Hashemi-Tari P, Gurka R, Hangan H (2010) Experimental investigation of tornado-like vortex dynamics with swirl ratio: the mean and turbulent flow fields. Haan FL, Sarkar PP, Gallus WA (2008) Design, construction and performance of a large tornado simulator for wind engineering applications. American meterology Society, Boston, Mass, pp 208–213įujita TT (1976) Graphic examples of tornadoes. In: Prepints, 7th Conference on severe local storms. Weatherwise 23:160–173įujita TT (1971) Proposed mechanism of suction spots accompanied by tornadoes. Meas Sci Technol 13:1058–1071įujita TT (1970) The Lubbock tornadoes: a study of suction spots. Exp Fluids 39:1040–1050įoucaut JM, Stanislas M (2002) Some considerations on the accuracy and frequency response of some derivative filters applied to particle image velocimetry vector fields. American Geophysical Union, Washington, DC, pp 557–571Įtebari A, Vlachos PP (2005) Improvements on the accuracy of derivative estimation from DPIV velocity measurements. In: Church C et al (ed) The tornado: its structure, dynamics, prediction, and hazards. University of Oklahoma Press, Norman, pp 197–236ĭoswell CA III, Weiss SJ, Johns RH (1993) Tornado forecasting: a review. In: Kessler E (ed) Thunderstorms morphology and dynamics, ver. J Atmos Sci 36:1755–1776ĭavies-Jones RP (1973) The dependence of core radius on swirl ratio in a tornado simulator. Bull Am Meteorol Soc 58:900–908Ĭhurch CR, Snow JT, Baker GL, Agee EM (1979) Characteristics of tornado-like vortices as a function of swirl ratio: a laboratory investigation. American Geophysical Union, Washington, DC, pp 277–295Ĭhurch CR, Snow JT, Agee EM (1977) Tornado vortex simulation at Purdue University. In: Church C, Burgess D, Doswell C, Davies-Jones R (eds) The tornado: its structure, dynamics, prediction, and hazards. American Geophysical Union, Washington, DC, pp 319–352Ĭhurch CR, Snow JT (1993) Laboratory models of tornadoes. Master’s thesis, Miami University, Oxford, Ohioīluestein HB, Golden JH (1993) A review of tornado observations. thesis, Purdue University, West Lafayette, Indianaīeer CP (2006) Analysis of velocity data to determine the structure of tornado-like vortices. It would be helpful in improving the understanding of the interaction between the tornado-like vortex structure and the ground surface, ultimately leading to better predictions of tornado-induced wind loads on civil structures.īaker GL (1981) Boundary layers in laminar vortex flows. This work provides detailed characterization of the tornado-like vortex structure, which has not been fully revealed in previous field studies and laboratory simulations. The intensified mean flow and enhanced turbulence at the ground level, correlated with the ground-vortex interaction, may cause dramatic damage of the civil structures in tornadoes. Here, the results show that not only the intensified mean flow but greatly enhanced turbulence occurs near the surface in the tornado-like vortex flow. The maximum velocity variance is about twice at the high swirl ratio (θ v = 45°) that at the low swirl ratio (θ v = 15°), which is contributed significantly by the multiple small-scale secondary vortices. The tangential velocity, as the dominant velocity component, has the peak value about three times that of the maximum radial velocity regardless of the swirl ratio. We quantified the effects of vortex wandering on the mean flow and found that vortex wandering was important and should be taken into account in the low swirl ratio case. We observed two distinct vortex structures: a single-celled vortex at the lowest swirl ratio ( S = 0.03, θ v = 15°) and multiple suction vortices rotating around the primary vortex (two-celled vortex) at higher swirl ratios ( S = 0.1–0.3, θ v = 30°–60°). Complicated near-ground flow was measured in two orthogonal views: horizontal planes at various elevations ( z = 11, 26 and 53 mm above the ground) and the meridian plane. We simulated tornado-like vortex flow at the swirl ratios of S = 0.03–0.3 (vane angle θ v = 15°–60°), using a laboratory tornado simulator and investigated the near-ground-vortex structure by particle imaging velocimetry. The near-ground flow structure of tornadoes is of utmost interest because it determines how and to what extent civil structures could get damaged in tornado events.
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