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A computer-controlled four-roll mill for investigations of particle and drop dynamics in two-dimensional linear shear flows

Published online by Cambridge University Press:  21 April 2006

B. J. Bentley  and
L. G. Leal
B. J. Bentley
Affiliation:
Chemical Engineering Department, California Institute of Technology, Pasadena, CA 91125, USA
L. G. Leal
Affiliation:
Chemical Engineering Department, California Institute of Technology, Pasadena, CA 91125, USA
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Abstract

In this paper we describe the design and operating characteristics of a computer-controlled four-roll mill for investigations of particle and drop dynamics in two-dimensional linear flows. The control system is based upon the use of: a video camera to visualize the instantaneous position of the drop or particle; a PDP 11/23 computer, with a pipeline processor acting as an interface between the camera and computer, to calculate the position and implement a control strategy, and d.c. stepping motors to convert an electronic signal to angular velocities of the four rollers. The control objective is to keep the centre of mass of the drop/particle at the centre of the region between the rollers where there is a stagnation point in the undisturbed flow, while maintaining the shear-rate and the ratio of vorticity to strain rate in the flow at fixed values. The resulting system is suitable for studies of: the rotational motions of single solid particles; the deformation and burst of single droplets; or the hydrodynamic interactions of two particles or drops, one of which is held with its centre-of-mass fixed at the stagnation point of the undisturbed flow. In all cases, the flow can be varied from pure rotation to pure strain, and the shear rate can be either steady or changing as a prescribed function of time.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 167 , June 1986 , pp. 219 - 240
Copyright
© 1986 Cambridge University Press

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