開水路流れにおける乱れ特性量の普遍関数表示について (2)

Abstract

This paper describes an experimental investigation of the profiles of mean velocitiesand some turbulence properties in a two-dimensional free surface shear flow. The exper-iments were performed under the condition of greater aspect ratio than 10, to obtain thetwo-dimensional flow in a rectangular open channel.The experimental results show that the mean velocity profiles are well described bythe logarithmic distribution, and that the Karman constant k and the integral constantAs, Ar may be treated as constants which are independent of the Reynolds number, theFroude number and the relative roughness height. However, the values of theses con-stants in a free surface shear flow are somewhat different from these in a pipe flow, andthe following values may be recommended, that is, k=0.33, As=2.2 and Ar=8.3.According to the Reynolds number similarity, the turbulence properties are normalizedwith the flow depth, the friction velocity and the local mean velocity. And the verticaldistribution of the normalized turbulence properties, such as, the turbulence intensity, theEulerian mean scale, the energy dissipation rate, the Taylor's dissipation scale, the Kol-mogorov's lacal scale, the Lagrangian mean scale and the turbulent diffusion coefficientare described by the universal function of the relative depth, respectively.