Conference proceeding
Spatial development of a constant-depth shallow mixing layer in a long channel
RIVER FLOW 2014, pp.155-161
2014
Abstract
The spatial development of a shallow mixing layer near the free surface is studied using results from a high-resolution eddy-resolving numerical simulation. The shallow mixing layer forms between two parallel streams that are initially separated by a thin splitter plate. The ratio between the bulk velocity of the two streams is equal to 2.3 and the Reynolds number defined with the mean velocity of the two streams and the channel depth is Re = 15,500. The mixing layer develops in a long constant-depth open channel with a flat smooth bed. The length of the channel in the simulation is equal to 400D, where D is the channel flow depth. This length is about two times larger than the channel length used in an experiment conducted with similar flow conditions, which is used to validate the numerical predictions over the upstream part of the channel. The larger channel length used in the numerical simulation allows studying the spatial evolution of the shallow mixing layer at conditions that are close to the equilibrium regime when the destabilizing effect of the mean shear between the two streams is compensated by the stabilizing effect of the friction acting on the mixing layer eddies at the bed. It is found that numerical predictions of the mean streamwise velocity profiles and the streamwise variation of the mixing layer width at the free surface are in good agreement with the experiment. Though simulation results also show a close to linear decay of the entrainment coefficient a with the bed friction factor, S, over the upstream part of the mixing layer, the rate of decay of a with S reduces significantly over the downstream part of the channel where the mixing layer approaches equilibrium. Spectral analysis of the velocity time series is used to estimate how the size and dominant passage frequency of the large-scale quasi-2D horizontal coherent structures forming within the shallow mixing layer vary as a function of the distance from the mixing layer origin.
Details
- Title: Subtitle
- Spatial development of a constant-depth shallow mixing layer in a long channel
- Creators
- Z ChengG Constantinescu
- Contributors
- M Pfister (Editor)
- Resource Type
- Conference proceeding
- Publication Details
- RIVER FLOW 2014, pp.155-161
- Language
- English
- Date published
- 2014
- Academic Unit
- Civil and Environmental Engineering
- Record Identifier
- 9984231918002771
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