In-plane transverse momentum injection to disrupt large-scale eddies in a turbulent boundary layer

Patent metadata

Field	Value
Publication number	US-11933334-B2
Application number	US-202318320154-A
Country	US
Kind code	B2
Filing date	May 18, 2023
Priority date	Feb 17, 2021
Publication date	Mar 19, 2024
Grant date	Mar 19, 2024

Abstract

Systems and methods are described herein to implement transverse momentum injection at low frequencies to directly modify large-scale eddies in a turbulent boundary layer on a surface of an object. A set of transverse momentum injection actuators may be positioned on the surface of the object to affect large-scale eddies in the turbulent boundary layer. The system may include a controller to selectively actuate the transverse momentum injection actuators with an actuation pattern to affect the large-scale eddies to modify the drag, fluid mixing, heat transfer, and/or other interactions of the fluid flow with the surface. In various embodiments, the transverse momentum injection actuators may be operated at frequencies less than 10,000 Hertz.

First claim

What is claimed is:

1. A turbulent boundary layer control system, comprising:
an actuator on a surface of an object that is controllable to inject momentum into a turbulent boundary layer of a fluid flowing relative to the surface with a friction Reynolds number, Re τ , greater than 1,500; and
a controller to operate the actuator according to an oscillation period based on a time scale multiplier, T + , of at least 300 to inject momentum into the turbulent boundary layer in a direction transverse to a flow direction of the fluid relative to the surface,
wherein the time scale multiplier, T + , is selected such that the injected momentum modifies large-scale eddies having a range of characteristic time scales exceeding 300η′, where η′ is a viscous time scale of the turbulent boundary layer of the fluid.

2. The system of claim 1 , wherein the time scale multiplier, T + , is expressible as:

T
+

=

1

f
⁢

η
′

,

where η′ is the viscous time scale of the turbulent boundary layer of the fluid and f is an actuation frequency at which the controller operates the actuator.

3. The system of claim 1 , wherein the time scale multiplier, T + , is expressible as:

1

T
+

=

f
*
v

u
τ
2

,

where f is the actuation frequency at which the controller operates the actuator, v is a kinematic viscosity of the fluid, and u τ is a friction velocity.

4. The system of claim 1 , wherein the time scale multiplier, T + , for the oscillation period is selected to have a value of 348 for a fluid flow having a friction Reynolds number, Re τ , of 6000.

5. The system of claim 1 , wherein the time scale multiplier, T + , for the oscillation period is selected to have a value exceeding 600 for fluid flows having friction Reynolds numbers, Re τ , exceeding 10,000.

6. The system of claim 1 , wherein the actuator comprises an actuator of a type selected from the group of actuator types consisting of: a piezoelectric actuator, an electromagnetic actuator, an electromechanical actuator, and a dielectric-barrier discharge (DBD) device.

7. A turbulent boundary layer control system, comprising:
one or more actuators on a surface of an object, wherein each actuator is controllable to inject momentum into a turbulent boundary layer of a fluid flowing relative to the surface with a friction Reynolds number, Re τ , greater than 200; and
a controller to operate the one or more actuators according to an oscillation period based on a time scale multiplier, T + , of at least 150 to inject momentum into the turbulent boundary layer in a direction transverse to a flow direction of the fluid relative to the surface,
wherein the time scale multiplier, T + , is selected such that the injected momentum disrupts large-scale eddies having a range of characteristic time scales exceeding 150η′, where η′ is a viscous time scale of the turbulent boundary layer of the fluid.

8. The system of claim 7 , wherein the time scale multiplier, T + , is expressible as:

T
+

=

1

f
⁢

η
′

,

where η′ is the viscous time scale of the turbulent boundary layer of the fluid and f is an actuation frequency at which the controller operates the actuator.

9. The system of claim 7 , wherein the time scale multiplier, T + , is expressible as:

1

T
+

=

f
*
v

u
τ
2

,

where f is the actuation frequency at which the controller operates the actuator, v is a kinematic viscosity of the fluid, and u τ is a friction velocity.

10. The system of claim 7 , wherein the time scale multiplier, T + , for the oscillation period is selected to have a value of 348 for a fluid flow having a friction Reynolds number, Re τ , of 6000.

11. The system of claim 7 , wherein the time scale multiplier, T + , for the oscillation period is selected to have a value exceeding 600 for fluid flows having friction Reynolds numbers, Re τ , exceeding 10,000.

12. The system of claim 7 , wherein the actuator comprises an actuator of a type selected from the group of actuator types consisting of: a piezoelectric actuator, an electromagnetic actuator, an electromechanical actuator, and a dielectric-barrier discharge (DBD) device.

13. A method to modify heat transfer properties between a fluid and a surface, comprising:
selecting a time scale multiplier, T + , greater than 50 for a viscous time scale, η′, in a turbulent boundary layer of a fluid flowing relative to a surface of an object with a friction Reynolds number, Re τ , greater than 180;
calculating an actuation frequency, f, for injecting momentum along the surface of the object and perpendicular to a direction of fluid flow relative to the surface of the object to disrupt a range of eddies in the turbulent boundary layer with characteristic time scales exceeding 50η′; and
actuating one or more actuators with the calculated actuation frequency, f, to inject momentum perpendicular to the direction of fluid flow to disrupt the range of eddies in the turbulent boundary layer to selectively increase or decrease a rate of heat transfer between the fluid and the surface of the object.

14. The method of claim 13 , wherein the time scale multiplier, T + , is expressible as:

T
+

=

1

f
⁢

η
′

,

where η′ is the viscous time scale of the fluid and f is the actuation frequency.

Assignees

• Deep Science Llc
• Entpr Science Fund Llc

Inventors

• Smits Alexander J
• Marusic Ivan
• Wine David
• Holloway Brian

Classifications

• F15D1/12 Primary

  by influencing the boundary layer · CPC title

• B64C23/005

  by other means not covered by groups B64C23/02 - B64C23/08, e.g. by electric charges, magnetic panels, piezoelectric elements, static charges or ultrasounds · CPC title

• F15D1/007

  comprising surfaces being moved by external supplied energy · CPC title

• F15D1/065

  Whereby an element is dispersed in a pipe over the whole length or whereby several elements are regularly distributed in a pipe · CPC title

• B62D35/00

  Vehicle bodies characterised by streamlining · CPC title