Lagrangian Vortex Computations of a Four Tidal Turbine Array: An Example Based on the NEPTHYD Layout in the Alderney Race

This study investigates the wake interaction of four full-scale three-bladed tidal turbines with different ambient turbulence conditions, in straight and yawed flows. A three-dimensional unsteady Lagrangian Vortex Blob software is used for the numerical simulations of the turbines’ wakes. In order to model the ambient turbulence in the Lagrangian Vortex Method formalism, a Synthetic Eddy Method is used. With this method, turbulent structures are added in the computational domain to generate a velocity field which statistically reproduces any ambient turbulence intensity and integral length scale. The influence of the size of the structures and their density (within the study volume) on the wake of a single turbine is studied. Good agreement is obtained between numerical and experimental results for a high turbulence intensity but too many structures can increase the numerical dissipation and reduce the wake extension. Numerical simulations of the four turbine array with the layout initially proposed for the NEPTHYD pilot farm are then presented. Two ambient turbulence intensities encountered in the Alderney Race and two integral length scales are tested with a straight flow. Finally, the wakes obtained for yawed flows with different angles are presented, highlighting turbine interactions

Genomic Analysis of Staphylococcus aureus of the Lineage CC130, Including mecC -Carrying MRSA and MSSA Isolates Recovered of Animal, Human, and Environmental Origins

Most methicillin resistant Staphylococcus aureus (MRSA) isolates harboring mecC gene belong to clonal complex CC130. This lineage has traditionally been regarded as animal-associated as it lacks the human specific immune evasion cluster (IEC), and has been recovered from a broad range of animal hosts. Nevertheless, sporadic mecC-MRSA human infections have been reported, with evidence of zoonotic transmission in some cases. The objective of this study was to investigate the whole-genome sequences of 18 S. aureus CC130 isolates [13 methicillin-resistant (mecC-MRSA) and five methicillin-susceptible (MSSA)] from different sequences types, obtained from a variety of host species and origins (human, livestock, wild birds and mammals, and water), and from different geographic locations, in order to identify characteristic markers and genomic features. Antibiotic resistance genes found among MRSA-CC130 were those associated with the SSCmecXI element. Most MRSA-CC130 strains carried a similar virulence gene profile. Additionally, six MRSA-CC130 possessed scn-sak and one MSSA-ST130 had lukMF’. The MSSA-ST700 strains were most divergent in their resistance and virulence genes. The pan-genome analysis showed that 29 genes were present solely in MRSA-CC130 (associated with SCCmecXI) and 21 among MSSA-CC130 isolates (associated with phages). The SCCmecXI, PBP3, GdpP, and AcrB were identical at the amino acid level in all strains, but some differences were found in PBP1, PBP2, PBP4, and YjbH proteins. An examination of the host markers showed that the 3’ region of the bacteriophage φ3 was nearly identical to the reference sequence. Truncated hlb gene was also found in scn-negative strains (two of them carrying sak-type gene). The dtlB gene of wild rabbit isolates included novel mutations. The vwbp gene was found in the three MSSA-ST700 strains from small ruminants and in one MSSA-ST130 from a red deer; these strains also carried a scn-type gene, different from the human and equine variants. Finally, a phylogenetic analysis showed that the three MSSA-ST700 strains and the two MSSA-ST130 strains cluster separately from the remaining MRSA-CC130 strains with the etD2 gene as marker for the main lineage. The presence of the human IEC cluster in some mecC-MRSA-CC130 strains suggests that these isolates may have had a human origin

Genomic Analysis of Staphylococcus aureus of the Lineage CC130, Including mecC -Carrying MRSA and MSSA Isolates Recovered of Animal, Human, and Environmental Origins

Most methicillin resistant Staphylococcus aureus (MRSA) isolates harboring mecC gene belong to clonal complex CC130. This lineage has traditionally been regarded as animal-associated as it lacks the human specific immune evasion cluster (IEC), and has been recovered from a broad range of animal hosts. Nevertheless, sporadic mecC-MRSA human infections have been reported, with evidence of zoonotic transmission in some cases. The objective of this study was to investigate the whole-genome sequences of 18 S. aureus CC130 isolates [13 methicillin-resistant (mecC-MRSA) and five methicillin-susceptible (MSSA)] from different sequences types, obtained from a variety of host species and origins (human, livestock, wild birds and mammals, and water), and from different geographic locations, in order to identify characteristic markers and genomic features. Antibiotic resistance genes found among MRSA-CC130 were those associated with the SSCmecXI element. Most MRSA-CC130 strains carried a similar virulence gene profile. Additionally, six MRSA-CC130 possessed scn-sak and one MSSA-ST130 had lukMF’. The MSSA-ST700 strains were most divergent in their resistance and virulence genes. The pan-genome analysis showed that 29 genes were present solely in MRSA-CC130 (associated with SCCmecXI) and 21 among MSSA-CC130 isolates (associated with phages). The SCCmecXI, PBP3, GdpP, and AcrB were identical at the amino acid level in all strains, but some differences were found in PBP1, PBP2, PBP4, and YjbH proteins. An examination of the host markers showed that the 3’ region of the bacteriophage φ3 was nearly identical to the reference sequence. Truncated hlb gene was also found in scn-negative strains (two of them carrying sak-type gene). The dtlB gene of wild rabbit isolates included novel mutations. The vwbp gene was found in the three MSSA-ST700 strains from small ruminants and in one MSSA-ST130 from a red deer; these strains also carried a scn-type gene, different from the human and equine variants. Finally, a phylogenetic analysis showed that the three MSSA-ST700 strains and the two MSSA-ST130 strains cluster separately from the remaining MRSA-CC130 strains with the etD2 gene as marker for the main lineage. The presence of the human IEC cluster in some mecC-MRSA-CC130 strains suggests that these isolates may have had a human origin

Effect of cinnamon supplementation on resistin and ghrelin in obese diabetic men

The object of this study was to determine the effect of Cinnamomum zeylanicum (cinnamon) on glycemic/lipid balance, resistin and ghrelin. 84 obese Type 2 diabetic patients were assigned in 2 groups which consumed 8 g and 4 g of cinnamon powder. Anthropometric, hormonal and biochemical parameters were measured before and after 10 weeks of treatment. We found that cinnamon decrease BMI and waist circumference respectively of -5.52±1.47 kg/m² and -10.72±6.12 cm for group 2 of and a decrease of -4.45±1.46 kg/m² and -6.86±5.5 cm in group 1. Our results also showed a decrease of the glucose level of -1,173±0, 75 mmol/L in group 2 and -0, 8932±0, 72 mmol/L in group 1 and a decrease of insulin levels of -3.24±2.85 μUI/L in group 2 and -2.54±2.8 μUI/L in group 1. The assays showed that resistin secretion decreased by -2.08±1.09 ng/mL for the 8 g dose and -1.59±0.926 ng/mL for the 4 g dose, and there was an increase in ghrelin secretion of +1.55±2.21 μg/mL for the 8 g dose and + 2.49±1.13 μg/mL for the 4 g dose. The results confirmed the anti-hyperglycemic and hypolipidemic effects of cinnamon opening a new approach to studying how the compounds derived from certain spices regulate the endogenous release of hormones such as ghrelin and resistin for therapeutic intervention

Generalization of stochastic models of turbulent wall pressure for vibro-acoustic studies based on RANS simulations

Le développement d’une couche limite turbulente sur des structures entraîne des vibrations et des nuisances sonores. Celles-ci sont estimées par des calculs vibro-acoustiques qui nécessitent le spectre de pression pariétale turbulente en fréquence-nombre d’onde. Ce spectre est généralement calculé via des modèles empiriques. Or ces modèles ont un domaine de validité très restreint et ne sont pas adaptés pour des écoulements complexes, avec notamment des gradients de pression. Dans ces travaux, une méthode est proposée pour calculer les corrélations spatio-temporelles de pression pariétale à partir d’une solution sous forme intégrale de l’équation de Poisson. Le spectre de pression est obtenu à partir de la transformation de Fourier de ces corrélations. L’expression retenue pour ces dernières fait intervenir les dérivées d’une fonction de Green ainsi que les champs de la vitesse moyenne et des tensions de Reynolds qui sont obtenus par simulation RANS. Elle fait aussi intervenir des coefficients de corrélation de vitesse spatio-temporelle qui doivent être modélisés. Pour cela, un nouveau modèle de coefficient de corrélation spatiale a été développé : l’Extended Anisotropic Model. Le calcul des corrélations et du spectre de pression est réalisé en utilisant une méthode numérique basée sur une stratégie d’échantillonnage adaptatif combinée à du krigeage. Elle permet de réduire le nombre de valeurs de corrélation de pression nécessaires pour obtenir le spectre de pression pariétale et donc de réduire le temps de calcul. La méthode est appliquée à des écoulements de couche limite turbulente sur une plaque plane et sur un profil NACA-0012 avec un gradient de pression adverse.Turbulent boundary layer flows over structures induce vibrations and noise. The latter are estimated by vibro-acoustic studies which require the wavenumber-frequency turbulent wall-pressure spectrum. This spectrum is generally computed via empirical models. However, these models have a very narrow domain of validity and are not adapted for complex flows, in particular with pressure gradients. In this work, a method is proposed to compute space-time wall-pressure correlations from an integral solution of the Poisson equation. The pressure spectrum is obtained by the Fourier transform of these correlations. The expression retained for the pressure correlations involves the derivatives of a Green function as well as the mean velocity field and the Reynolds stresses which are obtained by RANS solutions. It also involves space-time velocity correlation coefficients that have to be modelled. To achieve this, a new model was developed for the spatial correlation coefficients: the Extended Anisotropic Model. To compute the wall-pressure correlations and spectrum, a numerical method based on a self adaptive sampling strategy combined with Kriging is used. It reduces the number of pressure correlation values required to compute the wall-pressure spectrum and thus reduces the computation time. The method is applied to turbulent boundary layer flows over a flat plate and over a NACA-0012 profile with an adverse pressure gradient

A Kriging-based elliptic extended anisotropic model for the turbulent boundary layer wall pressure spectrum

International audienceThe present study addresses the computation of the wall pressure spectrum for a turbulent boundary layer flow without pressure gradient, at high Reynolds numbers, using a new model, the Kriging-based elliptic extended anisotropic model (KEEAM). A space–time solution to the Poisson equation for the wall pressure fluctuations is used. Both the turbulence–turbulence and turbulence–mean shear interactions are taken into account. It involves the mean velocity field and space–time velocity correlations which are modelled using Reynolds stresses and velocity correlation coefficients. We propose a new model, referred to as the extended anisotropic model, to evaluate the latter in all regions of the boundary layer. This model is an extension of the simplified anisotropic model of Gavin (PhD thesis, 2002, The Pennsylvania State University, University Park, PA) which was developed for the outer part of the boundary layer. It relies on a new expression for the spatial velocity correlation function and new parameters calibrated using the direct numerical simulation results of Sillero et al. (Phys. Fluids, vol. 26, 2014, 105109). Spatial correlation coefficients are related to space–time coefficients with the elliptic model of He & Zhang (Phys. Rev. E, vol. 73, 2006, 055303). The turbulent quantities necessary for the pressure computation are obtained by Reynolds-averaged Navier–Stokes solutions with a Reynolds stress turbulence model. Then, the pressure correlations are evaluated with a self-adaptive sampling strategy based on Kriging in order to reduce the computation time. The frequency and wavenumber–frequency wall pressure spectra obtained with the KEEAM agree well with empirical models developed for turbulent boundary layer flows without pressure gradient

Staphylococcus aureus in Animals and Food: Methicillin Resistance, Prevalence and Population Structure. A Review in the African Continent

The interest about Staphylococcus aureus (S. aureus) and methicillin resistant S. aureus (MRSA) in livestock, and domestic and wild animals has significantly increased. The spread of different clonal complexes related to livestock animals, mainly CC398, and the recent description of the new mecC gene, make it necessary to know more about the epidemiology and population structure of this microorganism all over the world. Nowadays, there are several descriptions about the presence of S. aureus and/or MRSA in different animal species (dogs, sheep, donkeys, bats, pigs, and monkeys), and in food of animal origin in African countries. In this continent, there is a high diversity of ethnicities, cultures or religions, as well as a high number of wild animal species and close contact between humans and animals, which can have a relevant impact in the epidemiology of this microorganism. This review shows that some clonal lineages associated with humans (CC1, CC15, CC72, CC80, CC101, and CC152) and animals (CC398, CC130 and CC133) are present in this continent in animal isolates, although the mecC gene has not been detected yet. However, available studies are limited to a few countries, very often with incomplete information, and many more studies are necessary to cover a larger number of African countries

Lagrangian Vortex computations of turbine wakes: recent improvements using Poletto’s Synthetic Eddy Method (SEM) to account for ambient turbulence

International audienceThis paper presents possible techniques for modelling ambient turbulence in the Lagrangian Vortex Method formalism. Due to the fact that regular Synthetic Eddy Method (SEM) already presented in previous studies is not divergence free by definition; improvements were necessary to develop a similar SEM method with such a divergence free property. The recent improvements formulated by R. Poletto give the way to such a possibility. This new Divergence Free Synthetic Eddy Method (DFSEM) is presented here in comparison with the regular SEM. Obtained numerical velocity fields are compared in terms of convergence properties, Power Spectral Density and also Taylor macro-scale. Finally, turbine wakes are computed with both the recent Poletto’s DFSEM and the regular Jarrin’s SEM to highlight differences. At this stage of development, the DFSEM seems very promising even though some improvements are still necessary

Fluctuating load perceived by the downstream turbine in a farm.

International audienceThis paper presents computations of a four tidal turbine array, with a row of three upstream devices and a downstream turbine. The studied configuration is based on the layout initially proposed in the framework of the NEPTHYD project. The simulations were carried out with a three-dimensional unsteady Lagrangian Vortex software. A synthetic eddy method is used to take into account the ambient turbulence encountered in tidal energetic sites. The loads perceived by the turbines are estimated with a lifting line approach, recently added in the software. To study the interaction between the upstream and downstream turbines, numerical velocity maps, wake lines, unsteady velocity variations obtained with numerical probes as well as fluctuations of power and thrust coefficients are presented

Implementing varying blade profile and Reynolds Number in BEMT code

International audienceCost, driven mostly by planned and unplanned maintenance, is the most significant barrier limiting widespread adoption of TECs. Accurate numerical models can be used to predict the structural loads on TECs and help improve their reliability. BEMT offers an efficient method for predicting the performance of TECs. A robust but unoptimized BEMT code, implemented in MATLAB, has been developed at Swansea University. Previous versions of the BEMT code only allowed for inputs of constant blade profile and Reynolds Number which contributed to the inaccuracies of the BEMT model in predicting experimental results. We present a faster and more accurate C++ implementation of the BEMT code. The error between the coefficient of power from the BEMT code and results of laboratory testing at optimum TSR was reduced by 13%. This should in turn improve the design of TEC, reducing their cost and increase their adoption as generators of low carbon energy