Lift-induced drag

About: Lift-induced drag is a research topic. Over the lifetime, 2861 publications have been published within this topic receiving 41094 citations.

Inverse optimization of transonic wing shape for mid-size regional aircraft

Abstract: Multiobjective Genetic Algorithms (MOGAs) have been applied to design a transonic wing shape. First, the wing planform is optimized by solving a multidisciplinary optimization problem based on aerodynamic, structural and fuel storing objectives and constraints. Second, three-dimensional target pressure distribution is optimized for the aerodynamic inverse design with the previously designed planform. Minimization of the profile drag and the induced drag is performed under constraints on lift and other design principles. Corresponding wing surface geometry is obtained by Takanashi's inverse method. These two multiobjective optimization problems are solved by Pareto-based MOGAs coupled with appropriate CFD solvers. Applying these two wing design procedures, Pareto surfaces can be studied for trade-offs and a good compromised solution for the wing design can be obtained.

Wind tunnel tests to reduce aerodynamic drag of trains by smoothing the under-floor construction

Abstract: As a train runs at a higher speed, aerodynamic drag increases. On long train-sets such as Shinkansen trains, the aerodynamic drag is mainly generated by intermediate vehicles. In the previous researches, we proved that smoothing the under-floor construction reduces the aerodynamic drag. To investigate the mechanism of this effect, we performed wind tunnel tests with train models consisting of three vehicles (representing head, intermediate and tail vehicles) and measured the aerodynamic drag and the pressure distribution on the intermediate vehicle. Test results show that the reduced aerodynamic drag is mainly the effect of decreases in the pressure drag around bogies.

Optimum lift-drag ratio for a ram wing tube vehicle

Abstract: Munk's theorem specifying the downwash condition for minimum drag is generalized to include lifting surfaces operating in proximity to solid boundaries. A simple method for finding the optimum lift distribution on a wing above an infinite flat plane is developed. The optimum configuration for a ram wing in a tube is found, and by means of a simple transformation this is mapped into the previously obtained solution for a wing in ground effect. An expression for the induced power required is calculated, and it is shown that there is a favorable effect on this requirement for the case of tube vehicles which have significant blockage ratios. Experimental results are presented which demonstrate that at very small clearances the theory must be modified to include viscous effects, and because of these effects ram wings in tubes usually have lower induced power requirements than the inviscid theory would indicate. Nomenclature AR = aspect ratio A t = cross-sectional area of tube b = wing span = vehicle width Cof — induced drag coefficient CL = lift coefficient Di = induced drag F = volume flux