Low Velocity Ratio Transverse Jets Influenced by Concentric Synthetic Jets

  • John Diep
  • Lorenz Sigurdson
Part of the International Centre for Mechanical Sciences book series (CISM, volume 439)


The objective was to discover and evaluate methods of smokestack downwash reduction using unsteady forcing. The flow is essentially a low momentum jet in a crossflow. After preliminary investigations of several concepts, the final wind-tunnel model applies an annular synthetic jet coaxially to a turbulent or laminar pipe flow at the stack exit. The crosswind Reynolds number based on stack diameter is on the order of 1000 to 7000. Primary diagnostics are hot-wire measurements and image processing of smoke flow visualization photographs of the plume gas. For a laminar pipe flow and increasing forcing amplitude, the initially turbulent plume can be made to completely relaminarize and then become turbulent again at higher amplitudes. Therefore an increased forcing does not always increase mixing. At higher amplitudes vortices appear at the forcing frequency. An abrupt transition of the vortices’ arrangement occurs at a particular amplitude that coincides with an apparent jump in mixing. For turbulent pipe flow, plume height increases by as much as 1.8 stack diameters. This data is collapsed using a simple model based on the idea that synthetic jet momentum dominates the plume at high forcing amplitudes.


Velocity Ratio Pipe Flow Force Amplitude Plume Height Plume Rise 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Briggs, G. (1975). Plume rise predictions. In Lectures on Air Pollution and Environmental Impact Analyses. American Meteorological Society. 59–111.Google Scholar
  2. Coward, A. (2000). Personal communications.Google Scholar
  3. Diep, J. and Sigurdson, L. (2001). Cross-jet influenced by a concentric synthetic jet. Physics of Fluids 13 (9): S16.Google Scholar
  4. Diep, J. and Sigurdson, L. (2002). Reduction of smokestack downwash using a concentric synthetic jet. Manuscript submitted for publication.Google Scholar
  5. Fan, L. (1967). Turbulent buoyant jets into stratified or flowing ambient fluids. Technical Report KH-R-15, W.M. Keck Laboratory of Hydraulics and Water Resources.Google Scholar
  6. Hoult, D. and Weil, J. (1972). Turbulent plume in a laminar cross flow. Atmospheric Environment 6: 513–531.CrossRefGoogle Scholar
  7. Johnston, C. (1994). Downwash of stack gas plumes. Master’s thesis, University of Alberta.Google Scholar
  8. Johnston, C. and Wilson, D. (1997). A vortex pair model for plume downwash into stack wakes. Atmospheric Environment 31 (1): 13–20.CrossRefGoogle Scholar
  9. Moussa, Z., Trischka, J., and Eskinazi, S. (1977). The near field in the mixing of a round jet with a cross-stream. Journal of Fluid Mechanics 80 (1): 49–80.CrossRefGoogle Scholar
  10. Overcamp, T. and Hoult, D. (1971). Precipitation in the wake of cooling towers. Atmospheric Environment 5: 751–765.CrossRefGoogle Scholar
  11. Sigurdson, L. (1995). The structure and control of a turbulent reattaching flow. Journal of Fluid Mechanics 298: 139–165.CrossRefGoogle Scholar
  12. Sigurdson, L. and Diep, J. (2001a). Mixing in a cross-jet enhanced by a coaxial annular synthetic jet. Manuscript submitted for publication.Google Scholar
  13. Sigurdson, L. and Diep, J. (2001b). Control of smokestack downwash using a concentric annular synthetic jet. In Bulletin of the American Physical Society 54th Annual Meeting of the Division of Fluid Dynamics, November 18–20, 2001, San Diego, California 46 (10): 46.Google Scholar
  14. Smith, B. and Glezer, A. (1998). The formation and evolution of synthetic jets. Physics of Fluids 10(9):2281–2297.CrossRefzbMATHMathSciNetGoogle Scholar
  15. Snyder, W., and Lawson, R. (1991). Fluid modeling simulation of stack-tip downwash for neutrally buoyant plumes. Atmospheric Environment 25A (12): 2837–2850.Google Scholar
  16. Vadot, L. (1967). Étude de la Diffusion des Panaches de Fumée dans l’Atmosphère. Centre Interprofessionnel Technique d’Études de la Pollution Atmosphérique, Paris.Google Scholar

Copyright information

© Springer-Verlag Wien 2003

Authors and Affiliations

  • John Diep
    • 1
  • Lorenz Sigurdson
    • 1
  1. 1.Vortex Fluid Dynamics Lab, Department of Mechanical EngineeringUniversity of AlbertaCanada

Personalised recommendations