Rayleigh–Bénard flow of a rarefied gas and its attractors. III. Three-dimensional computer simulations

Abstract

We investigate the three-dimensional Rayleigh–Bénard flow for a set of different Knudsen and Froude numbers at a fixed temperature ratio r=0.1, as well as for different aspect ratios. We observe a variety of stable vortex structures in the form of rolls, squares, and more complicated polygonal patterns. For sufficiently low Knudsen numbers, the existence of irregular regimes was confirmed. Two numerical approaches (the direct simulation Monte Carlo method and a finite-difference method for the Navier–Stokes equation) are used and the results show a satisfactory agreement.