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On the influence of two-dimensional hump roughness on laminar-turbulent transition

Franco, Juan and Hein, Stefan and Valero, Eusebio (2020) On the influence of two-dimensional hump roughness on laminar-turbulent transition. Physics of Fluids, 32 (3). American Institute of Physics (AIP). DOI: 10.1063/1.5131577 ISSN 1070-6631

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Official URL: https://doi.org/10.1063/1.5131577

Abstract

The presence of large surface irregularities such as humps, where the height is similar to the local boundary-layer (BL) displacement thickness, introduces regions of localized strong streamwise gradients in the base flow quantities. These large gradients can significantly modify the spatial development of incoming disturbances that lead to laminar–turbulent transition in wall-bounded flows [e.g., Tollmien–Schlichting (TS) waves]. Techniques such as Parabolized Stability Equations (PSE) are not suited for BL instability analysis in such regions: their formulation assumes that streamwise variations of base flow and disturbance quantities are small, allowing a marching procedure for their resolution. On the other hand, the Adaptive Harmonic Linearized Navier–Stokes (AHLNS) equations can handle these large streamwise gradients by using a fully elliptic system of equations, similar to Linearized Navier–Stokes (LNS), Harmonic LNS (HLNS), or Direct Numerical Simulation (DNS). Moreover, in AHLNS (as in PSE), a wave-like character of the instabilities is assumed, leading to a significant reduction in the number of streamwise grid points required compared with LNS, HLNS, or DNS computations. In the present study, an efficient combination of PSE and AHLNS is used to investigate the effect of height, length, and shape of a single hump placed on a flat plate in a two-dimensional flow field at Ma=0.5 without pressure gradient. The effect of this hump on the spatial evolution of TS waves, in terms of N-factors, is presented. An expected laminar–turbulent transition onset, via the eN methodology, is also described. It is shown that the shape of the surface irregularity, together with the height and length, plays an important role for the location of laminar–turbulent transition onset in convectively unstable flows.

Item URL in elib:https://elib.dlr.de/129611/
Document Type:Article
Title:On the influence of two-dimensional hump roughness on laminar-turbulent transition
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Franco, JuanJuan.Franco (at) dlr.dehttps://orcid.org/0000-0002-8391-8356
Hein, StefanStefan.Hein (at) dlr.deUNSPECIFIED
Valero, EusebioUniversidad Politécnica de MadridUNSPECIFIED
Date:2 March 2020
Journal or Publication Title:Physics of Fluids
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:32
DOI :10.1063/1.5131577
Editors:
EditorsEmailEditor's ORCID iD
UNSPECIFIEDAIPUNSPECIFIED
Publisher:American Institute of Physics (AIP)
ISSN:1070-6631
Status:Published
Keywords:boundary layers : stability, boundary layers : separation, instabilities : transition to turbulence, instabilities : boundary layer , laminar flows : boundary layers
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:other
DLR - Research area:Aeronautics
DLR - Program:L - no assignment
DLR - Research theme (Project):L - Managementaufgaben Luftfahrt
Location: Göttingen
Institutes and Institutions:Institute for Aerodynamics and Flow Technology > High Speed Configurations, GO
Deposited By: Franco, Juan
Deposited On:17 Mar 2020 17:52
Last Modified:17 Mar 2020 17:52

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