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An Empirical Wall Law for the Mean Velocity in Adverse Pressure Gradients

Knopp, Tobias (2022) An Empirical Wall Law for the Mean Velocity in Adverse Pressure Gradients. DLR-Interner Bericht. DLR-IB-AS-GO-2022-105. DLR. 63 S.

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Abstract

An empirical wall law for the mean velocity in an adverse pressure gradient is presented, with the ultimate goal of aiming at the improvement of RANS turbulence models and wall functions. For this purpose a large database of turbulent boundary-layer flows in adverse pressure gradients from wind tunnel experiments is considered, and the mean velocity in the inner layer is analysed. The log law in the mean velocity is found to be a robust feature. The extent of the log-law region is reduced in ratio to the boundary layer thickness with increasing strength of the pressure gradient. An extended wall law emerges above the log law, extending up to the outer edge of the inner layer. An empirical correlation to describe the reduction of the log-law region is proposed, depending on the pressure-gradient parameter and on the Reynolds number in inner viscous scaling, whose functional form is motivated by similarity and scaling arguments. Finally, there is a discussion of the conjecture of the existence of a wall law for the mean velocity, which is governed mainly by local parameters and whose leading order effects are the pressure gradient and the Reynolds number, but whose details can be perturbed by higher-order local and history effects.

Item URL in elib:https://elib.dlr.de/189577/
Document Type:Monograph (DLR-Interner Bericht)
Title:An Empirical Wall Law for the Mean Velocity in Adverse Pressure Gradients
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Knopp, TobiasUNSPECIFIEDhttps://orcid.org/0000-0002-3161-5353UNSPECIFIED
Date:November 2022
Refereed publication:No
Open Access:Yes
Number of Pages:63
Status:Published
Keywords:turbulent boundary layer; law of the wall; log law; half-power law; adverse pressure gradient
Institution:DLR
Department:AS-CASE Göttingen
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:Efficient Vehicle
DLR - Research area:Aeronautics
DLR - Program:L EV - Efficient Vehicle
DLR - Research theme (Project):L - Digital Technologies
Location: Göttingen
Institutes and Institutions:Institute for Aerodynamics and Flow Technology > CASE, GO
Deposited By: Knopp, Dr.rer.nat. Tobias
Deposited On:23 Nov 2022 13:58
Last Modified:23 Nov 2022 13:58

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