Direct numerical simulation of turbulent Rayleigh-Benard convection using a higher order scheme

In the present paper a Direct Numerical Simulation of turbulent Rayleigh-Benard convection of a Boussinesq fluid with Prandtl number 0.7 in a 6: 6: 1 aspect ratio box at Ra = 2.10(6) is attempted. The incompressible Navier-Stokes equations are solved on non-uniform cartesian grids using a finite difference method with a high resolution convective scheme and 2nd order Adams-Bashforth Crank-Nicolson (ABCN) time-stepping. The numerical simulation is conducted on a parallel computer We observed that temperature and velocity variances lead to different length and temperature scales. Negative skewnesses of vertical velocity and its derivative are observed. A non-uniform distribution of temperature near the surface proceeds to an exponential like variation in the center via an intermediate region outside the surface layer Instantaneous snapshots of the flow field reveal intense sheet-like structures near the surface layers becoming plumes in the middle region. In the vertical cross-sectional planes, strong shearing effect near the surfaces, horizontal spreading and induction of plumes are observed.