层流脉动流中平行圆柱体的温度边界层

Thermal boundary layer of parallel cylinder in laminar pulsating flows

采用数值模拟方法研究了一个平行圆柱体在层流脉动流中的温度边界层特性。数值模拟结果与实验数据一致。研究发现脉动流中平行圆柱体形成了形状不规则但相对稳定的温度边界层,并在流动方向上周期性脉动。脉动流中平行圆柱体的温度边界层平均厚度小于稳定流动下的温度边界层平均厚度,并以脉动流的频率进行脉动。此外,脉动流中平行圆柱体的壁面温度小于稳定流动下的壁面温度,表明脉动流下圆柱体的对流传热得到了强化。在一个脉动周期内,圆柱体在后半周期的温度边界层厚度和热阻均小于前半周期的温度边界层厚度和热阻。

The characteristics of thermal boundary layer of a parallel cylinder in laminar pulsating flows were numerically studied. Numerical results agree well with the experimental data. A relatively stable thermal boundary layer but with irregular shapes is observed for a parallel cylinder in pulsating flows, oscillating in the flowing direction. The averaged thickness of thermal boundary layer is found to be less than that in the steady flows, which also oscillates under the same frequency as the pulsating flows. On the other hand, the wall temperature of the cylinder is found to be lower in the pulsating flows than that in the steady flows, indicating that an enhanced convection heat transfer is obtained. During one pulsating cycle, the thickness of thermal boundary layer and the heat resistance are found to be smaller in the second half period than in the first half period.