Wall-Bounded Flows

Contributions of different scales of turbulent motions to the mean wall-shear stress in open channel flows at low-to-moderate Reynolds numbers

“…Gad-el-Hak 1994;Fan, Cheng & Li 2019a;Li et al 2019), but also exhibits close relevance to wall surface morphology (such as bed load transport in rivers, wind-blown sand movement in desert, etc.). Given the essential significance, sustained research efforts have been made to determine τ w (Winter 1979;Haritonidis 1989;Klewicki et al 2007;Walker 2014;Cierpka, Rossi & Köhler 2015;Rathakrishnan 2017;Vinuesa & Örlü 2017, etc. ) and to clarify its generation mechanism.…”

Untitled

“…where the von Karman constant 𝜅 and the constant 𝐵 are empirical constants [67][68][69]. For fixed 𝜅 and 𝐵 the value of the friction velocity 𝑢 𝜏 is related to a certain velocity profile 𝑦 ↦ → 𝑢(𝑦; 𝑢 𝜏 ) in the logarithmic boundary layer.…”

Use of vapochromic crystals to measure the concentration of a gaseous throughflow at the solid-fluid interface

“…Klewicki et al [15] present a useful review of OFI for measurement of surface shear stress in wallbounded flows. A thin film of oil applied to the surface of interest is illuminated by a monochromatic light source to produce fringe patterns (the result of constructive and destructive interference between the light partially reflected off the surface and the light that propagates through the film).…”

“…An array of factors affecting the accuracy of OFI are put forward by Klewicki et al [15], not all of which are relevant to this study. Those most pertinent to vapochromic crystals are surface contamination (analogous to thermal ageing and photodegredation of TLC and PSP respectively) and temperature.…”