115 research outputs found
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 suppliersâ 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 productâs life cycle, since the majority of most critical decisions in terms of productsâ overall performance are considered during the Research & Development (R&D) phase. Involving suppliers in a firmâs 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 manufacturerâs 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. Â 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 Commissionâs 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 â 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 EEAâs 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
âEurodeltaâ and âCityDeltaâ 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 âModel Benchmarking and Quality Assuranceâ 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 ďŹrst and important step is concerning the purpose of the model application, i.e. the addressed underlying scientiďŹc 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 ďŹt 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 deďŹne âbenchmarkingâ as the process of comparing the model output against either observational data or high ďŹdelity 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
Modelling the dispersion of particle numbers in five European cities
We present an overview of the modelling of particle number concentrations (PNCs) in five major European cities, namely Helsinki, Oslo, London, Rotterdam, and Athens, in 2008. Novel emission inventories of particle numbers have been compiled both on urban and European scales. We used atmospheric dispersion modelling for PNCs in the five target cities and on a European scale, and evaluated the predicted results against available measured concentrations. In all the target cities, the concentrations of particle numbers (PNs) were mostly influenced by the emissions originating from local vehicular traffic. The influence of shipping and harbours was also significant for Helsinki, Oslo, Rotterdam, and Athens, but not for London. The influence of the aviation emissions in Athens was also notable. The regional background concentrations were clearly lower than the contributions originating from urban sources in Helsinki, Oslo, and Athens. The regional background was also lower than urban contributions in traffic environments in London, but higher or approximately equal to urban contributions in Rotterdam. It was numerically evaluated that the influence of coagulation and dry deposition on the predicted PNCs was substantial for the urban background in Oslo. The predicted and measured annual average PNCs in four cities agreed within approximatelyPeer reviewe
An inter-comparison exercise of mesoscale flow models applied to an ideal case simulation
An exercise is described aiming at the comparison of the results of seven mesoscale models used for the simulation of an ideal circulation case. The exercise foresees the simulation of the flow over an ideal seaâland interface including ideal topography in order to verify model deviations on a controlled case. All models involved use the same initial and boundary conditions, circulation and temperature forcings as well as grid resolution in the horizontal and simulate the circulation over a 24-h period of time. The model differences at start are reduced to the minimum by the case specification and consist mainly of the parameterisation and numerical formulation of the fundamental equations of the atmospheric flow. The exercise reveals that despite the reduction of the differences in the case configuration, the differences in model results are still remarkable. An ad hoc investigation using one model of the original seven identifies the treatment of the boundary conditions, the parameterisation of the horizontal diffusion and of the surface heat flux as the main cause for the model deviations. The analysis of ideal cases represents a revealing and interesting exercise to be performed after the validation of models against analytical solution but prior to the application to real cases
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MEGAPOLI: concept of multi-scale modelling of megacity impact on air quality and climate
The EU FP7 Project MEGAPOLI: "Megacities: Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation" (http://megapoli.info) brings together leading European research groups, state-of-the-art scientific tools and key players from non-European countries to investigate the interactions among megacities, air quality and climate. MEGAPOLI bridges the spatial and temporal scales that connect local emissions, air quality and weather with global atmospheric chemistry and climate. The suggested concept of multi-scale integrated modelling of megacity impact on air quality and climate and vice versa is discussed in the paper. It requires considering different spatial and temporal dimensions: time scales from seconds and hours (to understand the interaction mechanisms) up to years and decades (to consider the climate effects); spatial resolutions: with model down- and up-scaling from street- to global-scale; and two-way interactions between meteorological and chemical processes
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