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Author:Brockmann, Tomas
Title:Suurten pyörteiden menetelmän soveltaminen huonetilailmastoinnin simulointiin
Method of Large Eddy Simulation Applied to Recirculating Ventilation Flow in a Room
Publication type:Master's thesis
Publication year:2008
Pages:124      Language:   fin
Department/School:Informaatio- ja luonnontieteiden tiedekunta
Degree programme:Teknillisen fysiikan ja matematiikan tutkinto-ohjelma
Main subject:Lämpötekniikka ja koneoppi   (Ene-39)
Supervisor:Siikonen, Timo
Instructor:Majander, Petri
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark T80     | Archive
Keywords:OpenFOAM
indoor ventilation flow
LES
OpenFOAM
huonetilavirtaukset
LES
Abstract (eng): The purpose of this work was to become familiar with OpenFOAM and to apply the large eddy simulation method to some low-Reynolds-number flow case.
OpenFOAM is a C++ library that is enjoying growing interest around the world.
Its main purpose is to allow the creation of applications for the solution of fluid dynamic problems.
The large eddy simulation method is a way of modelling turbulence.
The effects of small eddies are modelled while the flow is solved accurately on the large scale.

This work began with a channel flow simulation to get used to computational fluid dynamics.
The essential work then was to solve an indoor ventilation flow case by applying the large eddy simulation method.
Traditionally, turbulent flows are solved in such a way that turbulence is completely modelled and only a steady-state flow solution is solved.
Such a result depends heavily on the properties of the turbulence model applied and the solution is not always realistic.
The large eddy simulation method is considered as an increasingly interesting alternative since the required number-crunching resources are becoming affordable.

Computational times appeared prohibitively long without parallel running on many, preferably dozens of cores.
The required computational effort limits the size and complexity of the mode to be simulated.
Simulation results do not quite match the corresponding experimental measurements, but most of this can be attributed to the lack of inflow turbulence.
Apart from this,the results appear promising.

Some time-averaged simulations were applied to the indoor ventilation case too, but the turbulence models appeared to have their shortcomings.
Abstract (fin): Työn tarkoitus on OpenFOAMin käyttöönotto ja suurten pyörteiden menetelmän soveltaminen jonkin matalan Reynoldsin luvun virtauksen ratkaisemiseen.
OpenFOAM on enenevässä määrin suosiota saavuttava avoin C++ kirjasto, joka antaa edellytykset monenlaisten virtaussimulointiongelmien ratkaisemiseen.
Suurten pyörteiden menetelmä puolestaan on eräs tapa mallintaa turbulenssia.
Pienempien pyörteiden vaikutus virtaukseen mallinnetaan, ja suuremmat pyörteet ratkaistaan ajan suhteen tarkasti.

Työn alussa simuloitiin kanavavirtauksia virtaussimulointiin ja OpenFOAMiin tutustumiseksi.
Päätyö oli simuloida huonetilavirtauksia suurten pyörteiden menetelmällä.
Perinteisesti virtaussimuloinnissa on turbulenssi mallinnettu kokonaan ja ratkaistu keskiarvovirtauksia.
Tällainen ratkaisu riippuu kuitenkin pitkälti turbulenssimallista ja sen ominaisuuksista.
Tietokoneiden kehittyessä ja laskentatehojen kasvaessa suurten pyörteiden menetelmän soveltaminen tulee mahdolliseksi vaihtoehdoksi.

Työssä saadaan käsitys suurten pyörteiden menetelmän soveltuvuudesta huonetilavirtausten simulointiin.
Laskenta-ajat ovat kohtuuttomia, ellei laskentaa voida rinnakkaistaa useille, mieluummin kymmenille ytimille.
Vaatimus kohtuullisesta laskenta-ajasta asettaa rajoituksia laskentaverkon koolle ja siten laskentatilavuuden monimutkaisuudelle.
Simulointitulokset eivät aivan vastaa koehuoneen mittaustuloksia, mutta tämän voidaan pääasiassa katsoa johtuvan sisäänvirtauksen turbulenssin puutteesta.

Lopuksi simuloitiin vielä keskiarvotettua huonetilavirtausta.
Menetelmän soveltuminen jättää toivomisen varaa ja siten lisää mielenkiintoa suurten pyörteiden menetelmää kohtaan.
ED:2009-05-08
INSSI record number: 37388
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