Different intermittency for longitudinal and transversal turbulent fluctuations

Scaling exponents of the longitudinal and transversal velocity structure functions in numerical Navier-Stokes turbulence simulations with Taylor-Reynolds numbers up to \rel = 110 are determined by the extended self similarity method. We find significant differences in the degree of intermittency: For the sixth moments the scaling corrections to the classical Kolmogorov expectations are $\delta\xi_6^L= -0.21 \pm 0.01$ and \dx_6^T= -0.43 \pm 0.01, respectively, independent of \rel. Also the generalized extended self similarity exponents \rho_{p,q} = \dx_p/\dx_q differ significantly for the longitudinal and transversal structure functions. Within the She-Leveque model this means that longitudinal and transversal fluctuations obey different types of hierarchies of the moments. Moreover, the She-Leveque model hierarchy parameters $\beta^L$ and $\beta^T$ show small but significant dependences on the order of the moment.Comment: 20 pages, 10 eps-figures, to appear in Physics of Fluids, December 199

Cultivo protegido de videiras.

bitstream/item/123765/1/FD00024.pd

A new scaling property of turbulent flows

We discuss a possible theoretical interpretation of the self scaling property of turbulent flows (Extended Self Similarity). Our interpretation predicts that, even in cases when ESS is not observed, a generalized self scaling, must be observed. This prediction is checked on a number of laboratory experiments and direct numerical simulations.Comment: Plain Latex, 1 figure available upon request to [email protected]

Multiscale velocity correlation in turbulence: experiments, numerical simulations, synthetic signals

Multiscale correlation functions in high Reynolds number experimental turbulence, numerical simulations and synthetic signals are investigated. Fusion Rules predictions as they arise from multiplicative, almost uncorrelated, random processes for the energy cascade are tested. Leading and sub-leading contribution, in the inertial range, can be explained as arising from a multiplicative random process for the energy transfer mechanisms. Two different predictions for correlations involving dissipative observable are also briefly discussed

Caracterização físicoquímica do mosto e do vinho de uvas Moscato Giallo cultivadas sob cobertura plástica.

O objetivo deste trabalho foi avaliar o efeito da cobertura plástica sobre o mosto e a qualidade do vinho da cultivar Moscato Giallo.bitstream/CNPUV-2009-09/10530/1/cot091.pd

Correlação do acúmulo de horas de frio entre duas estações agroclimatológicas situadas em diferentes posições geográficas no município de Pelotas-RS.

bitstream/item/31643/1/comunicado110.pd

Intermittency of velocity time increments in turbulence

We analyze the statistics of turbulent velocity fluctuations in the time domain. Three cases are computed numerically and compared: (i) the time traces of Lagrangian fluid particles in a (3D) turbulent flow (referred to as the "dynamic" case); (ii) the time evolution of tracers advected by a frozen turbulent field (the "static" case), and (iii) the evolution in time of the velocity recorded at a fixed location in an evolving Eulerian velocity field, as it would be measured by a local probe (referred to as the "virtual probe" case). We observe that the static case and the virtual probe cases share many properties with Eulerian velocity statistics. The dynamic (Lagrangian) case is clearly different; it bears the signature of the global dynamics of the flow.Comment: 5 pages, 3 figures, to appear in PR

Fenologia e requerimento térmico de videira sob cobertura plástica.

O objetivo desse trabalho foi caracterizar a fenologia e o requerimento térmico da videira Vitis vinifera L., cv. Moscato Giallo sob cobertura plástica, nas condições da Serra Gaúcha.bitstream/CNPUV-2009-09/10531/1/cot093.pd

Anatomy, chlorophyll content and photosynthetic potential in grapevine leaves under plastic cover.

o presente trabalho avaliou a anatomia, o teor de clorofila e as respostas fotossintéticas em diferentes níveis de radiação solar em folhas de videiras cultivadas sob cobertura plástica. o experimento foi realizado em vinhedo com a cultivar Moscato Giallo, com e sem cobertura plástica. A avaliação da anatomia foliar foi realizada em 10 plantas, nas áreas coberta e descoberta. No estádio fenológico de mudança de cor das bagas, em cada área, foram coletadas seis folhas expostas à radiação solar e seis sombreadas, as quais foram fixadas e micrografadas (espessuras das epidermes adaxiais e abaxiais e dos parênquimas paliçádicos e lacunosos). O teor de clorofila e o potencial fotossintético foram avaliados na mudança de cor das bagas e após a colheita. A diminuição da radiação solar pela cobertura plástica propicia um incremento da espessura do parênquima paliçádico em folhas expostas e sombreadas. As epidermes adaxiais e abaxiais e o parênquima lacunoso não variam suas espessuras em função da diminuição de radiação solar. O teor de clorofila aumenta nas folhas das plantas cultivadas sob cobertura plástica. o potencial fotossintético das videiras não é afetado pela restrição de radiação solar da cobertura plástica devido à modificação na anatomia das folhas

Experimental test of the Gallavotti-Cohen fluctuation theorem in turbulent flows

We test the fluctuation theorem from measurements in turbulent flows. We study the time fluctuations of the force acting on an obstacle, and we consider two experimental situations: the case of a von K\'arm\'an swirling flow between counter-rotating disks (VK) and the case of a wind tunnel jet. We first study the symmetries implied by the Gallavotti-Cohen fluctuation theorem (FT) on the probability density distributions of the force fluctuations; we then test the Sinai scaling. We observe that in both experiments the symmetries implied by the FT are well verified, whereas the Sinai scaling is established, as expected, only for long times