Particle image velocimetry measurement of the velocity field in turbulent thermal convection.

Phys Rev E Stat Nonlin Soft Matter Phys

Department of Physics, The Chinese University of Hong Kong, Shatin, Hong Kong, China.

Published: December 2003

The spatial structure of the velocity field in turbulent Rayleigh-Bénard convection in water has been measured using the particle image velocimetry technique, with the Rayleigh number Ra varying from 9 x 10(8) to 9 x 10(11) and the Prandtl number remaining approximately constant (Pr approximately 4). The study provides a direct confirmation that a rotatory mean wind indeed persists for the highest value of Ra reached in the experiment. The measurement reveals that the mean flow in the central region of the convection cell is of the shape of a coherent elliptical rotating core for Ra below 1 x 10(10). Above this Ra, the orientation of the elliptical core changes by a 90 degrees angle and an inner core rotating at a lower rate inside the original bulk core emerges. It is further found that the rotation frequencies of the inner core and the outer shell have distinct scalings with Ra; the scaling exponent for the outer-shell is 0.5 and it is 0.4 for the inner core. From the measured rms and skewness distributions of the velocity field, we find that velocity fluctuations at the cell center are neither homogeneous nor isotropic. The turbulent energy production fields further reveal that the mean wind is not driven by turbulent fluctuations associated with Reynolds stress.

Download full-text PDF

Source
http://dx.doi.org/10.1103/PhysRevE.68.066303DOI Listing

Publication Analysis

Top Keywords

velocity field
12
inner core
12
particle image
8
image velocimetry
8
field turbulent
8
core
6
velocimetry measurement
4
velocity
4
measurement velocity
4
turbulent
4

Similar Publications

Want AI Summaries of new PubMed Abstracts delivered to your In-box?

Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!