Predicting Unsteady Flow Parameters in a Subsonic Air Diffuser Using MacCormack’s Explicit Method


A numerical procedure is presented to predict the flow characteristics inside a subsonic diffuser by solving Navier-Stokes' equations, using MacCormack’s explicit method. The flow is assumed to be viscous, compressible, unsteady and two-dimensional. The grid model suggested for the diffuser has 20 points in the horizontal direction and 30 points in the vertical direction. The numerical solution has shown reasonable results with a 2D variation of flow properties inside the diffuser and the steady state solution can be satisfied by 600-900 loops only. The obtained results of the present study are compared with those obtained by using a numerical code of National Project for Application-oriented Research in CFD (NPARC) as well as those obtained from a previous experimental study and give an acceptable range of errors (about ± 15%).