Electronic Thesis and Dissertation Repository

Degree

Master of Engineering Science

Program

Civil and Environmental Engineering

Supervisor

Hangan,Horia

Abstract

Downbursts are highly transient natural phenomena which produce strong downdrafts evolving from a cumulonimbus cloud They induce an outburst of damaging winds on or near to the ground causing an immense damage to the ground mounted structures and aircrafts. This study investigates the transient nature of downbursts using wind speed records from full scale downburst events employing an objective methodology. This method can detect the abrupt change points in a downburst time series based on statistical parameters such as mean, standard deviation and linear trend. In addition to the analysis of the full scale downburst events, several large scale experimental model downbursts are produced in the Wind Engineering, Energy and Environment (WindEEE) Dome at Western University by varying downdraft jet diameter and jet velocity to comprehensively characterize the downburst flow field. High resolution surface layer data is captured using Cobra probes and dynamics of the downburst vortices is investigated using Particle Image Velocimetry (PIV) Technique. The analysis of wind speed record is carried out deploying the moving mean approach with different averaging times. Statistical analysis on turbulence using reasonable averaging time shows the similarities of experimental model with full scale events. For the first time, an effort has been made to compare the primary vortex structure and its evolution with the limited full scale downburst records obtained using Doppler radar measurements.

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