| Popis: |
An experimental study of high level turbulence natural convection in a 4m-height differentially heated cavity was conducted at large Rayleigh numbers (4.0×1010≤ RaH ≤1.2×1011). In this study, turbulence quantities including θRMS (θ′), VRMS (V′), WRMS (W′), turbulent kinetic energy (k) are presented. The power spectral densities show a characteristics frequency of about 0.046 Hz in the core region indicating the existence of internal waves. In the boundary layer, we recorded higher frequency up to 4.5 Hz along the fluid flow. Periodic oscillations in the form of Tollmien-Schlichting waves are found in the boundary layer, near the isothermal walls (from the wall to about 7 mm). The results indicate that the decay of spectrum follows an f -3 law in the boundary layer. Large-scale vortex structures are identified mainly on the edge of the hot boundary layer. |
