Lifting foil

Abstract

A lifting foil for an aircraft, a hydrofoil or the like having a pair of courses or wings. Vortex losses due to spanwise fluid flow are substantially reduced by joining the tips of the courses with flow guides configured for jointly terminating the undesired flows. Termination is effected by providing the flow guides with crossections cambered for reducing the dynamic pressure of fluid flowing in a spanwise direction across flow guide surfaces.

1 . The method of reducing spanwise flow of a fluid medium along the surface of a lifting foil, while said lifting foil is immersed in said fluid medium and moving therethrough in a direction perpendicular to the direction of said spanwise flow, said method comprising the steps of: 
 (1) generating a second flow of said fluid medium, and    (2) directing said second flow of said fluid reversely against said first named spanwise flow, so that said first and second spanwise flows are substantially balanced against each other.    
   
   
       2 . A method according to  claim 1  wherein said second flow of said fluid is generated by means of a second lifting foil positioned alongside said first named lifting foil.  
   
   
       3 . A method according to  claim 2  wherein said directing is achieved by end-to-end joining of said first and second lifting foils.  
   
   
       4 . In a lifting foil having an upper course extending sideward between an upper starboard end and an upper port end, and a lower course extending sideward between a a lower starboard end situated opposite a lower port end; said courses being immersed in a fluid medium and in relative movement therewith in a first direction, X; the method of reducing spanwise flow of said fluid in a second direction, Y, perpendicular to X comprising the steps of: 
 (1) constructing a starboard flow guide comprising an upper section, a mid-section disposed alongside said upper section and a lower section disposed alongside said mid-section, opposite said upper section,    (2) attaching said starboard flow guide between the starboard ends of said upper and lower courses by blended connection therewith,    (3) constructing a port flow guide comprising an upper section, a mid-section disposed alongside said upper section and a lower section disposed alongside said mid-section, opposite said upper section, and    (4) attaching said port flow guide between the port ends of said upper and lower courses by blended connection therewith,    
   
   
       5 . A method according to  claim 4  wherein said flow guides have cambered surfaces configured for reducing dynamic pressures from maximum values at said upper and lower sections to minimum values at said mid-sections.  
   
   
       6 . A method according to  claim 5  wherein said minimum values at said mid-sections are substantially zero.  
   
   
       7 . A method of suppressing vortices at tips of upper and lower biplane wings comprising the steps of: 
 (1) collecting fluid flowing spanwise at said tips, and    (2) directing collected fluid to common termination points between adjacent wing tips.    
   
   
       8 . Method of vortex suppression according to  claim 7  further comprising the step of progressively reducing the dynamic pressure of fluid being directed to said termination points.