Accession Number : AD0638728

Title :   AN EXPERIMENTAL INVESTIGATION OF THE GENERATION OF WATER WAVES BY AIR SHEAR FLOWS.

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE AEROELASTIC AND STRUCTURES RESEARCH LAB

Personal Author(s) : Gupta,Ashok Kumar

Report Date : JUN 1966

Pagination or Media Count : 142

Abstract : A tank of length 46 in., width 12 in., and depth 5 1/4 in., tipped with a 4 1/2 in., long aluminum plate was filled with ordinary tap water and was placed parallel with a uniform air stream of low turbulence. Visual observations of the water free surface were made in the air speed range of 2 FPS to 26 FPS. (1) Allowing for the effects of slightly accelerating air flow and the finite length of the tank, the measured mean velocity profiles of the laminar air boundary layer agree in all essential aspects with Lock's velocity profile computed for zero pressure gradient. (2) Water wave generation by wind with laminar boundary layers consists of two phenomena: maintenance of water wave and initiation of water wave. A relatively low air speed can maintain a relatively long water wave but cannot initiate it. For the laminar boundary layer water waves of wavelengths 2 to 3 cm first appear at air speeds of 530 to 595 cm/sec. For the turbulent boundary layer the water waves first appear at air speeds of 350-400 cm/sec. (3) For air speeds greater than 23 FPS with the boundary layer laminar a Kel. Helm. type instability seems to occur. (4) Customary plots of neutral oscillations of Tollmien Schlichting waves modified by the water surface made for air speeds of 11.3, 17.5 and 20.6 FPS suggest a destabilising effect of the water surface.

Descriptors :   (*WATER WAVES, PRODUCTION), FLUID MECHANICS, GAS FLOW, AIR, WIND, LAMINAR BOUNDARY LAYER, VELOCITY, BOUNDARY LAYER, SURFACES

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE