中文摘要：

采用大涡模拟方法研究了上下两层温度不同的稳定分层湍流，主要对其中的湍流尺度特性、统计特性和湍流输运特性，以及标量场的时空演化进行了分析研究．研究结果表明：浮力尺度沿流动方向先增加然后趋于某个稳定值，剪切越强，浮力尺度越大；翻转尺度沿流向也是逐渐增大，剪切越强，翻转尺度越大；统计特性的分析发现，在较大的区域内温度脉动的平坦因子都偏离Gauss分布，强分层条件下温度脉动的统计特性与速度脉动的统计特性有较明显差别；湍流混合的过程开始于小尺度运动，最后扩展到大尺度运动．

英文摘要：

Three dimensional large eddy simulation （LES） was performed in the investigation of stably stratified turbulence with a sharp thermal interface. Main results are focused on the turbulent characteristic scale, statistical properties, transport properties, and temporal and spatial evolution of the scalar field. Results show that the buoyancy scale increases first, and then goes to a certain constant value. The stronger the mean shear, the larger the buoyancy scale. The overturning scale increases with the flow, and the mean shear improves the overturning scale. The flatness factor of temperature departs from the Gaussian distribution in a fairly large region, and its statistical properties are clearly different from those of the velocity fluctuations in a strong stratified case. Turbulent mixing starts from small scale motions, and then extends to large scale motions.