Linear modification method of water surface ship fairing

Abstract

The invention discloses a linear modification method for a water surface ship fairing, and relates to the technical field of ships, and the method comprises the steps: building a deformation control domain, and uniformly dispersing the deformation control domain into a plurality of discrete points; determining displacement values of discrete points on the missing top surface, the bottom surface, the middle longitudinal surface and the semi-ellipsoid side surface of the deformation control domain according to linear modification requirements; constructing a Laplacian displacement equation based on the linear modification demand of the minimum gradient of the displacement values of all discrete points, and solving the Laplacian displacement equation by using the displacement values of the discrete points to obtain the displacement values of other discrete points; and adopting an NURBS function and an interpolation algorithm to carry out interpolation according to the displacement value of each discrete point to obtain the displacement value of any curved surface control point of the to-be-deformed fairing, and carrying out linear modification to obtain a modified linear shape. According to the method, the fairing appearance can be quickly generated, and the optimization design and modeling efficiency of the fairing is improved.

Description

Technical Field

[0001] The present application relates to the field of ship technology, and in particular to a method for modifying the line shape of a surface ship fairing. Background Art

[0002] The surface ship fairing refers to the approximately spherical structure at the front of the bow below the designed waterline of the ship. The surface ship fairing is beneficial to reduce the resistance on the hull and thus improve the speed of the ship's navigation. However, the cavitation phenomenon in the surface ship fairing will also increase the ship's noise and affect the ship's noise level.

[0003] The influence of the surface ship shroud on the comprehensive performance of the ship is mainly related to the line shape of the surface ship shroud and the coupling between it and the main body of the ship must also be considered. Therefore, it is necessary to optimize the line shape of the surface ship shroud to optimize the comprehensive performance of the ship as much as possible. In the process of optimizing the line shape of the surface ship shroud, it is necessary to modify the line shape of the surface ship shroud frequently to evaluate the impact on the comprehensive performance of the ship under different line shapes. The current method of modifying the line shape of the surface ship shroud is mainly to use general 3D CAD software to manually adjust point by point. This method has low modification efficiency, and the modified line shape is also difficult to guarantee the most basic smoothness requirements, resulting in a cumbersome and inefficient design process, which affects the design efficiency of the surface ship shroud. Summary of the invention

[0004] In view of the above problems and technical requirements, this application proposes a method for modifying the line shape of a surface ship deflector. The technical solution of this application is as follows:

[0005] A method for modifying the line shape of a surface ship deflector comprises the following steps:

[0006] A deformation control domain is established according to the deflector to be deformed. The deformation control domain is a semi-ellipsoid with a missing top and wraps the deflector to be deformed. The long semi-axis of the deformation control domain is along the direction of the ship length, the horizontal semi-axis is along the direction of the ship width, and the vertical semi-axis is along the direction of the ship height.

[0007] The deformation control domain is uniformly discretized to obtain multiple discrete points;

[0008] Determine the displacement values ​​of discrete points on the missing top surface, bottom surface, mid-longitudinal surface and side surface of the semi-ellipsoid of the deformation control domain according to the requirements of line type modification; the bottom surface of the deformation control domain is the plane where the horizontal semi-axis and the vertical semi-axis are located and is perpendicular to the direction of the major semi-axis, the missing top surface of the deformation control domain is parallel to the bottom surface of the deformation control domain, and the mid-longitudinal surface of the deformation control domain is the plane where the major semi-axis and the vertical semi-axis are located and is perpendicular to the horizontal semi-axis;

[0009] The Laplace displacement equation is constructed based on the linear modification requirement of the minimum displacement gradient of all discrete points in the deformation control domain, and the Laplace displacement equation is solved by using the displacement values ​​of the discrete points on the missing top surface, bottom surface, middle longitudinal surface and side surface of the semi-ellipsoid of the deformation control domain to obtain the displacement values ​​of other discrete points in the deformation control domain;

[0010] The NURBS function and interpolation algorithm are used to interpolate the displacement value of any surface control point of the deformed fairing according to the displacement value of each discrete point in the deformation control domain. The line type of the deformed fairing is modified according to the displacement value of each surface control point to obtain the modified line type that meets the line type modification requirements.

[0011] A further technical solution is to uniformly discretize the deformation control domain to obtain multiple discrete points including:

[0012] The deformation control domain is uniformly discretized along the major semi-axis direction to obtain n including the missing top and bottom surfaces. u vertical sections; for each vertical section: divide the vertical section evenly along the horizontal semi-axis direction to obtain n sections including the section where the vertical semi-axis is located v -2 mutually parallel transverse segments and two curve segments on both sides. Each transverse segment and each curve segment are discretized uniformly along the vertical semi-axis direction to obtain n discrete points on the straight line where the horizontal semi-axis is located. w discrete points;

[0013] Each vertical section is discretized to obtain n v ×n w discrete points, the deformation control domain is discretized to obtain n u ×n v ×n w The position coordinates of the kth discrete point (i, j, k) from bottom to top on the jth tangent line segment starting from the port side on the i-th vertical section starting from the missing top surface in the global coordinate system are marked as (x i ,y j ,z k ); the global coordinate system takes the intersection of the vertical line passing through the front end point of the bow and the bottom surface of the hull as its origin, the positive direction of the x-axis points to the stern, the positive direction of the y-axis points to the starboard, and the positive direction of the z-axis is vertically upward; the long semi-axis direction of the deformation control domain is along the x-axis direction of the global coordinate system, the horizontal semi-axis direction is along the y-axis direction, and the vertical semi-axis direction is along the z-axis direction.

[0014] Its further technical solution is to determine the displacement values ​​of discrete points on the missing top surface, bottom surface, middle longitudinal surface and side surface of the semi-ellipsoid of the deformation control domain according to the line type modification requirements, including:

[0015] When the line type modification requirement indicates that the length of the deflector to be deformed along the long semi-axis direction is modified, the displacement values ​​of all discrete points on the bottom surface of the deformation control domain in the x direction, the y direction and the z direction are determined to be 0, and the displacement value of all discrete points on the missing top surface of the deformation control domain in the x direction is determined to be the target length displacement value, and the displacement values ​​in the y direction and the z direction are determined to be 0; when the line type modification requirement indicates that the deflector to be deformed is modified to be longer, the target length displacement value is negative; when the line type modification requirement indicates that the deflector to be deformed is modified to be shorter, the target length displacement value is positive; the absolute value of the target length displacement value is related to the length change of the deflector to be deformed;

[0016] When the linear modification requirement indicates that the width of the deflector to be deformed along the horizontal semi-axis direction is modified, the displacement values ​​of all discrete points on the mid-longitudinal plane of the deformation control domain in the x-direction, y-direction and z-direction are determined to be 0, and the displacement value of all discrete points on the left side surface of the semi-ellipsoid of the deformation control domain in the y-direction is determined to be the target width displacement value, and the displacement values ​​in the x-direction and z-direction are determined to be 0; the displacement values ​​of all discrete points on the right side surface of the semi-ellipsoid of the deformation control domain in the y-direction are determined to be equal in magnitude and opposite in direction to the displacement values ​​of all discrete points on the left side surface of the semi-ellipsoid, and the displacement values ​​in the x-direction and z-direction are determined to be 0; when the linear modification requirement indicates that the deflector to be deformed is modified to be wider, the target width displacement value is negative; when the linear modification requirement indicates that the deflector to be deformed is modified to be narrower, the target width displacement value is positive; the absolute value of the target width displacement value is related to the width change of the deflector to be deformed; wherein, all discrete points on the left side surface of the semi-ellipsoid include n on the curved segment close to the port side on each vertical section w discrete points; all discrete points on the right side of the semi-ellipsoid including the n points on the curved segments close to the starboard side on each vertical section w discrete points;

[0017] When the linear modification requirement indicates that the downward angle of the to-be-deformed shroud is modified along the vertical semi-axis direction, it is determined that the displacement values ​​of all discrete points on the bottom surface of the deformation control domain in the x-direction, the y-direction, and the z-direction are all 0, and the displacement value of all discrete points on the missing top surface of the deformation control domain in the z-direction is determined to be the target downward angle displacement value, and the displacement values ​​in the x-direction and the y-direction are 0; when the linear modification requirement indicates that the downward angle of the to-be-deformed shroud is modified to become smaller, the target downward angle displacement value is negative; when the linear modification requirement indicates that the downward angle of the to-be-deformed shroud is modified to become larger, the target downward angle displacement value is positive; the absolute value of the target downward angle displacement value is related to the change in the downward angle of the to-be-deformed shroud; the downward angle represents the angle between the line connecting the lowest point of the to-be-deformed shroud along the z-direction and the lowest point of the surface ship along the z-direction and the x-axis.

[0018] A further technical solution is that constructing the Laplace shift equation includes constructing the Laplace shift equation for any discrete point (i, j, k) as:

[0019]

[0020] Wherein, discrete point (i+1,j,k) is the adjacent discrete point of discrete point (i,j,k) in the direction of the major semi-axis, discrete point (i,j+1,k) is the adjacent discrete point of discrete point (i,j,k) in the direction of the horizontal semi-axis, and discrete point (i,j,k+1) is the adjacent discrete point of discrete point (i,j,k) in the direction of the vertical semi-axis; h ix is the distance between discrete point (i,j,k) and discrete point (i+1,j,k) in the direction of the major semi-axis, h iy is the distance between discrete point (i,j,k) and discrete point (i+1,j,k) in the horizontal semi-axis direction, h iz is the distance between discrete point (i,j,k) and discrete point (i+1,j,k) in the vertical semi-axis direction; f ijk is the displacement value of the discrete point (i, j, k), f (i+1)jk is the displacement value of the discrete point (i+1,j,k), f (i+2)jk is the displacement value of the discrete point (i+2,j,k), f i(j+1)k is the displacement value of the discrete point (i,j+1,k), f i(j+2)k is the displacement value of the discrete point (i,j+2,k), f ij(k+1) is the displacement value of the discrete point (i,j,k+1), f ij(k+2) is the displacement value of the discrete point (i,j,k+2).

[0021] Its further technical solution is that the target length displacement value is -20% to +50% of the distance between the missing top surface and the bottom surface of the deformation control domain along the x-direction; the target width displacement value is -20% to +40% of the horizontal semi-axis length of the bottom surface of the deformation control domain; and the target downward angle displacement value is -40% to +100% of the vertical semi-axis length of the bottom surface of the deformation control domain.

[0022] A further technical solution is that determining the displacement value of any surface control point of the deflector to be deformed includes:

[0023] Using NURBS functions and interpolation algorithms to construct a linear equation system of interpolation coefficients including unknown interpolation coefficients;

[0024] The interpolation coefficient U in the linear equation group is obtained by solving the position coordinates and displacement values ​​of all discrete points in the deformation control domain in the global coordinate system. ijk ;

[0025] The displacement value of the current surface control point is determined according to the position coordinates of any surface control point of the deflector to be deformed in the global coordinate system by using the interpolation coefficient linear equation group.

[0026] A further technical solution is that the interpolation coefficient linear equation group is:

[0027]

[0028] Among them, S(u,v,w) is the displacement value of any position coordinate (u,v,w) in the global coordinate system, N i,p (u) is the i-th p-order B-spline basis function, N j,q (v) is the j-th q-order B-spline basis function, N k,r (w) is the kth r-order B-spline basis function, represents the tensor product, and the expression of the B-spline basis function is:

[0029]

[0030] A further technical solution is to solve the interpolation coefficients U in the interpolation coefficient linear equations according to the position coordinates and displacement values ​​of all discrete points in the deformation control domain in the global coordinate system. ijk include:

[0031] The position coordinates (x i ,y j ,z k ) is converted to the corresponding normalized position coordinates (u i ,v j ,w k )and Among them, x max is the maximum value of the x coordinate of all discrete points in the deformation control domain, x min is the minimum value of the x coordinate of all discrete points in the deformation control domain, and y max is the maximum value of the y coordinate of all discrete points in the deformation control domain, y min is the minimum value of the y coordinate of all discrete points in the deformation control domain, z max is the maximum value of the z coordinate of all discrete points in the deformation control domain, z min is the minimum value of the z coordinate of all discrete points in the deformation control domain;

[0032] according to Solve the interpolation coefficient linear equation system to obtain the interpolation coefficient U ijk , f ijk is the displacement value of the discrete point (i,j,k).

[0033] The beneficial technical effects of this application are:

[0034] The present application proposes a method for modifying the linear shape of a surface ship fairing, which can fully fit the fairing to be deformed by constructing a deformation control domain of a semi-ellipsoid with a missing top, thereby reducing the redundant space in the deformation control domain. The deformation control domain is discretized into multiple discrete points as a whole, and the displacement values ​​of the discrete points on the missing top surface, bottom surface, middle longitudinal surface and side surface of the semi-ellipsoid are specified, and the displacement value of each surface control point is obtained by interpolation calculation. The surface control points within the entire deformation control domain can be modified, and rapid deformation of the fairing to be deformed along different dimensions such as length, width, and downward angle can be achieved within a specified range. At the same time, it ensures that the deformed fairing has a smooth appearance and a smooth transition with the main body of the ship, enhances the coupling with the surface ship, and helps to improve the comprehensive performance of the surface ship.

[0035] By introducing the NURBS interpolation method of the Laplace displacement equation to calculate the displacement value of each surface control point, the line type with the smallest displacement value gradient change can be obtained. Compared with the traditional FFD method, the method of this application can generate a smoother deformation of the deflector line type. By constructing the Laplace displacement equation for all discrete points and using the NURBS function and interpolation algorithm to establish the interpolation space, the displacement values ​​of all surface control points in the deformation control domain can be calculated at one time, which improves the optimization design and modeling efficiency of the deflector, and helps to obtain a higher performance smooth deflector shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a flow chart of the line type modification method.

[0037] Figure 2 It is the deformation control domain annotation diagram.

[0038] Figure 3 It is a schematic diagram of the established deformation control domain.

[0039] Figure 4 It is a discretization diagram of the deformation control domain.

[0040] Figure 5 It is a schematic diagram of the global coordinate system.

[0041] Figure 6 The linear modification requirement indicates to modify the length of the deformed fairing along the major semi-axis direction.

[0042] Figure 7 The linear modification requirement indicates to modify the width of the deformed fairing along the horizontal semi-axis direction.

[0043] Figure 8 The linear modification requirement indicates to modify the downward angle of the deformed fairing along the vertical semi-axis direction.

[0044] Fig. 9 This is a comparison chart before and after modifying the length of the air duct.

[0045] Fig.10 This is a comparison chart before and after modifying the width of the air shroud.

[0046] Fig.11 This is a comparison chart before and after modifying the downward angle of the fairing. DETAILED DESCRIPTION

[0047] The specific implementation of the present application is further described below in conjunction with the accompanying drawings.

[0048] This application proposes a method for modifying the line shape of a surface ship deflector, please refer to Figure 1 The specific steps are as follows:

[0049] Step 1: Establish a deformation control domain according to the deflector to be deformed. Since the deflector is installed at the bulbous bow of the surface ship, the front part of the bulbous bow is a protruding spherical structure. Therefore, in order to design a deflector that fully fits the bulbous bow, establish a deformation control domain with a topless semi-ellipsoid structure and wrap the deflector to be deformed. For the specific position structure, please refer to Figure 2 The center line of the deformation control domain is aligned with the center line of the deflector to be deformed, the long semi-axis of the deformation control domain is along the direction of the ship length, the horizontal semi-axis is along the direction of the ship width, and the vertical semi-axis is along the direction of the ship height.

[0050] exist Figure 2 A deformation control domain is constructed at the marked position shown. The missing top surface of the missing top semi-ellipsoid is spaced a certain distance from the front end and bottom of the bulbous bow. The spacing distance is set according to the design requirements of the fairing, for example, it is set to 25mm. The missing top surface and bottom surface of the deformation control domain are both elliptical planes. The bottom surface is the plane where the horizontal semi-axis and the vertical semi-axis are located and is perpendicular to the major semi-axis direction. The missing top surface and bottom surface of the deformation control domain are parallel to each other. The distance between the missing top surface and the bottom surface is the length of the deformation control domain, recorded as l, twice the length of the horizontal semi-axis of the bottom surface is the width of the deformation control domain, recorded as W, and twice the length of the vertical semi-axis of the bottom surface is the height of the deformation control domain, recorded as H. A deformation control domain with a length of l = 1270mm, a width of W = 960mm, and a height of H = 460mm is constructed as shown in the figure. Figure 3 As shown in the figure, the red area is the deformation control domain, the hollow circle is the surface control point Pc on the bulbous bow surface, the part wrapped by the deformation control domain is the deformation domain, and the rest is the non-deformation domain. The deformation domain contains all the surface control points of the deflector to be deformed.

[0051] Step 2, uniformly discretize the deformation control domain to obtain multiple discrete points. In the prior art, multiple discrete points can be obtained by uniformly dividing the outer surface of the deformation control domain. This method can only control the surface control points near the outer surface of the deformation control domain. However, the present application discretizes the entire deformation control domain to better control the surface control points at any position inside the deformation control domain.

[0052] In one embodiment, the deformation control domain is uniformly discretized along the long semi-axis direction to obtain n including the missing top surface and the bottom surface. u For each vertical section: divide the vertical section evenly along the horizontal semi-axis direction to obtain n sections including the section where the vertical semi-axis is located. v -2 mutually parallel transverse segments and two curve segments on both sides. Each transverse segment and each curve segment are discretized uniformly along the vertical semi-axis direction to obtain n discrete points on the straight line where the horizontal semi-axis is located. w discrete points. Figure 4 (a) is a schematic diagram of uniformly discretizing a vertical section. Three parallel line segments and two curve segments are uniformly divided along the horizontal semi-axis direction. The line segment in the middle column is the line segment where the vertical semi-axis is located. Then, each line segment and each curve segment are uniformly discretized into five discrete points along the vertical semi-axis direction. The line segment in the middle row is the straight line where the horizontal semi-axis is located.

[0053] Each vertical section is discretized in the above manner to ensure that the number of discrete points on each vertical section is the same, and n points are obtained on each vertical section. v ×n w discrete points, the deformation control domain is discretized to obtain n u ×n v ×n w discrete points, the result after the deformation control domain is discretized is as follows Figure 4 (b) The position coordinates of the kth discrete point (i, j, k) from bottom to top on the jth section segment starting from the port side on the i-th vertical section starting from the missing top surface in the global coordinate system are marked as (x i ,y j ,z k ). Among them, i, j, k are all integers and i∈[1,n u ], j∈[1,n v ], k∈[1,n w ],n u 、n v 、n w The value of can be customized according to the needs. Considering the calculation accuracy and efficiency, each vertical section is generally discretized into 5 to 10 discrete points. Figure 5 As shown in the figure, the intersection of the vertical line passing through the front end of the bow and the bottom of the hull is taken as the origin, the positive direction of the x-axis points to the stern, the positive direction of the y-axis points to the starboard, and the positive direction of the z-axis is vertically upward. The long semi-axis direction of the deformation control domain is along the x-axis direction of the global coordinate system, the horizontal semi-axis direction is along the y-axis direction, and the vertical semi-axis direction is along the z-axis direction.

[0054] Step 3: Determine the displacement values ​​of the discrete points on the missing top surface, bottom surface, mid-longitudinal surface and side surface of the semi-ellipsoid of the deformation control domain according to the requirements of line type modification. The bottom surface of the deformation control domain is the plane where the horizontal semi-axis and the vertical semi-axis are located and is perpendicular to the long semi-axis direction. The missing top surface of the deformation control domain is parallel to the bottom surface of the deformation control domain. The mid-longitudinal surface of the deformation control domain is the plane where the long semi-axis and the vertical semi-axis are located and is perpendicular to the horizontal semi-axis. The side surface of the semi-ellipsoid of the deformation control domain is the curved surface located on both sides of the mid-longitudinal surface along the horizontal semi-axis direction.

[0055] The linear modification requirement of the present application is to modify at least one of the length, width and downward angle of the fairing to be deformed. Modifying the downward angle of the fairing to be deformed can adjust the up and down deformation of the head end of the fairing to be deformed along the vertical semi-axis direction. The downward angle represents the angle between the line connecting the lowest point of the fairing to be deformed along the z direction and the lowest point of the surface ship along the z direction and the x-axis.

[0056] In one embodiment, when the linear modification requirement indicates that the length of the air deflector to be deformed along the long semi-axis direction is modified, fixed constraints are applied to the discrete points on the bottom surface of the deformation control domain, and displacement constraints are applied to the discrete points on the missing top surface of the deformation control domain. It is determined that the displacement values ​​of all discrete points on the bottom surface of the deformation control domain in the x-direction, y-direction and z-direction are all 0, and the displacement values ​​of all discrete points on the missing top surface of the deformation control domain in the x-direction are determined to be the target length displacement value, and the displacement values ​​in the y-direction and z-direction are determined to be 0. When the linear modification requirement indicates that the air deflector to be deformed is modified to be longer, the target length displacement value is negative; when the linear modification requirement indicates that the air deflector to be deformed is modified to be shorter, the target length displacement value is positive; the absolute value of the target length displacement value is related to the length change of the air deflector to be deformed. Among them, the target length displacement value is set according to the linear modification requirements. In this application, the target length displacement value is set to -20% to +50% of the distance (length l) between the missing top surface and the bottom surface of the deformation control domain along the x direction, that is, the length of the modified deflector to be deformed can be lengthened by at most 20% of the length l of the deflector to be deformed, and the length of the modified deflector to be deformed can be shortened by at most 50% of the length l of the deflector to be deformed. For example, if the length of the modified deflector to be deformed is lengthened by 30mm, the target length displacement value is -30mm, and the setting of the deformation control domain is as follows: Figure 6 shown.

[0057] When the linear modification requirement indicates to modify the width of the deflector to be deformed along the horizontal semi-axis direction, a fixed constraint is applied to the mid-longitudinal surface of the deformation control domain, and a displacement constraint is applied to the side surface of the semi-ellipsoid of the deformation control domain. It is determined that the displacement values ​​of all discrete points on the mid-longitudinal surface of the deformation control domain in the x, y and z directions are all 0, and the displacement values ​​of all discrete points on the left side surface of the semi-ellipsoid of the deformation control domain in the y direction are determined to be the target width displacement value, and the displacement values ​​in the x and z directions are 0; it is determined that the displacement values ​​of all discrete points on the right side surface of the semi-ellipsoid of the deformation control domain in the y direction are equal to the displacement values ​​of all discrete points on the left side surface of the semi-ellipsoid of the deformation control domain, and the displacement values ​​in the x and z directions are 0. When the line type modification requirement indicates that the deformed shroud is to be widened, the target width displacement value is negative, and when the line type modification requirement indicates that the deformed shroud is to be narrowed, the target width displacement value is positive; the absolute value of the target width displacement value is related to the width change of the deformed shroud; among them, all discrete points on the left surface of the semi-ellipsoid include n points on the curved segment close to the port side on each vertical section w discrete points; all discrete points on the right side of the semi-ellipsoid including the n points on the curved segments close to the starboard side on each vertical section w discrete points. Among them, the target width displacement value is set according to the line type modification requirements. This application sets the target width displacement value to be -20% to +40% of the horizontal semi-axis length of the bottom surface of the deformation control domain, that is, the width of the to-be-deformed air guide hood is modified to be at most 20% of the width W of the to-be-deformed air guide hood, and the width of the to-be-deformed air guide hood is modified to be at most 10% of the width W of the to-be-deformed air guide hood. For example, the width of the to-be-deformed air guide hood is modified to be 30mm wider. At this time, the displacement value of all discrete points on the left surface of the semi-ellipsoid is the target width displacement value of -30mm, and the displacement value of all discrete points on the right surface of the semi-ellipsoid is +30mm. The setting of the deformation control domain is as follows: Figure 7 shown.

[0058] When the linear modification requirement indicates to modify the downward angle of the to-be-deformed shroud along the vertical semi-axis direction, a fixed constraint is applied to the bottom surface of the deformation control domain, and a displacement constraint is applied to the missing top surface of the deformation control domain. Since the lowest point of the to-be-deformed shroud along the z direction and the lowest point of the surface ship along the z direction are both located on the xz plane, the downward angle of the to-be-deformed shroud can be modified by adjusting the displacement value of the discrete points on the missing top surface along the z direction. It is determined that the displacement values ​​of all discrete points on the bottom surface of the deformation control domain in the x, y, and z directions are all 0, and the displacement values ​​of all discrete points on the missing top surface of the deformation control domain in the z direction are determined to be the target downward angle displacement value, and the displacement values ​​in the x and y directions are 0. When the linear modification requirement indicates to modify the downward angle of the to-be-deformed shroud to be smaller, the displacement value of the target downward angle is negative; when the linear modification requirement indicates to modify the downward angle of the to-be-deformed shroud to be larger, the displacement value of the target downward angle is positive; the absolute value of the displacement value of the target downward angle is related to the change in the downward angle of the to-be-deformed shroud. Among them, the target downward angle displacement value is set according to the requirements of line type modification. In this application, the target downward angle displacement value is set to -40% to +100% of the vertical semi-axis length of the bottom surface of the deformation control domain, that is, the top surface of the air deflector to be deformed is modified to move downward by at most 20% of the height L of the air deflector to be deformed, and the top surface of the air deflector to be deformed is modified to move upward by at most 50% of the height L of the air deflector to be deformed. For example, if the top surface of the air deflector to be deformed is modified to move downward by 30mm, the target downward angle displacement value is -30mm, and the setting of the deformation control domain is as follows: Figure 8 shown.

[0059] Step 4: Construct the Laplace displacement equation based on the linear modification requirement of the minimum displacement gradient of all discrete points in the deformation control domain, and solve the Laplace displacement equation using the displacement values ​​of discrete points on the top, bottom, mid-longitudinal and side surfaces of the semi-ellipsoid of the deformation control domain to obtain the displacement values ​​of other discrete points in the deformation control domain.

[0060] This application introduces the Laplace constraint to minimize the gradient of the displacement value of the discrete points in the entire control domain, thereby ensuring that the surface of the deflector after deformation is smoother than that of the traditional FFD method. The displacement value of each discrete point in the deformation control domain satisfies the Laplace equation. In one embodiment, the Laplace shift equation is constructed for any discrete point (i, j, k):

[0061]

[0062] Wherein, discrete point (i+1,j,k) is the adjacent discrete point of discrete point (i,j,k) in the direction of the major semi-axis, discrete point (i,j+1,k) is the adjacent discrete point of discrete point (i,j,k) in the direction of the horizontal semi-axis, and discrete point (i,j,k+1) is the adjacent discrete point of discrete point (i,j,k) in the direction of the vertical semi-axis; h ix is the distance between discrete point (i,j,k) and discrete point (i+1,j,k) in the direction of the major semi-axis, h iy is the distance between discrete point (i,j,k) and discrete point (i+1,j,k) in the horizontal semi-axis direction, h iz is the distance between discrete point (i,j,k) and discrete point (i+1,j,k) in the vertical semi-axis direction; f ijk is the displacement value of the discrete point (i, j, k), f (i+1)jk is the displacement value of the discrete point (i+1,j,k), f (i+2)jk is the displacement value of the discrete point (i+2,j,k), f i(j+1)k is the displacement value of the discrete point (i,j+1,k), f i(j+2)k is the displacement value of the discrete point (i,j+2,k), f ij(k+1) is the displacement value of the discrete point (i,j,k+1), f ij(k+2) is the displacement value of the discrete point (i,j,k+2).

[0063] In order to solve the Laplace shift equation, the Laplace shift equation (1) is expressed in matrix form as follows:

[0064]

[0065] In the same way, the matrix form of the Laplace shift equation is listed for discrete points (i+1,j,k):

[0066]

[0067] Integrate formula (2) and formula (3) into a matrix equation:

[0068]

[0069] By analogy, the Laplace shift equations of all discrete points are integrated into one Laplace shift equation, and its corresponding matrix equation form is:

[0070] Mf=N (5)

[0071] Wherein, M is the coefficient matrix, whose number of rows and columns are the total number of discrete points in the deformation control domain; f is the displacement vector to be solved, and the elements in the displacement vector f are the displacement values ​​of all discrete points; N is the right-hand vector, whose elements are initialized to 0.

[0072] Then, the displacement values ​​of the discrete points on the missing top surface, bottom surface, middle longitudinal surface and side surface of the semi-ellipsoid of the deformation control domain are used to update the element values ​​in the coefficient matrix M, the displacement vector f and the right-end vector N. For a discrete point (i, j, k), if the discrete point is located on the missing top surface, bottom surface, middle longitudinal surface and side surface of the semi-ellipsoid of the deformation control domain, the displacement value of the point is known. Assuming that the displacement value of the discrete point is in the mth row of the displacement vector f, the element in the mth row and mth column of the coefficient matrix M is set to 1, the remaining elements in the mth row are set to 0, and the element in the mth row of the right-end vector N is set to the corresponding displacement value. The displacement values ​​of all discrete points on the missing top surface, bottom surface, middle longitudinal surface and side surface of the semi-ellipsoid of the deformation control domain are updated to the matrix equation. At this time, only the displacement values ​​of other discrete points in the deformation control domain are unknown in the matrix equation. Therefore, the Laplace displacement equation is solved to obtain the displacement values ​​of other discrete points in the deformation control domain.

[0073] Step 5: Using NURBS function and interpolation algorithm, according to the displacement values ​​of each discrete point in the deformation control domain, interpolate the displacement value of any surface control point of the deflector to be deformed.

[0074] In one embodiment, the specific steps of determining the displacement value of any surface control point of the deflector to be deformed are:

[0075] (1) The interpolation coefficient linear equation system containing unknown interpolation coefficients is constructed using NURBS function and interpolation algorithm:

[0076]

[0077] Among them, S(u,v,w) is the displacement value of any position coordinate (u,v,w) in the global coordinate system, N i,p (u) is the i-th p-order B-spline basis function, N j,q (v) is the j-th q-order B-spline basis function, N k,r (w) is the kth r-order B-spline basis function, represents the tensor product, and the expression of the B-spline basis function is:

[0078]

[0079] Among them, N i,p (u), N j,q (v) N k,r (w) can be calculated by formula (7). The orders p, q, and k of the B-spline basis function can be set according to the accuracy requirements of the line type modification. The higher the order, the higher the accuracy, but the greater the amount of calculation. In order to improve the calculation efficiency while ensuring the accuracy, the order is generally set to 2.

[0080] (2) The interpolation coefficient U in the linear equation group is obtained by solving the position coordinates and displacement values ​​of all discrete points in the deformation control domain in the global coordinate system. ijk .

[0081] In one embodiment, the position coordinates of all discrete points in the global coordinate system are normalized along the x, y, and z directions to obtain dimensionless position coordinates. The normalized position coordinates represent the relative positions of the discrete points in the deformation control domain along the corresponding directions. The position coordinates (x i ,y j ,z k ) is converted to the corresponding normalized position coordinates (u i ,v j ,w k )and Among them, x max is the maximum value of the x coordinate of all discrete points in the deformation control domain, x min is the minimum value of the x coordinate of all discrete points in the deformation control domain, and y max is the maximum value of the y coordinate of all discrete points in the deformation control domain, y min is the minimum value of the y coordinate of all discrete points in the deformation control domain, z max is the maximum value of the z coordinate of all discrete points in the deformation control domain, z min is the minimum value of the z coordinates of all discrete points in the deformation control domain.

[0082] The normalized position coordinates (u i ,v j ,w k ) and displacement value f ijk Substituting into the equation Solve the interpolation coefficient linear equation system to obtain the interpolation coefficient U ijk , f ijk is the displacement value of the discrete point (i,j,k).

[0083] (3) Using the interpolation coefficient linear equation group, the displacement value of the current surface control point is determined according to the position coordinates of any surface control point of the deflector to be deformed in the global coordinate system.

[0084] For any surface control point Pc, its position coordinates Pc (x, y, z) in the global coordinate system are converted to normalized position coordinates (u(p c ),v(p c ),w(p c )), and then substitute it into formula (6) to obtain the displacement value S(u(p c ),v(p c),w(p c ))=(ΔP cu ,ΔP cv ,ΔP cw ), the interpolation coefficient U in formula (6) ijk It has been calculated in (2).

[0085] Step 6: Modify the line type of the deformed fairing according to the displacement value of each surface control point to obtain a modified line type that meets the line type modification requirements.

[0086] For any surface control point Pc, the position coordinates of Pc after line shape modification (x+ΔP cu ,y+ΔP cv ,z+ΔP cw ). Substituting the position coordinates of all the surface control points on the deflector to be deformed into the NURBS curve equation, the modified line type can be obtained. The specific form of the NURBS curve equation can refer to the content of the prior art, and this application will not repeat it.

[0087] According to the target length displacement value in step 3, the length of the to-be-deformed air deflector is modified linearly to deform the to-be-deformed air deflector. The comparison results between the deformed air deflector and the original to-be-deformed air deflector are as follows: Fig. 9 As shown in FIG. 1 , the length of the deformed air deflector is longer than that of the original air deflector to be deformed. According to the target width displacement value in step 3, the width of the air deflector to be deformed is linearly modified to deform the air deflector to be deformed. The comparison results between the deformed air deflector and the original air deflector to be deformed are shown in FIG. Fig.10 As shown, the width of the deformed guide cover is wider than that of the original guide cover to be deformed. According to the target downward angle displacement value in step 3, the downward angle of the guide cover to be deformed is linearly modified to deform the guide cover to be deformed. The comparison results between the deformed guide cover and the original guide cover to be deformed are shown in Fig.11 As shown, the downward angle of the deformed air deflector becomes larger than that of the original air deflector to be deformed.

[0088] The above is only a preferred embodiment of the present application, and the present application is not limited to the above embodiments. It is understood that other improvements and changes directly derived or associated by those skilled in the art without departing from the spirit and concept of the present application should be considered to be included in the protection scope of the present application.

Claims

1. A method for modifying the line shape of a surface ship deflector, characterized in that: The line type modification method comprises: A deformation control domain is established according to the to-be-deformed fairing, wherein the deformation control domain is a semi-ellipsoid with a missing top and wraps the to-be-deformed fairing, wherein the long semi-axis of the deformation control domain is along the ship length direction, the horizontal semi-axis is along the ship width direction, and the vertical semi-axis is along the ship height direction; Uniformly discretizing the deformation control domain to obtain a plurality of discrete points; Determine the displacement values ​​of the discrete points on the missing top surface, bottom surface, middle longitudinal surface and side surface of the semi-ellipsoid of the deformation control domain according to the line type modification requirements; the bottom surface of the deformation control domain is the plane where the horizontal semi-axis and the vertical semi-axis are located and is perpendicular to the direction of the long semi-axis, the missing top surface of the deformation control domain is parallel to the bottom surface of the deformation control domain, and the middle longitudinal surface of the deformation control domain is the plane where the long semi-axis and the vertical semi-axis are located and is perpendicular to the horizontal semi-axis; A Laplace displacement equation is constructed based on the linear modification requirement of the minimum displacement gradient of all discrete points in the deformation control domain, and the Laplace displacement equation is solved by using the displacement values ​​of the discrete points on the missing top surface, bottom surface, middle longitudinal surface and side surface of the semi-ellipsoid of the deformation control domain to obtain the displacement values ​​of other discrete points in the deformation control domain; The displacement value of any surface control point of the to-be-deformed air deflector is interpolated by using NURBS function and interpolation algorithm according to the displacement value of each discrete point in the deformation control domain, and the line type of the to-be-deformed air deflector is modified according to the displacement value of each surface control point to obtain a modified line type that meets the line type modification requirements.

2. The line type modification method according to claim 1, characterized in that: The deformation control domain is uniformly discretized to obtain a plurality of discrete points including: The deformation control domain is uniformly discretized along the long semi-axis direction to obtain n u vertical sections; for each vertical section: evenly divide the vertical section along the horizontal semi-axis direction to obtain n sections including the section segment where the vertical semi-axis is located. v -2 mutually parallel transverse segments and two curve segments on both sides. Each transverse segment and each curve segment are discretized uniformly along the vertical semi-axis direction to obtain n discrete points on the straight line where the horizontal semi-axis is located. w discrete points; Each vertical section is discretized to obtain n v ×n w discrete points, the deformation control domain is discretized to obtain n u ×n v ×n w The position coordinates of the kth discrete point (i, j, k) from bottom to top on the jth tangent line segment starting from the port side on the i-th vertical section starting from the missing top surface in the global coordinate system are marked as (x i ,y j ,z k ); the global coordinate system takes the intersection of the vertical line passing through the front end point of the bow and the bottom surface of the hull as the origin, the positive direction of the x-axis points to the stern, the positive direction of the y-axis points to the starboard, and the positive direction of the z-axis is vertically upward; the long semi-axis direction of the deformation control domain is along the x-axis direction of the global coordinate system, the horizontal semi-axis direction is along the y-axis direction, and the vertical semi-axis direction is along the z-axis direction.

3. The line type modification method according to claim 2, characterized in that: Determining the displacement values ​​of discrete points on the missing top surface, bottom surface, mid-longitudinal surface and side surface of the semi-ellipsoid of the deformation control domain according to the line type modification requirements includes: When the line type modification requirement indicates that the length of the air deflector to be deformed along the long semi-axis direction is modified, it is determined that the displacement values ​​of all discrete points on the bottom surface of the deformation control domain in the x direction, the y direction and the z direction are all 0, and the displacement values ​​of all discrete points on the top surface of the deformation control domain in the x direction are determined to be the target length displacement value, and the displacement values ​​in the y direction and the z direction are 0; when the line type modification requirement indicates that the air deflector to be deformed is modified to be longer, the target length displacement value is negative; when the line type modification requirement indicates that the air deflector to be deformed is modified to be shorter, the target length displacement value is positive; the absolute value of the target length displacement value is related to the length change of the air deflector to be deformed; When the line type modification requirement indicates that the width of the deflector to be deformed along the horizontal semi-axis direction is modified, it is determined that the displacement values ​​of all discrete points on the mid-longitudinal plane of the deformation control domain in the x-direction, the y-direction and the z-direction are all 0, and the displacement value of all discrete points on the left side surface of the semi-ellipsoid of the deformation control domain in the y-direction is the target width displacement value, and the displacement values ​​in the x-direction and the z-direction are 0; it is determined that the displacement values ​​of all discrete points on the right side surface of the semi-ellipsoid of the deformation control domain in the y-direction are equal in magnitude and opposite in direction to the displacement values ​​of all discrete points on the left side surface of the semi-ellipsoid, and the displacement values ​​in the x-direction and the z-direction are 0; when the line type modification requirement indicates that the deflector to be deformed is modified to be wider, the target width displacement value is negative; when the line type modification requirement indicates that the deflector to be deformed is modified to be narrower, the target width displacement value is positive; the absolute value of the target width displacement value is related to the width change of the deflector to be deformed; wherein, all discrete points on the left side surface of the semi-ellipsoid include n on the curved segment close to the port side on each vertical section w discrete points; all discrete points on the right side of the semi-ellipsoid including the n points on the curved segments close to the starboard side on each vertical section w discrete points; When the line type modification requirement indicates that the downward angle of the to-be-deformed fairing is modified along the vertical semi-axis direction, it is determined that the displacement values ​​of all discrete points on the bottom surface of the deformation control domain in the x direction, y direction, and z direction are all 0, and the displacement value of all discrete points on the missing top surface of the deformation control domain in the z direction is determined to be the target downward angle displacement value, and the displacement values ​​in the x direction and y direction are 0; when the line type modification requirement indicates that the downward angle of the to-be-deformed fairing is modified to be smaller, the target downward angle displacement value is negative; when the line type modification requirement indicates that the downward angle of the to-be-deformed fairing is modified to be larger, the target downward angle displacement value is positive; the absolute value of the target downward angle displacement value is related to the change in the downward angle of the to-be-deformed fairing; the downward angle represents the angle between the line connecting the lowest point of the to-be-deformed fairing along the z direction and the lowest point of the surface ship along the z direction and the x-axis.

4. The line type modification method according to claim 2, characterized in that: Constructing the Laplace shift equation includes constructing the Laplace shift equation for any discrete point (i, j, k) as: Wherein, discrete point (i+1,j,k) is the adjacent discrete point of discrete point (i,j,k) in the direction of the major semi-axis, discrete point (i,j+1,k) is the adjacent discrete point of discrete point (i,j,k) in the direction of the horizontal semi-axis, and discrete point (i,j,k+1) is the adjacent discrete point of discrete point (i,j,k) in the direction of the vertical semi-axis; h ix is the distance between discrete point (i,j,k) and discrete point (i+1,j,k) in the direction of the major semi-axis, h iy is the distance between discrete point (i,j,k) and discrete point (i+1,j,k) in the horizontal semi-axis direction, h iz is the distance between discrete point (i,j,k) and discrete point (i+1,j,k) in the vertical semi-axis direction; f ijk is the displacement value of the discrete point (i, j, k), f (i+1)jk is the displacement value of the discrete point (i+1,j,k), f (i+2)jk is the displacement value of the discrete point (i+2,j,k), f i(j+1)k is the displacement value of the discrete point (i,j+1,k), f i(j+2)k is the displacement value of the discrete point (i,j+2,k), f ij(k+1) is the displacement value of the discrete point (i,j,k+1), f ij(k+2) is the displacement value of the discrete point (i,j,k+2).

5. The line type modification method according to claim 3, characterized in that: The target length displacement value is -20% to +50% of the distance between the top surface and the bottom surface of the deformation control domain along the x-direction; the target width displacement value is -20% to +40% of the horizontal semi-axis length of the bottom surface of the deformation control domain; and the target downward angle displacement value is -40% to +100% of the vertical semi-axis length of the bottom surface of the deformation control domain.

6. The line type modification method according to claim 2, characterized in that: Determining the displacement value of any surface control point of the to-be-deformed fairing includes: Using NURBS functions and interpolation algorithms to construct a linear equation system of interpolation coefficients including unknown interpolation coefficients; The interpolation coefficient U in the interpolation coefficient linear equation group is obtained by solving the position coordinates and displacement values ​​of all discrete points in the deformation control domain in the global coordinate system. ijk ; The interpolation coefficient linear equation group is used to determine the displacement value of the current surface control point according to the position coordinates of any surface control point of the deflector to be deformed in the global coordinate system.

7. The line type modification method according to claim 6, characterized in that: The interpolation coefficient linear equations are: Among them, S(u,v,w) is the displacement value of any position coordinate (u,v,w) in the global coordinate system, N i,p (u) is the i-th p-order B-spline basis function, N j,q (v) is the j-th q-order B-spline basis function, N k,r (w) is the kth r-order B-spline basis function, represents the tensor product, and the expression of the B-spline basis function is:

8. The line type modification method according to claim 7, characterized in that: The interpolation coefficient U in the interpolation coefficient linear equation group is obtained by solving the position coordinates and displacement values ​​of all discrete points in the deformation control domain in the global coordinate system. ijk include: The position coordinates (x i ,y j ,z k ) is converted to the corresponding normalized position coordinates (u i ,v j ,w k )and Among them, x max is the maximum value of the x coordinates of all discrete points in the deformation control domain, x min is the minimum value of the x coordinate of all discrete points in the deformation control domain, and y max is the maximum value of the y coordinates of all discrete points in the deformation control domain, y min is the minimum value of the y coordinate of all discrete points in the deformation control domain, z max is the maximum value of the z coordinate of all discrete points in the deformation control domain, z min is the minimum value of the z coordinates of all discrete points in the deformation control domain; according to Solve the interpolation coefficient linear equation system to obtain the interpolation coefficient U ijk , f ijk is the displacement value of the discrete point (i,j,k).

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