New tools for assessing personal exposure near urban air pollution hotspots

During the last decade, researchers and policy makers have focused on the development and deployment of air pollution mitigation measures invoking solutions based on technology transfer. This term encompasses the synthesis of air quality monitoring, primarily by networks of inexpensive sensors, remote sensing and numerical modelling, as tools for supporting policy makers and disseminating air quality information to the citizens. It has been recognised that localised concentration maxima developing around traffic sources represent an exposure contribution of major epidemiological significance. The ability, therefore, of an integrated air quality management system to reliably assess personal exposure heavily depends on the consistent numerical treatment of multiscale interactions which determine the flow and dispersion structures in these fine spatial scales. Moreover, it is important to incorporate innovative methodologies for enhancing the stability and error-resilience of the sensor networks themselves. The approach presented in this work focuses on the utilisation of latest developments both in sensor technology and numerical air quality modelling, so as to provide end products able to support regulatory assessment and environmental information services. A peer-to-peer network of air quality measuring devices is deployed in six urban areas in the Balkan region in order to provide real time air quality data over areas of high population and emissions density. The coupled mesoscale modelling system MEMO/ MARS-aero and the mesomicro MEMICO two-way coupling methodology implement the physical modelling core of the system in the respective spatial scales. These modelling tools are used to estimate, integrate and complement the sensor data on pollutant levels in predictions of high temporal and spatial resolution in order to highlight pollution hot spots. In the case of fine particulate matter, special adaptations are incorporated in the emissions and chemical transformation treatment in order to provide consistent number concentration fields, which constitute the most relevant exposure metric

THE EFFECT OF SOURCE TREATMENT ON POLLUTANT DISPERSION IN AN IDEALISED URBAN ROUGHNESS IN NUMERICAL SIMULATIONS USING THE STANDARD k-ε TURBULENCE CLOSURE MODEL

The need for accurate model predictions in urban air quality assessment studies during the past decade has led to the ever increasing use of Computational Fluid Dynamics (CFD) models in order to resolve the various local scale inhomogeneities which dominate flow and dispersion and are usually encountered in urban areas. Towards the aim of improving model predicted dispersion via the use of CFD models, a numerical study was undertaken in order to investigate the effect of different techniques applied for treating the sources of emissions on the near source behaviour of the models, as well as on the actual predicted concentrations at locations away from the vicinity of the sources under consideration. A series of 3D numerical simulations were performed for the wind tunnel model geometry of the Mock Urban Setting Test (MUST) field experiment of the University of Hamburg, Meteorological Institute, Division of Technical Meteorology, which was made available within the frame of COST Action 732. Overall in conclusion, results show that depending on the type of source, the intensity of the vertical component of the emissions exit velocity at the source and the mesh refinement close to source boundaries predicted concentrations can deviate significantly from the wind tunnel measurements. However, it is possible to partially improve the performance of a CFD model in urban dispersion problems, mainly via the application of the proper combination of these parameters

THE EFFECT OF SOURCE TREATMENT ON POLLUTANT DISPERSION IN AN IDEALISED URBAN ROUGHNESS IN NUMERICAL SIMULATIONS USING THE STANDARD k-ε TURBULENCE CLOSURE MODEL

The need for accurate model predictions in urban air quality assessment studies during the past decade has led to the ever increasing use of Computational Fluid Dynamics (CFD) models in order to resolve the various local scale inhomogeneities which dominate flow and dispersion and are usually encountered in urban areas. Towards the aim of improving model predicted dispersion via the use of CFD models, a numerical study was undertaken in order to investigate the effect of different techniques applied for treating the sources of emissions on the near source behaviour of the models, as well as on the actual predicted concentrations at locations away from the vicinity of the sources under consideration. A series of 3D numerical simulations were performed for the wind tunnel model geometry of the Mock Urban Setting Test (MUST) field experiment of the University of Hamburg, Meteorological Institute, Division of Technical Meteorology, which was made available within the frame of COST Action 732. Overall in conclusion, results show that depending on the type of source, the intensity of the vertical component of the emissions exit velocity at the source and the mesh refinement close to source boundaries predicted concentrations can deviate significantly from the wind tunnel measurements. However, it is possible to partially improve the performance of a CFD model in urban dispersion problems, mainly via the application of the proper combination of these parameters

A METAMODELLING IMPLEMENTATION OF A TWO-WAY COUPLED MESOSCALE-MICROSCALE FLOW MODEL FOR URBAN AREA SIMULATIONS

Systems of coupled prognostic mesoscale and microscale models have been used as a tool to accurately simulate flows around artificial structures and over densely-built urban areas. Typical implementations of such systems are based on a one-way coupling scheme, where the mesoscale model provides initial and boundary conditions for each off-line application of the microscale model. While very successful in predicting steady-state flows within specific local-scale areas, such schemes fail to account for feedbacks on the mesoscale flow induced by the presence of structures in smaller scales. Unfortunately, the large gap of spatial and temporal scales practically prohibits parallel on-line execution of the mesoscale and microscale models for any significant time interval. It is therefore necessary that a simplifying approach is adopted, where the microscale feedback is spatially and temporally upscaled to interact with parts of the mesoscale domain covering the urban area. In the present work a two-way coupled model system is developed, consisting of the prognostic mesoscale model MEMO and the microscale model MIMO. The microscale feedback on the mesoscale domain is simulated using a metamodelling approach, where the effect of local flows on the vertical profiles is estimated for representative urban areas of sizes up to a few hundred meters and used as calibration input for a set of interpolating metamodels. The feedback from the microscale metamodels is then introduced back in the mesoscale grid by means of Newtonian relaxation. As an illustrative application, simulations for the city of Athens, Greece during a multi-day period are presented. Effects of the microscale feedback on the mesoscale flow become evident both as a reduction of lower-level wind speeds in urban cells as well as an overall increase in turbulent kinetic energy production over densely-built areas

Identifying the optimal strategy for suppliers’ involvement in product design: A case study

In order to increase efficiency and improve competitiveness, manufacturers around the globe are focusing on developing their core businesses. On the other hand, standard activities of engineering are optimally accomplished outside the borders of the firm; thus outsourcing of non-core businesses has become lately a common practice. Product design is considered as one of the most important phases in a product’s life cycle, since the majority of most critical decisions in terms of products’ overall performance are considered during the Research & Development (R&D) phase. Involving suppliers in a firm’s R&D offers significant benefits in various directions, such as feasibility, practicability, sustainability, competitiveness and innovativeness. However, selecting the optimal outsourcing strategy is not an easy decision. On the contrary, it is most challenging since it encompasses a number of different and in many cases mutually conflicting criteria. This paper presents a methodological approach for the selection of the optimal outsourcing strategy for a manufacturer’s R&D. The methodology is based on outranking multicriteria methods and more specifically ELECTRE III. The approach is illustrated and validated through a real world case study of a Greek olive oil producer.   Keywords: product design; suppliers; R&D; outsourcing strategy; multicriteria analysis, ELECTRE II

FAIRMODE: A FORUM FOR AIR QUALITY MODELLING IN EUROPE

FAIRMODE (Forum for AIR quality MODelling in Europe) is an air quality modelling network that was established as a joint initiative of the European Environment Agency (EEA) and European Commission’s Joint Research Centre (JRC). In a common effort EEA and JRC aim at responding to the requirements of the new Air Quality Directive, with particular focus on the introduction of modelling as a necessary tool for air quality assessment and air quality management. The main aim of the modelling network is to bring together air quality modellers and model users in order to promote and support harmonised use of modelling for the assessment of air quality by EU and EEA member countries. The network will thus encourage synergy – at a local, national and European level - through the development and implementation of a common infrastructure based on best practices for reporting and storing information relevant to air quality modelling. A major objective of the FAIRMODE initiative is to provide guidance to present and future air quality model users in EEA’s EIONET partnership network. FAIRMODE also aims to enhance awareness of model usefulness, reliability and accuracy through model validation and intercomparison exercises at a national or European level. The JRC has taken on a leading role in the co-ordination of the latter activities gaining from its experience in leading the “Eurodelta” and “CityDelta” intercomparison exercises. A centralised web portal has been created in support of FAIRMODE, which is currently being used for internal communication purposes of the network participants, but will also provide the means for exchange of relevant material and experiences between all interested modellers and model users. The initial activities of the network will be organised by two main Work Groups, focusing on the preparation of a Guidance Document for model use and on model QA/QC procedures (input data, other uncertainties) respectively. The progress of the preparation of these documents as well as of the rest of the regular activities of the network will be reviewed and discussed within the frame of annual Plenary meetings and Steering Committee meetings

The ACCENT-protocol: a framework for benchmarking and model evaluation

We summarise results from a workshop on “Model Benchmarking and Quality Assurance” of the EU-Network of Excellence ACCENT, including results from other activities (e.g. COST Action 732) and publications. A formalised evaluation protocol is presented, i.e. a generic formalism describing the procedure of how to perform a model evaluation. This includes eight steps and examples from global model applications which are given for illustration. The first and important step is concerning the purpose of the model application, i.e. the addressed underlying scientific or political question. We give examples to demonstrate that there is no model evaluation per se, i.e. without a focused purpose. Model evaluation is testing, whether a model is fit for its purpose. The following steps are deduced from the purpose and include model requirements, input data, key processes and quantities, benchmark data, quality indicators, sensitivities, as well as benchmarking and grading. We define “benchmarking” as the process of comparing the model output against either observational data or high fidelity model data, i.e. benchmark data. Special focus is given to the uncertainties, e.g. in observational data, which have the potential to lead to wrong conclusions in the model evaluation if not considered carefully.publishe

A nested multi-scale system implemented in the large-eddy simulation model PALM model system 6.0

Large-eddy simulation (LES) provides a physically sound approach to study complex turbulent processes within the atmospheric boundary layer including urban boundary layer flows. However, such flow problems often involve a large separation of turbulent scales, requiring a large computational domain and very high grid resolution near the surface features, leading to prohibitive computational costs. To overcome this problem, an online LES–LES nesting scheme is implemented into the PALM model system 6.0. The hereby documented and evaluated nesting method is capable of supporting multiple child domains, which can be nested within their parent domain either in a parallel or recursively cascading configuration. The nesting system is evaluated by first simulating a purely convective boundary layer flow system and then three different neutrally stratified flow scenarios with increasing order of topographic complexity. The results of the nested runs are compared with corresponding non-nested high- and low-resolution results. The results reveal that the solution accuracy within the high-resolution nest domain is clearly improved as the solutions approach the non-nested high-resolution reference results. In obstacle-resolving LES, the two-way coupling becomes problematic as anterpolation introduces a regional discrepancy within the obstacle canopy of the parent domain. This is remedied by introducing canopy-restricted anterpolation where the operation is only performed above the obstacle canopy. The test simulations make evident that this approach is the most suitable coupling strategy for obstacle-resolving LES. The performed simulations testify that nesting can reduce the CPU time up to 80 % compared to the fine-resolution reference runs, while the computational overhead from the nesting operations remained below 16 % for the two-way coupling approach and significantly less for the one-way alternative.publishedVersio

A nested multi-scale system implemented in the large-eddy simulation model PALM model system 6.0

Large-eddy simulation (LES) provides a physically sound approach to study complex turbulent processes within the atmospheric boundary layer including urban boundary layer flows. However, such flow problems often involve a large separation of turbulent scales, requiring a large computational domain and very high grid resolution near the surface features, leading to prohibitive computational costs. To overcome this problem, an online LES-LES nesting scheme is implemented into the PALM model system 6.0. The hereby documented and evaluated nesting method is capable of supporting multiple child domains, which can be nested within their parent domain either in a parallel or recursively cascading configuration. The nesting system is evaluated by first simulating a purely convective boundary layer flow system and then three different neutrally stratified flow scenarios with increasing order of topographic complexity. The results of the nested runs are compared with corresponding non-nested high-and low-resolution results. The results reveal that the solution accuracy within the high-resolution nest domain is clearly improved as the solutions approach the non-nested high-resolution reference results. In obstacle-resolving LES, the two-way coupling becomes problematic as anterpolation introduces a regional discrepancy within the obstacle canopy of the parent domain. This is remedied by introducing canopy-restricted anterpolation where the operation is only performed above the obstacle canopy. The test simulations make evident that this approach is the most suitable coupling strategy for obstacle-resolving LES. The performed simulations testify that nesting can reduce the CPU time up to 80 % compared to the fine-resolution reference runs, while the computational overhead from the nesting operations remained below 16 % for the two-way coupling approach and significantly less for the one-way alternative. © 2021 Antti Hellsten et al