Prediction of Transition Location and Its Effects on Shock Bump Control on a Natural Laminar Flow Aerofoil
The reduction of overall drag for an aircraft operating at its cruise condition is a prevalent goal for many involved in the aerodynamic design of transonic aircraft. Bringing both financial and environmental benefits, savings on the order of single drag counts are considered to be significant. Many concepts have been trailed in the pursuit of increased lift to drag ratios at transonic cruise. One of them, in terms of novel concepts addressing this issue, is the preservation of natural laminar flow over an increased proportion of the wing area. The laminarisation of a wing reduces overall drag via both a reduction in skin friction drag resulting from decreased mixing across the boundary layer and a reduction in pressure drag resulting from variations in effective aerofoil shape due to reductions in the boundary layer’s displacement thickness. Another concept which reduces the wave drag via the reduction of the strength of the near normal shock-waves on the wing upper surface is the application of 2D shock control bumps to the laminar or turbulent wings by Ashill et al. [1, 2]. Since Qin et al.  proposed 3D bumps for shock control, detailed experimental and numerical studies, including bump shape optimisation have been conducted by Wong et al. , Ogawa et al.  and Qin et al. . While the λ–shock structure is observed as the key feature for some bump geometries tested [4, 5], e.g. ramp bumps, the optimised 2D and 3D bumps show a “knee-shaped” shock structure for smoothly (continuity of the first derivative) contoured bump designs .
KeywordsShock Structure Wave Drag Pressure Drag Transition Onset Laminar Separation Bubble
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