1,721,157 research outputs found
A comparative study of circular and rectangular bended plunging jets
Full text linkIn the present work we study the topology, mixing properties, turbulence quantities, dependence on the outlet geometry of a sharp-edged orifice plunging jet which first issues horizontally in air and then plunges in a water pool. The investigated orifices shapes are circular and rectangular. Data are acquired at different Reynolds numbers in the range 11000-25000, based on the orifice diameter (equal to 2 cm) and on the average exit velocity, as derived from flow rate measurements. Velocity fields in vertical and horizontal planes are measured using planar time-resolved Particle Image Velocimetry. Results show a clear asymmetry of the cross-velocity profiles both in circular and rectangular cases, with the latter that revealed a shape which is Reynolds num-ber dependent. Axial velocity decays, potential core lengths and spreading rates highlight an opposite trend between the two jet geometries, thus suggesting a higher mixing for the lowest Reynolds number circular jet and the highest rectangular one. Plunging angle shows a dependency on Reynolds number. Moreover, it seems to play a role in the evolution of the upper and lower side of the jet due to the onset of a co-flow. Ambient mass entrainment points out the different interactions of the two plunging jets with the ambient flow: in circular case, it entrains fluid from the surroundings, from horizontal to vertical planes in streamwise direction, while in rectangular one it ejects flow from vertical to horizontal planes. Finally, Strouhal numbers are derived for main vortices frequencies along jet centerline, other than upper and lower sides
World Trade Center disaster: Short- and medium-term health outcome
Full text linkSeveral studies related to September 11 World Trade Center (WTC) terrorist attack have been conducted in order to monitor physical and mental health in the population at risk in the short and medium term. In this paper the main health consequences in the exposed subjects 6 years after the disaster, including ocular, gastrointestinal, respiratory and psychological effects are described and discussed
Role of density ratio on particle dispersion in a turbulent jet
No full textThe behavior of dispersed particles in a turbulent round jet is experimentally investigated. The role of particle-to-fluid density ratio rho(p)/rho(f) is analyzed by inspecting particle velocity fields and preferential concentration at four different ratios, from 0.7 to 19.3. The jet near-field region, i.e., up to X/D = 11, is analyzed and compared to the unladen case. Particle-to-fluid density ratio is reported to have a strong impact on particle velocity field structure, in terms of jet transition and self-similar region as well as on turbulent fluctuations. Concentrations of particles show that increasing particle density corresponds to larger departure from uniformity. This occurrence is limited to the region X / D < 5, where also the largest differences of average and fluctuating velocities with respect to the unladen case are measured
STUDIO DELL'IPERRESPONSIVITA BRONCHIALE ASPECIFICA IN UN GRUPPO DI LAVORATORI DI UN'INDUSTRIA DI CELLE FRIGORIFERE
No full text36 workers employed in a refrigerator factory, divided into 3 groups at different levels of exposure to MDI, were submitted to anamnestic questionnaire, spirographic tests, aspecific bronchial provocation test with acetylcholine, and dosage of plasmatic immnoglobulins IgA, IgE, IgG, IgM. We found no statistically significant difference among the three groups for the prevalence of symptoms of asthma and chronic bronchitis, basal respiratory parameters and immunoglobulins plasmatic concentrations, whereas the percent of subjects with aspecific bronchial hyperreactivity was statistically significantly greater in the group of subjects exposed to higher concentration of MDI. This difference was not related to any other variable except the level of exposure. We suggest that the aspecific provocation test with acetylcholine may be useful in the monitoring of subjects exposed to the respiratory hazard of isocyanates
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