Precessional forcing of a mean geostrophic flow in a rotating cylinder

T. Albrecht, Patrice Meunier, Hugh Blackburn, Juan Lopez, Richard Manasseh

Research output: Contribution to conferenceAbstract

Abstract

It has often been observed that inertial waves in rotating flows can interact nonlinearly to create a mean geostrophic motion due to a streaming effect. This
mean geostrophic flow has a large effect in rotating flows since it changes the base flow and thereby detunes all the possible resonances. However, in a
cylinder, inviscid Kelvin modes (KM) are known theoretically to create \emph{no} mean geostrophic motion by nonlinear coupling. It was thus assumed that
the observed geostrophic flow relies on viscous effects in the Ekman boundary layers together with nonlinear interaction. We present here a simple flow
configuration where both the KM and the geostrophic flow can be quantified in order to analyse this mechanism in detail. We have studied the case of a KM
forced by precession. This allows to reach a very large amplitude of the KM at the resonance, even for small precession angles. PIV measurements are
compared to numerical simulations. The profiles of mean azimuthal velocity are studied in the laminar and in the turbulent case. They seem to be correlated
to the profiles of velocity of the forced KM. The amplitude of the geostrophic flow seems to agree with the viscous nonlinear theory which predicts that it
scales as the square of the forced KM's amplitude.
Original languageEnglish
Number of pages1
Publication statusPublished - 2014
EventAnnual Meeting of the APS Division of Fluid Dynamics 2014 - Moscone (West) Convention Center, San Francisco, United States of America
Duration: 23 Nov 201425 Nov 2014

Conference

ConferenceAnnual Meeting of the APS Division of Fluid Dynamics 2014
CountryUnited States of America
CitySan Francisco
Period23/11/1425/11/14

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