Flag: A free-Lagrange method for numerically simulating hydrodynamic flows in two dimensions

The FLAG concept applies to both compressible and incompressible fluid motions. We consider an incompressible, inviscid form of the equations of motion with streamfunction and vorticity as dependent variables. Incompressible, inviscid calculations give qualitative verification of a vorticity cascade toward higher wavenumbers and an energy cascade into lower wavenumbers currently postulated for two-dimensional hydrodynamic motions.