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为预测粗糙壁面诱导的流动转捩,对Langtry提出的γ-Reθ转捩模型增加粗糙壁面的比耗散率和涡黏性的边界条件,并对模型中的经验关联函数——转捩动量厚度雷诺数进行修正,引入等效沙粒表面粗糙度作为变量,使模型具有一定的预测粗糙壁面诱导的流动转捩的能力.对粗糙平板自然转捩算例和变压力梯度平板绕流算例进行数值模拟,计算结果与风洞实验数据符合的较好.主要结论如下:表面粗糙度一般会增加边界层内的传热系数和阻力系数,同时使层流到湍流的转捩位置提前;自然转捩的转捩位置受表面粗糙度影响较大,与光滑壁面相比,平板算例中0.15mm的表面粗糙度使转捩位置提前40%;分离诱导转捩的转捩位置受表面粗糙度影响较弱,随着表面粗糙度逐渐增加,转捩位置和分离泡位置略有后移,且分离泡强度逐渐减弱,分离泡之后的阻力系数增加.
To predict the wall-induced flow transition, the Langtry proposed γ-Reθ transition model was used to increase the boundary conditions for the specific dissipation rate and eddy viscosity of the rough wall. The empirical correlation function in the model, Reynolds number is modified to introduce the equivalent surface roughness of sand as a variable, so that the model has the ability of predicting the flow transition induced by the rough wall.An example of rough plate natural transition and variable pressure gradient plate flow The main results are as follows: The surface roughness generally increases the heat transfer coefficient and drag coefficient in the boundary layer, and at the same time makes the position of laminar flow to turbulent flow advance ahead of time. Natural rotation The turning position of 捩 is greatly affected by the surface roughness. Compared with the smooth surface, the surface roughness of 0.15mm in the flat plate example leads to a 40% advancement of the turning position. The position of the turn induced by the separation inducing transfer is affected by the surface roughness Weak, with the surface roughness gradually increased, the transfer position and separation of the bubble position slightly backward, and the separation of the bubble strength gradually weakened, after the separation bubble increases the drag coefficient.