Spreading of a Herschel-Bulkley fluid using lubrication approximation

In this work the flow of 1.5% Carbopol-940 solution was studied as it was transported through a wedge-like system at different angles, entrance heights, exit heights, and velocities. The high-speed video recordings of the flow were processed by tracking air bubbles entrapped in the solution. This data was used to find the velocity field of the solution beneath the wedge. Also, the force imposed by the solution on the inclined top plate of the wedge was measured. The theoretical description in the framework of the lubrication approximation for Newtonian fluids was used for comparison to the experimental results. It was found that Herschel-Bulkley fluids exhibit qualitatively similar behavior to the Newtonian fluid, such as the reverse flow near the top of the wedge. Overall, this work proves that the lubrication approximation can be effectively used to characterize the flow field of non-Newtonian Herschel-Bulkley fluids at the wedge angles at least up to 20 degrees.