Pixel Wind Tunnel vs Navier Stokes Explained

Draw a shape. Tap Simulate. Watch real fluid dynamics come alive in pixels. Pixel Wind Tunnel is a 2D fluid simulation app that runs real CFD (Computational Fluid Dynamics) calculations right on your device. No simplified approximations — the app solves the incompressible Navier-Stokes equations using the CIP advection method and Pressure Poisson solver, the same mathematical framework used in professional engineering software. HOW IT WORKS Draw any shape with your finger — airfoils, cars, buildings, anything Tap Simulate Watch the flow develop in real time That's it. Real fluid physics in three steps. SEE THE FLOW Switch between visualization modes to explore different aspects of the physics: • Velocity — where the flow speeds up and slows down • Pressure — high and low pressure regions around your shape • Vorticity — spinning structures and vortex shedding • Streamlines — paths that fluid particles follow MEASURE PERFORMANCE Real-time aerodynamic coefficients calculated from surface pressure and viscous stress integration: • Drag coefficient (Cd) • Lift coefficient (Cl) • Reynolds number Draw two different shapes and compare which one has less drag. Understand why streamlined shapes work better — with real numbers, not guesswork. EXPLORE DEEPER • Place point probes anywhere to track velocity and pressure over time • Scrub through simulation history with the timeline slider • Adjust inlet velocity and viscosity to change flow conditions • Save shapes with screenshots and reload them anytime REAL CALCULATION, NOT AN ANIMATION Every frame you see is computed from the actual Navier-Stokes equations. The CIP (Cubic Interpolated Propagation) method handles advection with minimal numerical diffusion, while the SOR iterative solver resolves the pressure field. Boundary conditions, viscous forces, and flow separation are all physically modeled. FOR CURIOUS MINDS Whether you're a student studying fluid mechanics, an engineer sketching quick ideas, a teacher demonstrating aerodynamics in class, or simply someone who wonders why things are shaped the way they are — draw it and find out.

The Navier-Stokes equations describe how every liquid and gas moves. They are usually met as a wall of symbols. Here they are a tank of water you can hold. A real three-dimensional fluid solver runs on your iPhone's GPU. Drop a column of water, stir a tank, push a flow past a sphere, or turn on Tilt and let gravity follow your phone. Then look inside: color the water by speed, pressure or rotation, tap anywhere to measure it, and open the live values to see each term of the equation as an arrow at that point. In still water the pressure arrow and the gravity arrow cancel, which is what the equation says they must do. FOUR GUIDED LESSONS Predict, watch, compare, explain. • Why does a swirl fade? The same stir in two liquids, 10,000 times apart in viscosity. • What holds water up? Measure pressure at two depths. • How does flow turn? A pulse of water meets a solid sphere. • Why doesn't water squash? The same falling column with pressure switched off. A LAB, NOT A VIDEO • Gravity, viscosity and stirring strength are yours to change, with a live Reynolds number. • Velocity and pressure arrows, tracer trails, pause, single-step and half speed. • Every term of the equation opens a plain-language explanation and an experiment to try. • Works offline. No account.