Physique et modélisation d’interactions instationnaires onde de choc/couche limite autour de profils d’aile transsoniques par simulation numérique

L’interaction onde de choc/couche limite en écoulement transsonique autour de profils aérodynamiques est étudiée numériquement utilisant différentes classes de modélisation de la turbulence. Les approches utilisées sont celles de modèles URANS et de méthodes hybrides RANS-LES. L’emploi d’une correction de compressibilité pour les fermetures à une équation est aussi évalué. Premièrement, la séparation intermittente induite par le choc sur un profil supercritique en conditions d’incidence proches de l’angle critique d’apparition du tremblement est analysée. Suite à des simulations URANS, la modélisation statistique la mieux adaptée est étudiée et utilisée dans l’approche DDES (Delayed Detached-Eddy Simulation). L’étude de la topologie de l’écoulement, des pressions pariétales et champs de vitesse statistiques montrent que les principales caractéristiques de l’oscillation auto-entretenue du choc sont capturées par les simulations. De plus, la DDES prédit des fluctuations secondaires de l’écoulement qui n’apparaissent pas en URANS. L’étude de l’interface instationnaire RANS-LES montre que la DDES évite le MSD (modeled stress depletion) pour les phases de l’écoulement attaché ou séparé. Le problème de la ‘zone grise’ et de son influence sur les résultats est considéré. Les conclusions de l’étude sur le profil supercritique est ensuite appliquées à l’étude numérique d’un profil transsonique laminaire. Dans ce contexte, l’effet de la position de la transition de la couche limite sur les caractéristiques de deux régimes d’interaction choc/couche limite sélectionnés est étudié. En conditions de tremblement, les simulations montrent une forte influence du point de transition sur l’amplitude du mouvement du choc et sur l’instationnarité globale de l’écoulement. ABSTRACT : Shock wave/boundary layer interactions arising in the transonic flow over airfoils are studied numerically using different levels of turbulence modeling. The simulations employ standard URANS models suitable for aerodynamics and hybrid RANS-LES methods. The use of a compressibility correction for one-equation closures is also considered. First, the intermittent shock-induced separation occurring over a supercritical airfoil at an angle of attack close to the buffet onset boundary is investigated. After a set of URANS computations, a scale-resolving simulation is performed using the best statistical approach in the context of a Delayed Detached-Eddy Simulation (DDES). The analysis of the flow topology and of the statistical wall-pressure distributions and velocity fields show that the main features of the self-sustained shock-wave oscillation are predicted by the simulations. The DDES also captures secondary flow fluctuations which are not predicted by URANS. An examination of the unsteady RANS-LES interface shows that the DDES successfully prevents modeled-stress depletion whether the flow is attached or separated. The gray area issue and its impact on the results are also addressed. The conclusions from the supercritical airfoil simulations are then applied to the numerical study of a laminar transonic profile. Following a preliminary characterization of the airfoil aerodynamics, the effect of the boundary layer transition location on the properties of two selected shock wave/boundary layer interaction regimes is assessed. In transonic buffet conditions, the simulations indicate a strong dependence of the shock-wave motion amplitude and of the global flow unsteadiness on the tripping location

Physics and modeling of unsteady shock wave/boundary layer interactions over transonic airfoils by numerical simulation

Shock wave/boundary layer interactions arising in the transonic flow over airfoils are studied numerically using different levels of turbulence modeling. The simulations employ standard URANS models suitable for aerodynamics and hybrid RANS-LES methods. The use of a compressibility correction for one-equation closures is also considered. First, the intermittent shock-induced separation occurring over a supercritical airfoil at an angle of attack close to the buffet onset boundary is investigated. After a set of URANS computations, a scale-resolving simulation is performed using the best statistical approach in the context of a Delayed Detached-Eddy Simulation (DDES). The analysis of the flow topology and of the statistical wall-pressure distributions and velocity fields show that the main features of the self-sustained shock-wave oscillation are predicted by the simulations. The DDES also captures secondary flow fluctuations which are not predicted by URANS. An examination of the unsteady RANS-LES interface shows that the DDES successfully prevents modeled-stress depletion whether the flow is attached or separated. The gray area issue and its impact on the results are also addressed. The conclusions from the supercritical airfoil simulations are then applied to the numerical study of a laminar transonic profile. Following a preliminary characterization of the airfoil aerodynamics, the effect of the boundary layer transition location on the properties of two selected shock wave/boundary layer interaction regimes is assessed. In transonic buffet conditions, the simulations indicate a strong dependence of the shock-wave motion amplitude and of the global flow unsteadiness on the tripping location

Numerical study of the turbulent transonic interaction and transition location effect involving optimisation around a supercritical aerofoil

The present article analyses the turbulent flow around a supercritical aerofoil at high Reynolds number and in the transonic regime, involving shock-wave/boundary-layer interaction (SWBLI) and buffet, by means of numerical simulation and turbulence modelling. Emphasis is put on the transition position influence on the SWBLI and optimisation of this position in order to provide a maximum lift/drag ratio. A non-classical optimisation approach based on Kriging method, coupled with the URANS modelling, has been applied on steady and unsteady flow regimes. Therefore, the present study contributes to the so-called ‘laminar-wing design’ with the aim of reducing the drag coefficient by providing an optimum laminar region upstream of the SWBLI

Simulation numérique et analyse physique du tremblement transsonique d'un profil supercritique à Reynolds élevé

L'écoulement autour d'un profil d'aile supercritique est étudié numériquement dans le régime du tremblement transsonique à Reynolds élevé par des approches de modélisation de la turbulence statistiques (URANS), statistiques avancées (Organized-Eddy Simulation) et hybrides (DDES). Les différentes méthodes sont évaluées par rapport à leurs capacités de prédiction des caractéristiques du mouvement de l'onde de choc, des fluctuations de grandeurs locales de l'écoulement et des profils de vitesse sur l'extrados. L'influence de l'instabilité de von Kármán sur le tremblement est également analysée

Prediction of Transonic Buffet by Delayed Detached-Eddy Simulation

A delayed detached-eddy simulation of the transonic buffet over a supercritical airfoil is performed. The turbulence modeling approach is based on a one-equation closure, and the results are compared to an unsteady Reynolds-averaged Navier–Stokes simulation using the same baseline model as well as experimental data. The delayed detached-eddy simulation successfully predicts the self-sustained unsteady shock-wave/boundary-layer interaction associated with buffet. When separation occurs, the flow exhibits alternate vortex shedding and a spanwise undulation. The method also captures secondary fluctuations in the boundary layer that are not predicted by unsteady Reynolds-averaged Navier–Stokes simulation. A map of flow separation emphasizes the differences between the delayed detached-eddy simulation and unsteady Reynolds-averaged Navier–Stokes flow topologies. Statistical pressure distributions and velocity profiles help assess the performance of each model. They indicate that the delayed detached-eddy simulation tends to overestimate the flow unsteadiness near the trailing edge. Instantaneous distributions of Reynolds-averaged Navier–Stokes and large-eddy simulation regions during buffet show that the delayed detached-eddy simulation enforces Reynolds-averaged Navier–Stokes mode near the airfoil even when the boundary layer gets very thick

Shock-vortex shear-layer interaction in the transonic flow around a supercritical airfoil at high Reynolds number in buffet conditions

This paper provides a conceptual analysis and a computational model for how the unsteady ‘buffeting’ phenomenon develops in transonic, low incidence flow around a supercritical aerofoil, the OAT15A, at Reynolds number of 3.3 million. It is shown how a low-frequency buffet mode is amplified in the shock-wave region and then develops upstream and downstream interaction with the alternating von Kármán eddies in the wake past the trailing-edge as well as with the shear-layer, Kelvin–Helmholtz vortices. These interactions are tracked by wavelet analysis, autoregressive (AR) modelling and by Proper Orthogonal Decomposition. The frequency modulation of the trailing-edge instability modes is shown in the spectra and in the wall-pressure fluctuations. The amplitude modulation of the buffet and von Kármán modes has been also quantified by POD analysis. The thinning of the shear layers, both at the outer edge of the turbulent boundary layers and the wake, caused by an ‘eddy-blocking’ mechanism is modelled by stochastic forcing of the turbulent kinetic energy and dissipation, by small-scale straining of the higher-order POD modes. The benefits from thinning the shear-layers by taking into account the interfacial dynamics are clearly shown in the velocity profiles, and wall pressure distribution in comparison with the experimental data

Production and survival of Ilex paraguariensis minicuttings and ministumps cultivated in semi-hydroponic system

O objetivo deste trabalho foi avaliar a viabilidade técnica do sistema semi-hidropônico para condução de minicepas de erva-mate e a resposta destas a soluções nutritivas de diferentes diluições nas sucessivas coletas, bem como, a sobrevivência das miniestacas produzidas neste sistema, após enraizamento. Depois de onze coletas, obteve-se 95,6% de sobrevivência das minicepas e média de 291 miniestacas m-2 de minijardim. As mudas obtidas por miniestaquia apresentaram média de 85,6% de sobrevivência, sem variação significativa entre as soluções testadas e número da coleta. O sistema adotado é tecnicamente viável, e recomenda-se a utilização de solução nutritiva menos concentrada.The objective of this study was to assess the technical viability of semi-hydroponic system for conduction of Ilex paraguariensis ministumps, and the answer of these to different nutritional solutions in the successive gatherings, as well as, the survival of the minicuttings produced in this system after rooting. After eleven gatherings, there was 95.6% of ministumps survival, and production of 291minicuttings m-2 of miniclonal garden. The minicuttings survival was 85.6%, with no significant difference between the solutions. The adopted system is technically viable, and lower concentrated solution to conduct the ministumps is recommended

A URBANIZAÇÃO DISPERSA DA CIDADE DE UBERLÂNDIA, MINAS GERAIS, BRASIL

The Brazilian Urban Expansion presents itself over time, more importantly in large and mediumsized cities. In this research we aimed to analyze the urban growth pattern of the city of Uberlândia, MG, through bibliographical review, field work and satellite image analysis. Observing the city landscape there is a wide horizon marked by continuity, that is, the relief is the first favorable aspect for expansion. However, the way how the urban space has been appropriated has left empty spaces waiting for appreciation, where the land speculation acts even before the proper urbanization, causing an expansion of tentacles, spreading by all as directions, characterizing a pattern of dispersed urban growth.A expansão urbana brasileira apresenta-se ao longo do tempo, de maneira desordenada especialmente nas grandes e médias cidades. Buscou-se nesse trabalho investigar o padrão de crescimento urbano da cidade de Uberlândia, MG, através de revisão bibliográfica, trabalhos de campo e análise de imagens de satélite. Observando-se a paisagem da cidade temos um horizonte amplo marcado pela continuidade, ou seja, o relevo é o primeiro aspecto favorável para a expansão. Porém, o modo de apropriação do espaço urbano na cidade, tem deixado vazios à espera da valorização, fazendo com que a especulação imobiliária antecedesse em alguns locais a própria urbanização, ocasionando a forma de tentáculos, espalhando-se por todas as direções, caracterizando um padrão de crescimento urbano disperso avançando cada vez mais em areas de cerrado

Efecto de diferentes protocolos de recuperación sobre la función autonómica cardiaca

Introdução: a avaliação da função autonômica cardíaca (FAC) após o teste de esforço (TE) é considerada um preditor poderoso e independente de risco cardiovascular. É escasso o conhecimento da influência de diferentes protocolos de recuperação sobre a FAC após TE em esteira rolante com os voluntários na posição ortostática. Objetivo: comparar a reativação vagal e o grau de modulação global da FAC em dois diferentes protocolos de recuperação, passiva (RP) e ativa (RA), imediatamente após TE submáximo em esteira rolante. Métodos: foram avaliados 24 homens fisicamente ativos com idade (média ± DP) de 27,2 ± 4,4 anos e IMC 24,8 ± 1,8 kg/m2. A ordem dos protocolos de recuperação foi definida de forma aleatória. Os testes foram realizados com intervalo de sete dias. Ambas as recuperações foram realizadas na posição ortostática durante cinco minutos, imediatamente após TE. Os índices temporais da variabilidade da frequência cardíaca foram utilizados para avaliar a reativação vagal e o grau de modulação global de FAC, rMSSD e SDNN, respectivamente, na RP e RA. Após análise da distribuição dos dados, utilizaram-se os testes de Mann-Whitney e de Friedman com post-hoc de Dum, no nível de significância de p ≤ 0,05. Resultados: verificou-se maior reativação vagal no primeiro minuto de recuperação na RP comparativamente a RA [4,1 (4,9-3,4) ms vs. 3,4 (4,0-2,9) ms, p = 0,03] e maior grau de modulação global da FAC do terceiro ao quinto minuto e tendência a diferença significativa no segundo minuto de RP comparativamente a RA (p = 0,09-0,005). Conclusão: os achados demonstram que o mínimo esforço físico, como caminhar lentamente sobre a esteira rolante, diminuiu a reativação vagal e o grau de modulação global da FAC após o TE submáximo em homens fisicamente ativos.Introduction: the evaluation of cardiac autonomic function (CAF) after stress test (ST) is considered a powerful and independent predictor of cardiovascular risk. The knowledge about the influence of different recovery protocols on CAF after ST on treadmill with volunteers in standing position is scarce. Objective: to compare the vagal reactivation and the degree of global CAF modulation in two different recovery protocols, passive (PR) vs. active (AR) immediately after submaximal ST in treadmill. Methods: We evaluated 24 physically active males, aged (mean ± SD) 27.2 ± 4.4 years and BMI 24.8 ± 1.8 kg/m2. The order of the recovery protocol was set at random. The tests were performed in 7-day intervals. Both recovery protocols were performed in standing position for 5 minutes, immediately after ST. The time indices of heart rate variability were used to assess the vagal reactivation and the overall degree of CAF, rMSSD, and SDNN, respectively, in PR and AR. After analysis of the data distribution, the Mann-Whitney and Friedman tests with Dum post-hoc were used at a significance level of p ≤ 0.05. Results: we observed a higher vagal reactivation at first minute of the PR compared to AR [4.1 (4.9-3.4) ms vs. 3.4 (4.0-2.9) ms, p = 0.03], and a higher degree of global CAF modulation from the third to the fifth minute and a tendency to significant difference in the second minute of PR compared to AR (p = 0.09−0.005). Conclusion: the findings demonstrate that minimum physical effort, such as walking slowly on a treadmill, decreased the vagal reactivation and the overall modulation degree of CAF after a submaximal ST in physically active men.Introducción: la evaluación de la función autonómica cardíaca (FAC) después de la prueba de esfuerzo (PE) se considera un predictor potente e independiente del riesgo cardiovascular. Es escaso el conocimiento de la influencia de los diferentes protocolos de recuperación sobre la FAC después de la PE en la cinta rodante con voluntarios en la posición de pie. Objetivo: comparar la reactivación vagal y el grado de la modulación general de la FAC en dos diferentes protocolos de recuperación, pasiva (RP) vs. activa (RA) inmediatamente después de la PE submáxima en la cinta rodante. Métodos: se evaluaron 24 hombres físicamente activos con edades (promedio ± DE) de 27,2 ± 4,4 años y IMC de 24,8 ± 1,8 kg/m2. El orden de los protocolos de recuperación se definió al azar. Las pruebas se realizaron en un intervalo de siete días. Ambas recuperaciones se realizaron en la posición de pie durante cinco minutos inmediatamente después de la PE. Los índices temporales de la variabilidad de la frecuencia cardiaca fueron utilizados para evaluar la reactivación vagal y el grado de modulación general de la FAC, rMSSD y SDNN, respectivamente, en RP y RA. Después del análisis de la distribución de los datos, se utilizaron la prueba de Mann-Whitney y la de Friedman con post-hoc de Dum, a un nivel de significación de p ≤ 0,05. Resultados: se observó una mayor reactivación vagal en el primer minuto de la PR comparada a la RA [4,1 (4,9-3,4) ms vs. 3,4 (4,0-2,9) ms, p = 0,03] y un mayor grado de modulación general de la FAC del tercer al quinto minuto y una tendencia a la diferencia estadística en el segundo minuto de RP comparada a RA (p = 0,09-0,005). Conclusión: los resultados muestran que el esfuerzo físico mínimo, como caminar lentamente sobre la cinta rodante, disminuyó la reactivación vagal y el grado de modulación general de la FAC después de la PE submáxima en hombres físicamente activos

FENOLOGIA E GERMINAÇÃO DE SEMENTES DE AGUAI, Chrysophyllum gonocarpum (Mart. & Eichl.) Engl.

Basic information on Chrysophyllum gonocarpum, Sapotaceae, still is incipient, therefore, this study intends to contribute with phenology, morphologic and germination registers. Comments and collection of botanical material had been carried out in the Region of the High Medium Uruguay and Missions (RS), from September/2004 to November/2005, as well as the physical and germination tests in laboratory. The species iniates flowers and blooms from September to December and the fruits from May to November. The inflorescence is constituted by groups of small flowers white-greenish with imbricate prebudding, being the metachlamydae, actinomorphic, pentamerous flower, with, upper syncarpus gymnoecium, anthers extrorse, distinct usuably dithecal opening by longitudinal slits, dorsifixix and axillary placentation. The fruit is a quadrangular berry of yellow colour, smooth surface, fleshy mesocarp and endocarp; from 1 to 5 seeds, luniformin moon form half with tegument of brown colour, bright thin pulp, with visible linear scar. The embryo posses two great large foliaceous cotyledons, hipocotylilo short and thick, endosperm uniform, surrounding the embryo. The germination is epigeal and the and seedling is phanerocotylar. The weight of 1,000 seeds is 381g with 2,625 units per kg, with humidity of 47.16%. The results pointed out that the germination is slow desuniforme and therefore there is need for more studies to accelerate, uniform or even establish the germination.Informações básicas sobre Chrysophyllum gonocarpum (Mart. & Eichl.) Engl., Sapotaceae, ainda são incipientes. Assim, pretende-se contribuir com dados fenológicos, morfológicos e germinativos sobre essa espécie. As observações e a coleta de material botânico foram realizadas na região do Médio Alto Uruguai e das Missões (RS), de setembro de 2004 a novembro de 2005, e os testes físicos e germinativos em laboratório. A espécie floresce de setembro a dezembro, e frutifica de maio a novembro. A inflorescência é constituída por grupos de pequenas flores branco-esverdeadas com prefloração imbricada, sendo a flor metaclamídea, actinomorfa, pentâmera, com gineceu sincárpico, súpero, anteras extrorsas, rimosas, dorsifixas e placentação axilar. O fruto é uma baga quadrangular, com epicarpo liso, de cor amarela, de mesocarpo e endocarpo carnoso macio, ovário com 1 a 5 sementes em forma de meia lua, tegumento lustroso, de cor castanha, com cicatriz linear visível. O embrião possui dois cotilédones grandes, foliáceos, hipocótilo curto e espesso, endosperma uniforme, circundando o embrião. A germinação é epígea e a plântula é caracterizada como fanerocotiledonar. Na análise física, o peso de 1000 sementes foi de 381 g, contabilizando 2.625 unidades por quilo, com umidade de 47,16%. Quanto à germinação, os resultados obtidos apontaram para um processo lento e desuniforme, demonstrando, portanto, a necessidade de maiores estudos para acelerar, uniformizar ou até mesmo estabelecer a germinação