Three-dimensional Navier-Stokes numerical simulations are necessary to correctly predict the complex lee- ward-side flow characteristics over delta wings, including leading-edge separation, secondary separation, and vortex breakdown. This article presents Navier-Stokes solutions of subsonic vortical flow over a 75-deg sweep delta wing with a sharp leading edge. The sensitivity of the solution to the numerical scheme is examined using both a partially upwind scheme and a central-differencing scheme. The effect of numerical grid density is also investigated. An embedded grid approach is implemented to enable higher resolution in selected isolated flow regions, such as the leeward-side surface flow region, and the leading-edge vortical flow region. HE main feature of the flow over delta wings at an angle of attack is the separated flow along the leading edges, which form free shear layers rolling up around cores to form leading-edge vortices. The leading-edge vortices induce ad- ditional nonlinear lift, usually called vortex-induced lift. In- crease in the angle of attack strengthens the vortices until eventually a sudden change occurs in the nature of the cores. This sudden change is known as vortex breakdown. In this article vortical flowfields, with and without vortex break- down, over highly-swept sharp-edged delta wings are inves- tigated. Due to its importance to aerodynamics, the vortex break- down over delta wings was explored in early experimental studies.1'2 Vortex breakdown was studied in controlled ex- periments on axisymmetric cylindrical vortices generated in confined tubes.3~6 Three types of vortex breakdown were ob- served for a cylindrical vortex,3 namely bubble breakdown, spiral breakdown, and double helix breakdown. Changes in the pressure gradient were found to have significant effects, thus a pressure increase downstream drives the breakdown upstream. For flows over delta wings, bubble and spiral breakdown are encountered, depending on the angle of incidence and the sweep angle. Experimental studies of flows over a unity aspect ratio delta wing7 show that as the angle of attack increases, bubble-type breakdown precedes spiral-type vortex break- down. The large suction pressure of the leading-edge vortex is diminished when vortex breakdown occurs with a subse- quent loss of lift and nose-up pitching moment. After vortex breakdown, the vortex core is not re-established and the downstream end of the bubble usually is followed by a tur- bulent wake. Experimental studies8-9 for flows over delta wings included surface and flowfield velocity and pressure measurements.