Field measurements of wind-driven rain: verification and expansion of site wind conditions

Abstract eng:
Wind-Driven Rain (WDR) is known to be a major source of moisture loads on building envelopes and has caused numerous cases of building envelope failures. A six-storey building with a flat roof located in Vancouver, British Columbia, Canada was instrumented for field WDR measurements. On-site weather conditions including wind speed, wind direction and horizontal rainfall were measured by a weather station located on the rooftop of the building. The WDR on façade was simultaneously measured using customized driving rain gauges placed on strategically selected locations to represent the expected WDR wetting pattern of façade. The wind speed over the roof top where the anemometer was located and in front but close to the building façade was measured on a 1:400-scaled model of the building with and without surroundings placed in an atmospheric boundary layer wind tunnel, in order to verify the on-site wind measurements and upstream terrain roughness. A suburban terrain was simulated in the wind tunnel and the wind profiles above the rooftop were measured. The wind tunnel measurements showed that for the stand-alone building, the wind speed at the anemometer height was increased by 12% compared to a power law predicted wind profile with a suburban terrain, while for the building with surroundings, the wind speed measured at the anemometer height fits well with the power law profile. The wind speed measured on-site and the wind speed generated by converting the wind speed measured at a nearby airport weather station (using the power law with the suburban terrain) also showed good agreement. This paper presents the wind tunnel setup, results obtained and comparisons with field measurements. Discussions on the proper on-site location of wind instruments for good WDR measurements are also included in the paper. INTRODUCTION Wind-driven rain (WDR) is one of the most important environmental loads and the main moisture source that affects the hygrothermal performance and durability of building envelopes [1-2]. The quantity and spatial distribution of WDR is affected by a wide range of parameters including wind speed, wind direction, rainfall intensity, wind angle, building geometry, location on building facades, and surrounding topography. WDR loads on facades are normally determined or estimated by measurements, semi-empirical correlations, and Computational Fluid Dynamics (CFD) modelling. Each approach has its advantages and limitations [2]. Measurements have always been the primary tool for WDR study and provide the basic knowledge for understanding WDR, but they can be time consuming, expensive, and suffer from large errors [2-4]. Their use for the estimation of WDR load can be limited to the specific site where measurements were taken. These limitations motivated

• Export as: BibTeX | MARC | MARCXML | DC | EndNote | NLM | RefWorks
• Add to your basket