Computational and experimental investigation was performed for an incompressible flow over an open cavity. A cavity of a unity length-to-depth ratio was considered at Mach number 0.1 and a moderate Reynolds number of 3.18x105 based on cavity depth. Different geometries of square and skewed cavities were taken in consideration to investigate their effect on the back flow pressure. The measurements were established for a two dimensional cavity in a wind tunnel of 30 m/s flow velocity corresponding to the considered Mach number. Both the pressure coefficient and the drag coefficient were estimated for the considered geometries. In addition, a numerical simulation of the cavity flow field was developed. A numerical solution of the Navier-Stocks equations was carried out for the incompressible two-dimensional and turbulent flow. The equations were descritized by a finite-element scheme using ANSYS 5.4 code. The flow was fully demonstrated over the cavities considered, acceptable agreement was obtained between the measured and numerical experiments. Moreover, it is found that the square cavity has a less pronounced effect on the back flow than other geometries. The results were verified with the corresponding published data.