Numerical study of unsteady turbulent cavitating flows
Abstract The simulation of cavitating flows is a challenging problem both in terms of modelling the physics and developing robust numerical methodologies. Such flows are characterized by important variations of the local Mach number, compressibility effects on turbulence and involve thermodynamic phase transition. To simulate these flows by applying homogeneous models and Reynolds averaged codes, the turbulence modelling plays a major role in the capture of unsteady behaviours. This paper presents a one-fluid compressible Reynolds-Averaged Navier–Stokes (RANS) solver with a simple equation of state (EOS) for the mixture. A special focus is devoted to the turbulence model influence. Unsteady numerical results are given for Venturi geometries and comparisons are made with experimental data.
Populations oscillations in isolated populations of flies are considered. Qualitative methods of analysis are applied to the functional differential equation representing the system and conditions for the occurrence of oscillations are derived. These conditions are readily visualized in terms of parameters which are easily measured and have a straightforward biological interpretation.