Physics
2D fluid (LBM)
Flow past a cylinder: the Kármán vortex street.
What happens
Fluid flows through a channel around whatever stands in its way: behind a cylinder the wake goes unstable and sheds the famous Karman vortex street. Draw your own obstacles with the left mouse button, erase with the right, inject dye stripes, and switch the view between dye, speed and vorticity. The room presets look down on a flat in the wind - walls, a sofa, a table, a wardrobe - and start it full of stale air: with a window in the windward wall and another in the leeward one the wind flushes it, with both windows on one side it barely does; the chart counts the stale air left.
Equations used in the module
Equations BGK: f_i(x+c_iΔt,t+Δt) = f_i − (f_i−f_i^eq)/τ + F_i f_i^eq = w_iρ[1+3c_i·u+4.5(c_i·u)²−1.5u²] ν = (τ−½)/3; Re = UD/ν; St = fD/U
