Physical and numerical modeling of downburst generated gust fronts

This paper presents three different schemes for modeling and analyzing the effects of gust fronts resulting from downbursts on structures. These schemes include: (i) the utilization of a manually controlled, pivoted flat plate that can be rotated to a high angle of incidence in a traditional low speed wind tunnel facility to mimic the kinematics and dynamics of a gust front and to quantify their effects on a series of prismatic models, (ii) simulation of flow past an inclined flat plate using CFD and (iii) generation of a gust front flow field in a multiple fan wind tunnel facility containing individually controlled fans. In these experimental configurations, the inflow profile is tailored to produce an inverted profile, characteristic of outflows from downbursts where velocity maxima is achieved nearer to the ground surface, while also modeling the transient dynamics of a gust front. Results demonstrate that the desired velocity profile can be reproduced within the conventional wind tunnel framework. Pressure measurements on a series of prismatic building models demonstrate the effect of the transient nature of gust front behavior and the subsequent change in pressures over a typical boundary layer flow, identifying key features for future investigations.