On the influence that the ground electrode diameter has in the propulsion efficiency of an asymmetric capacitor in nitrogen gas

In this work the propulsion force developed in an asymmetric capacitor will be calculated for three different diameters of the ground electrode. The used ion source is a small diameter wire, which generates a positive corona discharge in nitrogen gas directed to the ground electrode. By applying the fluid dynamic and electrostatic theories all hydrodynamic and electrostatic forces that act on the considered geometries will be computed in an attempt to provide a physical insight on the force mechanism that acts on the asymmetrical capacitors, and also to understand how to increase the efficiency of propulsion.Comment: 13 pages, 8 figures, Accepted for publication in "Physics of Plasmas

Controle de cancro-do-enxerto (Lasiodiplodia theobromae (Pat) Griff & Maubl em seringueira utilizando-se a técnica do plantio profundo.

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Assessing multi slot versus single slot pool-type fishways suitability for potamodromous cyprinids: An experimental approach using numerical modelling and fish

Developing new fishway designs that provide suitable hydrodynamic conditions for multiple native freshwater fish species is paramount to mitigate the negative effects of anthropogenic barriers in rivers. This poses an increased challenge in Mediterranean regions, where water availability is limited and issue of conflicting demands. Vertical slot fishways (VSF) are considered one of the best types of technical fishways for potamodromous fish species. However, they generally require a greater amount of water to operate relatively to other type of facilities. The present study used 3D numerical modelling to compare the hydrodynamics and assess the hydraulic suitability for multiple fish species, of a widely used VSF and of two multi slot fishway (MSF) configurations. The MSF configuration requires a lower discharge to operate (\u3e 20% less discharge) than the VSF, while keeping similar flow depths. With the reduction in discharge, the velocity, turbulent kinetic energy and Reynolds shear stress values for MSF are also much lower than the values for VSF (c. 20 – 40% less). Hence, besides requiring smaller discharges than similar VSF design, the MSF seems to be less selective for fish species, particularly smaller-sized individuals, and individuals with weaker swimming capacities. Passage performance of the Iberian barbel, Luciobarbus bocagei (Steindachner, 1864) was subsequently assessed when negotiating a VSF and a MSF in an indoor full scale experimental model. Results showed that the Iberian barbel performed a significantly higher number of movements in the MSF when compared to the VSF. On the other hand, no differences were found in the entrance time, entry efficiency and overall fish performance between configurations. This study shows that numerical modelling complemented with laboratory fish experiments can be an important tool to develop cost-effective fishways

Session D7: Is CFD an Efficient Tool ao Develop Pool Type Fishways?

Abstract: Rivers longitudinal connectivity is compromised by man-made obstacles, such as dams and weirs, which affect fish movements, leading to populations decrease and genetic deterioration. Properly designed fishways re-establish connectivity, allowing for fish migration. The aim of our work is to contribute to a more fast and efficient development of pool-type fishways using hydrodynamic modelling, based on fish behaviour experiments. Modelling free surface flows in hydraulic structures with complex geometry, like pooltype fishways, with aerated and complex flow patterns, represents a significant research challenge. Knowledge already acquired in an experimental full scale indoor pool-type fishway in previous studies is used. A 1:2.5 scaled fishway of this facility was built and used to characterize velocity and turbulence in a pool-type fishway with cross-walls equipped with bottom orifices. An offset orifice configuration was used with consecutive orifices positioned on opposite sides of the cross-walls, creating a sinusoidal flow path. The measurements of velocity fields were made using Particle Image Velocimetry (PIV) and Acoustic Doppler Velocimetry (ADV). Velocity maps were obtained at several positions, for planes parallel to the bottom and parallel to the sidewalls. Parameters that influence fishways efficiency like velocity fields, turbulent kinetic energy and Reynolds shear stresses were determined. A 3D computational fluid dynamics (CFD) model of the fishway was developed using a commercial software FLOW-3D. Velocity fields, turbulent kinetic energy and Reynolds shear stresses were compared with the ones determined from PIV measurements and ADV measurements and results deviations between experimental and numerical data were analyzed. The use of FLOW 3D to simulate mean velocity patterns and flow turbulence in pooltype fishways and its use as design tool for new fishway geometries are discussed

Exploração de caupi em área de varzea do Amapá: informações técnicas.

Neste trabalho são descritas de modo suscinto, algumas práticas que, se seguidas pelo agricultor, em muito contribuirão para que se obtenha sucesso na exploração de feijão caupi em área de várzea do Amapá.bitstream/item/97470/1/CPAF-AP-2000-Exploracao-caupi.PD

Feijão caupi: informações básicas de cultivo no Amapá.

Introdução. Preparo de área. Análise de solo. Calagem e adubação. Semeadura e cultivares. Espaçamento. Controle de plantas daninhas. Controle de pragas. Controle de doenças. Colheita. Beneficiamento e armazenamento.bitstream/item/97871/1/CPAF-AP-1998-Feijao-caupi-informacoes.pd

Recomendações técnicas para o cultivo de feijão caupi (Vigna unguiculata (L.) Walp.) no Estado do Amapá.

Introdução; Clima; Escolha e preparo do solo; Cultivares recomendadas; Época de semeadura; Sistema de plantio; Espaçamento e densidade de Semeadura; Adubação; Controle de ervas daninhas; Principais doenças; Colheita; Beneficiamento e armazenamento; Comercialização; Bibliografia consultada.bitstream/item/97845/1/CPAF-AP-1999-Recomendacoes-feijao.PD