Reverse flow phenomena of a polyacrylamide solution in a channel with an obstacle at the entry : influence of obstruction geometry

This study investigates the reverse-flow phenomena of a polyacrylamide solution in a channel referred to as a “test channel” with obstruction geometry at the entry placed in another wider parallel-walled channel. The influence of various obstruction geometries (i.e., shapes and sizes) plays a very important role in controlling reverse-flow behavior and is investigated in this study. The obstruction geometries used in this research were: flat plate, semicircle, circle, triangle, and rectangle with various aspect ratios. Experimental investigation and numerical simulations were carried out with a non-Newtonian 0.03% (by weight) polyacrylamide solution that obeys a power-law behavior for a fixed Reynolds number of 2000. The non-Newtonian fluid results are compared with that of water. The flat plate produced the maximum reverse flow at a gap-to-width (g/w) ratio of 1, whereas the triangle produced minimum reverse flow at a g/w ratio of 0.5. The circular geometry produced the maximum forward flow, and the flat plate produced the minimum forward flow at a g/w ratio of 8. Good agreement has been observed between the experimental results and numerical simulations.