Flow in a channel with obstruction geometry at the entry placed in another wider parallel walled channel could be reverse, stagnant or forward depending on the position of the obstruction geometry. Various parameters that influence the flow inside and around the test channel are: size and shape of the obstruction geometries, gap between the test channel and the obstruction geometry, and Reynolds number. The influence of these parameters on the magnitude of the velocity ratio, Vi/Vo (inside/outside velocity of the test channel) is investigated in this study. Semicircle, circle, triangles and various shapes of rectangles were used as the obstruction geometries. A mixed solution was used for the detailed investigation of the flow phenomena and its results are compared with that of a polyacrylamide solution and water. The experimental investigations include velocity measurement and flow visualization of the two non-Newtonian fluids (mixed solution and polyacrylamide solution) and Newtonian fluid (water). The two non-Newtonian fluids have the same viscosity but show a slightly different elasticity and they follow a power-law model. The numerical simulations of the flow of the mixed solution were also carried out using the CFD-ACE+ software.The results show that the flat plate obstruction geometry produce the maximum reverse flow and it occurs at a gap to width (g/w) ratio of 1.0 for non-Newtonian fluids, and at g/w ratio of 1.5 for water. The numerical simulations show that the predicted streamlines and velocity vectors of the flow phenomena are in good agreement with the streak lines of the flow visualization images.