入口速度比对射流拟序结构的影响

为了深入了解湍流流动机理以及湍流拟序结构发现过程的影响因素，本文采用大涡模拟方法对不同入口射流伴流速度比的平面湍射流流动进行了数值模拟。采用分步投影法求解动量方程，亚格子项采用标准Smagorinsky亚格子模式模拟，压力泊松方程采用修正的循环消去法快速求解，空间方程采用二阶精度的差分格式，在时间方向上采用二阶精度的显式差分格式。模拟结果给出了平面射流中湍流拟序结构的瞬态发展演变过程，分析了入口速度比对射流拟序结构发展演化过程及宏观流场形态的影响。为进一步研究射流拟序结构及其在湍流流动中的作用提供了基础。

Influences of inlet velocity ratio on coherent structures in planar jets

Turbulent jet flow is the most widely used flow type in engineering applications. Most proportion of energy transportation and conversion processes is dominated by transient evolution of the large\|scale structures, or the coherent structures, in turbulent jets. In this paper, two\|dimensional spatial developing turbulent planar jets with different velocity ratios of jet fluid to co\|flow fluid at the inlet section are simulated with large eddy simulation approach in order to give detailed information of transient behaviors of coherent structures in turbulent jets and how the velocity ratios affect evolution of coherent structures. Transient distributions of velocity are obtained at different evolution periods of turbulent jets, and evolutions of coherent structures in flow field are also given. Filtered nondimensionalized governing equations are solved with standard Smagorinsky sub\|grid scale model, and transport equation of passive scalar is also solved in order to perform numerical visualization of flow field. Numerical simulation is performed by Chorin's fractional step method. Buneman variant of cyclic odd\|even reduction algorithm is adopted for solving pressure correction Poisson equation.Simulation results show structures of flow field at different velocity ratios and the transient evolution process of coherent structures in planar jets as well as the interaction between velocity ratio and coherent structures and explain the existence of the potential core region in turbulent jets. Results of this paper may provide basis for control and optimization of engineering applications associated with turbulent jet flows.