Numerical simulation of downburst winds

Matthew S. Mason*, Graeme S. Wood, David F. Fletcher

*Corresponding author for this work

    Research output: Contribution to journalArticle

    84 Citations (Scopus)

    Abstract

    The wind field of an intense idealised downburst wind storm has been studied using an axisymmetric, dry, non-hydrostatic numerical sub-cloud model. The downburst driving processes of evaporation and melting have been paramaterized by an imposed cooling source that triggers and sustains a downdraft. The simulated downburst exhibits many characteristics of observed full-scale downburst events, in particular the presence of a primary and counter rotating secondary ring vortex at the leading edge of the diverging front. The counter-rotating vortex is shown to significantly influence the development and structure of the outflow. Numerical forcing and environmental characteristics have been systematically varied to determine the influence on the outflow wind field. Normalised wind structure at the time of peak outflow intensity was generally shown to remain constant for all simulations. Enveloped velocity profiles considering the velocity structure throughout the entire storm event show much more scatter. Assessing the available kinetic energy within each simulated storm event, it is shown that the simulated downburst wind events had significantly less energy available for loading isolated structures when compared with atmospheric boundary layer winds. The discrepancy is shown to be particularly prevalent when wind speeds were integrated over heights representative of tall buildings. A similar analysis for available full scale measurements led to similar findings.

    Original languageEnglish
    Pages (from-to)523-539
    Number of pages17
    JournalJournal of Wind Engineering and Industrial Aerodynamics
    Volume97
    Issue number11-12
    DOIs
    Publication statusPublished - Dec 2009

    Keywords

    • Downburst
    • Microburst
    • Thunderstorm
    • Thunderstorm outflow

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