绕钝体分离流动的非定常数值模拟研究

The unsteady numerical simulation of separated flow around bluff bodies

利用非定常RNGk-ε模型对三种典型的钝体绕流问题进行了研究,这三种流动分别为:方柱绕流、圆柱绕流和绕立方柱流动。研究表明了采用非定常雷诺平均方法可以研究钝体绕流的非定常流动,但所获得的结果各不相同。对于分离角固定的方柱绕流和绕立方柱流动,数值模拟结果和实验以及大涡模拟结果吻合较好,对于分离角不固定的圆柱绕流,随着雷诺数的增加,数值模拟结果和实验结果相差越大,分析认为这是由于壁面模型无法准确预测流动中不固定的分离角所致。改进了绕立方柱流动的模拟方法,采用非定常模拟方法后获得的结果要比定常模拟方法得到的结果有了根本改善。

Three typical flows around bluff bodies were studied by using unsteady RNG model. These three flows are： flow around a square cylinder, flow around a circular cylinder and the 3D flow past a surface-mounted cube. It shows we can use unsteady Reynolds average numerical simulation method to study these flows of unsteady bluff bodies while we get different results. Numerical simulation is quite validated against experiment and LES simulation data for flow around a square cylinder and the 3D flow past a surface-mounted cube with fixed separated angle. For unfixed separated angle of flow around a circular cylinder, numerical simulation data is more and more different with experiment result with increasing Reynolds number. It is thought to be that wall model can not exactly predict unfixed separated angle in that flow. By improving this simulation method for the 3D flow past a surface-mounted cube and adopting unsteady computation method, we can get much better results compared to steady numerical simulation.