A series of tests have been conducted using a Cryogenic Wind Tunnel to study the effect of Reynolds number (Re) on the aerodynamic force and surface pressure experienced by a high speed train. The test Reynolds number has been varied from 1 million to 10 million, which is the highest Reynolds number a wind tunnel has ever achieved for a train test. According to our results, the drag coefficient of the leading car decreases with higher Reynolds number for yaw angles up to 30º. The drag force

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... ficient drops about 0.06 when Re is raised from 1 million to 10 million. The side force is caused by the high pressure at the windward side and the low pressure generated by the vortex at the lee side. Both pressure distributions are not appreciably affected by Reynolds number changes at yaw angles up to 30º. The lift force coefficient increases with higher Re, though the change is small. At a yaw angle of zero the down force coefficient is reduced by a scale factor of about 0.03 when the Reynolds number is raised over the considered range. At higher yaw angles the lift force coefficient is reduced about 0.1. Similar to the side force coefficient, the rolling moment coefficient does not change much with Re. The magnitude of the pitching moment coefficient increases with higher Re. This indicates that the load on the front bogie is higher at higher Reynolds numbers. The yawing moment coefficient increases with Re. This effect is more evident at higher yaw angles. The yawing moment coefficient increases by about 6% when Re is raised from 1 million to 10 million. The influence of Re on the rolling moment coefficient around the leeward rail is relatively smaller. It increases by about 2% over the considered range of Re.