Flow Control over Sharp-Edged Wings

José M. Rullán, Jason Gibbs, Pavlos Vlachos, Demetri Telionis

Dept. of Engineering Science and Mechanics

Flow Control Team

P. Vlachos J. Rullan J. Gibbs

Overview Background Facilities and models Experimental tools (PIV, pressure scanners, 7-hole probes)

Results:1. Aerodynamics of swept wings2. Flow Control at high alpha3. CONTROL SEPARATED FLOW

(NOT SEPARATION)4. 10 4 < Re < 10 6

Conclusions

Background

Diamond-Planform, sharp-edged wings common on today’s fighter aircraft.

Little understanding of aerodynamic effects at sweeping angles between 30° and 40° AOA.

Vorticity Rolling over Swept Leading Edges

Sweep> 500 Sweep~450

Sweep~400 Sweep~400

Background (cont.) Low-sweep wings stall like *unswept wings or *delta wings

Dual vortex structures observed over a wing 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 diamond-planform wing

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 diamond wing

Flow control supplied at inboard half of wing

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

Pressure ports location

Spanwise blowing nozzles

ESM Pressure profiles @ 13 AOA for Station 3

Half flap Full flap

ESM Pressure profiles @ 13 AOA for Station 4

Half flap Full flap

ESM Pressure profiles @ 13 AOA for Station 5

Half flap Full flap

ESM Pressure profiles @ 13 AOA for Station C

Half flap Full flap

Pressure distributions for α=130.

Stations 5-7 Stations 8-10

Pressure distributions for α=170.

Stations 5-7 Stations 8-10

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

Future Work Study effect of sweep with new model Explore the frequency domain Identify local “3-D actuators” to

control these 3-D flow fields Aim at controlling forces and

moments