Advanced integral model for groups of interacting round turbulent buoyant jets

An integral model that combines all advantages of Superposition Method (SM), Entrainment Restriction Approach (ERA) and Second Order Approach (SOA) is proposed to predict the mean axial velocity and concentration fields of a group of N interacting vertical round turbulent buoyant jets. SM is successful in predicting the fields of mean axial velocity and mean concentration for a group of N interacting jets or plumes and ERA is advantageous in predicting the above fields for either two or large number (N → ∞) of interacting buoyant jets in the whole range of buoyancy. SOA takes into consideration in a dynamic way the turbulent contribution to the momentum and buoyancy fluxes and provides better accuracy than the usual procedures. A novelty of the proposed model is the production and utilisation of advanced profile distributions, convenient for the mean axial velocities and concentrations in a cross-section of the entire group of buoyant jets. These profiles are developed on the basis of flux conservation of momentum, buoyancy and kinetic energy for the mean motion. They enhance dynamic adaptation of the individual buoyant jet axes to the group centreline. Due to these profile distributions, the present model owns generality of application and better accuracy of predictions compared to usual integral models using simple Gaussian or top-hat profiles; thus it conferred the name Advanced Integral Model (AIM). AIM is herein applied to predict the mean flow properties of two different arrangement types of any number of buoyant jets: (a) linear diffusers and (b) rosette-type risers. Present results are compared to available experimental data and traditional solutions based on Gaussian profiles. Findings may be useful for design purposes and environmental impact assessment.     

Spatial concentration distributions of sulfur dioxide and nitrogen oxides in Patras, Greece, in a winter period

An economic and quick methodology for performing a preliminary spatial assessment of a city air quality with the purpose to identify locations and zones susceptible to high pollution levels is proposed. A Patras case-study is selected, regarding the air pollutants of sulfur dioxide (SO₂) and oxides of nitrogen (NO_x). A total number of 451 samples of short duration, of which 225 were randomly picked in morning rush hours and 226 within evening rush hours, were collected from 50 locations of the major Patras area during a year period, when peaks of primary air pollutants usually occur. Concentration measurements at prescribed locations used to statistically calculate spatial average concentrations approximating 1-h mean values with mean probable errors less than 25.9% for SO₂, NO and NO_x and less than 15.5% for NO₂. Then iso-concentration contour diagrams plotted indicate high pollution zones and possibly appropriate locations for continuous or random monitoring according to the European Community (EC) Directives. The 1-h mean concentrations were in good correlation to the corresponding traffic rates and useful relationships are given (0.54 ≤ r ≤ 0.63). In addition, comparisons with data available for other cities, as well as with the limit and guide values provided by the EC and the World Health Organization (WHO) were given. The present data could be useful for the design and optimization of a city network of stations for monitoring air quality, for environmental impact assessments, future reference and comparisons due to city development needs, as well as for validating dispersion models.     

Particulate and Sulfur Dioxide Concentration Measurements in Patras,Greece

Abstract

The purpose of this study was to obtain a better assessment of the Patras, Greece, air quality, in terms of the primary pollutants total suspended particulates (TSPs) and sulfur dioxide (SO₂), because limited and short-duration measurements have been conducted in the past. Installation and operation of a mobile air monitoring station at two different locations in the Patras downtown area and one location in the outskirts of the city was undertaken and covered the periods July 1, 1994-January 30, 1995; March 18-August 23, 1995; and April 19-July 27, 1996, respectively. For both pollutants measured at each location, the monthly average concentrations and typical weekly variation of daily averages, as well as the diurnal variations and frequency concentration distributions in each month of the monitoring periods, were calculated and are presented in bar diagrams. The annual and winter period medians and the annual 98th percentile were also calculated and are compared with the limit and guide values provided by the European Economic Community Council Directive 80/779/EEC. In addition, comparison of SO₂ values is made with the limit values adopted by the more recent Directive 1999/30/EC. It was found that the TSP and SO₂ levels at all locations were very low and were lower than the levels found in Thessaloniki and Athens, Greece. An attempt to explain what had been measured is also undertaken. The data presented are considered essential for future reference and comparison purposes.     

Sulfur dioxide dispersion and source contribution to receptors of downtown Patras, Greece

Background The development of the city of Patras, including harbour relocation, in conjunction with the protection of the regional ecosystems, requires air quality assessment and management. For this reason, a model applicable in the Patras area is necessary and valuable. The goal of this study was to validate a model suitable for predicting the dispersion of sulfur dioxide (SO₂), based on particular activity, topography and weather conditions. Methods We used the US-EPA ISCLT3 integral dispersion model to predict SO₂ concentrations for Patras, Greece. We assumed that the major contribution to Patras air pollution came from central heating, harbour and traffic. We calculated traffic emissions using COPERTIII. Results and Discussion Assigning suitable values of the mixing height, the model predicted the local and spatial distribution of the mean monthly SO₂ concentrations in downtown Patras, as well computed the contribution of the SO₂ emissions originating from each particular source at each receptor location on a seasonal and annual basis. The comparison between predictions and measurements shows that the model performance for estimating the SO₂ concentrations and period pattern is satisfactory. Conclusion The mixing height was the critical parameter for calibrating the model. Model validation promises satisfactory predictions for SO₂ pollution levels on monthly basis. Recommendations and Outlook The model could be used in predicting SO₂ concentrations and source contribution for several downtown Patras receptors using pertinent meteorological and emission information. It could be also extended to predict the dispersion of other primary air pollutants. The calibrated model predictions could be used to fill gaps in monitoring data, saving money and time, and help in assess and manage air quality as Patras develops.     

Particulate and sulfur dioxide concentration measurements in Patras,Greece

The purpose of this study was to obtain a better assessment of the Patras, Greece, air quality, in terms of the primary pollutants total suspended particulates (TSPs) and sulfur dioxide (SO2), because limited and short-duration measurements have been conducted in the past. Installation and operation of a mobile air monitoring station at two different locations in the Patras downtown area and one location in the outskirts of the city was undertaken and covered the periods July 1, 1994-January 30, 1995; March 18-August 23, 1995; and April 19-July 27, 1996, respectively. For both pollutants measured at each location, the monthly average concentrations and typical weekly variation of daily averages, as well as the diurnal variations and frequency concentration distributions in each month of the monitoring periods, were calculated and are presented in bar diagrams. The annual and winter period medians and the annual 98th percentile were also calculated and are compared with the limit and guide values provided by the European Economic Community Council Directive 80/779/EEC. In addition, comparison of SO2 values is made with the limit values adopted by the more recent Directive 1999/30/EC. It was found that the TSP and SO2 levels at all locations were very low and were lower than the levels found in Thessaloniki and Athens, Greece. An attempt to explain what had been measured is also undertaken. The data presented are considered essential for future reference and comparison purposes.