M. Whittle, R. J. Atkin, and W. A. Bullough :  J. of Non Newtonian Fluid Mechanics, 57, 61-81, (1995).

Fluid Dynamic Limitations to the Performance of an Electrorheological Clutch.

Abstract

We examine flow in a cylindrical electro-rheological clutch and discuss the fluid dynamic and inertial effects which limit the speed of operation.  Time dependent solutions of the equation of motion are developed in which the fluid is treated as a homogeneous continuum obeying the Bingham plastic constitutive equation.  Some approximations have to be made but the results give a good description of flow in clutches of practical dimensions.   The problem is also approached in an entirely different way by direct numerical integration using a time dependent version of the Bingham model and the results of the two methods are in in agreement. The results show that fluid dynamics places an upper limit on the acceleration of the output rotor.  This is only reached if very low moment of inertia rotors are used, otherwise the output hardware inertia is the limiting factor. Design formulae are developed to give a rough estimate for the fluid limited acceleration and to define the minimum output moment of inertia that can usefully be employed to give maximum available acceleration.

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