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 δ_L. 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 δ_L) 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

                                                        δ_L ∝ √L

                                                        δ_2L ∝ √(2L)

                                                        (δ_{2L -}δ_L)*100/δ_L= [(√(2L) - √L)/√L]*100

                                                                                   = (√2 -1) *100 = 41.42%