SIMILARITY CRITERIA OF WIND-DRIVEN CURRENT AND MODEL SCALE OF WIND VELOCITY

Studies on modelling techniques in wind-induced hydraulic phenomena in freshening reservoir (II)

Abstract

In order to realize the distorted hydraulic reservoir model on which the various tests with respect to wind-wave interactions may be made, the similarity criteria of the wind-driven circulation in shallow freshening reservoir is theoretically discussed in this paper. The model scale of wind velocity, λ_w, defined as the ratio of the model wind velocity at a certain height ζ_m to the prototype wind velocity at a unique height above the undisturbed surface, is ultimately determined. Before we arrive at λ_w, the model scale of wind stress coefficient, λ_s, related to λ_w, is expressed in terms of λ_w and λζ_c equal to ζ_m/10.0 through introducing the Wu's concept that the range of wind velocity may be divi-ded into breeze, light wind and strong wind regimes. Finally, we find throughout the present paper that the distortion of a scale model should be small from a viewpoint of the similarity of wind velocity, and that the numerical values of λ_w for three regimes are very like each other if a hydraulic model with certain geometric scales is designed.