Experimental Study on Secondary Circulation of Flow in a Wind Tunnel Basin

Abstract

Two velocity components of subsurface flow, observed in a rectangular wind tunnel basin equipped with a water circulation pump system, are measured over a vertical cross-section of the basin. Measurements are carried out for three cases: 1) reference wind speed U_a=8.4m/s without water current; 2) U_a=8.4m/s with current velocity U=10cm/s; and 3) U_a=8.4m/s with current velocity U=-10cm/s. A pair of secondary circulations is observed in a cross-section of the flow in the basin for each case: in the case-1 and case-3, a downwelling zone is found along the sidewall and an upwelling zone in the centre of the basin; and in the case-2, an upwelling zone is found along the sidewall and a downwelling zone in the centre of the basin. It is estimated that the velocity of the secondary circulations would be about 7-50% of the mainflow velocity.