Random vortex-street model for a self-similar plane turbulent jet |
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Authors: | L'vov Victor S Pomyalov Anna Procaccia Itamar Govindarajan Rama |
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Institution: | Department of Chemical Physics, The Weizmann Institute of Science, Rehovot 76100, Israel. |
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Abstract: | We ask what determines the (small) angle of turbulent jets. To answer this question we first construct a deterministic vortex-street model representing the large-scale structure in a self-similar plane turbulent jet. Without adjustable parameters the model reproduces the mean velocity profiles and the transverse positions of the large-scale structures, including their mean sweeping velocities, in a quantitative agreement with experiments. Nevertheless, the exact self-similar arrangement of the vortices (or any other deterministic model) necessarily leads to a collapse of the jet angle. The observed (small) angle results from a competition between vortex sweeping tending to strongly collapse the jet and randomness in the vortex structure, with the latter resulting in a weak spreading of the jet. |
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