The Drag Due to Lift of Plane Wings at Subsonic Speeds

1966 ◽  
Vol 70 (665) ◽  
pp. 595-599 ◽  
Author(s):  
D. Gardner ◽  
J. Weir
Keyword(s):  
Wind Tunnel ◽  
Reynolds Numbers ◽  
Considerable Improvement ◽  
Induced Drag ◽  
Wind Tunnel Measurements ◽  
Lift Curve ◽  
Mach Numbers ◽  
Drag Factor

SummaryThis note outlines a method for the prediction of drag due to lift of plane wings at Mach numbers below drag divergence and Reynolds numbers above 106. The method is based on the correlation of a number of wind tunnel measurements in terms of the effect of viscosity on lift curve slope. A comparison is made of the accuracy of estimating the induced drag factor, k, using this method, with the method of ret. 1, and it is shown that considerable improvement has been made, and that, in general, the predicted value of k is within 10% of experiment.

Drag reduction by wing tip slots in a gliding Harris' hawk, Parabuteo unicinctus

1995 ◽  
Vol 198 (3) ◽  
pp. 775-781 ◽  
Author(s):  
V A Tucker
Keyword(s):  
Wind Tunnel ◽  
Drag Reduction ◽  
Aerodynamic Drag ◽  
Mean Value ◽  
Induced Drag ◽  
Minimum Drag ◽  
Before And After ◽  
Parabuteo Unicinctus ◽  
Wing Tips ◽  
Drag Factor

The anterior-most primary feathers of many birds that soar over land bend upwards and separate vertically to form slotted wing tips during flight. The slots are thought to reduce aerodynamic drag, although drag reduction has never been demonstrated in living birds. Wing theory explains how the feathers that form the tip slots can reduce induced drag by spreading vorticity horizontally along the wing and by acting as winglets, which are used on aircraft to make wings non-planar and to spread vorticity vertically. This study uses the induced drag factor to measure the induced drag of a wing relative to that of a standard planar wing with the same span, lift and speed. An induced drag factor of less than 1 indicates that the wing is non-planar. The minimum drag of a Harris' hawk gliding freely in a wind tunnel was measured before and after removing the slots by clipping the tip feathers. The unclipped hawk had 70­90 % of the drag of the clipped hawk at speeds between 7.3 and 15.0 m s-1. At a wing span of 0.8 m, the unclipped hawk had a mean induced drag factor of 0.56, compared with the value of 1.10 assumed for the clipped hawk. A Monte Carlo simulation of error propagation and a sensitivity analysis to possible errors in measured and assumed values showed that the true mean value of the induced drag factor for the unclipped hawk was unlikely to be more than 0.93. These results for a living bird support the conclusions from a previous study of a feathered tip on a model wing in a wind tunnel: the feathers that form the slotted tips reduce induced drag by acting as winglets that make the wings non-planar and spread vorticity both horizontally and vertically.

Experimental investigations of flow over NACA airfoils 0021 and 4412 of wind turbine blades with and without Tubercles

2021 ◽  
pp. 0309524X2110071
Author(s):  
Usman Butt ◽  
Shafqat Hussain ◽  
Stephan Schacht ◽  
Uwe Ritschel
Keyword(s):  
Wind Tunnel ◽  
Drag Coefficient ◽  
Wind Turbine ◽  
Critical Region ◽  
Lift Coefficient ◽  
Turbine Blades ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Experimental Investigations ◽  
Wind Turbine Blades

Experimental investigations of wind turbine blades having NACA airfoils 0021 and 4412 with and without tubercles on the leading edge have been performed in a wind tunnel. It was found that the lift coefficient of the airfoil 0021 with tubercles was higher at Re = 1.2×105 and 1.69×105 in post critical region (at higher angle of attach) than airfoils without tubercles but this difference relatively diminished at higher Reynolds numbers and beyond indicating that there is no effect on the lift coefficients of airfoils with tubercles at higher Reynolds numbers whereas drag coefficient remains unchanged. It is noted that at Re = 1.69×105, the lift coefficient of airfoil without tubercles drops from 0.96 to 0.42 as the angle of attack increases from 15° to 20° which is about 56% and the corresponding values of lift coefficient for airfoil with tubercles are 0.86 and 0.7 at respective angles with18% drop.

Supersonic Nonequilibrium Plasma Wind-Tunnel Measurements of Shock Modification and Flow Visualization

AIAA Journal ◽  
10.2514/2.841 ◽  
2000 ◽  
Vol 38 (10) ◽  
pp. 1879-1888 ◽  
Author(s):  
R. Yano ◽  
V. Contini ◽  
E. Plonjes ◽  
P. Palm ◽  
S. Merriman ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Flow Visualization ◽  
Nonequilibrium Plasma ◽  
Wind Tunnel Measurements

Wind Tunnel Measurements of the E-8C Modeled With and Without Winglets

2007 ◽  
Author(s):  
Mark Reeder ◽  
Walt Allen ◽  
John Phillips ◽  
Robert Dimmick
Keyword(s):  
Wind Tunnel ◽  
Wind Tunnel Measurements
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