Physical modelling of a downdraft outflow with a slot jet

  • Lin, W.E. (Department of Mechanical and Materials Engineering, The University of Western Ontario) ;
  • Savory, E. (Department of Mechanical and Materials Engineering, The University of Western Ontario)
  • Received : 2009.09.15
  • Accepted : 2010.03.03
  • Published : 2010.09.25


This article provides a time-resolved characterisation of the wind field in a recently-commissioned, downdraft outflow simulator at The University of Western Ontario. A large slot jet approach to physical simulation was used. The simulator performance was assessed against field observations from a 2002 downdraft outflow near Lubbock, Texas. Outflow wind speed records were decomposed according to classical time series analysis. Length scales, characterising the coarse and fine flow structure, were determined from the time-varying mean and residual components, respectively. The simulated downdraft outflow was approximately 1200 times smaller in spatial extent than the 2002 Lubbock event.


  1. Bendat, J.S. and Piersol, A.G. (1986), Random data: Analysis and measurement procedures, 2nd Edition, John Wiley & Sons, USA.
  2. Choi, E.C.C. and Hidayat F.A. (2002), "Dynamic response of structures to thunderstorm winds", Prog. Struct. Eng. Mater., 4(4), 408-416.
  3. Fujita, T.T. (1981), "Tornadoes and downbursts in the context of generalized planetary scales", J. Atmos. Sci., 38(8), 1511-1534.<1511:TADITC>2.0.CO;2
  4. Fujita, T.T. and Wakimoto, R.M. (1981), "Five scales of airflow associated with a series of downbursts on 16 July 1980", Mon. Weather Rev., 109(7), 1438-1456.<1438:FSOAAW>2.0.CO;2
  5. Holmes, J.D., Hangan, H.M., Schroeder, J.L., Letchford, C.W., and Orwig, K.D. (2008), "A forensic study of the Lubbock-Reese downdraft of 2002", Wind Struct., 11(2), 137-152.
  6. Letchford, C.W. and Chay, M.T. (2002), "Pressure distributions on a cube in a simulated thunderstorm downburst. Part B: moving downburst observations", J. Wind Eng. Ind. Aerod., 90(7), 733-753.
  7. Letchford, C.W., Mans, C. and Chay, M.T. (2002), "Thunderstorms – their importance in wind engineering (a case for the next generation wind tunnel)", J. Wind Eng. Ind. Aerod., 90(12-15), 1415-1433.
  8. Lin, W.E. and Savory, E. (2006), "Large-scale quasi-steady modelling of a downburst outflow using a slot jet", Wind Struct., 9(6), 419-440.
  9. Lin, W.E., Orf, L.G., Savory, E. and Novacco, C. (2007), "Proposed large-scale modelling of the transient features of a downburst outflow", Wind Struct., 10(4), 315-346.
  10. Lin, W.E. (2010), Validation of a novel downdraft outflow simulator: A slot jet wind tunnel, PhD thesis, The University of Western Ontario, Canada.
  11. Mason, M.S., Letchford, C.W. and James, D.L. (2005), "Pulsed wall jet simulation of a stationary thunderstorm downburst, Part A: Physical structure and flow field characterization", J. Wind Eng. Ind. Aerod., 93(7), 557-580.
  12. McConville, A.C., Sterling, M. and Baker, C.J. (2009), "The physical simulation of thunderstorm downbursts using an impinging jet", Wind Struct., 12(2), 133-149.
  13. Orwig, K.D. and Schroeder, J.L. (2007), "Near-surface wind characteristics of extreme thunderstorm outflows", J. Wind Eng. Ind. Aerod., 95(7), 565-584.
  14. Priestley, M.B. (1988), Non-linear and non-stationary time series analysis, Academic Press, London, UK.
  15. Sengupta, A. and Sarkar, P.P. (2008), "Experimental measurement and numerical simulation of an impinging jet with application to thunderstorm microburst winds", J. Wind Eng. Ind. Aerod., 96(3), 345-365.
  16. Wakimoto, R.M. (2001), "Convectively driven high wind events", Meteorol. Monogr., 28(50), 255-298.
  17. Walker, G.R. (1992), "Wind engineering beyond the boundary layer wind tunnel", J. Wind Eng. Ind. Aerod., 41(1-3), 93-104.
  18. Welch, P.D. (1967), "The use of Fast Fourier Transform for the estimation of power spectra: A method based on time averaging over short, modified periodograms", IEEE Trans. Audio Electroacoust., 15(2), 70-73.
  19. White, F.M. (2003), Fluid mechanics, 5th Edition, McGraw Hill, USA.

Cited by

  1. Circumferential analysis of a simulated three-dimensional downburst-producing thunderstorm outflow vol.135, 2014,
  2. The response of an overhead electrical power transmission line to two types of wind forcing vol.100, pp.1, 2012,
  3. Direct numerical simulation of particle-laden plane turbulent wall jet and the influence of Stokes number vol.92, 2017,
  4. Large-eddy simulation of the interaction of wall jets with external stream vol.50, 2014,
  5. Evaluation of RANS and LES turbulence models for simulating a steady 2-D plane wall jet vol.35, pp.1, 2018,