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Effect of Surface Irregulariries on Boundary-Layer Trarnsition on HLFC Wings Studied by AHLNS

Franco, Juan and Hein, Stefan (2021) Effect of Surface Irregulariries on Boundary-Layer Trarnsition on HLFC Wings Studied by AHLNS. Clean Sky 2 technology progress, 24.-25. März 2021, Madrid, Spain.

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Official URL: https://cleansky.eu/event/clean-sky-2-technology-progress-contribution-to-the-environmental-performance-of-the-next


The interest in Hybrid Laminar Flow Control (HLFC) wings lies in the potential of suction for reducing the viscous drag on commercial aircraft wings by delaying laminar-turbulent transition. However, the joint between the leading edge suction panel and the wing box may introduce surface irregularities (e.g. backward/forward-facing steps (BFS/FFS), gaps, etc.). Such surface irregularities can promote transition by enhancing the spatial development of flow instabilities (e.g. Tollmien-Schlichting (TS) waves or crossflow (CF) vortices) and, therefore, may reduce the potential benefit of the suction system. The presence of surface irregularities can cause regions of localized strong streamwise gradients in the base flow quantities. Standard methodologies for transition prediction like Parabolized Stability Equations (PSE) can still be applied in regions far from the surface irregularities, where the streamwise variations are small. However, the PSE formulation is not suited for handling the presence of such large streamwise gradients. The Adaptive Harmonic Linearized Navier-Stokes (AHLNS) equations on the other hand can handle these large streamwise gradients properly. Because AHLNS still takes advantage of the wave-like character of the boundary-layer instabilities by using the same wave approach as in PSE, it is able to reproduce the results from linear Direct Numerical Simulations (DNS) at orders of magnitude lower computational costs. The AHLNS approach has already been applied to study the effect of surface irregularities on laminar nacelles at flight Reynolds numbers relevant for transonic transport aircraft. Within the European project HLFC-WIN, part of the Clean Sky 2 Joint Undertaken, AHLNS is used to assess the detrimental effects of different surface irregularities immediately downstream of the suction panel of the transonic HLFC-WIN swept-wing configuration, thus contributing to the selection of a suitable joint design and the specification of the corresponding manufacturing tolerances. As an initial result, gap geometries considered do not significantly affect the expected laminar-turbulent transition location on the HLFC system. An overview of these on-going numerical studies will be given.

Item URL in elib:https://elib.dlr.de/141523/
Document Type:Conference or Workshop Item (Speech)
Title:Effect of Surface Irregulariries on Boundary-Layer Trarnsition on HLFC Wings Studied by AHLNS
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
Date:24 March 2021
Refereed publication:No
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:No
Keywords:AHLNS, Laminar-turbulent transition, surface irregularities, HLFC wings
Event Title:Clean Sky 2 technology progress
Event Location:Madrid, Spain
Event Type:international Conference
Event Dates:24.-25. März 2021
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 - Aircraft Technologies and Integration
Location: Göttingen
Institutes and Institutions:Institute for Aerodynamics and Flow Technology > High Speed Configurations, GO
Deposited By: Franco, Juan
Deposited On:18 May 2021 17:59
Last Modified:07 Apr 2022 16:59

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