航空学报 > 1987, Vol. 8 Issue (1): 20-28

对二维复杂湍流剪切流动数学模型的新探索

周明德   

  1. 南京航空学院
  • 收稿日期:1986-05-09 修回日期:1900-01-01 出版日期:1987-01-25 发布日期:1987-01-25

AN EXPLORATION TO THE MODELLING OF TWO-DIMENSIONAL COMPLEX TURBULENT SHEAR FLOWS

Zhou mingde   

  1. Nanjing Aeronautical Institute
  • Received:1986-05-09 Revised:1900-01-01 Online:1987-01-25 Published:1987-01-25

摘要: 在复杂湍流剪切流中经常会遇到雷诺剪应力与法向速度梯度的反号问题,此时涡粘性假设不再适用。Hinze从湍流结构中存在大涡的概念出发提出了包含台劳级数二阶项的剪应力表达式,取得了正确的定性结果。作者进一步分析了Hinze公式,认为他未能取得合理的定量结果的主要原因,在于他的公式隐含着假设流体微团在大涡的输送作用下能对原有的平均动量有足够的记忆。本文从实验与计算的比较以及近代对湍流结构的知识出发,提出了新的假设。认为较小尺度的湍流结构在大涡的输送作用下能对所包含的剪应力有足够的记忆,在此假设下,推出了新的湍流剪应力表达式,计算结果与实验数据的初步比较说明了此假设的合理性。

Abstract: The regions with shear stress and mean velocity gradient of opposite sign often exist in complex turbulent shear flows. In these cases, the eddy viscosity hypothesis break down. Hinze regarded the departure from eddy viscosity hypothesis as a result from transportation of mean momentum over distance by the large structures and arrived at a shear stress expression including the second order derivatives of the mean velocity. However, he gave correct results only qualitatively. The present author investigated the expression further and found it greatly over-estimated the shear stress. This means that the flow particles is unlikely to have enough memory of the mean momentum over distance. By assuming the departure from eddy viscosity hypothesis as a result from transportation of shear stress contained in smaller eddies over distance by the large structures, the present author arrived at a new shear stress expression The shear stress estimated so far were in good agreement with the experiment.