Experimental study on turbulent asymptotic suction boundary layers

Abstract

Abstract

Laboratory realization of an asymptotic wall flow

“…In the turbulent case, precise parameter settings are also needed, with too much mass removal leading to downstream relaminarization and too little being insufficient to abate boundary layer growth. Ferro et al (2021) provide compelling evidence that their experiments attain the delicate balance required to create the TASBL state within a relatively short streamwise fetch and over a significant range of Reynolds numbers.…”

“…Unfortunately, attaining and accurately quantifying such idealized flow conditions in a laboratory experiment often proves to be a highly non-trivial, if not unattainable, objective. Given this, the results documented in the study by Ferro, Fallenius & Fransson (2021), relative to the turbulent asymptotic suction boundary layer (TASBL), constitutes an unusual and significant contribution.…”

“…In particular, these are x-invariant wall flows (statistically homogeneous in the TASBL case) that also have a constant velocity and irrotational free stream. Relative to the TASBL, Ferro et al (2021) identify a number of open questions that their experiments then convincingly address. Perhaps the most fundamental of these is whether the TASBL state can be attained in a reasonable laboratory experiment -an aim that, based upon their large eddy simulation results, Bobke, Orlu & Schlatter (2016) asserted was practically impossible.…”

“…Perhaps the most fundamental of these is whether the TASBL state can be attained in a reasonable laboratory experiment -an aim that, based upon their large eddy simulation results, Bobke, Orlu & Schlatter (2016) asserted was practically impossible. Similarly, Ferro et al (2021) describe that, owing to the paucity of data, the functional form and scaling behaviours associated with the mean velocity profile are not convincingly known -although a number of plausible proposals have been made regarding a logarithmic and/or bi-logarithmic region in addition to the profile in the viscous sublayer (e.g. Black & Sarnecki 1958;Tennekes 1964;Vigdorovich 2016).…”

Free-stream coherent structures in parallel compressible boundary-layer flows at subsonic and moderate supersonic Mach numbers

“…In the incompressible case, Hocking (1975) showed that the flow is linearly stable up to a Reynolds number of 54 370; Fransson & Alfredsson (2003) subsequently showed experimentally that transition could occur at much lower Reynolds numbers. It has been very recently shown that it is possible to experimentally realise a turbulent ASBL (Ferro, Fallenius & Fransson 2021). Several three-dimensional, fully nonlinear invariant solutions of the Navier–Stokes equations have been identified in incompressible ASBL flow.…”