Spreading, splashing and bouncing of wind-driven raindrops on building facades

Wind-driven rain (WDR) significantly affects buildings. Examples are the durability of building walls, the weathering and soiling of buildings and monuments, algae formation at building facades, mould growth at inside wall surfaces, indoor climate and energy consumption of buildings. In numerical simulation models to analyse the hygrothermal performance of building components, the WDR intensity on a building facade is traditionally implemented as a (uniform) moisture flux boundary condition. In reality however, WDR is the sum of individual raindrops, which do not only spread, but may also splash or bounce off the facade. In this paper, these phenomena, i.e. spreading, splashing and bouncing and their potential occurrence at raindrop impact on building facades are investigated. Laboratory measurements were made of water drop impact on a dry, clean and relatively smooth porous ceramic brick surface. Results show that—depending on impact angle, impact speed and diameter—raindrops impinging on porous material surfaces can show either spreading, splashing or bouncing, which results in variable shapes and sizes of wetted areas. The possibility and importance of splashing and bouncing at the windward facade of a building are investigated by combining the drop impact measurements with computational fluid dynamics (CFD) simulations of raindrop trajectories impinging on the windward building facade of a 10 × 10 × 10 m3 cubic building. It is shown that depending on the meteorological conditions, splashing and bouncing can occur at large parts of the facade. This implies that the current implementation of WDR as a boundary condition in numerical hygrothermal simulation models, which does not take into account these effects, can significantly overestimate the real moisture flux boundary condition

Fatty kidney: emerging role of ectopic lipid in obesity-related renal disease

Nephrolog

Body mass index and complications following major gastrointestinal surgery: A prospective, international cohort study and meta-analysis

Aim Previous studies reported conflicting evidence on the effects of obesity on outcomes after gastrointestinal surgery. The aims of this study were to explore the relationship of obesity with major postoperative complications in an international cohort and to present a metaanalysis of all available prospective data. Methods This prospective, multicentre study included adults undergoing both elective and emergency gastrointestinal resection, reversal of stoma or formation of stoma. The primary end-point was 30-day major complications (Clavien–Dindo Grades III–V). A systematic search was undertaken for studies assessing the relationship between obesity and major complications after gastrointestinal surgery. Individual patient meta-analysis was used to analyse pooled results. Results This study included 2519 patients across 127 centres, of whom 560 (22.2%) were obese. Unadjusted major complication rates were lower in obese vs normal weight patients (13.0% vs 16.2%, respectively), but this did not reach statistical significance (P = 0.863) on multivariate analysis for patients having surgery for either malignant or benign conditions. Individual patient meta-analysis demonstrated that obese patients undergoing surgery formalignancy were at increased risk of major complications (OR 2.10, 95% CI 1.49–2.96, P < 0.001), whereas obese patients undergoing surgery for benign indications were at decreased risk (OR 0.59, 95% CI 0.46–0.75, P < 0.001) compared to normal weight patients. Conclusions In our international data, obesity was not found to be associated with major complications following gastrointestinal surgery. Meta-analysis of available prospective data made a novel finding of obesity being associated with different outcomes depending on whether patients were undergoing surgery for benign or malignant disease