A Study of The Turbulent Flows behind A Rectangular Sharp Crested Weir in Open Channel Using Laser Doppler Velocimetry (Dept.C)

M Attia

doi:10.21608/bfemu.2020.127477

Abstract

This paper describes the experimental investigation using laser Doppler velocimetry) (LDV) in the downstream of .be rectangular sharp crested weir in a horizontal rectangular channel of constant width. The study was carried out for flows on smooth and rough weir. For precise and accurate measurements of mean and fluctuating a ting flow characteristics such as streamwise and vertical turbulence intensity components and streamwise and vertical mean velocity components. The depthwise measurements were carried out for different heights of the weir along to e centerline at different cross sections downstream of weir in the wake region . The results show that, the measured values of turbulence intensities are found to have high level of turbulence in the Dear wake region but are low in the far wake region. The turbulence intensities depict the occurrence of a constant turbulence close to the wall in the far wake region. The roughness was found to increase the turbulence. Also, it can be seen that with increasing weir height, the turbulence intensities are Increased.

Highlights

Flow fi elds associated with separation re ll.ltachment configuration, the flow beh ind and reattachment have received significant rectangular shar p crested weir
I.e. the determination of mean and fluctuating flow quantities such as streamwise and vertical components of turbulence intensity, and streamwise and verticRI mean velocity components, A detailed review of the two-dimensional situations has been offered by Bradshaw and Wong 141 and later by Eaton
The experimental study on Ihe turbulent flows behind a rectangular sharp vertical mean "c1ocity cOlllpollell[1] vI Uo is observed to be small comp ared 10 Ihe crested weir in open cbannel indicates that: The turbulen ce intensities have a high streamwise mean velocity iIfU o Regardless of its magnitude, measuremenr of the vertical level of turbulence in the near-wake region, In the far-wake region the intensities arc smaUcr and Ihe profiles arc similar in velocity is a new finding using LDV

Summary

Introduction

Flow fi elds associated with separation re ll.ltachment configuration, the flow beh ind and reattachment have received significant rectangular shar p crested weir. Examples ,include the rectangular sbarp crested wei r, the simple flow behind the back ward~ facing step, geome try nnd the attainable two separated flow in diffusers, and separation dim ensiona lity of the test flow facilitate the bubbles on airfoils. Among these separation analys is of separation indu ced fl ow Accepled September IS, 2008 C. I.e. the determination of mean and fluctuating flow quantities such as streamwise and vertical components of turbulence intensity, and streamwise and verticRI mean velocity components, A detailed review of the two-dimensional situations has been offered by Bradshaw and Wong 141 and later by Eaton

Methods

Results

Conclusion