REFINEMENT OF A DEPTH-AVERAGED RANS MODEL FOR OPEN CHANNEL FLOWS WITH SHEAR INSTAILITY

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  • せん断不安定のパラメータ依存性を考慮した平面二次元ＲＡＮＳモデルの構築
  • センダンフアンテイ ノ パラメータ イソンセイ オ コウリョ シタ ヘイメン ニジゲン RANS モデル ノ コウチク

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We developed a new RANS turbulence model for simulating flows with large scale vortex formations due to the shear instability. In this model, the eddy viscosity is set locally larger where the turbulence level is increased due to vortex shedding. The eddy viscosity is expressed by the summation of two terms, i.e., (i) effect of turbulence in a base flow and (ii) contribution by the vortex formations. The first term is set in proportion with the product of the local depth and the local friction velocity. For the second term, we considered two dimensionless parameters, i.e., Froude number and the bed friction number. The second term is modelled with the previous theoretical studies on the effects of those parameters on instability. The present model is validated through the comparison with the experimental data by Chu and Babarutui (1988) in parallel shear flows. Computational results showed that the present approach could capture well the velocity profiles around the shear layer even if a coarser computationlgrid is employed.

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