ASSESSMENT OF THEORETICAL MODELS FOR VISCOUS AND TRANSONIC FLOW.
Some current and proposed methods of treating viscous and transonic effects in theoretical aerodynamic models suitable for aeroelastic applications are reviewed critically. Where possible, theoretical results of such models are compared with experiment. Topics discussed include shear flow models (Princeton), simplified models for treating separation (Sisto, Princeton, Chi), classical linear theory, a local linearization theory, a transonic linear theory (Eckhaus-Williams), a transonic nonlinear (small disturbance) theory (LTRAN2), the experiment of Davis, and the experiment of Tijdeman. It is concluded that (1) shear flow models, which have proven very accurate in taking into account boundary layer effects for panel flutter, likely to be less so for lifting surface flutter; (2) an extremely simple model of separation shows promise, (3) for many applications in transonic flow, transonic linear theory will be adequate; (4) as the reduced frequency k increases, nonlinear effects decrease; (5) the concept of an aerodynamic transfer function remains useful even in the transonic regime; (6) for the transonic regime a composite aerodynamic representation in k using various aerodynamic models may be extremely useful.
