Experiments on the 2D flow of a grain-water mixture past a circular cylinder

We present experiments with a mixture of grains and water around a circular cylinder. Flow is driven by the internal cylinder of a Taylor–Couette cell. Velocity measurements of the mixture at the external surface are carried out using a commercial particle image velocimeter. The flow regime is in the macroviscous range and the flow field is similar to that generated by a Newtonian fluid around a circular cylinder, with a wake and a recirculation zone. Like in other granular flows, the velocity covariance tensor and the rate of deformation tensor are not collinear; they have principal axes rotated nearly 45°. Near the body, the velocity scale of the wake decays linearly at high Reynolds numbers and logarithmically at low Reynolds numbers. The transverse length scale increases as x′^n (x′ measured along the axis of symmetry with the origin at the boundary of the body) with n<0.5 (or nearly zero in some flow conditions).