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

Abstract

The invention discloses a numerical simulation method for aerodynamic performance of a high-speed train coupled with attitude motion under wind shear, and relates to the technical field of numerical simulation of high-speed trains. The method comprises the following steps: constructing a multi-domain computing environment comprising a background domain and an overlapping domain; wind field boundary conditions for simulating wind shear are set in the background domain; the overlapping domain envelopes all moving parts of the train and is coupled with the background domain through an overlapping grid interface; in the CFD framework, representing each moving part by defining a three-dimensional continuum with a physical attribute, and activating the multi-body motion degree of freedom of the moving part; elastic connecting elements are arranged between continuous bodies of all moving parts, and the multi-body dynamics topological relation of the vehicle is directly embedded into a CFD solver. According to the method, the defect that in traditional one-way coupling or joint simulation, the coupling effect is ignored or data delay exists is overcome fundamentally, and the evaluation result of the train pneumatic safety under the extreme working conditions such as wind shear is more real and reliable.

Description

Technical Field

[0001] This invention belongs to the field of high-speed train numerical simulation technology, and in particular relates to a numerical simulation method for the aerodynamic performance of high-speed trains under coupled attitude motion under wind shear. Background Technology

[0002] With the rapid development of high-speed rail, maglev, and other higher-speed train technologies, train speeds have increased from 350 km / h to 400-600 km / h and even higher. Within this speed range, the interaction between the train and the surrounding air is significantly enhanced, and the fluid-structure interaction effect between aerodynamic performance and vehicle attitude motion becomes increasingly prominent, becoming a key factor affecting train safety. Especially in areas with frequent strong winds, wind shear along railway lines further exacerbates the instability of train operation. The design trend towards higher operating speeds and lighter vehicle weights means that the aerodynamic safety risks of trains under wind shear are far higher than those of traditional high-speed trains, posing unprecedented challenges to technologies such as anti-tipping and anti-derailment.

[0003] Currently, there are two main approaches to studying the aerodynamic behavior of trains in windy environments: One approach separates aerodynamic performance from dynamic response analysis. This involves first obtaining aerodynamic forces through computational fluid dynamics (CFD) and then inputting them as loads into a multibody dynamics (MBD) model for response calculation. This method ignores the feedback effect of vehicle attitude changes (such as roll and pitch) on the surrounding flow field structure, failing to reflect the two-way coupling mechanism between aerodynamics and motion, leading to biases in driving safety assessments under high wind conditions.

[0004] Another type of simulation technique uses a combination of CFD and MBD, which achieves a certain degree of coupled simulation by alternately solving aerodynamic forces and vehicle motion in each time step. However, this method usually relies on data transfer and collaborative computing between multiple software platforms, which is complex, inefficient, and prone to decreased computational accuracy or even interruption due to problems such as mesh distortion and data asynchrony, making it difficult to meet the needs of high-precision and high-efficiency simulation in engineering practice.

[0005] Therefore, current technologies lack a numerical research method that can efficiently and stably realize the strong motion coupling between the flow field and moving components such as the car body and bogie frame within a unified numerical framework, and accurately handle complex wind field boundaries such as wind shear. In particular, existing methods still have significant shortcomings in considering the "fluid-structure-elastomer coupling" effect under the combined action of elastic deformation and attitude motion of the car body's flexible connecting components. Developing an integrated simulation method that can simultaneously capture aerodynamic performance and multi-body motion attitude is urgently needed and of great value for improving the aerodynamic safety assessment capabilities of higher-speed trains under wind shear conditions. Summary of the Invention

[0006] To address the aforementioned deficiencies in existing technologies, the present invention aims to provide a numerical simulation method for the aerodynamic performance of high-speed trains under coupled attitude motion under wind shear. By achieving simultaneous solution of computational fluid dynamics and multibody dynamics within a single software platform, this method avoids the efficiency loss and synchronization problems caused by data exchange between multiple software programs in traditional co-simulation methods.

[0007] This invention solves the above-mentioned technical problems through the following technical solution: a numerical simulation method for the aerodynamic performance of high-speed trains under coupled attitude motion under wind shear, used to achieve bidirectional coupled solution of flow field and train motion within a unified CFD framework, the method comprising: A multi-domain computing environment is constructed, comprising a background domain and an overlapping domain. The background domain is configured with wind field boundary conditions simulating wind shear. The overlapping domain encompasses all moving parts of the train and is coupled to the background domain through the overlapping mesh interface, forming a channel for dynamic exchange of flow field data. Within the CFD framework, each moving part is characterized by defining a three-dimensional continuum with physical properties, and its multibody motion degrees of freedom are activated; by setting elastic connecting elements between the continuums of each moving part, the multibody dynamics topology of the vehicle is directly embedded into the CFD solver. The multi-domain computing environment is meshed and a physical model is selected for solution calculation. During the solution process, the aerodynamic parameters acting on the train and the motion attitude parameters of each moving component are monitored and output in real time.

[0008] In this embodiment, the background domain is used to simulate the external wind field environment. Complex boundary conditions such as wind shear can be stably and accurately applied to the static background domain without frequent updates due to train movement. The overlapping domain is used to enclose and follow the train's movement, focusing only on local flow field changes near the train. This invention separates the complex global wind field simulation from the complex local motion simulation by constructing a static background domain and a dynamic overlapping domain, allowing both to be processed under optimal conditions, greatly improving the feasibility and accuracy of the calculation. The overlapping mesh technology allows the overlapping domain to traverse within the background domain. Regardless of the attitude changes of moving components such as the car body and bogie frame, the mesh quality remains at its initial high quality, completely solving the mesh distortion problem caused by large movements and fundamentally ensuring the stability and robustness of the calculation.

[0009] The overlapping mesh interface interpolates flow field information (such as velocity and pressure) from the background domain and provides it to the boundary of the overlapping domain as an entry condition. Simultaneously, it "feeds back" the flow field information calculated from the train surface within the overlapping domain to the background domain. This dynamic interpolation allows flow field information to be accurately exchanged in real time across different mesh regions, realistically simulating the disturbance of the flow field by a moving train and the reaction of the changed flow field to the moving train. The background domain and the overlapping domain are connected through interface interpolation, rather than by distorting the mesh to adapt to motion, fundamentally eliminating computational crashes caused by mesh distortion.

[0010] This invention directly embeds the multibody dynamics topology of a vehicle (including the vehicle body continuum, bogie continuum, and elastic connecting elements with physical properties) into the CFD solver, enabling the fluid equations and rigid motion equations to be solved synchronously within the same mathematical solver. This eliminates the overhead of inter-process communication and the time cost of data reading and writing, significantly improving the computation speed. It also avoids computational interruptions caused by asynchronous data transmission or interface errors. In each iteration of time step, the flow field changes and vehicle motion are closely intertwined and mutually influential, which can realistically simulate the dynamic and interdependent physical processes between aerodynamic forces and the motion of the vehicle body, bogie frame, etc., which is crucial for predicting the dynamic response of vehicles under transient conditions such as wind shear.

[0011] Furthermore, before constructing a multi-domain computing environment that includes a background domain and an overlapping domain, the method also includes constructing a simplified geometric model of a multi-train train and dividing the head car, middle car, tail car, bogie, and windshield in the simplified geometric model into independent components and numbering them.

[0012] In this embodiment, the lead car refers to the car at the very front of the train formation, the tail car refers to the car at the very back of the train formation, and the middle car refers to the car between the lead car and the tail car. The lead car directly faces the wind and experiences the greatest aerodynamic pressure; the tail car is located in a complex wake region and experiences significant pulsating pressure and torque; the middle car is affected by the airflow brought by the lead car after multiple disturbances. Therefore, the force conditions of the lead car, middle car, and tail car are completely different.

[0013] Because they experience completely different forces, the motion postures (such as roll, head-up, and head-down) of the lead, middle, and tail cars under wind load will also differ. The lead car may initiate motion first and transmit it to subsequent cars through the coupler and windshield. To define their physical properties (mass, inertia, etc.), configure their suspension systems with the bogies, and independently monitor the aerodynamic and motion posture parameters of each car in the simulation, the lead, middle, and tail cars are separated and numbered. This allows for accurate analysis of the transmission and evolution of wind shear effects along the train's length.

[0014] The bogie is a component connecting the car body and the track. Its motion is constrained by the track, while it interacts with the car body through a suspension system (such as a secondary suspension). The bogie has its own independent motion relative to the car body. The windshield is a flexible component connecting two car bodies. Its main function is to undergo elastic deformation to accommodate the relative motion between the car bodies. Separating the bogie and windshield is to reconstruct a digital train geometry model that is both physically accurate and computationally efficient during simulation. This model is a dynamic system composed of multiple components with mass, inertia, and elastic connections. This allows for accurate simulation of the influence of airflow on train motion under wind shear and the two-way fluid-structure interaction effect of train motion altering airflow states.

[0015] Furthermore, after the components are divided and numbered, each component is further simplified, including: The vehicle body surface is smoothed and non-aerodynamically critical features are removed; The structure of the windshield is simplified, retaining only its basic groove shape, and it is set as a flexible deformation area; The bogie is truncated at the top to create a flat surface.

[0016] In this embodiment, the vehicle body surface is smoothed to remove non-critical geometric features with minimal impact on macroscopic aerodynamic characteristics under high-speed crosswind conditions, such as pantograph mounts, door and window recesses, and small vents. This avoids generating a large number of low-quality, tiny meshes, reduces the overall mesh count, improves surface mesh quality, and lowers computational complexity. To prevent non-physical penetration or collision between the vehicle's geometric boundaries and the underlying bogie components during large-angle attitude changes (such as roll) in the simulation, which could lead to computational interruption, the bogie is truncated, retaining only the main structure and removing the upper portion where it connects to the vehicle body. This truncation ensures mesh stability during large-angle vehicle body movements and avoids computational interruptions. This simplified processing helps concentrate computational resources on capturing the mainstream field changes caused by the macroscopic movements of moving components such as the vehicle body and bogie frame, as well as the overall deformation of the windshield, rather than being distracted by the flow of minor details.

[0017] Furthermore, 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 direction of the incoming flow is less than 15%.

[0018] 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 direction of the incoming flow (i.e., the blockage ratio), the interference of the wall on the flow field is minimized.

[0019] Furthermore, the wind field boundary conditions are set as follows: the front of the lead vehicle and the windward side are velocity inlets, the rear of the tail vehicle and the leeward side are pressure outlets, the top is a symmetrical boundary, and the bottom is a sliding wall. A wind speed curve generated from measured wind field parameters is loaded at the velocity inlet.

[0020] In this embodiment, the front of the lead car and the windward side are designated as velocity inlets, which accurately defines the magnitude and direction of wind shear. The rear of the tail car and the leeward side are designated as pressure outlets, which realistically simulates the complex vortex shearing and wake development process behind the train and on the leeward side. The top is designated as a symmetrical boundary and set at an appropriate height above the car body to ensure the complete development of the flow field. The bottom is designated as a sliding wall, which is more in line with reality and can better balance computational accuracy and grid resource consumption. The wind speed curve generated by the measured wind field parameters is loaded onto the velocity inlets, realizing a realistic simulation of wind shear along the railway line.

[0021] Furthermore, a preset number of mesh cells are maintained between the boundary of the overlapping region and the boundary of the background region, and a close contact and hole cutting function is enabled in the setting of the overlapping mesh interface to automatically and stably handle the mesh relationship in the narrow area between the bottom of the vehicle body and the track surface.

[0022] Furthermore, the elastic connection element includes an elastic damping system for simulating the suspension action between the vehicle body continuous and the bogie continuous; the stiffness and damping coefficient of the elastic damping system are set according to the vehicle's secondary suspension parameters. The vertical spring used to simulate the secondary suspension is provided with an initial compression amount. The initial support force provided by the initial compression amount is balanced with the gravity of the corresponding vehicle body, ensuring that the model is in the correct static equilibrium initial state under the gravity field. A roll-resistance bar is simulated by defining a torque acting on the vehicle body continuous, the torque being proportional to the roll angle of the vehicle body continuous. An anti-snagging damper is simulated by defining multiple pairs of couples acting on the vehicle body continuum, wherein the couples are proportional to the yaw angle of the vehicle body continuum.

[0023] Furthermore, the mesh division adopts a cut volume mesh, and the bogie area and the bottom area of ​​the car body are locally densified; Based on the surface mesh of the vehicle body, the mesh is gradually densified outwards layer by layer; Nested encryption regions with shapes similar to the computational domain of each component are set up within each component area, with the size of the encryption regions gradually increasing from the inside out. The background domain and the overlapping domain maintain the same grid size at the interface to ensure the accuracy and computational stability of the flow field interpolation between the background domain and the overlapping domain.

[0024] Based on the same concept, the present invention also provides an electronic device, including 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 numerical simulation method for the aerodynamic performance of a high-speed train under coupled attitude motion under wind shear as described above.

[0025] Based on the same concept, the present invention also provides a computer-readable storage medium having a computer program or instructions stored thereon, which, when executed by a processor, implements the numerical simulation method for the aerodynamic performance of a high-speed train under coupled attitude motion under wind shear as described above.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention directly embeds the multibody dynamics topology of the vehicle into the CFD solver kernel, achieving synchronous and bidirectional solving of the flow field and the motion of moving parts such as the vehicle body within a unified framework. This invention can accurately capture the complete physical feedback process of "aerodynamic loads causing motion of moving parts such as the vehicle body --> the motion of moving parts such as the vehicle body changing the flow field --> the new flow field reacting on the aerodynamic loads". It fundamentally overcomes the shortcomings of ignoring coupling effects or having data delays in traditional unidirectional coupling or co-simulation, making the evaluation results of vehicle aerodynamic safety (such as anti-overturning and anti-derailment performance) under extreme conditions such as wind shear more realistic and reliable.

[0027] This invention adopts a "static background domain + dynamic overlapping domain" architecture and uses overlapping mesh technology to handle large displacement motion. It completely avoids the computational interruption problem caused by mesh distortion due to large-scale rotation of the vehicle body (such as side roll) in traditional dynamic meshes. It ensures that the mesh quality remains unchanged during the simulation of complex attitude changes, thus enabling the stable and robust completion of the entire transient simulation process and solving the technical problem that has long plagued numerical simulation in this field.

[0028] This invention integrates aerodynamic and dynamic analysis into a single software platform, eliminating the data exchange, interface configuration, and waiting time required for multi-software co-simulation. This integrated process not only simplifies operation and lowers the barrier to entry, but also improves computational efficiency by orders of magnitude by avoiding inter-process communication overhead. This makes long-term, multi-condition transient analysis feasible in engineering practice, greatly promoting design iteration and parameter optimization. Attached Figure Description

[0029] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a flowchart of the numerical simulation method for the aerodynamic performance of a high-speed train under coupled attitude motion under wind shear in an embodiment of the present invention; Figure 2 This is a velocity field cloud map of the vehicle body deflecting 2° towards the windward side in an embodiment of the present invention; Figure 3 This is a velocity field cloud map of the vehicle body deflected 2° towards the leeward side in an embodiment of the present invention; Figure 4 This is a velocity field cloud map of the vehicle body without deflection in an embodiment of the present invention; Figure 5 This is the vehicle attitude angle output curve in an embodiment of the present invention; Figure 6 This is the lateral acceleration output curve of the vehicle body in an embodiment of the present invention; Figure 7 This is the aerodynamic output curve in an embodiment of the present invention; Figure 8 This is the aerodynamic torque output curve in an embodiment of the present invention. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0033] Example 1 Figure 1 A flowchart illustrating the numerical simulation method for the aerodynamic performance of a high-speed train under coupled attitude motion under wind shear provided by this invention is shown. Figure 1 As shown, this numerical simulation method includes the following steps: Step 1: Construct a simplified geometric model of a multi-car train, and divide the head car, middle car, tail car, bogie, and windshield in the simplified geometric model into independent components and number them.

[0034] Based on a certain train formation model, a simplified geometric model is constructed. The head car, middle car, tail car, bogie, and windshield in the simplified geometric model are separated into independent components, so as to facilitate the subsequent independent definition of attributes, setting of motion, and application of monitoring.

[0035] Step 2: Simplify each component.

[0036] To concentrate computational resources on capturing the mainstream field changes caused by the macroscopic motion of moving parts such as the car body and the overall deformation of the windshield, without being disturbed by the flow of minor details, the components were simplified. Specifically, the car body surface was smoothed, and non-critical geometric features with minimal impact on macroscopic aerodynamic characteristics under high-speed crosswind conditions, such as pantograph mounts, door and window recesses, and small vents, were removed, avoiding the generation of a large number of low-quality, extremely small meshes and improving mesh quality. The windshield structure was simplified, retaining only the recessed shape of its capsule-shaped windshield, ignoring complex details such as internal seals, and setting it as a separate flexible deformation region. To prevent interference between the rotating car body and the fixed bogie during train attitude changes, the upper complex structure at the connection between the bogie and the car body was removed, creating a flat surface on the top of the bogie and preventing geometric interference between the car body and the bogie during movement.

[0037] In this embodiment, a global reference coordinate system is established with the point where the nose of the lead car is flush with the track plane (bottom surface of the wheelset) as the origin, providing a unified benchmark for subsequent mesh generation, motion definition and result analysis.

[0038] Step 3: Construct a multi-domain computing environment that includes a background domain and an overlapping domain, and build an overlapping network interface between the overlapping domain and the background domain to form a channel for dynamic exchange of flow field data.

[0039] After model construction and processing, a computational environment for numerical simulation needs to be created. This invention employs a multi-domain computational environment combining background and overlapping domains to efficiently and stably simulate the interaction between vehicles and the flow field under wind shear.

[0040] The background domain is used to simulate the macroscopic atmospheric environment and wind shear scenarios in which the train operates. Its construction steps are as follows: A regular cuboid computational domain is created outside the simplified geometric model (i.e., the train). This computational domain completely encloses the entire train and provides sufficient space in front of and behind the train (flow direction), to the left and right (lateral), and above (vertical) to ensure the stable development of the incoming and wake flows. The size of the background domain must meet the requirement that the blockage ratio (i.e., the ratio of the train's maximum cross-sectional area to the cross-sectional area of ​​the background domain in the direction of incoming flow) is less than 15% to minimize wall effects.

[0041] To accurately simulate wind shear scenarios, the wind field boundary conditions are set as follows: The Velocity Inlet is set at the watershed boundary in front of the lead car (simulating the incoming flow of the advancing train) and the watershed boundary on the windward side of the train (simulating the far-field incoming flow; measured wind field parameters can be directly embedded to reproduce the real wind field). The inlet location should be far enough away from the train to ensure that the incoming flow can enter the computational environment uniformly. Wind field parameters such as average wind speed, wind direction, turbulence intensity, gust factor, and fluctuating wind speed power spectrum are obtained through field measurements. Wind speed curves along the railway line are generated based on these parameters. These wind speed curves are then loaded into the Velocity Inlet as an editable data table, achieving a realistic simulation of wind shear.

[0042] Pressure Outlet: Located at the watershed boundary behind the last car and the far boundary on the leeward side of the train, to ensure that the wake can fully evolve and tend to stabilize. In this embodiment, the reference value of the outlet pressure is set to the ambient pressure condition.

[0043] Symmetry Plane: Set at the top of the computational environment and at an appropriate height above the vehicle body to ensure the complete development of the process.

[0044] Slip Wall: Located at the bottom of the computational environment, corresponding to the ground and track. The slip wall simulates the air-carrying effect of the ground, while also taking into account the actual height of the track relative to the ground.

[0045] To simulate the forward motion of a train, the fluid region of the entire background domain is set as a motion reference frame with the same speed and opposite direction as the train.

[0046] The overlapping region is a local area that tightly encloses the moving parts of the train. It moves along with the train and is key to achieving attitude coupling. The process of constructing the overlapping region is as follows: Create a regular cuboid region that completely encloses all moving parts of the train (such as the car body, bogie frame, etc.), thus forming an overlapping domain.

[0047] In this embodiment, a preset number of grid cells need to be maintained between the boundary of the overlapping domain and the boundary of the background domain. This gap serves as a buffer for data interpolation and is the basis for ensuring the accurate transmission of flow field information between the overlapping domain and the background domain.

[0048] To achieve accurate flow field simulation under large-scale vehicle body attitude movements, it is necessary to correctly define the overlapping region and its interface. Since the core focus of the simulation is the attitude change of the vehicle body relative to the bogie (such as roll, yaw, pitch, lateral movement, vertical movement, etc.), and the motion of the vehicle body relative to the bogie is much greater than the motion of the bogie relative to the track plane, this invention sets the motion reference of the overlapping region on the track plane to simplify the motion reference and more effectively capture the main motion attitudes. In a specific embodiment of this invention, the region is divided using Boolean subtraction operations: Subtracting the vehicle surface from the overlapping domain geometry generates the computational domain for the flow field around the vehicle during its motion. Subtracting the track model surface from the background domain geometry generates the background flow field region outside the track. These two components (computational domain and background flow field region) and their surfaces, generated through subtraction, are used to construct a new CFD computational domain using the software's region allocation function. The boundary of the overlapping domain is set to an overlapping mesh, and an overset interface is created between the overlapping domain and the background domain to serve as the boundary for flow field data interpolation and exchange between the two domains.

[0049] Considering the small distance between the bottom of the train and the track, the following advanced options are enabled in the overlapping mesh interface settings to ensure interpolation stability and calculation accuracy: Close contact: Optimizes mesh connection processing in narrow gaps.

[0050] Prismatic layer shrinkage: Automatically adjusts the boundary layer mesh when the gap is extremely small to prevent mesh failure.

[0051] Replace hole cutting: Automatically mark background domain mesh elements that are completely obscured by solids as "hole" elements that do not participate in the calculation.

[0052] This series of settings can effectively avoid numerical instability caused by mesh distortion during vehicle movement, and is a key technical measure to ensure the smooth operation of coupled simulation.

[0053] Step 4: Within the CFD framework, each moving component (such as the vehicle body, bogie frame, etc.) is characterized by defining a three-dimensional continuum with physical properties, and its multibody motion degrees of freedom are activated; by setting elastic connection elements between the continuums of each moving component, the multibody dynamics topology of the vehicle is directly embedded into the CFD solver.

[0054] Enable fluid-structure interaction (FSI) in the CFD software. Create a new motion type (e.g., six-degree-of-freedom motion or motion following a specified law), and specify the motion type of the overlapping domain computational region as this new motion type. This allows the overlapping domain and the train motion components within its envelope to be defined as a movable whole, thus establishing the basis for coupling the background flow field with the motion of the overlapping domain.

[0055] In the fluid-structure interaction (FSI) function's sub-options, create a three-dimensional continuum for each moving component in the group. For example, create a three-dimensional continuum for each car body (lead car, middle car, and tail car), and name them according to their numbers (e.g., body_1, body_2, ...). Set the body surface of each moving component continuum to the corresponding outer surface of the overlapping domain. Accurately input its physical properties, such as mass and moment of inertia, in the properties of each moving component continuum. These physical properties are derived from the vehicle design data. Set the body motion option of each moving component continuum to multibody motion, and activate the key degrees of freedom according to the requirements of crosswind stability analysis. In this embodiment, for the car body, at least roll and lateral translation degrees of freedom are enabled.

[0056] The mechanical interactions between car body continuouss and between the car body continuous and the bogie continuous are simulated by using a spring-damped system with volumetric coupling. For example, multiple spring-dampers are established between the car body continuous and the corresponding bogie continuous to simulate the secondary suspension. The number, spatial distribution, stiffness, and damping coefficient of the spring-dampers are consistent with the design parameters of the secondary suspension of a real vehicle. In this embodiment, the vertical springs simulating the secondary suspension need to be initially compressed so that the initial support force they provide exactly balances the weight of the car body they support, ensuring that the model is in the correct initial static equilibrium state under the gravitational field.

[0057] The function of an anti-roll torsion bar is simulated by defining a torque acting on the car body continuum, the magnitude of which is proportional to the roll angle of the car body. An anti-snaking damper is simulated by defining four pairs of couples acting on the car body continuum, the couples being proportional to the yaw angle of the car body continuum. At the coupler connections of adjacent car bodies, coupling connections (such as articulations) are established to constrain the relative motion between the car bodies, and the windshield is set as a flexible deformable region, thereby simulating the overall dynamic behavior of long-formation trains.

[0058] The "embedded fluid-structure interaction" numerical framework constructed in this invention has universality. By adjusting vehicle dynamic parameters (mass, moment of inertia, suspension stiffness, etc.) and flow field boundary conditions, this method can be widely applied to the study of aeroelasticity problems of high-speed trains with different formations and models, and even other means of transportation, demonstrating good versatility and scalability.

[0059] Step 5: Mesh the multi-domain computing environment and select a physical model for solution calculation; during the solution process, synchronously monitor and output the aerodynamic parameters acting on the train and the motion attitude parameters of the moving parts in real time.

[0060] To control computational resource consumption while ensuring computational accuracy, a structured meshing strategy is required for the multi-domain computing environment (computation domain). In this embodiment, the background domain and overlapping domain are discretized using a cut-volume mesh.

[0061] During mesh generation, differentiated mesh sizes are used for different components to balance accuracy and efficiency: due to the complex geometry and strong vortex flow in the bogie region, a finer surface mesh is applied; the relatively smooth car body surface uses a relatively coarser surface mesh, and the mesh is gradually refined outward from the car body surface mesh as a reference. Nested refinement regions with shapes similar to the computational domain of each component are set within each component region, with the size of the refinement regions gradually increasing from the inside out. Volume control is applied to the automatic meshing of the background domain to achieve hierarchical mesh refinement. The main region of the background domain uses a relatively sparse mesh to reduce the overall mesh count while maintaining computational accuracy.

[0062] The flow field changes are most complex at the bottom of the car body, especially around the bogies. Therefore, local densification needs to be applied to this area, ensuring sufficient coverage margin along the train's length to capture key flow structures. To accurately capture the development of vortex structures near the train surface, multiple boundary layer meshes are applied to all car body walls, allowing for thorough analysis of boundary layer flow characteristics.

[0063] During mesh generation, the mesh aspect ratio is controlled to be less than 2:1 to maintain high mesh quality. Simultaneously, the mesh size at the interface between the overlapping and background domains should be kept as consistent as possible to achieve stable coupling between the two domains and effective transmission of flow field information.

[0064] To accurately simulate the complex flow around a vehicle under wind shear and its coupling with the vehicle's motion, the physical model and numerical method used for the solution need to be configured: The Navier-Stokes equations based on the implicit unsteady SST k-ω turbulence model were chosen to simulate the flow field around the train, preventing flow separation caused by model stress loss and mesh issues. This approach combines the advantages of the standard k-ω model's accuracy in near-wall regions with its robustness in far-field free flow, enabling more accurate prediction of flow separation points and the extent of separation zones, effectively preventing distortion in the simulation of separated flow due to inaccurate model stress predictions.

[0065] This embodiment sets the fluid physical properties to constant density, i.e., incompressible flow, to simplify the governing equations and significantly improve computational efficiency. A separate flow solver is selected for optimization of incompressible flows, effectively handling a wide range of flow separation phenomena.

[0066] Activate the turbulence option in the model list to enable the SST k-ω turbulence model mentioned above, while also enabling the gravity model and setting the gravitational acceleration.

[0067] After completing all preprocessing settings, final configuration of solver parameters, data monitoring, and computation tasks is required to initiate transient coupled computation. In the solver control panel, define the following key parameters to control the computation's progression: Time step: Determined based on the characteristic frequency of wind shear and the frequency of train motion response, it needs to be small enough to capture key transient physical processes.

[0068] Total duration: Set a sufficiently long simulation time to ensure that the dynamic response of the train under wind shear reaches stability or completes a full evolution cycle.

[0069] Maximum number of iterations per time step: Sets the maximum number of iterations for the solver within each time step to ensure that the equation residuals converge sufficiently within that time step.

[0070] Time discretization scheme: A second-order implicit scheme is used for time discretization to improve the numerical accuracy of time progression.

[0071] To implement tracking of computational status and capture key results, appropriate monitors need to be set up: Force and Torque Monitor: Create a monitor to record in real time the resistance, lateral force, lift, overturning moment, pitching moment, and yaw moment of the entire vehicle and its components (such as the car body and bogies).

[0072] Motion attitude parameter monitor: Create a monitor to record in real time the roll angle, pitch angle, yaw angle, lateral displacement, vertical displacement, velocity, angular velocity, acceleration, angular acceleration, etc. of each moving part (such as the vehicle body).

[0073] Field variable monitoring: Monitor flow field parameters such as pressure and velocity at key locations throughout the entire computational domain.

[0074] Scene Recording: Enable the Scene recording function to save the flow field cloud map, vector map, and transient data of vehicle motion attitude for subsequent animation generation and detailed post-processing analysis.

[0075] After completing all the above settings, perform the following operations to start the calculation: Based on the established meshing strategy, volume meshes for the background domain and overlapping domain are generated; appropriate initial conditions (such as uniform inflow) are used to initialize the flow field of the computational domain; the complete simulation model is submitted to the solver; the solver will automatically perform the calculation, simultaneously solving the flow field control equations and multibody motion equations in each time step, thus realizing fluid-structure interaction simulation.

[0076] Step 6: Result Analysis and Iterative Optimization After the simulation calculation is completed, the output data is extracted and analyzed using the software's post-processing function to evaluate the comprehensive performance of high-speed trains under wind shear conditions.

[0077] The attitude angles (roll angle, pitch angle, and yaw angle) and displacements (lateral displacement and vertical displacement), acceleration, and velocity of each car body are extracted as time-varying curves. By analyzing these curves, the dynamic stability of the train under wind shear excitation is evaluated, key motion modes (such as car body roll) and their amplitude and frequency characteristics are identified, providing direct evidence for judging train safety risks (such as overturning and derailment tendencies).

[0078] Visualize and analyze flow field data at specific times or time averages: Pressure distribution cloud map: used to identify high-pressure impact zones and low-pressure separation zones on the vehicle body surface, and to analyze the distribution pattern of aerodynamic loads.

[0079] Velocity vector and streamline diagram: used to reveal the flow structure around the train, the generation, evolution and shedding of vortices, especially the unsteady characteristics of the wake region.

[0080] By combining flow field structure, we can gain a deeper understanding of the physical mechanisms that generate specific aerodynamic loads.

[0081] Time series data of aerodynamic forces and moments (drag, lateral force, lift, overturning moment, pitching moment, and yaw moment) of the whole vehicle and key components are extracted, and their mean, pulsation amplitude and dominant frequency are analyzed to quantitatively assess the transient and statistical impact of wind shear on the aerodynamic performance of the train.

[0082] Based on the analysis results of the above dynamic response, flow field structure, and aerodynamic loads, a complete correlation between "wind field excitation - aerodynamic load - vehicle motion" is established. This invention can accurately simulate the aerodynamic characteristics and multibody motion attitude of high-speed trains under wind shear, and its quantitative analysis conclusions can provide effective numerical basis and support for the wind resistance stability design, suspension parameter optimization, and operational safety assessment of trains.

[0083] Figures 2 to 8 The numerical simulation results of the aerodynamic performance of a high-speed train under coupled attitude motion under wind shear are shown, in which... Figures 2 to 4 This is a velocity field contour map of the vehicle body at different deflection angles. Figure 5 and Figure 6 Output curves for vehicle motion attitude parameters. Figure 7 and Figure 8 This is the aerodynamic load output curve. (From...) Figures 2 to 8 It can be seen that this invention can directly reveal the bidirectional dynamic coupling interaction between the vehicle's attitude motion and the surrounding flow field, including the pressure field and the velocity field (such as...). Figures 2 to 4 The changes in ) and the motion attitude parameters of the vehicle body under this coupling effect (such as Figure 5 and Figure 6 ) and vehicle aerodynamic load response (such as Figure 7 and Figure 8 ).

[0084] In contrast, existing methods typically only analyze the unidirectional influence of aerodynamics on vehicle attitude motion, failing to capture the reverse interference effect of vehicle motion on the flow field. Therefore, this invention achieves true two-way fluid-structure interaction analysis, while existing methods only involve the unidirectional interaction between aerodynamics and train dynamics.

[0085] This invention can simultaneously output high-precision flow field details (such as pressure field and velocity field), vehicle motion attitude parameters (such as attitude angle, velocity, acceleration, etc.), and aerodynamic load responses (such as aerodynamic force and aerodynamic torque). This data synchronization enables researchers to clearly establish the causal relationship between "flow field excitation - aerodynamic load - motion response," not only predicting phenomena but also gaining a deeper understanding of their underlying physical mechanisms. This provides direct and powerful theoretical basis and numerical guidance for the wind-resistant design of trains (such as shape optimization and suspension parameter matching).

[0086] Example 2 This invention also provides an electronic device, which includes a memory, a processor, and a computer program or instructions stored in the memory. The processor executes the computer program or instructions to implement the numerical simulation method for high-speed train aerodynamic performance under coupled attitude motion under wind shear in Embodiment 1 of this invention.

[0087] Although not shown, the electronic device includes a processor that can perform various appropriate operations and processes based on programs and / or data stored in read-only memory (ROM) or loaded from a storage portion into random access memory (RAM). The processor can be a multi-core processor or may contain multiple processors. In some embodiments, the processor may include a general-purpose main processor and one or more specialized coprocessors, such as a central processing unit, graphics processing unit (GPU), neural network processor (NPU), digital signal processor (DSP), etc. Various programs and data required for device operation are also stored in RAM. The processor, ROM, and RAM are interconnected via a bus. Input / output (I / O) interfaces are also connected to the bus.

[0088] The processor and memory described above are used together to execute programs / instructions stored in the memory. When the program / instructions are executed by the computer, they can implement the methods, steps, or functions described in the above embodiments.

[0089] Although not shown, embodiments of the present invention also provide a computer-readable storage medium having a computer program or instructions stored thereon, which, when executed by a processor, implements the numerical simulation method for high-speed train aerodynamic performance under coupled attitude motion under wind shear as described in Embodiment 1 of the present invention.

[0090] Readable storage media include both permanent and non-permanent, removable and non-removable media that can store information by any method or technology. 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, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0091] The above description only discloses specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or modifications that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A numerical simulation method for the aerodynamic performance of a high-speed train under coupled attitude motion under wind shear, used to achieve bidirectional coupled solution of flow field and train motion within a unified CFD framework, characterized in that... The method includes: A multi-domain computing environment is constructed, comprising a background domain and an overlapping domain. The background domain is configured with wind field boundary conditions simulating wind shear. The overlapping domain encompasses all moving parts of the train and is coupled to the background domain through the overlapping mesh interface, forming a channel for dynamic exchange of flow field data. Within the CFD framework, each moving part is characterized by defining a three-dimensional continuum with physical properties, and its multibody motion degrees of freedom are activated; by setting elastic connecting elements between the continuums of each moving part, the multibody dynamics topology of the vehicle is directly embedded into the CFD solver. The multi-domain computing environment is meshed and a physical model is selected for solution calculation. During the solution process, the aerodynamic parameters acting on the train and the motion attitude parameters of each moving component are monitored and output in real time.

2. The numerical simulation method for high-speed train aerodynamic performance under coupled attitude motion under wind shear as described in claim 1, characterized in that, Before constructing a multi-domain computing environment that includes a background domain and an overlapping domain, the method further includes constructing a simplified geometric model of a multi-train train and dividing the head car, middle car, tail car, bogie, and windshield in the simplified geometric model into independent components and numbering them.

3. The numerical simulation method for high-speed train aerodynamic performance under coupled attitude motion under wind shear as described in claim 2, characterized in that, After the components are divided and numbered, each component is further simplified, including: The vehicle body surface is smoothed and non-aerodynamically critical features are removed; The structure of the windshield is simplified, retaining only its basic groove shape, and it is set as a flexible deformation area; The bogie is truncated at the top to create a flat surface.

4. The numerical simulation method for high-speed train aerodynamic performance under coupled attitude motion under wind shear as described in claim 1, characterized in that, The background domain is a regular rectangular 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 direction of the incoming flow is less than 15%.

5. The numerical simulation method for high-speed train aerodynamic performance under coupled attitude motion under wind shear as described in claim 1, characterized in that, The wind field boundary conditions are set as follows: the front of the lead vehicle and the windward side are the velocity inlet, the rear of the tail vehicle and the leeward side are the pressure outlet, the top is a symmetrical boundary, and the bottom is a sliding wall. A wind speed curve generated from measured wind field parameters is loaded at the velocity inlet.

6. The numerical simulation method for high-speed train aerodynamic performance under coupled attitude motion under wind shear as described in claim 1, characterized in that, The boundary of the overlapping region and the boundary of the background region maintain a gap of a preset number of grid cells, and the close contact and replacement hole cutting function are enabled in the setting of the overlapping grid interface.

7. The numerical simulation method for high-speed train aerodynamic performance under coupled attitude motion under wind shear as described in claim 1, characterized in that, The elastic connection element includes an elastic damping system for simulating the suspension action between the vehicle body continuous and the bogie continuous; the stiffness and damping coefficient of the elastic damping system are set according to the vehicle's secondary suspension parameters. The vertical spring used to simulate a two-stage suspension is provided with an initial compression, the initial support force provided by the initial compression being balanced with the weight of the corresponding vehicle body; A roll-resistance bar is simulated by defining a torque acting on the vehicle body continuous, the torque being proportional to the roll angle of the vehicle body continuous. An anti-snagging damper is simulated by defining multiple pairs of couples acting on the vehicle body continuum, wherein the couples are proportional to the yaw angle of the vehicle body continuum.

8. The numerical simulation method for the aerodynamic performance of a high-speed train under coupled attitude motion under wind shear according to any one of claims 1 to 7, characterized in that, The grid division adopts a cut-body grid, and the bogie area and the bottom area of ​​the car body are locally densified; Based on the surface mesh of the vehicle body, the mesh is gradually densified outwards layer by layer; Nested encryption regions with shapes similar to the computational domain of each component are set up within each component area, with the size of the encryption regions gradually increasing from the inside out. The background domain and the overlapping domain have the same grid size at the interface.

9. An electronic device comprising a memory, a processor, and a computer program or instructions stored in the memory, characterized in that, The processor executes the computer program or instructions to implement the numerical simulation method for the aerodynamic performance of a high-speed train under coupled attitude motion as described in any one of claims 1 to 8.

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

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