Method of Measuring the Aerodynamic Drag of Trains

抄録

The running resistance of a train is composed of two parts, i.e. mechanical resistance and aerodynamic one. The ratio of the latter to the former increases remarkably with train speed, so it is very important for the planning of high speed trains to estimate the aerodynamic drag accurately. We have, however, only insufficient knowledges about it so far. In the test using actual trains, only the total running resistance could be measured and aerodynamic drag could not be obtained separately. And also in the model test in a wind tunnel it was practically impossible, though possible in principle, to obtain quantitatively accurate data, because of the inevitable reduction of model size and of the difficulties of experiments using models with rolling wheels and moving ground. As such was the case, there was no way but to rely on unsatisfactory data. The author found that the aerodynamic drag is closely related with the pressure rise on the side surface of a train, when it rushes into a tunnel, and that the aerodynamic drag can be obtained from this pressure rise independently of mechanical resistance. The mean aerodynamic drag coefficient of streamlined trains obtained through this method can be expressed as follows : c_D=0.12+0.0075x where x is the length of a train measured in meters.