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Subway Tunnel Piston Effect: Continuity & Bernoulli Flow (2D)

2D tunnel-aerodynamics lab: a train moving through a fixed-area tunnel forces air through the annular gap around it — continuity and Bernoulli give the bypass velocity, piston-effect pressure rise and drag power in real time.

Everyday Physics2DModerate60 FPS📱 Mobile-adapted⇄ 3D version

This 2D companion isolates the real fluid mechanics behind the 3D tunnel ride: a train modelled as a moving blockage inside a fixed-area tunnel, with the annular gap around it computed from the continuity equation and the resulting pressure field from Bernoulli's principle plus a Darcy-Weisbach friction term. Sliders for train speed, blockage ratio, friction loss and air density drive a live particle flow field and pressure strip, with a numeric readout panel for gap velocity, piston-effect and friction pressure, drag power and the gap's Reynolds number — the same "tunnel piston effect" that real metro systems design ventilation shafts around.

⚙ Under the hood

2D tunnel-piston-effect lab: continuity equation gives the annular bypass velocity around a moving train, Bernoulli plus a Darcy-Weisbach friction term give the pressure field, and the readout panel reports gap velocity, pressure rise, drag power and Reynolds number in real time.

tunnel aerodynamicspiston effectcontinuity equationbernoulli principlefluid flowpressure

2D · HTML5 Canvas 2D · 60 FPS target · runs fully client-side, no install