The Effect of Wave-damping on the Surface Velocity of Water in a Wind Tunnel

Abstract

A laboratory wind tunnel has been used to study the movement of the surface of a body of water over which a wind is blowing. The ratio of the surface velocity Us to the wind velocity V has been measured for both smooth and wavy surfaces at wind speeds between 350 and 750 cm/s. It has been found that this ratio is markedly affected by the damping-out of surface waves. For a wavy surface, as obtained with clean water, us/V has a constant value of about 0·03. The damping of the surface waves is achieved by the addition of detergent solution to the water. There is a particular concentration of detergent, and a corresponding surface pressure, at which u s/ V ceases to have this constant value and begins to rise to' values around 0·045. For a fully damped surface us/V rises linearly with V for low wind speeds and tends to a constant value of 0·045 for wind speeds greater than 550 cm/s. These findings are, to some extent, in conflict with the observations and theories of previous workers.