Reduced drag system for windmills, fans, propellers, airfoils, and hydrofoils

Abstract

Airfoil and hydrofoils systems with structures having a surface texture defined by fractal geometries are described. Raised portions or fractal bumps can be included on the surfaces, forming a surface texture. The surface textures can be defined by two-dimensional fractal shapes, partial two-dimensional fractal shapes, non-contiguous fractal shapes, three-dimensional fractal objects, and partial three-dimensional fractal objects. The surfaces can include indents having fractal geometries. The indents can have varying depths and can be bordered by other indents, or bumps, or smooth portions of the airfoil or hydrofoil structure. The fractal surface textures can reduce vortices inherent from airfoil and hydrofoil structures. The roughness and distribution of the fractal surface textures reduce the vortices, improving laminar flow characteristics and at the same time reducing drag. The systems are passive and do not require applied power.

1 . A turbulence reduction system comprising:
 a fluid-contact surface configured and arranged for movement within a fluid; and   one or more fractal-based surface features configured and arranged to reduce drag when the fluid-contact surface is moving relative to the fluid.   
     
     
         2 . The system of  claim 1 , wherein the one or more fractal-based surface features comprise one or more Koch stars. 
     
     
         3 . The system of  claim 1 , wherein the one or more fractal-based surface features comprise one or more Quadric Koch islands. 
     
     
         4 . The system of  claim 1 , wherein the one or more fractal-based surface features comprise indents. 
     
     
         5 . The system of  claim 1 , wherein the one or more fractal-based surface features comprise protrusions. 
     
     
         6 . The system of  claim 5 , wherein the one or more fractal-based surface features further comprise indents. 
     
     
         7 . The system of  claim 1 , wherein the one or more fractal-based surface features comprise a feature defined by a de Rham curve. 
     
     
         8 . The system of  claim 2 , wherein the one or more fractal-based surface features are about 5 mm to about 30 mm along a major axis. 
     
     
         9 . The system of  claim 2 , wherein the one or more fractal-based surface features are about 5 mm to about 30 mm in depth. 
     
     
         10 . The system of  claim 2 , wherein the one or more fractal-based surface features are about 5 mm to about 30 mm in height. 
     
     
         11 . The system of  claim 2 , wherein the Koch star is a 3rd or 4th generation Koch star. 
     
     
         12 . The system of  claim 1 , wherein the fluid contact surface is a hydrofoil or airfoil. 
     
     
         13 . The system of  claim 1 , wherein the one or more fractal-based surface features comprise a plurality of surface features configured and arranged as an array. 
     
     
         14 . The system of  claim 13 , wherein rows of the array are spaced apart in a nonlinear progression. 
     
     
         15 . The system of  claim 14 , wherein the nonlinear progression is parallel to a direction of flight of the fluid-contact surface. 
     
     
         16 . The system of  claim 14 , wherein the nonlinear progression is anti-parallel to a direction of flight of the fluid-contact surface. 
     
     
         17 . The system of  claim 1 , wherein the one or more fractal-based surface features comprise holes in the fluid-contact surface. 
     
     
         18 . The system of  claim 17 , further comprising an air supply for pumping air through the holes to reduce turbulence. 
     
     
         19 . The system of  claim 17 , further comprising an liquid supply for pumping liquid through the holes to reduce turbulence. 
     
     
         20 . The system of  claim 1 , wherein the one or more fractal-based surface features are disposed on a trailing edge of a wing.