Effect of Taper Ratio at Low Reynolds Number

Abstract

A low speed wind-tunnel investigation is presented documenting the impact of taper ratio at low Reynolds number. An wing using a S8036 section was tested at and 150,000. Taper ratio was varied from 1 down to 0.2 in 0.2 increments. An analytic prediction method as well as extended numerical lifting line theory incorporating nonlinear section data was implemented to compare with experiment. The experimental results indicated a weak dependence of peak lift to drag ratio on taper ratio for both Reynolds numbers. Surface flow visualization showed the presence of a large laminar transitional bubble on the upper wing surface. The relative extent of the bubble was observed to increase towards the tip region for tapered planforms. Agreement between theory and experiment in terms of lift and drag estimation was good. Planform optimization using the extended numerical lifting line theory indicated that at the test conditions and using the selected airfoil section, a planform that differs from straight taper or elliptic may be most efficient.