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.

Moving Model Test of High-Speed Train Aerodynamic Drag Based on Stagnation Pressure Measurements.

Abstract: A moving model test method based on stagnation pressure measurements is proposed to measure the train aerodynamic drag coefficient. Because the front tip of a high-speed train has a high pressure area and because a stagnation point occurs in the center of this region, the pressure of the stagnation point is equal to the dynamic pressure of the sensor tube based on the obtained train velocity. The first derivation of the train velocity is taken to calculate the acceleration of the train model ejected by the moving model system without additional power. According to Newton’s second law, the aerodynamic drag coefficient can be resolved through many tests at different train speeds selected within a relatively narrow range. Comparisons are conducted with wind tunnel tests and numerical simulations, and good agreement is obtained, with differences of less than 6.1%. Therefore, the moving model test method proposed in this paper is feasible and reliable.

Prediction of drag at subsonic and transonic speeds using Euler methods

Abstract: A technique for the evaluation of aerodynamic drag from flowfield solutions based on the Euler equations is discussed. The technique is limited to steady attached flows around three-dimensional configurations in the absence of active systems such as surface blowing/suction and propulsion. It allows the decomposition of the total drag into induced drag and wave drag and, consequently, it provides more information on the drag sources than the conventional surface-pressure integration technique. The induced drag is obtained from the integration of the kinetic energy (per unit distance) of the trailing vortex system on a wake plane and the wave drag is obtained from the integration of the entropy production on a plane just downstream of the shocks. The drag-evaluation technique is applied to three-dimensional flowfield solutions for the ONERA M6 wing as well as an aspect-ratio-7 wing with an elliptic spanwise chord distribution and an NACA-0012 section shape. Comparisons between the drag obtained with the present technique and the drag based on the integration of surface pressures are presented for two Euler codes.

Correlation of theory to wind-tunnel data at Reynolds numbers below 500,000

Abstract: This paper presents results obtained from two airfoil analysis methods compared with previously published wind tunnel test data at chord Reynolds numbers below 500,000. The analysis methods are from the Eppler-Somers airfoil design/analysis code and from ISES, the Drela-Giles airfoil design/analysis code. The experimental data are from recent tests of the Eppler 387 airfoil in the NASA Langley Low Turbulence Pressure Tunnel. For R ≥ 200,000, lift and pitching moment predictions from both theories compare well with experiment. Drag predictions from both theories also agree with experiment, although to different degrees. The Drela-Giles code also predicts pressure distributions which compare well with the experimental pressure distributions, including those cases with laminar separation bubbles. For Reynolds numbers of 60,000 and 100,000, lift and pitching moment predictions from both theories are in fair agreement with experiment. However, most of the drag predictions from the Eppler-Somers code are accompanied with separation bubble warnings which indicate that the drag predictions are too low. With the Drela-Giles code, there is a large discrepancy between the computed and experimental pressure distributions in cases with laminar separation bubbles, although the drag polar predictions are similar in trend to experiment.