103 research outputs found
Flow configurations in a Y splitting-junction microchannel
No full textIn the present work, the flow field in a splitting-junction micro channel with a Y shape,
which is the simplest geometry to be employed for heat and mass transfer in micro-devices such
as micro-heat-exchangers and micro-mixers, is investigated experimentally using micro Particle
Image Velocimetry (microPIV). The angular divergence in the Y splitting is changed, as well as the
Reynolds number, in order to investigate the instantaneous and mean flow fields to determine
which configurations are more suitable for practical applications. The results show that the flow
configuration is strongly dependent on the Y shape angle, especially in the junction part, and that
there is also a significant dependence on the Reynolds number
Aeroacoustics and aerodynamics of impinging supersonic jets: Analysis of the screech tones
No full textThe interaction between acoustics and aerodynamics of a supersonic jet is an actual fundamental topic which has been a matter of discussion in the last decades. The present paper is devoted to the experimental analysis of free and impinging jets with particular attention on the effect of an impinging surface on screech tones. The acoustics is studied using free-field microphones, while Particle Image Velocimetry is used to investigate the velocity field. The analysis of acquired data allowed to verify and explain the coupling between acoustic discrete tones and mean and fluctuating flow velocities. (C) 2013 AIP Publishing LLC
Analysis of the characteristic acoustic tones of an impinging jet
No full textThe acoustic emission of a supersonic jet is an interesting and fundamental issue due to the several technological applications and the diverse physical aspects to be still clarified. An experimental analysis of the characteristic acoustic tones of a supersonic impinging jet has been carried out with a particular attention on the effect of the nozzle pressure ratio and the distance of the impinging surface. The screech tones, typical of an imperfectly expanded supersonic free jet, have been first investigated to have an idea of the deflection from the free jet behavior due to the impinging surface. Then the analysis has been focused on smaller distances of the impinging plate from the jet exit to evaluate the behavior of the impinging tones. The difference between screech and impinging tones, due to the different interactions in the generating
feedback mechanism, has been observed
Sound source mechanisms in under‐expanded impinging jets
No full textExperiments on the aeroacoustics of an under-expanded supersonic jet impinging on a flat plate are presented and thoroughly discussed. A wide range of nozzle pressure ratios and of nozzle-to-plate distances has been analyzed with particular attention to the behavior of the discrete component of the noise. The investigation has been carried out by means of acoustic, particle image velocimetry and wall pressure measurements. The analysis of the relationship between the acoustic data and the fluid dynamic fields allows to examine the different source mechanisms of the discrete component of the noise and to evaluate the link between the jet flow structure and the acoustic tone features. Specifically, two ranges of nozzle pressure ratio have been observed showing different acoustic behaviors, characterized by distinct mechanisms of discrete noise generation. These regions are separated by a range of nozzle pressure ratios where impinging tones are not observed. The present experimental data extend previously published results, improving the analysis of the connection between fluid dynamic and acoustic fields and leading to a better comprehension of the impinging tone source mechanisms
TERNARY COMPLEXATION BETWEEN COPPER(II), D-ALANINE OR L-ALANINE AND A CHIRAL POLYMER OF (-)-TRANS-1,2-DIAMINOCYCLOHEXANE USED AS A CHROMATOGRAPHIC RESOLVING AGENT
No full textESR and titrimetric data are reported for the ternary interaction between Cu(II), a chiral polymer based upon (-)-trans-1,2-diaminocyclohexane, and L- or D-alanine in aqueous solution
Detection of BK polyomavirus genotypes in healthy and HIV-positive children
No full textUrine samples from 211 community children (3-7 years age), from 33 HIV type-1 infected children and from 56 HIV-negative children were collected and analyzed for the presence of BK virus (BKV) DNA by PCR. PCR amplifications were carried out using primers specific for the BKV structural region VP1. We also investigated the distribution of BKV subtypes by a restriction fragment polymorphism assay (RFLP). We demonstrated BKV DNA in 3.8% of 211 community children with a higher prevalence of subtype I. In HIV-1 positive children we detected BKV DNA in 2 urine samples (6%) out of 33, both belonging to subtype I. The HIV-negative cluster did not show any positivity to BKV DNA. The results confirm a more frequent primary BKV infection in children of 3-5 years of age and a higher prevalence in hospitalized children affected by HIV-1. The most relevant finding was that among both the community and HIV-1 positive children the subtype I was the most frequently detected
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