Control of Coaxial Jets by an Azimuthal Excitation: Vortex Dynamic and Mixing Properties (original) (raw)

Abstract

The goal of this work is to improve the mixing properties of a coaxial jet with moderate Reynolds number by active control. Two direct numerical simulations of coaxial jets are performed. First, studying a "natural" (without deterministic control) coaxial jet, we show that the appearance of counter-rotating pairs of streamwise vortices allows ejections from the seeding regions. This initiates the turbulent mixing. However spots of unmixed fluids persist at the end of the computational domain. We use then deterministic perturbation to allow an improvement of the mixing properties of the jet. The deterministic perturbation has an azimuthal part which forces the appearance of pairs of streamwise vortices. Finally, we found a real improvement of the mixing properties with a good homogeneity at the end of the computational domain due to a quicker appearance of small scales.

Loading...

Loading Preview

Sorry, preview is currently unavailable. You can download the paper by clicking the button above.

References (10)

  1. Angele, K., Kurimoto, N., Suzuki, Y., and Kasagi, N., 2006, "Evolution of the streamwise vortices in coaxial jet controlled with micro flap actuators", J. of Turbulence, 7(73):1-19.
  2. Balarac, G., and Métais, O., 2004, "Coherent vortices in coaxial jets", Advances in Turbulence X, H.I. Anderson and P.-Å. Krogstad editors (CIMNE, Barcelona). Balarac, G., and Métais, O., 2005, "The near field of coaxial jets : A numerical study", Phys. Fluids, 17 (065102):1-14.
  3. Balarac, G., Si-Ameur, M., Lesieur, M., and Métais, O., 2007, "Direct numerical simulations of high velocity ratio coaxial jets: Mixing properties and influence of the upstream conditions", J. of Turbulence, 8(21):1-27. Bernal, L. P., and Roshko, A., 1986, "Streamwise vortex structure in plane mixing layers", J. Fluid Mech., 170:449- 525. Champagne, F. H., and Wygnanski, I. J., 1971, "An ex- perimental investigation of coaxial turbulent jets", Int. J. Heat Mass Transfer, 14:1445-1464.
  4. Crow, S. C., and Champagne, F. H., 1971, "Orderly structure in jet turbulence", J. Fluid Mech., 48:547-591.
  5. Dahm, W. J. A., Frieler, C. E., and Tryggvason, G., 1992, "Vortex structure and dynamics in the near field of a coaxial jet", J. Fluid Mech., 241:371-402.
  6. Hunt, J. C. R., Wray, A. A., and Moin, P., 1988 "Eddies, stream, and convergence zones in turbulent flows" Annual Research Briefs, CTR, Stanford University. Liepmann, D., and Gharib., M., 1992, "The role of the streamwise vorticity in the near-field entrainment of a round jet", J. Fluid Mech., 245:643-668.
  7. Pickett, L. M., and Ghandhi, J. B., 2002, "Passive scalar mixing in a planar shear layer with laminar and turbulent inlet conditions", Phys. Fluids, 14(3):985-998.
  8. da Silva, C. B., Balarac, G., and Métais, O., 2003, "Tran- sition in high velocity ratio coaxial jets analysed from direct numerical simulations", J. of Turbulence, 4(24):1-18. da Silva, C. B., and Métais O., 2002a, "On the influ- ence of coherent structures upon interscale interactions in turbulent plane jets", J. Fluid Mech., 473:103-145. da Silva, C. B., and Métais O., 2002b, "Vortex con- trol of bifurcating jets: a numerical study", Phys. Fluids, 14(11):3798-3819.
  9. Villermaux, E., and Rehab, H., 2000, "Mixing in coaxial jets", J. Fluid Mech., 425:161-185.
  10. Warda, H. A., Kassab, S. Z., Elshorbagy, K. A., and Elsaadawy, E. A., 1999, "An experimental investigation of the near-field region of a free turbulent coaxial jet using LDA", Flow Measurement and Instrumentation, 10:15-26.