An analytical model for simulating steady state flows of downburst

Abstract

Downburst wind events represent the greatest threat to many structural engineering systems due to the extreme wind that they generate. They have been shown to be the cause of many past failures of many structural systems. There are many experimental and numerical models for simulating these types of loads. However, analytical and empirical simulation models are needed to facilitate the analysis of structural systems under these types of loads. There are remarkable disparities between the available analytical models and the recorded field data, experimental and numerical simulations. Added to that, the effects of nonlinear growth of boundary layer thickness are rarely included in these models. This paper presents an analytical model that successfully matches the recorded field data, experimental and numerical results. Two new empirical functions which are able to simulate the radial and vertical profiles of horizontal downburst wind speed have been developed. These two equations have then been implemented into the continuity equation and the vertical and radial profiles of the vertical downburst wind speed have been estimated analytically. Once boundary layer effects have been included in the model, the radius corresponding to maximum wind speed becomes a function of elevation, the height corresponding to maximum wind speed becomes a function of the radial coordinates and the shapes of the speed profiles become changeable with the radial and vertical coordinates.