Vasiliki D. Assimakopoulos

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

Notes on Numerical Fluid Mechanics and Multidisciplinary Design publishes state-ofart methods (including high performance methods) for numerical fluid mechanics, numerical simulation and multidisciplinary design optimization. The series includes proceedings of specialized conferences and workshops, as well as relevant project reports and monographs. Indexed by SCOPUS and Springerlink. The books of the series are submitted for indexing to Web of Science.

VOC and O3 Distributions over the Densely Populated Area of Greater Athens, Greece

Abstract The horizontal and vertical distributions of volatile organic compounds (VOCs) and ozone (O3) concentrations within the lower troposphere over the greater Athens area, Greece, under sea-breeze conditions were studied. Furthermore, an attempt was made to explain the dynamic and chemical mechanisms responsible for the formation of these distributions. Measurements were collected using a specially instrumented Falcon 20-E5 research aircraft, ground-based meteorological instrumentation, and a network of air quality monitoring stations within the context of the Scientific Training and Access to Aircraft for Atmospheric Research Throughout Europe (STAAARTE) 1997 experimental campaign. Relatively high ozone values (55–100 ppbv) were identified within the first 300–400 m above ground, and significantly reduced values were found over the depth of the atmospheric boundary layer. High values of VOC concentrations [150–350 ppbCarbon (C)] were observed near the ground as well as within the first 300–400 m abo...

A modelling method for estimating transboundary air pollution in southeastern Europe

Abstract A new methodology is presented for the model estimation of an import–export pollution balance across country borders based on the classification of the synoptic scale atmospheric circulation. As an application, the transboundary transport of SO 2 and NO x across the Greek borders is investigated for the year 1995. The annual total inflow–outflow fluxes were derived by weighting the model results with the annual relative frequency of the corresponding synoptic type appearance. The results of the new modelling method are similar to those following the day-by-day calculation of the inflow–outflow fluxes for the whole year 1995 using the same models. The advantage of the new methodology is that it is definitely less time-consuming than the day-by-day calculations. Hence, the proposed methodology can be employed as a practical tool for several applications requiring the implementation of complex models over longer time periods.

Indoor air quality assessment in the air traffic control tower of the Athens Airport, Greece

In this study, an assessment of indoor air quality (IAQ) and thermal comfort in the Athens Traffic Control Tower (ATCT) offices of Hellinicon building complex, which is mechanically ventilated, is presented. Measurements of PM10, PM2.5, TVOCs and CO2 concentrations were performed during three experimental cycles, while the Thom Discomfort Index was calculated to describe the employees’ feeling of discomfort. The aim of the first cycle was to identify the IAQ status, the second to investigate the effectiveness of certain measures taken, and the third to continuously monitor and control IAQ. During the first two cycles, daily spot measurements of TVOCs and CO2 were performed at various indoor locations and at the respective outdoor air intake positions, in addition with mean 24-h spot measurements of indoor PM10 and PM2.5. Results revealed that pollution levels vary according to the occupancy and the kind of activity. Following that, an automated system (IMAS) was designed and employed to continuously monitor indoor and outdoor CO2, TVOCs, temperature and relative humidity. The ultimate scope was to control the IAQ and offer acceptable comfort conditions to the employees, whose work is of special nature and extremely demanding. Intervention scenarios were formulated and applied to the system to improve indoor conditions, when and where necessary. Regarding the third cycle, 1-year measurements collected from the system to examine its effectiveness. While it was shown that discomfort may be attributed to co-existence of unsatisfactory thermal comfort conditions and IAQ, usually the sole predominant factor of discomfort feeling is thermal comfort.

On the wind flow patterns under neutral and unstable conditions in an urban area

Wind flow and pollutant dispersion within urban areas depend on the approaching flow profile and temperature stratification. Thus, the flow field developed under neutral and unstable stratification conditions, within a street-canyon, was studied experimentally and numerically for a two-dimensional urban background set-up. Wind-tunnel measurements were carried out with a triple hot sensor anemometer, while an academically developed CFD k–e algorithm was applied, employing an unstructured Cartesian grid. The numerical code compared well with experimental results. Under unstable conditions, intensive mixing exists within the street-canyons and the buoyancy-induced flow affects the vertical air motions within and above them.

Evaluation of CALPUFF modelling system performance: an application over the Greater Athens Area, Greece

This study has been carried out in order to evaluate the performance of CALPUFF modelling system in an area of complex topography. For this reason a comparison was performed between numerical results produced by this modelling system and those derived by two Eulerian models (UAM-V and REMSAD), together with experimental measurements. The meteorological input parameters, produced by the meteorological model CALMET are also examined through comparison with observations and to MM5 model results. Emphasis is given to the mixing height calculation, due to its importance in the prediction of pollutant concentrations. It was found that the overall performance of the CALPUFF is satisfactory and the results derived are compatible with these produced by the Eulerian models, especially under unstable atmospheric conditions. The CALPUFF models performance is improved significantly when vertical meteorological profiles produced by MM5 are additionally employed.

3D flow and pollutant dispersion simulation in organized cubic structures

The turbulent flow and the pollutant dispersion in organized cubic structures simulating an idealized building arrangement in a city is numerically investigated. The basic building arrangement under investigation is the experimental arrangement reported by Uehara et al (2000); it consists of an in line arrangement of cubic blocks having upwind a number of low rise square blocks which act as roughness elements for creating turbulent flow. The purpose of the investigation is to gain physical knowledge on the structure of the three dimensional flow and the pollutant dispersion mechanism, to compare with published two dimensional simulations and mainly to investigate the unsteady character of the flow field and its time scale characteristics.