FOURIER-WEIERSTRASS MODE ANALYSIS FOR THERMALLY DRIVEN TURBULENCE

The eddy size and temperature distribution in the inertial subrange of turbulent Rayleigh-Benard flow at a Rayleigh number Ra almost-equal-to 10(11) is calculated from the Boussinesq equations. Velocity and temperature fields are decomposed into Fourier modes with geometrically scaling wave numbers. 1/3 scaling for both velocity-mu and temperature-THETA is obtained in agreement with Shraiman and Siggia's finding, but there is no indication of a new scaling range as claimed recently. We resolve this discrepancy. The isotropization by eddy decay is demonstrated in terms of the mu-3-THETA scaling, which appreciably differs from 2/3; testing this new quantity experimentally would be of great interest.