Effect of free-stream turbulence on boundary layer transition
Effect of free-stream turbulence on boundary layer transition
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DOI：
10.1098/rsta.2013.0354
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发表时间：
2014-07
期刊：
影响因子：
--
通讯作者：
M. Goldstein
中科院分区：
文献类型：
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作者：
M. Goldstein
本文研究由中等高度的自由流紊流引起的平板边界层向紊流的转变。湍流被假定为产生的（理想化）网格和匹配的渐近展开被用来分析位于下游区域的有限厚度的平板上产生的流。基于网格尺寸λ和自由流速度的特征雷诺数Rλ被假定为大，湍流强度λ被假定为小。本文讨论了湍流雷诺数<$Rλ和板厚和在极限为和<$→0时保持固定（分别为O（1）和O（λ））的一般情况下的渐近流动结构。但考虑各种限制情况，以解释相关的过渡机制。有人认为，有两种类型的条纹状结构，可以在过渡过程中发挥作用：（i）那些出现在下游区域，并在上游流的流向涡产生的和（ii）那些集中在前缘附近，并在上游流的板法向涡产生的。前者相对不受前缘几何形状的影响，通常称为Klebanoff模式，而后者受前缘几何形状的影响很大，外观上更像流向涡。
This paper is concerned with the transition to turbulence in flat plate boundary layers due to moderately high levels of free-stream turbulence. The turbulence is assumed to be generated by an (idealized) grid and matched asymptotic expansions are used to analyse the resulting flow over a finite thickness flat plate located in the downstream region. The characteristic Reynolds number Rλ based on the mesh size λ and free-stream velocity is assumed to be large, and the turbulence intensity ϵ is assumed to be small. The asymptotic flow structure is discussed for the generic case where the turbulence Reynolds number ϵRλ and the plate thickness and are held fixed (at O(1) and O(λ), respectively) in the limit as and ϵ→0. But various limiting cases are considered in order to explain the relevant transition mechanisms. It is argued that there are two types of streak-like structures that can play a role in the transition process: (i) those that appear in the downstream region and are generated by streamwise vorticity in upstream flow and (ii) those that are concentrated near the leading edge and are generated by plate normal vorticity in upstream flow. The former are relatively unaffected by leading edge geometry and are usually referred to as Klebanoff modes while the latter are strongly affected by leading edge geometry and are more streamwise vortex-like in appearance.