Question

For a laminar boundary layer developing over a flat plate, the displacement thickness is defined as: $\delta^* = \int_0^\delta \left(1 - \frac{u}{\text{U}_\infty}\right) dy$. Physically, $\delta^*$ represents

• A. Momentum loss in the boundary layer
• B. Reduction in mass flow due to the presence of the boundary layer
• C. Energy lost in the boundary layer
• D. Vorticity in the flow

Hint:

Remember the physical definitions of boundary layer thicknesses:
Displacement thickness ($\delta^*$) $\rightarrow$ Mass flow rate deficit.
Momentum thickness ($\theta$) $\rightarrow$ Momentum flow rate deficit.
Energy thickness ($\delta^{**}$) $\rightarrow$ Kinetic energy flow rate deficit.

Answer 1

The Correct Option is B