Abstract
The chief sources of aerodynamic noise generated by rapid trains are cavities on their surfaces, e.g. bogies under the trains.The shear flow separated from the upstream edge of a cavity impinges on the downstream edge, and frequently alternates flowing into the cavity with flowing out from it.This fluid motion induces noise in low frequency range. A ' scoop deflector ' attached at a downstream edge has been found to be effective to reduce the noise. In this study, in order to determine the most effective dimensions of the scoop deflectors, the noise reduction by scoop deflectors was experimentally investigated by use of a scale model of a two dimensional cavity in a wind tunnel. Considering a train to travel in two directions (i.e. back and forth) along the tracks, a double scoop deflector, a set of scoop deflectors at both upstream and downstream edges, was dealt with. The optimum dimensions of the deflector were obtained; the ratio of the depth to the opening and the ratio of the length to the opening were 0.06 and 0.1, respectively.
