TIP SPOILER 



The tip spoiler is similar to a fence, except that it is oriented in a 

 spanwise manner, perpendicular to the incoming flow. Spoilers can be loc- 

 ated at various chordwise locations on the wing pressure or suction side, 

 but ideally the location should be such that the spoiler-increased turbulent 

 flow is absorbed directly into the vortex core, thereby dissipating the 

 vortex core energy. 



The numerous tip spoiler investigations generally concur that this 



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 device is highly effective; e.g., some reports claim an 80 percent re- 



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 duction in the tip vortex circulation strength, while others indicate 



that a small tip spoiler may be as effective as a much larger one, with 

 substantially less parasitic drag. However, there also is a large discrep- 

 ancy in the reported spoiler drag — from negligible to prohibitive. Again, 

 based upon the possible performance penalty and the potential for local sur- 

 face cavitation, spoilers hold little promise for application to propellers. 



TRAILING EDGE DEVICES: SPLINES AND HONEYCOMB 



Splines and honeycomb (shown in Figure 4) represent trailing edge de- 

 vices which are located off the wing and just aft of the wing-tip trailing 

 edge. These devices are positioned in the path of the tip vortex, the in- 

 tent being to destroy the vortex structure and promote early decay. Recent 

 investigations involving the application of these concepts to weaken large 

 aircraft vortex wakes report ' a high degree of effectiveness, but also 

 an equally high increase in drag. 



The trailing edge devices operate in the downstream tip vortex wake 

 region and, as such, do not affect either the rollup process on the wing or 

 the tip vortex structure in the wing near field. On this basis, it appears 

 that these devices would have little, if any, effect on the inception of 

 tip vortex cavitation. In addition, for marine propeller application, these 

 concepts would suffer obvious structural limitations. 



TIP MASS INJECTION 



As implied by the title, tip mass injection involves the ejection of a 

 fluid in the vicinity of the wing tip vortex. Of all the devices reviewed. 



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