Showing papers by "Sergio Pirozzoli published in 1999"

Analysis and simulation of a turbulent, compressible starting vortex

Abstract: The numerical simulation of a shock induced, turbulent compressible vortex is analyzed. The vortex is generated by the movement of an (unsteady) shock over the trailing-edge of a two-dimensional airfoil at different incidence angle. A theoretical analysis is performed for the case of a turbulent line vortex, at a low (vortex) Mach number and high Reynolds number, as a basis of comparison for the dynamic structure of the starting vortex. This theoretical analysis confirms the existence of an equilibrium structure of the isolated vortex similar to the laminar case. In the numerical computations, both an isotropic eddy viscosity two-equation turbulence model and an algebraic stress model are employed to assess the influence of turbulence model on the predictive capabilities of such a flow including the realization of the self-similar behavior found in the isolated vortex case. The results are also compared to theoretical estimates of the production-to-dissipation rate ratio for both types of turbulence model...

Asymptotic scaling of a decaying turbulent compressible vortex

Abstract: In the present work a theoretical analysis of the asymptotic decay of an isolated, compressible turbulent vortex is presented. The governing equations are expanded in powers of the vortex Mach number squared, and the asymptotic scaling both of the O(1) and the O(M2) variables is theoretically analyzed in the framework of an isotropic eddy viscosity two-equation turbulence model. Numerical simulations are presented to confirm the analytically predicted power-law decay, and to assess the influence of turbulence and of the initial thermodynamic state on the evolution both of a finite- and zero-circulation vortex. Regardless of the initial state, the simulations show that isolated turbulent compressible vortices decay according to a two-stage mechanism. For a finite-circulation vortex, the latter is found to be controlled primarily by the decay of vorticity and heat conduction, while for a zero-circulation vortex, the two-stage mechanism is associated with the reversal of the radial motion within the vortex core.