The computational fluid dynamics (CFD) simulation of flow over railway tracks has become increasingly critical for addressing one of the most challenging issues in railway transportation – sand deposition. Aeolian particle transport is a big problem for train operations in dry areas and deserts; it has a direct effect on the safety and efficiency of transportation. Engineers can study and guess how wind flow patterns, sand particle movement, and railway structures will affect each other by using ANSYS Fluent for CFD modeling. This advanced simulation method is necessary to test and create good ways to stop sand from building up, which can slow down trains, cause them to derail, and raise the cost of maintenance. Consequently, the current CFD study is conducted, featuring from a reference paper entitled “A new approach in reducing sand deposition on railway tracks to improve transportation”.

• Reference [1]: Mehdipour, R., and Z. Baniamerian. “A new approach in reducing sand deposition on railway tracks to improve transportation.” Aeolian Research41 (2019): 100537.

Figure 1: a) schematic of railway track on an embankment b) Sand deposition on the railway [1]

Simulation process

The computational fluid dynamics (CFD) simulation was run on ANSYS Fluent. ANSYS Design Modeler was used to make the initial design, and ANSYS Meshing was used to mesh the geometry. The 2D model area was 120 meters wide and 60 meters high to make sure that all the flow conditions were fully developed. Tetrahedral non-uniform meshes were used, with smaller pieces concentrating near the railroad track and getting bigger as you move away. A 10 m/s velocity inlet was set at the right edge based on local aerology data for storm conditions. There was an outflow condition at the left edge, and the upper border was symmetric.

Figure 2: Developed unstructured meshing for the 2D model

Post-processing

The velocity contours show clear flow patterns around the shape of the train track. When 10 m/s of entering flow hits the track cavities, it slows down a lot, creating two large recirculation zones with speeds close to 0 and 2 m/s. There are counter-rotating vortices in these low-speed areas, which can be seen most clearly in the streamline image. The flow speeds up over the top of the track structure, hitting speeds of about 11–12 m/s because the flow area is smaller. These flow features have a direct effect on how potential sand particles behave. The low speeds aren’t fast enough to keep the particles in suspension, so the recirculation zones in the track holes make it easy for particles to settle down. The faster flow over the track surfaces would probably keep particles from building up there, but they would be moved to the lee side of the track structure. Based on this flow pattern, it looks like sand would build up most in the hollow areas, especially in the swirl further downstream where flow speeds are lowest. These results suggest that in real-world railway applications, safety steps or changes to the design should focus on stopping these recirculation zones or stopping particles from getting into these important areas.

Figure 3: Streamlines of Flow Over Railway Track CFD Simulation