Fluid Mechanics MCQ Questions & Answers | Chemical Engineering

Streamlines are lines that are tangent to the velocity vector of the flow at every point.

Option A is correct – Streamlines are always parallel to the direction of fluid flow.

Option B is correct – There is no flow across a streamline, making it similar to a rigid boundary in fluid analysis.

Option C is incorrect – Streamlines never intersect. If they did, it would imply two different velocity directions at the same point, which is physically impossible.

Option D is correct – The fluid between two streamlines behaves like an isolated streamtube, and the spacing between streamlines varies inversely with the velocity (closer spacing indicates higher velocity).

Correct Answer: Option C: Streamlines intersect at isolated point of zero velocity and infinite velocity

Hydraulic mean depth (D_m) is defined as the cross-sectional area of flow divided by the wetted perimeter.

For a circular pipe flowing full, D_m = 0.25 D, where D is the diameter of the pipe.

For a circular channel flowing partially, when D_m = 0.3 D, it represents the condition for maximum efficiency of flow.

At this condition, both the flow rate and the mean velocity are maximized, because the hydraulic radius is at its optimum value.

Therefore, the correct answer is Option C: Both A & B