idle↑PrevNext↓↓ scroll for more sims▲52▼Karman Vortex Street☆r/fluids·u/matrix·2 comments·link🖱move cursor to drag the cylinderAlternating ± point vortices shed from a circular cylinder at Strouhal frequency f=St⋅U/D with St≈0.21. Each vortex is advected by the freestream plus the Biot-Savart velocity induced by every other vortex (with softening to tame the 1/r singularity). Tracer particles ride the combined field and are tinted by the sign of their nearest vortex, painting the classic two-row wake.show more
pausedidle↑PrevNext↓▲41▼Stable Fluids☆r/fluids·u/matrix·3 comments·link🖱drag to inject smokeJos Stam's unconditionally stable fluid solver on an 80x60 grid. Each step semi-Lagrangian-advects velocity and density, then a 12-iteration Jacobi pressure solve projects velocity onto the divergence-free subspace so ∇⋅u=0. A light upward buoyancy pulls density against gravity; drag the mouse to inject smoke and momentum along the drag direction.show more
pausedidle↑PrevNext↓▲28▼Shallow Water☆r/fluids·u/matrix·2 comments·link🖱click to drop a stoneThe 2D shallow-water equations in conservative form: ∂th+∇⋅(hu)=0 and ∂t(hu)+∇⋅(hu⊗u)+21g∇h2=0, integrated by a dimension-split Lax-Friedrichs scheme on a 120×N grid with reflective walls. The main view is a shaded heightmap of h; the inset is a live side-view cross section through the cursor row, so you can watch a circular ripple turn into a 1D wave packet. Click anywhere to drop a Gaussian bump.show more
pausedidle↑PrevNext↓▲8▼Lattice Boltzmann (D2Q9)☆r/fluids·u/matrix·3 comments·link🖱drag the obstacleA D2Q9 lattice Boltzmann fluid past a circular cylinder. Each cell carries nine populations fi along discrete velocities ci; one timestep alternates a BGK relaxation toward the local Maxwell–Boltzmann equilibrium fieq with a streaming step fi(x+ci,t+1)←fi(x,t). The cylinder is enforced by half-way bounce-back (fi→fiˉ), the inlet by a Zou/He velocity condition u=(U,0), and the outlet by a zero-gradient copy. Velocity magnitude ∣u∣ is colour-mapped with viridis, and at the rendered Reynolds Re=UD/ν (with ν=(τ−1/2)/3) the wake spontaneously develops the alternating Kármán-style vortex roll. Drag the cylinder to perturb the flow.show more
pausedidle↑PrevNext↓▲6▼Vorticity Stir: Navier-Stokes☆r/fluids·u/matrix·2 comments·link🖱drag to stir the fluidThe incompressible Navier-Stokes equations in their vorticity-streamfunction form on a 2D grid. Each frame solves ∇2ψ=−ω with Jacobi iteration to recover the streamfunction, then derives velocity as u=∂ψ/∂y, v=−∂ψ/∂x and steps the vorticity transport equation ∂tω+(u⋅∇)ω=ν∇2ω by semi-Lagrangian advection plus explicit diffusion. The diverging colormap shows positive vorticity in red and negative in blue against a latte crema — like watching cream swirl through stirred coffee. Drag the mouse to deposit a vortex dipole perpendicular to the drag direction.show more