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arXiv · 2505.18718

Reconsiderations about inner layer of wall-bounded flows

Hassan Nagib
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Abstract

Following recent evidence that even ZPG boundary layers do not exhibit a purely logarithmic extended overlap region, reconsideration of recently advanced logarithmic plus linear extended overlap region in wall-bounded flows leads to a revision of the model for the extended overlap region. The significant difference between the two representations is a separation between the inner layer and the extended overlap layer in the coefficient of the logarithmic term into $\kappa_{in}$ and k_o, respectively. From a wide range of data examined in wall-bounded flows, the value of k_in is universal and equal to 1/2.6 or in the range 0.38 400 and Y_out~0.45. This appears to be counterintuitive and deserves further attention. Here, both models are reevaluated using the same data sets from recent investigations in a region closer to the wall but outside the region with viscous stresses exceeding 20% of the total stress; i.e., dominated by viscous effects. It is perplexing that both an inviscid and a viscous model agree equally well with experiments and DNS data in this region closer to the wall.

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Hassan Nagib. 2025-05-24. Reconsiderations about inner layer of wall-bounded flows. https://arxiv.org/abs/2505.18718

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