We present a method to combine fluid dynamics and image analysis into a single fast simulation environment. Our target applications are hemodynamic studies. Our method combines an NS solver that relies on the L 2 penalty approach pioneered by Caltagirone and co-workers, and a level set method based on the Mumford-Shah energy model. Working in Cartesian coordinates regardless of grid no matter the complexity of the geometry, one can use fast parallel domain decomposition solvers in a fairly robust and consistent way. The input of the simulation tool is a set of JPEG images, and the output can be various flow components as well as shear stress indicators on the vessel or domain wall. In two space dimensions the code runs close to real time.