streakline · a wind tunnel in the browser

Draw walls Erase

Drag across the tunnel to draw walls; hold Shift to erase. Space pauses, R restarts, V cycles the view.

Obstacle

Shape Profile Angle Size

The size is the diameter, side, plate length or chord, in lattice cells, and it is the length in the Reynolds number. A positive angle raises the leading edge.

Flow

Reynolds number Inflow speed Grid

Running at: –
Relaxation τ: –
Lattice Mach: –
Flow time: –

Re = U D / ν. The viscosity ν sets how fast the lattice relaxes; below τ = 0.51 the scheme goes unstable, so a Reynolds number too high for the obstacle size is capped there. A larger obstacle or a faster inflow reaches higher.

Forces on the obstacle

drag C_d lift C_l, over the last 40 D/U

Mean drag C_d: –
Lift swing: –
Shedding period: –
Strouhal number: –

Forces come from the momentum the fluid hands the obstacle as it bounces off. Coefficients divide by ρU²D/2; the Strouhal number St = f D / U is the shedding frequency in flow units, read from the lift's swings and averaged over whole periods.

Scenes

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