Validation of a CFD model for the evaluation of urban microclimate at high latitudes: A case study in Trondheim, Norway

The urban microclimate is a rapidly evolving field of research gaining increasing interest from public authorities and researchers. However, studies at high-latitude cities are scarce and researchers primarily focus on summerly overheating. This study focuses on the validation process of a CFD model that applies the 3D URANS approach with the realisable k-e turbulence model at a highly complex urban area in Trondheim, Norway (63.4° N) during autumn. The CFD model features a polyhedral grid of the urban environment, including geometrically explicitly modelled buildings and trees in the area of interest. Furthermore, solar radiation, longwave radiation exchange, heat transfer from the buildings, heat storage in the urban surface, and the thermal effects of evapotranspiration from trees and grass surfaces are considered. The CFD model is validated with experimental results from a network of five mobile and one reference weather stations in the study area, providing hourly-averaged measurements for wind speed, wind direction (only reference weather station) and air temperature for two 48-h periods from September 27–28 and October 19–20. The results show that the CFD model is well able to reproduce the measured conditions at the area of interest with a mean R2 of 0.60, 0.63, and 0.96 for wind speed, wind direction and air temperature, respectively, at the reference weather station. It will be used in future studies, including the analysis of the impact of urban microclimate on buildings’ energy performance, outdoor thermal and pedestrian wind comfort.publishedVersio

Bioclimatic rehabilitation of an open market place by a computational fluid dynamics simulation assessment

These days urban design of open spaces is strongly related to bioclimatic techniques and practices. It is here presented the procedure of a bioclimatic study by the use of simulation tools. The area of an open market place is characterized of decreased human thermal comfort conditions during summer time. The employment of computational fluid dynamics has contributed in the understanding of what interventions should be made at the open space in order to succeed the defined thermal related targets. Table of the proposed rehabilitation explains what the interventions would contribute in the improvement of the local environment.The authors greatly acknowledge the support of the Mayor of Eordaia Mrs Paraskevi Vrizidou during all simulation stages. ANSYS-CFD simulations were carried out in the framework of student instruction and demonstration of the Department of Environmental Engineering, Democritus University of Thrace in Greece

On the Numerical Solution of Sparse Linear Systems Emerging in Finite Volume Discretizations of 2D Boussinesq-Type Models on Unstructured Grids

International audienceThis work aims to supplement the realization and validation of a higher-order well-balanced unstructured finite volume (FV) scheme, that has been relatively recently presented, for numerically simulating weakly non-linear weakly dispersive water waves over varying bathymetries. We in-vestigate and develop solution strategies for the sparse linear system that appears during this FV discretisation of a set of extended Boussinesq-type equations on unstructured meshes. The resultant linear system of equations must be solved at each discrete time step as to recover the actual velocity field of the flow and advance in time. The system’s coefficient matrix is sparse, un-symmetric and often ill-conditioned. Its characteristics are affected by physical quantities of the problem to be solved, such as the undisturbed water depth and the mesh topology. To this end, we investigate the application of different well-known iterative techniques, with and without the usage of preconditioners and reordering, for the solution of this sparse linear system. The iiterative methods considered are the GMRES and the BiCGSTAB, three preconditioning techniques, including different ILU factorizations and two different reordering techniques are implemented and discussed. An optimal strategy, in terms of computational efficiency and robustness, is finally proposed which combines the use of the BiCGSTAB method with the ILUT preconditioner and the Reverse Cuthill–McKee reordering

Using cool paving materials to improve microclimate of urban areas e Design realization and results of the flisvos project

The present paper deals with the application of 4500 m2 of reflective pavements in an urban park in the greater Athens area. The aim was to improve thermal comfort conditions, reduce the intensity of heat island and improve the global environmental quality in the considered area. To our knowledge, this has been the largest application of cool pavements in urban areas in the world. To evaluate the thermal impact of cool paving materials, specific and detailed measurements of the climatic conditions in the park have been performed before and after the installation of the new materials. Validated computerized fluid dynamics techniques have been used to homogenize the boundary conditions occurring during the two experiments and to perform direct comparisons of the climatic quality in the park. It was estimated that the use of cool paving materials contributes to the reduction of the peak ambient temperature during a typical summer day, by up to 1.9 K. At the same time, the surface temperature in the park was decreased by 12 K, while comfort conditions have been improved considerably. It is concluded that the use of reflective paving materials is a very efficient mitigation technique to improve thermal conditions in urban area

Sur la solution numerique des systems creuses et linéaires émergents de la discretization volume finis des modeles 2D de type Boussinesq

This work supplements the realization and validation of a higher-order well balanced finite volume (FV) scheme developed for numerically simulating, on triangular meshes, weakly non-linear weakly dispersive water waves over varying bathymetries. The scheme has been recently presented by Kazolea et al. \textit{(Coastal Eng. 69:42-66, 2012 and J. Comp. Phys. 271:281-305, 2014)}. More precisely, we investigate and develop solution strategies for the sparse linear system that occurs during this FV discretisation of a set of Boussinesq-type equations on unstructured meshes. The resultant system of equations must be solved at each time step as to recover the actual velocity field of the flow. The system's coefficient matrix is sparse, un-symmetric and often ill-conditioned. Its characteristics are affected by physical quantities of the problem to be solved, such as the un-disturbed water depth and the mesh topology. This work investigates the application of different iterative techniques, with and without the usage of preconditioners and reordering, for the solution of this sparse linear system. Two different iterative methods, three preconditioning techniques, including different ILU factorizations and two different reordering techniques are implemented and discussed. An optimal strategy, in terms of computational efficiency and robustness, is proposed.Ce travail concerne la réalisation et la validation d’un schéma Volumes Finis d’ordre élevé pour la simulation des vagues en régime faiblement non-linéaire et faiblement dispersife sur bathymétries variables. Le schéma implémenté est celui proposé récemment par Kazolea et al. (Coastal Eng 69:. 42-66, 2012 et J. Phys Comp 271:.. 281-305, 2014). Plus précisément, nous étudions et développons des stratégies de solution pour le système linéaire creux qui se produit au cours de la discrétisation des équations de Boussinesq sur maillagesnon structurés. Le système d’équations résultant doit être résolu à chaque pas de temps pour récupérer la vitesse. La matrice du système est creuse, non symétrique et souvent mal conditionné. Ses caractéristiques sont affectées par des quantités physiques tels que la profondeur de l’ eau au repos et la topologie du maillage. Ce travail étudie l’ application de différentes techniques itératives, avec et sans l’ utilisation de pré conditionneurs et de ré-numérotation, pour la solution de ce système linéaire creux. Deux méthodes itératives différentes, troistechniques de pré conditionnement, y compris les différents factorisations ILU et deux techniques de ré ordonnancement différentes sont mises en œuvre et évaluées. Une stratégie optimale, en termes d’efficacité de calcul et de robustesse, est proposé

Evaluation of dispersive liquid–liquid microextraction in the stereoselective determination of cetirizine following the fungal biotransformation of hydroxyzine and analysis by capillary electrophoresis

AbstractWe developed a capillary electrophoresis (CE) and dispersive liquid–liquid microextraction (DLLME) method to stereoselectively analyze hydroxyzine (HZ) and cetirizine (CTZ) in liquid culture media. The CE analyses were performed on an uncoated fused-silica capillary; 50mmolL−1 sodium borate buffer (pH 9.0) containing 0.8% (w/v) S-β-CD was used as the background electrolyte. The applied voltage and temperature were +6kV and 15°C, respectively, and the UV detector was set to 214nm. Chloroform (300µL) and ethanol (400µL) were used as the extraction and disperser solvents, respectively, for the DLLME. Following the formation of a cloudy solution, the samples were subjected to vortex agitation at 2000rpm for 30s and to centrifugation at 3000rpm for 5min. The recoveries ranged from 87.4 to 91.7%. The method was linear over a concentration range of 250–12,500ngmL−1 for each HZ enantiomer (r>0.998) and 125–6250ngmL−1 for each CTZ enantiomer (r>0.998). The limits of quantification were 125 and 250ngmL−1 for CTZ and HZ, respectively. Among the six fungi studied, three species were able to convert HZ to CTZ enantioselectively, particularly the fungus Cunninghamella elegans ATCC 10028B, which converted 19% of (S)-HZ to (S)-CTZ with 65% enantiomeric excess

Determination of levetiracetam in human plasma by dispersive liquid-liquid microextraction followed by gas chromatography-mass spectrometry

Levetiracetam (LEV) is an antiepileptic drug that is clinically effective in generalized and partial epilepsy syndromes. The use of this drug has been increasing in clinical practice and intra- or -interindividual variability has been exhibited for special population. For this reason, bioanalytical methods are required for drug monitoring in biological matrices. So this work presents a dispersive liquid-liquid microextraction method followed by gas chromatography-mass spectrometry (DLLME-GC-MS) for LEV quantification in human plasma. However, due to the matrix complexity a previous purification step is required. Unlike other pretreatment techniques presented in the literature, for the first time, a procedure employing ultrafiltration tubes Amicon (R) (10 kDa porous size) without organic solvent consumption was developed. GC-MS analyses were carried out using a linear temperature program, capillary fused silica column, and helium as the carrier gas. DLLME optimized parameters were type and volume of extraction and dispersing solvents, salt addition, and vortex agitation time. Under chosen parameters (extraction solvent: chloroform, 130 mu Ldispersing solvent: isopropyl alcohol, 400 mu Lno salt addition and no vortex agitation time), the method was completely validated and all parameters were in agreement with the literature recommendations. LEV was quantified in patient's plasma sample using less than 550 mu L of organic solvent.Sao Paulo Research Foundation (FAPESP) [2012/07210-8]Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)Department of Pharmaceutical Sciences, Faculty of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, 14040-903 Ribeirão Preto, SP, BrazilDepartment of Exact and Earth Sciences, Institute of Environmental, Chemical and Pharmaceutical Sciences, Federal University of São Paulo, 09972-270 Diadema, SP, BrazilDepartament of Chemistry, Faculty of Philosophy, Sciences and Letters of Ribeirão Preto, University of São Paulo, 14040-901 Ribeirão Preto, SP, BrazilDepartment of Clinical Analysis, Toxicology and Food Science, Faculty of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, 14040-903 Ribeirão Preto, SP, BrazilDepartment of Exact and Earth Sciences, Institute of Environmental, Chemical and Pharmaceutical Sciences, Federal University of São Paulo, 09972-270 Diadema, SP, BrazilFAPESP: 2012/07210-8Web of Scienc

Design and performance predictions of plus energy neighbourhoods – Case studies of demonstration projects in four different European climates

The article presents the design of four plus energy neighbourhood demonstration projects located in different climate zones in Europe. The demo projects are a part of the Horizon 2020 project ‘syn.ikia’, which aims to enable the development of sustainable plus energy neighbourhoods in different climates and contexts. In this article, we describe the active and passive building strategies and analyse the robustness of the designs with respect to different scenarios of climate change, user behaviour, and energy flexibility. Analyses were performed based on the primary energy balance, including space heating and cooling, ventilation, domestic hot water, and lighting. The performance predictions indicate that all demonstration projects may attain the plus energy balance according to the syn.ikia definition. This was achieved with high performing envelopes, efficient HVAC systems, and onsite renewable energy systems to cover the energy demand. The analysis shows that there is a significant potential for increased self-consumption of photovoltaic energy by adjusting the heating schedules and including electric vehicle charging. Testing of the designs with respect to varying climates and user-behaviours showed that there could be an increased risk of overheating, and that some of the designs may not achieve the positive energy balance in case of ‘worst case’ user behaviour scenarios.publishedVersio

Stability-indicating methods for the enantioselective determination of dihydropyridines by high performance liquid chromatography and capillary electrophoresis

This paper presents simple, rapid, precise and accurate stability-indicating HPLC and CE methods, which were developed and validated for the determination of nitrendipine, nimodipine and nisoldipine. These drugs are calcium channel antagonists of the 1,4-dihydropyridine type which are used in the treatment of cardiovascular diseases. Experimental results showed a good linear correlation between the area and the concentration of drugs covering a relatively large domain of concentration in all cases. The linearity of the analytical procedures was in the range of 2.0-120.0 mu g mL-1 for nitrendipine, 1.0-100.0 mu g mL(-1) for nimodipine and 100.0-600.0 mu g mL(-1) for nisoldipine, the regression determination coefficient being higher than 0.99 in all cases. The proposed methods were found to have good precision and accuracy. The chemical stability of these drugs was determined under various conditions and the methods have shown adequate separation for their enantiomers and degradation products. In addition, degradation products produced as a result of stress studies did not interfere with the detection of the drugs' enantiomers and the assays can thus be considered stability-indicating.Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES