Numerical Simulation of Nonpenetrative Turbulent Thermal Convection

Nonpenetrative convection Ð in which the lower boundary condition is one of constant heat flux and the upper boundary is insulatedÐ is an idealization of penetrative convection, which finds application in the planetary boundary layer. Three-dimensional, unsteady, ( ) direct numerical simulations 96 = 96 = 128 have been performed of turbulent, nonpene7 trative thermal convection inside a cubical enclosure at Ras 2= 10 . While the bulk temperature of the fluid increases linearly with time, the spatially averaged temperature profile exhibits a time-invariant behavior along the vertical coordinate. The numerical ( ) study has replicated results from earlier Particle Image Velocimetry PIV measurements of the same flow, in a 76.2 mm thick layer of water, at an aspect ratio of 6.6. Time-averaged vertical profiles of mean, root-mean-square, and skewness of velocity and temperature profiles compare well with experiments. Instantaneous velocity maps and temperature contours are also in good agreement with previous experimental results. Finally, while both the upper and lower boundary temperatures increase linearly with time, their difference is constant and matches well with analytical predictions.