THE MEASUREMENT OF TRAIN SLIPSTREAM CHARACTERISTICS USING A ROTATING RAIL RIG

Abstract. This paper presents the results of a new experimental technique to determine the structure of train slipstream velocities. The highly turbulent non stationary nature of the slip-streams make their measurement difficult and time consuming as in order to identify the trends of behaviour several passings of the train have to be made. This new technique has been developed in order to minimise considerably the measuring time. It consists of a rotating rail rig to which a 1/50th scale model of a three coach train is attached. Flow velocities were measured using a pressure transducer, Cobra probe (Turbulent Flow Instrumentation), posi-tioned close to the model side. Tests were carried out at different model speeds. Velocity time histories for each configuration were obtained from ensemble averages of the results of a number of runs. Although this technique allows carrying out the tests more rapidly there are significant problems with the proposed methodology, which will be detailed below. This in-vestigation sets out to quantify these issues and to determine the level of experimental accu-racy that might be obtained, using both experimental measurements and CFD calculations to bridge the gap between the proposed methodology and current measurement methods