超声速混合层液滴两相流动的大涡模拟

Large eddy simulation of two-phase mixing layer with droplets

关键词:  大涡模拟  两相流  混合层  液滴

Key words:  Large eddy simulation  Two-phase flow  Mixing layer  Droplets

摘要:

为研究超声速气流中液滴与气流的混合及液滴蒸发对混合的影响,采用大涡模拟(LES)方法数值仿真了超声速混合层内液滴两相流流场结构,气相流场采用亚格子(SGS)模型和切应力输运(k-ωSST)湍流模型,液相模拟采用轨道模型和单液滴蒸发模型。在混合层前缘入口处均匀持续地投放液滴,并在液滴入口处下方添加非周期小扰动,并观察液滴蒸发过程对该小扰动造成的影响。分析了入口小扰动在流场中不同的发展情况,发现液滴的蒸发过程使混合层厚度增加并加速混合层的发展,对气相流场扰动较强,可能导致流动失稳,对混合过程有很大的促进作用。

Abstract:

To study the mixing course of droplets and gas and the effect of evaporation on mixing in supersonic mixing layer,the two-phase supersonic mixing layer with droplets was simulated by the method of large eddy simulation(LES).The SGS sub-grid model and the k-ω SST turbulence model were adopted to calculate the gas phase of the flow.The track model and the single droplet evaporation model were used to simulate the liquid phase.The droplets were uniformly and continuously put in the flow in the front of the mixing layer at the inlet.The non-period micro-disturbances were added to the flow below the droplets inlet,and the influence of the droplets evaporation on the micro-disturbance were observed.The differences between developments of the micro-disturbance indicated that the course of evaporation would obviously increase the thickness of mixing layer and accelerate the development of mixing layer.The evaporation disturbs the gas phase flow distinctly,which would probably lead to unstable flow and enhance the flow mixing course.