Unsteady Three-Dimensional Behavior of Natural Convection in Horizontal Annulus. (II). Flow Patterns in Range from Transition Region to Turbulence and Measurements of Turbulence Quantities

The velocity and temperature distributions are measured for natural convection in a horizontal concentric annulus at high Rayleigh numbers with using a hot-wire anemometer and a thermocouple. Dealing with these data statistically, the average velocity and temperature profiles as well as their turbulence quantities are obtained. By carrying out the spectrum analysis of these velocity fluctuations, a transition from the laminar natural convection to the turbulent one is clarified. With increasing Rayleigh number, the stable flow pattern becomes unstable to a periodic one. The periodicity diminishes when the Rayleigh number is further increased. A comparison of these experimental data with the time-dependent three-dimensional numerical results, which were reported in our previous paper, shows a good agreement.