Numerical and experimental analysis of the flow over a commercial vehicle – pickup

Trabalho de Conclusão de Curso (Graduação)The pickups correspond to an important category of commercial vehicle once they combine passenger and cargo transport. The presence of an open trunk is responsible for a unique flow topology within a natural great interest for manufacturer’s research and that is gradually being more discussed on academic articles. This work presents a numerical and experimental study of the flow around a generic pickup based on the leaders of the light pickup market in Brazil. The proposed pickup model is composed only by flat surfaces and sharp edges and it’s derived from a dimensional study of five principal models of the category; a second version is conceived with the application of fillets on those edges. Simulations are performed using Reynolds Averaged Navier Stokes equations (RANS) on STAR-CCM+ solver with SST k-ω turbulence model; mesh is constituted of tetrahedral elements and the effect of a prismatic boundary layer is studied. On wind-tunnel, hot-wire anemometry and wall tufts visualization techniques are deployed for 1:10 scale model and serve as a reference for numerical results initial validation. Although a new geometry is tested, the results are similar to previous works. Rounding the model caused a reduction of 30% in the drag coefficient; no significant change is noted on the overall distribution of the structures on trunk and wake. Computational solution is prepared for reduced and full size pickup on typical highway velocities; for the range of tested scales (Re from 5×105 to 5×106), problem is believed to be independent of Reynolds, therefore wind-tunnel data that is not dynamic similar is still representative of real flow. This work is aimed to serve as a benchmark for future analyses so that more refined examination on CFD setup (mesh and solver) and application of other experimental routines are recommended. The investigation of drag reducing devices and the effects of other geometry variations is suggested as next steps

Primary melanoma of the oral cavity:a multi-institutional retrospective analysis in Brazil

Melanoma is an aggressive malignant tumor, rarely observed in the oral cavity. The aim of this study was to describe the clinicopathologic features of a series of oral melanomas. A retrospective descriptive study was performed. A total of 15,482 biopsy records from two oral and maxillofacial pathology services in Brazil were analyzed. All cases of oral melanomas were reviewed, and clinical, demographic, histopathological data, treatment, and follow-up status were collected. In addition, immunohistochemistry stains (pan-cytokeratin AE1/AE3, vimentin, ?-SMA, CD45, S-100 protein, HMB-45, Melan A, and Ki-67) were performed. The series comprised of 5 males (71.4%) and 2 females (28.6%), with a mean age of 58.0 ± 9.2 years (range: 45-69 years) and a 2.5:1 male-to-female ratio. The gingiva (n = 3, 42.8%) and hard palate (n = 2, 28.6%) were the most common affected sites, presenting clinically as ulcerated swellings with a brown to black color. Cervical lymph node metastasis was detected in three patients during the first examination. Microscopically, 6 cases (85.7%) were melanotic, and one (14.3%) was amelanotic. Most cases (n = 4, 57.1%) presented a predominance of epithelioid cells. S-100 and HMB-45 were positive in all cases (n = 7, 100.0%). In contrast, only 4 cases (57.1%) were positive for Melan-A. The proliferative index with Ki-67 was high, with labeling index ranging from 70.0% to more than 90% of positive cells. Five patients died from complications of the tumors after a mean follow-up period of 7.8 months. Melanoma is an aggressive malignant tumor that rarely occurs in the oral cavity. It occurs mainly in adult and elderly patients and often is diagnosed in advanced stages. The current findings were similar to previous studies and reflected the characteristics of the services from where lesions were retrieved

Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences

The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & Nemésio 2007; Donegan 2008, 2009; Nemésio 2009a–b; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on 18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based researchers who signed it in the short time span from 20 September to 6 October 2016

Heterogeneous contributions of change in population distribution of body mass index to change in obesity and underweight NCD Risk Factor Collaboration (NCD-RisC)

From 1985 to 2016, the prevalence of underweight decreased, and that of obesity and severe obesity increased, in most regions, with significant variation in the magnitude of these changes across regions. We investigated how much change in mean body mass index (BMI) explains changes in the prevalence of underweight, obesity, and severe obesity in different regions using data from 2896 population-based studies with 187 million participants. Changes in the prevalence of underweight and total obesity, and to a lesser extent severe obesity, are largely driven by shifts in the distribution of BMI, with smaller contributions from changes in the shape of the distribution. In East and Southeast Asia and sub-Saharan Africa, the underweight tail of the BMI distribution was left behind as the distribution shifted. There is a need for policies that address all forms of malnutrition by making healthy foods accessible and affordable, while restricting unhealthy foods through fiscal and regulatory restrictions

Modélisation du bruit d'origine aérodynamique : influence de la géométrie dans le bruit de forme

The influence of the shape on the sound emission of cylindrical bluff-bodies is studied. Simulations are performed in two-dimensions (2D) at low-Reynolds number (Re=20-200), with the incompressible direct Navier-Stokes (DNS) solver incompact3D, using the Immersed Boundary Method (IBM) formalism; the acoustic emission is evaluated by a single formula derived from Curle’s equation for compact cylinders. In anechoic wind tunnel, the acoustic signature is measured for about 30 geometries, Re=4,000-53,000; hot-wire measurements of the spanwise flow characteristics are performed for a subset of the tested cylinders. The influence of both the shape of the upstream portion of the geometry and the breadth-to-height ratio (AR) are proved to be major features in terms of both the flow and its acoustic emission in 2D. By reducing the strength of the vortices and pushing them downstream and affecting the mechanics of the von Kármán instability (delaying the transition to unsteadiness), stretched shapes (with higher AR) are generally quieter. From the experiments, it is found that the geometries of biggest AR are the loudest, contraposing the results obtained in 2D. The disparity is justified by a significant increase of the spanwise coherence associated with the larger AR’s, practically fully-phased, thus more acoustically efficient. Globally, it is implied that geometries which have weakly perturbed flow in 2D, marked by a later transition to unsteadiness (larger critical Reynolds number), are also more organized in 3D, high-Reynolds number regimes. The underlying relationship between low and high-Reynolds number transitions must be further investigated.L’influence de la forme de cylindres longs sur leur rayonnement acoustique en écoulement est étudiée. Des simulations bidimensionnelles (2D) sont réalisées à bas nombre de Reynolds (Re=20-200), à l’aide du code de calcul direct (DNS) incompressible incompact3D au moyen d’une méthode de frontière immergée (IBM). Une formule dérivée de l’équation de Curle pour un cylindre compact permet la quantification de l’émission acoustique en 2D. En soufflerie anéchoïque, la signature acoustique d’une trentaine de géométries est mesurée, Re=4,000-53,000 ; l’anémométrie par fil chaud est utilisée pour la description des propriétés axiales de l’écoulement. L’avant corps et l’allongement (AR) sont les plus importantes propriétés géométriques tant pour l’écoulement que pour le rayonnement acoustique en 2D. Les géométries allongées sont généralement les plus silencieuses car les tourbillons sont moins intenses et repoussés vers l’aval et l’apparition de l’instationnarité est retardée. De leur côté, les résultats expérimentaux montrent que les géométries allongées sont les plus bruyantes, ce qui est à l’opposé des conclusions précédentes. Ceci est justifié par une augmentation significative de la cohérence de l’écoulement en envergure pour les AR les plus longs, presque complètement en phase, donc plus efficace acoustiquement. Globalement, cela implique que les géométries dont l’écoulement 2D est faiblement perturbé, marqué par un déclenchement plus tardif de l’instationnarité (Reynolds critique plus élevé), sont aussi plus organisées en 3D aux Re des mesures. La relation sous-jacente entre les transitions successives vers la turbulence nécessite une étude approfondie

Shape optimization for the noise induced by the flow over compact bluff bodies

International audienceA shape optimization for tonal noise generated aerodynamically at low Mach number is performed for a cylinder with polygonal cross-section. Acoustic quantities are derived from a hybrid analytical formula, with aeroacoustic sources obtained from the incompressible solution of the direct Navier-Stokes equations in 2D at Re = 150; the solid domain is modelled by an Immersed Boundary Method. The optimization is done with the Particle Swarm Optimization (PSO) technique and performed in a cluster where each cost function evaluation is an independent flow simulation. The precision on the 4 main shape parameters is set to 0.001, consistently with the convergence criteria in time, grid and swarm. Optimal shapes for minimum drag and minimum acoustic power are relatively similar. A large range between the optimal shapes is obtained: factor 1.8 for drag and 20 dB for the acoustic power. The reduction of noise is associated with long and bluffer geometries, while the louder flows are associated with highly interacting shear layers obtained with back pointing triangles. The fluctuating lift is the major quantity to control noise at fixed length, while increasing the aspect ratio tends to reduce the noise for globally all geometries. An overall correlation between mean drag and fluctuating suction is also noticed