kth.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Direct numerical simulation of the turbulent flow around a Flettner rotor
KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics, Turbulent simulations laboratory. (SimEx/Flow)ORCID iD: 0000-0002-6712-8944
KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Computational Science and Technology (CST).ORCID iD: 0000-0003-3374-8093
KTH, School of Electrical Engineering and Computer Science (EECS), Centres, Centre for High Performance Computing, PDC.ORCID iD: 0000-0002-5020-1631
KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Computational Science and Technology (CST).ORCID iD: 0000-0003-0639-0639
Show others and affiliations
2024 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 14, no 1, article id 3004Article in journal (Refereed) Published
Abstract [en]

The three-dimensional turbulent flow around a Flettner rotor, i.e. an engine-driven rotating cylinder in an atmospheric boundary layer, is studied via direct numerical simulations (DNS) for three different rotation speeds (α). This technology offers a sustainable alternative mainly for marine propulsion, underscoring the critical importance of comprehending the characteristics of such flow. In this study, we evaluate the aerodynamic loads produced by the rotor of height h, with a specific focus on the changes in lift and drag force along the vertical axis of the cylinder. Correspondingly, we observe that vortex shedding is inhibited at the highest α values investigated. However, in the case of intermediate α, vortices continue to be shed in the upper section of the cylinder (y/h>0.3). As the cylinder begins to rotate, a large-scale motion becomes apparent on the high-pressure side, close to the bottom wall. We offer both a qualitative and quantitative description of this motion, outlining its impact on the wake deflection. This finding is significant as it influences the rotor wake to an extent of approximately one hundred diameters downstream. In practical applications, this phenomenon could influence the performance of subsequent boats and have an impact on the cylinder drag, affecting its fuel consumption. This fundamental study, which investigates a limited yet significant (for DNS) Reynolds number and explores various spinning ratios, provides valuable insights into the complex flow around a Flettner rotor. The simulations were performed using a modern GPU-based spectral element method, leveraging the power of modern supercomputers towards fundamental engineering problems.

Place, publisher, year, edition, pages
Springer Nature , 2024. Vol. 14, no 1, article id 3004
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-344051DOI: 10.1038/s41598-024-53194-xScopus ID: 2-s2.0-85184207516OAI: oai:DiVA.org:kth-344051DiVA, id: diva2:1841616
Funder
KTH Royal Institute of TechnologyKTH Royal Institute of Technology
Note

QC 20240301

Available from: 2024-02-29 Created: 2024-02-29 Last updated: 2024-04-22Bibliographically approved
In thesis
1. Space-adaptive simulation of transition and turbulence in shear flows
Open this publication in new window or tab >>Space-adaptive simulation of transition and turbulence in shear flows
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Rymdadaptiv simulering av transition och turbulens i skjuvströmning
Abstract [en]

Transitional and turbulent shear flows are ubiquitous, from the boundary layer developing on an aeroplane wing to the flow within the aortic arch. In this thesis, we study wall-bounded and free shear flows through direct numerical simulations. To control numerical errors and represent every flow structure, we implement the adaptive mesh refinement (AMR) technique within a spectral element method code. Using data-driven methods and causality metrics, we explore the fundamental physical mechanisms in various shear flows.

The adaptive mesh refinement technique necessitates a precise evaluation of the committed error. Thus, we compare the local spectral error indicator with the dual-weighted adjoint error estimator. The former ensures a more homogeneous refinement, targeting regions with a high-velocity gradient, while the latter is goal-oriented. However, the adjoint error estimator fails in turbulent flows due to the exponential sensitivity of the adjoint linear solution to any perturbation. Alternatively, we introduce a causality-based error indicator that employs the Shannon transfer entropy, i.e. a causality metric arising from information theory, to establish causal relations between the local solution and a specified quantity of interest.

Using information-theoretic causality, linear global stability analysis and modal decomposition, we investigate transitional and turbulent coherent structures. In turbulent straight pipe flows, the proper orthogonal decomposition is integrated with the Voronoi diagram to automatically discern between wall-attached and detached eddies. In spatially developing bent pipe flows, we employ the proper orthogonal decomposition to examine the swirl switching phenomenon, the origins of which continue to be a topic of debate. In the context of external flows around a cylinder, we explore two configurations: the Flettner rotor, a rotating cylinder in a wall-bounded shear flow, and the stepped cylinder, namely two cylinders of different diameters joined at one extremity. In the first configuration, we analyse the large-scale motion at the base of the rotor and the local vortex shedding suppression. In the second, we provide an in-depth look at structures arising on the junction surface and in the wake. Additionally, we conduct a global stability analysis with a novel AMR-based approach for some of the aforementioned cases.

Abstract [sv]

I denna avhandling studerar vi transitionella och turbulenta skjuvströmningar genom direkta numeriska simuleringar. Med hänsyn till den avgörande rollen av att kontrollera numeriska fel och representera varje skala i rummet, utvecklar, validerar och implementerar vi den adaptiva nätförfiningstekniken inom en spektralelementkod. Med hjälp av data-drivna metoder och mått för kausalitet utforskar vi de grundläggande fysikaliska mekanismerna i olika skjuvströmningar.

Den adaptiva nätförfiningen kräver en noggrann beräkning av det begångna felet. Således jämför vi den lokala spektrala felindikatorn med den felestimatorn från adjunkt-ekvationen. Den förra säkerställer en mer homogen förfining, inriktad på områden med en stor hastighetsgradient, medan den senare är målinriktad. Emellertid misslyckas den adjunkta felestimatorn i turbulenta flöden på grund av den exponentiella känsligheten hos den adjunkta linjära lösningen för turbulenta störningar. Som nytt alternativ introducerar vi en kausalitets-baserad felindikator som använder Shannon-transferentropin, dvs. ett kausalitets-mått som härrör från informationsteori, för att fastställa kausala samband mellan den lokala lösningen och en specificerad kvantitet av intresse.

Med hjälp av detta kausalitets-mått, linjär global stabilitetsanalys och modal dekomposition undersöker vi transitionella och turbulenta koherenta strukturer. I glatta turbulenta rörströmningar använder vi den så kallade proper orthogonal decomposition (POD) med Voronoi-diagrammet för att automatiskt skilja mellan väggnära och yttre virvlar. För strömningsfallet med ett krökt rör med 90 eller 180 grader-vinkel använder vi POD för att undersöka fenomenet swirl switching, vars ursprung fortsatt är oklart i litteraturen. I samband med den externa strömningen runt en cylinder utforskar vi två konfigurationer: Flettner-rotorn, en roterande cylinder i ett gränsskikt och den stegformade cylindern, där två cylindrar med olika diametrar är sammanfogade i ena änden. I den första konfigurationen analyserar vi den storskaliga rörelsen vid rotorns bas och den lokala förändringen av virvelamplituden. I den andra ger vi en djupgående analys av strukturer som uppstår nära mitten och i vaken. Dessutom genomför vi en global stabilitetsanalys med en ny adaptiv metod för att förstå bättre fysiken av de tidigare nämnda fallen.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2024
Series
TRITA-SCI-FOU ; 2024:10
Keywords
Turbulence, global stability, coherent structures, adaptive mesh refinement, Turbulens, global stabilitet, koherenta strukturer, adaptiv nätförfining
National Category
Fluid Mechanics and Acoustics
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-344052 (URN)978-91-8040-844-8 (ISBN)
Public defence
2024-03-27, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 240304

Available from: 2024-03-04 Created: 2024-02-29 Last updated: 2024-03-06Bibliographically approved
2. Direct Numerical Simulation of Turbulence on Heterogenous Computer Systems: Architectures, Algorithms, and Applications
Open this publication in new window or tab >>Direct Numerical Simulation of Turbulence on Heterogenous Computer Systems: Architectures, Algorithms, and Applications
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Direct numerical simulations (DNS) of turbulence have a virtually unbounded need for computing power. To carry out these simulations, software, computer architectures, and algorithms must operate as efficiently as possible to amortize the large computational cost. However, in a computing landscape increasingly incorporating heterogeneous computer systems, changes are necessary. In this thesis, we consider how DNS can be carried out efficiently on upcoming heterogeneous computer systems. This work relates to developing algorithms for upcoming heterogeneous computer architectures, overcoming software challenges associated with large-scale DNS on these platforms, and applying these developments to new flow cases that were previously too costly to carry out. We consider in particular the spectral element method for DNS and evaluate how this method maps to field-programmable gate arrays, graphics processing units, as well as conventional processors. We also consider the issue of trading arithmetic operations for less communication, reducing the cost of solving the linear systems that arise in the spectral element method. Our developments are incorporated into the spectral element framework Neko, enabling Neko to strong-scale efficiently on the largest supercomputers in the world. Finally, we have carried out several DNS such as the simulation of a Flettner rotor in a turbulent boundary layer and simulating Rayleigh-Bénard convection at very high Rayleigh numbers. The developments in this thesis enable the high-fidelity simulation of turbulence on emerging computer systems with high parallel efficiency and performance.

Abstract [sv]

Direct numerisk simulering (DNS) av turbulens kräver enorma mängder datorkraft. För att utföra simuleringar som DNS krävs det att mjukvara, datorarkitekturer och algoritmer samverkar så effektivt som möjligt tillsammans. Idag förändras superdatorer snabbt och inkoporerar nya heterogena datorarkitekturer. Detta innebär att nya tillvägagångssätt är nödvändiga för att tillgodogöra sig all beräkningskraft. I den här avhandlingen fokuserar vi på DNS på heterogena, storskaliga, datorsystem för att möjligöra nya simuleringar av turbulenta flöden. För att nå detta mål undersöker vi nya datorarkitekturer, analyserar och förbättrar de numeriska metoderna och algoritmerna vi använder och applicerar slutligen våra utvecklingar på nya simuleringar av turbulens. Vi fokuserar speciellt på den spektrala element metoden (SEM) för DNS och undersöker hur den beter sig på eng. field-programmable gate arrays, grafikkort och konventionella processorer. Vi bidrar även med analys av hur vi löser det linjära systemet som utgör kärnan i SEM för att bättre utnyttja den tillgängliga datorkraften och minska mängden data som behöver överföras. Våra förbättringar inkorporeras i SEM lösaren Neko och möjligör att Neko kan skala effektivt på de största superdatorerna i världen. Vi använder sedan detta ramverk för att genomföra flera storskaliga simuleringar. Vi genomför den första simuleringen av en Flettner rotor och dess interaktion med turbulent skjuvströmning samt simulering av Rayleigh-Bénard konvektion i en cylindrisk domän vid mycket höga Rayleigh tal. Avhandlingen möjligör detaljerad numerisk simulering av turbulens med hög skalbarhet och prestanda i dagens föränderliga datorlandskap. 

Place, publisher, year, edition, pages
Stockholm, Sweden: KTH Royal Institute of Technology, 2024. p. 54
Series
TRITA-EECS-AVL ; 2024:36
Keywords
High Performance Computing, Turbulence, Computational Fluid Dynamics, Heterogenous Computer Architectures, Högprestandaberäkningar, Turbulens, Numerisk Strömingsmekanik, Heterogena Datorarkitekturer
National Category
Computer Sciences Fluid Mechanics and Acoustics
Research subject
Computer Science
Identifiers
urn:nbn:se:kth:diva-345851 (URN)978-91-8040-910-0 (ISBN)
Public defence
2024-05-24, https://kth-se.zoom.us/s/61541415709, Kollegiesalen, Brinellvägen 6, Stockholm, 09:15 (English)
Opponent
Supervisors
Funder
Swedish e‐Science Research Center, SESSI
Note

QC 20240423

Available from: 2024-04-23 Created: 2024-04-22 Last updated: 2024-05-15Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full textScopus

Authority records

Massaro, DanieleKarp, MartinJansson, NiclasMarkidis, StefanoSchlatter, Philipp

Search in DiVA

By author/editor
Massaro, DanieleKarp, MartinJansson, NiclasMarkidis, StefanoSchlatter, Philipp
By organisation
Turbulent simulations laboratoryComputational Science and Technology (CST)Centre for High Performance Computing, PDCFluid Mechanics and Engineering Acoustics
In the same journal
Scientific Reports
Fluid Mechanics and Acoustics

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 85 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf