Systems and methods for active control of surface drag

Abstract

A fluid control system includes a deformable surface that covers a body in at least a first and second direction. The first direction is orthogonal to the second direction. The deformable surface includes a bottom side that faces the body and a top side that is opposite the bottom side. The fluid control system also includes at least one deformer between the deformable surface and the body. The at least one deformer is configured to modify a boundary layer of a fluid that is flowing over the deformable surface by selectively deforming the top side of the surface.

What is claimed is: 
     
         1 . A fluid flow control system, comprising:
 a deformable surface covering a body in at least a first and second direction, the first direction orthogonal to the second direction, the deformable surface including a bottom side facing the body and a top side opposite the bottom side; and   at least one deformer between the deformable surface and the body, the at least one deformer configured to modify a boundary layer of a fluid flowing over the deformable surface by selectively deforming the top side of the deformable surface.   
     
     
         2 . The fluid flow control system of  claim 1 , wherein the at least one deformer selectively deforms the top side of the deformable surface in a plane of the top side of the deformable surface. 
     
     
         3 . The fluid flow control system of  claim 1 , wherein the at least one deformer selectively deforms the top side of the deformable surface out of a plane of the top side of the deformable surface. 
     
     
         4 . The fluid flow control system of  claim 1 , wherein the at least one deformer is driven at a resonant frequency of the at least one deformer. 
     
     
         5 . The fluid flow control system of  claim 1 , wherein:
 the at least one deformer deforms the top side of the deformable surface to generate one or more surface waves.   
     
     
         6 . The fluid flow control system of  claim 5 , wherein:
 the at least one deformer selectively deforms the top side of the deformable surface in an oscillatory manner to generate the one or more surface waves.   
     
     
         7 . The fluid flow control system of  claim 1 , wherein:
 the fluid is a first fluid;   the deformable surface includes a plurality of cavities; and   the at least one deformer includes at least one second fluid channel fluidly coupled to the plurality of cavities, the at least one deformer configured to selectively generate a plurality of deformations by controlling an amount of second fluid in the plurality of cavities.   
     
     
         8 . The fluid flow control system of  claim 7 , wherein:
 the plurality of cavities are positioned to generate surface waves when the fluid is selectively delivered.   
     
     
         9 . The fluid flow control system of  claim 7 , wherein:
 the fluid delivered to the plurality of cavities includes a gas.   
     
     
         10 . The fluid flow control system of  claim 1 , wherein:
 the at least one deformer includes at least one actuator configured to deform the deformable surface by applying a force against the deformable surface at a plurality of controlled locations.   
     
     
         11 . The fluid flow control system of  claim 10 , wherein:
 the plurality of controlled locations are positioned to generate surface waves when the at least one deformer deforms the deformable surface.   
     
     
         12 . The fluid flow control system of  claim 1 , comprising:
 at least one sensor that measures at least one characteristic of the fluid surrounding the deformable surface.   
     
     
         13 . The fluid flow control system of  claim 12 , wherein:
 the at least one sensor measures a flow rate of fluid inside the boundary layer surrounding the deformable surface.   
     
     
         14 . The fluid flow control system of  claim 12 , wherein:
 the at least one sensor measures a flow rate of fluid outside of the boundary layer surrounding the deformable surface.   
     
     
         15 . The fluid flow control system of  claim 1 , comprising:
 a control circuit configured to control operation of the at least one deformer based on a measured property of the fluid flowing over the deformable surface.   
     
     
         16 . The fluid flow control system of  claim 1 , wherein:
 the deformable surface includes at least one of an elastomeric material, a thin film material, silicon nitrite, graphite, or a long chain polymer.   
     
     
         17 . The fluid flow control system of  claim 1 , wherein:
 the deformable surface includes a flexible material and is configured to be stretched over bodies of different shapes.   
     
     
         18 . The fluid flow control system of  claim 1 , wherein:
 the deformable surface includes a material configured to respond to one or more electromagnetic impulses; and   the at least one deformer includes at least one electromagnetic actuator configured to deform the deformable surface in a plurality of controlled locations by selectively generating the one or more electromagnetic impulses.   
     
     
         19 . A fluid flow control system, comprising:
 a deformable surface covering a body in at least a first and second direction, the first direction orthogonal to the second direction, the deformable surface including a bottom side facing the body and a top side opposite the bottom side;   at least one deformer between the deformable surface and the body; and   at least one sensor configured to measure a parameter of a fluid flowing over the deformable surface; and   a control circuit configured to control the at least one deformer to modify a boundary layer of a fluid flowing over the deformable surface by selectively deforming the top side of the deformable surface.   
     
     
         20 . A method, comprising:
 measuring a parameter of a fluid flowing over a deformable surface, the deformable surface covering a body in at least a first and second direction, the first direction orthogonal to the second direction, the deformable surface including a bottom side facing the body and a top side opposite the bottom side;   generating, by a control circuit, a control signal to modify the parameter based on the measured parameter; and   transmitting, by the control circuit, the control signal to at least one deformer between the deformable surface and the body to cause the at least one deformer to selectively deform the top side of the deformable surface to modify the parameter of the fluid.   
     
     
         21 . The method of  claim 20 , comprising selectively deforming, by the at least one deformer, the top side of the deformable surface in a plane of the top side of the deformable surface. 
     
     
         22 . The method of  claim 20 , comprising selectively deforming, by the at least one deformer, the top side of the deformable surface out of a plane of the top side of the deformable surface. 
     
     
         23 . The method of  claim 20 , comprising driving the at least one deformer at a resonant frequency of the at least one deformer. 
     
     
         24 . The method of  claim 20 , comprising:
 generating one or more surface waves using the at least one deformer.   
     
     
         25 . The method of  claim 24 , comprising deforming the top side of the deformable surface in an oscillatory manner to generate the one or more surface waves. 
     
     
         26 . The method of  claim 20 , wherein:
 the fluid is a first fluid;   the deformable surface includes a plurality of cavities;   the at least one deformer includes at least second one fluid channel fluidly coupled to the plurality of cavities; and   selectively deforming the top side of the deformable surface includes controlling an amount of second fluid in the plurality of cavities.   
     
     
         27 . The method of  claim 26 , wherein:
 the plurality of cavities generate surface waves when the fluid is selectively delivered.   
     
     
         28 . The method of  claim 26 , wherein:
 the fluid delivered to the plurality of cavities includes a gas.   
     
     
         29 . The method of  claim 20 , wherein:
 the at least one deformer includes at least one actuator, and the method includes using the at least one actuator to apply a force against the deformable surface at a plurality of controlled locations.   
     
     
         30 . The method of  claim 29 , wherein:
 the plurality of controlled locations are positioned to generate surface waves when the at least one deformer deforms the deformable surface.   
     
     
         31 . The method of  claim 20 , comprising:
 measuring a flow rate of fluid inside a boundary layer surrounding the deformable surface.   
     
     
         32 . The method of  claim 20 , comprising:
 measuring a flow rate of fluid outside a boundary layer surrounding the deformable surface.   
     
     
         33 . The method of  claim 20 , comprising:
 the deformable surface includes at least one of an elastomeric material, a thin film material, silicon nitrite, graphite, or a long chain polymer.   
     
     
         34 . The method of  claim 20 , wherein:
 the deformable surface includes a flexible material and is configured to be stretched over bodies of different shapes.   
     
     
         35 . The method of  claim 20 , comprising:
 generating, by at least one electromagnetic actuator of the at least one deformer, one or more electromagnetic impulses to cause a material of the deformable surface to respond to the one or more electromagnetic impulses.