Numerical and experimental analysis of drag force in medium speed train design

Aerodynamic drag is the highest portion of the overall resistance force in a high speed train. More streamlined design will have lower coefficient of drag. Therefore, improving the mask of car and carbody is essential to minimise the drag force. This study aims to obtain the value of the drag coefficient on the design of Indonesia's Medium Speed Train which has an operational speed of 160 km/h by the numerical method and then to validate it with the wind tunnel experimental test. In the initial stage, two designs was developed using a 3D CAD software. Subsequently, a CFD simulation was performed to determine the value of the drag coefficient. Two test models were built with a scale of 1:25, then both were tested in a wind tunnel. Based on the test results, the coefficient of drag of both models have relatively similar value. The graph data from the CFD simulation results then compared to the wind tunnel results. In addition, the wind speed variations was conducted to observe the effect of the Reynolds number on the drag coefficient.