Fluxo de massa na interface ar-água em tanques de grades oscilantes e detalhes de escoamentos turbulentos isotrópicos / Gas transfer near the air-water interface in an oscillating-grid tanks and properties of isotropic turbulent flows

AUTOR(ES)

Johannes Gerson Janzen

DATA DE PUBLICAÇÃO

2006

RESUMO

Gas transfer across the air-water interface in turbulent flows is an important process for many environmental systems. To improve the understanding of the basic principles involved in this phenomenon it is necessary to use suitable apparatus and experimental techniques. In this study, experiments and numerical simulation were conducted in a tank with one and two oscillating grids. In the two-grids configuration, experimental data were compared with analytical solutions, obtaining good agreement. Four quantities have been evaluated: turbulent kinetic energy, dissipation rate, eddy viscosity, and length scale. In the one-grid configuration, a microprobe has been used for measurements of oxygen concentration. In addition, the velocity and concentration fields near the interface were measured simultaneously using the combined particle image velocimetry (PIV) - laser induced fluorescence (LIF) technique. With the combined PIV-LIF technique, the total mass flux across the air-water interface could be obtained directly. The qualitative and quantitative results should help guide future work at the subject.

ASSUNTO(S)

turbulence turbulência gas transfer transferência de gases oscillating-grid tank tanque de grade oscilante

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