Session Da - Turbulent Jets & Wakes; Instabilities.
ORAL session, Monday, November 24
301, Moscone Center
Grid turbulence in a flowing soap film is investigated with ambient pressure P as one of the control parameters. Reducing P significantly decreases air drag thus minimizing three-dimensional effects on the flowing film. It was found that while the total kinetic energy \varepsilon=\int E(k)dk of velocity fluctuations increased noticeably as P was reduced, the energy spectrum E(k) for wavenumbers greater than the injection scale was remarkably insensitive to the pressure change, and obeyed a power law E(k)\sim k^-3.3\pm 0.3. Our experimental results are in good qualitative agreements with a recent numerical simulation on decaying two-dimensional turbulence.
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