Analysis of an Exact Fractional Step Method

An exact fractional step or projection method for solving the incompressible Navier–Stokes equations is analyzed. The method is applied to both structured and unstructured staggered mesh schemes. There are no splitting errors associated with the method; it satisfies the incompressibility condition to machine precision and reduces the number of unknowns. The exact projection technique is demonstrated on a two-dimensional cavity flow and a multiply connected moving domain with a free surface. Its performance is compared directly to classic fractional step methods and shown to be roughly twice as efficient. Boundary conditions and the relationship of the method to streamfunction-vorticity methods are discussed.