Estudo da transferência de massa por volatilização de compostos odorantes a partir de superfícies líquidas quiescentes
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Data
2015-03-31
Autores
Lovatte, Enilene Regina
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Universidade Federal do Espírito Santo
Resumo
This work aims to study the turbulent flow structures in the water near the gas-liquid interface with negligible deformation and its effects on the transfer of compounds. The Large Eddy Simulation (LES) with dynamical subgrid modelling was used to represent the turbulence using the FLUENT code. The fluid was considered Newtonian, incompressible isothermal. The mathematical model was validated with Direct Numerical Simulation (DNS) data from literature. Numerical simulations were performed with Reynolds number based on the friction velocity equal to 150, 640 and 1280 and Schmidt numbers equal to 1, 200 and 580 thus allowing specific investigation of the effects of these parameters governing the mass transfer phenomenon. The validation results show that the method is appropriate in understanding the transport and turbulence structures visualization (coherent structures) that directly affect the process. Qualitative analysis of the distribution of vorticity surface divergent, scalar instantaneous concentration and scalar concentration fluctuation showed the existence of turbulent structures acting on the carriage of scalar near the free surface. The coherent turbulent structures visualized in the domain have almost longitudinal aspect, existing contra-rotative vortices that act on the formation of vertical upward and downward movements close to the interface. The influence of the Reynolds number is mainly associated with reduced thickness of the diffusive sublayer due to the increase of scalar mixing in the bulk. The turbulence statistics for different Reynolds numbers indicate consistent variations in the results of the flow and transport of the scalar due to the variation of this parameter. The thickness of the diffusive sublayer near the free surface greatly decreases in cases where the Schmidt number increases. With respect to mass transfer coefficient between the cases investigated, the maximum value was obtained for the Reynolds number and the Schmidt number equal to 1, while the corresponding simulation to the Reynolds number of 150 and Schmidt equal to 580 resulting in minimum. The intermediate values of the coefficient increase with increasing Reynolds and decrease with increasing Schmidt.
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LES , Mass transfer , Volatilization , Odorant compounds , Turbulence , Quiescent surfaces , Transferência de Massa , Compostos Odorantes , Simulação das grandes escalas (LES)