Open‐channel Flow Measurements with a Laser Doppler Anemometer
- 1 May 1986
- journal article
- Published by American Society of Civil Engineers (ASCE) in Journal of Hydraulic Engineering
- Vol. 112 (5), 335-355
- https://doi.org/10.1061/(asce)0733-9429(1986)112:5(335)
Abstract
A powerful two‐color Laser Doppler Anemometer (LDA) system, with direct digital signal processing has been used to measure accurately the longitudinal and vertical velocity components in two‐dimensional, fully‐developed open‐channel flow over smooth beds. The law of the wall and the velocity defect law were re‐examined because the log‐law has been often applied to open channels without detailed verification. It was found that the log‐law can be applied strictly only to the near‐wall region. In this region, the von K´rm´n constant κ and the integral constant A are truly universal, having values of κ=0.412 and A=5.29 irrespective of the Reynolds and Froude number. As the Reynolds number becomes larger, the deviation from the log‐law cannot be neglected in the outer region. This deviation can be expressed well by Coles' wake function which involves a Reynolds‐number dependent parameter Π. The distributions of eddy viscosity and mixing length were evaluated and found to depend on Π. All the data including the...Keywords
This publication has 19 references indexed in Scilit:
- Turbulence structure and transport mechanism at the free surface in an open channel flowInternational Journal of Heat and Mass Transfer, 1982
- Structure of space-time correlations of bursting phenomena in an open-channel flowJournal of Fluid Mechanics, 1981
- Eddy diffusivity near the free surface of open channel flowInternational Journal of Heat and Mass Transfer, 1977
- TURBULENCE OF OPEN CHANNEL FLOW OVER SMOOTH AND ROUGH BEDSProceedings of the Japan Society of Civil Engineers, 1975
- The structure of the viscous sublayer and the adjacent wall region in a turbulent channel flowJournal of Fluid Mechanics, 1974
- Measurements of the radial and tangential eddy diffusivities of heat and mass in turbulent flow in a plain tubeInternational Journal of Heat and Mass Transfer, 1972
- A note on von Kármán's constant in low Reynolds number turbulent flowsJournal of Fluid Mechanics, 1972
- Structural features of turbulent flow over smooth and rough boundariesJournal of Fluid Mechanics, 1971
- A Study of Incompressible Turbulent Boundary Layers in Channel FlowJournal of Basic Engineering, 1968
- The law of the wake in the turbulent boundary layerJournal of Fluid Mechanics, 1956