Experimental study of stationary inertial flows of a yield-stress fluid around a cylinder

Non-recirculating and recirculating inertial flows of an elasto-viscoplastic yield stress fluid (Carbopol® gel) around a cylinder were studied experimentally. The experimental set-up that was designed and built was validated by studying the flow of a Newtonian fluid. Appropriate procedures were introduced for yield stress fluids. Changes in the morphology of the flow behind the cylinder were studied for Oldroyd numbers between 0 and 0.5 and Reynolds numbers between 10 and 100. The characteristic lengths of the flow and the separation angle of the streamlines were determined. They were compared with the numerical predictions for a Herschel–Bulkley viscoplastic fluid. The limits between the different flow regimes were determined experimentally and compared with the numerical results. The influence of the boundary conditions, and in particular slip on the cylinder, were also evaluated experimentally.

► We study the inertial flow of a yield stress fluid around a cylinder. ► Experimental data are compared with the numerical data for a viscoplastic fluid. ► The limits between non-recirculating and recirculating flows are determined. ► The influence of the slip at the wall is evaluated experimentally.