A method for calculating fluid-structure coupling of a water-entry vehicle based on motion decoupling

Abstract

The application provides a method for calculating fluid-structure coupling of a water-entry vehicle based on motion decoupling, which comprises the following steps: obtaining water-entry parameters of the vehicle; decoupling the motion of the vehicle when entering water into vertical falling of the vehicle and horizontal flow of the flow field, and determining the vertical falling speed of the vehicle and the horizontal flow speed of the flow field according to the water-entry parameters; determining the envelope size of a whole cuboid water area, the partition parameters of the whole cuboid water area and the envelope size of a water-contacting encryption area according to the water-entry parameters, the water-contacting encryption area being contained in the whole cuboid water area; establishing a water area finite element model according to the envelope size of the whole cuboid water area and the envelope size of the water-contacting encryption area; and performing fluid-structure coupling calculation based on the water area finite element model according to the vertical falling speed of the vehicle and the horizontal flow speed of the flow field. The technical scheme of the application is used to solve the technical problem that the analysis precision and the calculation efficiency of fluid-structure coupling are contradictory in the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fluid-structure coupling analysis, and particularly relates to a method for calculating fluid-structure coupling of a water-entry vehicle based on motion decoupling. BACKGROUND

[0002] When a vehicle enters water, a high-level short-pulse impact fluid power is generated, which may cause severe fluid-structure coupling effect, bring about dynamic strength, dynamic response amplification and flow field characteristic change and many other problems. When the finite element method is used to analyze the impact process of the water-entry vehicle, the grid quality of the fluid-structure coupling region is a key factor affecting the accuracy of the fluid-structure coupling analysis, and the grid size and scale of the water region are the primary factors affecting the calculation efficiency. For the water-entry problem, the region where the vehicle enters water is often several meters or even tens of meters long, which poses great challenges to the modeling of the water region, and it is difficult to balance the analysis accuracy and the calculation efficiency. SUMMARY

[0003] The present application provides a method for calculating fluid-structure coupling of a water-entry vehicle based on motion decoupling, which can solve the technical problem of the contradiction between the analysis accuracy and the calculation efficiency of the fluid-structure coupling in the prior art.

[0004] According to an aspect of the present application, a method for calculating fluid-structure coupling of a water-entry vehicle based on motion decoupling is provided, and the method comprises the following steps:

[0005] Obtaining water-entry parameters of the vehicle, the water-entry parameters comprising the full length of the vehicle, the diameter of the vehicle, the water-entry speed of the vehicle, the water-entry angle of the vehicle, the water-entry duration of the vehicle, the head length of the vehicle and the minimum diameter of the head of the vehicle;

[0006] Decoupling the motion of the vehicle when entering water into vertical falling of the vehicle and horizontal flow of the flow field, and determining the vertical falling speed of the vehicle and the horizontal flow speed of the flow field according to the water-entry parameters;

[0007] Determining the envelope size of the overall cuboid water region, the partition parameters of the overall cuboid water region and the envelope size of the water-contacting densification region according to the water-entry parameters, the water-contacting densification region being contained in the overall cuboid water region;

[0008] Establishing a water region finite element model according to the envelope size of the overall cuboid water region and the envelope size of the water-contacting densification region;

[0009] Performing fluid-structure coupling calculation based on the water region finite element model according to the vertical falling speed of the vehicle and the horizontal flow speed of the flow field.

[0010] Further, determining the vertical falling speed of the vehicle and the horizontal flow speed of the flow field according to the water-entry parameters comprises determining the vertical falling speed of the vehicle and the horizontal flow speed of the flow field according to the water-entry speed of the vehicle and the water-entry angle of the vehicle.

[0011] Further, the vertical falling speed of the vehicle and the horizontal flow speed of the flow field are determined according to the water entry speed of the vehicle and the water entry angle of the vehicle by the following formula:

[0012] V d = V sin θ,

[0013] V w = V cos θ,

[0014] In the above formula, V d represents the vertical falling speed of the vehicle, V w represents the horizontal flow speed of the flow field, V represents the water entry speed of the vehicle, and θ represents the water entry angle of the vehicle.

[0015] Further, the envelope size of the overall cuboid water area, the partition parameter of the overall cuboid water area, and the envelope size of the water contact encryption region are determined according to the water entry parameters, which include:

[0016] The envelope size of the overall cuboid water area is determined according to the overall length of the vehicle, the diameter of the vehicle, the water entry speed of the vehicle, the water entry angle of the vehicle, and the water entry duration of the vehicle;

[0017] The envelope size of the water contact encryption region is determined according to the head length of the vehicle, the minimum diameter of the head of the vehicle, the water entry angle of the vehicle, and the envelope size of the overall cuboid water area;

[0018] The overall cuboid water area is divided into a water contact front section, a water contact middle section, and a water contact rear section along the length direction, the water contact encryption region is contained in the water contact middle section, and the partition parameters of the water contact front section, the water contact middle section, and the water contact rear section are determined according to the envelope size of the water contact encryption region.

[0019] Further, the envelope size of the overall cuboid water area satisfies the following conditions:

[0020] L s ≥ 2L,

[0021] D s ≥ 5d,

[0022] H s > V sin θt,

[0023] In the above formula, L s represents the length of the overall cuboid water area, D s represents the width of the overall cuboid water area, H s represents the height of the overall cuboid water area, L represents the overall length of the vehicle, d represents the diameter of the vehicle, and t represents the water entry duration of the vehicle.

[0024] Further, the envelope size of the water contact encryption region satisfies the following conditions:

[0025] D m = max(L h sinθ,d h ),

[0026] H m = H s ,

[0027] In the above formula, D m represents the diameter of the water contact encryption area, H m represents the height of the water contact encryption area, L h represents the length of the head of the vehicle, and d h represents the minimum diameter of the head of the vehicle.

[0028] Further, the partition parameters of the water contact front section, the water contact middle section, and the water contact rear section satisfy the following conditions:

[0029] L2 = D m ,

[0030] L1 > 2L2,

[0031] L3 > 4L2,

[0032] In the above formula, L1 represents the length of the water contact front section, L2 represents the length of the water contact middle section, and L3 represents the length of the water contact rear section.

[0033] Further, the establishment of the water area finite element model according to the envelope size of the overall cuboid water area and the envelope size of the water contact encryption area comprises:

[0034] The water contact encryption area is divided into finite element grids according to the coin type topology structure, and the size ratio of the maximum grid to the minimum grid in the water contact encryption area is less than or equal to a first threshold value;

[0035] The water contact encryption area is divided into finite element grids according to the radial type topology structure to obtain a transition area, the length of the long side to the length of the short side of the grid in the transition area is less than or equal to a second threshold value;

[0036] The other areas on both sides of the transition area are divided into finite element grids, and the size ratio of two adjacent grids in the length direction of the overall cuboid water area is less than or equal to a third threshold value.

[0037] Further, the value of the first threshold value is 2, the value of the second threshold value is 1.3, and the value of the third threshold value is 1.5.

[0038] Further, the fluid-structure coupling calculation based on the water area finite element model according to the vertical falling speed of the vehicle and the horizontal flow speed of the flow field comprises:

[0039] Taking the vertical falling velocity of the sailing body as the initial velocity of the sailing body;

[0040] Taking the horizontal flow velocity of the flow field as the water area inlet velocity boundary;

[0041] Based on the water area finite element model, the fluid-structure coupling calculation is carried out according to the initial velocity of the sailing body and the water area inlet velocity boundary.

[0042] The technical scheme of the application provides a sailing body water entry fluid-structure coupling calculation method based on motion decoupling, which can simplify the complexity of the initial condition and boundary condition processing in the water entry fluid-structure coupling analysis by equivalently decoupling the motion of the sailing body into the vertical falling velocity of the sailing body and the horizontal flow velocity of the flow field, and significantly reduce the size and scale of the fluid-structure coupling contact area grid. In addition, by means of local grid encryption design, the flow field solving degree of freedom can be further reduced on the basis of small water area volume, and the fluid-structure coupling analysis calculation efficiency is greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0043] The accompanying drawings included to provide a further understanding of the embodiments of the application and constitute a part of the specification, which serve to explain the principles of the application together with the text. Obviously, the drawings in the following description only show some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0044] Figure 1 A flowchart of the sailing body water entry fluid-structure coupling calculation method based on motion decoupling provided by the specific embodiment of the application is shown;

[0045] Figure 2 A sailing body water entry state diagram provided by the specific embodiment of the application is shown;

[0046] Figure 3 A motion decoupling principle diagram provided by the specific embodiment of the application is shown;

[0047] Figure 4 An envelope size diagram of the overall cuboid water area and the water contact encryption area provided by the specific embodiment of the application is shown;

[0048] Figure 5 A partition parameter diagram of the overall cuboid water area provided by the specific embodiment of the application is shown;

[0049] Figure 6 A finite element model area division diagram provided by the specific embodiment of the application is shown;

[0050] Figure 7A model schematic diagram obtained by performing finite element meshing on the water-contacting encryption region according to a coin-type topology structure is shown;

[0051] Figure 8 A model schematic diagram obtained by performing finite element meshing on the four-prism transition region according to a radiation-type topology structure is shown;

[0052] Figure 9 A finite element mesh model schematic diagram of the water-contacting encryption region and the four-prism transition region is shown;

[0053] Figure 10 A three-dimensional finite element mesh model schematic diagram of the overall cuboid water area is shown. DETAILED DESCRIPTION

[0054] It should be noted that the embodiments and features of the embodiments in the present application can be combined with each other without conflict. The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. The description of the at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0055] It should be noted that the terms used herein are only intended to describe specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and it should also be understood that when the terms "comprise" and / or "include" are used in the specification, there is a presence of the features, steps, operations, devices, components and / or combinations thereof.

[0056] The foregoing is considered as illustrative only of the principles of the application. Other variations and modifications are possible in light of the above teachings. Therefore, the scope of the matter disclosed should not be limited to the certain embodiments and drawings described but can be identified by the scope of the claims and their equivalents. Unless otherwise stated, the relative arrangement of components and steps, numerical expressions, and numerical values set forth in the examples shown herein are not limiting the scope of the application. Also, it is to be understood that the dimensions of the various portions shown in the drawings are not necessarily to scale. Techniques, methods, and devices known to those of ordinary skill in the relevant art can not be discussed in detail but can be assumed by those skilled in the art to be within the scope of the present teachings. In the examples shown and discussed herein, any specific values should be interpreted as merely illustrative and not as a limitation of the scope of the exemplary embodiments. Thus, other examples of the exemplary embodiments can have different values. It is to be noted that like numbers and letters refer to like elements throughout the several views of the drawings and that, as typically an item defined in one drawing need not be discussed further in subsequent drawings.

[0057] As Figure 1 shown, according to a specific embodiment of the present application, a method for calculating the fluid-structure interaction of a water-entry vehicle based on motion decoupling is provided, the method comprising: obtaining water-entry parameters of the vehicle, the water-entry parameters including the overall length of the vehicle, the diameter of the vehicle, the water-entry speed of the vehicle, the water-entry angle of the vehicle, the water-entry duration of the vehicle, the head length of the vehicle, and the minimum diameter of the head of the vehicle; decoupling the motion of the vehicle when entering water into the vertical falling of the vehicle and the horizontal flow of the flow field, and determining the vertical falling speed of the vehicle and the horizontal flow speed of the flow field according to the water-entry parameters; determining the envelope size of the overall cuboid water area, the partition parameters of the overall cuboid water area, and the envelope size of the water-contacting encryption area according to the water-entry parameters, the water-contacting encryption area being contained in the overall cuboid water area; establishing a water area finite element model according to the envelope size of the overall cuboid water area and the envelope size of the water-contacting encryption area; and performing fluid-structure interaction calculation based on the water area finite element model according to the vertical falling speed of the vehicle and the horizontal flow speed of the flow field.

[0058] Please refer to Figure 2 Embodiments, the vehicle includes a front-end conical section and a rear-end cylindrical section, the diameter of the vehicle refers to the diameter of the cylindrical section, the head diameter of the vehicle refers to the diameter of the front-end of the conical section, the water-entry angle of the vehicle refers to the angle with the water surface when entering water, and the water-entry duration of the vehicle refers to the duration from the water-contacting of the vehicle to the full water-entry of the vehicle.

[0059] By using the configuration method, a motion decoupling-based water-entry fluid-structure coupling calculation method of a navigation body is provided, which equivalently decouples the motion of the navigation body into a vertical falling speed of the navigation body and a horizontal flow speed of a flow field, and significantly reduces the complexity of processing initial conditions and boundary conditions in water-entry fluid-structure coupling analysis, and simultaneously significantly reduces the scale and size of a grid in a fluid-structure coupling contact area. In addition, by using a local grid encryption design, the flow field calculation freedom can be further reduced on the basis of a small water volume, and the fluid-structure coupling analysis calculation efficiency is greatly improved. Compared with the prior art, the technical scheme of the present application can solve the technical problem that the accuracy and calculation efficiency of fluid-structure coupling analysis are contradictory in the prior art.

[0060] As shown in Figure 2 and Figure 3 , in the embodiment of the present application, the equivalent decoupling of the motion of the navigation body refers to decoupling the navigation body in the parallel water surface direction and the vertical water surface direction, and decoupling the motion of the navigation body when entering the water into the vertical falling of the navigation body and the horizontal flow of the flow field according to the speed and the trajectory inclination angle when entering the water, that is, determining the vertical falling speed of the navigation body and the horizontal flow speed of the flow field according to the water-entry parameters includes determining the vertical falling speed of the navigation body and the horizontal flow speed of the flow field according to the water-entry speed of the navigation body and the water-entry angle of the navigation body. Specifically, as a specific embodiment of the present application, the vertical falling speed of the navigation body and the horizontal flow speed of the flow field are determined according to the water-entry speed of the navigation body and the water-entry angle of the navigation body by the following formula:

[0061] V d = V sin θ,

[0062] V w = V cos θ,

[0063] In the above formula, V d represents the vertical falling speed of the navigation body, V w represents the horizontal flow speed of the flow field, V represents the water-entry speed of the navigation body, and θ represents the water-entry angle of the navigation body.

[0064] In which, the vertical falling speed of the navigation body is used as the initial speed of the navigation body in the coupling analysis, and the horizontal flow speed of the flow field is used as the water area inlet speed boundary in the coupling analysis, and by using the equivalent decoupling method, the complexity of processing initial conditions and boundary conditions in water-entry fluid-structure coupling analysis can be greatly reduced.

[0065] Furthermore, in this embodiment of the invention, determining the envelope size of the overall cuboid water area, the partitioning parameters of the overall cuboid water area, and the envelope size of the water-contact reinforcement zone based on the water entry parameters includes: determining the envelope size of the overall cuboid water area based on the total length of the vehicle, the diameter of the vehicle, the vehicle's water entry speed, the vehicle's water entry angle, and the vehicle's water entry time; determining the envelope size of the water-contact reinforcement zone based on the length of the vehicle's head, the minimum diameter of the vehicle's head, the vehicle's water entry angle, and the envelope size of the overall cuboid water area; dividing the overall cuboid water area along its length into three partitions: the front water-contact section, the middle water-contact section, and the rear water-contact section, with the water-contact reinforcement zone contained within the middle water-contact section; and determining the partitioning parameters of the front water-contact section, the middle water-contact section, and the rear water-contact section based on the envelope size of the water-contact reinforcement zone.

[0066] Specifically, the envelope size of the overall rectangular water body is as follows: Figure 4 As shown, in a specific embodiment of the present invention, the envelope size of the overall cuboid water area satisfies the following conditions:

[0067] L s ≥2L,

[0068] D s ≥5d,

[0069] H s >V sinθt,

[0070] In the above formula, L s D represents the length of the entire rectangular body of water. s H represents the width of the entire rectangular body of water. s The height of the rectangular body of water is represented by L, the total length of the vehicle is represented by d, the diameter of the vehicle is represented by d, and the time it takes for the vehicle to enter the water is represented by t.

[0071] Furthermore, the envelope size of the water-contact encrypted area is as follows: Figure 4 As shown, in a specific embodiment of the present invention, the envelope size of the water-contact encryption region satisfies the following conditions:

[0072] D m =max(L h sinθ,d h ),

[0073] H m =H s ,

[0074] In the above formula, D m H represents the diameter of the water-contact encrypted area. m L represents the height of the water-contact encrypted area. h d represents the length of the bow of the aircraft carrier. h This indicates the minimum diameter of the bow of the aircraft carrier.

[0075] In addition, the partition of the overall cuboid water area is as shown in Figure 5 The overall cuboid water area is divided into three sections, i.e., a pre-touch water section, a mid-touch water section, and a post-touch water section. As a specific embodiment of the present application, the partition parameters of the pre-touch water section, the mid-touch water section, and the post-touch water section satisfy the following conditions:

[0076] L2=D m ,

[0077] L1>2L2,

[0078] L3>4L2,

[0079] In the above formula, L1 represents the length of the pre-touch water section, L2 represents the length of the mid-touch water section, and L3 represents the length of the post-touch water section.

[0080] Further, as shown in Figure 6 , the overall cuboid water area is divided into three types of modeling areas from the perspective of grid division. As viewed from the top view, the overall rectangle includes a circular encryption area, which is the location of the touch water encryption area. A square transition area is arranged around the circular encryption area, and the areas on both sides of the square transition area together constitute a non-encryption area. Specifically, the establishment of the water area finite element model according to the envelope size of the overall cuboid water area and the envelope size of the touch water encryption area includes: performing finite element grid division on the touch water encryption area according to the coin type topology structure, and the size ratio of the largest grid to the smallest grid in the touch water encryption area (fluid-solid grid ratio) is less than or equal to a first threshold value; performing finite element grid division on the transition area according to the radial type topology structure to obtain the transition area, the bottom side length of the transition area is equal to the width of the overall cuboid water area, and the length-to-short side ratio of the grid in the transition area (cross-section transition grid ratio) is less than or equal to a second threshold value; and performing finite element grid division on other areas on both sides of the transition area, and the size ratio of two adjacent grids in the length direction of the overall cuboid water area (adjacent transition grid ratio) is less than or equal to a third threshold value. The top view of the finite element model of the touch water encryption area is as shown in Figure 7 , the top view of the finite element model of the transition area is as shown in Figure 8 , the transition area is arranged around the touch water encryption area, and the top view of the finite element model formed by the combination of the two is as shown in Figure 9 . In addition, the values of the first threshold value, the second threshold value, and the third threshold value are determined according to the actual situation. As a specific embodiment of the present application, the value of the first threshold value is 2, the value of the second threshold value is 1.3, and the value of the third threshold value is 1.5. The three-dimensional finite element model constructed is as shown in Figure 10 . Through local encryption grid, the flow field calculation freedom degree is further reduced on the basis of small water volume, and the fluid-solid coupling analysis and calculation efficiency is greatly improved.

[0081] Further, in the embodiment of the present application, the fluid-structure coupling calculation based on the water area finite element model according to the vertical falling speed of the navigation body and the horizontal flow speed of the flow field comprises: taking the vertical falling speed of the navigation body as the initial speed of the navigation body; taking the horizontal flow speed of the flow field as the water area inlet speed boundary; and performing the fluid-structure coupling calculation based on the water area finite element model according to the initial speed of the navigation body and the water area inlet speed boundary. The finite element modeling software can adopt Abaqus. Through the motion relationship decoupling and the water area boundary condition setting, the volume of the fluid-structure coupling contact area grid can be greatly reduced, and the problem of too large water area modeling size in the traditional analysis method is solved.

[0082] In order to more clearly understand the fluid-structure coupling calculation method provided by the present application, the above processes will be described in detail below with actual application examples. It should be understood by those skilled in the art that the examples are only for the purpose of more clearly understanding the fluid-structure coupling calculation method provided by the present application, and do not limit the technical scope of the present application.

[0083] Step 1: decoupling the navigation body-water area for the navigation body water entry process, the water entry speed is 100 m / s, the water entry angle is 20 degrees, the water flow speed is 93.96 m / s, and the navigation body vertical speed is 34.2 m / s;

[0084] Step 2: determining the overall water area size and the water contact encryption area size according to the water entry design parameters, the overall length of the navigation body L = 5 m, the diameter of the navigation body d = 0.3 m, the water entry speed V = 100 m / s, the trajectory inclination angle θ = 20°, the water entry time t = 0.005 s, the length of the navigation body head L h = 0.05 m and the diameter d h = 0.06 m. The water area size is 10 m1×5 m×0.2 m, the water contact encryption area size is D m = 0.06 m, and H m = 0.2 m.

[0085] Step 3: dividing the overall water area into a water contact front section, a water contact middle section and a water contact rear section along the length direction, the lengths are L1 = 0.24 m, L2 = 0.06 m and L3 = 9.7 m respectively; the inner circle encryption area diameter is 0.06 m, and the square transition area size is 1.5 m.

[0086] Step 4: establishing the navigation body-water area finite element grid according to the above conditions, setting the water boundary condition and the navigation body initial speed condition on the rectangular water area end face according to the speed in Step 1, and submitting the calculation.

[0087] In summary, the application provides a kind of based on motion decoupling's water entry fluid-structure coupling calculation method of vehicle, the method is by the motion of vehicle equivalent decoupling as the vertical drop speed of vehicle and the initial condition and boundary condition processing complexity in the horizontal flow velocity of water entry fluid-structure coupling analysis of flow field, while significantly reducing the scale and scale of fluid-structure coupling contact area grid, in addition, by local encryption grid design, it can further reduce the degree of freedom of flow field solution based on small water volume, greatly improve the efficiency of fluid-structure coupling analysis calculation.Compared with prior art, the technical scheme of the application can solve the technical problem that the accuracy and calculation efficiency of fluid-structure coupling analysis are contradictory in the prior art.

[0088] For the convenience of description, spatial relative terms such as "above", "upper", "on", "top", etc. can be used herein to describe the spatial relationship of one device or feature to another device or feature as shown in the drawings. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation of the device described in the drawings. For example, if the device in the drawing is inverted, the device described as "above" or "on" other devices or structures will be positioned "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below" orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein are interpreted accordingly.

[0089] In addition, it should be noted that the use of the words "first", "second", and the like to describe various components is merely intended to facilitate the description of the corresponding components, and unless otherwise stated, the above words have no special meaning, and therefore cannot be understood as limiting the scope of protection of the present application.

[0090] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for computing fluid-structure interaction of a re-entry vehicle based on motion decoupling, characterized in that, The method comprises: obtaining the water entry parameters of the vehicle, the water entry parameters comprising the vehicle overall length, the vehicle diameter, the vehicle water entry speed, the vehicle water entry angle, the vehicle water entry duration, the vehicle head length and the vehicle head minimum diameter; equivalent decoupling the motion of the vehicle when entering the water into the vertical falling of the vehicle and the horizontal flow of the flow field, and determining the vertical falling speed of the vehicle and the horizontal flow speed of the flow field according to the water entry parameters; determining the envelope size of the overall cuboid water area, the partition parameters of the overall cuboid water area and the envelope size of the water contact encryption area according to the water entry parameters, the water contact encryption area being contained in the overall cuboid water area; establishing a water area finite element model according to the envelope size of the overall cuboid water area and the envelope size of the water contact encryption area, comprising: carrying out finite element mesh division on the water contact encryption area in a copper coin type topology structure, the size ratio of the maximum mesh to the minimum mesh in the water contact encryption area being less than or equal to a first threshold value; carrying out finite element mesh division in a radial type topology structure with the water contact encryption area as the center to obtain a transition area, the bottom side length of the transition area being equal to the width of the overall cuboid water area, the length to width ratio of the mesh in the transition area being less than or equal to a second threshold value; carrying out finite element mesh division on other areas on both sides of the transition area, and the size ratio of two adjacent meshes in the length direction of the overall cuboid water area being less than or equal to a third threshold value; performing fluid-solid coupling calculation based on the water area finite element model according to the vertical falling speed of the vehicle and the horizontal flow speed of the flow field, comprising: taking the vertical falling speed of the vehicle as the initial speed of the vehicle; taking the horizontal flow speed of the flow field as the water area inlet speed boundary; performing fluid-solid coupling calculation based on the water area finite element model according to the initial speed of the vehicle and the water area inlet speed boundary.

2. The method of claim 1, wherein, Determining the vertical falling speed of the vehicle and the horizontal flow speed of the flow field according to the water entry parameters comprises: determining the vertical falling speed of the vehicle and the horizontal flow speed of the flow field according to the vehicle water entry speed and the vehicle water entry angle.

3. The method of claim 2, wherein, The vertical falling speed of the vehicle and the horizontal flow speed of the flow field are determined according to the vehicle water entry speed and the vehicle water entry angle by the following formula: V d = V sin θ, V w = V cos θ, In the above formula, V d represents the vertical falling velocity of the vehicle, V w represents the horizontal flow velocity of the flow field, V represents the water entry velocity of the vehicle, and θ represents the water entry angle of the vehicle.

4. The method of claim 3, wherein, Determining the envelope size of the overall cuboid water area, the partition parameters of the overall cuboid water area and the envelope size of the water contact encryption area according to the water entry parameters comprises: determining the envelope size of the overall cuboid water area according to the vehicle overall length, the vehicle diameter, the vehicle water entry speed, the vehicle water entry angle and the vehicle water entry duration; determining the envelope size of the water contact encryption area according to the vehicle head length, the vehicle head minimum diameter, the vehicle water entry angle and the envelope size of the overall cuboid water area; The whole cuboid water area is divided into a pre-contact water section, a middle contact water section and a post-contact water section along the length direction, the contact water encryption region is contained in the middle contact water section, and the partition parameters of the pre-contact water section, the middle contact water section and the post-contact water section are determined according to the envelope size of the contact water encryption region.

5. The method of claim 4, wherein, The envelope size of the whole cuboid water area satisfies the following condition: L s ≥2L, D s ≥5d, H s > Vsinθt, In the above formula, L s represents the length of the overall cuboid water area, D s represents the width of the overall cuboid water area, H s represents the height of the overall cuboid water area, L represents the overall length of the vehicle, d represents the diameter of the vehicle, and t represents the length of time when the vehicle enters the water.

6. The method of claim 5, wherein, The envelope size of the contact water encryption region satisfies the following condition: D m = max(L h sinθ,d h ), H m = H s , In the above formula, D m represents the diameter of the water-contacting encrypted region, H m represents the height of the water-contacting encrypted region, L h represents the length of the head of the navigation body, d h represents the minimum diameter of the head of the navigation body.

7. The method of claim 6, wherein, The partition parameters of the pre-contact water section, the middle contact water section and the post-contact water section satisfy the following condition: L2 = D m , L1>2L2, L3>4L2, In the above formula, L1 represents the length of the pre-contact water section, L2 represents the length of the middle contact water section, and L3 represents the length of the post-contact water section.

8. The method of claim 7, wherein, The first threshold value is 2, the second threshold value is 1.3, and the third threshold value is 1.5.

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