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Mukha, T., Brethouwer, G. & Schlatter, P. (2024). Boundary Conditions for Wall-Modelled Large-Eddy Simulation Using Spectral Element Discretization. In: ERCOFTAC Series: (pp. 215-220). Springer Science and Business Media B.V., 31
Open this publication in new window or tab >>Boundary Conditions for Wall-Modelled Large-Eddy Simulation Using Spectral Element Discretization
2024 (English)In: ERCOFTAC Series, Springer Science and Business Media B.V. , 2024, Vol. 31, p. 215-220Chapter in book (Other academic)
Abstract [en]

Complementing large-eddy simulation (LES) with wall-modelling is, perhaps, the most straight-forward way to enable high-fidelity simulations at high Reynolds numbers. At the same time, high-order methods offer the benefits of high computational efficiency and potentially faster convergence with respect to mesh refinement even outside the asymptotic regime.

Place, publisher, year, edition, pages
Springer Science and Business Media B.V., 2024
National Category
Computational Mathematics Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-340784 (URN)10.1007/978-3-031-47028-8_33 (DOI)2-s2.0-85178120212 (Scopus ID)
Note

QC 20231214

Available from: 2023-12-14 Created: 2023-12-14 Last updated: 2023-12-14Bibliographically approved
Massaro, D., Karp, M., Jansson, N., Markidis, S. & Schlatter, P. (2024). Direct numerical simulation of the turbulent flow around a Flettner rotor. Scientific Reports, 14(1), Article ID 3004.
Open this publication in new window or tab >>Direct numerical simulation of the turbulent flow around a Flettner rotor
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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
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-344051 (URN)10.1038/s41598-024-53194-x (DOI)2-s2.0-85184207516 (Scopus ID)
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
Lupi, V., Örlü, R. & Schlatter, P. (2024). Direct Numerical Simulations of Turbulent Flow in Helical Pipes. In: ERCOFTAC Series: (pp. 362-367). Springer Science and Business Media B.V., 31
Open this publication in new window or tab >>Direct Numerical Simulations of Turbulent Flow in Helical Pipes
2024 (English)In: ERCOFTAC Series, Springer Science and Business Media B.V. , 2024, Vol. 31, p. 362-367Chapter in book (Other academic)
Abstract [en]

Direct numerical simulations of the fully developed turbulent flow through helical pipes are performed. The numerical procedure is described, and a validation of the volume force driving the flow is presented. A comparison of the turbulence statistics against literature data is also reported.

Place, publisher, year, edition, pages
Springer Science and Business Media B.V., 2024
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-340778 (URN)10.1007/978-3-031-47028-8_55 (DOI)2-s2.0-85178107205 (Scopus ID)
Note

QC 20231214

Available from: 2023-12-14 Created: 2023-12-14 Last updated: 2023-12-14Bibliographically approved
Mallor, F., Liu, J., Peplinski, A., Vinuesa, R., Örlü, R., Weinkauf, T. & Schlatter, P. (2024). In-Situ Analysis of Backflow Events and Their Relation to Separation in Wings Through Well-Resolved LES. In: ERCOFTAC Series: (pp. 17-22). Springer Science and Business Media B.V., 31
Open this publication in new window or tab >>In-Situ Analysis of Backflow Events and Their Relation to Separation in Wings Through Well-Resolved LES
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2024 (English)In: ERCOFTAC Series, Springer Science and Business Media B.V. , 2024, Vol. 31, p. 17-22Chapter in book (Other academic)
Abstract [en]

Wall-bounded turbulent flows as those occurring in transportation (e.g. aviation) or industrial applications (e.g turbomachinery), are usually subjected to pressure gradients (PGs). The presence of such PGs affects greatly the development and physics of the turbulent boundary layer (TBL), making it an open research area. An important phenomena associated with the presence of strong adverse PGs (APGs) as appearing in wings, is the separation of the boundary layer, which can lead to stall.

Place, publisher, year, edition, pages
Springer Science and Business Media B.V., 2024
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-340780 (URN)10.1007/978-3-031-47028-8_3 (DOI)2-s2.0-85178156992 (Scopus ID)
Note

QC 20231214

Available from: 2023-12-14 Created: 2023-12-14 Last updated: 2023-12-14Bibliographically approved
Massaro, D., Yao, J., Rezaeiravesh, S., Hussain, F. & Schlatter, P. (2024). Karhunen-Loève decomposition of high Reynolds number turbulent pipe flows: a Voronoi analysis. Paper presented at 5th Madrid Turbulence Workshop.
Open this publication in new window or tab >>Karhunen-Loève decomposition of high Reynolds number turbulent pipe flows: a Voronoi analysis
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2024 (English)Manuscript (preprint) (Other academic)
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-344045 (URN)
Conference
5th Madrid Turbulence Workshop
Note

Fifth Madrid Turbulence Workshop May 29 - June 30, 2023

Will be published in Journal of Physics: Conference Series (In Press)

QC 20240304

Available from: 2024-02-29 Created: 2024-02-29 Last updated: 2024-03-04Bibliographically approved
Jansson, N., Karp, M., Podobas, A., Markidis, S. & Schlatter, P. (2024). Neko: A modern, portable, and scalable framework for high-fidelity computational fluid dynamics. Computers & Fluids, 275, 106243-106243, Article ID 106243.
Open this publication in new window or tab >>Neko: A modern, portable, and scalable framework for high-fidelity computational fluid dynamics
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2024 (English)In: Computers & Fluids, ISSN 0045-7930, E-ISSN 1879-0747, Vol. 275, p. 106243-106243, article id 106243Article in journal (Refereed) Published
Abstract [en]

Computational fluid dynamics (CFD), in particular applied to turbulent flows, is a research area with great engineering and fundamental physical interest. However, already at moderately high Reynolds numbers the computational cost becomes prohibitive as the range of active spatial and temporal scales is quickly widening. Specifically scale-resolving simulations, including large-eddy simulation (LES) and direct numerical simulations (DNS), thus need to rely on modern efficient numerical methods and corresponding software implementations. Recent trends and advancements, including more diverse and heterogeneous hardware in High-Performance Computing (HPC), are challenging software developers in their pursuit for good performance and numerical stability. The well-known maxim “software outlives hardware” may no longer necessarily hold true, and developers are today forced to re-factor their codebases to leverage these powerful new systems. In this paper, we present Neko, a new portable framework for high-order spectral element discretization, targeting turbulent flows in moderately complex geometries. Neko is fully available as open software. Unlike prior works, Neko adopts a modern object-oriented approach in Fortran 2008, allowing multi-tier abstractions of the solver stack and facilitating hardware backends ranging from general-purpose processors (CPUs) down to exotic vector processors and FPGAs. We show that Neko’s performance and accuracy are comparable to NekRS, and thus on-par with Nek5000’s successor on modern CPU machines. Furthermore, we develop a performance model, which we use to discuss challenges and opportunities for high-order solvers on emerging hardware

Place, publisher, year, edition, pages
Elsevier BV, 2024
National Category
Fluid Mechanics and Acoustics Computational Mathematics Computer Sciences
Identifiers
urn:nbn:se:kth:diva-344896 (URN)10.1016/j.compfluid.2024.106243 (DOI)2-s2.0-85189508362 (Scopus ID)
Funder
Swedish Research Council, 2019-04723EU, Horizon 2020, 823691EU, Horizon 2020, 801039
Note

QC 20240403

Available from: 2024-04-02 Created: 2024-04-02 Last updated: 2024-04-22Bibliographically approved
Toosi, S., Peplinski, A., Schlatter, P. & Vinuesa, R. (2024). The Effect of Wing-Tip Vortices on the Flow Around a NACA0012 Wing. In: ERCOFTAC Series: (pp. 183-188). Springer Science and Business Media B.V., 31
Open this publication in new window or tab >>The Effect of Wing-Tip Vortices on the Flow Around a NACA0012 Wing
2024 (English)In: ERCOFTAC Series, Springer Science and Business Media B.V. , 2024, Vol. 31, p. 183-188Chapter in book (Other academic)
Abstract [en]

The wing-tip vortices are formed near the tip of finite-span, lift-generating surfaces as a result of the pressure difference between the pressure and suction sides of the wing.

Place, publisher, year, edition, pages
Springer Science and Business Media B.V., 2024
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-340785 (URN)10.1007/978-3-031-47028-8_28 (DOI)2-s2.0-85178092210 (Scopus ID)
Note

QC 20231214

Available from: 2023-12-14 Created: 2023-12-14 Last updated: 2023-12-14Bibliographically approved
Atzori, M., Mallor, F., Pozuelo, R., Fukagata, K., Vinuesa, R. & Schlatter, P. (2023). A new perspective on skin-friction contributions in adverse-pressure-gradient turbulent boundary layers. International Journal of Heat and Fluid Flow, 101, Article ID 109117.
Open this publication in new window or tab >>A new perspective on skin-friction contributions in adverse-pressure-gradient turbulent boundary layers
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2023 (English)In: International Journal of Heat and Fluid Flow, ISSN 0142-727X, E-ISSN 1879-2278, Vol. 101, article id 109117Article in journal (Refereed) Published
Abstract [en]

For adverse-pressure-gradient turbulent boundary layers, the study of integral skin-friction contributions still poses significant challenges. Beyond questions related to the integration boundaries and the derivation procedure, which have been thoroughly investigated in the literature, an important issue is how different terms should be aggregated. The nature of these flows, which exhibit significant in-homogeneity in the streamwise direction, usually results in cancellation between several contributions with high absolute values. We propose a formulation of the identity derived by Fukagata et al. (2002), which we obtained from the convective form of the governing equations. A new skin-friction contribution is defined, considering wall-tangential convection and pressure gradient together. This contribution is related to the evolution of the dynamic pressure in the mean flow. The results of the decomposition are examined for a broad range of pressure-gradient conditions and different flow-control strategies. We found that the new formulation of the identity allows to readily identify the different regimes of near-equilibrium conditions and approaching separation. It also provides a more effective description of control effects. A similar aggregation between convection and pressure-gradient terms is also possible for any other decomposition where in-homogeneity contributions are considered explicitly.

Place, publisher, year, edition, pages
Elsevier BV, 2023
Keywords
Turbulent boundary layers, Adverse pressure gradients, Skin friction
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-326056 (URN)10.1016/j.ijheatfluidflow.2023.109117 (DOI)000952242400001 ()2-s2.0-85149273522 (Scopus ID)
Note

QC 20230425

Available from: 2023-04-25 Created: 2023-04-25 Last updated: 2024-01-19Bibliographically approved
Mallor, F., Frede, A., Rezaeiravesh, S., Gatti, D. & Schlatter, P. (2023). Bayesian Optimisation of blowing and suction for drag reduction on a transonic airfoil. In: Proceedings of the 14th ERCOFTAC Symp. on Engineering Turbulence Modelling and Measurements (ETMM14), Barcelona, Spain: . Paper presented at ERCOFTAC symposium on Engineering, Turbulence, Modelling and Measurements (ETMM14), Barcelona, Spain, 6-8 September 2023 (pp. 837-842).
Open this publication in new window or tab >>Bayesian Optimisation of blowing and suction for drag reduction on a transonic airfoil
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2023 (English)In: Proceedings of the 14th ERCOFTAC Symp. on Engineering Turbulence Modelling and Measurements (ETMM14), Barcelona, Spain, 2023, p. 837-842Conference paper, Oral presentation with published abstract (Other academic)
Abstract [en]

Wall-normal blowing and suction has shown to be a promising active control method for friction drag reduction. In this work, we exploit a Bayesian optimization framework based on Gaussian process regression to find a configuration of non-homogeneous wall-normal blowing and suction capable of improving the aerodynamic efficiency of an RAE2822 airfoil in transonic conditions. The RANS simulations are carried out with the open-source solver SU2. During the optimization process, three different scenarios are considered: only the drag is minimized, the drag and the power needed to drive the control system are included, and the actuation power with a specified compressor efficiency are used for the calculation of the efficiency increase. Even in the most realistic case considering the actuation power and efficiencies an increase in the overall efficiency of 1.15% is reached.

National Category
Fluid Mechanics and Acoustics
Research subject
Aerospace Engineering; Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-342440 (URN)
Conference
ERCOFTAC symposium on Engineering, Turbulence, Modelling and Measurements (ETMM14), Barcelona, Spain, 6-8 September 2023
Note

QC 20240122

Available from: 2024-01-19 Created: 2024-01-19 Last updated: 2024-01-22Bibliographically approved
Mallor, F., Semprini-Cesari, G., Mukha, T., Rezaeiravesh, S. & Schlatter, P. (2023). Bayesian Optimization of Wall-Normal Blowing and Suction-Based Flow Control of a NACA 4412 Wing Profile. Flow Turbulence and Combustion
Open this publication in new window or tab >>Bayesian Optimization of Wall-Normal Blowing and Suction-Based Flow Control of a NACA 4412 Wing Profile
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2023 (English)In: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987Article in journal (Refereed) Published
Abstract [en]

Active flow-control techniques have shown promise for achieving high levels of drag reduction. However, these techniques are often complex and involve multiple tunable parameters, making it challenging to optimize their efficiency. Here, we present a Bayesian optimization (BO) approach based on Gaussian process regression to optimize a wall-normal blowing and suction control scheme for a NACA 4412 wing profile at two angles of attack: 5 and 11∘, corresponding to cruise and high-lift scenarios, respectively. An automated framework is developed by linking the BO code to the CFD solver OpenFOAM. RANS simulations (validated against high-fidelity LES and experimental data) are used in order to evaluate the different flow cases. BO is shown to provide rapid convergence towards a global maximum, even when the complexity of the response function is increased by introducing a model for the cost of the flow control actuation. The importance of considering the actuation cost is highlighted: while some cases yield a net drag reduction (NDR), they may result in an overall power increase. Furthermore, optimizing for NDR or net power reduction (NPR) can lead to significantly different actuation strategies. Finally, by considering losses and efficiencies representative of real-world applications, still a significant NPR is achieved in the 11∘ case, while net power reduction is only marginally positive in the 5∘ case.

Place, publisher, year, edition, pages
Springer Nature, 2023
Keywords
Flow control, Bayesian optimization, Gaussian process regression, drag reduction, turbulence
National Category
Fluid Mechanics and Acoustics
Research subject
Aerospace Engineering; Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-342442 (URN)10.1007/s10494-023-00475-6 (DOI)001058987600003 ()2-s2.0-85169823248 (Scopus ID)
Note

QC 20240123

Available from: 2024-01-19 Created: 2024-01-19 Last updated: 2024-01-23Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-9627-5903

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