The integral momentum and tracer equations for the mean motion with the turbulence contribution in momentum and tracer fluxes are integrated on the centreline of either plane or round buoyant jets, using suitable assumptions for the spreading coefficients and a closing function, and unified first- and second-order solutions are derived in the entire buoyancy range for mean axial velocities and mean concentrations. Comparisons to experimental data in the literature validate the model and show that second-order solutions deviate less than first-order solutions. Both types are used in conjunction with the integral continuity and kinetic energy equations for the mean motion to determine the variation of the local Richardson and Froude numbers, dispersion ratio, bulk dilution, dilution ratio, entrainment coefficient and mean velocity, kinetic energy flux and its gradient for the mean motion; and the variations of these quantities are evaluated using reported experimental or theoretical data. Finally, the variation of the product of kinetic energy flux and the local Richardson number is examined and a universal constant for both plane and round buoyant jets is revealed, leading to a unified definition of the local Richardson number, which is independent of the flow and mixing geometry and could be useful. Simple computational programming and good overall agreement make the proposed model a very promising tool for laboratory and field studies, outfall design and validation of numerical models.

No abstract

No abstract

An integral model predicting the mean flow and mixing properties of inclined plane and round turbulent buoyant jets in a motionless environment of uniform density is proposed. The escaping masses from the main buoyant jet flow are simulated, and the model can be successfully applied to initial discharge inclinations θ 0 from 90 to −75 • with respect to the horizontal plane. This complementary approach introduces a concentration coefficient, which is calibrated using experimental evidence. The present model has incorporated the second-order approach and, regarding the jet-core region, a jet-core model based on the advanced integral model for the production of more correct transverse profiles of the mean axial velocities and mean concentrations than the common Gaussian or top-hat profiles. The partial differential equations for momentum and tracer conservation are written in orthogonal and cylindrical curvilinear coordinates for inclined plane and round buoyant jets, respectively, and they are integrated under the closure assumptions of (a) quasi-linear spreading of the mean flow and mixing fields, and (b) known transverse profile distributions. The integral forms are solved by employing the Runge-Kutta algorithm. Since the most important contribution in the present model is the simulation of the escaping masses, the model has been called the escaping mass approach (EMA). Herein EMA is applied to predict the mean flow properties (trajectory characteristics, mean axial velocities and mean concentrations) for inclined plane and round buoyant jets. The results predicted are compared with experimental data available in the literature, and the accuracy obtained is more than satisfactory. The performance of the EMA is up to 56 % better than using classical integral procedures. EMA can be used for design purposes and for environmental impact assessment studies.

No 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 (SO 2 ), 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

Round turbulent buoyant jets discharged vertically upwards forming a regular polygon Jets ronds flottants turbulents émis verticalement vers le haut en formant un polygone régulier ARISTEIDIS A. BLOUTSOS, Postgraduate student, ABSTRACT The simplified partial differential equations of momentum and tracer for the mean motion are integrated on the reduced cross-sectional area within the field of one buoyant jet from a group issued vertically upwards from a rosette-type riser. The solutions yield the dimensionless centerline axial velocities and concentrations. Mathematically, the one-jet field is separated from the entire group by employing the Entrainment Restriction Approach (ERA) applicable in interacting buoyant jets with symmetry planes. ERA was herein improved by incorporating the Second Order Approach (SOA). Interaction effects are highlighted by normalizing the mean-flow properties. The role of buoyancy on merging is introduced by a dynamic parameter, which combines proximity effects with buoyancy, thus termed dynamic proximity number. In addition, the distributions for mean dilution, kinetic energy flux and local Richardson number are also predicted, discussed, and compared with data reported in the literature. Findings may be useful for design purposes and environmental impact assessment. RÉSUMÉLes équations aux dérivées partielles simplifiées de la quantité de mouvement et du traceur pour l'écoulement moyen sont intégrées sur la section transversale réduite d'un seul jet flottant regroupant les émissions verticales vers le haut d'une colonne montante de type rosette. Les solutions fournissent les vitesses et des concentrations axiales sans dimensions le long de la ligne centrale. Mathématiquement, le champ du jet unique est séparé du groupe entier en utilisant l'Approche de Restriction d'Entraînement (ERA) applicable aux jets flottants interactifs avec plans de symétrie. La méthode ERA a été ici améliorée en y incorporant l'Approche du Second Ordre (SOA). Les effets d'interaction sont mis en relief par la normalisation des propriétés de l'écoulement moyen. Le rôle de la flottabilité sur le fusionnement est introduit par un paramètre dynamique, qui combine les effets de proximité et de flottabilité, nommé nombre dynamique de proximité. En outre, les distributions de la dilution moyenne, du flux d'énergie cinétique et du nombre de Richardson local sont également calculées, discutées, et comparées aux données rapportées dans la littérature. Les résultats peuvent être utiles pour des objectifs de conception et l'évaluation de l'impact environnemental. assistance in the design and environmental impact assessment of such a system. The operation of these systems and the possible measures taken to minimize probable environmental impacts may also be evaluated by employing computer models in conjunction with field observations. Due to buoyant-jet merging, the flow and mixing field is generally complicated and difficult to resolve. Regarding ocean outfalls using diffusers with rosettetype risers including those with...

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 (SO(2)) 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 SO(2), NO and NO(x) and less than 15.5% for NO(2). 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