Parallel configuration aircraft separation characteristic simulation method based on CFD / RBD

Abstract

The invention provides a CFD / RBD-based parallel configuration aircraft separation characteristic simulation method. The method comprises the following steps: S10, establishing a component grid and a background grid; s20, generating an overlapping grid; s30, performing steady calculation by using a CFD solver to obtain the flow field at the current moment and the aerodynamic load of each sub-stage; s40, solving the dynamic control equation by the RBD solver to obtain motion parameters of each sublevel at the next moment, and sending the motion parameters to a CFD solver; s50, obtaining the updated component grid of each sub-level; s60, generating an updated overlapping grid; s70, on the basis of the updated overlapped grid, a CFD solver is used for solving the flow field by adopting a double-time step method, and the flow field at the next moment and the aerodynamic load of each sublevel are obtained; and S80, repeating the steps S40 to S70 until the preset simulation time is reached, so as to complete the separation characteristic simulation of the parallel configuration aircraft. According to the method, the technical problem that the transient characteristic of the interstage interference between the aircraft and the boosting stage is difficult to present by the method in the prior art can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of aircraft design, and in particular to a CFD / RBD-based method for simulating separation characteristics of parallel-configuration aircraft. Background Art

[0002] During the launch of the magnetic levitation electromagnetic booster, the spacecraft and the booster stage form a parallel configuration spacecraft. Whether the spacecraft and the booster stage can be safely unlocked and separated determines the success or failure of the launch mission. There is a complex interstage flow field interference effect between the spacecraft and the booster stage, which causes the separation body to be subjected to complex transient aerodynamic loads and is closely coupled with the dynamic process of the separation body; in addition, the separation device will also constrain the relative motion characteristics between the separation bodies, which in turn makes it difficult to establish the separation strategy and predict the separation characteristics.

[0003] For multi-body separation dynamics problems such as the separation of parallel-configuration aircraft, commonly used research methods include indirect prediction methods based on steady aerodynamic loads and direct prediction methods based on quasi-steady or unsteady aerodynamic loads. Among them, the indirect prediction method based on steady aerodynamic loads is represented by the grid method. Through a large amount of numerical simulation or wind tunnel test data, the steady-state aerodynamic interference characteristics between the separated bodies are considered, and the separation characteristics are obtained through ballistic simulation based on the Monte Carlo method, and the analysis of separation influencing factors is given in a probabilistic way. The direct prediction method based on quasi-steady is represented by the trajectory capture method. The aerodynamic load of the separated body is obtained through experiments or numerical means, and the position and attitude of the separated body at the next moment are solved accordingly. After the separated body is adjusted to the specified position and attitude, the aerodynamic load analysis is carried out again, and the above process is repeated until the calculation is completed.

[0004] Due to the complex unsteady flow characteristics between the vehicle and the booster stage, it is difficult to present the transient characteristics of the inter-stage interference using the above method. Summary of the invention

[0005] The present invention provides a CFD / RBD-based method for simulating separation characteristics of a parallel-configuration aircraft, which can solve the technical problem that the methods in the prior art are difficult to present the transient characteristics of the interference between the aircraft and the booster stage.

[0006] According to one aspect of the present invention, a method for simulating separation characteristics of parallel configuration aircraft based on CFD / RBD is provided, the method comprising:

[0007] S10, establishing an unstructured grid for each sub-level of the parallel configuration aircraft, and using the unstructured grid of each sub-level as a component grid of each sub-level, establishing an unstructured grid for the motion airspace of the parallel configuration aircraft, and using the unstructured grid of the motion airspace as a background grid;

[0008] S20, determining the interpolation boundary of each component grid according to the principle of whether a contributing unit can be found in the background grid, and digging holes in the background grid according to the interpolation boundary of each component grid to generate overlapping grids;

[0009] S30, based on the overlapping grids, using the CFD solver to perform steady-state calculations to obtain the flow field at the current moment and the aerodynamic loads of each sub-stage;

[0010] S40, establishing a dynamic control equation according to the aerodynamic load of each sub-stage at the current moment and the mass, moment of inertia, structural connection relationship and initial motion parameters of each sub-stage of the parallel configuration aircraft, and the RBD solver solves the dynamic control equation to obtain the motion parameters of each sub-stage at the next moment, and sends them to the CFD solver;

[0011] S50, determining translation parameters and rotation parameters according to the motion parameters of each sub-level at the next moment, and translating and rotating the component meshes corresponding to each sub-level of the parallel configuration aircraft according to the translation parameters and rotation parameters to obtain updated component meshes of each sub-level;

[0012] S60, determining the interpolation boundaries of each updated component grid according to the principle of whether a contributing unit can be found in the background grid, and digging holes in the background grid according to the interpolation boundaries of each updated component grid to generate an updated overlapping grid;

[0013] S70, based on the updated overlapping grid, using the CFD solver to solve the flow field using a double time step method to obtain the flow field at the next moment and the aerodynamic loads of each sub-stage;

[0014] S80, repeat S40 to S70 until the preset simulation time is reached, so as to obtain the change history of aerodynamic loads, motion parameters and flow fields of each sub-stage of the parallel configuration aircraft over time in the entire simulation stage, thereby completing the separation characteristic simulation of the parallel configuration aircraft.

[0015] Preferably, after S10, the method further comprises: meshing the area between the sub-stages of the parallel configuration aircraft.

[0016] Preferably, the CFD solver is used to perform steady calculations to obtain the flow field at the current moment and the aerodynamic loads of each sub-stage, including:

[0017] The Reynolds-averaged Navier-Stokes equations of a three-dimensional arbitrary Lagrangian-Euler system are used as the flow control equations. The equations are closed by the k-ωSST turbulence model and the ideal gas model. The pressure far-field boundary conditions are determined according to the incoming flow velocity and static pressure, and the no-slip boundary conditions are used on the wall.

[0018] Use CFD solver to perform steady calculations to obtain the flow field at the current moment;

[0019] According to the flow field at the current moment, the surface pressure field of each sub-level at the current moment is obtained;

[0020] The aerodynamic load of each sub-stage at the current moment is obtained by integrating the surface pressure field of each sub-stage at the current moment.

[0021] Preferably, the CFD solver is a finite volume method CFD solver Fluent.

[0022] Preferably, the RBD solver is an RBD solver MBDyn based on an implicit, A / L stable, second-order accurate predictive-corrector integrator.

[0023] Preferably, the motion parameters include translational velocity, rotational velocity, displacement and posture.

[0024] Preferably, the structural connection of each sub-stage is a catapult, a hinge or a ball joint.

[0025] According to another aspect of the present invention, a computer device is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements any of the above methods when executing the computer program.

[0026] By applying the technical solution of the present invention, a coupled solution of aerodynamic load and separation body motion is achieved through a coupled solution of a CFD solver and an RBD solver, so as to present the separation motion characteristics under the action of aerodynamic load to the greatest extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 A flow chart of a CFD / RBD-based parallel configuration aircraft separation characteristic simulation method according to an embodiment of the present invention is shown;

[0029] Figure 2 A coupling schematic diagram of a CFD / RBD-based parallel configuration aircraft separation characteristic simulation method according to an embodiment of the present invention is shown;

[0030] Figure 3 A schematic diagram of a wing / external store release separation standard model provided according to an embodiment of the present invention is shown;

[0031] Figure 4 A curve diagram showing the linear displacement of an external attachment provided in accordance with an embodiment of the present invention is shown;

[0032] Figure 5 A curve chart of the angular displacement of an external attachment provided according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0033] It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0035] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0036] like Figure 1 and Figure 2 As shown, the present invention provides a CFD / RBD-based parallel configuration aircraft separation characteristics simulation method, the method comprising:

[0037] S10, establishing an unstructured grid for each sub-level of the parallel configuration aircraft, and using the unstructured grid of each sub-level as a component grid of each sub-level, establishing an unstructured grid for the motion airspace of the parallel configuration aircraft, and using the unstructured grid of the motion airspace as a background grid;

[0038] S20, determining the interpolation boundary of each component grid according to the principle of whether a contributing unit can be found in the background grid, and digging holes in the background grid according to the interpolation boundary of each component grid to generate overlapping grids;

[0039] S30, based on the overlapping grids, using a CFD (computational fluid dynamics) solver to perform steady-state calculations to obtain the flow field at the current moment and the aerodynamic loads of each sub-stage;

[0040] S40, establishing a dynamic control equation according to the aerodynamic load of each sub-stage at the current moment and the mass, moment of inertia, structural connection relationship and initial motion parameters of each sub-stage of the parallel configuration aircraft, and solving the dynamic control equation by an RBD (rigid body dynamics) solver to obtain the motion parameters of each sub-stage at the next moment, and sending them to a CFD solver;

[0041] S50, determining translation parameters and rotation parameters according to the motion parameters of each sub-level at the next moment, and translating and rotating the component meshes corresponding to each sub-level of the parallel configuration aircraft according to the translation parameters and rotation parameters to obtain updated component meshes of each sub-level;

[0042] S60, determining the interpolation boundaries of each updated component grid according to the principle of whether a contributing unit can be found in the background grid, and digging holes in the background grid according to the interpolation boundaries of each updated component grid to generate an updated overlapping grid;

[0043] S70, based on the updated overlapping grid, using the CFD solver to solve the flow field using a double time step method to obtain the flow field at the next moment and the aerodynamic loads of each sub-stage;

[0044] S80, repeat S40 to S70 until the preset simulation time is reached, so as to obtain the change history of aerodynamic loads, motion parameters and flow fields of each sub-stage of the parallel configuration aircraft over time in the entire simulation stage, thereby completing the separation characteristic simulation of the parallel configuration aircraft.

[0045] The present invention realizes coupled solution of aerodynamic load and separation body motion through coupled solution of CFD solver and RBD solver, and presents separation motion characteristics under the action of aerodynamic load to the greatest extent.

[0046] According to an embodiment of the present invention, in order to improve the calculation accuracy of subsequent steps, after S10, the method further includes: meshing the area between the sub-stages of the parallel configuration aircraft.

[0047] According to an embodiment of the present invention, a CFD solver is used to perform steady calculations to obtain the flow field at the current moment and the aerodynamic loads of each sub-stage, including:

[0048] The Reynolds-averaged Navier-Stokes (RANS) equations of a three-dimensional arbitrary Lagrangian-Euler system (ALE) are used as the flow control equations. The equation group is closed by the k-ωSST turbulence model and the ideal gas model. The pressure far-field boundary conditions are determined according to the incoming flow velocity and static pressure, and the no-slip boundary conditions are used on the wall.

[0049] Use CFD solver to perform steady calculations to obtain the flow field at the current moment;

[0050] According to the flow field at the current moment, the surface pressure field of each sub-level at the current moment is obtained;

[0051] The aerodynamic load of each sub-stage at the current moment is obtained by integrating the surface pressure field of each sub-stage at the current moment.

[0052] According to an embodiment of the present invention, the CFD solver is a finite volume method CFD solver Fluent.

[0053] According to one embodiment of the present invention, the RBD solver is an RBD solver MBDyn based on an implicit, A / L stable, second-order accurate predictive-corrector integrator.

[0054] According to an embodiment of the present invention, the motion parameters include translation speed, rotation speed, displacement and posture.

[0055] According to one embodiment of the present invention, in order to achieve complex constrained stage separation and make it closer to the separation process of a parallel configuration aircraft, the structural connection of each sub-stage can adopt a series of structures such as catapults, hinges or ball joints.

[0056] In order to further understand the present invention, the following Figure 3-Figure 5 The CFD / RBD-based method for simulating separation characteristics of parallel-configuration aircraft of the present invention is described in detail.

[0057] In this embodiment, the separation characteristics of the wing / external load release separation standard model are simulated. Figure 3 As shown, it consists of an external attachment with winglets and a semi-delta wing with a 45° leading edge sweep angle. The wing root chord length is 7.62m, the span is 6.6m, and the tip-to-root ratio is 0.134. The external attachment is 3.02m long, the center of gravity is 1.42m from the front end, the mass is 907.8kg, and the moment of inertia is Ixx=27.12kg·m 2 , Iyy=Izz=488.1kg·m2 The front ejector is arranged at a distance of 1.24m from the head of the external attachment, and the force applied is 10679.4N; the rear ejector is arranged at a distance of 1.75m from the head of the external attachment, and the force applied is 42717.5N. The stroke length of the ejector to apply force is 0.1m.

[0058] Through CFD / RBD coupling solution, the curves of the displacement of the centerline and angular displacement of the external material over time are obtained, such as Figure 4 , Figure 5 As shown, it can be seen that the X-direction displacement Xcg Exp, Y-direction displacement Ycg Exp, Z-direction displacement Zcg Exp, roll angle Roll Exp, yaw angle Yaw Exp and pitch angle Pitch Exp of the external material center are in good agreement with their respective test results (CFD / RBD curves), indicating that this method can better predict the separation characteristics of external objects.

[0059] The present invention also provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements any of the above methods when executing the computer program.

[0060] In summary, the present invention provides a CFD / RBD-based method for simulating separation characteristics of parallel-configuration aircraft, which has the following beneficial effects compared with the prior art:

[0061] 1. It can realize the coupled solution of aerodynamic load and separation body motion, and present the separation motion characteristics under the action of aerodynamic load to the greatest extent;

[0062] 2. Based on the open source MBDyn solution, a variety of ejection forces, constraint forces, etc. can be effectively established, which is conducive to the modeling of complex separation mechanisms.

[0063] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the devices or elements referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention. The directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0064] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0065] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A CFD / RBD-based method for simulating separation characteristics of parallel configuration aircraft, characterized in that: The method comprises: S10, establishing an unstructured grid for each sub-level of the parallel configuration aircraft, and using the unstructured grid of each sub-level as a component grid of each sub-level, establishing an unstructured grid for the motion airspace of the parallel configuration aircraft, and using the unstructured grid of the motion airspace as a background grid; S20, determining the interpolation boundary of each component grid according to the principle of whether a contributing unit can be found in the background grid, and digging holes in the background grid according to the interpolation boundary of each component grid to generate overlapping grids; S30, based on the overlapping grids, using the CFD solver to perform steady-state calculations to obtain the flow field at the current moment and the aerodynamic loads of each sub-stage; S40, establishing a dynamic control equation according to the aerodynamic load of each sub-stage at the current moment and the mass, moment of inertia, structural connection relationship and initial motion parameters of each sub-stage of the parallel configuration aircraft, and the RBD solver solves the dynamic control equation to obtain the motion parameters of each sub-stage at the next moment, and sends them to the CFD solver; S50, determining translation parameters and rotation parameters according to the motion parameters of each sub-level at the next moment, and translating and rotating the component meshes corresponding to each sub-level of the parallel configuration aircraft according to the translation parameters and rotation parameters to obtain updated component meshes of each sub-level; S60, determining the interpolation boundaries of each updated component grid according to the principle of whether a contributing unit can be found in the background grid, and digging holes in the background grid according to the interpolation boundaries of each updated component grid to generate an updated overlapping grid; S70, based on the updated overlapping grid, using the CFD solver to solve the flow field using a double time step method to obtain the flow field at the next moment and the aerodynamic loads of each sub-stage; S80, repeat S40 to S70 until the preset simulation time is reached, so as to obtain the change history of aerodynamic loads, motion parameters and flow fields of each sub-stage of the parallel configuration aircraft over time in the entire simulation stage, thereby completing the separation characteristic simulation of the parallel configuration aircraft.

2. The method according to claim 1, characterized in that After S10, the method further includes: meshing the area between the sub-stages of the parallel configuration aircraft.

3. The method according to claim 1 or 2, characterized in that: Using the CFD solver for steady calculation, the flow field at the current moment and the aerodynamic loads of each sub-stage are obtained, including: The Reynolds-averaged Navier-Stokes equations of a three-dimensional arbitrary Lagrangian-Euler system are used as the flow control equations. The equations are closed by the k-ωSST turbulence model and the ideal gas model. The pressure far-field boundary conditions are determined according to the incoming flow velocity and static pressure, and the no-slip boundary conditions are used on the wall. Use CFD solver to perform steady calculations to obtain the flow field at the current moment; According to the flow field at the current moment, the surface pressure field of each sub-level at the current moment is obtained; The aerodynamic load of each sub-stage at the current moment is obtained by integrating the surface pressure field of each sub-stage at the current moment.

4. The method according to claim 1, characterized in that: The CFD solver is Fluent, a finite volume method CFD solver.

5. The method according to claim 1, characterized in that The RBD solver is an implicit, A / L stable, second-order accurate predictive-corrector integrator-based RBD solver MBDyn.

6. The method according to claim 1, characterized in that The motion parameters include translation speed, rotation speed, displacement and posture.

7. The method according to any one of claims 1 to 6, characterized in that: The structural connection of each sub-stage is a catapult, a hinge or a ball joint.

8. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 7 is implemented.

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