On the Torque and Energy Balances for the Flow Between E(ccentric) R(otating) D(iscs)
Rheometrical flow systems in which a small perturbation is superimposed on a rigid rotation have been the subject of considerable interest in recent years, both from the experimental and theoretical points of view. Yet there are some problems with respect to the flow field in these rheometers which are not satisfactorily solved. This paper will mainly deal with the orthogonal rheometer, but similar problems arise with other rheometers based on the same principle. The velocity field in ERD flow as realized in the orthogonal rheometer was first proposed by Blyler and Kurtz1. It was shown, however, that this velocity field leads to some fundamental problems. First of all there is the so-called “stress power paradox”2,3, expressing the paradoxal observation that, although energy is dissipated in the sample, no power seems to enter into it from the apparatus. In the second place it was pointed out4,5 that the total torque acting on the sample differs from zero. This led these authors to the assumption that a torsional flow was superimposed on the primarily assumed flow. Finally, the stress field resulting from the proposed flow field1, also when an additional torsional flow field is superimposed on it, does not obey the boundary conditions at the free edge. In order to overcome this latter difficulty it was assumed4 that there is an edge zone in which the flow field is not of the form postulated.
KeywordsFlow Field Free Edge Ball Bearing Lower Plate Rigid Rotation
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