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arXiv · 1603.06484

Turbulent drag in a rotating frame

Antoine Campagne·Nathanaël Machicoane·Basile Gallet·Pierre-Philippe Cortet·Frédéric Moisy
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Abstract

What is the turbulent drag force experienced by an object moving in a rotating fluid? This open and fundamental question can be addressed by measuring the torque needed to drive an impeller at constant angular velocity $\omega$ in a water tank mounted on a platform rotating at a rate $\Omega$. We report a dramatic reduction in drag as $\Omega$ increases, down to values as low as $12$\% of the non-rotating drag. At small Rossby number $Ro = \omega/\Omega$, the decrease in drag coefficient $K$ follows the approximate scaling law $K \sim Ro$, which is predicted in the framework of nonlinear inertial wave interactions and weak-turbulence theory. However, stereoscopic particle image velocimetry measurements indicate that this drag reduction rather originates from a weakening of the turbulence intensity in line with the two-dimensionalization of the large-scale flow.

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Antoine Campagne, Nathanaël Machicoane, Basile Gallet, Pierre-Philippe Cortet, Frédéric Moisy. 2016-03-21. Turbulent drag in a rotating frame. https://doi.org/10.1017/jfm.2016.214

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