Stability lecture 14

Stability lecture 14 - Lecture 14 Experiments: 1. Benard...

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Lecture 14 Experiments: 1. Benard (1900) Used a number of different liquids with high viscosity v . Thin layers, less than 1mm thick. Water heated at the bottom Circulated hot water across solid surface to maintain constant temperature of wall. Observed regular hexagonal cell pattern, start at subcritical values. Flow is up in the middle, down on side of cells. This interested Rayleigh in the experiment. 2. Silveston (1958) – 1 st accurate measurements of Rayleigh number. Water cooled at top Electrical heating 1 mm h < Very careful, elaborate experiments for a broad range of Ra. He was able to measure the heat flux of the bottom by monitoring the electric current. 1
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Plotted: Actual heat flux/area Pure conduction heat flux/area (Nusselt number) vs. Ra Q Nu T k h Nu == Similar to figures 13 & 14 in Chandrasekhar or 2.6 in D & R or figure 6.4 in Drazin (pg. 101). Nonlinear heat transfer is also a function of Pr. He also estimated a critical R , theoretical value 1708. a 1700 51 C Maybe eventually get turbulent convection.
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This note was uploaded on 06/07/2011 for the course EOC 6934 taught by Professor Staff during the Fall '08 term at University of Florida.

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Stability lecture 14 - Lecture 14 Experiments: 1. Benard...

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