Numerical Analysis of Low-Reynolds-Number Flows in Earth and Mars Atmosphere

The focus of the paper is on low-Reynolds-number flows in the incompressible and compressible regime. Incompressible is the regime of these flows in the Earth atmosphere. The interest for the compressible aerodynamics has, instead, recently grown for the possible use of flying machines for exploring the Martian surface. Separation occurring in the laminar regime and the possible formation of a bubble are likely the most important and critical phenomena of these flows. Reynolds-averaged Navier–Stokes (RANS) models with a transport equation for transition functions have been considered because of the fundamental role played by the transition. Large eddy simulations have also been performed. The NACA 0012-34 and the Ishii airfoils are the test cases considered and the achieved results are compared to reference data available in literature. The importance of freestream turbulence values for the RANS simulations has been highlighted. The behavior of the bubble with the incidence and the stall mechanism has been described. The dependence on the Mach number of the aerodynamic coefficients has been reproduced according to experimental data. The results of the large eddy simulations could be employed as input data for physics-informed neural networks to the aim of training RANS turbulence models for reproducing low-Reynolds-number flows.