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The generation of turbulent inflow boundary conditions using precursor channel flow simulations
Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Numerical Analysis.
2017 (English)In: Computers & Fluids, ISSN 0045-7930, E-ISSN 1879-0747, Vol. 156, p. 21-33Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2017. Vol. 156, p. 21-33
National Category
Computational Mathematics
Identifiers
URN: urn:nbn:se:uu:diva-302801DOI: 10.1016/j.compfluid.2017.06.020ISI: 000411848100003OAI: oai:DiVA.org:uu-302801DiVA, id: diva2:967721
Projects
eSSENCEAvailable from: 2017-06-23 Created: 2016-09-09 Last updated: 2018-08-05Bibliographically approved
In thesis
1. Inflow generation for scale-resolving simulations of turbulent boundary layers
Open this publication in new window or tab >>Inflow generation for scale-resolving simulations of turbulent boundary layers
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Generating inflow fields for scale-resolving simulations of turbulent flow is crucial for a wide range of applications and is an active area of research. In this thesis, a method for inflow generation employing a precursor turbulent channel flow simulation is proposed. A procedure for determining the parameters of the precursor simulation based on the properties of the inflow is given. To evaluate the performance of the method, results from a simulation of a flat-plate zero-pressure-gradient turbulent boundary layer are analysed. The adaption length is quantified in terms of the development of integral quantities and the statistical moments of the velocity field. The performance is also compared with that of a state-of-the-art rescaling method for the generation of inflow data. It is shown that both approaches result in adaption lengths of comparable sizes, which makes the proposed method an attractive alternative due to its conceptual simplicity and robustness.

As part of the work on inflow generation, a Python package, eddylicious, was developed. The purpose of the package is to be a framework within which various generation methods can be implemented. The package is available online under an open-source license. An overview of the architecture and currently implemented functionality of the package is given in this thesis.

Furthermore, the results of a preparatory study on large-eddy simulation of wall-bounded turbulent flows are discussed. Fully-developed turbulent channel flow is used as a model problem, and the general-purpose computational fluid dynamics solver OpenFOAM is employed. The accuracy of the results with respect to the resolution of the computational mesh is analysed. Several modelling approaches for the subgrid scale stresses are considered.

Place, publisher, year, edition, pages
Uppsala University, 2016
Series
Information technology licentiate theses: Licentiate theses from the Department of Information Technology, ISSN 1404-5117 ; 2016-009
National Category
Computational Mathematics
Research subject
Scientific Computing with specialization in Numerical Analysis
Identifiers
urn:nbn:se:uu:diva-302808 (URN)
External cooperation:
Supervisors
Available from: 2016-09-09 Created: 2016-09-09 Last updated: 2016-09-09Bibliographically approved
2. Modelling Techniques for Large-Eddy Simulation of Wall-Bounded Turbulent Flows
Open this publication in new window or tab >>Modelling Techniques for Large-Eddy Simulation of Wall-Bounded Turbulent Flows
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Large-eddy simulation (LES) is a highly accurate turbulence modelling approach in which a wide range of spatial and temporal scales of the flow are resolved. However, LES becomes prohibitively computationally expensive when applied to wall-bounded flows at high Reynolds numbers, which are typical of many industrial applications. This is caused by the need to resolve very small, yet dynamically important flow structures found in the inner region of turbulent boundary layers (TBLs). To remove the restrictive resolution requirements, coupling LES with special models for the flow in the inner region has been proposed. The predictive accuracy of this promising approach, referred to as wall-modelled LES (WMLES), requires further analysis and validation. 

In this work, systematic simulation campaigns of canonical wall-bounded flows have been conducted to support the development of a complete methodology for highly accurate WMLES on unstructured grids. Two novel algebraic wall-stress models are also proposed and shown to be more robust and precise than the classical approaches of the same type. 

For turbulence simulations, it is often challenging to provide accurate conditions at the inflow boundaries of the domain. Here, a novel methodology is proposed for generating an inflow TBL using a precursor simulation of turbulent channel flow. A procedure for determining the parameters of the precursor based on the Reynolds number of the inflow TBL is given. The proposed method is robust and easy to implement, and its accuracy is demonstrated to be on par with other state-of-the-art approaches. 

To make the above investigations possible, several software packages have been developed in the course of the work on this thesis. This includes a Python package for post-processing the flow simulation results, a Python package for inflow generation methods, and a library for WMLES based on the general-purpose software for computational fluid dynamics OpenFOAM. All three codes are publicly released under an open-source licence to facilitate their use by other research groups.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 91
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1697
Keywords
Wall modelling, Inflow generation, Large-eddy simulation, OpenFOAM, Computational fluid dynamics
National Category
Computational Mathematics
Research subject
Scientific Computing
Identifiers
urn:nbn:se:uu:diva-356729 (URN)978-91-513-0394-9 (ISBN)
Public defence
2018-09-21, ITC 2446, Lägerhyddsvägen 2, Uppsala, 10:15 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 621-2012-3721
Available from: 2018-08-31 Created: 2018-08-05 Last updated: 2018-09-10

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Mukha, TimofeyLiefvendahl, Mattias

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