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Improving roughness models using high order direct numerical simulations and immersed boundary conditions

MEGEP (Mécanique, Energétique, Génie civil & Procédés)

https://rdv.onera.fr/soutenance-eloise-dayer

The presence of roughness on aeronautical surfaces can lead to an increase in drag and heat transfer. In order to define RANS models that includes roughness effect on the flow, database of flow over rough surfaces must be first obtained  from direct numerical simulations (DNS).

In this PhD thesis, the JAGUAR solver developed by ONERA and CERFACS is used  with this objective. This solver uses the spectral difference (SD) method to discretize the computational domain. Because of the large element size in the SD method, an Immersed Boundary Method (IBM) must be used to allow the inclusion of rough surfaces in the computations. In this regard, the volume penalization method was chosen. The combination of this IBM and the SD method is tested by simulating the steady flow over a cylinder. Interactions between the IBM and the SD method are analyzed from this first test case. Then, the turbulent flow over an academic rough surface is determined with and without the IBM. Those computations shows that the IBM is capable of reproducing the results obtained by the classical SD method for these academic rough surfaces. Finally, the turbulent flow over a more complex and realistic rough surface is computed. The final results shows that it is possible to build a DNS database of flow over complex rough surfaces with the IBM and the JAGUAR solver.

Jury

Koen HILLEWAERT	Université de Liège	Reviewer
Sébastien TORDEUX	Université de Pau et des Pays de l'Adour	Reviewer
Éric GONCALVES DA SILVA	ENSMA	Examiner
Guillaume PUIGT	ONERA	Examiner
Héloïse BEAUGENDRE	ENSEIRB-MATMECA	Examiner
François CHEDEVERGNE	ONERA	Thesis supervisor
Arthur COLOMBIÉ	CERFACS, IPSA	Thesis co-supervisor
Omar DOUNIA	CERFACS	Thesis co-supervisor