Boundary Layer Theory MCQ with answer and solution

Concept

Laminar Boundary Layer Velocity Profile

Formula

u/U = 2(y/δ) - (y/δ)²

Step-by-step solution

1. Identify the given velocity profile formula: u/U = 2(y/δ) - (y/δ)². 2. Observe the variable terms: (y/δ) is raised to the maximum power of 2. 3. Conclude that a second-degree polynomial equation represents a parabolic curve.

Explanation

In a laminar boundary layer over a flat plate, fluid viscous forces dominate, causing the velocity to smoothly increase from zero at the wall to maximum velocity at the outer edge, which closely follows a parabolic curve.

Shortcut

Remember: Laminar Plate = Like a Parabola (LP), or recall that the formula for laminar boundary velocity profile is a second-degree polynomial (y²), which is a Parabolic curve.

Common mistake

Students often select the logarithmic profile by confusing the laminar boundary layer profile with the turbulent boundary layer velocity profile (log law), or they choose a linear profile by oversimplifying the velocity gradient near the wall.