When the hydrodynamic boundary layer thickness (δ), which is the distance from the surface at which the local velocity (u) reaches 99% of the free - stream velocity, which of the following equations is valid for laminar flow:
1
(δ / x) = 5 / (Rex)(1/2)
2
(δ / x) = 5 (Rex)(2)
3
(δ / x) = 10 / (Rex)(1/2)
4
(δ/ x) = 10 / (Rex)(2)