Fluid Mechanics and Hydraulic Machinery Miscellaneous
 An incompressible fluid flows over a flat plate with zero pressure gradient. The boundary layer thickness is 1 mm at a location where the Reynolds number is 1000. If the velocity of the fluid alone is increased by a factor of 4, then the boundary layer thickness at the same location, in mm will be

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Boundary layer thickness, δ ∝ 1 √Re Re ∝ V ⇒ δ ∝ 1 √V
Correct Option: C
Boundary layer thickness, δ ∝ 1 √Re Re ∝ V ⇒ δ ∝ 1 √V
 Consider an incompressible laminar boundary layer flow over a flat plate of length L, aligned with the direction of an incoming uniform free stream. If F is the ratio of the drag force on the front half of the plate to the drag force on the rear half, then

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NA
Correct Option: D
NA
 For air flow over a flat plate, velocity (U) and boundary layer thickness (δ) can be expressed respectively, as
If the free stream velocity is 2 m/s, and air has kinematic viscosity of 1.5 × 10^{5} m^{2}/s and density of 1.23 kg/m^{3}, the wall shear stress at x = 1 m, is

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NA
Correct Option: C
NA
 If x is the distance measured from the leading edge of a flat plate, then laminar boundary layer thickness varies as

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ρ = 5x for laminar flow √Re Re_{x} = Vx υ ∴ ρ = 5√x for laminar flow √V / υ
∴ ρ ∝ √x
Correct Option: D
ρ = 5x for laminar flow √Re Re_{x} = Vx υ ∴ ρ = 5√x for laminar flow √V / υ
∴ ρ ∝ √x
 Flow separations flow past a solid object is caused by

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NA
Correct Option: C
NA