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Turbulent boundary layer over a bump with and without sweep
KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics. (FLOW)ORCID iD: 0000-0002-3814-7919
Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), 23955-6900 Thuwal, Kingdom of Saudi Arabia.ORCID iD: 0000-0002-2195-8408
Institute of Fluid Mechanics (LSTM), Friedrich–Alexander Universit¨at Erlangen–N¨urnberg (FAU), DE-910 58 Erlangen, Germany.ORCID iD: 0000-0001-9627-5903
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The development of a three-dimensional (3D) turbulent boundary layer over the Boeing speed bump is studied by infinitely sweeping the leading edge—thereby introducing a cross-flow component. While several numerical studies have looked at two-dimensional turbulent boundary layers over the bump, the current work corresponds closer to wings in practice, while retaining the simplicity of centerslice of the geometry. For validation, the unswept bump is also simulated, and time series data at different streamwise stations of cross-stream planes are usedto compute pre-multiplied spanwise spectra and linear coherence spectra. The linear coherence spectra revealed the potential influence of the wind tunnel topwall and/or a combination with minute inconsistencies in the inflow condition that can enhance the wall-normal coherence between the near-wall and outerregion of the boundary layer. The examination of pre-multiplied spectra shows the boundary layer development in a new light while hinting at the narrow width of the domain usually preferred for the Boeing bump simulations. Comparisons are then made between the swept and unswept configurations in terms of the development of the boundary layer and introduction of sweep causing the streamlines to curve. As seen in other experiments over swept surfaces, sweeping reduces the skin friction over the bump. The skin friction of the swept bump also did not show the second peak in skin friction observed for the unswept bump. In addition, the swept bump does not suffer incipient separation in the streamwise direction unlike the unswept bump.

National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-370677OAI: oai:DiVA.org:kth-370677DiVA, id: diva2:2002139
Note

QC 20251003

Available from: 2025-09-29 Created: 2025-09-29 Last updated: 2025-10-03Bibliographically approved
In thesis
1. Facilitating advanced spectral element simulations of wall-bounded flows
Open this publication in new window or tab >>Facilitating advanced spectral element simulations of wall-bounded flows
2025 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The overarching aim of this thesis is to enable accurate simulations of high-Reynolds-number wall-bounded flows, representative of those encountered in realistic engineering applications. Achieving this goal requires progress on several fronts, ranging from methodological developments to computational considerations and the application of simulations to relevant flow configurations.

First, advances are made in numerical techniques for scale-resolving simulations of wall-bounded turbulence. New methods are introduced that allow turbulent boundary layers to be simulated efficiently at arbitrarily high Reynolds numbers and sustained over long physical times. In addition, existing turbulence inflow generation approaches are assessed with particular emphasis on their suitability for aeroacoustic predictions, where a physically consistent representation of turbulent structures is essential.

Second, the ability of scale-resolving simulations to exploit emerging computing architectures is investigated. In particular, the sensitivity of such simulations to reduced-precision arithmetic, a feature increasingly common in modern high-performance computing hardware, is systematically evaluated. This provides insights into the accuracy–efficiency trade-offs that can be expected as computational platforms evolve.

Finally, the methods are applied to canonical but engineering-relevant test cases that combine fundamental physical interest with practical significance. Direct numerical simulations are carried out for flow over the Boeing speed bump and for a drone rotor at moderate Reynolds numbers. For the Boeing speed bump, a detailed analysis of boundary-layer dynamics is performed, providing new insights into the interaction between geometry-induced pressure gradients and turbulent structures. The drone rotor simulations, in turn, represent a first step toward applying scale-resolving methods to realistic aerodynamic configurations where both performance and noise are of interest.

Overall, the contributions of this thesis span algorithmic development, computational assessment, and application to canonical test cases, thereby laying the foundation for scale-resolving simulations of wall-bounded turbulence at conditions directly relevant to engineering design.

Abstract [sv]

Det övergripande målet med denna avhandling är att möjliggöra noggranna simuleringar av väggbundna strömmar vid höga Reynolds-tal, representativa för de förhållanden som återfinns i verkliga ingenjörstillämpningar. För att uppnådetta krävs framsteg på flera områden, från metodutveckling till datoranpassning och tillämpning på relevanta strömningsfall.

För det första presenteras nya numeriska metoder för skalanupplösande simuleringar av väggbunden turbulens. Dessa metoder gör det möjligt att på etteffektivt sätt simulera turbulenta gränsskikt vid godtyckligt höga Reynolds-tal och att upprätthålla simuleringarna under långa tidsperioder. Vidare utvärderas befintliga inflödesmetoder för turbulens med särskilt fokus på deras lämplighet för aeroakustiska prediktioner, där en fysiskt konsekvent representation av turbulenta strukturer är avgörande.

För det andra undersöks skalanupplösande simuleringars förmåga att utnyttjanya beräkningsarkitekturer. I synnerhet analyseras känsligheten hos dessasimuleringar för reducerad numerisk precision, en egenskap som blir allt vanligare i modern högprestandaberäkning. Detta ger viktiga insikter i av vägningen mellan noggrannhet och beräkningseffektivitet vid framtida beräkningsplattformar.

Slutligen tillämpas metoderna på kanoniska men ingenjörsrelevanta fall som kombinerar fundamentalt fysikaliskt intresse med praktisk betydelse. Direkta numeriska simuleringar genomförs för strömning över en Boeing speed bump samt för en drönarrotor vid måttliga Reynolds-tal. För Boeing speed bump analyseras gränsskiktets fysik i detalj, vilket ger nya insikter om samspelet mellan geometriinducerade tryckgradienter och turbulenta strukturer. Simuleringarnaav drönarrotorn utgör i sin tur ett första steg mot att tillämpa skalanupplösande metoder på realistiska aerodynamiska konfigurationer där både prestanda ochbuller är av intresse.

Sammanfattningsvis spänner avhandlingens bidrag från metodutveckling och datorarkitektoniska utvärderingar till tillämpning på kanoniska testfall. Därmed läggs en grund för skalanupplösande simuleringar av väggbunden turbulens under förhållanden som är direkt relevanta för ingenjörsmässig design.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2025. p. 215
Series
TRITA-SCI-FOU ; 2025:31
Keywords
Turbulence, Wall-bounded flows, Turbulent boundary layers, Inflow methods, Reduced precision, Aeroacoustics, Boeing speed bump, Drone rotors., Turbulens, Väggbundna strömmar, Turbulenta gränsskikt, Inflödesmetoder, Reducerad numerisk precision, Aeroakustik, Boeing speed bump, Drönarrotorer.
National Category
Fluid Mechanics
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-370680 (URN)978-91-8106-334-9 (ISBN)
Public defence
2025-10-23, F3, Lindstedtvägen 26, https://kth-se.zoom.us/j/67397349774, Stockholm, 10:15 (English)
Opponent
Supervisors
Note

QC 250930

Available from: 2025-09-30 Created: 2025-09-29 Last updated: 2025-10-07Bibliographically approved

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Stanly, RonithMukha, TimofeySchlatter, Philipp

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