Consider steady, laminar flow of an incompressible fluid with zero pressure gradient over a thin horizontal flat plate of length 2 m, free stream velocity 1 m s⁻¹. A boundary layer thickness of 1 mm is observed at 0.25 m from the leading edge. At 1 m from the leading edge, the boundary layer thickness (in mm) is _________ (rounded off to the nearest integer).

Question

Accepted Answer

The correct answer is 2. GATE 2026 official key: 2. For a laminar boundary layer, δ ∝ √x, so δ(1 m) = δ(0.25 m) × √(1/0.25) = 1 mm × 2 = 2 mm.