# US 11,905,983 B2 · Systems and methods for active control of surface drag using electrodes

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- Number: US 11,905,983 B2
- Document ID: US11905983B2
- Status: Granted
- Kind: B2
- Application number: 17/154,763
- Filed: 2021-01-21
- Published: 2021-11-11
- Granted: 2024-02-20
- Earliest claimed: 2020-01-23
- Assignees: Deep Science, LLC
- Applicants: Deep Science, LLC
- Inventors: Brian C. Holloway; David William Wine
- Web page: https://patentgrep.com/patent/US11905983B2

## CPC

- F15D 1/0075: {comprising electromagnetic or electrostatic means for influencing the state of the fluid, e.g. for ionising the fluid or for generating a plasma}
- B64C 23/005: {by other means not covered by groups B64C23/02 - B64C23/08, e.g. by electric charges, magnetic panels, piezoelectric elements, static charges or ultrasounds}
- H05H 1/2406: {using dielectric barrier discharges, i.e. with a dielectric interposed between the electrodes}
- H05H 1/2439: {Surface discharges, e.g. air flow control}
- B64C 21/10: using other surface properties, e.g. roughness
- B64C 2230/12: by using electromagnetic tiles, fluid ionizers, static charges or plasma
- F15D 1/007: {comprising surfaces being moved by external supplied energy}
- F15D 1/12: by influencing the boundary layer
- Y02T 50/10: Drag reduction
- F15D: FLUID DYNAMICS, i.e. METHODS OR MEANS FOR INFLUENCING THE FLOW OF GASES OR LIQUIDS
- B64C: AEROPLANES; HELICOPTERS
- H05H: PLASMA TECHNIQUE (apparatus or processes specially adapted for producing X-rays H05G2/00); PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

A fluid control system includes a dielectric-barrier discharge (DBD) device, and processing circuitry. The processing circuitry is configured to obtain a streamwise length scale of a fluid flowing over a surface. The processing circuitry is also configured to obtain a convective time scale of the fluid flowing over the surface. The processing circuitry is also configured to operate the DBD device, based on the streamwise length scale and the convective time scale, to adjust a flow property of the fluid.

## Claims

### Claim 1

A fluid control system, comprising:
a dielectric-barrier discharge (DBD) device; and
processing circuitry configured to:
obtain a streamwise length scale of a flow regime of a fluid flowing over a surface, where the streamwise length scale is between 10η and 100,000η, where η is a viscous length scale of the flow regime of the fluid;
obtain a convective time scale of the flow regime of the fluid flowing over the surface, where the convective time scale is between 10η′ and 10,000η′, where η′ is a viscous time scale of the flow regime of the fluid; and
operate the DBD device, based on the streamwise length scale and the convective time scale, to provide momentum in a spanwise direction to the fluid flowing over the surface to adjust a flow property of the fluid.

### Claim 2 (depends on 1)

The fluid control system of claim 1, wherein the flow property is at least one of a flow rate, a velocity, a momentum, a transverse momentum, a shear stress, a velocity profile, a velocity gradient, or a skin-friction coefficient of the fluid.

### Claim 3 (depends on 1)

The fluid control system of claim 1, wherein the DBD device is configured to provide spanwise bi-directional momentum to the fluid flowing over the surface.

### Claim 4 (depends on 1)

The fluid control system of claim 1, wherein the DBD device comprises a plurality of DBD electrodes.

### Claim 5 (depends on 4)

The fluid control system of claim 4, wherein the processing circuitry is configured to sequentially activate the plurality of DBD electrodes to provide the momentum in the spanwise direction to the fluid flowing over the surface.

### Claim 6 (depends on 4)

The fluid control system of claim 4, wherein each of the plurality of DBD electrodes has a height less than a hydrodynamic height.

### Claim 7 (depends on 4)

The fluid control system of claim 4, wherein the DBD electrodes are arranged in an array extending along at least the spanwise direction, a streamwise direction, or a direction other than the spanwise direction or the streamwise direction.

### Claim 8 (depends on 7)

The fluid control system of claim 7, wherein each of the plurality of DBD electrodes has a length and a spatial frequency, the length and the spatial frequency of each of the plurality of DBD electrodes varying based on a position of each of the plurality of DBD electrodes.

### Claim 9 (depends on 7)

The fluid control system of claim 7, wherein each of the plurality of DBD electrodes has a length and a spatial frequency, the length and the spatial frequency of each of the plurality of DBD electrodes varying based on expected local flow conditions of the fluid flowing over the surface and the spatial frequency being between 10 mm and 50 mm.

### Claim 10 (depends on 4)

The fluid control system of claim 4, wherein the plurality of DBD electrodes are sized to control eddy motions of the fluid flowing over the surface based on the streamwise length scale and the convective time scale.

### Claim 11 (depends on 1)

The fluid control system of claim 1, wherein the processing circuitry is configured to operate the DBD device to provide the momentum to the fluid flowing over the surface by operating the DBD device according to a temporal frequency, the temporal frequency based on the convective time scale.

### Claim 12 (depends on 1)

The fluid control system of claim 1, wherein the processing circuitry is configured to operate the DBD device to provide spanwise momentum to the fluid flowing over the surface, the spanwise momentum being between 1% and 20% of a freestream fluid momentum of the fluid flowing over the surface.

### Claim 13 (depends on 1)

The fluid control system of claim 1, wherein the surface comprises one or more riblets protruding from the surface, wherein the one or more riblets at least partially surround the DBD device.

### Claim 14 (depends on 1)

The fluid control system of claim 1, wherein the momentum reduces a skin-friction drag on the surface.

### Claim 15

A method for controlling a property of a fluid that flows over a surface, the method comprising:
obtaining a streamwise length scale and a convective time scale of a flow regime of the fluid that flows over the surface at least partially based on a sensor input,
wherein the streamwise length scale is a function of a viscous length scale, η, of the flow regime of the fluid, and wherein the convective time scale is a function of a viscous time scale, η′, of the flow regime of the fluid;
determining an operation of a dielectric-barrier discharge (DBD) device based on the streamwise length scale and the convective time scale of the flow regime to control a flow property of the flow regime of the fluid; and
operating the DBD device according to the determined operation to provide momentum in a spanwise direction to the flow regime of the fluid that flows over the surface to adjust the flow property of the flow regime of the fluid.

### Claim 16 (depends on 15)

The method of claim 15, wherein the flow property is at least one of a flow rate, a velocity, a momentum, a transverse momentum, a shear stress, a velocity profile, a velocity gradient, or a skin-friction coefficient of the fluid.

### Claim 17 (depends on 15)

The method of claim 15, wherein the streamwise length scale has a value between 10η and 100,000η.

### Claim 18 (depends on 15)

The method of claim 15, wherein the convective time scale has a value between 10η′ and 10,000η.

### Claim 19 (depends on 15)

The method of claim 15, wherein the determined operation comprises operating the DBD device to provide spanwise bi-directional momentum to the fluid flowing over the surface.

### Claim 20 (depends on 15)

The method of claim 15, wherein the DBD device comprises a plurality of DBD electrodes.

### Claim 21 (depends on 20)

The method of claim 20, wherein the determined operation comprises sequentially activating the plurality of DBD electrodes to provide the momentum in the spanwise direction to the fluid flowing over the surface.

### Claim 22 (depends on 20)

The method of claim 20, wherein each of the plurality of DBD electrodes has a height less than a hydrodynamic height.

### Claim 23 (depends on 20)

The method of claim 20, wherein the plurality of DBD electrodes are arranged in an array extending along at least a spanwise direction, a streamwise direction, or a direction other than the spanwise direction or the streamwise direction.

### Claim 24 (depends on 23)

The method of claim 23, wherein each of the plurality of DBD electrodes has a length and a spatial frequency, the length and the spatial frequency of each of the plurality of DBD electrodes varying based on a position of each of the plurality of DBD electrodes.

### Claim 25 (depends on 23)

The method of claim 23, wherein each of the plurality of DBD electrodes has a length and a spatial frequency, the length and the spatial frequency of each of the plurality of DBD electrodes varying based on expected local flow conditions of the fluid flowing over the surface.

### Claim 26 (depends on 20)

The method of claim 20, wherein the plurality of DBD electrodes are sized to control eddy motions of the fluid flowing over the surface based on the streamwise length scale and the convective time scale.

### Claim 27 (depends on 15)

The method of claim 15, wherein the determined operation comprises operating the DBD device to provide the momentum to the fluid flowing over the surface by operating the DBD device according to a temporal frequency, the temporal frequency based on the convective time scale.

### Claim 28 (depends on 15)

The method of claim 15, wherein the determined operation comprises operating the DBD device to provide spanwise momentum to the fluid flowing over the surface, the spanwise momentum being between 1% and 20% of a freestream fluid momentum of the fluid flowing over the surface.

### Claim 29 (depends on 15)

The method of claim 15, wherein the momentum reduces a skin-friction drag on the surface.

### Claim 30

A method for adjusting a property of a fluid that flows over a surface, the method comprising:
obtaining a streamwise length scale of a flow regime of the fluid that flows over the surface, wherein the streamwise length scale is between 10η and 100,000η, where η is a viscous length scale of the flow regime of the fluid;
obtaining a convective time scale of the flow regime of the fluid that flows over the surface, wherein the convective time scale is between 10η′ and 10,000η, where η′ is a viscous time scale of the flow regime of the fluid; and
providing momentum to the fluid in a spanwise direction to adjust a flow property of the flow regime of the fluid based on the streamwise length scale and the convective time scale.

### Claim 31 (depends on 30)

The method of claim 30, wherein the flow property is at least one of a flow rate, a velocity, a momentum, a transverse momentum, a shear stress, a velocity profile, a velocity gradient, or a skin-friction coefficient of the fluid.

### Claim 32 (depends on 30)

The method of claim 30, wherein providing the momentum to the fluid to adjust the flow property of the flow regime of the fluid comprises operating a dielectric-barrier discharge (DBD) device, the DBD device comprising a plurality of DBD electrodes.

### Claim 33 (depends on 32)

The method of claim 32, comprising operating the DBD device to provide spanwise bi-directional momentum to the fluid flowing over the surface.

### Claim 34 (depends on 32)

The method of claim 32, wherein providing the momentum comprises sequentially activating the plurality of DBD electrodes to provide the momentum in the spanwise direction to the fluid flowing over the surface.

### Claim 35 (depends on 34)

The method of claim 34, wherein the plurality of DBD electrodes are sized to control eddy motions of the fluid flowing over the surface based on the streamwise length scale and the convective time scale.

### Claim 36 (depends on 34)

The method of claim 34, wherein providing the momentum to the fluid comprises operating the DBD device to provide the momentum to the fluid flowing over the surface by operating the DBD device according to a temporal frequency, the temporal frequency based on the convective time scale.

### Claim 37 (depends on 34)

The method of claim 34, wherein providing the momentum to the fluid comprises operating the DBD device to provide spanwise momentum to the fluid flowing over the surface, the spanwise momentum being between 1% and 20% of a freestream fluid momentum of the fluid flowing over the surface.

### Claim 38 (depends on 32)

The method of claim 32, wherein each of the plurality of DBD electrodes has a height less than a hydrodynamic height.

### Claim 39 (depends on 32)

The method of claim 32, wherein the plurality of DBD electrodes are arranged in an array extending along at least a spanwise direction, a streamwise direction, or a direction other than the spanwise direction or the streamwise direction.

### Claim 40 (depends on 39)

The method of claim 39, wherein each of the plurality of DBD electrodes has a length and a spatial frequency, the length and the spatial frequency of each of the plurality of DBD electrodes varying based on a position of each of the plurality of DBD electrodes.

### Claim 41 (depends on 39)

The method of claim 39, wherein each of the plurality of DBD electrodes has a length and a spatial frequency, the length and the spatial frequency of each of the plurality of DBD electrodes varying based on expected local flow conditions of the fluid flowing over the surface.

### Claim 42

A wind turbine comprising:
a plurality of turbine blades;
a base configured to support the turbine blades, wherein each of the plurality of turbine blades is configured to rotate relative to the base as a fluid flows across the plurality of turbine blades; and
a fluid control system positioned on at least one of the turbine blades, the fluid control system comprising:
a dielectric-barrier discharge (DBD) device; and
processing circuitry configured to:
obtain a streamwise length scale of at least one flow regime of the fluid;
obtain a convective time scale of the at least one flow regime of the fluid; and
operate the DBD device, based on the streamwise length scale and the convective time scale, to provide momentum in a spanwise direction to adjust a flow property of the fluid.

### Claim 43 (depends on 42)

The wind turbine of claim 42, wherein the flow property is at least one of a flow rate, a velocity, a momentum, a transverse momentum, a shear stress, a velocity profile, a velocity gradient, or a skin-friction coefficient of the fluid.

### Claim 44 (depends on 42)

The wind turbine of claim 42, wherein the fluid control system is configured to adjust the flow property of the fluid to reduce a skin-friction drag on a surface of the wind turbine.

### Claim 45

An aircraft comprising:
a fuselage;
a component comprising at least one of a wing or a flight control surface coupled with the fuselage; and
a fluid control system positioned on at least one of the fuselage or the component, the fluid control system comprising:
a dielectric-barrier discharge (DBD) device; and
processing circuitry configured to:
obtain a streamwise length scale of at least one flow regime of a fluid flowing over the at least one of the fuselage or the component;
obtain a convective time scale of the at least one flow regime of the fluid; and
operate the DBD device, based on the streamwise length scale and the convective time scale, to provide momentum in a spanwise direction to adjust a flow property of the fluid.

### Claim 46 (depends on 45)

The aircraft of claim 45, wherein the flow property is at least one of a flow rate, a velocity, a momentum, a transverse momentum, a shear stress, a velocity profile, a velocity gradient, or a skin-friction coefficient of the fluid.

### Claim 47 (depends on 45)

The aircraft of claim 45, wherein the fluid control system is configured to adjust the flow property of the fluid to reduce a skin-friction drag on a surface of the fuselage or the component of the aircraft.