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. VlachosJ. RullanJ. Gibbs

Overview  Background  Facilities and models Experimental tools (PIV, pressure scanners, 7-hole probes)  Results: 1.Aerodynamics of swept wings 2.Flow Control at high alpha 3.CONTROL SEPARATED FLOW (NOT SEPARATION) < 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> 50 0 Sweep~45 0 Sweep~40 0

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 38.7 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 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.) planesz/cz/b planesx/c A0.28 B0.513 C0.746 D1.086

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 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 x1200 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 controlcontrol

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 controlControl

Results (cont.)  Plane 8, t=T/8 No controlControl

Results (cont.)  Plane 8, t=2T/8 No controlControl

Results (cont.)  Plane 8, t=3T/8 No controlControl

Results (cont.)  Plane 8, t=4T/8 No controlControl

Results (cont.)  Plane 8, t=5T/8 No controlControl

Results (cont.)  Plane 8, t=6T/8 No controlControl

Results (cont.)  Plane 8, t=7T/8 No controlControl

Results (cont.)  Plane 9, t=0 No controlControl

Results (cont.)  Plane 9, t=T/8 No controlControl

Results (cont.)  Plane 9, t=2T/8 No controlControl

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 A Plane C Plane D

Circulation Variation (cont.)  Plane C  Plane D

Pressure ports location Spanwise blowing nozzles

ESM Pressure 13 AOA for Station 3  Half flap  Full flap

ESM Pressure 13 AOA for Station 4  Half flap  Full flap

ESM Pressure 13 AOA for Station 5  Half flap  Full flap

ESM Pressure 13 AOA for Station C  Half flap  Full flap

Pressure distributions for α=13 0.  Stations 5-7  Stations 8-10

Pressure distributions for α=17 0.  Stations 5-7  Stations 8-10

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

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