Improved modelling of downburst outflows for wind engineering applications using a cooling source approach

Simulation of a downburst-producing thunderstorm using a very high-resolution three-dimensional cloud model

“…In previous work utilizing the CS approach (e.g., Orf and Anderson, 1999;Vermeire et al, 2011a) for an isolated downburst in a 3D model, a single cold pulse of air neatly descends to the ground and spreads out in an axisymmetric fashion with a single clearly defined roll vortex. Instantaneous wind profiles through the strongest nearsurface winds in these simulations are found slightly lagging a vigorous, clearly defined roll vortex circulation, and this maximum wind velocity can be found along any radius passing above where the center of the axisymmetrically forced downdraft impinges the ground.…”

“…CM1 is a 3D meteorological cloud model designed for studying idealized simulations of meteorological phenomena and is currently being used in meteorological research of downbursts, thunderstorms, squall lines, and hurricanes. The model is designed to run efficiently on massively parallel computer architectures and is flexible enough to carry out idealized simulations in dry environments including impinging jet (Vermeire et al, 2011a) and cooling source (Lin et al, 2007;Vermeire et al, 2011b) downburst simulations, as well as moist environment simulations which model the genesis and evolution of severe thunderstorms (e.g., James and Markowski, 2010).…”

“…Near-ground winds have been studied using this model in order to better understand the wind-loading characteristics of downbursts on structures (e.g., Letchford and Chay, 2002;Kim and Hangan, 2007). While the IJ model produces a downburst structure which is approximately visually similar to observations and cloud model simulations, the CS approach has been found to much better capture the physics of a downburst event (Vermeire et al, 2011a). The IJ model was found to contain unrealistic forcing parameters and, by its very nature, to be unable to account for baroclinically generated horizontal vorticity known to be essential in producing physically realistic density driven outflows.…”

Dynamic Response of Flat Roofs Subjected to Non-Stationary Moving Microbursts

“…Sub-cloud model was also adopted by Mason et al (2010) to simulate the stationary and translating/moving downburst. Based on computational-fluiddynamics (CFD) simulation, Vermeire et al (2011) compared the results obtained via the cooling source model with those via the impinging jet model. It is pointed out that the impinging jet model is not capable of accurately capturing the non-dimensional vorticity term from the cooling source results, and the impinging jet consistently over-predicts the magnitude of both Engineering Applications of Computational Fluid Mechanics Vol.…”

Investigating the impact of atmospheric stability on thunderstorm outflow winds and turbulence

“…RANS simulations of downburst winds (Mason et al, 2009;Proctor, 1988;Mason et al, 2010a) and LES studies (Vermeire et al, 2011a;Anabor et al, 2011;Orf et al, 2012Orf et al, , 2014 both solve the Navier-Stokes equations and have been used to 15 study the dynamics of downburst winds. What separates the two methods is that RANS models estimate the entire turbulent contributions of the flow field, while LES resolves the largest turbulent eddies and parameterizes only the smaller turbulent eddies.…”