Implications of compressibility effects for Reynolds-scaled testing of an inverted wing in ground effect. (23rd February 2015)

• Record Type: Journal Article
• Authors: Doig, Graham; Barber, Tracie J.; Diasinos, Sammy
• Is Part Of: International journal of aerodynamics. Volume 4:Number 3/4(2014)
• Page Start: 135
• Page End: 153
• Publication Date: 2015-02-23
• Subjects: ground effect -- CFD -- compressible flow -- Reynolds-scaling -- inverted wing -- downforce; Aerodynamics -- Periodicals; 533.6205
• Languages: English
• ISSNs: 1743-5447

Abstract

The influence of compressibility around an isolated inverted wing at a fixed Reynolds number was examined as relevant to the issue of wind tunnel scaling effects. Three-dimensional simulations were conducted for low ground clearances, at: full scale and a Mach number of 0.088, at 50% scale at Mach 0.176, and at 25% scale at Mach 0.352. As the scale was reduced, the increasing peak local Mach number between the wing and the ground resulted in a higher propensity of the flow to separate towards the trailing edge, and for incompressible or full-scale CFD to underestimate the lift and drag coefficients by an ever-increasing margin. The lower vortex path was less affected. The results suggest that compressible CFD of a scale experiment ought to be conducted at the same Reynolds number and Mach number as the tunnel test for the best possible correlation at free-stream Mach numbers beyond 0.15.