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Almost a hundred years ago, Osborne Reynolds carried out a simple experiment. He filled a leather bag with marbles, topped it with water and then twisted it, thereby inducing a shear. The water level drops because the close packing of the marbles is disrupted as layers of marbles slide over each other during the twisting motion; as a result the marbles are further apart on average, creating space that the water has to fill.
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Evans et al. (1984) studied this question.
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