Regime of Oscillatory Flow

Abstract

A regime of flow is defined as the transition from laminar to turbulent flow which is an inception of turbulence in the flow field. Knowledge of flow regime provides useful information for quantitative description of flow and its analysis. It also serves as the lower limit of sediment transport. Earlier regimes of flow are very compliated because of their various types of flow and bed roughness. In this study an analysis is made of regime of flow using known published data tested in oscillating beds, wave flumes and water tunnels over loose sediment beds and rigid ripple beds, as well as wave flume data tested by the author. The approach is based on a dimensional consideration and a derivation of theoretical regimes of flow. It is found that the theoretical regimes of flow which are expressed in terms of flow Reynolds number and relative smoothness of the bed can be used for loose sediment beds but cannot be used for ripple beds of larger roughness. A unique regime of flow which is expressed in terms of sediment Froude number and relative bed smoothness is obtained from its proper fitting to the experimental data from all types of flow and bed roughness. The appropriate dimensionless parameter “the relative bed smoothness” reveals automatically the condition of its roughness.