Present work is focused on the numerical study of evaporation of sessile liquid droplets on top of smooth solid substrates. The process of evaporation of a sessile liquid droplet has lots of different applications both in industry and research area. This process has been under study for many years, and still it is an actual problem, solution of which can give answers on some fundamental and practical questions. Instantaneous distribution of mass and heat fluxes inside and outside of an evaporating sessile droplet is studied in this research using computer simulations. The deduced dependences of instantaneous fluxes are applied for self-consistent calculations of time evolution of evaporating sessile droplets. The proposed theory of evaporating sessile droplets of liquid has been validated against available experimental data, and has shown a good agreement. Evaporation of surfactant solution droplets is studied experimentally. The theory, proposed for two stages of evaporation, fits experimental data well. An additional evaporation stage, specific for surfactant solutions, is observed and described. Mathematical modelling of this stage requires further research on surfactant adsorption and its influence on the value of receding contact angle. Numerical study of the evaporation of microdroplets is conducted in order to evaluate the significance of different evaporation mechanisms (diffusive and kinetic models of evaporation) and different physical phenomena (Kelvin s equation, latent heat of vaporization, thermal Marangoni convection, Stefan flow).

In this work, we will present experimental and theoretical results concerning adsorption und phase equilibria being influenced by kinetic effects.

[pt] A consideração dos efeitos da incidência de tornados sobre estruturas é prática corrente em vários países, principalmente no que diz respeito a instalações industriais sensíveis, nas quais as conseqüências de uma eventual ocorrência de tal fenômeno são de maior risco. No Brasil, a despeito de múltiplos registros em algumas regiões ao longo dos últimos anos, tais estudos são ainda incipientes. Objetiva-se, em particular, a avaliação de efeitos mecânicos de tornados sobre sistemas estruturais. Para isso, utiliza-se o modelo de campo de vento proposto por Wen (1975), baseado na solução qualitativa de Kuo (1971), e três modelos de pórticos tridimensionais, de alturas 20, 60 e 100 m. Através de ensaios numéricos, apresentam-se as respostas estática, cinemática e dinâmica dessas estruturas quando atingidas pelo tornado modelado. Análise comparativa entre os efeitos de inércia e arrasto é feita e é proposto um espectro de resposta cinemática a tornados. Os efeitos globais são também avaliados, a fim de se inferirem informações gerais sobre os efeitos mecânicos do fenômeno sobre sistemas estruturais. Comparações com a norma brasileira de vento são apresentadas e a simplificação de se considerar a estrutura como ponto material perante o sinistro é avaliada. / [en] The consideration of the effects of the incidence of tornadoes on structures is common in many countries, mainly in sensible industrial installations, in which the consequences of an eventual occurrence of such phenomenon are of large risk. In Brazil, in spite of multiple registers in some regions during the last couple of years, such studies are still incipient. A methodology for the evaluation of tornado mechanical effects on structural systems is presented. For this, the wind field model proposed by Wen (1975), based on the qualitative solution of Kuo (1971) is used, and three models of 3-D framed structures, 20, 60 and 100 m high, are analyzed. Through numerical tests, the static and dynamic response of these structures to a sampling tornado are evaluated and analyzed. Comparative analysis of the inertia and drag effects is made and a tornadic response spectrum is presented. Global effects are also evaluated, in order to infer general information on the mechanical actions of the phenomenon on structural systems. Comparisons with the Brazilian wind code provisions are presented and the simplification of considering the structure as a material point during the analysis is criticized.