Forces acting on the ship. Forces acting on the vessel

1. General concepts and definitions

Controllability - the ability of the vessel to move along a given trajectory, i.e. Hold the specified direction of movement or change it under the action of control devices.

The main managers on the vessel are the steering controls, the propulsion control tools, the means of active control.

Controllability combines two properties: Resistance to the course and turning .

Resistance to the course - This is the ability of the vessel to maintain the direction of rectilinear movement. Resistance to the course can be automatically when the vessel is able to hold on the course without work management (steering wheel), and operational when the deduction of the vessel on the specified course is carried out using the controls.

Tolding - the ability of the vessel to change the direction of movement and describe the trajectory of a given curvature.

Turning and stability on the course correspond to the main purpose of any means of management: turn the ship and ensure its movement in the constant direction. In addition, any control tool must ensure opposition to the influence of external power factors. In accordance with this, R.Ya. The penitz introduced the definition of such an important component of manageability, as obeditity.

Obedience - the ability of the vessel to overcome resistance to maneuvering at specified external influences. In the absence of external influence, its role can play their own instability.

Coma obedience introduced the concept sensitivityUnder which the vessel's ability is meant as soon as possible to respond to the control of the control means, in particular, to the steering wheel.

Screw rush. In order for the vessel to move at a certain speed, it is necessary to make a moving force to it, overcoming resistance to movement. The useful power required to overcome the resistance is determined by the formula: NP \u003d R V, where R is the resistance force; V is the speed of movement.

The driving force is created by a working screw, which, like every mechanism, spends part of the energy unproductive. The powerful rotation power is: Nz \u003d M n, where M is the moment of resistance to rotation of the screw; N - screw rotation frequency.

The ratio of useful power to spent is called a transmitted coefficient of the complex Housing-propulsion:

h \u003d RV / M N

The missing coefficient characterizes the need for the vessel in the energy required to maintain the specified speed of movement. The power of the power plant (effective power NE) the vessel should be more spent power to rotate the screw, since there are losses in the grip and gear:

Ne \u003d RV / H HT HP,

where HB, HP - the efficiency of the mercoperation and gearbox.

Since with a uniform rectilinear movement, the screw strength is equal to the resistance strength, the above formula can be used to approximate the screw thrust in the full course mode (VO):

RE \u003d NE H HB Hr / Vo,

where the missing coefficient is determined by the LAPP formula:

where L is the length of the vessel between the perpendiculars:

n- Rotation frequency, s -1.

The maximum rift of the screw is developing in the mooring mode - about 10% more of the screw thrust in the full stroke mode.

The screw strength when working on the reverse approximately 70-80% of the screw thrust in the full run mode.

Resistance to the movement of the vessel

Water has viscosity properties and weights that cause two types of resistance when the vessel moves: viscous and wave. The viscous resistance has two components: friction and forms.
The friction resistance depends on the area and the roughness of the moistened surface of the case. The form resistance depends on the case of the housing. Wave resistance It is associated with the formation of ship waves when interacting the hull of a moving vessel with its surrounding water.

To solve the practical problems, water resistance to the vessel takes a proportional square of speed:

R \u003d K V²,

where k is a coefficient of proportionality, depending on the sediment of the vessel and the degree of fracturing of the body.

As indicated in the previous section, the power of resistance in full speed can be calculated according to the following formula:

RO \u003d NE H HB HP / VO.

Intermediate resistance values \u200b\u200b(R) for any speed of the stroke are determined:

Inertia vessel and attached mass of water

Equality of the resistance forces of the medium by the movement of the vessel and the thrust of the screw determines the uniform progressive movement of the vessel. When changing the screw rotation frequency, this equality of forces is broken.
With an increase in thrust, the vessel speed increases, with a decrease - drops. Changing the speed takes place for a long time, until the inertia of the vessel and the force of the screw and the resistance is not equal again. The measure of inertia is mass. However, the inertia of the vessel moving in the aquatic environment depends not only on the mass of the vessel itself.

The vessel body involves the water particles adjacent to it, which is spent additional energy. As a result, to give the vessel some speed will need a longer operation of the power plant.
When braking, it is necessary to pay off not only the kinetic energy accumulated by the vessel, but also the energy of water particles involved in the movement. Such interaction of water particles with a case is similar to an increase in the mass of the vessel.
This additional mass (the attached mass of water) in transport vessels ranges from 5 to 10% of their displacement with the longitudinal movement of the vessel and about 80% of the displacement during the transverse movement.

2. Forces and moments acting on the vessel when it moves

When considering the movement of the vessel, a rectangular coordinate system of XYZ is used associated with the severity of the vessel. Positive direction of the axes: x - in the nose; Y - towards the right side; Z - down.

All forces acting on the ship are divided into three groups: driving, external and reactive.

The driving includes strengthCreated by means of management: screw strength, side power steering, forces created by means of active control.

The external forces include wind pressure forces, Unrest of the sea, flow.

The reactive includes forces arising from the movement of the vessel under the action of driving and external forces. They are divided by inertial - caused by the inertness of the vessel and the attached mass of water and arising only in the presence of accelerations. The direction of the inertial forces is always opposite to the active acceleration.

Neifferentic forces are caused by the viscosity of water and are hydrodynamic forces.

When analyzing the forces acting on the vessel, it is considered as a vertical wing of a symmetric profile relative to the diametrical plane (DP).

With reference to the vessel, the main properties of the wing are formulated as follows:

if the vessel moves straightly in the stream of water or air at some angle of attack, then in addition lob's forcesdirected opposite to movement, the lifting force arises, directed perpendicular to the incoming flow. As a result, the referring to these forces does not coincide with the direction of flow. The magnitude of the resultant forces is proportional to the angle of attack and the square of the speed of the increasing flow;

an application point of the equal force is shifted by the DP from the center of the Wing Square towards the flow. The magnitude of this displacement is the bigger than the sharp angle of attack. At the corners of the attack close to 90 degrees, the point of the application of the equal force coincides with center of sailiness (for the surface of the vessel) and the center of the side resistance (for the underwater part);

applied to the underwater part of the vessel case: an angle of attack is an angle of drift, and for the surface part - cows angle (ku) apparent wind;

the side resistance center usually coincides with the center of the severity of the vessel, And the position of the center of sailiness depends on the location of the add-ons.

In the absence of wind and the direct position of the steering wheel, the first differential equation of the vessel movement can be represented as:

where MX is the mass of the vessel, taking into account the attached mass of water.

Uniform movement: There are no accelerations, therefore the inertial force of MX DV / DT \u003d 0. The vessel acts two equal and oppositely directional forces: water resistance strength and screw thrust force.

For Change the screw strength the equality of the thrust of the screw and the resistance of the movement of the vessel is disturbed; This causes the appearance of inertial forces, acceleration appears and the ship begins to move accelerated or slow. Inertial forces are directed against acceleration, i.e. Prevent the change in the speed of movement.

With an increase in the force of thrust 3 forces act on the ship:screw thrust force - forward Resistance force- Back, inertia strength - back.

With a decrease in the force of thrust: traction force - forward; from salah resistance- back; inertia strength - forward

When maneuver stop:fromsalah resistance - back; inertia strength - forward;

With reverse:

a) before the ships stop: resistance force- back; the force of traction - back; Inertia strength - forward.

b) after stopping and starting the movement back: resistance force - Forward; the force of traction - back; Inertia strength - forward.

Note:forward - the direction to the nose of the vessel; Back - direction to the stern of the ship.

Forces acting on the vessel when turning

Turns of the vessel occur under the action of an overlooked steering wheel. If you hold it on board the steering wheel during a certain period of time, the vessel will make a movement called circulation. At the same time, the center of gravity of the vessel will describe the circulating curve, in shape close to the circle.
For the beginning of the circulation, the moment of the start of the steering wheel is taken. Circulation is characterized by linear and angular velocities, curvature radius and drift angle.
The circulation process is customary to divide for three periods: maneuverable is for the time of the wheelchair time; Evolutionary - begins from the moment the steering is completed and the circulation characteristics will take the established values; The established - starts from the moment the end of the second period and continues until the steering wheel remains in the overlap position.

The vessel's steering wheel is considered as a vertical wing of a symmetric profile.Therefore, at its smoker, lifting force arises - the side force of the RR RR.

We will apply two equal PRU to the center of severity and the oppositely directed forces of P "RU and R" "RU. These two forces are mutually compensated, i.e. do not affect the vessel body.

Then the following strengths and moments operate on the vessel:

the power of the windshield resistance of the steering wheel RRH - reduces the speed of the vessel;

the moment of the strength of the Rru R "" Ru - unfolds the ship towards the pilot steering wheel;

power r "ru - moves the center of gravity to the side, back turning.

Forces acting on the ship in the evolutionary period of circulation

The ship's turn under the action of the moment of the force of Rru R "" RU leads to the appearance of the corner of the drift. The vessel body begins to work as a wing. The lifting force appears - the hydrodynamic power of R. We applied the vessel to the CT two equal Ry and the oppositely directed forces R "Y R" "Y.

Then additionally to the forces and moments acting in the maneuverable circulation mode appear:

the power of the windshield resistance RX - even more reduces the speed of the vessel;

the moment of strength Ry R "Y - promotes turn; angular rotation speed increases;

the force R "" Y - compensates for the strength of P "RU and the trajectory is twisted towards the turn.

Forces acting in the established period of circulation

As soon as the vessel starts the movement along the curvilinear trajectory, the centrifugal power of RC appears. Each point in the length of the vessel describes a relatively common center about its trajectory.
At the same time, each point has its own drift angle, the values \u200b\u200bof which increase as it removes towards the stern. In accordance with the properties of the wing, the point of application of the hydrodynamic force R is shifting in the feed for the center of the severity of the vessel.

As a result:

the power of the RCCh - reduces the speed of the vessel;

the power of the RCU - prevents the change in the radius of circulation;

the moment created by the hydrodynamic power of RU is preventing an increase in the angular rotation rate;

all circulation parameters strive for their established values.

The geometrically circulation trajectory is characterized by:

The resolution IMO A.751 (18) "Interim standards of maneuverable qualities" for newly under construction vessels proposed values:

1) Direct offset (Advance) - no more than 4.5 ship lengths;

2) Tactical diameter (TACTICAL DIAMETER) - no more than 5 ship lengths.

Ship handling when following

When the vessel moves, the following strengths and moments act on the vessel on the vessel to the vessel (see Figure):

transverse power of the steering wheel;

the moment of the forces of the Rru and the Rru turns the vessel to the side, inversely reversed the steering wheel;

the hydrodynamic power of the RU forms a moment that prevents reversal;

a spindle water pumping on the steering wheel reduces the effective steering angle by a value equal to the drift corner and, therefore, the value of the side force of the steering force decreases.

The following factors determine the worse drive of the vessel in the rear compared to the front.

Forces and moments related to wind exposure

When considering the forces and moments associated with the impact of wind, the apparent wind speed is used.

In accordance with the property of the wing, the aerodynamic force A. appears when exposed to wind.

Enclosing aerodynamic force on the longitudinal and transverse components and applying two equal and the oppositely directed forces of AU and A "We obtain:

aH strength - increases the speed of the vessel;

the moment of forces AU and A "U - unfolds the ship on the right side;

power A "" y - causes lateral movement, which leads to the appearance of the drift angle A and the hydrodynamic power R;

the longitudinal component of the hydrodynamic force RX - reduces the speed of the vessel;

the moment of the Forces Ry R "" Y, acting in one direction with the moment of the forces of AU and A "y, even more unfolding the ship;

the strength r "y causes lateral movement opposite to move from power A" "

To hold the vessel on the course it is necessary to shift the steering wheel to some angle to create the moment of lateral power of the steering wheel of the RRU, which compensates for the moments of aero- and hydrodynamic forces.

A working propeller of the screw makes at the same time a translational movement at the vessel vessel V relative to unperturbed water and rotational motion with an angular velocity W \u003d 2p n. Each screw blade is seen as a separate wing.

When the water flow is inserted on the screw, the force is created on each blade, proportional to the square of the flow rate and the value of the angle of attack. Laying this force on two perpendicular directions to each other, we obtain: the force of thrust directed along the axis of rotation of the screw and the length of the windshield, acting in the plane of the screw disk along the tangent of the circle, which the points describe on the screw blades during its rotation.

Since the working screw is located behind the hull of the vessel, then when it moves, the water flow flows on the blade of the screw with unequal rates and at various angles. As a result, there is an inequality of thrust forces and windscreen resistance for each blade, which leads to the appearance, in addition to the thrust of the screw strength screw, affecting the manageability of the simulated ship.

The main reasons for the appearance of the lateral forces are:

associated flow of water, drought by the body when it moves;

water reaction to a working screw;

uneven sinking water jet from the working screw on the steering wheel or the vessel case.

Consider the influence of these reasons for the operation of the fixed screws (VFSH) and the adjustable (VRSH) step of the right rotation.

The influence of associated flow

In the upper part of the screw, the speed of the passing flow of water due to the shape of the body of the housing will be greater than in its lower part, which leads to an increase in the angle of the water flow attack on the upper blade. This can be shown by considering the movement of the blade element located on the R radius from the axis of rotation of the screw.

The blade element during the operation of the screw takes part in the rotational motion with a linear velocity equal to 2Pr ● n, and the progressive movement at the speed of the vessel V.

The actual speed of the progressive movement of the screw blades of the screw decreases by the value of the dv speed of the associated flow. As a result, the angle of attack increases to the value of AF, which leads to an increase in the forces of DPH and DRU.
Integrating the DRX and DRU along the length of the blade, we obtain the values \u200b\u200bof the thrust forces (P1) and the windscreen resistance (Q1) created by the screw blade in the upper position. These forces will be more P3 and Q3 forces created by a blade in the lower position. The inequality of the forces Q1 and Q3 causes the appearance of the lateral force DQ \u003d Q1 - Q3, which seeks to deploy the stern of the vessel to the left to the side of greater from the forces.

Screw water reaction

The work of the screw is influenced by the proximity of the water surface. As a result, air seats are observed to the blades in the upper half of the screw disk. At the same time, the upper blades are experiencing a smaller force of the water reaction than the lower. As a result, the side force of the water reaction occurs, which is always directed toward the rotation of the screw - in the case under consideration to the right.

When rotating the screw, the twisted flow of water flows on the pen in its lower and upper part at different angles of attack. At the bottom of the clutch, the attack is less than in the top.

As a result, the side force arises, which seeks to turn the stern to the right.

The overall effect of the screw: For most vessels with VFS and VRSH strength or mutually.

In this case, the passing stream is saved. However, in contrast to the above case, the passing stream reduces the angle of attack.

Therefore, the dpy frontal resistance force on each blade element is reduced. In the upper position, such a decrease is expressed stronger than in the bottom, because At the bottom of the speed of associated flow less. Therefore, the resulting windshield resistance blades for VFS will be directed to the left.

The absolute majority of ships of the LSH left rotation are. For VRSH When changing the mode of operation from the front to the reverse, the direction of rotation is saved, only the screw step changes: the left step screw becomes the right screw. Therefore, the resulting windshield strength of the blades as well as ships with the Right step will be directed to the left.

Screw water reaction

The side force of the reaction of water to the screw, as mentioned above, is always directed toward the rotation of the screw: and both for VFS and for VRSh - to the left.

A screw jet is thrown into the vessel's feed.

As a result, elevated hydrodynamic pressure and feed will be shifted: both for VFS and for VRSh - left.

The overall effect of the screw: feed goes left.

The vessel is moving back, the screw rotates back.

With the beginning of the movement of the vessel back, the passing stream disappears.

Screw water reaction: Left.

: left.

The overall effect of the screw: Feed goes left.

4. Effect of rowing screws on the controllability of the multi-aircraft vessel

Most modern passenger ships, icebreakers, as well as high tonnage high-speed vessels are equipped with two- or three-mall power plants. main feature Multi-ships compared to the simultaneous courts are their best handling.
Rowing screws in two-screw, as well as onboard screws in the three screw vessels are located symmetrically relative to the diametrical plane and have the opposite direction of rotation, usually the same name with the board. Consider the controllability of multi-ships on the example of a two-duty vessel.

With the simultaneous operation of the screws forward or backward, the lateral forces caused by the passing stream, the reaction of water to the screw and the jet from the screws that are embroiled on the steering wheel or the housing are mutually compensated, as the screws have the opposite direction of rotation. Therefore, there is no tendency to evade feed in one direction or another, as at the simultaneous vessel.

One screw is working forward, another stop.

Taking advantage of the well-known technique, attach two equal strengths of the RL screw thrust (in the picture the left side screw works) and the oppositely directed forces, we get:

strength p "" l causes the movement of the vessel forward;

the moment of the power of the RL and P "L turns the stern towards the working screw;

from the hydrodynamics it is known that the working screw accelerates the flow of water that flows around the feed of the feeds, and the hydrodynamic pressure from the operating screw is falling. Due to the pressure difference, the power of the RD is formed. Having attached to the CT vessel two equal RDs and the oppositely directed forces of P "D and R" "D, we get: - the moment of the power of the RD and R" "D pulls the stern towards the working screw; strength p" d - shifts the CT vessel towards the operating screw .

Thus, the movement of the two-venture vessel in question is approximately similar to the movement of the simulated vessel with an overlooking steering wheel.

One screw works back, another stop.

After conducting the previous partitioning and reasoning sections, it is possible to obtain a general conclusion that the vessel's feed shies towards the opposite of the screw-operated back. At the same time, it should be noted that the Power of the RD in the case under consideration is created due to the jet from the operating screw, which is thrown into the stern part of the case.

Ship turnout in place when operating screws savage

The two-screw vessel can unfold almost in place when the screws are boosted (one screw works the front, and the other reverse). The rotational frequency is selected in such a way that the strengths of the screws are the same in size.
The approximate equality of forces is achieved when on the machine running forward, give one step less than on the car operating back. For example: Small move forward - middle back.
The unfolding moment is created not only due to the location of the screws along different sides of the DP, but also due to the difference in water pressure in the stern bezor, created by oppositely directed jets from the screws.

The disadvantages of two-ventures should include low efficiency located in the Power Steering. Therefore, at low speeds, when the main part of the force arising on the steering wheel during its smoker is created by the jet of water, a screwdriver on the steering wheel, the main way of control is the maneuver machine.

Three-ventricular vessels Combine positive maneuverable qualities of single and two-screw vessels and have higher maneuverability including at low speeds. In front of the front, the average screw increases the efficiency of the steering wheel due to the screw stream. In the rear, the average screw provides progressive movement, and the reversals are carried out by the work of the onboard screws.

5. The main factors affecting the manageability of the vessel

Constructive factors.

The ratio of length to the width of the vessel (L / B).The greater this attitude, the worse the valid of the vessel, which is due to the relative increase in the forces of resistance to the lateral movement of the vessel. Therefore, wide and short vessels have better turnover than long and narrow.

The coefficient of total completeness (d). With increasing coefficient D, turning is improved, i.e. The fuller the vessel, the better his turning.

The design and location of the steering wheel.The structure of the steering wheel (its area and relative elongation) is little affected by improving the ship's turning. The location is significantly more influence. If the steering wheel is located in a screw stream, the speed of water flow into the steering wheel increases due to the additional flow rate caused by the screw stream, which ensures a significant improvement in the turning.

On duvunt ships, the steering wheel, located in the DP, has relatively low efficiency. If two steering fever are installed on such vessels for each of the screw, turning sharply increases.

Ship speed

The form of circulation, its main geometric characteristics (extension, direct displacement, reverse offset) depend on the initial velocity of the vessel. But the diameter of the steady circulation with the same corner of the steering wheel remains constant and does not depend on the initial speed.

Under the wind, the handling significantly depends on the velocity speed: the speed is less, the greater the effect of wind on handling.

Elements of landing vessel

Trim. The increase in the differential of the stern leads to a displacement of the center of the side resistance from the Middle in the direction of the stern, therefore the stability of the vessel is growing up to the course and its turning is worse.
On the other hand, the softener of the nose sharply impairs stability on the course - the vessel becomes rigging, which complicates maneuvering in cramped conditions. Therefore, the ship is trying to download it so that it has a small differential on the stern.

Bank. The ship's roll violates the symmetry of the hull flow. The area of \u200b\u200bthe immersed surface of the cheekbone of the lone board becomes more appropriate area of \u200b\u200bthe cheekbone of the raised side.

As a result, the ship seeks to appreciate the opposite roll, i.e. towards the smallest resistance.

Draft.The change in precipitation leads to a change in the side of the side resistance of the immersed part of the case and the area of \u200b\u200bsailiness. As a result, the resistance of the vessel is improved with the increase in precipitation and the turnover is worse, and with a decrease in precipitation - on the contrary.
In addition, the decrease in the sediment causes an increase in sailing area, which leads to a relative strengthening of the impact of wind on the controllability of the vessel.

Inertia-brake characteristics of the vessel

Forces and moments acting on the ship.

System of vessel motion equations in

Horizontal plane.

Maneuveracted vessel characteristics.

Requirements for the content of information about

Maneuverable characteristics of the vessel.

General about inertia-brake

The properties of the vessel.

7. Features of reversing various types

Driving vessels.

Braking vessel.

Ship as a control object.

The transport marine vessel makes movement on the border of two environments: water and air, while experiencing hydrodynamic and aerodynamic effects.

To achieve the specified motion parameters, the vessel must be controlled. In this sense the vessel is a managed system. Each the controlled system consists of three parts: control object, controls and control devices (automaton or man)

Control – this is such an organization of the process that ensures a certain purpose corresponding to the management task.

When swimming vessel in the open sea, the management task is In ensuring its transition from one point to another along a straight trajectory, holding the specified course and periodically adjusting it after obtaining observations. In this case the course is a managed coordinate, and the process of maintaining its constant value is the purpose of management.

The instantaneous value of a number of coordinates determines the state of the vessel in this moment. Such coordinates are: course, speed, drift angle, transverse displacement relative to the General Course and t.P. They are output coordinates. Unlike them, coordinates are the causes of the controlled movement are called input . it steering angle and Row Screw Rotation Rotation . When selecting the input coordinate values, the control device (stealless, sentient), are guided by the values \u200b\u200bof the output coordinates. Such a connection between the investigation and the cause is called feedback.

The considered managed system is closed, because It operates the control device (justifier). If the control device stops functioning, the system becomes open and the behavior of the control object (vessel) will be determined by the state in which the controls are fixed (the angle of the steering wheel, the frequency and the direction of rotation of the propeller).

In the discipline "Department of the Ship", the tasks of the management of the vessel are studied, the movement of which occurs in close proximity from obstacles, i.e. At distances comparable to the size of the control object itself, which eliminates the ability to consider it as a point (for example, as in the course "Navigation").

Forces and moments acting on the ship

All the forces acting on the ship are made to divide into three groups: driving, external and reactive.

To moving believe the forces created by the control facilities to give the ship linear and angular movement. These forces include: stopping the rowing screw, the side force of the steering wheel, the forces created by the means of active control (SAU), etc.

To external Believe the strength of the wind pressure, unrest of the sea, flow. These forces in most cases create interference when maneuvering.

To reactive include strength and moments resulting from the movement of the vessel. Jet forces depend on linear and angular velocities of the vessel. By nature, the reactive forces and moments are divided into inertial and non-air. Inertial forces and moments are caused by the inertness of the vessel and the associated mass of the fluid. These forces arise only when the presence of accelerations - linear, angular, centripetal. Inertial force is always directed towards opposite to acceleration. With a uniform straight movement of the vessel, the inertial forces do not occur.

Neifferent forces and their moments are due to the viscosity of the intake water, therefore, are hydrodynamic forces and moments. When considering manageability tasks, a mobile coordinate system with the beginning in its center of gravity is used. Positive direction of the axes: x - in the nose; Y - towards the right side; Z - down. The positive countdown of the corners is accepted clockwise, however, with reservations against the angle of the blasting, drift angle and the winding corner of the wind.

For the positive direction of the handling of the steering wheel, the handling of the circulation clockwise is accepted, i.e. The shock on the right side (the feather of the steering wheel unfolds at the same time counterclockwise).

For the positive angle of the drift, such in which the flow of water comes from the left side of the left side and, therefore, creates positive transverse hydrodynamic power on the housing of the vessel. Such angle of drift occurs on the right circulation of the vessel.

The general case of the vessel movement is described by the system of three differential equations: two equations of forces along the longitudinal x and transverse y axes and the correspondence equations around the vertical axis Z.

All forces acting on the ship are divided into three groups:

Driving;

External;

Jet.

TO moving Forces include the forces created by the controls: the screw, the side power of the steering force, the forces created by the means of active control.

TO external Forces include wind pressure forces, sea cleansing, flow pressure.

TO reactive Forces include forces arising from the vessel's movement under the action of driving and external forces. They are divided by inertial - caused by the inertness of the vessel and the attached mass of water and arising only in the presence of accelerations. The direction of the inertial forces is always opposite to the active acceleration. Noninerization Forces are caused by the viscosity of water and air and are hydrodynamic and aerodynamic forces.

Drive screw and resistance to the movement of the vessel.

In order for the vessel to move at a certain speed, it is necessary to make a moving force to it, overcoming resistance to movement. The useful power required to overcome the resistance is determined by the formula

where R is the power of resistance; V is the speed of movement.

The driving force is created by a working screw, which, like every mechanism, spends part of the energy unproductive.

The ratio of useful power to spent is called a passive coefficient of the complex case - a propulsion. The missing coefficient characterizes the need for the vessel in the energy required to maintain the specified speed of movement.

The maximum rush of the screw is developing in the mooring mode (in the case when the vessel stands on mooring, and its car was given a full front turn). This force is about 10% more of the screw thrust in the full course mode. The screw strength when working on the reverse for various vessels is approximately 70-80% of the screw thrust in the full stroke mode.

PITCHING.

Swing is called oscillatory movements that the ship performs near its equilibrium position.

Oscillations are called free(on quiet water), if they are committed by a vessel after the cessation of the forces that caused these oscillations (a flurry of the wind, a towing cable jerk). Due to the presence of resistance forces (air resistance, friction of water), free oscillations are gradually faded and stopped. Oscillations are called forcedif they are committed under the action of periodic disturbing forces (incident waves).

Pitch is characterized by the following parameters (Fig. 179):

amplitude θ- the greatest deviation from the equilibrium position;

wheel- the sum of two consecutive amplitudes;

period- the time of the commission of two full disclaims;

acceleration.

Pitch makes it difficult to operate machines, mechanisms and devices due to the impact of the emerging inertia, creates additional loads on the strong links of the vessel body, has a harmful physical impact on people.

Fig. 179.. Pitchparameters: θ 1 and θ 2 amplitudes; θ 1 + θ 2 scope.

Distinguish onboard, kille and vertical swing. For onboard swingoscillations are performed around the longitudinal axis passing through the center of severity of the vessel, keel- Around the transverse. The onboard pitching at a small period and large amplitudes becomes a pusty, which is dangerous for mechanisms and is seriously transferred by people.

The period of free vibrations of the vessel on quiet water can be determined by the formula T \u003d C (b / √h,where IN- width of the vessel, m; h.- transverse meticenter height, m; from- A coefficient equal to 0.78 - 0.81 cargo ships.

From the formula it is clear that the pitching period decreases with an increase in metuclear height. When designing the vessel, they strive to achieve sufficient stability with moderate smoothness of the pitch. When swimming on the excitement, the vessel must know the period of own oscillations of the vessel and the wave period (the time between the junction on the vessel of two adjacent ridges). If the period of the vessel's own oscillations is either close to the wave period, then the phenomenon of the resonance occurs, which can lead to the tipping of the vessel.

With a killeva ride, it is possible either pouring a deck, either when the nasal is barefall or the feed of their blows about water (Slema). In addition, the acceleration arising during a keel ridge is much larger than when onboard. This circumstance must be taken into account when choosing mechanisms installed in the nose or in the stern.

Vertical pitchcaused by the change in the power of maintenance during the passage of the wave under the vessel. The period of vertical pitch is equal to the wave period.

To prevent the undesirable consequences of the action of pitching, shipbuilders are used by means of contributing, if not complete stopping pitching, then at least the death of its disclaims. Especially acute is this problem for passenger ships.

To die the killeep and pouring a deck with water, a number of modern vessels make a significant lifting of the deck in the nose and in the stern (saddle), the collapse of the nasal spangouts increases, vessels with Baku and Utah. At the same time, water visors are installed in the tank.

To die on board pitching, use passive unmanaged or active managers of pitching.

To passive sedatives belong to cyli kili,presenting steel plates installed for 30 to 50% of the vessel length in the region of cheekbones along the water current line (Fig. 180). They are simple on the device, reduce the amplitude of pitching by 15-20%, but have a significant additional water resistance to the movement of the vessel, reducing the speed of the course by 2-3%.

Fig. 181. Side passive tanks and the position of liquid in them when rolling the vessel in a resonance with a wave.

These tanks are effective during pitching modes with a large period. In all other cases, they do not die, but even increase its amplitude.

IN active tanks(Fig. 182) Water is pumped by special pumps. However, the installation of the pump and the automatic device controlling the pump work significantly complicates and increases the design.

Forces and moments acting on the ship. When analyzing the forces acting on the vessel, it is considered as a vertical wing of a symmetric profile relative to the diametrical plane (DP). With reference to the vessel, the main properties of the wing are formulated as follows rectilineously in the flow of water or air at some attack angle, then in addition to the force if the vessel is manifold: the frontal resistance is directed oppositely by the movement, the lifting force appears to be perpendicular to the perpendicular flow. As a result, the referring to these forces does not coincide with the direction of flow. The magnitude of the resultant forces is proportional to the angle of attack and the square of the speed of the increasing flow; An application point of the equal force is shifted by the DP from the center of the Wing Square towards the flow. The magnitude of this displacement is the greater the sharper an angle of attack. At the corners of the attack close to 90 degrees, the point of the application of the equal force coincides with the center of sailbo (for the surface of the vessel) and the side of the side resistance (for the underwater part); With reference to the underwater part of the vessel case: the angle of attack is an angle of drift, and for the surface part of the course angle (ku) of the apparent wind; The lateral resistance center usually coincides with the center of the severity of the vessel, and the position of the sail service center depends on the location of the add-ons.

Forces and moments acting on the ship. Fig. 1. 3. Impact of external forces on the hull of the vessel

Maneuverability of the vessel 1. 1. General concepts and definitions of maneuvering - a change in the direction of movement of the vessel and its velocity with the help of a steering wheel, drivers, sweeping devices in order to ensure the safety of navigation or solving operational tasks (mooring, armature, narrow passage, etc. ). Maneuverability is determined by such qualities of the vessel as speed, hurdity, controllability, resistance to the course and turning, as well as the inertial characteristics of the vessel. Ship maneuverability is not constant. Its change occurs under the influence of various factors (loading, roll, differential, wind, etc.), which should be taken into account for the shipholders when managing the vessel. Under the hosfendance it is understood as the ability of the vessel to overcome the resistance of the environment and move at the required speed with the lowest capacity of the main machines. The speed of the vessel is one of the most important characteristics of the maneuverable elements of the vessel. The speed of the vessel is considered the speed with which it moves relative to water. Controllability - the ability of the vessel to move according to a given trajectory, i.e., hold the defined direction of movement or change it under the action of control devices. The main managers on the vessel are the steering controls, the propulsion control tools, the means of active control. Controllability combines two properties: resistance to the course and turning. Resistance to the course is the ability of the vessel to maintain the direction of the straight movement. Tolding - the ability of the vessel to change the direction of movement and describe the trajectory of a given curvature. Resistance to the course and turning are in contradiction with each other. The more stable straight movement of the vessel, the harder it is to turn it, that is, turning turns. But on the other hand, improving the ship's turning makes it difficult to move in a constant direction, in this case the deduction of the vessel on the course is associated with the intense work of the steering or auto-power and frequent handling of the steering wheel. When designing vessels, they seek to find the optimal combination of these properties. The ship's controllability is mainly determined by the mutual arrangement of three points: the center of gravity (CT), the center of the application of all the forces of resistance to the movement and the center of the application of the driving force (Fig. 1. 4). Fig. 1. 4. Location of the vessel's rotation center

Ship maneuverability If the center of gravity, at a certain state of loading, the vessel remains fixed, the center of the resistance forces application does not have a permanent location. Depending on the movement of the vessel, the total vector of the forces of the resistance of the aqueous and air media changes, and the point of its application to the vessel is usually moved along the diametrical plane. When turning, the vessel unfolds around the vertical axis (center of rotation - P) passing through the center of resistance forces. If the CT is located in front of the center of resistance forces, the ship is steadily on the course and vice versa, if the CT is located behind the center of the resistance forces, the ship is unstable in the course and more arranged. The location of the driving force application center depends on the mode of operation of the drivers, the position of the steering wheel, the impact of wind, flow, etc. Depending on the location of the specified three points when the vessel is moving, concomitant phenomena may occur: roll, differential, transverse displacement. As a result of the effects of flowing waters and wind masses on the body, screw and steering wheel, even with a calm sea and weak wind, the vessel does not remain constantly on the specified course, but deviates from it. The deviation of the vessel from the course with the direct position of the steering wheel is called ulice. The amplitude of the yaw of the vessel in quiet weather is small. Therefore, it takes a slight overhang of the steering wheel to the right or left. With strong wind and excitement, the stability of the vessel on the course is significantly worse. On the shyness of the ship big influence The arrangement of the superstructure. On those courts where the superstructures on the stern increase increase, since almost always the feed goes "under the wind", and the nose is "on the wind". If the superstructure is in the nose, the ship evades "from the wind". Evasion of the vessel under the wind is called respect. This property is just as dyedness, is a disadvantage of the vessel, it always has to take into account when carrying out various maneuvers, especially in cramped conditions.

Circulation circulation is called the trajectory described by the center of the severity of the vessel, when moving with rejected steering wheel. Circulation is characterized by linear and angular velocities, curvature radius and drift angle. The angle between the vessel linear velocity vector and the diametral plane is called the drift angle (β). These characteristics do not remain constant throughout the maneuver. The circulation is taken to break through three periods: maneuverable, evolutionary and established. The maneuverable period is the period during which the steering wheel is operated on a certain angle. Since the start of the steering wheel, the vessel begins to drift to the side opposite to the charging of the steering wheel, and at the same time begins to turn around in the direction of the steering wheel. During this period, the trajectory movement of the center of gravity of the vessel from the straight line turns into a curvilinear, the speed of movement of the vessel is dropped. The evolution period is a period starting since the end of the steering wheel and continuing until the end of the end of the drift corner, linear and angular velocities. This period is characterized by a further decrease in speed (up to 30 - 50%), a change in the roll to the outerboard up to 100 and the sharp removal of the feed on the outer side. The period established circulation is a period beginning at the end of the evolutionary, characterized by the equilibrium of the forces acting on the ship: the screw stop, the hydrodynamic forces on the steering wheel and the case, centrifugal force. The trajectory of the center of gravity (CT) of the vessel turns into a trajectory of the correct circumference or close to it. The geometrically circulation trajectory is characterized by the following elements: DO - the diameter of the established circulation - the distance between the diametrous planes of the vessel on two consecutive courses, differing in 180 * with the steady movement; DC is the tactical circulation diameter - the distance between the positions of the diametral plane (DP) of the vessel before the start of rotation and at the time of the course of 180 *; L 1 - extensive - the distance between the provisions of the vessel of the vessel before entering the circulation to the circulation point in which the ship's course varies by 90 *; L 2 - a direct shift - the distance from the initial position of the vessel of the vessel to its position after the rotation by 90 *, measured by normal to the initial direction of the ship's movement; L 3 - reverse offset - the largest shift of the CT vessel as a result of a drift in the direction, the opposite side of the steering wheelchair (the opposite displacement usually does not exceed the width of the vessel B, and on some ships is missing at all); TC - Circulation period - Time of rotation of the vessel by 360 *.

Influence of various factors on the vessel turning. Constructive factors. The ratio of length to the width of the vessel (L / B). The more this attitude, the worse the valid of the vessel. This is due to the relative increase in the resistance forces by the lateral movement of the vessel. Therefore, wide and short vessels have better turnover than long and narrow. The ratio of the sediment to the length of the vessel (T / L). With an increase in the attitude, the vessel turning is somewhat deteriorating somewhat, that is, the ship in full cargo will have the worst turnover than in Ballast. The ratio of the width to the sediment (in / t). The growth of this relationship leads to a significant improvement in turning. Courts are wide and petty more turning than ships with large precipitation and narrow. The coefficient of total completeness (δ). With an increase in the coefficient Δ, the turnover is improved, i.e., the larger the vessel, the better its turning. Form of the stern (the area of \u200b\u200bthe feed dadwood and the fullness of the stern). Especially a strong influence on the revival of the vessel is the area of \u200b\u200bFeed Daidwood. Therefore, even a small increase in it leads to a sharp increase in the diameter of circulation at all corners of the steering wheel. An increase in the completeness of the feed helps to improve the turning of the vessel. The shape of the nasal formations of the vessel is significantly less on the validation than the shape of the stern. As a rule, the effect of the nasal form is manifested only in the presence of a significant nasal podzer (for example, in icebreakers), which causes some increase in the diameter of the vessel circulation. Sizes and steering configuration. Increased steering area, as well as other changes in the shape of the steering wheel, has a dual impact on turning. Practical calculations show that an increase in the area of \u200b\u200bthe steering wheel leads to a decrease in the diameter of the circulation at large corners of the steering wheel and to an increase in it at low angle angles. Placing the steering wheel relative to the screws significantly affects the valid of the vessel. The arrangement of the steering wheel in the screw stream due to an increase in the speed of its flow contributes to the growth of the steering efficiency and is reflected on the vessel turning the same as an increase in the steering area. The effect of the screw stream affects the fiction. 1. 17. The influence of the wheelchair angle on the vessel's turnover: more than a large steering area enters the stream A - the drive angle to 45 *, b - the drive angle of more than 45 * from the screw. When the steering wheel is driven by more than 45 *, the effectiveness of its action on the vessel turning sharply decreases (Fig. 1. 17).

Influence of various factors on the vessel turning speed of the vessel. The starting speed of the V, with which the vessel performs a straight vessel movement to the steering wheel, affects the values \u200b\u200bof the extensive, direct and reverse displacements. Under the wind, the handling significantly depends on the velocity speed: the speed is less, the greater the effect of wind on handling. The sea's excitement contributes to the shyfulness of the vessel. The corners of the armor depend on the rate angle of the wave and increase as the excitement of the sea increases. Particularly unfavorable swimming will be in the presence of wind waves and zybi from course angles 120 ° - 180 ° at vessel velocity close to the speed of the wave propagation. In this case, the amplitude of the decussion can be up to 30-50 °, and the steering wheel of the steering wheel becomes ineffective. Elements of planting vessels Different. The increase in the differential of the stern improves the stability of the vessel in the course and worsens its turn. On the other hand, the softener of the nose sharply impairs stability on the course - the vessel becomes rigging, which complicates maneuvering in cramped conditions. Therefore, the ship is trying to download it so that it has a small differential on the stern. The ship's roll violates the symmetry of the hull flow. The area of \u200b\u200bthe immersed surface of the cheekbone of the lone board becomes more appropriate area of \u200b\u200bthe cheekbone of the raised side. As a result, the vessel seeks to evade the opposite car, that is, towards the least resistance.

Used Books. 1. 2. 3. Snopkov V. I. Department of Judgment. / V.I. Snopkov - St. Petersburg. : ANO NPO Professional, 2004. -536 with Charlay G. N. Maritime Judgment Management. Charlai G. N. Vladivostok. : Mor. State University, 2009. -503 s. Likhachev A. V. Office of the vessel: a textbook for maritime universities. / Likhachev A. V. SPb. : Polytechnic University Publishing, 2004. 504 p. Prepared by Associate Professor of the Department of Us and BZK at the Sea of \u200b\u200bHGMA K. D. P., K. T. N. Tovostokorny O. N.

All the forces acting on the ship, according to the currently adopted classification, are divided into three groups: driving, external and reactive.

The driving force is the forces created by the means of management in order to give the vessel of the required linear and angular movement. Such forces include the propeller, the side power of the steering wheel, the forces created by the SAU, and so on.

The external is the strength of the pressure of the wind, the unrest of the sea, the flow. These forces caused by external sources of energy, in most cases create interference when maneuvering.

The reactive includes strengths and moments resulting from the movement of the vessel under the action of driving and external forces. Jet forces depend on linear and angular velocities.

By nature, reactive forces and moments are divided into inertial and non-air.

Inertial forces and moments are caused by the inertness of the vessel and the associated mass of the fluid. These forces arise only in the presence of accelerations - linear, corner, centripetal.

The inertial force is always directed towards the opposite acceleration. With a uniform straight movement of the vessel, the inertial forces do not occur.

Neifferent forces and their moments are due to the viscosity of the intake water, therefore, are hydrodynamic forces and moments. When considering manageability tasks, usually, as already noted, a movable coordinate system with the beginning in C is used. T. (TG) Positive axle direction: X.- into the nose; Y- towards the right side; Z - down. The positive countdown of the corners is accepted clockwise, however, with reservations with respect to the angle of the blasting, the angle of drift and the winding corner of the wind.

For the positive direction of the handling of the steering wheel, anchorage is taken, causing circulation clockwise, i.e. the shock to the right side (the feather of the steering wheel is unfolded counterclockwise).

For a positive drift angle, such in which the flow of water rolls on the side of the left side and, therefore, creates positive transverse hydrodynamic power on the housing. Such angle of drift occurs on the right circulation of the vessel.

The total case of the vessel motion is described by the system of three differential equations of movement: two equations of forces - by longitudinal X.and transverse Y.axes and equations of moments around the vertical axis Z.

This system in a somewhat simplified version has the form:

where m is the mass of the vessel

λ 11 - attached masses when moving along the X axis;

λ 22 - attached masses when driving along the Y axis;

V x - ship speed projection on x axis;

V y - the projection of the vessel speed on the Y axis;

ω - the corner speed of the vessel;

J - the moment of the inertia of the vessel relative to the z axis;

R x is a longitudinal hydrodynamic force on the housing;

R y is a transverse hydrodynamic force on the case;

P E - useful strength of the screw;

P px - longitudinal power of water pressure on the steering wheel;

P PY - transverse power of the steering force;

A X - longitudinal aerodynamic force;

A y - transverse aerodynamic force;

M R is the moment of hydrodynamic power on the case;

M a - moment of aerodynamic force;

M P is the moment of the transverse power of the steering wheel.

The first equation of the system characterizes the movement of the vessel along the "X" axis during acceleration and braking, so its solution allows you to evaluate the inertia-brake characteristics of the vessel. The second equation describes the patterns of transverse shift of the vessel. The third equation characterizing the angular movement is used in evaluating the manageability of ships. From this system, it can be seen that with a uniform and straightforward movement of the vessel, the left parts of the equations will be zero, and the transverse movement will not be. Based on this, the system of equations will take the form:

P e \u003d r x + a x + p px

P px p e a x r x

Fig.5.5. Forces acting on the vessel with a straight line movement.

5.4 Forces arising from the operation of the screw.

Hydromechanical interaction system Case - screw - the steering wheel is very difficult. The propulsion operating close to the vessel case significantly changes its speed field, which leads to a change in the hydrodynamic forces acting on the body. In turn, the flow of water coming to the screw receives perturbations from the housing of the moving ship. The essential effect of the screw also has a steering wheel on it. As a result of the interaction of the system, the corps - screw - steering wheel. There is a number of lateral forces that need to be constantly taken into account and rationally use when managing the shy maneuvers.

Power of associated flow.

Water-moving housing causes a backway stream, directed towards the movement of the vessel. The reasons for its appearance are the friction of the boundary layers of water about the hull of the vessel and the desire of mass of water to fill the volume displaced by the case. Between the speed of associated flow at the location of the screw V P.andship speed V.there is a relationship V P.\u003d V (1-ω), where ω is the coefficient of associated flow. Its values \u200b\u200bfor various vessels may vary from 0.10 to 1.00. Thus, the effect of the body on the screw is reduced to a decrease in the speed of the screw flowing.

Fig.5.6. Power of associated flow

It is experimentally established that in the upper half of the screw disk, the speed of the passing stream is greater than in the bottom. The non-uniformity field of the rapid flow rates in the screw disk for one turn causes a change in the angle of attack and, according to the strength of the stop and the moment on the blades passing the upper and lower position. So, the blade in the upper position will have a larger angle of attack and, accordingly, more resistance to rotation than the blade located in the lower position. As a result, the side force arises, which on the front steady move (the shield of the right rotation) will shift the feed of the vessel left.

Power of associated flow b it manifests itself to the greatest extent on the front steady go, causing evasion of the vessel's feed to the side, reverse rotation of the screw.

The power of the reaction.

The blades of the rowing screw, passing the upper position, are significantly closer to the surface of the water than the blades passing the lower position. As a result, this is an air suction to the upper water layers , camefully changes the power characteristics of the blade (emphasis and moment).

The influence of the proximity of the surface of the water is most significantly manifested with a small blowing of the screw (in the transport plants following in the ballast, the blade in the upper position is generally out of the water), in the period of unsteady movement (cottage of the stroke with the "stop"), during reverse. The difference between the stop and the moment on the upper and lower blasts, leads to the formation of the side of the reaction D.On the steady move and with an increase in the blowing of the screw, the reaction force action decreases sharply.

Fig.5.6. Reaction force D.

In the 1st sector, the blade, moving from position 1 to position 2, meets the resistance of water, the power of the reaction will be directed first to rightly (power d 1, and then upward (power d 2); the latter on the diametricness of the vessel does not affect, but gives vibration stern.

In the 2nd sector, the blade, moving out positions 2 in position 3, meets the resistance of the water, the power of the reaction of which is first at the bottom up (power d 2), and then the blades will overcome the power of the reaction sufficiently dense water layers (power d 3) directed from left to right and much greater than power D. 1 . Consequently, the vessel's feed will deviate to the right, and the nose is left.

, meets water resistance, the power of the reaction of which will be directed at the beginning left of the right (power d 3), and then the blade will overcome the reaction force D. 4 , directed from top to bottom. On the diametral plane of the vessel, this force does not affect, but gives vibration of the stern.

in position 1, the resistance of water meets, the power of the reaction is directed at first from top to bottom (force D. 4 ), and then the blade will overcome the reaction force of less dense layers of water (power d 1), directed to the right left, significantly less than power d 3. Consequently, the vessel's feed will deviate to the right, and the nose is left.

Power reaction D.it manifests itself to the greatest extent during the period of unsteady movement, causing evasion of the stern towards the rotation of the screw.

Power of a thrown jet.

The rowing screw during rotation twists the mass of water adjacent to the blades and discard them, forming a powerful spiral stream. When driving a vessel, this flow affects the steering wheel located behind the screw . When moving with reverse, the flow affects the forage of the vessel. A spiral stream formed by a screw can be represented in axial (axial) and tangential (tangential) components. The axial component, affecting the steering wheel located behind the screw, significantly increases its efficiency and does not cause any lateral forces. When the vessel moves, the axial component, affecting symmetric feeds, also does not cause any lateral forces.

The tangential component on the front turns on the feather of the steering wheel in the left upper and right lower half.

Due to the asymmetricality of the distribution of the associated flow by sediment, the vessel, and therefore caused by the circumferential velocities in the stream flowing onto the steering wheel, the effects of the tangential component on the right lower half of the steering wheel will be greater than on the left upper. As a result, the lateral power of a pounced jet S.

Fig.5.7. Action of power S.

In the 1st sector, the blade, moving from position 1 to position 2, discards the water layers away from the vessel, and no strength of the jet sink is formed.

In the 2nd sector, the blade, moving from position 2 to position 3, pits the water layers to the lower surface of the steering wheel, where the water density is much larger ... The steering wheel should have a desire to be left left, but since it is installed in the diametral plane of the vessel, the power of the ship The jet rushes to the entire feed of the vessel and takes the feed of the vessel to the left, and therefore the nose goes to the right. Denote this strength through FROM 1 .

In the 3rd sector, the blade, moving from position 3 to position 4 , it will throw away the layers of water from the vessel, therefore, there will be no strength of the jet patch.

In the 4th sector, the blade, moving from position 4 in position 1, the layers of water pounces again, but on the other hand, rather than in the 2nd sector, and on the top of the steering wheel. Denote this streaming force FROM 2 . The effect of this force will be less than the effect of the jet damp force FROM 1 in the 2nd sector, due to the smaller water density. Hence the conclusion: the screw of the right rotation on the steady forehead, acting on the steering wheel, rejects the stern of the vessel to the left, and the nose is right

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