Extended Abstract (248K)P3.9
Measuring the viscous dissipation of turbulent kinetic energy with a hotwire and a sonic anemometer
Jan Slager, Utrecht University, Utrecht, Netherlands; and P. G. Duynkerke and A. van Dijk
We used a combination of a sonic- and a hotwire anemometer to measure the smallest structures in the atmospheric boundary layer, with the aim to evaluate the kinetic energy balances under different stability conditions. The sonic anemometer was used to calibrate the hotwire anemometer. Details of the calibration method will be given in the presentation. Experiments to estimate viscous dissipation were performed near and at the 213 m Cabauw tower of KNMI. We will show two different methods to estimate viscous dissipation: by direct computation and using Kolmogorov?s four-fifths law. The resulting estimates will be shown to agree within measurement accuracy. Furthermore we will estimate Kolmogorov?s constant and compare the resulting estimate with earlier measurements. We will show that our results indicate that in convective conditions (-2 < z/L < 0) production is larger than dissipation, suggesting a negative transport term. For stable conditions (0 < z/L < 5) it will be shown that dissipation is larger than production. This may also indicate a transport term, but with a positive sign.
Poster Session 3, Fundamental Studies
Tuesday, 16 July 2002, 2:00 PM-2:00 PM
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