用于可压缩自由剪切流动的湍流混合长度

抓住可压缩流动变密度特性,构造出基于有效涡量的三维von Karman混合长度。湍流模型采用仅依赖湍动能k的单方程KDO(Kinetic Dependent Only)模型,引入新构造的混合长度替换旧尺度得到CKDO模型。为了验证其描述可压缩自由剪切湍流的能力,选择无壁面束缚、密度梯度大和可压缩效应强的自由剪切混合层为算例,其对流马赫数Ma_c=0.8。计算结果表明,KDO模型对混合层的速度分布有着良好的控制和模拟,而经可压缩修正后的CKDO模型与原模型及其他可压缩修正模型相比,所计算的速度分布、主雷诺剪切力和混合层厚度与试验结果更加接近,说明了该混合长度对可压缩混合层这种自由剪切湍流有着良好的刻画能力。

Turbulence mixing length for compressible free shear flows

Seizing compressible flow variable density characteristics,a three-dimensional von Karman mixing length scale based on the effective vorticity has been constructed. This paper adopts a single-equation turbulence KDO (Kinetic Dependent Cnly) model which depends only on the turbulent kinetic energy equation, and introduces a new structure which replaces the old mixing length scale to obtain CKDO model. Then in order to verify its ability to describe compressible free shear turbulence, we select the compressible mixing layer of no wall bondage, large density gradient and strong compressibility effects as an example, whose convective Mach number is 0.8. The results show that KDO model has good control and simulation ability of mixing flow velocity distribution; compared with the original model and other compressible correction models, the velocity distribution, primary Reynolds shear stress and mixing layer thickness obtained with compressible correction model CKDO have a better fit with the experimental value. The results illustrate that the new mixing length has a good ability of characterization for compressible free shear turbulent mixing layer.