## The CFD code karalis

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##### Data

2000-08-31

##### Autori

Mulas, Marco

Chibbaro, Sergio

Delussu, Giovanni

Di Piazza, Ivan

Talice, Marco

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##### Abstract

Karalis is a paralle MPI, Finite-Volume, multiblock CFD code which solves the fully compressible Euler and Navier-Stokes equations where all couplings between dynamics and thermodynamics are allowed. This the most general mathematical model for all fluid flows. The code solves the coupled system of continuity, momentum and full energy equation for the velocity components, pressure and temperature. Once, u, v, w, p are and T are updated, arbitrary thermodynamics is supplied. The second order Roe’s upwind TVD scheme is used to compute convective fluxes through the Finite-Volume cell interfaces. A V-cycle Coarse Grid Correction Multi-Grid algorithm is used, together with a 5-stage Runge-Kutta explicit time-marching method, to accelerate convergence to a steady state. This formulation, typical of aerodynamic flows, shows an eccellent efficiency even for incompressible flows as well as for flows of incompressible fluids (typically buoyancy flows), once equipped with a preconditioner. Merkel’s preconditioner has been chosen because it can be easily formulated for arbitrary equations of state given as a functional relation of two independent thermodynamic variables (typically the pressure p and the temperature T), or even in tabular form, read in as an input file and used with bilinear interpolation. Karalis implement two among the most popular turbulence models, namely the one-equation model by Spalart and Allmaras and the two-equations model by Wilcox, the k-ω model, which allow a good compromise between accuracy, robustness and stability of turbulent calculations. Code validation is presented for some typical benchmark test cases of incompressible fluid dynamics. Comparison with solutions obtained with a few popular commercial CFD codes is also presented.

##### Descrizione

##### Keywords

CFD , Navier-Stokes equations , turbulence model