Flow-Over-a-Surface Transition (2D) — Boundary-Layer Reynolds Simulator

Re 0

x_tr —

LAMINAR

Flow speed U 1.0 m/s

Viscosity ν 15 ×10⁻⁶ m²/s

Length scale L 2.0 m

Particle count 220

Reynolds Re = UL/ν0

RegimeLaminar

Transition x—

Turbulence intensity0%

Local Reynolds number: Re_x = Ux/ν
Flow starts laminar at the leading edge. As distance x downstream grows, Re_x rises; past the critical threshold (Re_x ≈ 3×10⁵–5×10⁵, the standard flat-plate / open-channel value) the boundary layer trips into turbulence: point-vortex shedding perturbs the streamlines into chaotic eddies. Below Re_x ≈ 3×10⁵ the flow keeps a smooth Blasius profile; above ≈5×10⁵ it is fully turbulent (1/7-power profile).