GATE 2018 ME (ME2) – Question 32
A laminar boundary layer forms over a flat plate in viscous air flow. Its thickness at length L is $\delta_1$. If plate length doubles, find the percentage increase in end thickness relative to $\delta_1$, to two decimal places.
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Correct answer: 41.30 to 41.50
Explanation
At fixed external velocity and viscosity, laminar flat-plate thickness scales as $\delta(x)\propto\sqrt{x}$. Therefore $\delta(2L)/\delta(L)=\sqrt2$. Percentage increase is $100(\sqrt2-1)=$ **41.42%**.