## 2 Analysis of High-Speed Maglev Noise Source Distribution  
### Numerical Simulation Model of the Flow Field  
The three-dimensional and triple-unit configuration of the Shanghai TR08 Maglev system exhibits longitudinal dimensions of 27 m for both terminal vehicular modules and 24.5 m for the intermediate coach section, with 0.25 m windshield clearance between adjacent units, culminating in an aggregate length of 79 m for the complete train formation, as shown in Figure 1a. Geometric abstraction was used to solve the inherent surface irregularity problem in the geometry, and smaller auxiliary features were excluded from the computational domain. Vertical clearance and lateral span measurements were 4.7 and 3.7 m, respectively, while the transverse deck dimension of the guideway was 2.8 m, as shown in Figure 1b. The electromagnetic suspension maintained a 10 mm operational clearance above the elevated bridge structure, with a 10 m vertical elevation [16]. This streamlined topology modeled using SolidWorks is shown in Figure 1.  
The fluid dynamics simulation domain encompassing the full-scale Maglev vehicle configuration on the guideway system is shown in Figure 2. The spatial arrangement comprised a 40 m inflow boundary offset from the leading vehicle nose and an 80 m outflow boundary clearance from the trailing vehicle nose, yielding a 199 m longitudinal computational span. Vertically, the domain extended 10 m below and 13.5 m above the guideway reference plane, establishing a total vertical dimension of 23.5 m. The lateral confinement of the domain measured 22.2 m in the transverse direction. The aerodynamic simulation framework incorporated compressible flow considerations for Maglev velocities of 235, 300, and 430 km/h. The _abcd_ boundary was configured as a pressure far-field with 1 atm pressure and a zero yaw angle. Symmetric constraints were applied to the _aefb_, _bfgc_, and _cghd_ planes. Ground effect modeling utilized slip walls on _aehd_ and guideway surfaces with velocities matching the inflows. The train surface was defined as a no-slip stationary wall. The _efght_ boundary implemented a pressure outlet at ambient conditions. Two mesh refinement zones (Blocks 1 and 2) were strategically positioned around the train geometry to ensure computational accuracy, as shown in Figure 2.  
The computational framework employed a hybrid meshing strategy with refinement zones to achieve the required solution accuracy. The mesh partitioned using Fluent Meshing is shown in Figure 3. Surface discretization followed curvature-adaptive principles where grid element dimensions scaled inversely with surface curvature gradients. Critical flow resolution parameters were defined through simultaneous resolution of boundary layer dynamics and turbulence modeling requirements. Specific element sizing included 10 mm for aerodynamically sensitive zones (streamlined nose/tail sections), 30 mm for geometrically stable regions (door interfaces, carriage junctions, and underbody components), and 100 mm for guideway surfaces. The final surface grid configuration contained approximately 22 million elements. Figure 1: Shanghai Maglev train TR08 geometric model: (**a**) side view, (**b**) front view. Figure 2: Computational domain and mesh refinement zones. The near-body flow region was discretized using unstructured prismatic elements to accommodate complex geometries. A wall-resolved large eddy simulation (LES) approach was implemented with the first grid node placement at 0.01 mm normal to the solid surfaces. The boundary layer transition was achieved through 25 progressively expanding prismatic layers (growth factor 1.05), ensuring a smooth velocity gradient resolution between the viscous sublayer and main flow regions. The meshing strategy employed dual refinement blocks to enhance the flow-resolution accuracy. Block 1 enveloped the Maglev train surfaces with a maximum element size of 100 mm, while Block 2 had a 300 mm mesh control to mitigate wake interference.