An Experimental Investigation of the Structure of a Turbulent Wind Over Water Waves PDF Download

Author: Susumu Karaki
Publisher:
ISBN:
Category : Ocean waves
Languages : en
Pages : 126

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Book Description
This investigation presents experimental results from a study of the structure of a turbulent boundary layer developed by air flow over water waves in a lab wind-wave channel. It was demonstrated that the sheared flow region is two-layered, similar to rough wall boundary layers. The inner layer, adjacent to the wall, is describable by the 'law of the wall' and the outer flow by the 'defect law.' The data were taken in two-dimensional flow with small favorable pressure gradients. The first part of the two-part investigation involved air flow over an initially still water surface on which waves developed in response to wind excitation. In the second part, air was passed over water waves of a single frequency and varied amplitude. The results indicated that within the range of this study the water surface can be classed as aerodynamically rough at wind speeds greater than 12 fps and the flow structure of the boundary layer corresponds to that over a rough wall. The velocity decrement due to surface roughness is shown to be a function of the local root-mean-square wave height. The effect of wave-induced fluctuations in the air is limited to a very close neighborhood of the wavy surface. For the specific combination of wind and wave speeds of this study it was found that while the amplitudes of the horizontal components of the fluctuation decreased with increasing elevation, the vertical component increased. (Author).