Flow Control over Swept Edges

Demetri Telionis

Dept. of Engineering Science and Mechanics

Flow Control Team

P. Vlachos J. Rullan J. Gibbs

Sharp Leading and Trailing Edges

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

x/c

Cp

40°30°25°20°15°10°

Pressure coefficient distribution at different angles of attack. No actuation.

20 40 60 80 100 120 140 160 180 2000

500

1000

1500

2000

2500

Hz

Pow

er S

pect

rum

40° Pk: 25.5 - 51 30° Pk::34.75 - 69.525° Pk: 42.5 - 85

20 40 60 80 100 120 140 160 180 2000

50

100

150

200

250

Hz

Pow

er S

pect

rum

20°..Pk: 56 15° Pk: :6610° Pk: N/A

Power Spectra of Wake Velocity

Normal force coefficient variation with excitation frequency. Angle of attack: 20; leading edge flap actuation; trailing edge flap actuation.

Strouhal number variation with excitation frequency. Angle of attack: 20; leading edge flap actuation; trailing edge flap actuation.

Normal force coefficient variation with excitation frequency. Angle of attack:15; leading edge flap actuation.

Strouhal number variation with excitation frequency. Angle of attack: 15; leading edge flap actuation.

Normal force coefficient variation with excitation frequency. Angle of attack:10;leading edge flap actuation.

Strouhal number variation with excitation frequency. Angle of attack: 10;leading edge flap actuation.

20 40 60 80 100 120 140 160 180 2000

200

400

600

800

1000

1200

Hz

Pow

er S

pect

rum

Fa=0 Pk: 34.75 - 69.5

Fa=72.25 Pk: 72.25 - 35.5

20 40 60 80 100 120 140 160 180 2000

100

200

300

400

500

600

700

800

Hz

Pow

er S

pect

rum

Fa=0 Pk: 42.75 - 85.5

Fa=74.5 Pk: 74.5 - 27.5

PSD of Pitot 3 at excitation |F|=2.06. Angle of attack 30

PSD of Pitot 3 at excitation |F|=1.75.Angle of attack 25. Pk: peaks.

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

-1.5

-1

-0.5

0

0.5

1

x/c

Cp

|F|=0 Cn : -0.573

|F|=0.5 Cn : -0.770

|F|=0.77 Cn : -0.996

|F|=1 Cn : -0.950

|F|=1.5 Cn : -0.954

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

-2

-1.5

-1

-0.5

0

0.5

1

x/c

Cp

F=0 Cn : -0.632 F=47.5 Cn : -0.792F=90 Cn :-0.678 F=105 Cn : -0.719

Pressure coefficient distribution for controlled case. Angle of attack 10. Leading edge excitation.

Pressure coefficient distribution forcontrolled case. Angle of attack 15. Leadingedge excitation.

Vorticity Rolling over Swept Leading Edges

Sweep> 500 Sweep~450

Sweep~400 Sweep~400

Background (cont.) Low-sweep edges stall like *unswept edges or *highly-swept edges

Dual vortex structures observed over an edge swept by 50 degrees at Re=2.6X104 (From

Gordnier and Visbal 2005)

Yaniktepe and Rockwell

Sweep angle 38.7º for triangular planform Flow appears to be

dominated by delta wing vortices

Interrogation only at planes normal to flow

Low Re number~10000 Control by small

oscillations of entire wing

Facilities and models

VA Tech Stability Wind Tunnel

U∞=40-60 m/s Re≈1,200,000

44” span, 42 degrees swept edge

Facilities and models

Water Tunnel with U∞=0.25 m/s Re≈30000

CCD camera synchronized with Nd:YAG pulsing laser

Actuating at shedding frequency

Wind Tunnel Model

Model is hollow.

Leading edge slot for pulsing jet

8” span, 40 degrees swept edge

Flow control supplied at inboard half model

Facilities and models(cont.)

planes z/c z/b

1 0.068 0.092

2 0.156 0.209

3 0.249 0.334

4 0.340 0.456

5 0.417 0.559

6 0.467 0.626

7 0.531 0.711

8 0.581 0.778

9 0.644 0.863

10 0.694 0.930

planes x/c

A 0.28

B 0.513

C 0.746

D 1.086

Data acquisition with enhanced time and space resolution ( > 1000 fps)Image Pre-Processing and Enhancement to Increase signal qualityVelocity Evaluation Methodology with accuracy better than 0.05 pixels and space resolution in the order of 4 pixels

Sneak Preview of Our DPIV System

Time-Resolved DPIV

DPIV Digital Particle Image Velocimetry System

III Conventional Stereo-DPIV system with: 30 Hz repetition rate (< 30 Hz) 50 mJ/pulse

dual-head laser 2 1Kx1K pixel cameras

Time-Resolved Digital Particle Image Velocimetry System I An ACL 45 copper-vapor laser with 55W and

3-30KHz pulsing rate and output power from 5-10mJ/pulse

Two Phantom-IV digital cameras that deliver up to 30,000 fps with adjustable resolution while with the maximum resolution of 512x512 the sampling rate is 1000 frme/sec

Time-Resolved Digital Particle Image Velocimetry System II : A 50W 0-30kHz 2-25mJ/pulse Nd:Yag Three IDT v. 4.0 cameras with 1280x1024

pixels resolution and 1-10kHz sampling rate kHz frame-straddling (double-pulsing) with as little as 1 msec between pulses

Under Development: Time Resolved Stereo DPIV with Dual-head

laser 0-30kHz 50mJ/pulse 2 1600x1200 time resolved cameras …with build-in 4th generation intensifiers

Actuation Time instants of pulsed jet(a)

(b)

(c)

PIV Results Velocity vectors and vorticity contours

along Plane D

no control control

PIV results (cont.) Planes 2(z/b= 0.209) and 3

(z/b= 0.334) with actuation.

Plane 2 Plane 3

Results (cont.) Plane A, control, t=0,t=T/8

Results (cont.) Plane A, control, t=2T/8,t=3T/8

Results (cont.) Plane A, control, t=4T/8,t=5T/8

Results (cont.) Plane A, control, t=6T/8,t=7T/8

Results (cont.) Plane 8, t=0

No control Control

Results (cont.) Plane 8, t=T/8

No control Control

Results (cont.) Plane 8, t=2T/8

No control Control

Results (cont.) Plane 8, t=3T/8

No control Control

Results (cont.) Plane 8, t=4T/8

No control Control

Results (cont.) Plane 8, t=5T/8

No control Control

Results (cont.) Plane 8, t=6T/8

No control Control

Results (cont.) Plane 8, t=7T/8

No control Control

Results (cont.) Plane 9, t=0

No control Control

Results (cont.) Plane 9, t=T/8

No control Control

Results (cont.) Plane 9, t=2T/8

No control Control

Results (cont.) Planes B and C, control

Results (cont.) Plane D, no control and control

Flow animation for Treft planes

Circulation variation over one cycle

Plane A Plane B

Plane B

Plane A

Plane C

Plane D

Circulation Variation (cont.)

Plane C Plane D

ESM Pressure profiles @ 13 AOA for Station 3

Half flap Full flap

ESM Pressure profiles @ 13 AOA for Station 4

Half flap Full flap

ConclusionsWITH ACTUATION: Dual vortical patterns are activated and

periodically emerge downstream Vortical patterns are managed over the wing Suction increases with control Oscillating mini-flaps and pulsed jets equally

effective Flow is better organized Steady point spanwise blowing has potential