PIV mapping of pressure and velocity fields in the plane magnetohydrodynamic Couette flow

Alban Potherat, Brahim Moudjed, Martin Holdsworth

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    Abstract

    We present the first simultaneous mapping of two-dimensional, time-dependent velocity and pressure fields in a plane Couette flow pervaded by a transverse magnetic field. While electromagnetic forces are strongest in fluids of high electric conductivity such as liquid metals, their opacity excludes optical measurement methods. We circumvent this difficulty using a transparent electrolyte (sulphuric acid), whose weaker conductivity is offset by higher magnetic fields. We describe an experimental rig based on this idea, where the Couette flow is entrained by a tape immersed in sulphuric acid and positioned flush onto the bore of large superconducting magnet, so that most of the flow is pervaded by a sufficiently homogeneous transverse magnetic field. Velocity and pressure fields are obtained by means of a bespoke PIV system, capable of recording the fluid’s acceleration as well as its velocity. Both fields are then fed into a finite difference solver that extracts the pressure field from the magnetohydrodynamic governing equations. This method constitutes the first implementation of the pressure PIV technique to an MHD flow. Thanks to it, we obtain the first experimental velocity and pressure profiles in an MHD Couette flows and show that the transitional regime between laminar and turbulent states is dominated by near-wall, isolated, anisotropic perturbations.
    Original languageEnglish
    Article number255
    Number of pages17
    JournalExperiments in Fluids
    Volume61
    Issue number12
    Early online date18 Nov 2020
    DOIs
    Publication statusPublished - Dec 2020

    Bibliographical note

    The final publication is available at Springer via http://dx.doi.org/10.1007/s00348-020-03090-7

    Copyright © and Moral Rights are retained by the author(s) and/ or other copyright owners. A copy can be downloaded for personal non-commercial research or study, without prior permission or charge. This item cannot be reproduced or quoted extensively from without first obtaining permission in writing from the copyright holder(s). The content must not be changed in any way or sold commercially in any format or medium without the formal permission of the copyright holders.

    ASJC Scopus subject areas

    • Computational Mechanics
    • Mechanics of Materials
    • Physics and Astronomy(all)
    • Fluid Flow and Transfer Processes

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