A local sensor for joint temperature and velocity measurements in turbulent flows.

We present the principle for a micro-sensor aimed at measuring local correlations of turbulent velocity and temperature. The operating principle is versatile and can be adapted for various types of flow. It is based on a micro-machined cantilever, on the tip of which a platinum resistor is patterned.

Turbulent boundary layer in high Rayleigh number convection in air.

Flow visualizations and particle image velocimetry measurements in the boundary layer of a Rayleigh-Bénard experiment are presented for the Rayleigh number Ra=1.4×1010. Our visualizations indicate that the appearance of the flow structures is similar to ordinary (isothermal) turbulent boundary layers.

Boundary layer analysis in turbulent Rayleigh-Bénard convection in air: experiment versus simulation.

We report measurements and numerical simulations of the three-dimensional velocity and temperature fields in turbulent Rayleigh-Bénard convection in air. Highly resolved velocity and temperature measurements inside and outside the boundary layers have been directly compared with equivalent data obtained in direct numerical simulations (DNSs). This comparison comprises a set of two Rayleigh numbers at Ra=3×10(9) and 3×10(10) and a fixed aspect ratio; this is the ratio between the diameter and the height of the Rayleigh-Bénard cell of Γ=1.

Thickness of the diffusive sublayer in turbulent convection.

In this paper we address the following question: how thick is the diffusive fraction of the thermal boundary layer in highly turbulent thermal convection? We have studied this problem in a large-scale Rayleigh-Bénard experiment at fixed aspect ratio Gamma=1.13 and variable Rayleigh number 5.2x10(10) View Article and Find Full Text PDF

Structure of viscous boundary layers in turbulent Rayleigh-Bénard convection.

Highly resolved profiles of the mean velocity in turbulent Rayleigh-Bénard convection in air are presented and discussed. The present work extends our recently performed experiments at constant aspect ratio [Phys. Rev.

Mean velocity profile in confined turbulent convection.

In this Letter, highly resolved measurements of the horizontal velocity inside the boundary layer of turbulent Rayleigh-Bénard convection are reported. They were performed in a cylindrical box with an aspect ratio Gamma=1.13 which was filled with air with a Prandtl number Pr=0.

Breakdown of wind in turbulent thermal convection.

We report experiments on turbulent Rayleigh-Bénard convection of air in a cylindrical large-scale facility with a diameter of 7 meters and Rayleigh numbers up to Ra approximately 10(12). The facility is used to explore the structure of the large-scale circulation for continuously varying aspect ratios between Gamma approximately 1 and Gamma approximately 10. Using autocorrelation functions derived from high-resolution time series of temperature and velocity near the cooling plate we demonstrate that the well-known single-roll structure (often called "wind") breaks down when the aspect ratio increases beyond the critical value Gamma(1) = 1.