A numerical simulation method for bidirectional fluid-structure coupling in UAV recovery

Abstract

The present invention belongs to the field of aerospace technology, and relates to a numerical simulation method for bidirectional fluid-solid coupling of unmanned aerial vehicle recovery, comprising the following steps: dividing a simulation object into different calculation areas to obtain an external flow field calculation domain and a solid calculation domain; meshing the solid calculation domain to obtain a solid calculation grid; meshing the external flow field calculation domain to construct an overlapping grid after interpolation; calculating the overlapping grid after interpolation to obtain flow field data; calculating the solid calculation grid to obtain solid deformation data; outputting the coupling result of the flow field data and the solid deformation data by means of fluid-solid bidirectional coupling; taking the unmanned aerial vehicle recovery time T0 as a judgment condition, if the fluid-solid coupling simulation time T<T0, the external flow field calculation domain grid performs grid torsion deformation and local grid regeneration according to the grid deformation threshold, and the solid geometry domain grid performs grid reconstruction; if T≥T0, the calculation result is output, and different applicable material properties of the simulation object are changed.

Description

Technical Field

[0001] The invention belongs to the field of aerospace technology, and in particular relates to a numerical simulation method for bidirectional fluid-solid coupling of unmanned aerial vehicle recovery. Background Art

[0002] Drone recovery technology has a high application prospect in the military field. In recent years, the U.S. Defense Advanced Research Projects Agency (DARPA) has launched a series of drone recovery test flights, of which nine attempts to recover three Gremlins drones have all failed. Drone recovery technology is the most important part. In future operations, the combination of large manned aircraft and small drones will give full play to the performance of drones. By dropping drones outside the enemy's defense zone and recovering them after performing corresponding combat missions, the combat distance and reaction time of drones are effectively improved with the help of the longer hovering time and range of the carrier aircraft. In the air above hot spots, the enemy can be pressured by continuously sending drones, and the "sea of ​​drones" tactics can be used to cover the combat of manned aircraft.

[0003] However, during the recovery process, the towing docking device, the carrier aircraft wake and the UAV will interact with each other. In order to make all components work together and increase the chance of successful docking, a complete numerical simulation method is needed to analyze the motion changes of the entire docking process. In existing technologies, most of them are fluid-solid coupling of a single simple model. When there are combined effects such as the carrier aircraft wake and flexible rope towing, the recovery process of UAVs with complex surfaces is difficult to achieve.

[0004] The patent "CN109783978A-A method for numerical simulation of aerodynamics of micro flapping-wing aircraft based on ANSYS workbench" describes the use of ANSYS workbench software to realize fluid-solid coupling simulation of a simple flapping-wing model. The method is only applicable to simple models. It is difficult to simulate complex processes of rigid-flexible coupling of multiple models, and the adaptability to complex curved surface meshes is also poor. Summary of the invention

[0005] The purpose of the present invention is to provide a numerical simulation method for bidirectional fluid-solid coupling of UAV recovery, propose a complete rigid-flexible coupling calculation process for multiple complex surface models, and solve the problem that the rigid-flexible coupling of multiple models is difficult to calculate and the calculation efficiency is low.

[0006] The present invention is achieved through the following technical solutions:

[0007] A numerical simulation method for bidirectional fluid-solid coupling of UAV recovery includes the following steps:

[0008] Step 1, select the carrier, flexible rope and UAV model as simulation objects;

[0009] Step 2: Divide the simulation object into different calculation areas through geometric processing to obtain the external flow field calculation domain and the solid calculation domain;

[0010] Step 3, mesh the solid computational domain, evenly distribute the mesh nodes on the model surface, and obtain the solid computational mesh;

[0011] The external flow field calculation domain is meshed to generate the aircraft carrier background mesh domain and the foreground mesh domain containing the flexible rope and the UAV. In the overlapping part of the foreground mesh domain and the background mesh domain, the mesh size is controlled by local encryption to construct the interpolated overlapping mesh.

[0012] Step 4: Use the fluid solver to calculate the interpolated overlapping grids to obtain the flow field data at the grid nodes;

[0013] Use the solid solver to calculate the solid computational mesh generated in step 3 to obtain the solid deformation data at the mesh nodes;

[0014] Step 5: Output the coupling result of the flow field data and solid deformation data obtained in step 4 through fluid-solid bidirectional coupling;

[0015] Step 6: Taking the recovery time T0 of the UAV as the judgment condition, perform mesh adjustment and result output on the fluid domain and solid domain used in the coupling part;

[0016] If the fluid-solid coupling simulation time T≥T0 is not satisfied, proceed to step 7, otherwise proceed to step 8;

[0017] Step 7: The mesh of the external flow field calculation domain is subjected to mesh torsion deformation and local mesh regeneration according to the mesh deformation threshold;

[0018] Solid geometry domain mesh is re-meshed;

[0019] Step 8. Output the calculation results to check the impact of the carrier aircraft's wake area on the flexible rope and the UAV's motion trajectory, determine the success rate of the recovery process and the rationality of the isolation model layout, adjust and optimize different components, and change the different applicable material properties of the simulation object.

[0020] Furthermore, in step 2, during the UAV recovery process, the external flow field calculation domain includes the carrier aircraft, the flexible rope, and the UAV;

[0021] The solid calculation domain includes the flexible rope and the UAV, in which the carrier is only responsible for generating the wake and acting on the flexible rope and the UAV, and does not participate in the deformation calculation of the solid.

[0022] Furthermore, in step 3, the solid computational domain is meshed as follows:

[0023] The internal solid meshes are drawn for the flexible rope and the UAV. The mesh size is divided based on the size of the UAV's trailing edge. The flexible rope is swept with a hexahedral mesh, and the surface of the UAV is filled with an unstructured mesh to obtain a solid computational mesh.

[0024] Further, in step 3, the external flow field calculation domain is gridded, which specifically includes the following steps:

[0025] 3.1. Draw a fluid grid for the carrier separately as the background grid part of the overlapping grid;

[0026] 3.2. The entire aircraft part is divided into 10 to 20 times the size of the wing trailing edge, and the relative spatial position of the flexible rope and the UAV is locally encrypted for subsequent overlapping mesh interpolation. For the main wing, horizontal tail, vertical tail and UAV wing parts with prominent influence on aerodynamic characteristics, an encrypted frame is constructed. The surface mesh is triangular, and the spatial mesh is created using the ploy-hexcore method with a cross-sectional shape of hexagonal filling; the flexible rope and the UAV jointly draw the fluid mesh as the foreground mesh part of the overlapping mesh;

[0027] 3.3. The flexible rope and the UAV are meshed according to the minimum surface size. The meshes around the flexible rope and the UAV are encrypted with the spatial mesh size encrypted at the foreground mesh in 3.2 to construct the interpolated overlapping meshes.

[0028] Furthermore, in step 4, the specific process of obtaining the flow field data is: use the fluid solver to perform steady-state calculations on the interpolated overlapping grids, use the final solution of the steady-state calculations as the initial field for the unsteady calculations, start calculating the unsteady calculation part of the external flow field calculation domain, and obtain the flow field data at the grid nodes.

[0029] Furthermore, in step 4, the specific process of obtaining the solid deformation data is as follows:

[0030] Use the solid solver to calculate the solid computational grid generated in step 3, select the same time step as the unsteady calculation of the external flow field, assign corresponding material properties to the flexible rope and the drone, add gravity, monitor the corresponding deformation and velocity parameters, and obtain the solid deformation data at the grid nodes.

[0031] Further, step 5 is specifically as follows:

[0032] The flow field data and solid deformation data obtained in step 4 are used to establish the force and displacement parameter exchange between the fluid domain and the solid domain through fluid-solid bidirectional coupling. The fluid-solid coupling simulation time T and the coupling time step are set, the result output frequency is adjusted to multiple coupling saves, and the last coupling result is output.

[0033] Furthermore, in step 7, the mesh of the external flow field calculation domain is mesh smoothed and mesh torsion deformed according to the mesh deformation threshold; at the same time, the mesh of the external flow field calculation domain is locally regenerated by the linear elastic body method with a minimum mesh size and a mesh slope value of 0.95.

[0034] Further, in step 8, the calculation results include lift and drag, moment, flow field cloud diagram, deformation displacement, velocity and acceleration.

[0035] Compared with the prior art, the present invention has the following beneficial technical effects:

[0036] The present invention discloses a numerical simulation method for bidirectional fluid-solid coupling of drone recovery, which uses a far-field background grid and a foreground grid of a moving part (such as a drone), and a method of local torsion deformation and reconstruction of the foreground grid to achieve rigid-flexible coupling of multiple models. At the same time, it has good robustness for multiple moving parts, and the calculation of complex surfaces such as drone recovery can more realistically reflect the motion changes of the drone recovery process, can accurately simulate the motion boundary of the drone, and provide recovery safety assessment under the combined action of the carrier wake and flexible rope towing.

[0037] The present invention can more realistically reflect the changes in the flow field during the recovery process through a steady and unsteady simulation method, and can adapt to the recovery process of multiple drones at the same time. The entire process is simple to operate, has strong applicability, and high engineering practicality.

[0038] The method of the present invention can be used to obtain changes in various aerodynamic parameters of the UAV during the recovery process, such as speed, angular velocity, angular acceleration, torque, lift and drag, as well as deformation displacement and cloud map of the rope, so as to quickly judge the success rate of the recovery process and the rationality of the layout, and facilitate adjustment and optimization of different components and configuration of different material properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a process framework diagram of the present invention;

[0040] Figure 2 It is a model diagram used in the calculation of the present invention;

[0041] Figure 3 It is the carrier background grid domain of the present invention. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the present invention more clear, the following is further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, not all embodiments.

[0043] The components described and shown in the drawings and embodiments of the present invention may be arranged and designed in various configurations. Therefore, the detailed description of the embodiments of the present invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely represents a selected embodiment of the present invention. Based on the drawings and embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0044] The present invention discloses a numerical simulation method for bidirectional fluid-solid coupling of UAV recovery, comprising the following steps:

[0045] Step 1, select the carrier, flexible rope and UAV model as simulation objects;

[0046] Step 2: Divide the simulation object into different calculation areas through geometric processing to obtain the external flow field calculation domain and the solid calculation domain;

[0047] Step 3, mesh the solid computational domain, evenly distribute the mesh nodes on the model surface, and obtain the solid computational mesh;

[0048] The external flow field calculation domain is meshed to generate the aircraft carrier background mesh domain and the foreground mesh domain containing the flexible rope and the UAV. In the overlapping part of the foreground mesh domain and the background mesh domain, the mesh size is controlled by local encryption to construct the interpolated overlapping mesh.

[0049] Step 4: Use the fluid solver to calculate the interpolated overlapping grids to obtain the flow field data at the grid nodes;

[0050] Use the solid solver to calculate the solid computational mesh generated in step 3 to obtain the solid deformation data at the mesh nodes;

[0051] Step 5: Output the coupling result of the flow field data and solid deformation data obtained in step 4 through fluid-solid bidirectional coupling;

[0052] Step 6: Taking the recovery time T0 of the UAV as the judgment condition, perform mesh adjustment and result output on the fluid domain and solid domain used in the coupling part;

[0053] If the fluid-solid coupling simulation time T≥T0 is not satisfied, proceed to step 7, otherwise proceed to step 8;

[0054] Step 7: The mesh of the external flow field calculation domain is subjected to mesh torsion deformation and local mesh regeneration according to the mesh deformation threshold;

[0055] Solid geometry domain mesh is re-meshed;

[0056] Step 8. Output the calculation results to check the impact of the carrier aircraft's wake area on the flexible rope and the UAV's motion trajectory, determine the success rate of the recovery process and the rationality of the isolation model layout, adjust and optimize different components, and change the different applicable material properties of the simulation object.

[0057] The features and performances of the present invention are further described in detail below with reference to examples.

[0058] The present invention discloses a numerical simulation method for bidirectional fluid-solid coupling of UAV recovery. Different calculation areas are divided first, and calculation parameters of different calculation domains are set in the ANSYS workbench environment. The coupling surface interpolation and data exchange of fluid and solid are performed through system coupling, and the coupled motion change results are output, such as Figure 1 As shown, the specific steps include:

[0059] Step 1: Select an arbitrary carrier, a certain length of flexible rope and a complex shape such as Figure 2 The drone model shown.

[0060] Step 2: Use Spaceclaim to divide the model into two parts: the external flow field calculation domain and the solid calculation domain. During the recovery process of the drone, the external flow field calculation domain must include the carrier, the flexible rope and the drone, and the solid calculation domain must include the flexible rope and the drone. The carrier is only responsible for generating a wake to act on the rope and the drone, and does not participate in the deformation calculation of the solid.

[0061] Step 3: Grid the solid calculation domain and the external flow field calculation domain respectively. The external flow field calculation domain needs to use the overlapping grid method. The specific operation steps of the grid are as follows:

[0062] Step 3.1, mesh of external flow field calculation domain: the carrier aircraft draws the fluid mesh separately, which belongs to the background mesh part of the overlapping mesh. The entire carrier aircraft part is divided into larger sizes, and the relative spatial positions of the flexible rope and the UAV are locally encrypted for the subsequent overlapping mesh interpolation. For the main wing, horizontal tail, vertical tail and UAV wing parts with prominent influence on aerodynamic characteristics, an encrypted frame is constructed. The surface mesh is triangular, and the spatial mesh is created using the ploy-hexcore method with a hexagonal filling of the cross-section shape; the flexible rope and the UAV draw the fluid mesh together, which belongs to the foreground part of the overlapping mesh. The flexible rope and the UAV are meshed according to the minimum surface size, and the mesh around the flexible rope and the UAV is encrypted with the encrypted spatial mesh size at the foreground mesh.

[0063] Step 3.2, solid computational domain mesh: Draw the internal solid mesh of the flexible rope and the UAV. The mesh size should be similar to the fluid foreground mesh size. The flexible rope is swept using a hexahedral mesh, and the surface of the UAV is filled with an unstructured mesh.

[0064] Step 4: overlap interpolation of external flow field grids, use the smooth and remesh grid reconstruction methods, set Linearly Elastic Solid to perform local grid torsion deformation according to the grid deformation threshold, use the LocalCell method to adaptively regenerate the local grid with the minimum and maximum grid lengths and the maximum grid slope, and implicitly update the grid. The specific global grid is as follows: Figure 3 shown.

[0065] Step 5: Use Fluent Flow to calculate the overlapping grid with the given parameters in step 4, perform steady calculations, use the corresponding results as the initial values ​​for unsteady calculations, and start the unsteady calculation part of the coupled calculation of the external flow field calculation domain.

[0066] Step 6. Use the solid computational grid generated in the transient structure calculation step 3.2, select the same time step as the unsteady calculation of the external flow field, such as 0.0001, assign corresponding material properties to the flexible rope and the drone, such as nylon and structural steel, add gravity, and monitor the corresponding deformation and velocity parameters.

[0067] Step 7: Set up the coupling module. System coupling establishes the force and displacement parameter exchange between the fluid domain and the solid domain. Set the fluid-solid coupling simulation time T and the coupling time step. Adjust the result output frequency to five couplings and output the fifth coupling result.

[0068] Step 8. Check the influence of the carrier aircraft's wake area on the motion trajectory of the flexible rope and the UAV in the fluid solver Fluent Flow and the solid solver Transient structure respectively. According to the calculated parameters of the UAV and the flexible rope, such as (angular) velocity, (angular) acceleration, lift and drag, and displacement, judge the success rate of the recovery process and the rationality of the layout of the partition model, adjust and optimize different components, and change the properties of different applicable materials.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A numerical simulation method for bidirectional fluid-solid coupling of UAV recovery, characterized in that: The following steps are involved: Step 1, select the carrier, flexible rope and UAV model as simulation objects; Step 2: Divide the simulation object into different calculation areas through geometric processing to obtain the external flow field calculation domain and the solid calculation domain; Step 3, mesh the solid computational domain, evenly distribute the mesh nodes on the model surface, and obtain the solid computational mesh; The external flow field calculation domain is meshed to generate the aircraft carrier background mesh domain and the foreground mesh domain containing the flexible rope and the UAV. In the overlapping part of the foreground mesh domain and the background mesh domain, the mesh size is controlled by local encryption to construct the interpolated overlapping mesh. Step 4: Use the fluid solver to calculate the interpolated overlapping grids to obtain the flow field data at the grid nodes; Use the solid solver to calculate the solid computational mesh generated in step 3 to obtain the solid deformation data at the mesh nodes; Step 5: Output the coupling result of the flow field data and solid deformation data obtained in step 4 through fluid-solid bidirectional coupling; Step 6: Taking the recovery time T0 of the UAV as the judgment condition, perform mesh adjustment and result output on the fluid domain and solid domain used in the coupling part; If the fluid-solid coupling simulation time T≥T0 is not satisfied, proceed to step 7, otherwise proceed to step 8; Step 7: The mesh of the external flow field calculation domain is subjected to mesh torsion deformation and local mesh regeneration according to the mesh deformation threshold; Solid geometry domain mesh is re-meshed; Step 8. Output the calculation results to check the impact of the carrier aircraft's wake area on the flexible rope and the UAV's motion trajectory, determine the success rate of the recovery process and the rationality of the isolation model layout, adjust and optimize different components, and change the different applicable material properties of the simulation object.

2. The numerical simulation method for bidirectional fluid-solid coupling of UAV recovery according to claim 1 is characterized in that: In step 2, during the UAV recovery process, the external flow field calculation domain includes the carrier aircraft, the flexible rope, and the UAV; The solid calculation domain includes the flexible rope and the UAV, in which the carrier is only responsible for generating the wake and acting on the flexible rope and the UAV, and does not participate in the deformation calculation of the solid.

3. The numerical simulation method for bidirectional fluid-solid coupling of UAV recovery according to claim 1 is characterized in that: In step 3, the solid computational domain is meshed as follows: The internal solid meshes are drawn for the flexible rope and the UAV. The mesh size is divided based on the size of the UAV's trailing edge. The flexible rope is swept with a hexahedral mesh, and the surface of the UAV is filled with an unstructured mesh to obtain a solid computational mesh.

4. The numerical simulation method for bidirectional fluid-solid coupling of UAV recovery according to claim 1 is characterized in that: In step 3, the external flow field calculation domain is meshed, which specifically includes the following steps: 3.

1. Draw a fluid grid for the carrier separately as the background grid part of the overlapping grid; 3.

2. The entire aircraft part is divided into 10 to 20 times the size of the wing trailing edge, and the relative spatial position of the flexible rope and the UAV is locally encrypted for subsequent overlapping mesh interpolation. For the main wing, horizontal tail, vertical tail and UAV wing parts with prominent influence on aerodynamic characteristics, an encrypted frame is constructed. The surface mesh is triangular, and the spatial mesh is created using the ploy-hexcore method with a cross-sectional shape of hexagonal filling; the flexible rope and the UAV jointly draw the fluid mesh as the foreground mesh part of the overlapping mesh; 3.

3. The flexible rope and the UAV are meshed according to the minimum surface size. The meshes around the flexible rope and the UAV are encrypted with the spatial mesh size encrypted at the foreground mesh in 3.2 to construct the interpolated overlapping meshes.

5. The numerical simulation method for bidirectional fluid-solid coupling of UAV recovery according to claim 1 is characterized in that: In step 4, the specific process of obtaining the flow field data is: use the fluid solver to perform steady-state calculations on the interpolated overlapping grids, use the final solution of the steady-state calculation as the initial field for the unsteady calculation, start calculating the unsteady calculation part of the external flow field calculation domain, and obtain the flow field data at the grid nodes.

6. The numerical simulation method for bidirectional fluid-solid coupling of UAV recovery according to claim 1 is characterized in that: In step 4, the specific process of obtaining solid deformation data is as follows: Use the solid solver to calculate the solid computational grid generated in step 3, select the same time step as the unsteady calculation of the external flow field, assign corresponding material properties to the flexible rope and the drone, add gravity, monitor the corresponding deformation and velocity parameters, and obtain the solid deformation data at the grid nodes.

7. The numerical simulation method for bidirectional fluid-solid coupling of UAV recovery according to claim 1 is characterized in that: Step 5 is as follows: The flow field data and solid deformation data obtained in step 4 are used to establish the force and displacement parameter exchange between the fluid domain and the solid domain through fluid-solid bidirectional coupling. The fluid-solid coupling simulation time T and the coupling time step are set, the result output frequency is adjusted to multiple coupling saves, and the last coupling result is output.

8. The numerical simulation method for bidirectional fluid-solid coupling of UAV recovery according to claim 1 is characterized in that: In step 7, the mesh of the external flow field calculation domain is mesh smoothed and mesh torsion deformed according to the mesh deformation threshold; at the same time, the mesh of the external flow field calculation domain is locally regenerated by the linear elastic body method with a minimum mesh size and a mesh slope value of 0.

95.

9. The numerical simulation method for bidirectional fluid-solid coupling of UAV recovery according to claim 1 is characterized in that: In step 8, the calculation results include lift and drag, moment, flow field cloud diagram, deformation displacement, velocity and acceleration.

Images