Showing papers on "Wave flume published in 1968"

Closely spaced pile breakwater as a protection structure against beach erosion

Abstract: The theory for the transmission and reflection of the waves at the closely spaced pile breakwater has been developed by the use of shallow water wave theory of small amplitude. Experiment on the hydraulic characteristics of the breakwater has been performed in a two dimensional wave flume. The agreement between the theory and the experiment is pretty good with respect to the coefficients of transmission and reflection of waves, and also to the shoreward velocity of the jet discharged from a space between any two adjacent piles. Experiment was also made on the local scouring at the foot of the clocely spaced pile breakwater. The maximrai scouring depth at the foot of the breakwater relates closely to the ratio of the velocity of the jet to the mean fall velocity of bed material. The relation between the maximum scouring depth and the power of the jet is discussed.

The Dynamics of Fixed Towers in Deep Water Random Waves

Abstract: This paper is concerned with the design of offshore, bottom-supported structures which are subject to deflections and stresses due to deep water wave forces. Both periodic and random waves are considered. It is shown that the wave force on the structure can be adequately expressed by the inertia force component and that this linearization of the wave force expression leads to a criterion for the optimum spacing of structural supports which is a function of the random wave spectrum. Equations for the dynamic response of the platform are developed. The theoretical considerations were verified experimentally and the results indicated that for structures designed with optimum support spacing, the magnitude of structural response is relatively insensitive to wave direction.

Turbulent Flow Over Moving Boundary

Abstract: To gain a better understanding of the mechanism of energy transfer from wind to an already formed small amplitude gravity water wave, pressure and velocity measurements were performed in a model in which the wave surface was reproduced by a wavy boundary moving at constant speed. Experiments were carried out in a water flume with two different sets of sinusoidal shape wavy boundaries under fixed and moving conditions. It was found that, while the pressure distribution was almost symmetrical when the boundary was fixed, it displayed a noticable phase-lag with respect to the waves shape when the boundary was moving, which accounts for the energy transfer from wind to wave because of the normal stress. Within the limitations of experimental accuracy the data coincides with the curves computed for each case from Miles' mathematical theory. In addition, flow visualization experiments provided a qualitative verification of the existance of a stationary vortex over the wave, as predicted by Lighthill in his physical explanation of the phenomena.