A real-time energy efficiency assessment method for wind-assisted ships

Abstract

A real-time energy efficiency assessment method for a wind-assisted ship. The present invention takes into account the coupling effect among the ship, the propeller, and the rudder, and analyzes the three-degree-of-freedom motion of "surge - sway - yaw" in the horizontal plane of the target wind-assisted ship. Taking the propeller thrust of the target wind-assisted ship under the action of the wind-assisted device as the input, the main engine power after the change of the propeller load of the target wind-assisted ship is calculated. Further, an oil consumption and energy efficiency benefit model is established to calculate the main engine power and oil consumption of the target wind-assisted ship with and without the wind-assisted device under the same ship speed. The present invention solves the matching problem among multiple mechanical models in the process of the energy efficiency assessment of the wind-assisted ship, systematically establishes an energy efficiency analysis and assessment method for the wind-assisted ship, and based on the present invention, the real-time energy efficiency analysis and prediction of the target wind-assisted ship can be quickly realized, which can provide reliable data support for the calculation of the comprehensive economic benefits of the wind-assisted device and the wind-assisted ship.

Description

Technical Field

[0001] The present invention belongs to the field of construction and design of sailboats, and particularly relates to a method for real-time evaluation of the energy efficiency of a wind-assisted ship. Background Art

[0002] With the development of the global economy, the overall global energy demand shows a growth trend, which will bring more severe environmental problems. The international community has put forward gradually stricter environmental protection requirements for all industries. As one of the main bodies of world energy consumption, the shipping industry's environmental pollution has attracted great attention from the international community. With the increasingly strict environmental protection requirements, the shipping industry urgently needs to adopt various innovative energy-saving and emission-reduction technologies to address global environmental problems.

[0003] The wind-assisted device is a new breakthrough in the shipping industry's innovative energy-saving and emission-reduction technologies for ships and has been widely recognized by the industry. When a wind-assisted ship equipped with a wind-assisted device sails with its sails up, the wind acts on the assisting device, which can provide auxiliary thrust for the ship to a certain extent, thereby saving fuel consumption, reducing emissions, bringing good economic benefits to ship operation, and at the same time helping to ensure the energy security and long-term flexibility of ship operation in an unstable market.

[0004] Real-time evaluation of the energy-saving effect of a wind-assisted ship is an important guarantee for making a realistic estimate of the comprehensive economic benefits of the wind-assisted device. Overestimating or underestimating the energy-saving effect of the wind-assisted device will lead to incorrect operation guidance and decisions for the wind-assisted ship. At the same time, the real-time calculation of the energy-saving effect of a wind-assisted ship needs to combine the meteorological environment information during the navigation of the wind-assisted ship and the energy efficiency information of the ship itself. There is currently no effective solution for how to apply reasonable calculation strategies and evaluation methods to use the meteorological data and energy efficiency information during the navigation of the wind-assisted ship as calculation inputs to comprehensively and objectively reflect the energy-saving situation of the wind-assisted device. Summary of the Invention

[0005] To solve the above problems, the present invention provides a method for real-time evaluation of the energy efficiency of a wind-assisted ship, aiming to achieve the purpose of real-time monitoring of the energy-saving effect of the ship's assisting device. The technical solution adopted is as follows:

[0006] A method for real-time evaluation of the energy efficiency of a wind-assisted ship,

[0007] S1: Establish a ship motion coordinate system, define the 0 rib position of the ship as the origin of the x-axis, and the positive direction of the x-axis is from the 0 rib position of the ship to the bow; define the midship as the origin of the y-axis, and the positive direction of the y-axis is from the midship to the port side of the ship.

[0008] β is the relative wind direction angle. The wind coming from the bow direction is defined as the 0° relative wind direction angle, increasing in the clockwise direction. The value range of the relative wind direction angle is 0° to 360°. During the ship's movement, the relative wind direction angle β is monitored in real time.

[0009] S2: Through the sail force model and the relative wind direction angle β monitored in real time, the sail boost force X sail and the lateral force Y sail ,

[0010]

[0011] where, is the air density,

[0012] v is the wind speed encountered by the target wind-powered ship,

[0013] A is the sail area,

[0014] C x,β is the longitudinal force coefficient of the target wind-powered device,

[0015] C Y,β is the lateral force coefficient of the target wind-powered device;

[0016] The relationship between the resistance X ship along the ship length direction of the target wind-powered ship and the yaw angle θ, and the yaw moment M hull , [[ID=3*]]

[0017] X ship = R Ts +ΔR

[0018]

[0019] where: R Ts is the hull resistance of the target wind-powered ship in the non-yaw (i.e., straight-ahead) state,

[0020] ΔR is the resistance increment when the yaw angle is θ,

[0021] d is the mean draft,

[0022] L PP is the length between perpendiculars of the target wind-powered ship,

[0023] λ is the aspect ratio of the wind-powered ship, λ = 2d / L PP ,

[0024] τ′=(T a -T f ) / d,

[0025]

[0026] The longitudinal component X of the rudder hydrodynamic force is obtained from the rudder hydrodynamic model rudder and the lateral component Y of the rudder hydrodynamic force rudder ;

[0027]

[0028]

[0029] where: F N is the normal pressure of the rudder,

[0030] t R is the thrust deduction coefficient of the rudder,

[0031] δ is the rudder angle,

[0032] C b is the block coefficient,

[0033] a H is the correction factor of the lateral force induced by steering on the hull,

[0034] A R is the area of the rudder,

[0035] f α is the slope of the lift coefficient of the rudder when the angle between the oncoming flow velocity and the rudder is 0,

[0036] U R is the longitudinal effective oncoming flow velocity of the rudder,

[0037] α R is the effective oncoming flow angle of attack of the rudder;

[0038] Establish a target wind-assisted ship motion-force model:

[0039]

[0040] And the propulsive force X of the wind force along the ship length direction sail and the lateral force Y of the wind force along the ship width direction sail and the longitudinal component X of the rudder hydrodynamic force rudder and the lateral component Y of the rudder hydrodynamic force rudder and the resistance X along the ship length direction suffered by the target wind-assisted ship navigation ship and the yaw angle θ caused by the target wind-assisted ship, and the lateral resistance Y suffered by the target wind-assisted ship under the yaw angle θ ship and the yaw moment M hull are substituted into the motion-force model.

[0041] where, L S is the longitudinal distance from the installation position of the target wind-assisted device to the center of gravity of the target wind-assisted ship,

[0042] L R is the longitudinal distance from the target wind-assisted ship's rudder stock to the center of gravity.

[0043] S3: Through the propeller thrust X propeller Obtain the fuel consumption SFC of the target wind-assisted ship in the current state.

[0044] For the above real-time energy efficiency evaluation method of a wind-assisted ship, further, the target wind-assisted ship is provided with a wind condition sensor, and the wind condition sensor includes a wind direction sensor and a wind speed sensor, and the wind direction sensor and the wind speed sensor are signal-connected to the sail turning power device.

[0045] For the above real-time energy efficiency evaluation method of a wind-assisted ship, further, the wind-assisted ship is a ship equipped with sails.

[0046] For the above real-time energy efficiency evaluation method of a wind-assisted ship, further, regard the target wind-assisted ship and the sails as rigid bodies and ignore the elastic deformation. Consider the coupling effect between the ship, the propeller and the rudder, and analyze the three-degree-of-freedom motion of "surge - sway - yaw" of the target wind-assisted ship in the horizontal plane.

[0047] The present invention solves the matching problem between multiple mechanical models in the process of evaluating the operating energy efficiency of a wind-assisted ship, systematically establishes an energy efficiency analysis and evaluation method for a wind-assisted ship, and based on the present invention, it can quickly realize real-time energy efficiency analysis and prediction of the target wind-assisted ship, and can provide reliable data support for calculating the comprehensive economic benefits of the wind-assisted device and the wind-assisted ship. Brief Description of the Drawings

[0048] Figure 1 is a schematic diagram of a wind-assisted ship;

[0049] Figure 2 are the motion coordinates of the target wind-assisted ship and the relative wind action direction;

[0050] Figure 3 is a schematic diagram of the forces acting on the target wind-assisted ship;

[0051] Figure 4 is a schematic diagram of the longitudinal force coefficient of the target wind-assisted device changing with the relative wind direction angle;

[0052] Figure 5 is a schematic diagram of the lateral force coefficient of the target wind-assisted device changing with the relative wind direction angle. Detailed Embodiments

[0053] As Figure 1As shown, an energy efficiency real-time evaluation method for a wind-assisted ship targets a ship equipped with sails. The target wind-assisted device is the sail, and the main parameters of the target wind-assisted ship include:

[0054] The length between perpendiculars LPP, molded breadth B, forward draft Tf, aft draft Ta, ship speed Vs, block coefficient Cb, longitudinal position of the center of gravity LCG, ship hydrostatic information, and calm water resistance information applied in establishing the hull hydrodynamic model in step S2, and the rudder area AR, rudder angle δ, rudder aspect ratio λR, and rudder installation position applied in establishing the rudder force model.

[0055] The ship speed-power information, open water information of the propeller, and propeller diameter D applied in establishing the main engine power and fuel consumption model in step S3.

[0056] The main parameters of the target wind-assisted device include:

[0057] The sail area A, longitudinal force coefficient Cx,β, lateral force coefficient CY,β, and installation position applied in calculating the sail boosting force and lateral force in step S2.

[0058] The target wind-assisted ship is equipped with a wind condition sensor, which includes a wind direction sensor and a wind speed sensor, and is carried on the target wind-assisted ship to measure the relative wind direction and relative wind speed. The controller issues commands to the sail turning power source according to the wind condition signal for sail turning control to obtain the maximum boosting force of the target wind-assisted device under the current wind condition.

[0059] The specific operation steps are as follows:

[0060] S1: Establish the motion coordinates of the target wind-assisted ship and the coordinate system of the action direction of the relative wind (encountered wind).

[0061] As Figure 2 shown, define the 0 rib position of the ship as the origin of the x-axis, and the direction from the 0 rib position of the ship to the bow as the positive direction of the x-axis; define the midship as the origin of the y-axis, and the direction from the midship to the port side of the ship as the positive direction of the y-axis. β is the relative wind direction angle of the target wind-assisted ship. Define the wind coming from the bow direction as the 0° relative wind direction angle, increasing clockwise, and the relative wind direction angle ranges from 0° to 360°.

[0062] Thus, the establishment of the motion coordinates of the target wind-assisted ship and the coordinate system of the action direction of the relative wind (encountered wind) is completed, and the conditions for establishing the planar motion model of the target wind-assisted ship are available.

[0063] S2: Establish the planar motion model of the target wind-assisted ship. Both the hull and the sails are regarded as rigid bodies, ignoring elastic deformation, and the mutual effects between the hull, the propeller, and the rudder are treated as static water. Analyze the three-degree-of-freedom motion of "surge-sway-yaw" in the horizontal plane of the target wind-assisted ship.

[0064] After the target wind power boosting device generates the boosting force, if the target wind power boosted ship continues to maintain the original speed, the rotational speed and thrust of its propeller will decrease to a certain extent. At the same time, under the action of the lateral force, the target wind power boosted ship will have lateral offset and heading change. Therefore, it is necessary to use steering to maintain the course stability. Under the combined action of the longitudinal force, lateral force, rudder force, propeller thrust and hull resistance of the target wind power boosted ship, a force and moment balance state will ultimately be achieved.

[0065] As Figure 3 shown, the various forces are respectively defined as follows: the boosting force X sail provided by the sail along the ship length direction and the lateral force Y sail along the ship width direction; the effective thrust X propeller provided by the propeller; the longitudinal component X rudder and the lateral component Y rudder of the rudder hydrodynamic force caused by the rudder angle δ to overcome yaw steering; the resistance X ship along the ship length direction suffered by the target wind power boosted ship during navigation; the yaw angle θ caused by the target wind power boosted ship, the hull yaw moment M hull and the lateral resistance Y ship suffered by the target wind power boosted ship at the yaw angle θ. According to the ship motion coordinate system, a planar motion model of the target wind power boosted ship is established, and the relationship between the forces is as follows, that is, the motion-force model:

[0066]

[0067] The lever arm L S is the longitudinal distance from the installation position of the target wind power boosting device to the center of gravity of the target wind power boosted ship. The lever arm L R is taken as the longitudinal distance from the rudder stock of the target wind power boosted ship to the center of gravity.

[0068] By establishing the sail force model, the hull hydrodynamic model and the rudder force model, X sail , Y sail , X rudder , Y rudder , X ship , M hull are obtained, and then the effective thrust X propeller of the propeller is obtained.

[0069] According to the aerodynamic characteristics of the set target wind power boosting device, a sail force model is established. According to the theory of sail aerodynamic characteristics, when the air flows through the surface of the target wind power boosting device, a velocity difference will be generated. The velocity difference is the pressure difference. Therefore, a lift force F L will be generated in the direction perpendicular to the relative wind direction, and a drag force F DThe components of lift and drag in the direction of ship navigation constitute the boosting force, and the components perpendicular to the navigation direction constitute the lateral force.

[0070] Low-speed air fluid is regarded as an incompressible fluid. According to the theory of the aerodynamic characteristics of the sail, the lift coefficient C L and the drag coefficient C D are only related to the angle of the wind flowing towards the sail, that is, the angle of attack α, and there is a one-to-one correspondence. The lift and drag of the sail are directly proportional to the air density, the sail area, and the square of the relative wind speed. Similarly, the boosting force and lateral force of the sail can also be expressed as:

[0071]

[0072] In the formula, ρ a is the air density, v is the encounter wind speed of the target wind-powered boosting ship, β is the relative wind direction angle, and A is the sail area;

[0073] C x,β , C Y,β are the longitudinal force and lateral force coefficients of the target wind-powered boosting device respectively.

[0074] Use wind tunnel test technology to predict the aerodynamic performance of the target wind-powered boosting device under steady state. Use the criteria of geometric similarity, kinematic similarity, and dynamic similarity to test and measure the aerodynamic forces (lift, drag) of the sail model at angles of attack from 0° to 180° with an interval of 10°. Nondimensionalize the aerodynamic forces measured in the test to obtain the lift coefficient and drag coefficient of the target wind-powered boosting device at different angles of attack. At this time, with the best boosting force as the control target, synthesize the lift coefficient and drag coefficient under each relative wind direction and decompose them along the longitudinal and lateral directions of the ship to obtain the longitudinal force coefficient and lateral force coefficient of the target wind-powered boosting device at a relative wind direction angle of 0° to 360°. The longitudinal force coefficient of the target wind-powered boosting device changes with the relative wind direction angle as shown in Figure 4 shown, and the lateral force coefficient changes with the relative wind direction angle as shown in Figure 5 shown.

[0075] Establish a hydrodynamic calculation model of the hull of the target wind-powered boosting ship. The resistance X ship along the ship length direction that the wind-powered boosting ship encounters during navigation is expressed as:

[0076] X ship = R Ts + ΔR

[0077] In the formula, R Ts , ΔR are the hull resistance of the target wind-powered boosting ship in the non-yawing, that is, straight-ahead state, and the resistance increment when the yaw angle is θ respectively. The expression of ΔR is:

[0078] ΔR = C·θ 2·R rs

[0079] In the formula, R rs is the residual resistance of the target wind-assisted ship in the straight-ahead state; C is the compensation coefficient of the target wind-assisted ship. In this example, by means of the computational fluid dynamics (CFD) method, the resistance of the target wind-assisted ship at different yaw angles is obtained.

[0080] The hull resistance R of the target wind-assisted ship in the straight-ahead state Ts is obtained from the ship model resistance test. Considering that usually the model test can only provide the resistance results at a specific draft, for the actual draft state of the target wind-assisted ship, the resistance results in the model test must be converted according to the displacement by the naval coefficient method. The conversion formula is:

[0081]

[0082] R Tβ_actualdraft is the converted hull resistance, and R Tβ_Balastorscantling is the hull resistance under the ballast draft or structural draft close to the actual mean draft and trim state of the target wind-assisted ship, is the actual displacement, is the displacement under the ballast draft or structural draft.

[0083] The yaw moment is based on the Kojima model in the MMG maneuvering motion model. The acting point of the moment is the center of gravity of the ship. The expression is:

[0084] M hull = N v v shipx

[0085] In the formula, v shipx is the longitudinal component of the speed of the target wind-assisted ship, and Nv is the rotational derivative of the hydrodynamic moment. The expression is:

[0086]

[0087] In the formula, d is the mean draft, and λ is the aspect ratio of the wind-assisted ship: λ = 2d / L PP ,

[0088] τ′ = (T a - T f ) / d,

[0089]

[0090] M hull is expressed as:

[0091]

[0092] So far, the establishment of the hull hydrodynamic calculation model of the target wind-assisted ship has been completed. Next, the rudder force model will be further established.

[0093] When establishing the rudder force model, due to the flow characteristics at the stern of the hull, the hull and the propeller will interfere with the force on the rudder. In this example, based on the rudder force characteristic model in the MMG maneuvering motion model, the rudder force model is established, and the expression is:

[0094]

[0095] In the formula, F N is the normal pressure of the rudder, δ is the rudder angle of the rudder, t R is the thrust deduction coefficient of the rudder; a H is the correction factor for the lateral force of the hull induced by steering. These two coefficients are for considering the interference of the hull and the propeller on the rudder, and the expressions are:

[0096]

[0097] In the formula, A R is the area of the rudder, f α is the slope of the lift coefficient of the rudder when the angle between the oncoming flow velocity and the rudder is 0, U R is the longitudinal effective oncoming flow velocity of the rudder, α R is the effective oncoming flow angle of attack of the rudder. So far, the longitudinal component X rudder and the lateral component Y rudder of the rudder hydrodynamic force can be expressed as relationships with the speed Vs of the target wind-assisted ship, the rudder angle δ, and the yaw angle θ.

[0098] Substitute the above-mentioned component force calculation models into the motion-force model of the target wind-assisted ship; at the same time, input the encountered wind conditions of the target wind-assisted ship, the parameters of the target wind-assisted device and the target wind-assisted ship into the motion-force model; solve the above motion-force model, and the propeller thrust, yaw angle, rudder angle and other navigation attitude parameters of the target wind-assisted ship under the action of wind assistance can be obtained.

[0099] Each item in the motion-force model has a definite expression. With the help of programming language for iterative solution, the propeller thrust, yaw angle, rudder angle and other navigation attitude parameters of the target wind-assisted ship under any wind conditions can be obtained.

[0100] So far, the solution of the force-motion equation of the target wind-assisted ship has been completed, and the effective propeller thrust X propeller is obtained. The effective propeller thrust is used as the calculation input parameter of the main engine power and fuel consumption model. After establishing the main engine power and fuel consumption model, the main engine fuel consumption of the target wind-assisted ship under the action of the wind-assisted device can be calculated. Next, the establishment of the main engine power and fuel consumption model will be carried out.

[0101] S3: Establish the main engine power and fuel consumption models.

[0102] Combined with the speed-power information of the target wind-assisted ship, taking the effective thrust of the propeller of the target wind-assisted ship under the action of the wind-assisted device as the input, establish the main engine power model and calculate the main engine power after the change of the propeller load of the target wind-assisted ship. Further, establish the main engine fuel consumption model and calculate the main engine fuel consumption of the target wind-assisted ship under the action of the wind-assisted device.

[0103] In this example, the propeller thrust X solved from the above motion-force model propeller , considering the thrust deduction t m , the thrust that the propeller of the target wind-assisted ship needs to generate is expressed as:

[0104]

[0105] Among them, the thrust deduction coefficient t m is obtained from the ship model test data.

[0106] The propeller advance speed is expressed as:

[0107]

[0108] In the formula, K T is the thrust coefficient of the propeller behind the ship; J is the advance speed coefficient; V A is the propeller advance speed; D is the propeller diameter, and ρ is the sea water density. According to the propeller open water test data, interpolate the propeller advance speed J and the torque coefficient K T / J 2 on the K Q curve after adding the sail. At this time, the main engine shaft power P D of the target wind-assisted ship after adding the sail is expressed as:

[0109]

[0110] η R is the propeller efficiency ratio and is obtained through model tests.

[0111] Further, based on the main engine fuel consumption technical materials, calculate the fuel consumption of the target wind-assisted ship in the current state:

[0112] SFC = interpolate(P B *, SFC*, P B )

[0113] Thus, the establishment of the main engine power and fuel consumption models is completed.

[0114] According to the effective propeller thrust X propeller , the fuel consumption of the main engine of the target wind-assisted ship under the action of the wind-assisted device can be solved. To evaluate the energy-saving situation of the wind-assisted device, it is necessary to further establish an energy efficiency benefit model for the wind-assisted ship, that is, a fuel consumption and energy efficiency benefit model, and calculate the main engine power and fuel consumption of the target wind-assisted ship with and without the wind-assisted device at the same speed. The energy efficiency benefit of the target wind-assisted ship is expressed as:

[0115]

[0116] In the formula, P D0 , P D are the main engine powers before and after adding sails of the target wind-assisted ship calculated according to the above main engine shaft power expression of the target wind-assisted ship, respectively.

[0117] Based on the above formula, the benefit measurement of the main engine power of the target wind-assisted ship can be completed. For the benefit measurement of other parameters such as fuel consumption, similarly, replace PD0 and PD with the fuel consumption before and after adding sails of the target wind-assisted ship calculated according to the above model and algorithm.

[0118] So far, the detailed description of the specific implementation manner of the present invention is completed.

Claims

1. A real-time energy efficiency assessment method for a wind-assisted ship, characterized in that: S1: Establish a ship motion coordinate system, define the 0 rib position of the ship as the origin of the x-axis, and the direction from the 0 rib position of the ship to the bow as the positive direction of the x-axis; define the ship's midship as the origin of the y-axis, and the direction from the midship to the port side of the ship as the positive direction of the y-axis; β is the relative wind direction angle. Define the wind coming from the bow direction as the 0° relative wind direction angle, which increases in a clockwise rotation. The range of the relative wind direction angle is 0° to 360°. During the movement of the target wind-assisted ship, the relative wind direction angle β is monitored in real time; S2: Obtain the sail boosting force X and the lateral force Y through the sail force model and the relative wind direction angle β monitored in real time sail and the lateral force Y sail , where ρa is the air density, v is the wind speed encountered by the target wind-assisted ship, A is the sail area, C x,β is the longitudinal force coefficient of the target wind power boosting device, C Y,β is the lateral force coefficient of the target wind power boosting device; Obtain the resistance X of the target wind-assisted ship along the ship length direction through the hull hydrodynamic model ship and the relationship with the yaw angle θ, as well as the yaw moment M hull , X ship = R Ts + ΔR Where: R Ts is the hull resistance of the target wind-assisted ship in the straight-ahead state without yaw, ΔR is the resistance increment when the yaw angle is θ, d is the mean draft, L PP is the length between perpendiculars of the target wind-assisted ship, λ is the aspect ratio of the wind-assisted ship, λ = 2d / L PP , τ′=(T a -T f ) / d, Obtain the longitudinal component X of the rudder hydrodynamic force through the rudder hydrodynamic force model rudder and the lateral component Y of the rudder hydrodynamic force rudder ; Where: F N is the positive pressure of the rudder, t R is the thrust deduction coefficient of the rudder, δ is the rudder angle of the rudder, C b is the block coefficient, a H is the correction factor for the lateral force induced by steering A R is the area of the rudder, f α is the slope of the lift coefficient of the rudder when the angle between the oncoming flow velocity and the rudder is 0, U R is the longitudinal effective oncoming flow velocity of the rudder, α R is the effective flow attack angle of the rudder; Establish a motion-force model for the target wind-assisted ship: And substitute the propulsive force Xsail of the wind along the ship length direction, the lateral force Ysail of the wind along the ship width direction, the longitudinal component Xrudder of the rudder hydrodynamic force, the lateral component Yrudder of the rudder hydrodynamic force, the resistance Xship along the ship length direction suffered by the target wind-assisted ship during navigation, the yaw angle θ of the target wind-assisted ship, and the lateral resistance Yship and yaw moment Mhull suffered by the target wind-assisted ship at the yaw angle θ into the motion-force model, where LS is the longitudinal distance from the installation position of the target wind-assisted device to the center of gravity of the target wind-assisted ship, L R is the longitudinal distance from the target wind-assisted ship rudder stock to the center of gravity; S3: Through the propeller thrust X propeller Obtain the fuel consumption SFC of the target wind-assisted ship in the current state.

2. The real-time energy efficiency assessment method for a wind-assisted ship according to claim 1, characterized in that: The target wind-assisted ship is provided with a wind condition sensor, and the wind condition sensor includes a wind direction sensor and a wind speed sensor. The wind direction sensor and the wind speed sensor are signal-connected to the sail turning power device.

3. The real-time energy efficiency evaluation method for a wind-assisted ship according to claim 1, characterized in that: The wind-assisted ship is a ship equipped with sails.

4. The real-time energy efficiency evaluation method of a wind-assisted ship according to claim 1, characterized in that: Both the target wind-assisted ship and the sail are regarded as rigid bodies, and elastic deformation is ignored.

Images