Experimental study of reverse flow in a channel without obstruction at the entry

It is known that reverse flow (i.e., flow in the direction opposite to the free stream direction) occurs when an obstruction is placed near the entry to a channel (referred to as the test channel), kept inside another wider channel. The present investigation is focused on realizing a reverse flow in the test channel without an obstruction placed at the entry. Experiments in the water channel have been carried out along with flow visualization. The initial investigation revealed that reverse flow even in the absence of an obstruction would occur in a situation where the two walls, forming the channel have a stagger with respect to each other and are kept at an angle of attack. Studies have been carried out for different widths (i.e., gaps between the two walls forming the channel), stagger (i.e., perpendicular distance between the leading edges of the side walls), and angles of attack. It is found that both the stagger and the angle of attack are needed for reverse flow to occur. The critical angle of attack at which the reverse flow begins depends on the stagger and channel width.