## Team for Advanced Flow Simulation and Modeling |

For more information: |
## Flow Around High-Speed Trains Passing in a TunnelAerodynamics plays a crucial role in the design and development of high-speed trains from the point of view of cost effectiveness, safety, comfort, and minimal impact on the environment, amongst many other factors. Trains passing each other, especially in tunnels, create pressure transients which may threaten the structural integrity of the trains and may also cause some discomfort to the passengers. The mesh we used is rather coarse for a 3D problem with intricate geometries and therefore we attach to the results only a qualitative significance. The mesh consists of 51,584 hexahedral elements and 58,607 nodes, and results in approximately 550,000 coupled equations. To accommodate the motion of the trains we have developed a special algebraic mesh moving and remeshing scheme where elements are transplanted from regions in front of the trains to regions behind the trains when they become too distorted. The total number of nodes and elements remains fixed during the simulation. At the start of the simulation the trains are at rest near the tunnel entrances and accelerate to 100 m/s during the first second, which is the speed at which they will pass each other. This leads to a relative Mach number of approximately 0.6 when the trains pass. We observe that as the trains gain speed, high-pressure regions develop at the front of the trains, and low-pressure regions develop at the rear. The images below show the pressure distribution on the surface of the trains and on a cutting plane parallel to the tunnel floor. The mesh is superimposed on top of the cutting plane. The mesh generator, flow solver, and flow visualization software (based on Visual3 library and Wavefront) were developed by the T*AFSM.
## References: 1. T.E. Tezduyar and T.J.R. Hughes, "Finite Element Formulations for
Convection Dominated Flows with Particular Emphasis on the Compressible
Euler Equations", AIAA Paper 83-0125, 2. T.J.R. Hughes and T.E. Tezduyar, "Finite Element Methods for
First-order Hyperbolic Systems with Particular Emphasis on the
Compressible Euler Equations", 3. G.J. Le Beau and T.E. Tezduyar, "Finite Element Computation of
Compressible Flows with the SUPG Formulation", 4. G.J. Le Beau and T.E. Tezduyar, "Finite Element Solution of Flow
Problems with Mixed-Time Integration", 5. T.E. Tezduyar, "Stabilized Finite Element Formulations for
Incompressible Flow Computations", 6. T.E. Tezduyar, M. Behr and J. Liou, "A New Strategy for Finite
Element Computations Involving Moving Boundaries and Interfaces--The
DSD/ST Procedure: I. The Concept and the Preliminary Numerical Tests",
7. T.E. Tezduyar, M. Behr, S. Mittal and J. Liou, "A New Strategy for
Finite Element Computations Involving Moving Boundaries and
Interfaces--The DSD/ST Procedure: II. Computation of Free-surface Flows,
Two-liquid Flows, and Flows with Drifting Cylinders", 8. T.E. Tezduyar, M. Behr, S. Mittal and A.A. Johnson "Computation of
Unsteady Incompressible Flows with the Stabilized Finite Element
Methods--Space-Time Formulations, Iterative Strategies and Massively
Parallel Implementations", 9. T. Tezduyar, "Advanced Flow Simulation and Modeling", 10. T. Tezduyar, "CFD Methods for Three-Dimensional Computation of
Complex Flow Problems", |