A calculation technique using overset grid coordinate system has many benefits on airflow analysis around buildings, especially when the buildings have complicated configurations. In this research work, a fundamental calculation algorithm for incomppressible viscous flow was studied and a 2-dimensional test program was developed using SIMPLE algorithm and fortified solution method. As the result of test solutions, it was found that this program enabled steady and time-marching calculations for incompressible viscous flow using plural grid coordinate systems.
