NASA Technical Paper 3496

A methodology is described for computing viscous flows of air and sulfur hexafluoride (SF 6 ). The basis of the method is an existing flow solver that calculates turbulent flows in two dimensions on unstructured triangular meshes. The solver has been modified to incorporate the thermodynamic model for SF 6 and used to calculate the viscous flow over two multielement airfoils that have been tested in a wind tunnel with air as the test medium. Flows of both air and SF 6 at a free-stream Mach number of 0.2 and a Reynolds number of 9 × 10 6 are computed for a range of angles of attack corresponding to the wind-tunnel test. The computations are used to investigate the suitability of SF 6 as a test medium in wind tunnels and are a follow-on to previous computations for single-element airfoils. Surface-pressure, lift, and drag coefficients are compared with experimental data. The effects of a heavy gas on the details of the flow are investigated based on computed boundary-layer and skin-fri..