UNCLE is a two/three-dimensional, finite-volume, unstructured incompressible Navier-Stokes solver for steady and unsteady flow fields. UNCLE relies on a cell-centered pressure-based method that is based on the SIMPLE algorithm with second order accuracy in both time and space. In order to compute numerical flux on interfaces, a second order upwind scheme is adopted to compute advection terms and second order central difference scheme is used for diffusion terms. A collocated grid system with the Rhie and Chow momentum interpolation method is employed to avoid the checkerboard solution of the pressure based scheme. Fluxes on the volume faces are determined through interpolation of cell-centered values. The time discretization is second-order fully implicit scheme.