A method for designing the profile of a variable cross-section transition section of an underwater vehicle

Abstract

The present invention proposes a method for designing the profile of a variable-section transition section of an underwater vehicle, which can not only define the existing low-drag line shape on the transition surface to ensure that the surface has a better drag reduction performance, but also accurately give the function of the transition surface. It includes: step 1, using mathematical language to describe the parallel mid-body section and the contraction section of the vehicle, and obtaining the function expression of the parallel mid-body section cross-sectional profile and the rotating body generatrix; step 2, making a plane perpendicular to the rotation axis on the tail rotating body, taking the circle intercepted by the plane and the tail contraction section, and obtaining its mathematical expression; step 3, selecting any plane passing through the rotation axis, and using the curves intercepted by the plane and the parallel mid-body section and the rotating body as constraints, calculate the intersection expression of the transition section surface on the plane; step 4, using the transition section intersection expression obtained in step 3, using a function surface or a mesh surface to draw the transition section surface.

Description

Technical Field

[0001] The present invention belongs to the field of ship and ocean engineering, and specifically relates to related fields such as ship shape design. Background Art

[0002] The outer surface of an underwater vehicle is the basis for the design and construction of the vehicle. The vehicle surface determines its appearance, carrying performance, fluid performance, noise performance and other important properties. Therefore, it is particularly important to rationally design the surface of the underwater vehicle.

[0003] At present, the main body shape of traditional underwater vehicles is a spherical cylindrical cone or a teardrop-shaped rotating body that rotates along the length of the ship. The line shape of this type of rotating underwater vehicle is relatively simple, and a smooth shape can be obtained by rationally designing the generatrix of the vehicle's shape. In recent years, the research and development of underwater unmanned vehicles has gradually become a hot topic. Unmanned vehicles do not require personnel to operate on board, and the demand for pressure cabins on the boat is no longer like that of submarines, where a rotating pressure cabin is installed throughout the boat. At the same time, in order to facilitate the carrying of various types of loads, some load sections of underwater unmanned vehicles have gradually begun to adopt a flat shape instead of a cylindrical shape with an arc. These factors have led to the fact that the interface shape of the parallel mid-body section of the vehicle no longer uses a traditional rotating body. For example, the cross-sectional shape of the parallel mid-body section of the latest XLUUV Orca in the United States adopts a rounded square.

[0004] However, the change in the shape of the parallel mid-body section has brought new challenges to the underwater vehicle shape design: how to reasonably design the transition shape so that the parallel mid-body section of the non-rotating body can smoothly transition to the tail contraction section rotating body.

[0005] by Figure 1 For example, the model shown in the figure has a rounded square in the middle of the parallel body section and a rotating body in the tail contraction section. For this case, a simpler transition zone surface design scheme is to use a bridging surface to link the cross-sections of the two areas, such as Figure 2 As shown in FIG. 1 , although the existing bridging surface solution can ensure that the transition surface is tangent to the parallel outer surface of the middle body and the outer surface of the tail contraction section, the tail end model is cut by a plane at an angle of 45° to the horizontal plane, and the cross-sectional shape is as follows: Figure 3As shown in the figure, the curvature of the transition zone section on the cross section changes too dramatically, and some areas are concave along the axial section. When the fluid flows through the surface with a concave shape, the viscous pressure resistance caused by the transition zone surface will increase significantly. In addition, since the generation method of the bridge surface is automatically generated by the modeling software, the generation result of the surface is uncontrollable, and the actual shape of the transition curve will generate a non-unique surface with the change of the modeling software and modeling method. Finally, due to the uncontrollable factor of the shape of the transition surface, the existing design scheme cannot use the existing low-resistance linear design transition section surface. Summary of the invention

[0006] The present invention proposes a method for designing a variable-section transition section profile of an underwater vehicle, which can not only define the existing low-resistance line shape on the transition surface to ensure that the surface has better drag reduction performance, but also accurately give the function of the transition surface to ensure that the transition surface profile value is controllable everywhere.

[0007] The present invention is achieved through the following technical solutions.

[0008] A method for designing a variable cross-section transition section profile for an underwater vehicle comprises the following steps:

[0009] Step 1: Use mathematical language to describe the parallel mid-body section and the contraction section body of revolution of the spacecraft, and obtain the function expression of the cross-sectional profile of the parallel mid-body section and the generatrix of the body of revolution;

[0010] Step 2: Make a plane perpendicular to the rotation axis on the tail rotating body, take the circle intercepted by the plane and the tail contraction section, and obtain its mathematical expression;

[0011] Step 3, select any plane passing through the rotation axis, and use the curves intercepted by the plane and the parallel mid-body segment and the rotating body as constraint conditions to calculate the expression of the section line of the transition segment surface on the plane;

[0012] Step 4: Based on the transition segment cutoff line expression obtained in step 3, use a function surface or a mesh surface to draw the transition segment surface.

[0013] Beneficial effects of the present invention:

[0014] 1. The transition section curved surface designed by the present invention smoothly transitions between the parallel mid-body section and the tail contraction section, and the transition section curved surface has no concave line along the x-axis direction;

[0015] 2. The present invention accurately controls the mathematical expression of the transition section surface, which facilitates the parametric design of the aircraft transition section surface and realizes the rapid iterative design of the aircraft shape;

[0016] 3. The line type change of the transition section surface along the x direction is a geometric scaling of the line type of the tail contraction section, which not only facilitates the use of a low-resistance line type for the transition section, but also ensures that the line type of the transition section and the line type of the contraction section have a certain similarity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the parallel mid-body section and tail contraction section to be designed in the present invention;

[0018] Figure 2 It is the design result of the existing technology;

[0019] Figure 3 It is a schematic diagram of the transition section profile of a certain section of the prior art design result;

[0020] Figure 4 A flow chart of a method for designing a variable cross-section transition section profile for an underwater vehicle according to the present invention;

[0021] Figure 5 To take a schematic diagram of the tail contraction section after cutting perpendicular to the rotation axis, the surface of the cut area will be redesigned by the method proposed by the present invention;

[0022] Figure 6 A design method for smoothly transitioning from a parallel mid-body section to a tail contraction section section on a plane passing through the rotation axis;

[0023] Figure 7 The design results of the transition section profile on different rotation sections;

[0024] Figure 8 It is a schematic diagram of the result of the transition section line extending along the negative x-axis to the parallel mid-body section;

[0025] Fig. 9 The transition section surface designed by the method proposed in the present invention is a demonstration case. DETAILED DESCRIPTION

[0026] The exemplary embodiments of the present invention are described in detail below with reference to the accompanying drawings. It should be understood that the embodiments shown and described in the accompanying drawings are only exemplary and are intended to illustrate the principles and spirit of the present invention, rather than to limit the scope of the present invention.

[0027] like Figure 4 As shown, a method for designing a profile of a variable cross-section transition section of an underwater vehicle according to the present invention specifically comprises the following steps:

[0028] Step 1: Use mathematical language to describe the parallel mid-body section and the contraction section body of revolution of the spacecraft, and obtain the function expression of the cross-sectional profile of the parallel mid-body section and the generatrix of the body of revolution;

[0029] like Figure 1 As shown, in this embodiment, the function expression for obtaining the parallel mid-body section profile and the generatrix of the body of revolution is specifically performed by the following steps:

[0030] In this embodiment, the cross-sectional shape of the parallel middle body section is a rounded square with a side length of 2000 mm and a fillet radius of 500 mm; the tail contraction section is a body of revolution, the generatrix of the body of revolution is a cosine function, and the length of the contraction section is 3000 mm;

[0031] 1.1 First, establish a rectangular coordinate system, with the center point of the starting section of the tail contraction section as the origin; the rotation axis of the tail contraction section rotating body as the x-axis (that is, the length direction of the spacecraft is the x-axis), and the direction pointing to the stern is the positive direction of the x-axis; looking from the stern to the bow, the positive direction of the y-axis is the top of the spacecraft, and the positive direction of the z-axis is the port side of the spacecraft.

[0032] 1.2 Establishing the cylindrical coordinate system, the x-axis in the cylindrical coordinate system is consistent with the x-axis in the rectangular coordinate system. When θ = 0, the direction of the radial vector r is parallel to the y-axis. After the given coordinate system, the parallel midbody cross-section contour line r of the example model is obtained. 1 (θ) and the function r of the mother line of the tail contraction section 2 (x); In order to facilitate the subsequent transition zone profile design during specific implementation, the tangent line of the starting position of the contraction section busbar profile is parallel to the x-axis;

[0033] 1.3 Since the parallel midbody cross-section profile is in the yoz plane and is symmetrical about the y-axis and the z-axis, it is only necessary to give the function expression of the profile in the first quadrant. The equation of the curve is divided into three sections:

[0034]

[0035] Where y1 and z1 represent the horizontal and vertical coordinates of the cross-sectional profile of the parallel midbody segment projected on the yoz plane; φ is the radian value of the square corner, and there is a certain conversion relationship between the radian value and the cylindrical coordinate angle θ:

[0036] 1.4 Convert formula (1) into cylindrical coordinates, and the cross-sectional profile curve equation is expressed as

[0037]

[0038] 1.5 The generatrix expression of the tail contraction section is:

[0039]

[0040] 1.6 In NX10.0, the cross-sectional contour line of the parallel body segment is drawn on the x=0 plane using the regular curve drawing formula (2) or by directly drawing a rounded square sketch. The curve is stretched from x=0 to x=-4000 using the stretching operation to generate the parallel mid-body segment. The tail contraction segment generatrix defined by the regular curve drawing formula (3) is then rotated 360° around the x-axis using the rotation operation to generate the tail contraction segment.

[0041] Step 2: Draw a plane x=x perpendicular to the x-axis Q , take the circle intercepted by the plane and the tail contraction segment, the projection equation of the intercepted circle on the yoz plane is:

[0042] or r(θ)=r 2 (x Q ) (4)

[0043] In the specific implementation, in order to ensure that the final transition surface is smooth and has no abnormal protrusions, the section x=x Q It is necessary to ensure that the outline of the intercepted circle does not exceed the projection range of the parallel middle section outline on the yoz plane.

[0044] In this embodiment, the plane x=1000 mm is taken, and the equation of the curve intercepted by the intersection of the plane and the outer surface of the tail contraction section is:

[0045]

[0046] In NX, create a reference surface x=1000mm and use the "Trim Body" command to use the reference surface x=1000mm as a tool to remove the part of the rotation body where x<1000mm. The trimming result is as follows: Figure 5 As shown in Figure 5, the circular contour intercepted by the plane is the curve defined by formula (5).

[0047] Step 3: Select any plane passing through the rotation axis (x-axis) and convert it to obtain the equation of the intersection curve between the plane and the transition section; the details are as follows:

[0048] Take any plane passing through the x-axis, and its angle with the xoy plane is θ i , the plane intersects with the parallel section and the tail contraction section to obtain the corresponding interface contour line, such as Figure 6 As shown, the two cross-sectional contour lines are at θ = θ i The mathematical expressions on the plane are:

[0049] Parallel segment transversal: r(x) = r 1 (θ i ) (6)

[0050] Contraction section line: r(x) = r2 (x) (7)

[0051] In specific implementation, in order to make the parallel segment section smoothly transition to the contraction segment section, the tail contraction segment line type is scaled with point Q as the reference point, so that the left endpoint of the scaled curve is tangent to the parallel segment section, and the tangent point is P. The equation of the scaled curve is:

[0052]

[0053] On the scaled curve, select the curve segment between point P and Q as the transition zone line type;

[0054] It can be seen that in this design method, the transition line is tangent to the line of the first and tail sections at the same time, and its shape is similar to the line of the contraction section that has been designed for drag reduction. The transition section still has good drag reduction performance.

[0055] In this embodiment, a cross section θ=20° passing through the x-axis is selected. On the cross section, the radii of point P and point Q are respectively:

[0056]

[0057] The contraction curve is scaled about point Q. If the scaled curve needs to be tangent to the parallel midbody curve, the value of the magnification factor k is:

[0058]

[0059] Then the expression of the transition section intercept is:

[0060]

[0061] Using a rectangular coordinate system, the curve can be expressed as:

[0062]

[0063] In NX, the section line of the transition zone on the θ=20° section represented by formula (12) is drawn by "regular curve" or "artistic spline".

[0064] Step 4: according to the equation of the intersection curve between the plane and the transition section, draw the transition section surface using a function surface;

[0065] Furthermore, for modeling software that cannot create function surfaces, several planes passing through the rotation axis are drawn using lines, and the intersection lines between the planes and the transition surface are drawn on the planes according to formula (8), and finally the transition surface is established by meshing the surface.

[0066] like Figure 7As shown, in this embodiment, sections θ=0°, 5°, 10°, ..., 45° are selected, and the transition curve on each section is drawn using formula (8), and then the generated curve is radially oriented using the θ=45° plane to obtain the line type of 1 / 4 of the transition section of the spacecraft.

[0067] Theoretically, all the starting points of the transition section can be connected into a three-dimensional spline curve, and the cross-sectional profile of the curve and the tail contraction section at x = 1000mm is used as the "main curve", and the transition curve generated by the wall is used as the "cross curve". The transition area surface is generated by the "through curve mesh" command in NX. However, since the surface is tangent to the parallel mid-body segment, the transition surface cannot be used to "trim" the redundant entities of the parallel mid-body segment.

[0068] Therefore, this embodiment first uses the plane of x = -1600mm and uses the "trim body" command to remove the part of the parallel middle body segment x>-1600mm. On this basis, each transition curve is extended along the negative x axis until it intersects with the parallel middle body contour intercepted by the plane of x = -1600mm, and the extended curve is obtained as follows: Figure 8 As shown. After extending the transition section curve, the transition section curve is drawn into a transition surface by using the curve mesh command, and the surface of the first quadrant is symmetrical to the four quadrants by using the mirror feature command, and then the curves of the first and tail end faces of the transition section are sealed into a surface domain by using the bounded plane command, and then the transition surface and the bounded plane are stitched into a transition section entity by using the stitch command, and finally the parallel mid-body section, transition section, and tail contraction section are merged by using the merge command to form the tail shape of the aircraft; as shown Fig. 9 shown.

[0069] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0070] It is obvious to those skilled in the art that the embodiments of the present invention are not limited to the details of the above exemplary embodiments, and that the embodiments of the present invention can be implemented in other specific forms without departing from the spirit or basic features of the embodiments of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the embodiments of the present invention is limited by the attached claims rather than the above description, so it is intended to include all changes that fall within the meaning and scope of the equivalent elements of the claims in the embodiments of the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved. In addition, it is obvious that the word "comprising" does not exclude other units or steps, and the singular does not exclude the plural. Multiple units, modules or devices stated in the system, device or terminal claims can also be implemented by the same unit, module or device through software or hardware. The words first, second, etc. are used to indicate names, and do not indicate any particular order.

[0071] Finally, it should be noted that the above implementation modes are only used to illustrate the technical solutions of the embodiments of the present invention and are not intended to limit them. Although the embodiments of the present invention have been described in detail with reference to the above preferred implementation modes, those skilled in the art should understand that the technical solutions of the embodiments of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for designing a variable cross-section transition section profile for an underwater vehicle, characterized in that: The following steps are involved: Step 1: Use mathematical language to describe the parallel mid-body section and the contraction section body of revolution of the spacecraft, and obtain the function expression of the cross-sectional profile of the parallel mid-body section and the generatrix of the body of revolution; Step 2: Make a plane perpendicular to the rotation axis on the tail rotating body, take the circle intercepted by the plane and the tail contraction section, and obtain its mathematical expression; Step 3, select any plane passing through the rotation axis, and use the curves intercepted by the plane and the parallel mid-body segment and the rotating body as constraint conditions to calculate the expression of the section line of the transition segment surface on the plane; Step 4: Based on the transition segment cutoff line expression obtained in step 3, use a function surface or a mesh surface to draw the transition segment surface.

2. A method for designing a variable cross-section transition section profile for an underwater vehicle as claimed in claim 1, characterized in that: The function expression for obtaining the parallel mid-body section profile and the generatrix of the body of revolution is specifically obtained by the following steps: 1.1 First, establish a rectangular coordinate system, with the center point of the starting section of the tail contraction section as the origin; the rotation axis of the tail contraction section rotation body as the x-axis, and the direction pointing to the stern as the positive direction of the x-axis; looking from the stern to the bow, the positive direction of the y-axis is directly above the spacecraft, and the positive direction of the z-axis is the port side of the spacecraft; 1.2 Establish a cylindrical coordinate system of xr-θ. The x-axis in the cylindrical coordinate system is consistent with the x-axis in the rectangular coordinate system. When θ=0, the direction of the radial vector r is parallel to the y-axis. After the given coordinate system, the function r2(x) of the parallel midbody cross-section contour line r1(θ) and the generatrix of the tail contraction section of the example model is obtained respectively; 1.3 Among them, the cross section of the parallel midbody segment is a rounded square. Since the cross-sectional profile of the parallel midbody segment is in the yoz plane and is symmetrical about the y-axis and the z-axis, it is only necessary to give the function expression of the contour line in the first quadrant. The equation of the curve is divided into three sections: Where y1 and z1 represent the horizontal and vertical coordinates of the cross-sectional profile of the parallel midbody segment projected on the yoz plane; φ is the radian value of the square corner, and there is a certain conversion relationship between the radian value and the cylindrical coordinate angle θ: 1.4 Convert formula (1) into cylindrical coordinates, and the cross-sectional profile curve equation is expressed as 1.5 The generatrix of the rotating body of the tail contraction section is a sine function, and its expression is: 1.6 In NX10.0, use the regular curve drawing formula (2) or directly draw a rounded square sketch to draw the cross-sectional contour line of the parallel body segment on the x=0 plane, and use the stretching operation to stretch the curve from x=0 to x=-4000 to generate the parallel mid-body segment; then use the regular curve drawing formula (3) to define the tail contraction segment generatrix, and use the rotation operation to rotate the generatrix 360° around the x-axis to generate the tail contraction segment.

3. A method for designing a variable cross-section transition section profile for an underwater vehicle as claimed in claim 1 or 2, characterized in that: In step 2, to ensure that the final transition surface is smooth and has no abnormal protrusions, select section x = x Q It is necessary to ensure that the outline of the intercepted circle does not exceed the projection range of the parallel middle section outline on the yoz plane.

4. A method for designing a variable cross-section transition section profile for an underwater vehicle as claimed in claim 1 or 2, characterized in that: Step 3 is as follows: 4.1 Take any plane passing through the x-axis, and its angle with the xoy plane is θ i The plane intersects with the parallel section and the tail contraction section to obtain the corresponding interface contour line. The two cross-sectional contour lines are at θ = θ i The mathematical expressions on the plane are: Parallel segment section: r(x)=r1(θ i ) (6) Contraction section line: r(x) = r2(x) (7) 4.2 In order to make the parallel segment section smoothly transition to the contraction segment section, the tail contraction segment line type is scaled with point Q as the reference point, so that the left endpoint of the scaled curve is tangent to the parallel segment section, and the tangent point is P. The equation of the scaled curve is: On the scaled curve, select the curve segment within the range of point P and Q as the transition zone line type.

5. A method for designing a variable cross-section transition section profile for an underwater vehicle as claimed in claim 4, characterized in that: In step 4, according to the expression given by formula (8), the transition segment surface is directly drawn using the function surface command; for modeling software that cannot create function surfaces, several planes passing through the rotation axis are drawn using lines, and the intersection line between the plane and the transition segment surface is drawn on the plane according to formula (8), and finally the transition segment surface is established by meshing the surface.

Images