Numerical simulation method of high-speed train aerodynamic performance under coupling attitude motion with wind shear

Abstract

The application discloses a kind of high-speed train aerodynamic performance numerical simulation methods of coupling attitude motion under wind shear, it is related to high-speed train numerical simulation technical field.The method includes building a multiple domain computing environment including background domain and overlap domain;The background domain is provided with the wind field boundary condition of simulating wind shear;The overlap domain envelops all moving parts of train, and is coupled with the background domain through overlap grid interface;In the CFD framework, each moving part is characterized by defining three-dimensional continuum with physical properties, and the multi-body motion degree of freedom thereof is activated;By setting elastic connecting elements between each moving part continuum, the multi-body dynamics topological relationship of vehicle is directly embedded into CFD solver.The application fundamentally overcomes the drawbacks of ignoring coupling effect or existing data delay in traditional one-way coupling or joint simulation, so that the evaluation result of train aerodynamic safety under extreme conditions such as wind shear is more real and reliable.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of numerical simulation of high-speed trains, and particularly relates to a numerical simulation method for aerodynamic performance of a high-speed train under wind shear coupling with posture motion. BACKGROUND

[0002] With the rapid development of high-speed wheel-rail and maglev trains, the train running speed has increased from 350 km / h to 400-600 km / h or even higher. In this speed range, the interaction between the train and the surrounding air is significantly enhanced, and the fluid-structure coupling effect between the aerodynamic performance and the posture motion of the train body is increasingly prominent, becoming a key factor affecting the safety of train operation. Especially in areas where strong winds frequently occur, the wind shear phenomenon along the railway further exacerbates the instability of train operation. The design trend of higher running speed and lighter train body makes the aerodynamic safety risk of the train under the action of wind shear much higher than that of traditional high-speed trains, and the anti-overturning and anti-derailing technologies face unprecedented challenges.

[0003] Currently, there are mainly two methods for studying the aerodynamic-kinetic behavior of trains in wind environment:

[0004] One method is to analyze the aerodynamic performance and dynamic response separately, that is, to obtain the aerodynamic force through computational fluid dynamics (CFD) first, and then to input it as a load into a multibody dynamics (MBD) model for response calculation. This method ignores the feedback effect of the train body posture changes (such as roll and nodding) on the surrounding flow field structure, and cannot reflect the two-way coupling mechanism between aerodynamic motion, resulting in deviation in the evaluation of train safety in strong wind environment.

[0005] The other method uses the joint simulation technology of CFD and MBD, which alternately solves the aerodynamic force and the train body motion at each time step to achieve a certain degree of coupling simulation. However, this method usually relies on data transmission and collaborative calculation between multiple software platforms, and the process is complex and inefficient. Moreover, it is prone to problems such as grid distortion, data asynchronization, etc., which may lead to a decrease in calculation accuracy or even interruption, making it difficult to meet the demand for high-precision and high-efficiency simulation in engineering practice.

[0006] Therefore, there is still a lack of a numerical research method that can efficiently and stably realize the strong coupling of the flow field and the motion of the train body and bogie frame in a unified numerical framework, and accurately handle the complex wind field boundary such as wind shear. Especially in terms of the "fluid-elastic coupling" effect considering the elastic deformation of the flexible connecting components of the train body and the combined action of the posture motion, the existing methods still have obvious deficiencies. It is urgent and valuable to develop an integrated simulation method that can simultaneously capture the aerodynamic performance and the posture of the multibody motion, in order to improve the aerodynamic safety evaluation capability of high-speed trains under wind shear conditions. SUMMARY

[0007] In view of the above-mentioned defects in the prior art, the purpose of the present application is to provide a numerical simulation method for aerodynamic performance of high-speed trains under wind shear coupling attitude motion, which realizes synchronous solution of computational fluid dynamics and multi-body dynamics in a single software platform, and avoids the efficiency loss and synchronization problems caused by data exchange of multiple software in the traditional joint simulation method.

[0008] The present application solves the above technical problems by the following technical solutions: a numerical simulation method for aerodynamic performance of high-speed trains under wind shear coupling attitude motion, which realizes bidirectional coupling solution of flow field and train motion in a unified CFD framework, the method comprising:

[0009] a multi-domain computing environment including a background domain and an overlapping domain is constructed; the background domain is provided with a wind field boundary condition simulating wind shear; the overlapping domain envelopes all moving parts of the train and is coupled with the background domain through an overlapping grid interface to form a channel for dynamic exchange of flow field data;

[0010] in the CFD framework, each moving part is characterized by defining a three-dimensional continuum with physical properties, and its multi-body motion degrees of freedom are activated; the multi-body dynamics topology of the vehicle is directly embedded into the CFD solver by setting elastic connecting elements between the continua of each moving part;

[0011] the multi-domain computing environment is meshed, and a physical model is selected for solution calculation; during the solution process, aerodynamic parameters acting on the train and motion attitude parameters of each moving part are monitored and output in real time.

[0012] In this embodiment, the background domain is used to simulate the external wind field environment, and complex boundary conditions such as wind shear can be stably and accurately applied to the static background domain without frequent updating due to train motion. The overlapping domain is used to envelope and follow the train motion, and it only concerns the local flow field changes near the train. The present application separates the complex global wind field simulation and the complex local motion simulation by constructing a static background domain and a dynamic overlapping domain, so that both can be processed under optimal conditions, greatly improving the feasibility and accuracy of the calculation; the overlapping grid technology allows the overlapping domain to shuttle in the background domain, regardless of the attitude changes of the moving parts such as the car body and the bogie frame, the grid quality always remains in the initial high-quality state, completely solving the grid distortion problem caused by large motion, and fundamentally ensuring the stability and robustness of the calculation.

[0013] The overlapping grid interface provides the flow field information (such as velocity and pressure) of the background domain to the boundary of the overlapping domain as an inlet condition through interpolation; meanwhile, the flow field information calculated on the surface of the train in the overlapping domain is provided to the background domain. The dynamic interpolation enables the flow field information to be accurately exchanged in real time across different grid regions, physically simulating the disturbance of the moving train to the flow field and the reaction of the changed flow field to the moving train. The background domain and the overlapping domain are connected through the interface interpolation instead of adapting to the movement by distorting the grid, fundamentally eliminating the calculation collapse problem caused by the grid distortion.

[0014] The present application directly embeds the multi-body dynamics topological relationship of the vehicle (including the vehicle body continuum, the bogie continuum and the elastic connection element with physical properties) into the CFD solver, so that the fluid equation and the rigid motion equation are synchronously solved in the same mathematical solver, eliminating the overhead of inter-process communication and the time cost of data reading and writing, and significantly improving the calculation speed; avoiding the calculation interruption caused by asynchronous data transmission or interface error; in the iteration process of each time step, the flow field change and the vehicle motion are closely intertwined and mutually influenced, which can truly simulate the dynamic and mutually dependent physical process between the aerodynamic force and the motion of the vehicle body, bogie frame and the like, and is crucial for predicting the dynamic response of the vehicle under wind shear and other transient conditions.

[0015] Further, before constructing a multi-domain calculation environment including the background domain and the overlapping domain, the method further comprises constructing a simplified geometric model of the multi-formation train, and segmenting and numbering the head car, the intermediate car, the tail car, the bogie and the wind screen in the simplified geometric model into independent parts.

[0016] In the embodiment, the head car refers to the vehicle located at the front end of the train formation, the tail car refers to the vehicle located at the rear end of the train formation, and the intermediate car refers to the vehicle between the head car and the tail car. The head car directly faces the wind and bears the largest aerodynamic pressure; the tail car is in a complex wake region and bears significant fluctuating pressure and moment; the intermediate car is affected by the airflow after multiple interferences caused by the head car. Therefore, the force conditions of the head car, the intermediate car and the tail car are completely different.

[0017] Due to the completely different forces, the motion postures (such as roll and nod) of the head car, the intermediate car and the tail car under wind load are also different. The head car may first move and transmit the motion to the subsequent vehicles through the coupler and the wind screen. In order to define their physical properties (mass, inertia, etc.) respectively, set their suspension systems with the bogie respectively, and independently monitor the aerodynamic parameters and motion posture parameters of each car, the head car, the intermediate car and the tail car are segmented and numbered. In this way, the transmission and evolution process of the wind shear in the length direction of the train can be accurately analyzed.

[0018] Bogie is the component connecting car body and track, its motion is constrained by track, and it interacts with car body through suspension system (such as secondary suspension). Bogie has its own independent motion relative to car body. Windbreak is the flexible component connecting two car bodies, its main function is to deform elastically to adapt to the relative motion between car bodies. The purpose of dividing bogie and windbreak is to reconstruct a digital train geometry model which is both physically realistic and convenient for calculation when simulating. The model is a dynamic system composed of multiple components with mass, inertia and elastic connection, so as to accurately simulate the influence of airflow on train motion under wind shear and the two-way fluid-structure coupling effect of train motion changing airflow state.

[0019] Further, after the component division and numbering, each component is also simplified, including:

[0020] The surface of the car body is smoothed to remove non-aerodynamic key features;

[0021] The structure of the windbreak is simplified to only retain its basic groove shape, and it is set as a flexible deformation area;

[0022] The bogie is truncated to form a flat surface at the top.

[0023] In this embodiment, the surface of the car body is smoothed to remove non-key geometric features such as pantograph mounting seat, door and window groove, small air vent, etc. which have little effect on the macroscopic aerodynamic characteristics under high-speed crosswind conditions. This avoids generating a large number of small grids with low quality, reduces the total number of grids, improves the quality of surface grids and reduces the computational complexity. To prevent the geometric boundary of the car body from penetrating or colliding with the bogie component below when the car body undergoes large attitude changes (such as roll) in simulation, causing computational interruption, the bogie is truncated to retain only the main structure of the bogie and remove the upper part connected to the car body. Truncation ensures the stability of the grid when the car body undergoes large attitude motion, avoiding computational interruption. Simplification helps to concentrate computational resources on capturing the main flow changes caused by the macroscopic motion of the car body, bogie frame and other moving components and the overall deformation of the windbreak, rather than being disturbed by the flow of minor details.

[0024] Further, the background domain is a regular cuboid flow domain, the size of which ensures that the ratio of the maximum cross-sectional area of the train to the cross-sectional area of the background domain in the incoming flow direction is less than 15%.

[0025] In this embodiment, by limiting the ratio of the maximum cross-sectional area of the train to the cross-sectional area of the background domain in the incoming flow direction (i.e. blockage ratio), the disturbance of the wall surface to the flow field is minimized.

[0026] Further, the wind field boundary condition is set as: the front and windward side of the head car is a velocity inlet, the rear and leeward side of the tail car is a pressure outlet, the top is a symmetry boundary, and the bottom is a slip wall.

[0027] The wind speed curve generated by the measured wind field parameters is loaded at the velocity inlet.

[0028] In this embodiment, the front and windward side of the head car is set as a velocity inlet, so that the wind speed and direction of the wind shear can be accurately defined; the rear and leeward side of the tail car is set as a pressure outlet, so that the complex vortex shedding and wake development process behind the train and on the leeward side can be truly simulated; the top is set as a symmetry boundary and is set at an appropriate height above the car body, so that the complete development of the flow field is ensured; the bottom is set as a slip wall, which is more in line with the actual situation and can better balance the calculation accuracy and grid resource consumption. The wind speed curve generated by the measured wind field parameters is loaded at the velocity inlet, so that the real simulation of the wind shear along the railway is realized.

[0029] Further, a gap of a preset number of grid units is maintained between the boundary of the overlap domain and the boundary of the background domain, and the close contact and replacement hole cutting functions are enabled in the setting of the overlap grid interface, so that the grid relationship between the bottom of the car body and the track surface in the narrow area is automatically and stably handled.

[0030] Further, the elastic connecting element includes an elastic damping system for simulating the suspension action between the car body continuum and the bogie continuum; the stiffness and damping coefficient of the elastic damping system are set according to the secondary suspension parameters of the vehicle;

[0031] The vertical spring for simulating the secondary suspension is provided with an initial compression amount, and the initial support force provided by the initial compression amount is balanced with the gravity of the corresponding car body, so as to ensure that the model is in the correct static equilibrium initial state under the gravitational field;

[0032] The anti-roll torsion bar is simulated by defining a torque acting on the car body continuum, and the torque is proportional to the roll angle of the car body continuum;

[0033] The anti-snake damper is simulated by defining a plurality of pairs of force couples acting on the car body continuum, and the force couples are proportional to the yaw angle of the car body continuum.

[0034] Further, the grid division adopts a cut body grid, and the bogie area and the bottom area of the car body are subjected to local encryption processing;

[0035] The car body surface grid is taken as a reference, and the encryption is performed layer by layer outwardly;

[0036] A nested encryption area similar in shape to the component calculation domain is set in each component area, and the size of the encryption area gradually increases from inside to outside;

[0037] The grid size of the background domain and the overlap domain at the interface is consistent, so as to ensure the accuracy and calculation stability of flow field interpolation between the background domain and the overlap domain.

[0038] Based on the same concept, the application also provides an electronic device, comprising a memory, a processor and a computer program or instructions stored in the memory, wherein the processor executes the computer program or instructions to realize the high-speed train aerodynamic performance numerical simulation method for coupled attitude motion under wind shear.

[0039] Based on the same concept, the application also provides a computer readable storage medium, which stores a computer program or instructions, and the computer program or instructions are executed by a processor to realize the high-speed train aerodynamic performance numerical simulation method for coupled attitude motion under wind shear.

[0040] Compared with the prior art, the application has the following beneficial effects:

[0041] The application can accurately capture the complete physical feedback process of "aerodynamic load causing the motion of the vehicle body and other moving components --> the motion of the vehicle body and other moving components changing the flow field --> the new flow field acting on the aerodynamic load", and fundamentally overcomes the drawbacks of ignoring the coupling effect or existing data delay in the traditional one-way coupling or joint simulation, so that the evaluation result of the train aerodynamic safety (such as anti-overturning and anti-derailment performance) under extreme working conditions such as wind shear is more real and reliable.

[0042] The application adopts the architecture of "static background domain + dynamic overlap domain", and uses the overlap grid technology to process large displacement motion, which completely avoids the calculation interruption problem of grid distortion caused by large rotation (such as roll) of the vehicle body and other moving components in the traditional dynamic grid, ensures that the grid quality remains unchanged during the simulation of complex attitude change process, and thus can stably and robustly complete the entire transient simulation process, solving the technical problem that has long plagued the numerical simulation in this field.

[0043] The application integrates aerodynamic analysis and dynamic analysis in a single software platform, eliminating the data exchange, interface configuration and waiting time required by multi-software joint simulation. This integrated process not only simplifies the operation and reduces the use threshold, but also improves the calculation efficiency by orders of magnitude due to the avoidance of inter-process communication overhead, so that long-time and multi-condition transient analysis becomes feasible in engineering practice, greatly promoting design iteration and parameter optimization. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the present application, the drawings needed to be used in the following embodiment description will be briefly introduced. Obviously, the drawings in the following description are only one embodiment of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0045] Figure 1 is a flow chart of the high-speed train aerodynamic performance numerical simulation method for coupling attitude motion under wind shear in the embodiment of the present application;

[0046] Figure 2 is a velocity field cloud chart of the train body deflecting 2° to the windward side in the embodiment of the present application;

[0047] Figure 3 is a velocity field cloud chart of the train body deflecting 2° to the leeward side in the embodiment of the present application;

[0048] Figure 4 is a velocity field cloud chart of the train body without deflection in the embodiment of the present application;

[0049] Figure 5 is a train body attitude angle output curve in the embodiment of the present application;

[0050] Figure 6 is a train body lateral acceleration output curve in the embodiment of the present application;

[0051] Figure 7 is an aerodynamic force output curve in the embodiment of the present application;

[0052] Figure 8 is an aerodynamic moment output curve in the embodiment of the present application. DETAILED DESCRIPTION

[0053] The technical solutions in the present application will be described clearly and completely in the following description in combination with the drawings in the embodiment of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort belong to the protection scope of the present application.

[0054] The technical solutions of the present application will be described in detail in the following specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes can not be described in some embodiments.

[0055] Embodiment one

[0056] Figure 1 The flow chart of the high-speed train aerodynamic performance numerical simulation method for coupling attitude motion under wind shear provided by the present application is shown. As shown in the figure, Figure 1As shown, the numerical simulation method comprises the following steps:

[0057] Step 1: Construct a simplified geometric model of a multi-formation train, and divide the head car, intermediate car, tail car, bogie and wind screen in the simplified geometric model into independent parts and number them.

[0058] According to a certain formation train model, a simplified geometric model of the train is constructed, the head car, intermediate car, tail car, bogie and wind screen in the simplified geometric model are divided out to form independent parts, so as to facilitate subsequent independent definition of attributes, setting of motion and application of monitoring.

[0059] Step 2: Simplify each part.

[0060] In order to concentrate calculation resources on capturing the main flow field changes caused by the macro motion of the car body and the overall deformation of the wind screen, and not be disturbed by the secondary details of the flow, each part is simplified. Specifically, the car body surface is smoothed, the pantograph mounting seat, door and window grooves, small air vents and other non-critical geometric features that have little effect on the macro aerodynamic characteristics under high-speed crosswind conditions are removed, avoiding the generation of a large number of low-quality small grids and improving the grid quality. The structure of the wind screen is simplified, only the groove shape of the capsule-type wind screen is retained, the internal sealing elements and other complex details are ignored, and it is set as a flexible deformation area. In order to prevent interference between the rotating car body and the fixed bogie during the change of the train attitude, the upper complex structure at the connection between the bogie and the car body is cut off, the top of the bogie is formed into a flat surface, and geometric interference between the car body and the bogie during the movement of the car body is prevented.

[0061] In this embodiment, the nose end of the head car is taken as the coordinate origin, and a global reference coordinate system is established, which provides a unified reference for subsequent grid division, motion definition and result analysis.

[0062] Step 3: Construct a multi-domain computing environment including a background domain and an overlapping domain, and construct an overlapping network interface between the overlapping domain and the background domain to form a channel for dynamic exchange of flow field data.

[0063] After the model is constructed and processed, a computing environment for numerical simulation needs to be created. The present application adopts a multi-domain computing environment combining a background domain and an overlapping domain to efficiently and stably simulate the interaction between the train and the flow field under wind shear.

[0064] The background domain is used to simulate the macro atmospheric environment and wind shear scene in which the train is located, and the construction steps are as follows:

[0065] A regular cuboid computational domain is created outside the simplified geometric model (i.e. train), which completely envelops the entire train and reserves sufficient space in front of and behind the train (flow direction), left and right (transverse direction) and top (vertical direction) to ensure the stable development of the incoming flow and wake flow. The size of the background domain should meet the requirement that the blockage ratio (i.e. the ratio of the maximum cross-sectional area of the train to the cross-sectional area of the flow field in the incoming flow direction) is less than 15% to minimize the wall effect.

[0066] In order to accurately simulate the wind shear scenario, the wind field boundary conditions are set as follows:

[0067] Velocity Inlet: Set in the flow field boundary in front of the head car (simulate the incoming flow of the train advancing) and the flow field boundary on the windward side of the train (simulate the far-field incoming flow, which can directly embed the measured parameters of the wind field to reproduce the real wind field). The inlet position should be far enough from the train to ensure that the incoming flow can enter the calculation environment uniformly. The average wind speed, wind direction, turbulence intensity, gust factor, fluctuating wind speed power spectrum and other wind field parameters of the wind field are obtained by field measurement; the wind speed curve along the railway is generated according to these wind field parameters; the wind speed curve is loaded into the velocity inlet in the form of an editable data table, realizing the real simulation of wind shear.

[0068] Pressure Outlet: Set in the flow field boundary behind the tail car and the far end boundary on the leeward side of the train to ensure that the wake flow can fully evolve and tend to be stable. In this embodiment, the reference value of the outlet pressure is set to the environmental pressure condition.

[0069] Symmetry Plane: Set at the top of the calculation environment and at an appropriate height above the car body to ensure complete development of the flow process.

[0070] Slip Wall: Set at the bottom of the calculation environment, corresponding to the ground and the track. The slip wall simulates the carrying effect of the ground on the air, while considering the actual height of the track relative to the ground.

[0071] In order to simulate the forward motion of the train, the fluid region of the entire background domain is set as a motion reference system with the same size and opposite direction as the motion speed of the train.

[0072] The overlap domain is a local area that tightly envelops the moving parts of the train and moves with the train, which is the key to realizing the attitude coupling. The construction process of the overlap domain is as follows:

[0073] A regular cuboid region is created, which completely envelops all moving parts of the train (such as the car body, bogie frame, etc.), i.e. forms the overlap domain.

[0074] In the embodiment, a preset number of grid cells needs to be kept between the boundary of the overlap domain and the boundary of the background domain, which serves as a buffer for data interpolation and is the basis for ensuring the accurate transmission of flow field information between the overlap domain and the background domain.

[0075] In order to realize accurate simulation of the flow field under large-range posture motion of the vehicle body, the overlap domain and its interface need to be correctly defined. Since the core of the simulation is the posture change of the vehicle body relative to the bogie (such as roll, head swing, nod, lateral shift, vertical shift, etc.), the motion of the vehicle body relative to the bogie is much larger than the motion of the bogie relative to the track plane, therefore, the motion reference of the overlap domain is set on the track plane in the present application, so as to simplify the motion reference and more effectively capture the main motion postures. In the specific embodiment of the present application, region division is performed through Boolean subtraction operation:

[0076] The overlap domain geometry is subtracted from the vehicle body surface, and the generated space is the calculation region of the flow field around the vehicle body during motion; the background domain geometry is subtracted from the track model surface, and the generated space is the background flow field region outside the track; the two components (calculation region and background flow field region) generated through subtraction operation and their surfaces are newly created into a CFD calculation region through the region assignment function in the software. The boundary of the overlap domain is set as an overlap grid, and an overlap grid interface (Overset Interface) is newly created between the overlap domain and the background domain, which serves as the boundary for flow field data interpolation and exchange between the overlap domain and the background domain.

[0077] Considering that the distance between the bottom of the train and the track is small, the following advanced options are enabled in the setting of the overlap grid interface to ensure the stability and calculation accuracy of the interpolation:

[0078] Close contact: optimize the grid connection processing at narrow gaps.

[0079] Prism layer contraction: automatically adjust the boundary layer grid when the gap is extremely small to prevent grid failure.

[0080] Instead of hole cutting: automatically mark the background domain grid cells that are completely blocked by solids as "hole" cells that do not participate in calculation.

[0081] This series of settings can effectively avoid numerical instability caused by grid distortion during the motion of the vehicle body and other moving parts, and is a key technical measure to ensure the smooth running of the coupled simulation.

[0082] Step 4: In the CFD framework, each moving part (such as the vehicle body and the bogie frame) is represented by defining a three-dimensional continuum with physical properties, and the multi-body motion degrees of freedom are activated; the multi-body dynamics topology relationship of the vehicle is directly embedded into the CFD solver by setting elastic connection elements between the continua of each moving part.

[0083] Enable the fluid-structure coupling solution function in the CFD software. Create a new motion form (for example, six degrees of freedom motion or motion following a specified law), and specify the motion type of the overlapping domain calculation area as the newly created motion form, so that the motion of the train in the overlapping domain and its internal envelope can be defined as a movable whole, realizing the coupling of the background domain flow field and the motion of the overlapping domain.

[0084] In the sub-option of the fluid-structure coupling function, a three-dimensional continuum is created for each moving component in the consist, for example, a three-dimensional continuum is created for each car body (head car, intermediate car and tail car), and is named according to its number (such as body_1, body_2, …). The body surface of each moving component continuum is set as the outer surface of the corresponding component in the overlapping domain, and the physical properties such as mass and moment of inertia of each moving component continuum are accurately input in the attributes of each moving component continuum, which are derived from vehicle design data. The body motion option of each moving component continuum is set to multi-body motion, and the key motion degrees of freedom are activated according to the requirements of crosswind stability analysis. In this embodiment, for the car body, at least the roll and lateral translation degrees of freedom are enabled.

[0085] The mechanical interaction between the car body continuum and the car body continuum, and between the car body continuum and the bogie continuum is simulated by using a spring-damper system in the body coupling. For example, a plurality of spring dampers are established between the car body continuum and the corresponding bogie continuum to simulate the effect of the secondary suspension, and the number, spatial distribution, stiffness and damping coefficient of the spring dampers are consistent with the design parameters of the secondary suspension of the actual vehicle. In this embodiment, the vertical spring simulating the secondary suspension needs to be set with an initial compression amount, so that the initial support force provided by it is exactly balanced with the gravity of the supported car body, ensuring that the model is in the correct static equilibrium initial state under the gravity field.

[0086] The effect of the anti-roll torsion bar is simulated by defining a torque acting on the car body continuum, and the size of the torque is proportional to the roll angle of the car body; the effect of the anti-snake shock absorber is simulated by defining four pairs of force couples acting on the car body continuum, and the force couples are proportional to the yaw angle of the car body continuum. At the coupling connection (such as a hinge) between adjacent car bodies, the relative motion relationship between the car bodies is constrained, and the windscreen is set as a flexible deformation area, thereby simulating the overall dynamic behavior of the long and large consist train.

[0087] The "embedded fluid-structure coupling" numerical framework constructed by the present application has universality. By adjusting the vehicle dynamics parameters (mass, moment of inertia, suspension stiffness, etc.) and the flow field boundary conditions, this method can be widely applied to the aerodynamic elastic mechanics problems of different consists, different car types, high-speed trains and other vehicles, and has good universality and expandability.

[0088] Step 5: Grid the multi-domain computing environment and select a physical model for solving calculation; in the solving process, synchronously monitor and output the aerodynamic parameters acting on the train and the motion posture parameters of the moving parts.

[0089] To control the consumption of computing resources under the premise of ensuring calculation accuracy, a structured grid division strategy needs to be adopted for the multi-domain computing environment (computing domain). In this embodiment, the background domain and the overlapping domain are discretized using a cut body network.

[0090] In the grid division process, different grid sizes are used for different parts to balance accuracy and efficiency: because the bogie area has a complex geometric structure and the surrounding flow field has strong vortex, a more fine surface grid is applied; the car body surface is relatively smooth, a relatively coarse surface grid is used, and the car body surface grid is used as a benchmark to gradually increase the encryption layer outward. In the area of each part, a nested encryption area similar in shape to the computing domain of the part is set, and the size of the encryption area gradually increases from inside to outside. Body control is applied in the background domain automatic grid to achieve hierarchical grid encryption. The main area of the background domain uses a relatively sparse grid to reduce the overall number of grids while ensuring calculation accuracy.

[0091] The bottom of the car body, especially the area around the bogie, has the most complex flow field changes, so local encryption needs to be applied in this area, and the encryption range needs to have sufficient coverage in the length direction of the train to capture key flow structures. To accurately capture the development process of vortex structures near the train surface, multiple layers of boundary layer grids are applied to all car body walls, so that the boundary layer flow characteristics can be fully analyzed.

[0092] In the grid generation process, the slenderness ratio of the grid is controlled to be less than 2:1 to maintain high grid quality. At the same time, the grid size at the interface between the overlapping domain and the background domain should be kept consistent as much as possible to achieve stable coupling between the two domains and effective transfer of flow field information.

[0093] To accurately simulate the complex flow around the train under wind shear and its coupling with the motion of the car body, the physical model and numerical method for solving need to be configured:

[0094] The N-S equation based on the implicit unsteady SST k-ω turbulence model is selected to simulate the flow field around the train to prevent flow separation caused by model stress loss and grid problems. This approach combines the advantages of the standard k-ω model in near-wall region calculation and the k-ω model in far-field free flow, which can more accurately predict the flow separation point and separation zone range, effectively preventing the distortion of separated flow simulation caused by inaccurate model stress prediction.

[0095] In this example, the fluid physical properties are set to constant density, i.e., incompressible flow, to simplify the control equations and significantly improve computational efficiency. The detached eddy solver is chosen to be optimized for incompressible flow and can effectively handle a wide range of flow separation phenomena.

[0096] Activate the turbulence option in the model list to enable the above-mentioned SST k-ω turbulence model, while enabling the gravity model and setting the gravitational acceleration.

[0097] After completing all the preprocessing settings, the solver parameters, data monitoring and calculation tasks need to be finally configured to start the transient coupled calculation. In the solver control panel, the following key parameters are defined to control the advancement of the calculation:

[0098] Time step: determined according to the characteristic frequency of wind shear and the response frequency of train motion, needs to be small enough to capture key transient physical processes.

[0099] Total duration: set a long enough simulation time to ensure that the dynamic response of the train under the action of wind shear reaches stability or completes a complete evolution period.

[0100] Maximum number of iterations per time step: set the maximum number of iterations of the solver in each time step to ensure that the equation residual in that time step converges sufficiently.

[0101] Time discretization format: use second-order implicit format for time discretization to improve the numerical accuracy of time advancement.

[0102] In order to implement the tracking of the calculation state and capture key results, the corresponding monitors need to be set:

[0103] Force and moment monitor: create a monitor to record the drag force, lateral force, lift force, overturning moment, nodding moment, and shaking moment of the whole vehicle and each component (such as each car body and bogie) in real time.

[0104] Motion attitude parameter monitor: create a monitor to record the roll angle, nodding angle, shaking angle, lateral displacement, vertical displacement, speed, angular velocity, acceleration, and angular acceleration of each moving component (such as the car body) in real time.

[0105] Field variable monitoring: monitor the pressure, velocity and other flow field parameters at key positions in the entire calculation domain.

[0106] Scene recording: enable the Scene recording function to save the transient data of flow field contour maps, vector diagrams and vehicle motion attitude, which can be used for subsequent animation generation and detailed post-processing analysis.

[0107] After completing all the above settings, perform the following operations to start the calculation:

[0108] Based on the established grid strategy, the background domain and the overlapping domain are generated; the flow field is initialized by using appropriate initial conditions (such as uniform inflow); the complete simulation model is submitted to the solver; the solver will automatically perform the calculation, and at each time step, the flow field control equation and the multi-body motion equation are solved synchronously to realize the fluid-structure coupling simulation.

[0109] Step 6: result analysis and iterative optimization

[0110] After the simulation calculation is completed, the output data is extracted and analyzed by using the post-processing function of the software to evaluate the comprehensive performance of the high-speed train under the wind shear environment.

[0111] The attitude angle (roll angle, nodding angle, shaking angle) and displacement (lateral displacement, vertical displacement), acceleration, speed, etc. of each car body are extracted to obtain the time-varying curve. By analyzing these curves, the dynamic stability of the train under the wind shear excitation is evaluated, and the key motion mode (such as car body roll) and its amplitude and frequency characteristics are identified, which provides a direct basis for judging the driving safety risk (such as overturning and derailment tendency).

[0112] Visual analysis of flow field data at a specific time or time average:

[0113] Pressure distribution cloud map: used to identify the high-pressure impact area and low-pressure separation area on the surface of the car body, and analyze the distribution law of the aerodynamic load.

[0114] Velocity vector and streamline diagram: used to reveal the flow structure around the train, the generation, evolution and shedding process of vortex, especially the unsteady characteristics of the wake region.

[0115] By combining the flow field structure, the physical mechanism of the generation of specific aerodynamic load can be understood in depth.

[0116] The time series data of the aerodynamic force and moment (drag force, lateral force, lift force, overturning moment, nodding moment, shaking moment) of the whole vehicle and key components are extracted, the mean value, fluctuation amplitude and dominant frequency are analyzed, and the transient and statistical influence of the wind shear on the aerodynamic performance of the train is quantitatively evaluated.

[0117] Based on the analysis results of the above-mentioned dynamic response, flow field structure and aerodynamic load, the complete correlation of "wind field excitation-aerodynamic load-vehicle motion" is established. The present application can accurately simulate the aerodynamic characteristics and multi-body motion attitude of the high-speed train under the wind shear, and the quantitative analysis conclusion can provide effective numerical basis and support for the wind-resistant stability design, suspension parameter optimization and operation safety evaluation of the train.

[0118] Figures 2 to 8 The numerical simulation results of the aerodynamic performance of the high-speed train coupled with the attitude motion under the wind shear are shown, wherein, Figures 2 to 4 is the velocity field cloud map of the car body at different deflection angles,Figure 5 and Figure 6 output curve of vehicle body motion posture parameter, Figure 7 and Figure 8 output curve of aerodynamic load. It can be known from Figures 2 to 8 that the present application can directly reveal the two-way dynamic coupling interaction between the vehicle body posture motion and the surrounding flow field, including the changes of pressure field, velocity field (such as Figures 2 to 4 ), and the motion posture parameters (such as Figure 5 and Figure 6 ) of the vehicle body and the aerodynamic load response (such as Figure 7 and Figure 8 ) of the whole vehicle under the coupling effect.

[0119] In comparison, the existing method can generally only analyze the one-way influence of aerodynamics on the vehicle body posture motion, and cannot capture the reverse interference effect of the vehicle body motion on the flow field. Therefore, the present application realizes the true two-way fluid-solid coupling analysis, while the existing method only involves the one-way action research of aerodynamics and train dynamics.

[0120] The present application can synchronously output high-precision flow field details (such as pressure field, velocity field), vehicle motion posture parameters (such as posture angle, velocity, acceleration, etc.) and aerodynamic load response (such as aerodynamic force, aerodynamic moment). This data synchronization enables researchers to clearly establish the causal relationship between “flow field excitation-aerodynamic load-motion response”, not only can predict the phenomenon, but also can deeply understand the internal physical mechanism, thereby providing direct and strong theoretical basis and numerical guidance for the wind resistance design (such as shape optimization, suspension parameter matching) of the train.

[0121] Embodiment two

[0122] The embodiment of the present application also provides an electronic device, which comprises a memory, a processor and a computer program or instruction stored in the memory, and the processor executes the computer program or instruction to realize the high-speed train aerodynamic performance numerical simulation method of coupled posture motion under wind shear in the embodiment one of the present application.

[0123] Although not shown, the electronic device includes a processor that can perform various appropriate operations and processes according to programs and / or data stored in a read-only memory (ROM) or programs and / or data loaded from a storage section into a random access memory (RAM). The processor can be one multi-core processor or can include a plurality of processors. In some embodiments, the processor can include a general-purpose main processor and one or more special-purpose co-processors, such as a central processing unit, a graphics processing unit (GPU), a neural processing unit (NPU), a digital signal processor (DSP), and the like. In the RAM, various programs and data required for device operations are also stored. The processor, the ROM, and the RAM are connected to each other through a bus. An input / output (I / O) interface is also connected to the bus.

[0124] The above processor and memory are used together to execute programs / instructions stored in the memory, which, when executed by a computer, can implement the methods, steps, or functions described in the above embodiments.

[0125] Although not shown, the present embodiment also provides a computer-readable storage medium having a computer program or instructions stored thereon, which, when executed by a processor, implements the method for numerical simulation of aerodynamic performance of a high-speed train in a wind shear decoupling attitude motion in the first embodiment of the present application.

[0126] The computer-readable storage medium includes permanent and non-permanent, removable and non-removable media, which can be implemented by any method or technology to store information. The information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassette, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information accessible by a computing device. According to the definition herein, computer-readable media does not include transitory media such as modulated data signals and carriers.

[0127] The above only discloses specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or modifications within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A numerical simulation method of aerodynamic performance of high-speed trains under the coupling of attitude motion and wind shear, for realizing bidirectional coupling solution of flow field and train motion in a unified CFD framework, characterized in that, The method comprises: constructing a multi-domain computing environment comprising a background domain and an overlapping domain; the background domain is provided with wind field boundary conditions simulating wind shear; the overlapping domain envelops all moving parts of the train and is coupled with the background domain through an overlapping grid interface to form a channel for dynamic exchange of flow field data; in the CFD framework, each moving part is represented by defining a three-dimensional continuum with physical properties and activating its multi-body motion degrees of freedom; the multi-body dynamics topology of the vehicle is directly embedded into the CFD solver by setting elastic connecting elements between the continua of each moving part; the multi-domain computing environment is meshed and a physical model is selected for solving and calculation; during the solving process, the aerodynamic parameters acting on the train and the motion posture parameters of each moving part are monitored and output in real time.

2. The method according to claim 1, wherein, Before constructing a multi-domain computing environment comprising a background domain and an overlapping domain, the method further comprises constructing a simplified geometric model of a multi-formation train, and dividing the head car, intermediate car, tail car, bogie and wind screen in the simplified geometric model into independent parts and numbering them.

3. The method according to claim 2, wherein, After part segmentation and numbering, each part is further simplified, including: smooth the surface of the car body to remove non-aerodynamic key features; simplify the structure of the wind screen and only keep its basic groove shape, and set it as a flexible deformation area; top cut the bogie to form a flat surface on the top.

4. The method according to claim 1, wherein, The background domain is a regular cuboid flow domain, and the size ensures that the ratio of the maximum cross-sectional area of the train to the cross-sectional area of the background domain in the incoming flow direction is less than 15%.

5. The method according to claim 1, wherein The wind field boundary conditions are set as follows: the front and windward side of the head car are velocity inlets, the rear and leeward side of the tail car are pressure outlets, the top is a symmetric boundary, and the bottom is a slip wall; load the wind speed curve generated from the measured wind field parameters at the velocity inlet.

6. The method of claim 1, wherein the method further comprises: The boundary of the overlapping domain and the boundary of the background domain maintain a gap of a predetermined number of grid elements, and the close contact and replacement hole cutting functions are enabled in the setting of the overlapping grid interface.

7. The method according to claim 1, wherein The elastic connecting element includes an elastic damping system for simulating the suspension action between the car body continuum and the bogie continuum; the stiffness and damping coefficient of the elastic damping system are set according to the secondary suspension parameters of the vehicle; the vertical spring for simulating the secondary suspension is provided with an initial compression amount, and the initial support force provided by the initial compression amount is balanced with the gravity of the corresponding car body; an anti-roll torsion bar is simulated by defining a torque acting on the car body continuum, and the torque is proportional to the roll angle of the car body continuum; an anti-snake damper is simulated by defining a plurality of pairs of force couples acting on the car body continuum, and the force couples are proportional to the yaw angle of the car body continuum.

8. The method according to any one of claims 1 to 7, wherein the method is characterized by, The grid division adopts cut-body grid and performs local encryption processing on the bogie area and the bottom area of the car body; encrypt layer by layer outward based on the car body surface grid; nested encryption areas similar in shape to the computing domain of each part are set in the area of each part, and the size of the encryption area gradually increases from inside to outside; the grid size of the background domain and the overlapping domain at the interface is consistent.

9. An electronic device comprising a memory, a processor, and a computer program or instructions stored on the memory, wherein the computer program or instructions, when executed by the processor, cause the electronic device to perform the method of any one of claims 1-8. The processor executes the computer program or instruction to realize the high-speed train aerodynamic performance numerical simulation method of coupled attitude motion under wind shear as claimed in any one of claims 1-8.

10. A computer readable storage medium having stored thereon a computer program or instructions, characterized in that, The computer program or instruction is executed by the processor to realize the high-speed train aerodynamic performance numerical simulation method of coupled attitude motion under wind shear as claimed in any one of claims 1-8.

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