A CFD / RBD-based simulation method for the separation characteristics of a parallel configuration aircraft

Abstract

The application provides a CFD / RBD-based simulation method for separation characteristics of a parallel configuration aircraft, which 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 a flow field at a current time and aerodynamic loads of each sub-stage; S40, performing solution on a dynamic control equation by using an RBD solver to obtain motion parameters of each sub-stage at a next time, and sending the motion parameters to the CFD solver; S50, obtaining updated component grids of each sub-stage; S60, generating updated overlapping grids; S70, performing flow field solution by using the CFD solver based on the updated overlapping grids and by using a double-time-step method to obtain a flow field at the next time and the aerodynamic loads of each sub-stage; and S80, repeating S40 to S70 until a preset simulation time is reached, so as to complete simulation of the separation characteristics of the parallel configuration aircraft. The application can solve the technical problem that the method in the prior art is difficult to present the transient characteristics of the interference between the aircraft and the boost stage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aircraft design, in particular to a CFD / RBD-based simulation method for separation characteristics of a parallel-connection configuration aircraft. BACKGROUND

[0002] In the process of magnetic suspension electromagnetic boosting launch, the aircraft and the booster form a parallel-connection configuration aircraft, and whether the aircraft and the booster can be safely unlocked and separated determines the success or failure of the launch mission. The aircraft and the booster have complex inter-stage flow field interference effects, which cause the separation body to be subjected to complex transient aerodynamic loads and be 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 further causes difficulties in separation strategy establishment and separation characteristic prediction.

[0003] For the separation of a parallel-connection configuration aircraft, the commonly used research methods include an indirect prediction method based on steady aerodynamic loads and a direct prediction method 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, which considers the steady-state aerodynamic interference characteristics between the separation bodies through a large number of numerical simulation or wind tunnel test data, and obtains the separation characteristics through a trajectory simulation based on the Monte Carlo method, and gives the separation influencing factor analysis in a probabilistic manner. The direct prediction method based on quasi-steady is represented by the trajectory capture method, which obtains the aerodynamic load of the separation body through test or numerical means, and solves the position and attitude of the separation body at the next moment according to the aerodynamic load, adjusts the separation body to the specified position and attitude, and then carries out aerodynamic load analysis again, and the above process is repeated until the calculation is completed.

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

[0005] The present application provides a CFD / RBD-based simulation method for separation characteristics of a parallel-connection configuration aircraft, which can solve the technical problem that the existing method is difficult to present the transient characteristics of the inter-stage interference between the aircraft and the booster.

[0006] According to an aspect of the present application, a CFD / RBD-based simulation method for separation characteristics of a parallel-connection configuration aircraft is provided, which comprises:

[0007] S10, a non-structured grid is established for each sub-stage of the parallel-connection configuration aircraft, and the non-structured grid of each sub-stage is taken as a component grid of each sub-stage; a non-structured grid is established for the motion space of the parallel-connection configuration aircraft, and the non-structured grid of the motion space is taken as a background grid;

[0008] S20, determine the interpolation boundary of each component grid according to the principle of whether the contribution unit can be found in the background grid, and perform hole digging on the background grid according to the interpolation boundary of each component grid to generate an overlapping grid;

[0009] S30, based on the overlapping grid, a steady calculation is performed by using a CFD solver to obtain a flow field at a current time and aerodynamic loads of each sub-stage;

[0010] S40, a dynamic control equation is established according to the aerodynamic loads of each sub-stage at the current time and the mass, moment of inertia, structure connection relationship and initial motion parameters of each sub-stage of the parallel configuration aircraft, and a RBD solver is used to solve the dynamic control equation to obtain motion parameters of each sub-stage at a next time and send the motion parameters to the CFD solver;

[0011] S50, translation parameters and rotation parameters are determined according to the motion parameters of each sub-stage at the next time, and each component grid corresponding to each sub-stage of the parallel configuration aircraft is translated and rotated according to the translation parameters and the rotation parameters to obtain updated component grids of each sub-stage;

[0012] S60, the interpolation boundary of each updated component grid is determined according to the principle of whether the contribution unit can be found in the background grid, and the background grid is hole dug according to the interpolation boundary of each updated component grid to generate an updated overlapping grid;

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

[0014] S80, S40 to S70 are repeated until a preset simulation time is reached to obtain the change process of the aerodynamic loads, motion parameters and flow field 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: performing grid densification on a region between each sub-stage of the parallel configuration aircraft.

[0016] Preferably, the steady calculation by using the CFD solver to obtain the flow field at the current time and the aerodynamic loads of each sub-stage comprises:

[0017] The Reynolds-averaged Navier-Stokes equation of a three-dimensional arbitrary Lagrange-Euler system is used as a flow control equation, the equation set is closed by using a k-ω SST turbulence model and an ideal gas model, a pressure far field boundary condition is determined according to an incoming flow velocity and a static pressure, and a wall surface adopts a no-slip boundary condition;

[0018] The CFD solver is used to perform steady calculation to obtain the flow field at the current time;

[0019] obtaining a surface pressure field of each sub-level at the current time according to the flow field at the current time;

[0020] integrating the surface pressure field of each sub-level at the current time to obtain an aerodynamic load of each sub-level at the current time.

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

[0022] Preferably, the RBD solver is an implicit, A / L stable, second-order accuracy predictor-corrector integrator RBD solver MBDyn.

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

[0024] Preferably, the structural connection of each sub-level is a catapult, a hinge or a spherical hinge.

[0025] According to another aspect of the present application, 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-mentioned methods when executing the computer program.

[0026] By coupling the CFD solver and the RBD solver, the aerodynamic load and the separation motion are coupled and solved, and the separation motion characteristics under the action of the aerodynamic load are maximized. BRIEF DESCRIPTION OF DRAWINGS

[0027] The accompanying drawings, which are included to provide a further understanding of the embodiments of the application and constitute a part of this application, serve to explain the principles of the application and, together with the description, to enable the practice of the application. Obviously, the drawings described below are only 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.

[0028] Figure 1 A flow chart of the CFD / RBD-based parallel configuration aircraft separation characteristic simulation method provided by the embodiment of the present application is shown;

[0029] Figure 2 A coupling schematic diagram of the CFD / RBD-based parallel configuration aircraft separation characteristic simulation method provided by the embodiment of the present application is shown;

[0030] Figure 3 A schematic diagram of a wing / external store separation model provided by the embodiment of the present application is shown;

[0031] Figure 4 A curve diagram of the external object linear displacement is shown according to an embodiment of the present application;

[0032] Figure 5 A curve diagram of the external object angular displacement is shown according to an embodiment of the present application. DETAILED DESCRIPTION

[0033] 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 intended to limit the present application and its application or use in any way. 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.

[0034] 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 reference to the presence of a feature, step, operation, device, component and / or combinations thereof.

[0035] Unless otherwise specifically noted, the relative arrangement of parts and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the application. At the same time, it should be understood that the sizes of the various parts shown in the drawings are not drawn in proportion to the actual proportions. The techniques, methods and devices known to those of ordinary skill in the relevant art can not be discussed in detail, but in appropriate cases, the techniques, methods and devices should be considered as part of the authorized description. In all examples shown and discussed herein, any specific value should be interpreted as merely exemplary, and not as a limitation. Therefore, other examples of exemplary embodiments can have different values. It should be noted that similar reference numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0036] As shown in Figure 1 and Figure 2 The present application provides a CFD / RBD-based simulation method for the separation characteristics of a parallel configuration aircraft, which comprises:

[0037] S10, establish a non-structured grid for each sub-stage of the parallel configuration aircraft, and take the non-structured grid of each sub-stage as a component grid of each sub-stage, establish a non-structured grid for a motion space of the parallel configuration aircraft, and take the non-structured grid of the motion space as a background grid;

[0038] S20, determine an interpolation boundary of each component grid according to whether a contribution unit can be found in the background grid, and perform hole digging on the background grid according to the interpolation boundary of each component grid, to generate an overlapping grid;

[0039] S30, perform steady calculation on the overlapping grid by using a CFD (computational fluid dynamics) solver, to obtain a flow field at a current time and aerodynamic loads of each sub-stage;

[0040] S40, establish a dynamic control equation according to the aerodynamic loads of each sub-stage at the current time and mass, moment of inertia, structure connection relationship and initial motion parameters of each sub-stage of the parallel configuration aircraft, perform solving on the dynamic control equation by using an RBD (rigid body dynamics) solver, to obtain motion parameters of each sub-stage at a next time, and send the motion parameters to the CFD solver;

[0041] S50, determine translation parameters and rotation parameters according to the motion parameters of each sub-stage at the next time, and perform translation and rotation on the component grid corresponding to each sub-stage of the parallel configuration aircraft according to the translation parameters and the rotation parameters, to obtain updated component grids of each sub-stage;

[0042] S60, determine an interpolation boundary of each updated component grid according to whether a contribution unit can be found in the background grid, and perform hole digging on the background grid according to the interpolation boundary of each updated component grid, to generate an updated overlapping grid;

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

[0044] S80, repeat S40 to S70 until a preset simulation time is reached, to obtain a change process of the aerodynamic loads, the motion parameters and the flow field of each sub-stage of the parallel configuration aircraft over time in an entire simulation stage, so that separation characteristic simulation of the parallel configuration aircraft is completed.

[0045] The CFD solver and the RBD solver are coupled to realize coupled solving of the aerodynamic loads and the separation body motion, so that the separation motion characteristics under the action of the aerodynamic loads are presented to the greatest extent.

[0046] According to an embodiment of the present application, in order to improve the calculation accuracy of subsequent steps, after S10, the method further comprises: performing grid densification on a region between each sub-stage of the parallel configuration aircraft.

[0047] According to one embodiment of the present application, the steady calculation by the CFD solver obtains the flow field at the current time and the aerodynamic load of each sub-stage, which comprises:

[0048] The Reynolds-averaged Navier-Stokes (RANS) equation of a three-dimensional arbitrary Lagrangian-Eulerian system (ALE) is taken as the flow control equation, the equation group is closed by a k-ω SST turbulence model and an ideal gas model, the pressure far-field boundary condition is determined according to the incoming flow velocity and static pressure, and the wall surface adopts a no-slip boundary condition;

[0049] The steady calculation by the CFD solver obtains the flow field at the current time;

[0050] The surface pressure field of each sub-stage at the current time is obtained according to the flow field at the current time;

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

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

[0053] According to one embodiment of the present application, the RBD solver is an implicit, A / L stable, second-order accuracy predictor-corrector integrator RBD solver MBDyn.

[0054] According to one embodiment of the present application, the motion parameters include translational velocity, rotational velocity, displacement and attitude.

[0055] According to one embodiment of the present application, in order to realize the complex constraint-containing inter-stage separation and make the separation process of the parallel-configuration aircraft closer to the separation process, the structural connection of each sub-stage can adopt a series of structures such as an ejector, a hinged support or a spherical hinge.

[0056] In order to have a further understanding of the present application, the following Figures 3-5 The parallel-configuration aircraft separation characteristic simulation method based on CFD / RBD of the present application is described in detail.

[0057] In the present embodiment, the separation characteristic simulation is performed on a wing / external store release separation standard model. The wing / external store configuration is shown in Figure 3 and is composed of an external store with a winglet and a half-triangle wing with a 45° forward edge sweep angle. The wing root chord length is 7.62 m, the span length is 6.6 m, and the tip-to-root ratio is 0.134. The external store length is 3.02 m, the center of gravity position is 1.42 m away from the front end, the mass is 907.8 kg, and the inertia moment is Ixx=27.12 kg·m 2 , Iyy=Izz=488.1 kg·m2 The front-positioned injector is arranged at a distance of 1.24 m from the head of the external hanging object, and the applied force is 10679.4 N; the rear-positioned injector is arranged at a distance of 1.75 m from the head of the external hanging object, and the applied force is 42717.5 N, and the stroke length of the force applied by the injector is 0.1 m.

[0058] The centroid displacement and angular displacement curves of the external hanging object changing with time are obtained by CFD / RBD coupling solution, as shown in Figure 4 、 Figure 5 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 hanging object are in good agreement with the respective test results (CFD / RBD curves), which shows that the method can better predict the separation characteristics of the external hanging object.

[0059] The application further provides a computer device, including a memory, a processor and a computer program stored in the memory and executable on the processor, and the processor implements the method described above when executing the computer program.

[0060] In summary, the application provides a parallel configuration aircraft separation characteristic simulation method based on CFD / RBD, which has the following beneficial effects compared with the prior art:

[0061] 1. The aerodynamic load and separation body motion coupling solution can be realized, and the separation motion characteristics under the action of the aerodynamic load can be presented to the maximum extent.

[0062] 2. The open-source MBDyn solution can effectively establish various elastic forces, constraint forces and the like, and is beneficial to realize complex separation mechanism modeling.

[0063] In the description of the application, it should be understood that the orientation words such as "front, rear, upper, lower, left, right", "transverse, vertical, perpendicular, horizontal" and "top, bottom" and the like indicate the orientation or position relationship shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and in the absence of the opposite description, these orientation words do not indicate and imply that the indicated device or element must have a specific orientation or be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the protection scope of the application; the orientation words "inner, outer" refer to the inner and outer of the contour of each component itself.

[0064] For purposes of the description hereinafter, the terms "upper", "lower", "right", "left", "rear", "front", "vertical" and "horizontal" as can be perceived herein relative to the accompanying drawings refer to the orientation of the components being described. However, it is to be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device described herein relative to the other device or structure is inverted, then a spatially relative term such as "above" can be interpreted as meaning "below" or "below" can be interpreted as meaning "above". The device can also be oriented in other ways (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. The devices can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0065] In addition, it should be pointed out that the use of the terms "first", "second" and the like in connection with various elements is merely intended for identification, and does not constitute a special meaning, and therefore cannot be interpreted as a limitation on the scope of protection of the present application.

[0066] The preferred embodiments of the present application are described above in detail. The present application, however, is not limited to the above embodiments, but can be variously modified and changed by those skilled in the art without departing from the scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the present application.

Claims

1. A CFD / RBD based simulation method for the separation characteristics of a parallel configuration aircraft, characterized in that, The method comprises: S10, establishing a non-structured grid for each sub-stage of the parallel configuration aircraft, taking the non-structured grid of each sub-stage as a component grid of each sub-stage, and establishing a non-structured grid for a motion space of the parallel configuration aircraft, and taking the non-structured grid of the motion space as a background grid; S20, determining an interpolation boundary of each component grid according to whether a contribution unit can be found in the background grid, and performing hole digging on the background grid according to the interpolation boundary of each component grid to generate an overlapping grid; S30, performing steady calculation on the overlapping grid by using a CFD solver to obtain a flow field at a current time and aerodynamic loads of each sub-stage; S40, establishing a dynamic control equation according to the aerodynamic loads of each sub-stage at the current time and mass, moment of inertia, structure connection relationship and initial motion parameters of each sub-stage of the parallel configuration aircraft, performing solving on the dynamic control equation by using an RBD solver to obtain motion parameters of each sub-stage at a next time, and sending the motion parameters to the CFD solver; S50, determining translation parameters and rotation parameters according to the motion parameters of each sub-stage at the next time, and performing translation and rotation on the component grid corresponding to each sub-stage of the parallel configuration aircraft according to the translation parameters and the rotation parameters to obtain updated component grids of each sub-stage; S60, determining an interpolation boundary of each updated component grid according to whether a contribution unit can be found in the background grid, and performing hole digging on the background grid according to the interpolation boundary of each updated component grid to generate an updated overlapping grid; S70, performing flow field solving on the updated overlapping grid by using the CFD solver to obtain a flow field at the next time and aerodynamic loads of each sub-stage; S80, repeating S40 to S70 until a preset simulation time is reached to obtain the change process of the aerodynamic loads, the motion parameters and the flow field of each sub-stage of the parallel configuration aircraft over time in the entire simulation stage, thereby completing simulation of the separation characteristics of the parallel configuration aircraft.

2. The method of claim 1, wherein, After S10, the method further comprises: performing grid densification on a region between each sub-stage of the parallel configuration aircraft.

3. The method according to claim 1 or 2, characterized in that, The steady calculation by using the CFD solver to obtain the flow field at the current time and the aerodynamic loads of each sub-stage comprises: taking the Reynolds-averaged Navier-Stokes equation of a three-dimensional arbitrary Lagrange-Euler system as a flow control equation, closing the equation set through a k-ω SST turbulence model and an ideal gas model, determining a pressure far-field boundary condition according to an incoming flow velocity and a static pressure, and adopting a no-slip boundary condition for a wall surface; performing steady calculation by using the CFD solver to obtain the flow field at the current time; obtaining a surface pressure field of each sub-stage at the current time according to the flow field at the current time; integrating the surface pressure field of each sub-stage at the current time to obtain the aerodynamic loads of each sub-stage at the current time.

4. The method of claim 1, wherein, The CFD solver is a finite volume method CFD solver Fluent.

5. The method of claim 1, wherein, The RBD solver is an implicit, A / L stable, second-order accuracy predictor-corrector integrator RBD solver MBDyn.

6. The method of claim 1, wherein, The motion parameters comprise translation velocity, rotation velocity, displacement and attitude.

7. The method of claim 1, wherein, The structure connection of each sub-stage is an ejector, a hinged support or a spherical hinge.

8. A computer device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor implements the method of any one of claims 1 to 7 when executing the computer program.

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