A test campaign was undertaken in the European Transonic Wind tunnel (ETW) using a large half model of an aircraft with a clean Natural Laminar Flow wing. The model was designed to: 1) Investigate surface tolerance requirements for Natural Laminar Flow aircraft; 2) To validate the high speed aerodynamic design process for Natural Laminar Flow wings within Airbus and to investigate means of validating the expected performance benefit of laminar flow over and above that of a tripped turbulent wing. As part of the validation of performance predictions for a Natural Laminar Flow wing in free and tripped conditions, the drag impact of turbulent wedges on the laminar increment has to be quantified. This is because even in a facility with extremely good flow quality and sound operating procedures for Natural Laminar Flow testing, turbulent wedges due to flow contamination or leakage at model joints can occur that reduce the laminar extent on the wing during the course of a test run. An investigation to compare Computational Fluid Dynamics (CFD) simulations of the Natural Laminar Flow wing in free and fixed transition cases with results obtained from the ETW test was undertaken. The investigation showed that CFD simulations could replicate the drag increment due to upper surface laminarity measured in ETW, provided that the turbulent wedges observed in the tunnel for a given condition were modelled.
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