Compound airfoil

Abstract

An airfoil is provided that has an arrangement that improves the lift of an airfoil and that include surface features that change the performance of the airfoil. Protrusions are provided on the top surface of the airfoil such that channels are formed between adjacent protrusions that affect the flow of air there through. In an additional respect, indentations can be provided on the bottom surface of the airfoil that affect the flow of air there through.

What is claimed is: 
     
         1 . An airfoil for a vehicle, comprising:
 a top surface extending between a leading edge and a trailing edge on a top side of the airfoil and defining a chord length therebetween;   a bottom surface extending between the leading edge and the trailing edge on a bottom side of the airfoil;   a plurality of protrusions on the top surface of the air foil, wherein two adjacent protrusions define a channel therebetween that extends in the direction of the chord length;   wherein each channel has a leading portion, a middle portion, and a trailing portion, the channel being sized and shaped such that the leading portion and the trailing portion are wider than the middle portion.   
     
     
         2 . An airfoil of  claim 1 , wherein each channel extends along a majority of the top surface in the direction of the chord length. 
     
     
         3 . An airfoil of  claim 1 , wherein the length of the leading portion of each channel is shorter than the middle portion in the direction of the chord length. 
     
     
         4 . An airfoil of  claim 3 , wherein the length of the trailing portion of each channel is longer than the middle portion in the direction of the chord length. 
     
     
         5 . An airfoil of  claim 1 , wherein each channel extends along less than half of the top surface in the direction of the chord length. 
     
     
         6 . An airfoil of  claim 1 , wherein the walls of adjacent protrusions converge along a curved trajectory to define the leading portion of each channel. 
     
     
         7 . An airfoil of  claim 1 , wherein the walls of adjacent protrusions diverge along a generally linear trajectory to define the trailing portion of each channel. 
     
     
         8 . An airfoil of  claim 1 , wherein the walls of adjacent protrusions extend generally parallel to each other to define the middle portion of each channel. 
     
     
         9 . An airfoil of  claim 1 , wherein distance between a top surface of each protrusion and the top surface of the airfoil defines a depth of each channel, and the depth of each channel is greater in the leading portion than the middle portion and the trailing portion. 
     
     
         10 . An airfoil of  claim 1 , wherein each protrusion extends around the leading edge to the bottom surface of the airfoil such that adjacent protrusions form channels on the bottom surface of the airfoil. 
     
     
         11 . An airfoil for a vehicle, comprising:
 a top surface extending between a leading edge and a trailing edge on a top side of the airfoil and defining a chord length therebetween;   a bottom surface extending between the leading edge and the trailing edge on a bottom side of the airfoil;   a plurality of indentations on the bottom surface of the air foil each defining a channel, wherein   each indentation has a leading portion and a trailing portion, the channel being sized and shaped such that the trailing portion is wider than the leading portion.