In a laminar boundary layer, the ratio of boundary layer thickness (\( \delta \)) to the corresponding displacement thickness (\( \delta^* \)) lies between ________.
Show Hint
- 1.5 and 2.4
- 2.5 and 3.4
- 3.5 and 4.4
- 4.5 and 5.4
The Correct Option is B
Solution and Explanation
Step 1: Definition of boundary layer and displacement thickness.
The boundary layer thickness (\( \delta \)) is the distance from the surface where the velocity reaches a specified value (typically 99% of the free-stream velocity). The displacement thickness (\( \delta^* \)) accounts for the reduction in mass flow due to the velocity profile in the boundary layer.
Step 2: Analyze each option.
(A) Incorrect. The ratio is generally higher than this range in a laminar boundary layer.
(B) Correct. In a laminar boundary layer, the ratio of \( \delta \) to \( \delta^* \) typically lies between 2.5 and 3.4.
(C) Incorrect. The ratio tends to be lower than this value.
(D) Incorrect. This ratio is generally not in this higher range.
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