(06/07) Juliett Davitian has won the AE outstanding M.S. recipient award and Hann Mao has won the AE outstanding B.S. recipient award for 2007. Congratulations!

(06/06) Leo Alves has won the MAE outstanding PhD recipient award and Marcus George has won the AE outstanding MS recipient award for 2006. Congratulations!

(05/06) Ann Karagozian has completed chairing two studies for the Air Force.

(09/05) Juliett Davitian has won a three year NASA Graduate Student Research Program Fellowship, commencing in the Fall of 2005.

(5/05) Ann Karagozian has been appointed the Vice Chair of the Air Force Scientific Advisory Board.

(1/05) Srinivasan Dattarajan MS '02 , PhD '04 won the 2004 Best Student Presentation award from the AIAA Microgravity Technical Committee.

(5/12/04) Sevan Megerian Wins First Place at AIAA Student Conference, 2004.

(8/03) Lydia Treviño featured in UCLA Engineer—

(6/03) Robert Lobbia has received a special scholarship award from Aviation Week & Space Technology—the Next Century of Flight (NCF) award.

Click here for the latest group publications.

Researchers: Prof. Ann Karagozian, Prof. Robert M'Closkey, Prof. Luca Cortelezzi (McGill Univ.), Sevan Megerian (grad), Juliett Davitian (grad), Leonardo Alves(grad), Marcus George (grad), Edson Rodriguez (undergrad), Stepan Shahinian (undergrad), Kristy Dalrymple (undergrad), Dr. Yen-Cheng Chen (postdoc) Research Supported By:   NASA Dryden and National Science Foundation

	Smoke visualization of the transverse jet in crossflow.
	Jon King (right) and Steve Shapiro (left) analyzing fluid structures while photographing the mixing of a transerse jet in crossflow.
	Shown above the animation of a pulsed transverse jet exposed to square wave excitation, with R = Uj / U∞ = 2.58, at a scaled frequency of 0.3 and duty cycle of 10%. (click image to run *.mpg movie file, 10MB)

This project involves examination of the fundamental features of the pulsed or acoustically excited transverse jet, a flowfield which may be applied to fuel injection as well as dilution air injection in aircraft engines, and which can potentially be controlled via active means so as to improve engine efficiency and reduce emissions. Current activities involve: 1) experiments on gas phase jets in crossflow, including instability characterization and open and closed loop controlled acoustic excitation. 2) vortex element simulations of the unforced and forced jet in crossflow with a detailed examination of the evolution of the vortical structures associated with the jet. 3) development of control strategies for optimization of jet behavior. 4) linear stability analysis as well as full 3D Navier-Stokes simulations of reactive and non-reactive transverse jets.

The UCLA combustion laboratory's experiment setup for this project allows for accurate system identification as well as open and closed loop control. A spectrum analyzer is used to extract frequency response of the input signal (speaker voltage) over the output signal (jet velocity). These Bode plots are used to create a plant model of the pulsed jet in crossflow. With the knowledge of the plant model an inverted model is used to create a compensator that gives a new compensated system Bode plot that is both flat in magnitude and matched in phase. Application of this compensator has shown dramatic increases in jet penetration mixing and entrainment. Evaluation of the frequency space (40Hz-3240Hz), different input waveforms (precompensated), and temporal pulse widths have shown that there are perferred conditions under which optimal jet penetration mixing and entrainment occur. Closed loop control strategies are being developed that allow even greater control authority over the jet's temporal waveform.

The 3D vortex element simulations are being performed at McGill University by Prof. Luca Cortelezzi. Resulting simulations have so far been in reasonable agreement with the observed experimental results.

Publications:

1. Optimization of Controlled Jets in Crossflow, Shapiro, S., King, J., M'Closkey, R. T, and Karagozian, A. R., AIAA Journal, Vol. 44, No. 6, pp. 1292-1298, 2006.
   
   
2. Linear Stability Analysis of Jets in Crossflow, Alves, L. S. de B., Kelly, R. E., and Karagozian, A. R., 43rd AIAA Aerospace Sciences Meeting, AIAA Paper AIAA-2005-1118, January, 2005.
   
   
3. Evolution of Shear Layer Instabilities in the Transverse Jet, Megerian, S. and Karagozian, A. R., 43rd AIAA Aerospace Sciences Meeting, AIAA Paper AIAA-2005-0142, January, 2005.
   
   
4. Control of Vorticity Generation in an Acoustically Excited Jet in Crossflow, Karagozian, A. R., Megerian, S., Alves, L, George, M., Kelly, R. E., and M'Closkey, R. T., 43rd AIAA Aerospace Sciences Meeting, Invited AIAA Paper 2005-0303, January, 2005 .
   
   
5. Evolution of Shear Layer Instabilities in the Transverse Jet, Megerian, S. and Karagozian, A. R., AIAA Region VI Student Conference, UCLA, AIAA student paper, FIRST PLACE WINNER M.S. student division, April, 2004.
   
   
6. The Actively Controlled Jet in Crossflow, R.T. M'Closkey, J. King, L. Cortelezzi, A.R. Karagozian, Journal of Fluid Mechanics, Vol. 452, No. 1, p. 325, February, 2002.
   
   
7. On the Formation of the Counter-Rotating Vortex Pair in Transverse Jets, Cortelezzi, L. and Karagozian, A. R., Journal of Fluid Mechanics, Vol. 446, pp. 347-373, November, 2001.
   
   
8. Actively Controlled Transverse Gas Injection, L. Cortelezzi, J. King, R. Lobbia, R.T. M'Closkey, A.R. Karagozian, IEEE Conference on Decision and Control, Invited Paper CDC00-INV4905, December, 2000.