Fast Euler and Navier-Stokes fluid flow simulation

Three m-files to realize easily simulations of fluid flow in a rectangular cavity.

Here are two examples of videos:
http://www.youtube.com/watch?v=rCxkKp8Ngw4
http://www.youtube.com/watch?v=9QJahw5tBV8
The colors show the vorticity of the flow.
Enter the command line:
simulation_euler_flow(l,L,lambda_max)
where L and l are the width and height of the box containing the fluid and lambda_max is an integer that will be used to determine the number of degrees of freedom (the larger it is, the better the simulation will be but the longer the computation will last). As a first guess, you can try : l = 4, L = 3 and lambda_max = 60.
Once the computation is done, enter:
film = graph_flow_euler
to make a Matlab movie.