ANS:A - parabolic

For laminar flow in an open channel, the vertical velocity distribution is typically assumed to be parabolic. In laminar flow, the velocity distribution across the depth of the channel can be approximated by a parabolic profile. This means that the velocity is highest at the centerline of the channel and decreases gradually toward the bottom and top boundaries. The parabolic velocity distribution is a result of the balance between gravity and shear stresses within the fluid. The parabolic velocity profile is described by the following equation: u(y)=Bh4Q​(y−hy2​) Where:

• u(y) = velocity at a distance y from the channel bottom
• Q = flow rate
• B = width of the channel
• h = depth of the flow