Numerical Simulation and Optimization of Wind Effects of Porous Parapets on Low-Rise Buildings with Flat Roofs

Ye Qiu,Youyi Zhao,Bingbing San

doi:10.1155/2019/3402613

Abstract

This paper presents a procedure to optimize the porosity of parapets to improve the aerodynamic behavior of low-rise buildings with flat roofs, by coupling an optimization algorithm and computational fluid dynamics (CFD) simulations. The performance of solid parapets to decrease the wind suctions on flat roofs induced by conical vortices was firstly studied, based on four turbulence closure models (standard k-ε, RNG k-ε, SST k-ω, and RSM). The simulation results were validated by comparing with the wind tunnel data. Additionally, the porous parapet was treated as a momentum sink in the governing momentum equation, and the RSM turbulence model was employed. As a result, six optimization studies focusing on the highest mean suction minimization that consider parapet height were presented. The aim of this paper is to search for the best performing porosity through an automatic CFD-based optimization methodology. At low relative heights (hp/H = 0.01∼0.05, hp is the parapet height, and H is the roof height), the porous parapet with optimal porosity in between 38.2% and 52.3% seems to be more effective than solid parapets in attenuating high corner suctions generated by conical vortices; however, the solid parapet gives the best performance in the reduction of wind suctions when hp/H ≥ 0.07.

Highlights

Wind loads on flat or low-sloped roofs of low-rise buildings have been evaluated in many wind tunnel investigations
Of particular concern are the worst mean and peak suctions observed on roof corners near the edge for oblique wind directions, where the existence of conical or delta wing vortices is well established at both model scale and full-scale [1]. is phenomenon becomes increasingly important for the design of low industrial buildings, because of their relatively light dead load and flexibility that making them susceptible to wind loads
Stathopoulos et al [5], denoted STA hereafter, has experimentally measured the surface pressure coefficients on flat roofs with solid parapets for the wind direction of 45°. us, in order to validate the possible applicability of the turbulence closure models used later for solving these cases, the mean pressure study results from STA’s experiments are compared

Summary

Introduction

Wind loads on flat or low-sloped roofs of low-rise buildings have been evaluated in many wind tunnel investigations. Pindado and Meseguer [9] conducted tests with six porous parapet types and found that low relative height parapets (hp/H < 0.05) with a medium porosity are more effective than solid parapets to reduce the corner suctions. Several studies by means of computational fluid dynamics (CFD) simulations were carried out to investigate the performance of solid parapets in reducing the roof suctions of low-rise buildings. To the authors’ knowledge, experimental methods using wind tunnel testing or CFD techniques provide the basis of traditional “cut and try” approach for the design of parapets located at roof edges In this approach, several parapets with different porosities or heights are investigated, and the one that yields the best performance in reducing high suctions is identified. The influence of the height of solid parapets on roof surface pressures has been analyzed numerically, and six parapets with relative heights hp/H from 0.01 to 0.13 were selected for the aerodynamic optimization analysis. e implementation of the optimization procedures using gradient algorithm was carried out to find the optimal porosity, which aims at improving the corner suction mitigation performance of parapets early in the design

Numerical Methods

Optimization Methods

Results and Discussions