Flow Control over Swept Edges Demetri Telionis Dept. of Engineering Science and Mechanics

Flow Control Team P. VlachosJ. RullanJ. Gibbs

Sharp Leading and Trailing Edges

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

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.

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.

Pressure coefficient distribution for controlled case. Angle of attack 10 . Leading edge excitation. Pressure coefficient distribution for controlled case. Angle of attack 15 . Leading edge excitation.

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

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

ESM Pressure 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