BOUNDARY-LAYER STABILITY ANALYSIS OF FLIGHT-MEASURED TRANSITION DATA

Correlation of in-flight boundary-layer transition experiments with linear boundary-layer stability theory contributes both to the validation of the numerical methods as well as the analysis of the measured transition process. Transition results obtained in a recent flight experiment, in which the extent of laminar flow and the transition process on the wing of a business-jet fitted with an instrumented glove section were determined, are analyzed. The experiment was conducted at freestream Mach numbers from 0.55 to 0.82, chord Reynolds numbers from 10 to 20x10⁶, and leading-edge sweep angles of 17° to 20°. The growth of both Tollmien-Schlichting and crossflow instabilities are predicted using the eⁿ method for several flight conditions and the calculated “n-factors” at transition onset are correlated. Comparison of the measured dominant boundary-layer disturbance frequencies and the predicted unstable frequencies shows fair agreement for several of the flight conditions studied.