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Anisotropy-resolving subgrid-scale modelling using explicit algebraic closures for large eddy simulationPrimeFaces.cw("AccordionPanel","widget_formSmash_some",{id:"formSmash:some",widgetVar:"widget_formSmash_some",multiple:true}); PrimeFaces.cw("AccordionPanel","widget_formSmash_all",{id:"formSmash:all",widgetVar:"widget_formSmash_all",multiple:true});
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PrimeFaces.cw("AccordionPanel","widget_formSmash_responsibleOrgs",{id:"formSmash:responsibleOrgs",widgetVar:"widget_formSmash_responsibleOrgs",multiple:true}); 2014 (English)Doctoral thesis, comprehensive summary (Other academic)
##### Abstract [en]

##### Place, publisher, year, edition, pages

Stockholm: KTH Royal Institute of Technology, 2014. , vii, 48 p.
##### Series

TRITA-MEK, ISSN 0348-467X ; 2014:07 2014:07
##### Keyword [en]

Turbulence, large eddy simulation, explicit algebraic subgridscale model, passive scalar, stochastic modelling, periodic hill flow
##### National Category

Fluid Mechanics and Acoustics
##### Research subject

Engineering Mechanics
##### Identifiers

URN: urn:nbn:se:kth:diva-142401ISBN: 978-91-7595-038-9OAI: oai:DiVA.org:kth-142401DiVA: diva2:700132
##### Public defence

2014-03-14, F3, Lindstedsvägen 26, KTH, Stockholm, 10:15 (English)
##### Opponent

PrimeFaces.cw("AccordionPanel","widget_formSmash_j_idt455",{id:"formSmash:j_idt455",widgetVar:"widget_formSmash_j_idt455",multiple:true});
##### Supervisors

PrimeFaces.cw("AccordionPanel","widget_formSmash_j_idt461",{id:"formSmash:j_idt461",widgetVar:"widget_formSmash_j_idt461",multiple:true});
#####

PrimeFaces.cw("AccordionPanel","widget_formSmash_j_idt467",{id:"formSmash:j_idt467",widgetVar:"widget_formSmash_j_idt467",multiple:true});
##### Projects

Explicit algebraic sub-grid scale modelling for large-eddy simulations
##### Funder

Swedish Research Council, 621-2010- 6965
##### Note

##### List of papers

The present thesis deals with the development and performance analysis ofanisotropy-resolving models for the small, unresolved scales (”sub-grid scales”,SGS) in large eddy simulation (LES). The models are characterised by a descriptionof anisotropy by use of explicit algebraic models for both the subgridscale(SGS) stress tensor (EASSM) and SGS scalar flux vector (EASSFM). Extensiveanalysis of the performance of the explicit algebraic SGS stress model(EASSM) has been performed and comparisons made with the conventionalisotropic dynamic eddy viscosity model (DEVM). The studies include LES ofplane channel flow at relatively high Reynolds numbers and a wide range ofresolutions and LES of separated flow in a channel with streamwise periodichill-shaped constrictions (periodic hill flow) at coarse resolutions. The formersimulations were carried out with a pseudo-spectral Navier–Stokes solver, whilethe latter simulations were computed with a second-order, finite-volume basedsolver for unstructured grids. The LESs of channel flow demonstrate that theEASSM gives a good description of the SGS anisotropy, which in turn gives ahigh degree of resolution independence, contrary to the behaviour of LES predictionsusing the DEVM. LESs of periodic hill flow showed that the EASSMalso for this case gives significantly better flow predictions than the DEVM.In particular, the reattachment point was much better predicted with the EASSMand reasonably well predicted even at very coarse resolutions, where theDEVM is unable to predict a proper flow separation.The explicit algebraic SGS scalar flux model (EASSFM) is developed toimprove LES predictions of complex anisotropic flows with turbulent heat ormass transfer, and can be described as a nonlinear tensor eddy diffusivity model.It was tested in combination with the EASSM for the SGS stresses, and itsperformance was compared to the conventional dynamic eddy diffusivity model(DEDM) in channel flow with and without system rotation in the wall-normaldirection. EASSM and EASSFM gave predictions of high accuracy for meanvelocity and mean scalar fields, as well as stresses and scalar flux components.An extension of the EASSM and EASSFM, based on stochastic differentialequations of Langevin type, gave further improvements. In contrast to conventionalmodels, these extended models are able to describe intermittent transferof energy from the small, unresolved scales, to the resolved large ones.The present study shows that the EASSM/EASSFM gives a clear improvementof LES of wall-bounded flows in simple, as well as in complex geometriesin comparison with simpler SGS models. This is also shown to hold for a widerange of resolutions and is particularly accentuated for coarse resolution. The advantages are also demonstrated both for high-order numerical schemes andfor solvers using low-order finite volume methods. The models therefore havea clear potential for more applied computational fluid mechanics.

QC 20140304

Available from: 2014-03-04 Created: 2014-03-03 Last updated: 2014-03-04Bibliographically approved1. Effects of modelling, resolution and anisotropy of subgrid-scales on large eddy simulations of channel flow$(function(){PrimeFaces.cw("OverlayPanel","overlay404718",{id:"formSmash:j_idt503:0:j_idt507",widgetVar:"overlay404718",target:"formSmash:j_idt503:0:partsLink",showEvent:"mousedown",hideEvent:"mousedown",showEffect:"blind",hideEffect:"fade",appendToBody:true});});

2. Large eddy simulation of channel flow with andwithout periodic constrictions using the explicit algebraic subgrid-scale model$(function(){PrimeFaces.cw("OverlayPanel","overlay700102",{id:"formSmash:j_idt503:1:j_idt507",widgetVar:"overlay700102",target:"formSmash:j_idt503:1:partsLink",showEvent:"mousedown",hideEvent:"mousedown",showEffect:"blind",hideEffect:"fade",appendToBody:true});});

3. A comparison between isotropic and anisotropy-resolving closures in large eddy simulation of separated flow$(function(){PrimeFaces.cw("OverlayPanel","overlay700110",{id:"formSmash:j_idt503:2:j_idt507",widgetVar:"overlay700110",target:"formSmash:j_idt503:2:partsLink",showEvent:"mousedown",hideEvent:"mousedown",showEffect:"blind",hideEffect:"fade",appendToBody:true});});

4. An explicit algebraic model for the subgrid-scale passive scalar flux$(function(){PrimeFaces.cw("OverlayPanel","overlay634176",{id:"formSmash:j_idt503:3:j_idt507",widgetVar:"overlay634176",target:"formSmash:j_idt503:3:partsLink",showEvent:"mousedown",hideEvent:"mousedown",showEffect:"blind",hideEffect:"fade",appendToBody:true});});

5. A stochastic extension of the explicit algebraic subgrid-scales models$(function(){PrimeFaces.cw("OverlayPanel","overlay700097",{id:"formSmash:j_idt503:4:j_idt507",widgetVar:"overlay700097",target:"formSmash:j_idt503:4:partsLink",showEvent:"mousedown",hideEvent:"mousedown",showEffect:"blind",hideEffect:"fade",appendToBody:true});});

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