575 publications from this institution
In the past 70 years, considerable advances have been made in wind-driven rain (WDR) research in building engineering. Experimental, semi-empirical and numerical simulation methods have been developed and applied to assess the amount of WDR impinging on building facades. Each of these methods has been combined with hygrothermal simulation models to determine the uptake of WDR water by porous building materials, and these models have become standard evaluation tools for building facade performance and durability. Several state-of-the-art rain penetration testing facilities have been developed and applied. In spite of these achievements, considerable challenges remain. Semi-empirical methods are often not accurate enough to capture the complexity of WDR. Numerical simulation based on Computational Fluid Dynamics (CFD) has hardly been explored beyond the case of the isolated building model. Little is known about the contact and surface phenomena that can occur at raindrop impact. More information is also needed on rain penetration mechanisms. At present, research efforts are focusing on at least these four research tracks. The complexity of WDR ensures they will continue to do so for a considerable time in the future.
General circulation models of climate change predict that the intensity and frequency of heat waves will increase, which are a significant threat to public health (Luber and McGeehin 2008). The effect of heat waves on the public health became apparent during the 2003 heat wave in France, where almost 15,000 heat related deaths (excess of 60%) were reported (Pirard et al. 2005). Between 1,000 and 2,200 heat related excess deaths were reported in the Netherlands (Fischera et al. 2004, Garssen et al. 2005). The total heat related excess mortality across Europe was more than 50,000 (Brucker 2005, Kosatsky 2005). In this study, a first heat wave vulnerability classification for overheating is made of four Dutch residential building types, using historical climate data of five heat-waves in the Netherlands. The four evaluated building types are Terraced houses, Corner houses, Detached houses and SemiDetached houses, of which the geometry was based on the Dutch reference buildings (SenterNovem 2006). Apart from these four building types, ten other variables/uncertainties such as building orientation, ventilation rate, Rc-values and window areas were taken into account using Monte Carlo analysis. For this analysis, 400 cases were generated for each building type using random Latin Hypercube sampling. From this analysis a first classification was made, which from most to least vulnerable was: (1) Detached house, (2) Corner house, (3) Semi-detached house, (4) Terraced House.
The urban environment constitutes a promising potential for wind energy harvesting where the wind turbines can be integrated in the existing buildings and city infrastructures or renovation projects. While several studies have been performed to investigate the urban wind energy potential, the impact of the arrangement of high-rise buildings has not yet investigated in detail. In this paper, therefore, the impact of the arrangement of high-rise buildings on the wind energy potential (defined as high mean wind speed and low turbulence intensity (Ti 18%)) is investigated using 3D steady Reynolds-averaged Navier-Stokes (RANS) simulations. A 2×2 array of high-rise buildings with height = 90 m and aspect ratio (height/width) of 4.5 is studied. The evaluation is based on validation with wind-tunnel measurements of mean wind speed for a generic urban area. The study focuses on two building orientations, = 0 and 45, and seven distances, ranging from 3 to 21 m, between the side facades of the upstream buildings. The results show that for cases with = 45 and D 9 m, the wind power potential between the buildings significantly increase (29%). The findings of the study support the design of high-rise buildings with respect to integrated wind energy harvesting.
A cycling peloton is the main group of cyclists riding closely together to reduce aerodynamic drag and energy expenditure. Previous studies on small groups of in-line drafting cyclists showed reductions down to 70 to 50% the drag of an isolated rider at same speed and these values have also been used for pelotons. However, inside a tightly packed peloton with multiple rows of riders providing shelter, larger drag reductions can be expected. This paper systematically investigates the drag reductions in two pelotons of 121 cyclists. High-resolution CFD simulations are performed with the RANS equations and the Transition SST-k-ω model. The cyclist wall-adjacent cell size is 20 μm and the total cell count per peloton is nearly 3 billion. The simulations are validated by four wind-tunnel tests, including one with a peloton of 121 models. The results show that the drag of all cyclists in the peloton decreases compared to that of an isolated rider. In the mid rear of the peloton it reduces down to 5%–10% that of an isolated rider. This corresponds to an "equivalent cycling speed" that is 4.5 to 3.2 times less than the peloton speed. These results can be used to improve cycling strategies.
Pressure measurements in a boundary layer wind tunnel on two tall building models in tandem arrangement are analysed in order to determine local wind loads relevant for facade design. The tests comprise measurements of 4 configurations over 24 wind directions. Mean and root-mean-square pressure contours are presented for two model faces. The results show that the so-called Venturi or channelling effect in a building passage is a flow phenomenon with highly unsteady features. Furthermore, the ratio of separation distance and building influence scale, w/S, appears to be a promising parameter to provide an indication for the influence on the local loads on buildings in tandem arrangement.
Abstract An increase in ambient air temperature due to climate change can adversely affect indoor thermal conditions, particularly in heritage-listed dwellings, as renovation efforts may be limited by preservation constraints, potentially leading to indoor overheating for occupants. Incorporating heritage-listed dwellings into the climate change adaptation strategies is essential. Heritage-listed dwellings exhibit varying preservation constraints, with character-defining elements differing across cases. A literature review indicates a deficiency in research regarding climate change adaptation for lilong houses, which are two- to three-storey terrace houses featuring timber-brick structures, predominantly constructed in late 19th and early 20th century Shanghai, and recognised as significant urban heritage of the city. Through building energy simulations, this article examines the climate change adaptation of heritage-listed apartment-style lilong houses in Shanghai. Overheating hours and degree hours are utilised to assess indoor overheating conditions. Three scenarios for the preservation of the building envelope are proposed: (1) preservation of walls, (2) preservation of windows, (3) preservation of the roof. There are five categories of climate change adaptation measures. The findings indicate that substantial reductions can be attained by implementing a single preservation scenario customised to the character-defining elements and preservation constraints of heritage-listed dwellings. The most significant decrease in the number of overheating hours is observed in the wall preservation scenario, with a reduction of 69%, followed by a 53% reduction in the roof preservation scenario and a 31% reduction in the window preservation scenario. The proposed preservation scenarios enable the improvement in building indoor thermal conditions without compromising heritage preservation.
Knowledge of the efficiency of contaminant removal from buildings is important with regard to indoor air quality and comfort and health of the occupants. In naturally ventilated buildings, contaminants produced inside the building should be removed by wind and/or buoyancy. Computational Fluid Dynamics (CFD) can be applied to analyze natural ventilation by modeling the interaction between outdoor wind flow and indoor air flow. This paper presents transient CFD simulations with species modeling to reproduce CO2 gas removal from a large semi-enclosed stadium by means of natural ventilation. The simulation, in which both the decay of air temperature and water vapor concentration are incorporated, shows a good agreement with full-scale measurements of CO2 concentration decay, made after three concerts on three consecutive evenings, when the indoor CO2 level had reached its maximum. Further research will include sensitivity analysis of CFD indoor dispersion and natural ventilation simulations to the wide range of computational parameters involved.
Competitive hand-cycling represents a unique case for cycling aerodynamics as the athletes are in a relatively aerodynamic position in comparison to traditional able-bodied cyclists. There are some aerodynamic similarities between both cycling disciplines, including wheel designs and helmets. The lack of research in hand-cycling aerodynamics presents the potential for significant improvements. This research analysed the aerodynamics of competitive hand-cycling under crosswind conditions using wind-tunnel experiments and Computational Fluid Dynamics (CFD) simulations. A range of yaw angles from 0° to 20° in 5° increments were investigated for two separate hand-cycling setups; a road race and a time-trial setup. A maximum drag increase of 14.1% was found from 0° to 15° yaw, for a hand-cyclist equipped for a road race. The three disk wheels used for the TT setup had a large impact on the lateral forces experienced by the TT hand-cyclist. At just 5° yaw and at 15 m/s, the drag and lateral forces for the TT setup matched closely, while this event did not occur until 15° yaw at the same velocity for the road setup. For 20° yaw, the ratio of the lateral force to drag force was 1.6 and 5.6 for the road and TT setups respectively.
The Dutch railways plan to increase the amount of trains and their running velocities to avoid overcrowded trains during rush hours. Pedestrian discomfort or danger at platforms can be caused by trains which are allowed to pass small railway stations at high speeds up to 140 km/h. A number of these railway stations lay underground, where wind gusts caused by trains are amplified by space confine-ment. The purpose of this study is to evaluate the effect of passing passenger and freight trains on the wind flow induced inside an un-derground tunnel by means of transient CFD simulation.
