Method and apparatus for controlling turbulence in boundary layer and other wall-bounded fluid flow fields

• US 5,797,414 A
• Filed: 06/25/1997
• Issued: 08/25/1998
• Est. Priority Date: 02/13/1995
• Status: Expired due to Fees

• Current Assignee: Orlev Scientific Computing Limited
• Original Assignee: Orlev Scientific Computing Limited
• Inventors: Sirovich, Lawrence, Bronicki, Lucien Y., Levich, Eugene
• Primary Examiner(s): CHAMBERS, A MICHAEL
• Application Number:
  US08/903,190
• Time in Patent Office: 426 Days
• Field of Search: 137/13, 137/828, 137/833, 244/200
• US Class Current: 137/13
• CPC Class Codes: B64C 21/10 using other surface properties, e.g. roughness
• CPC Class Codes: B64C 2230/02 by using acoustic waves generated by transducers
• CPC Class Codes: 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
• CPC Class Codes: F15D 1/003 comprising surface features, e.g. indentations or protrusions F15D1/0055, F15D1/006 take precedence
• CPC Class Codes: F15D 1/06 by influencing the boundary layer use of materials, e.g. to reduce surface friction C09K3/00
• CPC Class Codes: F15D 1/12 by influencing the boundary layer use of materials, e.g. to reduce surface friction C09K3/00
• CPC Class Codes: Y02T 50/10 Drag reduction
• CPC Class Codes: Y10T 137/0391 Affecting flow by the addition of material or energy
• CPC Class Codes: Y10T 137/2196 Acoustical or thermal energy
• CPC Class Codes: Y10T 137/2224 Structure of body of device

Abstract

Turbulence is controlled in boundary layer or wall-bounded fluid flow fields having a turbulent wall region characterized by a system of roll pairs extending in the direction of flow, and obliquely propagating structures interacting with the system of roll pairs, by locally introducing into the turbulent wall region two separate disturbances that are effective to produce, in a local region, a composite disturbance field that is strongly coupled to and modifies the obliquely propagating structures in a manner that increases or decreases the interaction of the propagating structures with the system of roll pairs thereby locally increasing or decreasing the turbulence in the flow field. One of the disturbances may result from the interaction of the fluid with a linear strip, or an array of strips, of delta-shaped protrusions positioned spanwise on the wall (i.e., transverse to the flow direction); and the second disturbance may result from injecting sonic energy into the local region. Furthermore, a linear strip or an array of airfoil shaped protrusions can be used for producing a pair of counter rotating rolls for controlling turbulence in the boundary layer.

Claims

1. A method for controlling turbulence in boundary layer or other wall-bounded fluid flow fields having a turbulent wall region characterized by a system of roll pairs or steaks whose diameter is functionally related to the strength of the flow, and which extend in the direction of flow, and by propagating structures of coherent patterns that propagate obliquely to the direction of flow at a substantially constant group speed, said method including using a linear, or two dimensional array of fine-scale mechanical systems capable of controlled mechanical motion to introduce into the turbulent wall region disturbances that are effective in said region to produce a composite disturbance field having a component due to the static presence of said systems and a component due to their controlled mechanical motion, said composite field being strongly coupled to and modifying the obliquely propagating structures in a manner that increases or decreases the interaction of the propagating structures with the system of roll pairs for locally increasing or decreasing the turbulence in the flow field.

2. A method according to claim 1 wherein said fine scale mechanical systems are micro-electro-mechanical systems (MEMS).

3. A method according to claim 2 wherein said micro-electro-mechanical systems are mounted in a surface that defines said wall-bounded fluid flow field.

4. A method according to claim 1 wherein said fine scale mechanical systems are micro-thermo-mechanical systems.

5. A method according to claim 4 wherein said micro-thermo-mechanical systems are mounted in a surface that defines said wall-bounded fluid flow field.

6. A method according to claim 1 wherein said fine scale mechanical systems are micro-acoustic-mechanical systems.

7. A method according to claim 6 wherein said micro-acoustic-mechanical systems are mounted in a surface that defines said wall-bounded fluid flow field.

8. A method according to claim 1 wherein said fine scale mechanical systems are vibratable diaphragms or membranes.

9. A method according to claim 8 wherein said vibratable diaphragms or membranes are mounted in a surface that defines said wall-bounded fluid flow field.

10. Apparatus for controlling turbulence in boundary layer or other wall-bounded fluid flow fields having a turbulent wall region characterized by a system of roll pairs or streaks whose diameter is functionally related to the strength of the flow, and which extend in the direction of flow, and by propagating structures of coherent patterns that propagate obliquely to the direction of flow at a substantially constant group speed, said apparatus including a linear, or two dimensional, array of fine-scale mechanical systems capable of controlled mechanical motion in response to actuation, and drivers to actuate said fine-scale mechanical systems for introducing into the turbulent wall region disturbances that are effective in said region to produce a composite disturbance field having a component due to the static presence of said systems and a component due to their controlled mechanical motion, said composite field being strongly coupled to and modifying the obliquely propagating structures in a manner that increases or decreases the interaction of the propagating structures with the system of roll pairs for locally increasing or decreasing the turbulence in the flow field.

11. Apparatus for controlling turbulence in boundary layer or other wall-bounded fluid flow field having a turbulent wall region characterized by a system of roll pairs or steaks whose diameter is functionally related to the strength of the flow, and which extend in the direction of flow, and by propagating structures of coherent patterns that propagate obliquely to the direction of flow at a substantially constant group speed, said apparatus including:

a) an array of sensors in operative relationship with said field for sensing the level of turbulence in said region;

b) means connected to said sensors for detecting changes in the level of turbulence in said region, and producing an output when the change exceeds a threshold;

d) a linear, or two dimensional, array of actuatable fine-scale mechanical systems capable of controlled mechanical motion, said systems being in operative relationship with said region; and

e) means to actuate said fine-scale mechanical systems in response to said output for introducing into the turbulent wall region disturbances that are effective in said region to produce a composite disturbance field having a component due to the static presence of said systems and a component due to their controlled mechanical motion, said composite field being strongly coupled to and modifying the obliquely propagating structures in a manner that reduces changes in the level of turbulence in said flow field by increasing or decreasing the interaction of the propagating structures with the system of roll pairs for locally increasing or decreasing the turbulence in the flow field.

12. Apparatus according to claim 11 wherein said fine scale mechanical systems are micro-electro-mechanical systems (MEMS).

13. Apparatus according to claim 12 wherein said micro-electro-mechanical systems are mounted in a surface that defines said wall-bounded fluid flow field.

14. Apparatus according to claim 11 wherein said fine scale mechanical systems are micro-thermo-mechanical systems.

15. Apparatus according to claim 14 wherein said micro-thermo-mechanical systems are mounted in a surface that defines said wall-bounded fluid flow field.

16. Apparatus according to claim 11 wherein said fine scale mechanical systems are micro-acoustic-mechanical systems.

17. Apparatus according to claim 16 wherein said micro-acoustic-mechanical systems are mounted in a surface that defines said wall-bounded fluid flow field.

18. Apparatus according to claim 11 wherein said fine scale mechanical systems are vibratable diaphragms or membranes.

19. Apparatus for controlling turbulence in boundary layer or other wall-bounded fluid flow field comprising:

a) a two dimensional, array of active, actuatable fine-scale mechanical systems capable of controlled mechanical motion in response to actuation, said systems being in operative relationship with said region;

b) said systems being spaced apart in a direction normal to the direction of the flow field a distance in the range 100-200 wall units, a wall unit being equal to m/(sr)^1/2 where m is the viscosity of the fluid, s is the average frictional stress at the wall, and r is the density of the fluid; and

c) means to actuate said fine-scale mechanical systems for producing a composite disturbance field having a component due to the static presence of said systems and a component due to their controlled mechanical motion.

20. Apparatus according to claim 19 including:

a) an array of sensors in operative relationship with said field for sensing the level of turbulence in said region;

b) means connected to said sensors for detecting changes in the level of turbulence in said region, and producing an output when the change exceeds a threshold;

c) means to actuate said fine-scale mechanical systems in response to said output for introducing said composite disturbance into the turbulent wall region.