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NaSty - CFD App Development

A real time full Navier-Stokes educational app on Apple Devices.

NaSty provides a single-phase flow Navier-Stokes solver for two dimensional fluid simulations. Finite differences on a staggered grid with Chorin’s projection approach are used to discretise the Navier-Stokes equations. To solve the resulting Poisson equation a SOR iterative solver is used, which enforces incompressibility of computed fluid. Including complex geometries and particle transport NaSty provides all possibilities to visualize fluid flow around obstacles in two dimensions.

NaSty - CFD App is available in Appstore : NaSty - CFD APP in AppStore

Some InApp Screenshots on iPhone:

Further information about NaSty’s bigger brother NaSt3DGPF can be found here
  • M. Griebel, T. Dornseifer, and T. Neunhoeffer. Numerical Simulation in Fluid Dynamics, a Practical Introduction. SIAM, Philadelphia, 1998.
  • R. Croce, M. Griebel, and M. A. Schweitzer. Numerical Simulation of Bubble and Droplet-Deformation by a Level Set Approach with Surface Tension in Three Dimensions. International Journal for Numerical Methods in Fluids, 62(9):963-993, 2009.


Building a scenario

  • put or remove obstacles: tap in fluid box while pausing
  • bad obstacles: automatic checking and removing of obstacles with two opposing fluid cell neighbors causing wrong boundary conditions for the Poisson solver
  • obstacle boundary conditions: selectable in the options menu
  • wall boundary conditions: wall-buttons for each border: “wall” for an adhering wall, “slip” for a slippery wall, “outflow” for an outlet, “inflow” for an inlet
  • manipulate fluid velocity: swipe in fluid box while playing
  • save own scenarios in the save menu
  • load saved scenarios or standard examples in the load menu


  • play/pause-button: start and pause flow
  • stop-button: stop flow and erase floaters
  • restart-button: stop flow and erase floaters and obstacles

Visualization of flow

  • random: floaters emerging at random
  • line: floaters streaming in a line
  • static: stationary floaters, aligned along flow direction