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In the present paper, a new dynamic subgrid-scale (SGS) model of turbulent stress and heat flux for stratified shear flow
is proposed. Based on our calculated results of stratified channel flow, the dynamic subgrid-scale model developed in this
paper is shown to be effective for large eddy simulation (LES) of stratified turbulent shear flows. The new SGS model is then
applied to the LES of the stratified turbulent channel flow to investigate the coupled shear and buoyancy effects on the behavior
of turbulent statistics, turbulent heat transfer and flow structures at different Richardson numbers. 相似文献
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Performance of supersonic model combustors with staged injections of supercritical aviation kerosene 总被引:1,自引:0,他引:1
Supersonic model combustors using two-stage injections of supercritical kerosene were experimentally investigated in both Mach 2.5 and 3.0 model combustors with stagnation temperatures of approximately 1,750 K. Supercritical kerosene of approximately 760 K was prepared and injected in the overall equivalence ratio range of 0.5-1.46. Two pairs of integrated injector/flameholder cavity modules in tandem were used to facilitate fuel-air mixing and stable combustion. For single-stage fuel injection at an upstream location, it was found that the boundary layer separation could propagate into the isolator with increasing fuel equivalence ratio due to excessive local heat release, which in turns changed the entry airflow conditions. Moving the fuel injection to a further downstream location could alleviate the problem, while it would result in a decrease in combustion efficiency due to shorter fuel residence time. With two-stage fuel injections the overall combustor performance was shown to be improved and kerosene injections at fuel rich conditions could be reached without the upstream propagation of the boundary layer separation into the isolator. Furthermore, effects of the entry Mach number and pilot hydrogen on combustion performance were also studied. 相似文献
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冲击射流结构中应用粗糙表面的实验研究 总被引:1,自引:0,他引:1
在单侧开口的冲击射流冷却结构中,逐步增加的横流将影响冲击板上的对流换热效率,本文提出了压窝板和肋片板两种粗糙冲击板构型,增加横流的扰动以减少对冲击流的影响并且增大横流与壁面的对流换热。实验采用瞬态热敏液晶测量方法,可以得到大尺度壁面的二维对流换热系数分布,可以较为系统地分析压窝及肋片周围的局部换热系数分布。通过实验研究,发现压窝板可以显著增大平均换热系数,而肋片板降低了平均换热系数。 相似文献
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采用大涡模拟(LES)方法,并结合动力学亚格子尺度应力(SGS)模型,通过数值求解柱坐标系下的滤波Navier-Stokes方程,研究了绕管轴旋转圆管内的湍流流动特性.为验证计算的可靠性,以及动力学SGS模型对于旋转湍流的适用性,将大涡模拟计算所得的结果,与相应的直接模拟(DNS)结果和实验数据进行了对比验证,吻合良好.进一步对旋转圆管湍流的物理机理进行了探讨,研究了湍流特性随旋转速率的变化规律.当旋转速率增加时,湍流流动有层流化的发展趋势.基于湍动能变化的关系,分析了旋转效应对湍流脉动生成的抑制作用. 相似文献
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利用高来流马赫数为3, 5, 6, 7, 10的槽道湍流直接数值模拟(direct numerical simulations, DNS)数据, 评估和修正经典的参考焓值法. 研究表明在高来流马赫数槽道湍流中, 经典参考焓值法预测的壁面热流与DNS结果相差很大, 需要作适当的修正.修正参考焓值法Ⅰ和Ⅱ的预测结果明显优于经典参考焓值法;并且修正参考焓值法Ⅱ更加适用于高马赫数流动, 其壁面热流与DNS结果的相对误差在10%以内. 同时, 修正参考焓值法Ⅱ的普适性在超声速燃烧室隔离段热环境试验中得到了验证. 相似文献
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