Laminar flow in three-dimensional square-square expansions

In this work we investigate the three-dimensional laminar flow of Newtonian and viscoelastic fluids through square–square expansions. The experimental results obtained in this simple geometry provide useful data for benchmarking purposes in complex three-dimensional flows. Visualizations of the flow patterns were performed using streak photography, the velocity field of the flow was measured in detail using particle image velocimetry and additionally, pressure drop measurements were carried out. The Newtonian fluid flow was investigated for the expansion ratios of 1:2.4, 1:4 and 1:8 and the experimental results were compared with numerical predictions. For all expansion ratios studied, a corner vortex is observed downstream of the expansion and an increase of the flow inertia leads to an enhancement of the vortex size. Good agreement is found between experimental and numerical results. The flow of the two non-Newtonian fluids was investigated experimentally for expansion ratios of 1:2.4, 1:4, 1:8 and 1:12, and compared with numerical simulations using the Oldroyd-B, FENE-MCR and sPTT constitutive equations. For both the Boger and shear-thinning viscoelastic fluids, a corner vortex appears downstream of the expansion, which decreases in size and strength when the elasticity of the flow is increased. For all fluids and expansion ratios studied, the recirculations that are formed downstream of the square–square expansion exhibit a three-dimensional structure evidenced by a helical flow, which is also predicted in the numerical simulations

Three-dimensional flow of Newtonian and Boger fluids in square-square contractions

The flow of a Newtonian fluid and a Boger fluid through sudden square–square contractions was investigated experimentally aiming to characterize the flow and provide quantitative data for benchmarking in a complex three-dimensional flow. Visualizations of the flow patterns were undertaken using streakline photography, detailed velocity field measurementswere conducted using particle image velocimetry (PIV) and pressure drop measurements were performed in various geometries with different contraction ratios. For the Newtonian fluid, the experimental results are compared with numerical simulations performed using a finite volume method, and excellent agreement is found for the range of Reynolds number tested (Re2 ≤23). For the viscoelastic case, recirculations are still present upstream of the contraction but we also observe other complex flow patterns that are dependent on contraction ratio (CR) and Deborah number (De2) for the range of conditions studied: CR = 2.4, 4, 8, 12 and De2 ≤150. For low contraction ratios strong divergent flow is observed upstream of the contraction, whereas for high contraction ratios there is no upstream divergent flow, except in the vicinity of the re-entrant corner where a localized a typical divergent flow is observed. For all contraction ratios studied, at sufficiently high Deborah numbers, strong elastic vortex enhancement upstream of the contraction is observed, which leads to the onset of a periodic complex flow at higher flow rates. The vortices observed under steady flow are not closed, and fluid elasticity was found to modify the flow direction within the recirculations as compared to that found for Newtonian fluids. The entry pressure drop, quantified using a Couette correction, was found to increase with the Deborah number for the higher contraction ratios

Mycobacterium avium Complex in domestic and wild animals

Mycobacteria from the Mycobacterium avium complex (MAC) cause a variety of diseases including tuberculosis-like disease in humans and birds, disseminated infections in AIDS patients and otherwise immunocompromised patients, lymphadenitis in humans and mammals and paratuberculosis in ruminants. M. avium subsp. paratuberculosis (Map) is the etiologic agent of Johne´s disease in cattle and it has been identified in human patients with Crohn’s disease. The MAC comprises slow growing mycobacteria that are ubiquitous in the environment (soil and water), and have a wide source range, causing disease in various domestic and wild mammals and birds [1]. The aim of this study was to discuss the classification and biology, epidemiology, clinical signs, pathology, diagnostic techniques, and public health concerns in Mycobacterium avium complex in domestic and wild animals

Lymphocyte population in the granulomatous lesions of wild-boars (Sus scrofa) suspected of tuberculosis

Só está disponível o resumoLymphocyte population in the granulomatous lesions of wild-boars (Sus scrofa) suspected of tuberculosis

AS INUNDAÇÕES NO MUNICÍPIO DE VILA VELHA E A IMPORTÂNCIA DAS BACIAS HIDROGRÁFICAS NO SUPORTE AO PLANEJAMENTO

Vila Velha é um dos municípios mais urbanizados do ES e historicamente sofre com inundações, pois está assentado sobre planícies fluviais e litorâneas, nas quais o avanço da urbanização agrava o problema. O objetivo principal deste paper foi delimitar as bacias que drenam o município e identificar a relação destas com as inundações. Os resultados mostram que o município é drenado por três bacias e o grau de intervenções nos cursos d’água relaciona-se ao de urbanização e compromete o escoamento

Permittivity of (40 nm and 80 nm) alumina nanofluids in ethylene glycol at different temperatures

This article studies the effective permittivity of alumina nanofluids (aluminium oxide) in ethylene glycol. Two nanoparticle sizes (40 nm and 80 nm) were considered and the measurements were carried out at various concentrations (up to 2% in volume) and at six different temperatures (from 298.15 K to 348.15 K). An empirical equation is proposed that allows to obtain the permittivity value at any concentration or temperature in the studied ranges. The influence of the volume fraction, nanoparticle size and the temperature on relative permittivity is shown. When compared to the previous published values for alumina (40 nm) in water, current results show the influence of the base fluid. The enhancement of permittivity was calculated, and its behaviour was analysed. Smaller sized particles have the highest values of permittivity and enhancement. Theoretical models in the study of permittivity are applied. The poor predictions of classical models are attributed to the positive behaviour of the permittivity change on mixing for these nanofluids. The contributions to permittivity from ethylene glycol and nanoparticles are separated in two distinct terms in the variable index equation. The permittivity change on mixing calculated from this equation points out that the nanoparticles are the main responsible for the unusual permittivity increment in these colloids.We appreciate the financial support ED431C 2020-06 provided by the Xunta de Galicia (Spain). M.F.C. thanks Instituto Superior de Engenharia do Porto for granting leave of absence to carry out experimental work at University of Vigo.info:eu-repo/semantics/publishedVersio

Pulmonary lesions consistent with disseminated adiaspiromycosis in egyptian mongooses (Herpestes ichneumon) from Portugal.

Pulmonary lesions consistent with disseminated adiaspiromycosis in egyptian mongooses (Herpestes ichneumon) from Portugal