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Inlet boundary conditions at the supply opening play an important role in the accuracy and reliability of computational fluid dynamics (CFD) simulations for indoor airflow. A non-exhaustive overview of past CFD simulations of ventilation flow in generic enclosures indicates that uniform hypotheses of inlet boundary conditions are commonly used. However, due to thermal effects and a complex air supply system geometry, constant values of inlet airflow quantities can be insufficient for an accurate simulation of non-isothermal ventilation flow. In addition, this can lead to biased conclusions on the performance of turbulence models and other computational settings. To assess this issue, a well-documented experiment on non-isothermal mechanical ventilation with detailed information of inlet conditions from the literature is used in this study. Different turbulence models and inlet boundary conditions are validated, including seven steady Reynolds-averaged Navier-Stokes (RANS) models, six methods of imposing inlet air velocity, three methods of specifying air temperature, and a wide range of turbulence quantities. The parametric study demonstrates that in this particular case, i.e., cold air supply from a single round nozzle diffuser close to the ceiling, ω-based turbulence models perform better than the ε-based turbulence models. The impacts of different methods to specify inlet air temperature profile and turbulence quantities on the simulation results are not significant. However, if the inlet airflow direction is not taken into account appropriately, significant deviations are observed between CFD simulations and experimental data.

Cycling races contain a multitude of motorcycles for various activities including television broadcasting. During parts of the race, these motorcycles can ride in close proximity of cyclists. Earlier studies focused on the impact of a nearby motorcycle on cyclist drag for in-line arrangements. It was shown that not only a motorcycle in front of a cyclist but also a motorcycle closely behind a cyclist can substantially reduce cyclist drag. However, there appears to be no information in the scientific literature about the impact of the motorcycle on cyclist drag for parallel and staggered arrangements. This paper presents wind tunnel measurements of cyclist drag for 32 different parallel and staggered cyclist-motorcycle arrangements. It is shown that the parallel arrangement leads to a drag increase for the cyclist, in the range of 5 to about 10% for a lateral distance of 2 to 1 m. The staggered arrangement can lead to either a drag increase or a drag decrease, where the latter is about 2% for most positions analyzed. For one of the parallel arrangements, computational fluid dynamics simulations were performed to provide insight into the reasons for the drag increase. A cyclist power model was used to convert the drag changes into potential time gains or losses. Compared to a lone cyclist riding at a speed of 46.8 km/h (13 m/s) on level road in calm weather, the time loss by a drag increase of 10%, 4% and − 2% was 2.16, 0.76 s and − 0.80 s per km, respectively. These time differences are large enough to influence the outcome of cycling races.

On-site renewable energy generation in the built environment can be achieved by incorporating wind turbines in the integral design of buildings. Passages through buildings are considered promising to strengthen the local wind resource availability but information concerning their design and performance is scarce. Therefore, two key design parameters that can enhance the wind energy performance of ducted openings in high-rise buildings are addressed and optimized via CFD simulations: the fillet radius (r) of the opening and the duct diameter (d0). 3D steady RANS simulations are performed and validated with wind tunnel data from the literature. Fillets are shown to suppress flow separation, thereby enhancing the magnitude and uniformity of the wind speed in the duct and reducing the turbulent kinetic energy. With a reference diameter d0 = D, the best-performing configuration has a normalized fillet radius r/d0 = 0.2, which increases the average wind speed in the duct by 65% and the wind power by 354%. Modifying the duct diameter alone has limited influence. However, combining a larger duct diameter d0 = 1.5D with fillets with r/d0 = 0.4, can yield up to 78% increase in average wind speed and 650% in wind power density. Findings indicate that the dimensionless wind speed in the duct (U/U0) scales closely in proportion to the normalized fillet radius (r/d0). With these results, the present study demonstrates the aerodynamic advantage of ducted openings in buildings and identifies relevant design conditions required to improve the wind resource availability for the prospective implementation of wind turbines.

© 2018 The Authors Vertical axis wind turbines (VAWTs) have received growing interest for off-shore application and in the urban environments mainly due to their omni-directional capability, scalability, robustness, low noise and costs. However, their aerodynamic performance is still not comparable with their horizontal axis counterparts. To enhance their performance, the impact of operational parameters such as tip speed ratio (λ), Reynolds number (Re c ) and turbulence intensity (TI) on their power performance and aerodynamics needs to be deeply understood. The current study, therefore, intends to systematically investigate the effect of these parameters in order to provide a deeper insight into their impact on the aerodynamic performance of VAWTs. For this investigation, a Darrieus H-type VAWT has been employed. A wide range of the parameters is considered: λ = 1.2-6.0, Re c = 0.3 × 10 5 -4.2 × 10 5 and TI = 0%-30% to analyze the turbine performance, turbine wake and dynamic loads on blades. High-fidelity computational fluid dynamics (CFD), extensively validated with experimental data, are employed. The results show that (i) variable-speed operation maintaining the optimal λ at different wind speeds improves the turbine power coefficient, e.g. up to 168% at 4 m/s, while keeping an almost constant thrust coefficient, (ii) the turbine performance and wake are Re-dependent up to the highest Re c studied, (iii) large TI (> 5%) improves the turbine performance in dynamic stall by promoting the laminar-to-turbulent transition and delaying stall on blades, however it deteriorates the optimal performance by introducing extra skin friction drag. The findings of the current study can support more accurate performance prediction of VAWTs for various operating conditions and can help the improvement of the aerodynamic performance of VAWTs. ispartof: Energy Conversion And Management vol:169 pages:45-77 status: published

Wind flow in urban environments is an important factor governing the dispersion of heat and pollutants from streets, squares and buildings. This paper presents a coupled CFD modelling approach for urban wind flow and indoor natural ventilation. A specific procedure is used to efficiently and simultaneously generate the geometry and the high-resolution body-fitted grid for both the outdoor and indoor environment. This procedure allows modelling complex geometries with full control over grid quality and grid resolution, contrary to standard semi-automatic unstructured grid generation procedures. It also provides a way to easily implement various changes in the model geometry and grid for parametric studies. As a case study, a parametric analysis of natural ventilation is performed for the geometrically complex Amsterdam ArenA stadium in the Netherlands. The turbulent wind flow and temperature distribution around and inside the stadium are solved with the 3D steady Reynolds-averaged Navier-Stokes equations. Special attention is given to CFD solution verification and validation. It is shown that small geometrical modifications can increase the ventilation rate by up to 43%. The coupled modelling approach and grid generation procedure presented in this paper can be used similarly for future studies of wind flow and related processes in complex urban environments.

Wind-driven rain (WDR) is one of the most important boundary conditions governing the hygrothermal behaviour of building facades, which is usually numerically analysed with the so-called Heat-Air-Moisture (HAM) transfer models. In the traditional approach of HAM transfer models, WDR is implemented in a simplified manner: the total mass of all raindrops impinging on a certain surface area of a building facade during the time interval of the meteorological input data (typically 1 h) is spatially and temporally averaged and is supplied to the facade as an averaged moisture flux. However, real WDR is the sum of individual raindrops that impinge on the facade in a spatially and temporally discrete modus, and that do not only spread at impact, but may also splash or bounce off the facade. Therefore the reliability of this simplification can be questioned. To investigate its validity, a new experimental set-up was developed at a full-scale test building. It allows simultaneous and continuous measurements of the reference wind speed and direction, WDR intensity, outdoor air temperature and humidity, as well as the response of facade material samples to these environmental conditions. For this purpose, a measuring device was developed that monitors the weight change of the sample with a resolution of 5 mg. Temperatures at the interior and exterior material surfaces are also monitored. The whole measurement data set is used to check the validity of the traditional numerical approach. Large differences are found between the measurement and simulation results, which cannot solely be attributed to the uncertainty in the convective moisture transfer coefficient, but may be due to two additional reasons: the occurrence of splashing and bouncing at raindrop impact on the facade, which is not included in the model, and/or errors in surface moisture evaporation and absorption due to modelling the actual random and discrete raindrop impingement as a simplified averaged moisture flux.

Wind-driven rain (WDR) is one of the most important moisture sources that affect the hygrothermal performance and the durability of building facades. The facades of the Dutch monumental building St. Hubertus show severe deterioration caused by WDR. Assessment of the amount and intensity of WDR falling onto the facades is necessary as input for numerical heat-air-moisture (HAM) transfer models to analyse the causes of the moisture problems and the impact of remedial measures. In this study, a numerical simulation method based on Computational Fluid Dynamics (CFD) is used to predict the amount of WDR impinging on the south-west facade of the tower of the building. The paper focuses on the numerical simulation results, the validation of these results and their sensitivity to two parameters: the level of geometrical detailing of the computational building model and the upstream terrain aerodynamic roughness length. Validation is performed by comparison of the numerical results with a dataset obtained from on-site WDR measurements. It is shown that the CFD simulations provide fairly good predictions of the amount of WDR impinging on the south-west facade of the tower, except for the lower part. It is also shown that the local effects of geometrical facade details are significant and can yield differences in WDR exposure up to 40%, while their effect at other positions is negligible. Finally, the sensitivity of WDR simulations to the upstream aerodynamic roughness length is discussed.

Experimental wind tunnel and smoke visualization testing was conducted to investigate the performance of a two-sided wind catcher. This type of wind catcher is divided internally into two halves for the purposes of air supply and extract. In this study, the two-sided wind catcher model was constructed of two similar one-sided wind catcher models, which were attached back to back. These one-sided models are 1: 40 scale models of Kharmani's School wind catcher in the city of Yazd. Experimental investigations were carried out using an open-circuit wind tunnel, and both the induced volumetric airflow into the building and the pressure coefficients around all surfaces of the wind catcher model were measured at various wind angles. Additional experimental tests and computational fluid dynamics simulation of the wind catcher in the wind tunnel were also conducted in order to assess the accuracy of measurement procedures and the uncertainty of experimental results. To evaluate the stack effects on the natural ventilation performance of a two-sided wind catcher system, the results were compared to the corresponding results of a one-sided one. As a result of placing urban full-scale wind catchers in the boundary layer of atmospheric winds, the effect of this phenomenon was also examined experimentally. The experiments were performed when the wind catcher model with an adjoining house was placed in the wake of upstream objects, resembling neighbouring buildings. It was found that for an isolated two-sided wind catcher model, maximum efficiency is achieved at an air incident angle of 90°, and this can only be explained by the domination of a stack effect rather than dynamic pressure. At this air incident angle the wind catcher efficiency is ≈20 per cent more than the one at zero angle. The results show that the approaching air incident angles, the presence of an object upstream of the structure, and the blowing of atmospheric wind, influence phenomena such as pressure coefficients, induced airflow rate, and the airflow pattern of the two-sided wind catcher. The results show the potential of the two-sided wind catcher as a passive device for providing natural ventilation in buildings.

Hydrodynamic performance of a one-sided wind catcher was investigated by experimental wind tunnel and smoke visualization testing. Wind catchers or what is called Baud-Geers in Persian language was a main component of buildings in central region of Iran and the neighboring countries. A Baud-Geer is a tower used to capture wind from external air stream and induce it into the building in order to provide natural ventilation and passive cooling. Due to geographical coordinates of the region, wind power and the direction of blowing wind, wind catchers are employed in different heights, cross sections of the air passages and the places and the number of the openings. The one-sided wind catcher has only one channel as a passage of induced air and is often related to the areas where there is prevailing wind. These Baud-Geers are employed to catch the wind blowing at higher elevations and direct it to the building, causing it to leave through windows, doors or other exhausted segments. In this study a 1:40 scale model of Kharmani's School Baud-Geer was employed and the induced air flow rate into the test room and the pressure coefficients around all surfaces of its channel were measured for different values of approaching air incident angles. Using measured pressure coefficients, the theoretical values of ventilation air flow were estimated to evaluate ability of simplified models in natural ventilation studies. Due to placing of urban full-scale wind catchers in the boundary layer of atmospheric winds, the effect of this phenomenon was also examined. The experiments were conducted when the wind catcher model with adjoining house was placed in the wake of upstream objects, resembling neighboring buildings. It was found that for an isolated wind catcher model, the maximum efficiency is achieved at zero air incident angle. Also it was concluded that the angle of incidence of the wind, the presence of an upstream building around the structure and blowing of atmospheric wind influence the pressure coefficients, the rate and the direction of ventilation air flow.

Building integrated photovoltaic (BIPV) is a key concept for the realisation of sustainable buildings. Despite the progress in BIPV modelling, the use of sensitivity analysis (SA) is still scarce in the BIPV literature. SA can help the modeller to identify which model inputs influence the model outputs the most. This paper presents a simulation framework that combines global SA methods with a multi-physics BIPV model. The analysis focuses on the performance of naturally ventilated BIPV facade elements (cell temperature and power). Building performance indicators, such as the total heat flux to the building interior and the building wall temperature, are also analysed. Inputs to the SA include convective heat transfer coefficients, cavity airflow rate, and weather conditions. As expected, the SA results were found to be highly dependent on the range selected for the inputs. For a narrow variation in weather conditions, the exterior convective heat transfer coefficient was identified as the input with the strongest influence on the BIPV performance. Results also showed that cavity ventilation becomes more important as the exterior convective heat transfer decreases. These findings indicate the need for accurate models to represent exterior convective heat transfer in BIPV facades and corroborate the importance of cavity ventilation.

With the growing awareness about ipRGC-influenced light (IIL) responses, design applications related to these responses are flourishing. To compare design options and optimize lighting conditions for building occupants, lighting simulations are typically used. However, as our IIL responses depend on the spectral characteristics of light, spectral simulations are required. The goal of this study is to validate two spectral simulation tools, ALFA and Lark, for the study of indoor spaces in relation to occupants’ IIL responses. Indicators associated with IIL responses derived from ALFA- and Lark-simulated data are compared against indicators derived from data measured under indoor daylighting and electric lighting conditions. The results show that Lark outperforms ALFA in most cases, with a simulation error in the ±20% range for point-in-time indicators. When accounting for time dynamics of light exposure, at least 9% of the daylight exposures simulated for a 6-h period in Lark lead to a significant error.

Spoked wheels are the most frequently used wheel type in road cycling competitions and their aerodynamic optimization is crucial for cyclist performance. The aerodynamic performance of wheels is generally analyzed by wind tunnel tests or CFD simulations for isolated wheels. There is a large number of options to model the wheel/ground contact in CFD simulations, including different clearances between tire and ground and different heights of solid contact patches (step). However, it is unclear to what extent these modeling options influence the CFD results. The present paper systematically analyzes the impact of these options on the computed forces and moments of an isolated cycling spoked wheel and elucidates the flow behavior around this wheel for zero yaw conditions. The wheel drag coefficient for the cases where the ground is included in the simulations using a clearance or a step is 1.0% and about 1.8% lower compared to the case without ground, respectively, whereas the rotational moment is about 2.0% lower for all the wheel/ground contact modeling approaches compared to the case without ground. The gap clearance (≤20 mm) and step height (≤10 mm) should be kept minimal to avoid a significant influence on the forces and moments. In addition, the presence of the ground influences the flow behavior in the lower section of the wheel including the pressure distribution on the exterior of the wheel. This study is intended to help researchers and manufacturers to perform accurate CFD simulations of cycling spoked wheels and to optimize their aerodynamics. ispartof: European Journal Of Mechanics B-Fluids vol:82 issue:July-August 2020 pages:21-38 status: Published online

In connection with a design research project for professional in the Dutch building industry, an educational project was developed, the multidisciplinary master project Integral Design, to prepare our Master students better for their professional life. The concept of an earlier developed integral design workshop for professionals was implemented within the start-up workshop of our masters’ project integral design. The frame work of the approach is described as well as the positive effects on the collaboration between the design team members from different disciplines as result of the morphological approach of the Integral Design method. This method was also applied during workshops in different courses about design methodology As basically the same set-up for the workshop was used this allowed us to compare the results of the different students and analyse them. During the different workshop series the effects on the outcome of the conceptual phase of the design process has been investigated. The results of this analysis are presented in the paper and showed some remarkable similarities as well as some differences among the different student groups.

Aquifer thermal energy storage (ATES) is a significant source of heating/cooling systems due to its energy and cost efficient operation. To ensure environmental and energy sustainability, the use of ATES is governed by strict regulations, one of which is the requirement of maintaining a balance in the amount of heat transfer into the ground. In general, the combination of a heat pump (HP) and an air handling unit (AHU) are commonly used to achieve this thermal balance through regeneration strategies for cooling dominated loads. However, this approach increases the operational cost and energy consumption of ATES heating/cooling systems. In this paper, an alternative approach that makes use of night ventilation (NV) for regeneration is evaluated. In addition, the operational cost and energy efficiencies of the commonly used combination of an HP and AHU are compared to those associated with NV operation. The results show that using NV for the regeneration of the cold well could reduce energy consumption by 19.3 MWh/year, which amounts to a 26.4% increase in system coefficient of performance (COP).

© 2018 The Authors In a team time trial (TTT), the main strategy is based on drafting, where team members alternately take the lead while others ride behind the leading cyclist. TTTs can contain up to 9 riders of the same team. To the best of our knowledge, systematic aerodynamic studies of drafting groups from 2 up to 9 riders have not yet been published. Therefore, this paper presents such an analysis for up to 9 drafting cyclists in a single paceline, with wheel-to-wheel spacings d = 0.05, 0.15, 0.5, 1 and 5 m. A total of 47 Computational Fluid Dynamics (CFD) simulations are performed with the 3D RANS equations, standard k-ε model and scalable wall functions and validated with wind-tunnel measurements. In groups of up to 5 identical riders with d up to 1 m, the last rider has the lowest drag but this is not the case for larger groups. A closely drafting group of 7, 8 or 9 riders has an average drag that is about half that of an isolated rider. However, for much longer theoretical single pacelines, a staggered peloton configuration can yet be about two times more drag efficient. ispartof: JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS vol:182 pages:128-145 status: published

As both cycling wheels can constitute up to 10% of the total drag of the cyclist–bicycle system, care is required for accurate modeling of the wheel aerodynamics. This short communication extends the results of an earlier study in which the impact of the presence of the ground and the type of wheel/ground contact modeling on the wheel aerodynamic resistance was studied. In CFD, two types of wheel/ground interaction can be considered, either a small clearance between wheel and ground or a solid step replacing the contact patch. Previous CFD simulations – without crosswind – suggested to limit the distance between wheel and ground to maximum 20 mm, whereas the step height should be maximum 10 mm. New CFD simulations have been performed including the effect of crosswind, and validated with WT tests. These indicate that the clearance between wheel and ground should be maximum 10 mm, lower than without crosswind, whereas the step height should be smaller than 10 mm. Flow field visualizations are provided to elucidate the flow behavior around a spoked wheel in crosswind conditions. This study is intended to help researchers and manufacturers in the selection of best approaches to accurately reproduce the wheel aerodynamics when crosswind is present.

It is crucial to accurately and efficiently predict transient particle transport in indoor environments to improve air distribution design and reduce health risks. For steady-state indoor airflow, fast fluid dynamics (FFD) + Markov chain model increased the calculation speed by around seven times compared to computational fluid dynamics (CFD) + Eulerian model and CFD + Lagrangian model, while achieving the same level of accuracy. However, the indoor airflow could be transient, if there were human behaviors involved like coughing or sneezing and air was supplied periodically. Therefore, this study developed an FFD + Markov chain model solver for predicting transient particle transport in transient indoor airflow. This investigation used two cases, transient particle transport in a ventilated two-zone chamber and a chamber with periodic air supplies, for validation. Case 1 had experimental data for validation and the results showed that the predicted particle concentration by FFD + Markov chain model matched well with the experimental data. Besides, it had similar accuracy as the CFD + Eulerian model. In the second case, the prediction by large eddy simulation (LES) was used for validating the FFD. The simulated particle concentrations by the Markov chain model and the Eulerian model were similar. The simulated particle concentrations by the Markov chain model and the Eulerian model were similar. The computational time of the FFD + Markov chain model was 7.8 times less than that of the CFD + Eulerian model., Highlights • A fast fluid dynamics (FFD) ＋ Markov chain model solver developed in OpenFOAM. • The solver is for predicting transient particle transport in transient indoor airflow. • The developed method had a similar accuracy to the CFD ＋ Eulerian model. • 7.8 times less computing time than CFD ＋ Eulerian model.

© 2018 The Authors 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. ispartof: JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS vol:179 pages:319-337 status: published

Urban wind energy consists of the utilization of wind energy technology in applications to the urban and suburban built environment. The paper provides some views on the progress made recently in the areas of wind resource assessment in the urban habitat; the utilization of suitable wind turbines for enhancing the exploitation of these resources; and the significant role of knowledge of building and urban aerodynamics for an optimal arrangement of interfacing augmented wind with its extraction mechanisms. The paper is not intended to be exhaustive, rather its purpose is to provide some views on the above-mentioned topics from the viewpoint of wind engineering and industrial aerodynamics in the context of buildings and cities.

The national building codes set requirements for building energy efficiency in many countries. The purpose of this study was to improve understanding on the measured and calculated energy efficiency of Finnish schools and daycare centers. The study analyzed the energy consumption of 134 schools and 71 daycare centers and compared the regulatory building permit calculations to measured values for 18 case buildings. According to the results, the specific electricity consumption (kW h/(m2 a)) has increased in schools but not in daycare centers. The heating energy consumption was lower in schools, but this might be explained by that they had clearly larger gross floor area than daycare centers. When compared to the technical requirements in the building code, the actual heating energy consumption has decreased less than what the changes in the building code would suggest. The building energy consumption calculated for building permits with the monthly calculation method and standard use clearly underestimated the measured building energy consumption. The differences were larger in heating energy than in electricity consumption. In conclusion, different regulatory limit values should be considered for the two building types. The calculation methods and input data should be analyzed to ensure that they truly guide towards cost-optimal design choices. submittedVersion

Scale-adaptive simulation (SAS) approach is employed to investigate the complex dynamic stall phenomena occurring on a wind turbine blade. The results are com-pared with the more popular less computationally-expensive unsteady Reynolds-averaged Navier-Stokes (URANS) approach where the latter is validated using three sets of experimental data. The comparison reveals that the two approaches have similar predictions of the instant of the formation/bursting/shedding of the laminar separation bubble (LSB) and dynamic stall vortex (DSV), the size of the LSB and aerodynamic loads during the upstroke. This is while the two approach-es exhibit dissimilar predictions of the trailing-edge vortex characteristics, its in-teraction with the DSV, number of secondary vortices and aerodynamic loads during the downstroke.

Recent museum studies have indicated the appearance of cracks and dimensional changes on decorated oak panels in historical Dutch cabinets and panel paintings. A thorough analysis of these damage mechanisms is needed to obtain a comprehensive understanding of the causes of damage and to advise museums on future sustainable preservation strategies and rational guidelines for indoor climate specifications. For this purpose, a combined experimental-numerical characterization of the fracture behaviour of oak wood of various ages is presented in this communication. Three-point bending tests were performed on historical samples dated 1300 and 1668 A.D. and on new samples. The measured failure responses and fracture paths are compared against numerical results computed with a finite element model. The discrete fracture behaviour is accurately simulated by using a robust interface damage model in combination with a dissipation-based path-following technique. The results indicate that the samples dated 1300 A.D. show a quasi-brittle fracture response, while the samples dated 1668 A.D. and the new samples show a rather brittle failure response. Further, the local tensile strength of the oak wood decreases with age in an approximately linear fashion, thus indicating a so-called ageing effect. Numerical simulations show that, due to small imperfections at the notch tip of the specimen, the maximal load carrying capacity under three-point bending may decrease by maximally \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$7 \%$$\end{document}7%. A comparison between a calibration of the experimental results by isotropic and orthotropic elastic models shows that the peak load is 10–\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$13\%$$\end{document}13% higher for the orthotropic elastic model. Finally, no significant dependence of the fracture toughness on the age of the oak wood and on the orientation of the fracture plane has been found. The strength and toughness values measured can be used as input for advanced numerical simulations on climate-induced damage in decorated oak wooden panels and panel paintings.

A finite element based hygrothermal model consisting of several interconnected components with varying number of spatial dimensions was applied to analyze the time-dependent temperature and humidity conditions of a mechanically depressurized and ventilated crawl space. Purpose of the depressurization is to prevent the intrusion of radon or other insanitary particles into indoor air. However, in typical foundation structures the depressurization will cause airflow from soil into the crawl space air and it may convey excessive moisture making the hygrothermal conditions potential for mould growth or other moisture-induced biological damage, which is not considered to be acceptable even with the depressurization. Although in general the forced convection of humidity from soil presumably increases relative humidity in crawl space, significant heat capacity of the ground may warm the air flowing into the crawl space and thus decrease the relative humidity. Overall effect of the depressurization on the conditions in crawl space is therefore not trivial. Because a full-scale three-dimensional finite element analysis of heat, mass and momentum transfer in crawl space and its surroundings would require excessive computational resources, several simplifications were necessary to apply in the model. According to the numerical results, the airflow through drainage layer into crawl space does not seem to have severe effect on the crawl space conditions. Conversely, in cold periods the relative humidity in crawl space is very low because of the air temperature is increased while flowing through the drainage layer. acceptedVersion

In this paper we present a methodology for simulating and mapping energy needs for European museums for the recent past, near future 2021–2050 and far future 2071–2100. This approach consists of four recent developments: Firstly, climates files. The availability of the hourly based, European, external future A1B climate data from the European FP7 Climate for Culture project. Secondly, classification. An energy-based classification system of museums based on the quality of the building envelope and systems, representing wide ranges of museums. The latter consisted of 16 different museums equal to all combinations of four levels of building construction and four levels of climate control. Thirdly, building performance simulation. A multi-zone building energy and indoor climate model with a proved record of simulating a wide range of buildings, including museums. Seven performance indicators were used: The mean indoor temperature; the mean indoor relative humidity; the mean heating demand; the mean cooling demand; the mean humidification demand; the mean dehumidification demand; the total energy demand. Fourthly, a mapping tool. We used a mapping tool to produce European maps for sixteen museum types and five 30-year periods: recent past, near future, far future, near future minus recent past and far future minus recent past. The most important mapping results are included and discussed in this paper.

Previous findings have indicated better performance attained by modified urban morphologies for wind energy utilization only in single and pair buildings, or medium-dense low-rise building arrays. Hence, the main purpose of this study is to address the research gaps to complete a fundamental understanding of the influences of urban morphology in compact high-rise urban areas on enhancing urban wind energy harvest for sustainable urban development. A comprehensive parametric study is conducted using the computational fluid dynamics tool to analyze the impacts of urban morphologies on the wind energy potential for a 6 × 6 array of generic high-rise buildings, including (i) urban density altered from compact to sparse urban layouts, (ii) building corner shapes of sharp and rounded corners, (iii) urban layouts of in-line and staggered patterns, and (iv) wind directions of 0° and 45°. This investigation implements the three-dimensional steady Reynolds-averaged Navier-Stokes equations with the Reynolds stress model to explore the distributions of wind speed, power density, and turbulence intensity over the building array. The results indicate that decreasing urban plan area density reduces the unacceptable turbulence areas with relatively higher wind power density on the roof. Besides, round corners can produce elevated power densities up to 201% greater than sharp corners beside the building. Even under the oblique wind direction of 45°, the rounded corner still shows better wind energy potentials than the sharp corner. The in-line urban layout demonstrates more significant areas with higher power densities and low turbulence intensities than the staggered urban layout.

Outdoor urban ventilation in a real complex urban area is investigated by introducing a new ventilation indicator – the “air delay”. Computational Fluid Dynamics (CFD) simulations are performed using the 3D steady Reynolds-Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) approaches. The up-to-date literature shows the lack of detailed evaluations of the two approaches for real compact urban areas. This study further presents a systematic evaluation of steady RANS and LES for the assessment of the ventilation conditions in a dense district in Nicosia, Cyprus. The ventilation conditions within the urban area are investigated by calculating the distribution of the age of air. To better assess the outdoor ventilation, a new indicator, the “air delay” is introduced as the difference between the local mean age of air at an urban area and that in an empty domain with the same computational settings, allowing the comparison of the results in different parts of the domain, without impact of the boundary conditions. CFD results are validated using wind-tunnel measurements of mean wind speed and turbulence intensity performed for the same urban area. The results show that LES can accurately predict the mean wind speed and turbulence intensity with the average deviations of about 6% and 14%, respectively, from the wind-tunnel measurements while for the steady RANS, these are 8% and 31%, respectively. The steady RANS simulations overestimate the local mean air delay. The deviation between the two approaches is 52% at pedestrian level (2 m). ispartof: Building and Environment vol:126 pages:355-372 status: published

Indoor temperature (T) and relative humidity (RH) are important for collection preservation and thermal comfort in museums. In the 20th century, the notion evolved that T and RH need to be stringently controlled, often resulting in excessive energy consumption. However, recent studies have shown that controlled fluctuations are permissible, enabling improved energy efficiency. Consequently, the thermal comfort requirements are increasingly important to determine temperature limits, but knowledge is limited. Therefore, a thermal comfort survey study and indoor measurements were conducted at Hermitage Amsterdam museum in Amsterdam, the Netherlands for one year, including: (1) monitoring of existing conditions (T = 21°C, RH = 50%); and (2) an intervention in which T is controlled based on an adaptive comfort approach (T = 19.5–24°C, RH = 50%). The results show that the thermal comfort of the existing conditions is far from optimum; visitors feel too cool in summer and slightly too warm in winter. The adaptive temperature limits were developed to improve thermal comfort significantly without endangering the collection, thereby saving energy. Furthermore, facilitating visitors to adapt their clothing may contribute to enlarging the temperature bandwidth and improve (individual) thermal comfort.

Quality assurance in computational fluid dynamics (CFD) is essential for an accurate and reliable assessment of complex indoor airflow. Two important aspects are the limitation of numerical diffusion and the appropriate choice of inlet conditions to ensure the correct amount of physical diffusion. This paper presents an assessment of the impact of both numerical and physical diffusion on the predicted flow patterns and contaminant distribution in steady Reynolds-averaged Navier–Stokes (RANS) CFD simulations of mixing ventilation at a low slot Reynolds number (Re≈2,500). The simulations are performed on five different grids and with three different spatial discretization schemes; i.e. first-order upwind (FOU), second-order upwind (SOU) and QUICK. The impact of physical diffusion is assessed by varying the inlet turbulence intensity (TI) that is often less known in practice. The analysis shows that: (1) excessive numerical and physical diffusion leads to erroneous results in terms of delayed detachment of the wall jet and locally decreased velocity gradients; (2) excessive numerical diffusion by FOU schemes leads to deviations (up to 100%) in mean velocity and concentration, even on very high-resolution grids; (3) difference between SOU and FOU on the coarsest grid is larger than difference between SOU on coarsest grid and SOU on 22 times finer grid; (4) imposing TI values from 1% to 100% at the inlet results in very different flow patterns (enhanced or delayed detachment of wall jet) and different contaminant concentrations (deviations up to 40%); (5) impact of physical diffusion on contaminant transport can markedly differ from that of numerical diffusion. ispartof: Building Simulation vol:10 issue:4 pages:589-606 status: published

In the recent decade, investigation on the total building performance has become increasingly important for the environmental modelling community. With the advance of integrated design and modelling tool and Building Information Modelling (BIM) development, it is now possible to simulate and predict the building energy efficiency, air quality & health assessment, risk analysis & mitigation scenario for our urban planning analysis; all seamlessly in a single urban digital platform. In order to achieve the national goal of at least 80% of the buildings in Singapore to be green by 2030, Singapore Government has introduced the new BCA Green Mark 2015 scheme for accelerating the green building agenda. During the recent third Green Building Masterplan announced in 2015, it was decided to engage building tenants and occupants more actively to drive energy consumption behavioural change and to address the well-being of the people. Following up from this Masterplan, it is important for both the stakeholders and agency to jointly develop Performance Driven and Scientific Based Simulation Methodology and Evaluation Parameters as a frame work to evaluate the building design based on Singapore's hot and humid climate and densely-built-up urban areas for the Green Mark 2015 Scheme. In this paper, we will present the methodology and perform a baseline case study for the natural ventilation performance with the typical Non-Residential Building (NRB) industrial building. This can be resulted in the comprehensive CFD Quality Check List for the Environmental Sustainable Design (ESD) consultant in order to maintain modelling result accuracy. Demonstration on Indoor Air Quality (IAQ) using Air Exchange Effectiveness (AEE) as performance indicator will also be illustrated.

In the 20th century, museum indoor climates have been conditioned ever more strictly, sometimes beyond guidelines, allowing no fluctuations at all. Among other effects, this has led to excessive energy demands. At the start of the 21st century, interest has increased to condition the indoor climate more reasonable. This study assessed the energy impact of three levels of museum climate control: Reference (21 °C/50% RH, no permissible fluctuations), ASHRAE’s Class AA, ASHRAE’s Class A. Full-scale measurements were conducted in the museum Hermitage Amsterdam for one year. The results show that Class AA saved 49% and Class A saved 63% compared to the Reference setpoint strategy. Moreover, relaxing the climate specifications decreased hourly fluctuations, but increased daily fluctuations. It is highly likely that the overall degradation risk has not significantly changed for most artefacts.

© 2019, The Author(s). The torso angle of a cyclist is a key element to consider when attaining aerodynamic postures. For athletes competing in the tandem para-cycling category as the pilot or stoker, the torso angles are similar to those adopted by able-bodied athletes. However, their aerodynamic interaction is not yet fully understood. To date, there has been no study to identify aerodynamically advantageous torso angles for tandem athletes. In this study, numerical simulations with computational fluid dynamics and reduced-scale wind tunnel experiments were used to study the aerodynamics of tandem cyclists considering 23 different torso angle combinations. The sagittal torso angle combination of the pilot and stoker that yielded the lowest overall drag area of 0.308 m 2 (combined pilot, stoker and bicycle) was 25° for the pilot coupled with 20° for the stoker. The results suggest that higher torso angles for the pilot have a lower impact on the overall drag area than equivalent torso angles for the stoker. This study suggests that a slight relaxation of pilot torso angle (which may help increase power output) may not penalise aerodynamics, in low (< 25°) sagittal torso angle ranges. ispartof: SPORTS ENGINEERING vol:22 issue:1 status: published

Designing an optimal wind farm layout requires fundamental knowledge of the interaction of wind turbines in an arrangement. In this paper, extensive high-fidelity CFD simulations are performed to investigate the influence of relative spacing, i.e., distance (R) and angle (Φ), in double rotor arrangements of co-rotating Darrieus H-type vertical axis wind turbines (VAWTs) on their aerodynamic performance. The relative spacing varies within 1.25d ≤ R ≤ 10d (d: turbine diameter) and −90° ≤ Φ ≤ +90°. The turbines operate at their optimal tip speed ratio. The analysis is focused on the individual and overall power performance of the turbines and their aerodynamics. Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations, validated with experiments, are employed. It is found that an optimal region exists in which a higher overall power coefficient (CPoverall) compared to the CP of an isolated solo rotor (CPSolo) can be achieved. This region corresponds to compact rotor arrangements, i.e. R/d ≤ 3d with Φ ≥ +45° and Φ ≤ −45°, yielding a maximum 1.8% increment in CPoverall/CPSolo at R/d = 1.25 and Φ = +75°. Detailed flow analysis reveals that in the optimal spacing, a narrow passage between the two rotors is formed within which the flow accelerates, forming a high-velocity region. The downstream turbine benefits from its blade(s) passing through this region and consequently yields higher CP values. The findings highlight the high potential for compact VAWT farms with high power density and support the optimal layout design of VAWT farms.

Coastal areas and seaport areas are exposed to high wind speeds which may involve risks for the ships and people working in the area. Therefore, knowledge of the microscale wind conditions is essential for safe maneuvering and mooring of ships and optimizing harbor design. In the present study, 3D steady RANS CFD simulations with the realizable k-e turbulence model are performed for the new configuration of the “IJmuiden sea lock” in Amsterdam, the largest sea lock in the world at the time of writing this article. The computed wind speed and turbulence intensity amplification factors and the local wind directions are validated with on-site measurements for the old configuration of the sea lock. For the wind speed amplification factor and local wind direction, a satisfactory agreement is obtained with 90% of CFD data within ±30% from the measured data. Conversely, for the turbulence intensity amplification factor, less satisfactory agreement is found with 74% of CFD data within ±30% from the measured data. Overall, the 3D steady RANS approach shows a sufficiently high reliability for predicting the wind conditions in the seaport area under neutral atmospheric conditions.

In this study the temperatures on 22 balconies (17 glazed) and adjacent flats were monitored with an aim to determine the key factors affecting the ability of a glazed balcony to warm up and remain warm without a heater. Considered were glazed balconies in different locations, the amount of glazing and building heat loss, the tightness of balcony vertical structures, and balcony ability to capture solar radiation. Temperature monitoring showed that over a year the air temperature of both glazed and unglazed balconies remained almost without an exception above the outdoor air temperature. On average, the temperatures of unglazed balconies were 2.0 °C and those of glazed balconies 5.0 °C higher than the outdoor air temperature. The three key factors affecting the glazed balcony temperatures seemed to be the level of air leakage in the balcony vertical structures, the balcony's ability to capture solar radiation, and the heat gain from an adjacent flat, in that order. The air tightness of the glazing was the most crucial factor, since it affected the results all the year round. Solar radiation was important from spring to autumn and heat gain in midwinter. acceptedVersion

INSULAtE-project assessed impacts of energy retrofits on indoor environmental quality and occupants’ satisfaction. Most common retrofit actions included changing new windows and installing heat recovery into exhaust ventilation system. This paper presents results related to ventilation in Finnish apartment buildings before and after the retrofits. Average ventilation rates (from exhaust vents) in buildings with mechanical ventilation were 0.43 ACH before and 0.48 ACH after the retrofits. Average CO 2 concentrations were 750 ppm before and 715 ppm after the retrofits, correspondingly. Percentage of occupants satisfied with IAQ was 22% before and 41% after the retrofits. In conclusion, ventilation rates, CO 2 -levels, and occupants’ satisfaction with IAQ were improved in most retrofitted buildings.

© 2015 Elsevier Ltd. Both new and existing buildings need to be adapted to climate change, in order to keep providing a comfortable and healthy indoor climate. Preferably, the adaptation measures applied at the building level scale do not require additional energy (i.e. passive measures). Previous studies showed that passive climate change adaptation measures can have a positive effect on thermal comfort in summer and its shoulder seasons in non-air-conditioned residential buildings. In this paper, the effect of these passive climate adaptation measures - applied at building component level - on the cooling and heating energy demand of a terraced house is analyzed using building energy simulations. It is shown that for this particular case the required cooling energy can be limited to a large extent (59-74%) when external solar shading or additional natural ventilation is applied. In addition, it is shown that for a well-insulated terraced house the energy cost for heating is not strongly affected by the application of passive climate change adaptation measures. publisher: Elsevier articletitle: Analysis of the predicted effect of passive climate adaptation measures on energy demand for cooling and heating in a residential building journaltitle: Energy articlelink: http://dx.doi.org/10.1016/j.energy.2015.11.036 content_type: article copyright: Copyright © 2015 Elsevier Ltd. All rights reserved. ispartof: Energy vol:94 pages:811-820 status: published

In this paper we present a new method for simulating and mapping energy demands for European museums for recent past (RP), near future 2020-2050 (NF) and far future 2070-2100 (FF). It is new combination of three recent developments: Firstly, the simulation and mapping of building performance indicators based on European weather stations. Secondly, a multi zone energy model, representing a wide range of museums. The latter consists of 16 different museum zone types equal to all combinations of 4 levels of building construction and 4 levels of climate control. Thirdly, the availability of hourly based, EU wide, external future A1B climate files from the EU FP7 Climate for Culture project. We used 7 performance indicators: (1) mean indoor temperature; (2) mean indoor relative humidity; (3) mean heating demand; (4) mean cooling demand; (5) mean humidification demand; (6) mean dehumidification dem nd; (7) total energy demand, to produce EU maps for 16 museum types and five 30 year time periods: RP, NF, FF, NF-RP and FF-RP. This gives in total 560 maps. The most important mapping results are included and discussed in this paper.

Pressure differences between outdoors and indoors influence indoor environmental quality (IEQ) and building physics of the building envelope. This paper focuses on measurements of pressure difference values of about 152 apartments from 26 multi- family buildings in Finland. Measured data include pressure differences between indoor spaces and both outdoors and staircases before and after renovation. In buildings equipped with mechanical exhaust, the pressure differences between indoors and outdoors before renovation varied from +10,1 to -95,0 Pa (average -7,8 Pa), and between indoors and staircases from -3,5 to -6,0 Pa (average -18,6 Pa), being lower than -5 Pa in 36% of the buildings. In naturally ventilated buildings, the pressure differences between indoors and outdoors were lower than -5 Pa in 44% of the buildings. The average pressure differences after renovation in nine buildings equipped with mechanical exhaust were slightly higher (-19,1 Pa against outdoor and -9,0 Pa against staircase). A possible reason for higher negative pressure could be that the airtightness of building was improved by renovation, but the ventilation system was not balanced accordingly. Improving energy efficiency (EE) could effect on pressure difference either positively or negatively. Measured pressure difference between indoors and outdoors or staircase before and after renovation could be a possible indicator when assessing the impacts of improving EE on IEQ and occupant satisfaction.

© 2015 Elsevier Ltd. The roof geometry of a leeward sawtooth roof building can have a large influence on the cross-ventilation flow. In this paper, five different leeward sawtooth roof geometries are evaluated using Computational Fluid Dynamics (CFD). The 3D CFD simulations are performed using the steady Reynolds-Averaged Navier-Stokes approach with the SST k- ω turbulence model to provide closure to the governing equations. The computational grid is based on a grid-sensitivity analysis and the computational model is successfully validated using PIV measurements for a generic isolated building from literature. The five different roof geometries that are studied include one straight and four curved roofs. The curved roofs can be subdivided in one concave, one hybrid (convex-concave) and two convex roof geometries. It is shown that a straight or convex roof geometry can maximize the underpressure in the wake of the building, where the outlet opening is located, which results in enhanced wind-driven cross-ventilation flow. Analysis of the results shows that for a normal wind incidence angle (0°) the straight and convex leeward sawtooth roof geometries can result in an increase of the volume flow rate by 13.0%, 12.5% and 12.3% respectively compared to a concave roof geometry. Furthermore, the increase of the indoor air velocity can be as high as 90% in the upper part of the occupied zone (at h=1.7. m above ground level) for convex versus concave roofs. publisher: Elsevier articletitle: Impact of roof geometry of an isolated leeward sawtooth roof building on cross-ventilation: Straight, concave, hybrid or convex? journaltitle: Journal of Wind Engineering and Industrial Aerodynamics articlelink: http://dx.doi.org/10.1016/j.jweia.2015.05.014 content_type: article copyright: Copyright © 2015 Elsevier Ltd. All rights reserved. ispartof: Journal of Wind Engineering and Industrial Aerodynamics vol:145 pages:102-114 status: published

The impact of relative spacing on the individual and overall performance of two adjacent co-rotating Darrieus H-type VAWTs is investigated through high-fidelity URANS simulations, validated with experimental data. The simulations cover relative distances of 1.25d ≤ R ≤ 10d (d: turbine diameter) and relative angles of 0° ≤ Φ ≤ 90°. The relative angles of 30° ≤ Φ ≤ 75 with relative distance range of 1.25d ≤ R ≤ 5d are identified as the optimal regime with the highest overall power performance for the array. In this regime, the downstream turbine has a maximum increase of 5.1% in CP (R = 1.5d and Φ = 45°) with respect to an isolated solo rotor with similar characteristics. Local flow characteristics including wake length, wake expansion, vorticity and velocity fields are also investigated. It is found that for azimuthal angles of 90° ≤ θ ≤ 160° in the optimal regime, regions of accelerated flow are created due to the contraction of the flow between the turbines which benefit the downstream turbine CP and thus the overall power performance of the array. This provides an opportunity for a compact placement of turbines within a vertical-axis wind turbine farm and consequently increasing the farm power density.

The identification, quantification, and control of demand flexibility is the major challenge for future grid operations and requires innovative methods and new control strategies. Optimal control strategies such as economic model predictive control have gained attention in building energy management systems. The present experimental case study demonstrates the application of an economic model predictive controller under real-time pricing, including day-ahead prices and imbalance prices. For real-time prices in balancing and spot markets, we introduce a method that presents a flexibility service to provide demand flexibility for a notification time of 1 h t t day end in advance. The flexibility service can be used as an ancillary service for innovative flexibility markets. The flexibility service includes a dynamic modification of the day-ahead prices to enable the adaption of energy consumption to errors in forecasting of renewable energy generation. The developed method was tested under real-life conditions, which also included the stochastic behaviour of occupants and the dynamic behaviour of the building and heating system. During the test periods, the controller managed the total operational costs of the heat pump’s electricity consumption and achieved a prediction performance of Root Mean Square Error between 0.17 and 0.22 kWh. To show the provision of demand flexibility, key performance indicators were quantified according to the categories 1) energy and power, 2) energy efficiency, and 3) energy costs. We introduce this categorization to present the benefits of using flexibility indicators along with conventional performance indicators in real-life applications.

The building sector constitutes a significant share of global energy consumption and CO2 emissions. Despite improving technology and materials, the foundation of successful energy design lies in architectural design decisions. Windows are one architectural design issue that is a key factor in both energy efficiency and functionality. This research utilized dynamic building simulations to study the direct and combined energy impacts of window related architectural design through the following main variables’ effect on heating, cooling, and lighting need: window area, proportions, horizontal position, external shading, glazing properties, and adjacent room proportions. Four solar orientations and three climatically different Finnish locations were included as context variables. Window energy efficiency in the studied cases was found to be primarily about controlling solar heat gain. Geographic location changed not only energy consumption directly, but also the individual variables’ impact on it and each other. The results indicate that cooling can be a significant factor even in cold climates, and that energy efficiency should always be evaluated using local weather data as well as sufficient design detail. Most properties affected each other significantly, highlighting a need for a comprehensive approach in both research and design practice and allowing evaluating previous studies comprising fewer variables. acceptedVersion

Interior insulation is being applied in dwellings constructed with the ‘Airey’ system, a post-war prefab construction system which has recently been gaining heritage significance recognition. It's well-known that applying internal insulation in historic buildings may result in interstitial condensation, surface condensation, mould growth and decay. A review of literature on hygrothermal performance assessment of internal insulation of historic buildings is presented. The results show a strong focus on buildings constructed with solid masonry walls; an evaluation of construction types similar to the Airey system remains absent. The methods that have commonly been applied – being a 1D or 2D simulation of the envelope, focussing on vapour transport through diffusion – were developed to address the hygrothermal behaviour of solid masonry walls. These may not be suitable to identify hygrothermal risks in the Airey system, which is lightweight and has many air cavities. A method for hygrothermal performance assessment that is tailored to these specific characteristics of the Airey system is proposed, combining a whole building HAM-model with a coupled 3D heat transfer model of the construction details. The calibration of the HAM-model to on-site measurements demonstrates the importance of modelling convective vapour transport, specifically as it relates to air leakage through the vapour barrier. The results highlight the importance of accounting for convection in hygrothermal assessments and indicate that simulating a vapour barrier as being installed with perfect airtightness may lead to unrealistic outcomes. Moreover, the results demonstrate the need to further develop the understanding of hygrothermal risks associated with applying internal insulation to non-solid walls, and to adapt the methodology of hygrothermal performance assessments in order to do so.

Heat stress in urban areas can have detrimental effects on human health, comfort and productivity. In order to mitigate heat stress, Computational Fluid Dynamics (CFD) simulations of urban microclimate are increasingly used. The validation of these simulations however requires high-quality experimental data to be compared with the simulation results. Due to lack of available high-resolution high-quality experimental data, CFD validation of urban microclimate for real urban areas is normally performed based on either a limited number of parameters measured at a limited number of points in space, or on experiments for idealized generic configurations. In this study, CFD simulations of urban microclimate are performed for a dense highly heterogeneous district in Nicosia, Cyprus and validated using a high-resolution dataset of on-site measurements of air temperature, wind speed and surface temperature conducted for the same district area. The CFD simulations are performed based on the 3D Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations and the simulated period covers four consecutive days in July 2010. It is shown that the CFD simulations can predict air temperatures with an average absolute difference of 1.35 °C, wind speed with an average absolute difference of 0.57 m/s and surface temperatures with an average absolute difference of 2.31 °C. Based on the comparative results, conclusions are made regarding the performance of URANS for the selected application and possible reasons for deviations between measured and simulated results are discussed.

The Indoor Environmental Quality (IEQ) in a building affects occupants’ well-being and productivity. Traditionally, models are developed to predict IEQ satisfaction from physical measurements. These approaches work fine in a laboratory environment but tend to fail in real-world applications. Recent work focuses on collecting direct human feedback on IEQ. However, existing approaches either lack the ability to capture the multiple dimensions of IEQ or the integration with other domain knowledge, e.g. from building information modeling or building automation systems. To tackle this problem, we have developed a novel approach based on Semantic Web Technologies (SWT) which enable interoperability and reasoning. In this paper, the HBC (Human Comfort in Building) ontology is presented, which formally specifies the domain of IEQ in multiple dimensions and relates it to adjacent domains. An online survey is designed in order to specify ontology requirements and collect human feedbacks for evaluating the ontology. We evaluate the use of the HBC ontology in two use cases in an o ce building: recommendation of spaces based on IEQ factors and recommendation of settings for technical equipment from collected feedbacks.

The application of Computational Fluid Dynamics based on the Reynolds-Averaged Navier-Stokes equations to the simulation of bluff body aerodynamics has been thoroughly investigated in the past. Although a satisfactory accuracy can be obtained for some urban physics problems their predictive capability is limited to the mean flow properties, while the ability to accurately predict turbulent fluctuations is recognized to be of fundamental importance when dealing with wind loading and pollution dispersion problems. The need to correctly take into account the flow dynamics when such problems are faced has led researchers to move towards scale-resolving turbulence models such as Large Eddy Simulations (LES). The development and assessment of LES as a tool for the analysis of these problems is nowadays an active research field and represents a demanding engineering challenge. This research work has two objectives. The first one is focused on wind loads assessment and aims to study the capabilities of LES in reproducing wind load effects in terms of internal forces on structural members. This differs from the majority of the existing research, where performance of LES is evaluated only in terms of surface pressures, and is done with a view of adopting LES as a complementary design tools alongside wind tunnel tests. The second objective is the study of LES capabilities in calculating pollutant dispersion in the built environment. The validation of LES in this field is considered to be of the utmost importance in order to conceive healthier and more sustainable cities. In order to validate the numerical setup adopted, a systematic comparison between numerical and experimental data is performed. The obtained results are intended to be used in the drafting of best practice guidelines for the application of LES in the urban physics field with a particular attention to wind load assessment and pollution dispersion problems.

Sixteen existing multi-family buildings (94 apartments) in Finland and 20 (96 apartments) in Lithuania were investigated prior to their renovation in order to develop and test out a common protocol for the indoor environmental quality (IEQ) assessment, and to assess the potential for improving IEQ along with energy efficiency. Baseline data on buildings, as well as data on temperature (T), relative humidity (RH), carbon dioxide (CO2), carbon monoxide (CO), particulate matter (PM), nitrogen dioxide (NO2), formaldehyde, volatile organic compounds (VOCs), radon, and microbial content in settled dust were collected from each apartment. In addition, questionnaire data regarding housing quality and health were collected from the occupants. The results indicated that most measured IEQ parameters were within recommended limits. However, different baselines in each country were observed especially for parameters related to thermal conditions and ventilation. Different baselines were also observed for the respondents' satisfaction with their residence and indoor air quality, as well as their behavior related to indoor environment. In this paper, we present some evidence for the potential in improving IEQ along with energy efficiency in the current building stock, followed by discussion of possible IEQ indicators and development of the assessment protocol. Keywords: Environmental monitoring, Exposure, Questionnaire, Residential buildings, IEQ indicators

The transpirational cooling of vegetation as a measure to mitigate outdoor air temperatures was investigated for a street canyon in the city center of Arnhem, the Netherlands for the meteorological conditions of an afternoon hour on a hot summer day during a heat wave with wind of speed 5.1 m s −1 at 10 m above ground and direction along the canyon. Computational Fluid Dynamics (CFD) simulations with locally applied vegetation in the street, i.e. avenue-trees, facade greening, roof greening and all three combined, were performed. The 3D steady-state Reynolds-averaged Navier–Stokes (RANS) equations were closed by the realizable k-e turbulence model extended with source and sink terms to represent the effects of vegetation on air flow. By specifying a cooling power term in the energy equation, the transpirational cooling by vegetation was accounted for. The strongest cooling by a single vegetative measure was obtained with the avenue-trees with mean and maximum temperature reductions at pedestrian level of 0.43 °C and 1.6 °C, respectively. Facade greening resulted in rather small changes with mean and maximum reductions of 0.04 °C and 0.3 °C, respectively. For roof greening no noticeable reductions inside the canyon were found. In the case of a combination of all vegetative measures, cooling in terms of spatial distribution and intensity overall resembled a linear superposition of those of the vegetative measures solely applied with 0.52 °C mean and 2.0 °C maximum temperature reduction. Overall, the cooling was restricted to the vicinity of the vegetative measures, i.e. up to a distance of a few meters.

In a changing outdoor climate, new buildings as well as the existing building stock need to adapt in order to keep providing their inhabitants and users a comfortable and healthy indoor environment, with a minimum or – preferably – no increase in energy consumption. In this paper, the effectiveness of six passive climate change adaptation measures applied at the level of building components is assessed using building energy simulations for three generic residential buildings as commonly built in – among others – the Netherlands: (1) detached house; (2) terraced house; (3) apartment. The study involves both residential buildings that are built according to the regulations and common practice in 2012, and residential buildings that were constructed in the 1970s, with a lower thermal resistance of the opaque and transparent parts of the building envelope. The climate change adaptation measures investigated are: (i) increased thermal resistance; (ii) changed thermal capacity; (iii) increased short-wave reflectivity (albedo); (iv) vegetation roofs; (v) solar shading; and (vi) additional natural ventilation. This paper quantifies the effectiveness of these climate change adaptation measures for new residential buildings as well as for renovation of the current building stock. The performance indicator is the number of overheating hours during a year. It is shown that exterior solar shading and additional natural ventilation are most effective for this performance indicator. Furthermore, increasing thermal insulation to reduce energy use for heating demands additional measures to prevent overheating.

When an oak board is exposed to moisture on only one of its surfaces, an asymmetric moisture content profile induces differential expansion over the thickness. Consequently, a bending moment causes the board to curve. Meanwhile, moisture transport takes place, which results in a continuously changing bending moment. When exposed to a step change in the moisture content, the end of the board deflects to a maximum, after which the board, due to moisture transport, deflects back to its initial x-position. The y-position of the free end of the board changes continuously too, but reaches a different value eventually due to a different moisture content. In real-life applications, however, objects are most often exposed to continuous or cyclic changes in the relative humidity. It is shown that the deflective step response of the board contains information about its frequency behavior. When assuming linear system behavior, the frequency response can be predicted from the step response. Experiments with a sinusoidal fluctuation in relative humidity at different frequencies confirm the prediction from the step response.