“…Our experiments have been done with three different values of h: 52, 78 and 100 m. Then, at the rim, the gap is, respectively, 637, 663 and 685 m. When the gap vary, one has to consider the offset cone and plate (ocp) geometry equations. They have initially been described by Jackson and Kaye [23] for the measurement of normal stresses and then also discussed by Ohl and Gleissle [24]. The shear rate varies within the gap.…”