Direct Numerical Simulation of a separated channel flow with a smooth profile

A direct numerical simulation (DNS) of a channel flow with one curved surface was performed at moderate Reynolds number (Re_tau = 395 at the inlet). The adverse pressure gradient was obtained by a wall curvature through a mathematical mapping from physical coordinates to Cartesian ones. The code, using spectral spanwise and normal discretization, combines the advantage of a good accuracy with a fast integration procedure compared to standard numerical procedures for complex geometries. The turbulent flow slightly separates on the profile at the lower curved wall and is at the onset of separation at the opposite flat wall. The thin separation bubble is characterized with a reversal flow fraction. Intense vortices are generated near the separation line on the lower wall but also at the upper wall. Turbulent normal stresses and kinetic energy budget are investigated along the channel.Comment: 23 pages, submitted to Journal of Turbulenc

Optimal perturbations and low-frequency oscillations in a separated boundary-layer flow

International audienceA separated boundary-layer flow at the rear of a bump is considered. The flow undergoes two-dimensional low-frequency global oscillations known as 'flapping' typical for elongated separation bubbles. Computing equilibrium stationary states of the Navier-Stokes equations and performing a global instability analysis, the onset of the two-dimensional instability is shown to be characterized by a family of modes with localized structures around the reattachment point becoming almost simultaneously unstable. The optimal perturbation analysis, by projecting the initial disturbance on the set of temporal eigenmodes, reveals that the non-normal modes are able to describe localized initial perturbations associated with large transient energy growth. At larger time a global oscillation is found accompanied by a periodic regeneration of the flow perturbation inside the bubble, as the consequence of non-normal cancellation of modes. The low-frequency of the resulting beating behavior is retrieved when applying the optimal initial perturbation to Navier-Stokes time integration. Exploring the possibility of model reduction using temporal two-dimensional instability modes, a low-dimensional feedback controller is designed, performing a Petrov/Galerkin projection based on the bi-orthogonality between the direct and adjoint modes. The low-dimensional controller is shown to be able to damp the full linear instability dynamics

Determination of laccase from the Amazonian trametes elegans strain using the medium supplemented with Brazil nut (bertholletia excelsa) meal, collected in the municipality of Alvarães / Am

Atualmente vários estudos estão sendo desenvolvidos para utilização de enzimas fúngicas em várias aplicações industriais. Poucos ou raros são estudos feitos nesse sentido com fungos pertencentes à biodiversidade Amazônica. A lacase (p-difenol; dioxigêniooxidoredutase EC 1.10.3.2) é uma polifenol oxidase que atua sobre uma variedade de doadores de hidrogênio aromáticos e espécies inorgânicas, incluindo íons Mn+2. A ampla gama de substratos sobre os quais a lacase pode atuar é uma característica que direciona seu emprego na biorremediação de ambientes complexos. Dada relevância da presente pesquisa e ressaltando o aproveitamento de resíduos, que se busca incrementar pesquisas no que se refere à determinação da enzima lacase, utilizou-se o resíduo da casca da Castanha do Brasil, estes foram lavados, colocados em estufa elétrica a 40º para eliminação da umidade e em seguida triturados em moinho de facas a 60 mesh. A “farinha” produzida foi utilizada como substrato de crescimento em meio líquido; onde o meio de cultivo foi incubado a 30ºC em fase estacionária e em triplicata. O substrato seringaldazina foi utilizado para determinação da enzima lacase, através do método que se baseia na oxidação do substrato enzimático seringaldazina para sua forma de quinona, o substrato de crescimento em fase estacionária apresentou atividade de lacase para a cepa Amazônica Trametes elegans, determinados por espectrofotômetro de absorbância.Currently several studies are being developed for use of fungal enzymes in various industrial applications. Few studies are rare or that direction with fungi belonging to Amazonian biodiversity. Laccase (p-diphenol; dioxigêniooxidoredutase EC 1.10.3.2) is a polyphenol oxidase that acts on a variety of aromatic hydrogen donor and inorganic species, including two Mn ions. A wide range of substrates on which the laccase can act is a feature that directs its use in bioremediation of complex environments. Given the relevance of this study and highlighting the utilization of residues, which seeks to increase research with regard to the determination of laccase enzyme, we used the residue of the peel Brazil nuts, they were washed, placed in electric oven at 40 ° for elimination of moisture and then ground into knife mill to 60 mesh. A "flour" produced was used as a substrate for growth in liquid medium, where the culture medium was incubated at 30 ° C in stationary phase and in triplicate. The substrate syringaldazine was used for determination of laccase enzyme, the method which relies on the oxidation of syringaldazine enzyme substrate to form a quinone, the growth substrate in the stationary phase showed laccase activity for Trametes elegans strain Amazon determined by spectrophotometer absorbance

FG-Cloud : Cloud communautaire distribué à vocation scientifique

National audienc