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Abstract: A stochastic model is derived to predict the turbulent torque produced by aswirling flow. It is a simple Langevin process, with a colored noise. Using theunified colored noise approximation, we derive analytically the PDF of thefluctuations of injected power in two forcing regimes: constant angularvelocity or constant applied torque. In the limit of small velocityfluctuations and vanishing inertia, we predict that the injected powerfluctuates twice less in the case of constant torque than in the case ofconstant angular velocity forcing. The model is further tested againstexperimental data in a von Karman device filled with water. It is shown toallow for a parameter-free prediction of the PDF of power fluctuations in thecase where the forcing is made at constant torque. A physical interpretation ofour model is finally given, using a quasi-linear model of turbulence.



Author: Nicolas Leprovost SPEC, Louis Marié SPEC, Bérengère Dubrulle SPEC

Source: https://arxiv.org/







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