INTRODUCTION

Wind Driven Rain (WDR) occurs when wind and rain both occur simultaneously. It is very important to study the effect of WDR on building façade as the rain penetration in the walls/windows of the building may lead to building envelope failure. This further leads to direct effect on durability of building façade. CFD helps in predicting the amount of rainfall for various wind directions & droplet sizes beforehand and hence helps in defining the preventive measures which can be incorporated at construction stage of building itself.

CHALLENGES

• To simulate the large volume which require very huge computational resources.
• Modeling and meshing of building CFD domain with number of components such as windows on each floor, façade of each floor, etc.
• Modeling multiphase (DPM) for taking into effect of water droplets.
• To estimate the catch ratio for various droplet sizes.
• To estimate amount of rainfall hitting building façade for different wind directions.
• Post-processing large amount of information and extracting relevant information for design analysis.

THE SOLUTION

WDR analysis of building structure is quite challenging due to the higher number of windows at each floor & more number of floors in building CFD domain. Mesh was manually controlled to keep the mesh count within limits and at the same time capture the critical regions under consideration. CFD analysis of wind driven rain for high rise building was carried for various wind flow direction conditions and rain droplet sizes. For all these iterations catch ratio and amount of rainfall hitting on the walls and windows were predicted. Based on the CFD WDR analysis results, overhangs were suggested for improving raindrop trajectories over windward façade.

BENEFITS

• Prediction of Catch ratio.
• Visualization of amount of rainfall hitting walls/windows for various sizes of droplets
• Design modifications are easy for prediction to reduce the effect of WDR on wall/window seepages.