Flow phenomena in a channel with different shaped obstructions at the entrance

The flow in a channel, when obstructed with a geometry at the entry, can be forward, reverse or stagnant depending on the position of the obstruction. There are several parameters that influence the flow inside and around the test channel. The most dominant parameters that influence the flow phenomena are the shapes and sizes ofobstruction geometry and the gap (g) between the obstruction and the entry ofthe test channel. Influence of these flow parameters were investigated using velocity measurement and flow visualization images. The velocity measurement and the flow visualization provided the quantitative and qualitative information, respectively. The velocity measurements were carried out for different shapes of obstruction geometries at a fixed velocity of 0.24 m/s which is equivalent to a Reynolds number of6000. The flat plate produced the maximum reverse flow reaching 20% of the incoming channel velocity, while the circular geometry produced the minimum reverse flow. However, the circular geometry produced the maximum forward flow equal to 90% of the incoming velocity while the flat plate produced the minimum forward flow. For a rectangular shaped obstruction, it was found that the shorter after-body length (l/b = 0.32) produced the maximum reverse flow. The influence ofthe gap on the velocity ratio was also investigated for flat plate obstruction geometry and is presented here. The flow visualization pictures showing the flow pattern inside and around the test channel are also presented and discussed.