In order to develop a practical modern numerical simulation system, an efficient Navier-Stokes solver, developed as a general-purpose program, has been systematically connected with the Solution-Adaptive-Grid program, a grid generation program and some post processing programs of computational results. The most attractive feature of this simple system is that grid redistribution is accomplished according to the physical phenomena of each problem. It significantly helps to improve the accuracy and quality of numerical results. Through several flow problems, this tiny system has been shown to work effectively.