Investigation of the turbulent boundary layer and associated energy dissipation in an open channel flow behind a series of regular grids

2014 ◽  
pp. 97-105
Author(s):  
T Earl ◽  
S Cochard ◽  
L Thomas ◽  
L David
Keyword(s):  
Boundary Layer ◽  
Energy Dissipation ◽  
Turbulent Boundary Layer ◽  
Channel Flow ◽  
Open Channel ◽  
Open Channel Flow ◽  
Regular Grids

PIV Study of Separated and Reattached Open Channel Flow Over Surface Mounted Blocks

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
Martin Agelinchaab ◽  
Mark F. Tachie
Keyword(s):  
Boundary Layer ◽  
Shear Layer ◽  
Channel Flow ◽  
Open Channel ◽  
Open Channel Flow ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Mean Velocity ◽  
High Background ◽  
The Mean

A particle image velocimetry is used to study the mean and turbulent fields of separated and redeveloping flow over square, rectangular, and semicircular blocks fixed to the bottom wall of an open channel. The open channel flow is characterized by high background turbulence level, and the ratio of the upstream boundary layer thickness to block height is considerably higher than in prior experiments. The variation of the Reynolds stresses along the dividing streamlines is discussed within the context of vortex stretching, longitudinal strain rate, and wall damping. It appears that wall damping is a more dominant mechanism in the vicinity of reattachment. In the recirculation and reattachment regions, profiles of the mean velocity, turbulent quantities, and transport terms are used to document the salient features of block geometry on the flow. The flow characteristics in these regions strongly depend on block geometry. Downstream of reattachment, a new shear layer is formed, and the redevelopment of the shear layer toward the upstream open channel boundary layer is studied using the boundary layer parameters and Reynolds stresses. The results show that the mean flow rapidly redeveloped so that the Clauser parameter recovered to its upstream value at 90 step heights downstream of reattachment. However, the rate of development close to reattachment strongly depends on block geometry.

scholarly journals Development of River Meander Model

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Levent Yilmaz
Keyword(s):  
Boundary Layer ◽  
Velocity Profile ◽  
Channel Flow ◽  
Open Channel ◽  
Open Channel Flow ◽  
Suspended Sediments ◽  
Flow Region ◽  
Boundary Layer Theory ◽  
Meandering Channels ◽  
Meander Model

In the studies of open-channel flow with suspended sediments, used aconstant of Von Karman κ in a model for velocity profile. The augmentation parameters have been added by various researchers in more recentdevelopment of the boundary-layer theory of meander development. In thisresearch new parameters will be included because of the existence of theturbulent flow region in meandering channels because of boundary-layertheory.

Experimental Study of Shallow Open Channel Turbulent Flows Over Rough Walls

2014 ◽  
Author(s):  
B. Nyantekyi-Kwakye ◽  
E. E. Essel ◽  
S. Clark ◽  
M. F. Tachie
Keyword(s):  
Boundary Layer ◽  
Experimental Study ◽  
Reynolds Number ◽  
Channel Flow ◽  
Open Channel ◽  
Open Channel Flow ◽  
Reynolds Stresses ◽  
Freestream Velocity ◽  
The Mean ◽  
Bed Roughness

An experimental study was undertaken to investigate the effects of bed roughness on the turbulence characteristics of shallow open channel flows. The measurements were performed in a recirculating open channel flow over a reference smooth bed and a three-dimensional rough bed (36-grit sandpaper). The velocity measurements were conducted using a high resolution particle image velocimetry (PIV) system. The Reynolds number based on the depth of flow (h) and freestream velocity (Ue) varied from 21000 to 30000 and the Froude number ranged from 0.46 to 0.65. Two smooth bed experiments were conducted to investigate the effect of Reynolds number on the open channel flow. The mean velocities and Reynolds stresses for the two smooth cases were observed to be weakly dependent on Reynolds number. The effect of bed roughness was observed to penetrate into the outer layer of the boundary layer. The results show that bed roughness significantly increased the skin friction coefficient, wake parameter, boundary layer parameters, as well as the mean velocity, Reynolds stresses and the energy budget terms. A two-point correlation analysis showed that the coherent structures were also significantly modified by bed roughness.

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