575 publications from this institution
This paper presents ongoing research about an integrated approach to perform high resolution heat, air and moisture (HAM) simulation of whole buildings. There are several HAM modelling tools, with different space and time resolution. The integrated approach establishes run-time external coupling of existing tools (building envelope HAM, BES, CFD) and utilizes the capabilities of one tool in an attempt to compensate the deficiencies of the other. The paper presents the literature review of approaches for domain integration, the physical processes as dealt with by existing tools, coupling requirements and it addresses the importance of validation and coupling necessity decision procedures.
The presence of building balconies can significantly modify the near-façade wind flow pattern and surface pressures. The present study evaluates the impact of building balcony geometry on mean wind speed on balcony spaces and wind-induced mean surface pressure for generic high-rise buildings. The focus is on balconies that extend along the entire width of the building façade. Large-eddy simulations (LES), validated with wind tunnel experiments, are conducted to investigate the impact of (i) balconies present or not, (ii) balcony depth, (iii) balcony parapet walls, (iv) balcony partition walls, and (v) density of balconies. The results indicate that the balcony geometry can greatly affect the mean wind speed on balcony spaces and the local and façade-averaged mean pressure coefficient (Cp). The presence of balconies can increase the façade-averaged Cp over the windward and leeward façades by 5.2% and 8.9%, respectively. These numbers rise to 23.5% and 23.3% when two partition walls are added at the lateral edges of the façades. Adding five partition walls can reduce the overall area-averaged wind speed on balcony spaces by 68.0% compared to the case without partition walls. These findings can be useful in developing, designing and constructing buildings with façade geometrical details that improve building ventilation, air quality and wind comfort.
CFD simulations of the wind speed conditions in passages between generic parallel building configurations have been performed to initiate the development of grid resolution guidelines. CFD validation is conducted based on published wind tunnel data. At least for the cases studied here, the minimum required grid resolution across the passage width is a function of the passage width and the building influence scale. A preliminary grid resolution guideline is provided and some information for the development of additional guidelines is given.
SARS-CoV-2 can spread by close contact through large droplet spray and indirect contact via contaminated objects. There is mounting evidence that it can also be transmitted by inhalation of infected saliva aerosol particles. These particles are generated when breathing, talking, laughing, coughing or sneezing. It can be assumed that aerosol particle concentrations should be kept low in order to minimize the potential risk of airborne virus transmission. This paper presents measurements of aerosol particle concentrations in a gym, where saliva aerosol production is pronounced. 35 test persons performed physical exercise and aerosol particle concentrations, CO2 concentrations, air temperature and relative humidity were obtained in the room of 886 m³. A separate test was used to discriminate between human endogenous and exogenous aerosol particles. Aerosol particle removal by mechanical ventilation and mobile air cleaning units was measured. The gym test showed that ventilation with air-change rate ACH = 2.2 h−1, i.e. 4.5 times the minimum of the Dutch Building Code, was insufficient to stop the significant aerosol concentration rise over 30 min. Air cleaning alone with ACH = 1.39 h−1 had a similar effect as ventilation alone. Simplified mathematical models were engaged to provide further insight into ventilation, air cleaning and deposition. It was shown that combining the above-mentioned ventilation and air cleaning can reduce aerosol particle concentrations with 80 to 90% , depending on aerosol size. This combination of existing ventilation supplemented with air cleaning is energy efficient and can also be applied for other indoor environments.
The influence of a 90° bend on the characteristics of the flow in a low-speed wind tunnel is investigated with CFD (Computational Fluid Dynamics). CFD validation is performed based on published experimental data. The investigated bend is designed to preserve a uniform velocity inlet profile and a low turbulence level. The influence of bend curvature is assessed. Moreover, the effect of the presence, the number and the spacing of guide vanes is investigated. Two turbulence models are evaluated in the numerical simulations. Bends with a weak curvature and guide vanes are found to perform best in preserving a uniform velocity inlet profile. Comparing guide vanes with equal and variable spacing, the latter results in better flow uniformity in the centre of the duct, downstream of the bend, but not at the outside. A considerable increase in turbulence level is noticed for all configurations investigated. The turbulence has a significant anisotropic character indicating the need for turbulence models that can account for anisotropy in this type of studies.
“Gunumuzde yayin baskisi ve yayinlarin miktari artarken yayinlarin ortalama kalitesinin azaldigi gorulmektedir, bu yuzden daha kariyerinin basinda olan arastirmacilara, dergi makalelerinin nasil yazilmasi gerektigi konusunda rehberlik etmek giderek onem kazanmaktadir. Daha once [bununla ilgili] iyi hazirlamis bircok [yazim] kilavuz ve [yazim] kurallar yayinlanmis olsa da bu makalede kesinlikle yapmamaniz gereken 10 seyin altini cizerek farkli bir yaklasim benimsenmektedir. Ben bu on seyi temel bilimlerdeki tecrubelerime dayandirdim fakat bunlarin bazilari disiplininiz ne olursa olsun dogrulugundan bir sey kaybetmeyecek olan seylerdir.”
Conflation of computational fluid dynamics (CFD) and building energy simulation (BES) has been used in recent years in order to improve the estimation of surface coefficients for studies on thermal comfort, mold growth and other performance aspects of a building. BES can provide more realistic boundary conditions for CFD, while CFD can provide higher resolution modelling of flow patterns within air volumes and convective heat transfer coefficients (CHTC) for BES. BES and CFD can be internally or externally coupled. Internal coupling is the traditional way of expanding software by which the code is expanded by adding new modules and it entails a lot of effort in terms of debugging, maintenance etc. On the other hand, by external coupling different existing numerical packages work together, using the latest advances already implemented in them. This paper focuses on the validation of a newly developed prototype performing the external coupling of BES and CFD. The validation procedure involves an inter-model comparison between a conjugate heat transfer model and the prototype.
Apart from sports events, new large sports stadia are also increasingly used for concerts, conferences and other festivities. An example of such a modern multifunctional stadium is the Amsterdam ‘ArenA’ in the Netherlands. This stadium is equipped with a roof construction that can be opened and closed depending on the weather conditions and the type of event. It is not equipped with HVAC systems to control the conditions of the very large air volume (106 m³). Indoor air quality problems can occur for the configuration with closed roof because of the large number of spectators and insufficient natural ventilation. During the concert period in summer, overheating is an additional problem. This paper presents the results of full-scale measurements and CFD simulations of wind speed and air exchange rate in the above mentioned stadium. CFD simulations are presented which analyse the current air exchange rate and the air exchange rates of several alternative ventilation configurations. CFD was preferred for this study for the detailed simulation of air flow through the relatively small ventilation openings, the discharge coefficients of which are unknown. A particular innovative feature of this study is the combined simulation of outdoor wind flow and indoor air flow.
