Stabilité globale de l'écoulement compressible autour d'un cylindre de section parabolique

Global stability of compressible flow about a swept parabolic body

• Auteur / Autrice : Christoph Mack
• Direction : Peter Schmid
• Type : Thèse de doctorat
• Discipline(s) : Mécanique
• Date : Soutenance en 2009
• Etablissement(s) : Palaiseau, Ecole polytechnique

Mots clés

Mots clés contrôlés

Compressibilité

Mots clés libres

Stabilité globale

Simulation numérique directe

Méthodes de tpe Krylov

Transformation de Cayley

Résumé

The present thesis is concerned with the global stability of compressible flow in the leading-edge region of a swept blunt body, a flow situation which can be found in many engineering applications. It is the goal of the present study to investigate a more comprehensive model and to thus gain new insight into the complex stability characteristics of this flow. To this end, two objectives have been pursued: (i) a powerful DNS-based global stability solver has been developed and (ii) this stability algorithm has then been employed to extract stability information from our flow model. The former objective has been accomplished by combining direct numerical simulations (DNS) and Krylov methods using a matrix-free implementation; furthermore, a Cayley transformation as well as preconditioning techniques are used to add, on the one hand, flexibility and, on the other hand, robustness and efficiency to our algorithm. The developed stability algorithm has then been employed to study the global stability of compressible flow about a swept parabolic body. The computed spectrum provides a comprehensive picture of the temporal perturbation dynamics of this flow and, as a result, a wide and rich variety of global modes has been uncovered: boundary-layer modes, different types of acoustic modes and wave packet modes have been found. Furthermore, boundary-layer modes connecting attachment-line and crossflow instabilities as well as composite global modes featuring both the structure of boundary-layer and acoustic instabilities have been computed. Moreover, the neutral curve for boundary-layer and acoustic modes has been presented