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Similarity solutions for stratified rotating-disk flow

Published online by Cambridge University Press:  21 April 2006

J. D. Goddard
Affiliation:
Department of Chemical Engineering, University of Southern California, Los Angeles, CA 90089–1211, USA
J. B. Melville
Affiliation:
Department of Chemical Engineering, University of Southern California, Los Angeles, CA 90089–1211, USA
K. Zhang
Affiliation:
Department of Chemical Engineering, University of Southern California, Los Angeles, CA 90089–1211, USA

Abstract

This work treats the vertically stratified system of two homogeneous fluid layers confined between horizontal infinite rotating disks which rotate steadily about a common vertical axis. Allowance is made for uniform injection of fluid at either disk. With appropriate restrictions on disk rotational speeds and injection rates a flat interface is possible, and the problem admits similarity solutions to the Navier-Stokes equations of the Kármán-Bödewadt-Batchelor variety. This type of flow allows for a uniformly accessible surface of interphase mass and heat transfer at the two-fluid interface, and, with that as the primary motivation, the present work provides exploratory numerical solutions of the above equations for both corotation and counter-rotation combined with injection.

A linearized theory is given for the case of nearly rigid rotation, with explicit analytical results for the large-Reynolds-number boundary-layer limit. Also, we offer a theoretical discussion of the inviscid limit for arbitrary rotation and injection rates. Based on the type of Euler-cell solutions identified in previous work, we derive the remarkably simple formula \[ \rho_1\omega_1^2\cot^2\frac{\omega_1d_1}{V_1} = \rho_2\omega^2_2\cot^2\frac{\omega_2d_2}{V_2} \] connecting densities ρ, depths d, rotation speeds ω and injection velocities V.

Sample calculations and comparisons are given for property ratios typical of water-kerosene layers. In this case, the linearized theory works exceedingly well for corotation with small injectional Rossby numbers Vd. The simple inviscid theory cited above shows excellent agreement with the numerical computations for Reynolds numbers greater than 500 and for Rossby numbers > 1/π, corresponding to strong blowing in the inviscid regime. The larger-wavelength inviscid cell structure appears to provide the kind of stagnation-flow pattern essential to the application envisaged.

Type
Research Article
Copyright
© 1987 Cambridge University Press

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