PocketFlow vs Navier Stokes Explained

Real water, live on your iPhone. Free to try for 7 days, then one purchase unlocks it for good. Draw a shape with your finger or build one in 3D, and watch water pour over, under and around it as it happens. PocketFlow runs a real free-surface water simulation on your phone's GPU. It isn't an animation: every frame is solved by our own solver, so the water splashes, jumps and settles because the physics says so. NEW IN 3.3 Feel and hear the water: haptics and sound follow the flow as it surges and hits the walls, then ease to a steady hum once it settles, each with a one-tap button. Spray and thin water look lifelike. Plot any 3D section and share it. Import a model at Actual size, and Add and fit tank grows the tank around it. Heights read as real-world elevations, in tanks from 1 cm to 10 km. BRING YOUR OWN MODEL (STL) Import a CAD or 3D-print model from Build, Files, Mail or AirDrop, at Actual size or at a scale you choose. Models move, turn, size, snap and duplicate like any shape, can poke through the walls and floor, and can have up to a million triangles. TWO WAYS TO PLAY • 2D Sketch: a side view of a tank. Draw solids right in the water with a pen, box or oval, and the flow reacts straight away. Press and hold a solid to duplicate it, cut it out or size it exactly, with undo, redo and snap guides. • 3D Build: add boxes, spheres and cylinders. Slide them with an axis lock, size any side, turn about any axis, or type exact numbers. SLICE 3D INTO 2D Cut any 3D scene along or across the flow and open the slice in 2D, at full size or as a scale model such as 1:15. START FROM A TEMPLATE Press ▶ to run any template. • 2D: Open channel, Dam break, Sluice gate, Weir • 3D: Channel + pier, Weir, Dam break, Labyrinth weir, Dam & stilling basin, and Mystery dam: an STL dam, spillway and stilling basin at 1:100 SET THE SIDES Make each side a wall or open to the air. Add an inlet by velocity or by flow rate, or hold a side at a water level, with or without inflow. Drag any side to size the tank, set up to eight blocks of starting water, or start empty. SEE WHAT'S GOING ON • Show plain water, or color it by velocity or pressure • Section view in 3D cuts the tank open to show the flow inside, and an Ortho view gives true elevations and plans • Plot along the cut: water surface, bed, velocity and bed pressure Drag to read values; share as a picture or data. Bridges and culverts are drawn as they are, even running full • Tap any solid to read its elevation • Section and level probes in 2D • Stretch the height or mirror the 2D view for long, flat channels • Probe pins with live velocity, depth and Froude readouts • Streamlines that follow the flow • A measure ruler that snaps to walls and edges • Live In and Out, with a Filling or Steady cue TILT TO SLOSH Tap Tilt and tip your phone. The water runs to the low side, like a real tank in your hands. THINK FULL SIZE Working with a scale model? Pick a scale such as 1:25 and every number shows at full size, scaled by Froude similarity. TRACE OVER A PHOTO In 2D, add a photo or drawing as a background, set it to true size from a known length, and draw your solids over it. SHARE IT Save or send a photo with the color scale on it, or a 10-second clip. EASY TO PICK UP A seven-step Quick start shows you where to press. Scenes save themselves, Continue picks up where you left off, and Fast, Balanced and Detailed presets trade speed for detail. GOOD TO KNOW • Runs fully on the device: no account, no ads, no tracking, works offline • One purchase after the 7-day trial, no subscription. Bought PocketFlow before? You're already unlocked. • Made for learning, exploring and quick what-ifs. It is real physics, but not a certified engineering design tool: check real designs with proper engineering analysis. Great for students and teachers, engineers who want a quick feel for a flow, and anyone who likes watching water.

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.