Abstract
Hydrodynamic forces exerting on a squire pillar (length d) with angle of attack α, placed in the unsteady free surface shear flow, are investigated experimentally, being varied in the range of α=0°-45°. It is found that the assumption of hydrostatic pressure distribution at the front and back side of the pillar is not valid for the case of unsteady free surface shear flow and hydrodynamic force changes with the pressure difference Δh between the front and back side of the pillar. It is shown that Δh/d is dependent on the gradient dh/dx of water surface calculated from Ritter solution and Δh/d increases with |dh/dx|, and the drag coefficient Cd is smaller than that in uniform flows.
