A theory for the viscous sublayer of a turbulent flow
A theory for the viscous sublayer of a turbulent flow
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湍流粘性底层理论
DOI：
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发表时间：
1962
影响因子：
3.7
通讯作者：
J. Sternberg
中科院分区：
文献类型：
--
作者：
J. Sternberg
层流亚层和过渡区是湍流脉动直接被粘性耗散的区域。湍流脉动运动方程的简化线性化形式被用来描述壁面与完全湍流部分之间的湍流场。假定粘性下层内的平均流动和下层外的湍流场是从实验中得知的。小层厚度在理论上是自然产生的，直接类似于层流中涨落的内粘性区域。结果表明，包含大部分湍流能量的大尺度脉动向下游对流，其速度特性为边界层中部。因此，泰勒的假设不适用于壁面附近的这些大范围波动。湍流边界压力脉动测量得到的对流速度与理论相符。计算了子层的能谱和U‘涨落能级，并讨论了涨落场的其他方面。计算了下层边缘的线性压力脉动场，发现线性脉动场比非线性脉动场大得多。考察了强自由流湍流对层流边界层转变的影响，发现泰勒参数下的物理模型似乎是不正确的。
The laminar sublayer and ‘transition zone’ are shown to be the region where the turbulent velocity fluctuations are directly dissipated by viscosity. A simplified linearized from of the equations of motion for the turbulent fluctuations is used to describe the turbulent field between the wall and the fully turbulent part of the flow. The mean flow in the viscous sublayer and the turbulent field outside the sublayer are assumed to be known from experiment. The thickness of the sublayer arises naturally in the theory and is directly analogous to the inner viscous region for the fluctuations in a laminar flow. It is shown that the large-scale fluctuations containing most of the turbulent energy are convected downstream with a velocity characteristic of the middle of the boundary layer. Thus Taylor's hypothesis does not apply to these large-scale fluctuations near the wall. The convective velocity found in the measurements of pressure fluctuations at the boundaries of turbulent flows is in accord with the theory. Calculations are given for the energy spectra and u′ fluctuation level in the sublayer and other aspects of the fluctuation field are discussed. The linear pressure fluctuation field at the edge of the sublayer is calculated and found to be much larger than the nonlinear field. Examining the effect of strong free-stream turbulence on laminar boundary-layer transition, it appears that the physical model underlying Taylor's parameter is incorrect.