Numerical modelling of train aerodynamics in confined space

Geographical limitations have always been a major concern in Singapore. As demand for a more efficient transport system to accommodate the rising population increases, alternatives such as underground spaces have been explored and made available. The most recent example is the newly introduced Downtown Line which have exploited the spaces Singapore can offer underground. With the transport lines built underground, trains are expected to operate in confined spaces over a long period of time. The objective of this project is to study the aerodynamics behavior of the airflow around the train as it travels through the tunnel. Simulations of several positions of the train with respect to the tunnel were performed using Computational Fluid Dynamic (CFD), using a commercial software ANSYS FLUENT. Results achieved revealed presence of huge pressure fluctuations over the train's surface. Pressure variances and different distribution at different train positions relative to the tunnel can also be observed. The exposure to pressure variation can sometimes have an impact on the structural integrity of the train. If high-speed trains were to be used in the future, these pressure variations would have a profound, if not catastrophic impact on the trains if they are not designed adequately. Besides the external train structure, proper sealing of the train doors is equally important. In an event of air leakage, passengers will feel discomfort due to the high differential in pressure.