scholarly journals Influence of Flood-Plain Roughness on Turbulent Structure in Open Compound Channel Flows

1993 ◽  
Vol 37 ◽  
pp. 587-592
Author(s):  
Akihiro TOMINAGA
Keyword(s):  
Flood Plain ◽  
Turbulent Structure ◽  
Channel Flows ◽  
Compound Channel

Drag reduction and turbulent structure in two-dimensional channel flows

1991 ◽  
Vol 336 (1640) ◽  
pp. 19-34 ◽  
Keyword(s):  
Shear Stress ◽  
Drag Reduction ◽  
Strain Rate ◽  
Reynolds Stress ◽  
Polymer Concentration ◽  
Turbulent Structure ◽  
Channel Flows ◽  
Channel Height ◽  
Normal Velocity ◽  
Two Dimensional

A two-component laser velocimeter has been used to determine the effect of wall strain rate, polymer concentration and channel height upon the drag reduction and turbulent structure in fully developed, low concentration, two-dimensional channel flows. Water flows at equal wall shear stress and with Reynolds numbers from 14430 to 34640 were measured for comparison. Drag reduction levels clearly depended upon wall strain rate, polymer concentration and channel height independently.However, most of the turbulent structure depended only upon the level of drag reduction. The slope of the logarithmic law of the wall increased as drag reduction increased. Similarly, the root-mean-square of the fluctuations in the streamwise velocity increased while the r.m.s. of the fluctuations in the wall-normal velocity decreased with drag reduction. The production of the streamwise normal Reynolds stress and the Reynolds shear stress decreased in the drag-reduced flows. Therefore it appears that the polymer solutions inhibit the transfer of energy from the streamwise to the wall-normal velocity fluctuations. This could occur through inhibiting the newtonian transfer mechanism provided by the pressure-strain correlation. In six drag-reducing flows, the sum of the Reynolds stress and the mean viscous stress was equal to the total shear stress. However, for the combination of highest concentration (5 p.p.m.), smallest channel height (25 mm) and highest wall strain rate (4000 s - 1 ), the sum of the Reynolds and viscous stresses was substantially lower than the total stress indicating the presence of a strong non-newtonian effect. In all drag-reducing flows the correlation coefficient for uv decreased as the axes of principal stress for the Reynolds stress rotated toward the streamwise and wall-normal directions.

Parameter optimization in modelling unsteady compound channel flows

1992 ◽  
Vol 19 (3) ◽  
pp. 441-446 ◽  
Author(s):  
Habib Abida ◽  
Ronald D. Townsend
Keyword(s):  
Parameter Optimization ◽  
Optimization Methods ◽  
Flood Plain ◽  
Flood Routing ◽  
Compound Channel ◽  
Flood Events ◽  
Channel Section ◽  
Simplex Methods ◽  
Boundary Roughness ◽  
Good Agreement

Optimization methods are used to estimate data for routing floods through open compound channels (main channels with flood plain zones). These data include the irregular channel section geometry and the varying boundary roughness. Differences between simulated and observed stages and discharges are minimized using three optimization algorithms: Powell's method, Rosenbrock's algorithm, and the Nelder and Meade simplex method. Powells' method performed poorly; however, both the Rosenbrock and simplex methods yielded good results. The estimated data using the Rosenbrock and simplex methods were used to route different flood events observed in a laboratory channel. Simulated peak stages and discharges were in good agreement with those estimated using actual routing data. Key words: compound channel, flood routing, lateral momentum transfer, optimization, unsteady flow.

scholarly journals Discharge Assessment for Compound Channel Flows

1990 ◽  
Vol 34 ◽  
pp. 415-420
Author(s):  
Akira MUROTA ◽  
Teruyuki FUKUHARA ◽  
Masanori SETA
Keyword(s):  
Channel Flows ◽  
Compound Channel

Turbulent Structure and Coherent Vortex over the Dune Bed in Open-Channel Flows

1989 ◽  
Vol 33 ◽  
pp. 475-480
Author(s):  
Hiroji NAKAGAWA ◽  
Iehisa NEZU ◽  
Toshimori MATSUNOTO ◽  
Fumihiko KANAZAWA
Keyword(s):  
Open Channel ◽  
Turbulent Structure ◽  
Channel Flows ◽  
Open Channel Flows ◽  
Coherent Vortex
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