Numerical simulation of WINDEEE dome downburst for open terrain using physical roughness elements

Abstract eng:
Downburst phenomenon was not experimentally simulated at wind tunnel testing scales until recently through the WINDEEE dome. This ground breaking achievement represents an important milestone for Wind Engineering, where many characteristics of downbursts are explored for the first time, developing the understanding of such nonstationary events and how different they are from ABL flow. The current study reports a numerical simulation that replicates the WINDEEE downburst testing for open terrain. Utilizing the large eddy simulation (LES) turbulence model and adopting the impinging jet model, similar to that applied at WINDEEE dome, simulations were performed for the chosen terrain. The terrain roughness was simulated using physical roughness elements, mimicking the roughness elements used in the actual experiment. These elements were set as part of the domain geometric boundaries to observe their impact on the flow mean and turbulent characteristics. Taking advantage of the unique experimental data available, the current study compares both mean and turbulent characteristics of the simulated downburst in both the time and frequency domains to validate the newly developed numerical tool. Results show similar mean profiles, especially at the peak zones that are studied in more detail. The significance of this study can be clearly viewed in the potentials of using the validated numerical tool to simulate more complex phenomena, such as nonstationary downbursts, on more terrains, as well as to implement different geometric and spatial properties of downbursts to study the impact of the captured wind fields on various structures. INTRODUCTION: Downbursts are events of strong descending downdrafts that result in extreme winds close to the ground level [1]. These events, mainly associated to thunderstorms, are of significance to wind engineers, especially those interested in structural loading. Authors like [2] have acknowledged thunderstorms as being responsible for the majority of damaging high intensity wind events in the North Eastern United States. They also pointed out downbursts as being the governing wind speeds at 10 meters elevation in Australia according to [3]. This was further backed by [4] who mentioned that thunderstorms are responsible for three quarters of peak gust wind speeds outside of hurricane regions in the United States. These findings among others in the stream of wind engineering, have established the need to resolve the featuring characteristics of downburst flows, with special consideration to near ground flows, being the region of interest for structural and wind engineers. Accordingly, researchers have first tried to resolve the flow through the analysis of field measurements. The work done by [5], [6], [7], [8] and [9] is a representative sample of the efforts researchers have dedicated to that approach. Although such work has been an important contributor to our understanding of

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