Energy and water vapor transport in a turbulent stratified environment

We present direct numerical simulations about the transport of kinetic energy and unsaturated water vapor across a thin layer which separates two decaying turbulent flows with different energy. This interface lies in a shearless stratified environment modeled by means of Boussinesq’s approximation. Water vapor is treated as a passive scalar (Kumar et al. 2014). Initial conditions have Fr2 between 0.64 and 64 (stable case) and between -3.2 and -19 (unstable case) and Re_lambda = 250. Dry air is in the lower half of the domain and has a higher turbulent energy, seven times higher than the energy of moist air in the upper half. In the early stage of evolution, as long as Fr^2 > 1, stratification plays a minor role and the flows follows closely neutral stratification mixing. As the buoyancy terms grows, Fr2 ~ O(1), the mixing process deeply changes. A stable stratification generates a separation layer which blocks the entrainment of dry air into the moist one, characterized by a relative increment of the turbulent dissipation rate compared to the local turbulent energy. On the contrary, an unstable stratification sligthy enhances the entrainment. Growth-decay of energy and mixing layer thichness are discussed and compared with laboratory and numerical experiments

Coupling traffic models on networks and urban dispersion models for simulating sustainable mobility strategies

The aim of the present paper is to investigate the viability of macroscopic traffic models for modeling and testing different traffic scenarios, in order to define the impact on air quality of different strategies for the reduction of traffic emissions. To this aim, we complement a well assessed traffic model on networks (Garavello, Piccoli, 2006) with a strategy for estimating data needed from the model and we couple it with the urban dispersion model Sirane (Soulhac, 2000)

Stratified zig-zags on vortex pairs using vertically shifted perturbations

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Efeito do mês do parto na taxa de prenhez e no peso ao desmame de bovinos de corte criados extensivamente na sub ? região de Aquidauana.

Objetivou-se com este trabalho verificar o efeito do mês do parto sobre a taxa de prenhez e no peso a desmama de bezerros de vacas aneloradas criadas extensivamente na sub ? região de Aquidauana, Pantanal Sul ? Mato ? Grossense. Foram analisadas informações produtivas de 111 vacas multíparas aneloradas referente ao ano pecuário de 2007 e 2008. As informações da taxa de prenhez da vaca na estação de monta subsequente, o sexo, mês de nascimento e o peso ao desmame de bezerros foram consideradas nas análises. O efeito do mês do parto na taxa de prenhez foi analisado por meio de regressão logística. Na análise de variância verificaram-se os efeitos do sexo, mês de nascimento e a interação entre sexo e mês de nascimento. As informações foram analisadas através do programa estatístico R. As médias dos parâmetros avaliados considerados significativos foram comparadas através do Teste de Tukey a 5% de probabilidade de erro. Vacas com partos realizados no início da estação de nascimento apresentaram maiores taxas de prenhez na estação de monta subsequente (P<0,05). Os efeitos de sexo e mês de nascimento apresentaram interação significativa para o peso ao desmame de bezerros (P<0,05). Nas condições climáticas da sub ? região de Aquidauana, Pantanal Sul ? Mato ? Grossense, o ajuste estratégico da estação de monta visando os nascimentos dos bezerros em períodos de maior oferta de forragem contribui para o melhor desempenho reprodutivo e produtivo do rebanho

Intermittency layers associated to turbulent interfaces

In this study we focus on the transport across an interface which separates two regions with homogeneous and isotropic turbulence in absence of a mean shear. The turbulent transport resulting presents an internal structure. Indeed, in the case of turbulent self-diffusion, both experiments and simulations show that the fluid velocity field is marked by a high intermittency front located aside the interface, which is the source of turbulent bursts penetrating the low turbulence region. The presence of an inner structure inside a layer of turbulence self-transport highlights the different nature of the turbulent transport with respect to the Gaussian diffusion. By including other effects, for instance a passive scalar transport or a mass transport in presence of a density stratification, the phenomenology is much enriched. For instance, our preliminary numerical experiments on the passive scalar transport reveals the presence of two intermittency fronts, one on each side of the interface. As can be seen if the figure below, the intermittency level in the fronts is high. This is true both for the scalar and the scalr derivative statistics. A gradual decay in time is observed while they propagate toward the lateral isotropic regions of the flow. In the presence of a kinetic energy gradient across the interface, the locations and intensity of the intermittency fronts are no more symmetric to respect to the interface. The front on the high energy side of the mixing region penetrates deeper and exhibits stronger intermittency. Analogous features are observed also in two dimensions