射流中速度和温度的脉动关联及耗散规律

本文采用X热线-冷线组合探头及全速度偏航角标定法,对非等温圆形射流中的脉动关联量以及脉动量的耗散规律进行了实测和分析。得到了Reynolds应力、脉动热通量和Prandtl数的分布。对耗散率的测量结果证实了由满足自模条件导出的Taylor微尺度和湍动能耗散率在中心线上的变化关系是成立的,并且推导了中心线上湍流温度耗散率的表达式。本文的研究还表明,以往模拟计算中,将脉动温度场的时间尺度与脉动速度场的时间尺度之比取为常数的假定是缺乏实验依据的。

Fluctuating Correlation and Dissipative Law of Velocity and Temperature in Jet-Flow

The hot X-probe/cold wire arrangement was used for the measurement in a heated turbulent circular jet. The distributions of Reynolds shear stress, fluctuation heat flux and turbulent Prandtl number were obtained. The data of dissipation rates of turbulent kinetic energy and temperature confirmed the correlations, derived from requirements of self-preservation, for the streamwise variation of Taylor microscale and the average rate of dissipation of turbulent kinetic energy at the jet axis. An expression for the average rate of temperature dissipation at the jet axis was derived and is fairly well supported by the experimental result. The ratio between the time-scale of the thermal turbulent field and the time-scale of turbulent field, which is often assumed constant in turbulant modelling, was shown to decrease with increasing streamwise distance at the jet axis.