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

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

-2.5

-2 -1.5

-1 -0.5

0 0.5

1 1.5

0 0.1

0.2

0.3

0.4

0.5

x/c 0.6

0.7

0.8

40° 30° 25° 20° 15° 10° 0.9

1

2500 2000 1500

Power Spectra of Wake Velocity

250 40° Pk: 25.5 - 51 30° Pk::34.75 - 69.5

25° Pk: 42.5 - 85 200 150 20°..Pk: 56 15° Pk: :66 10° Pk: N/A 1000 500 100 50 0 20 40 60 80 100 Hz 120 140 160 180 200 0 20 40 60 80 100 Hz 120 140 160 180 200

1.4

1.3

2.5

2 1.2

1.5

1.1

1 0.5

1 0.9

0 0 0 0.5

1

|F|

1.5

2 0.5

1

|F|

1.5

2

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.

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1 0.9

0 1.2

1 0.8

0.6

0.4

0.2

0.2

0.4

0.6

0.8

|F|

1 1.2

1.4

1.6

0 0 0.5

1 1.5

|F| 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.

1.3

1.2

1.1

1 0.9

0 20 40 60

|F|

80 100

Normal force coefficient variation with excitation frequency. Angle of attack: 10



;leading edge flap actuation.

120 2 1 0 0 9 8 7 4 3 6 5 20 40 60

|F|

80 100 120

Strouhal number variation with excitation frequency. Angle of attack: 10



; leading edge flap actuation.

1200 1000 800 600 400 200 F a =0 Pk: 34.75 - 69.5 F a =72.25 Pk: 72.25 - 35.5

0 20 40 60 80 100 Hz 120 140 160 180 200

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

 800 700 600 F F a a =0 Pk: 42.75 - 85.5 =74.5 Pk: 74.5 - 27.5

500 400 300 200 100 0 20 40 60 80 100 Hz 120 140 160 180 200

PSD of Pitot 3 at excitation |F|=1.75.

Angle of attack 25



. Pk: peaks.

-1.5

-2 -1.5

F=0 Cn : -0.632 F=47.5 Cn : -0.792

F=90 Cn :-0.678 F=105 Cn : -0.719 -1 -0.5

0 0.5

1 0 0.1

0.2

0.3

0.4

0.5

x/c 0.6

|F|=0 C n : -0.573 |F|=0.5 C n : -0.770 |F|=0.77 C n : -0.996

|F|=1 C n : -0.950 |F|=1.5 C n : -0.954 0.7

0.8

0.9

1 -1 -0.5

0 0.5

1 0 0.1

0.2

0.3

0.4

0.5

x/c 0.6

0.7

0.8

0.9

1

Pressure coefficient distribution for controlled case. Angle of attack 15



. Leading edge excitation .

Pressure coefficient distribution for controlled case. Angle of attack 10



. Leading edge excitation.

Vorticity Rolling over Swept Leading Edges Sweep> 50 0 Sweep~45 0 Sweep~40 0 Sweep~40 0

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 38.7

º 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 1 2 3 4 5 6 7 8 9 10 planes A B C D z/c 0.068

0.156

0.249

0.340

0.417

0.467

0.531

0.581

0.644

0.694

x/c 0.28

0.513

0.746

1.086

z/b 0.092

0.209

0.334

0.456

0.559

0.626

0.711

0.778

0.863

0.930

Time-Resolved DPIV

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

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

(b) (c) (a) 

Actuation

Time instants of pulsed jet

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 C Plane D Plane A Plane B

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

Conclusions

WITH 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