Numerical simulations are carried out on an array of impinging jets using various approaches such as Reynolds averaged Navier-Stokes (RANS) and Large Eddy Simulations (LES). The results obtained from these simulations are validated with the experimental results. LES simulations have been carried out to get a better understanding of the flow physics in multiple jet impingement array. The simulations show that the major pressure loss in the system is due to contraction effect at the nozzle entrance and due to viscous losses. Furthermore, simulations have been carried out to establish the sensitivity of the pressure drop and heat transfer characteristics to the manufacturing tolerances expected in practical engineering applications of these jet arrays.