Question
The viscous laminar flow of air over a flat plate results in the formation of a boundary layer. The boundary layer thickness at the end of the plate of length L is δL. When the plate length is increased to twice its original length, the percentage change in laminar boundary layer thickness at the end of the plate (with respect to δL) is ________ (correct to two decimal places).
Answer :
41.42%
For laminar flow over flat plate,
As per Blasius equation,
δ = 5x/√(ρV∞x/µ)
δ ∝ √x
δL ∝ √L
δ2L ∝ √(2L)
(δ2L -δL)*100/δL= [(√(2L) - √L)/√L]*100
= (√2 -1) *100 = 41.42%
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