Analysis and thermodynamic modeling of a lattice gas model applied to liquid bridges.

Author(s)

Alexandre Barros de Almeida

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Física (IF/SBI)
• Defense date: 2012-12-10

Examining board members

Adriano Mesquita Alencar; Roberto Fernandes Silva Andrade; Kaline Rabelo Coutinho

• Advisor: Adriano Mesquita Alencar

Abstract

This work studied a three dimension lattice gas model to simulate macroscopic liquid systems. We used the model to study the energy and the forces involved during the process of liquid bridge formation and rupture between two parallel planes. The motivarion of this study was a physiological processes which occur inside the mammals lungs. Furthermore, a study was made to elucidate thermodynamic properties of the model. Concerning to physiological application, it was observed that the free energy of liquid bridge is smaller than the free energy of the droplet, for different liquid systems. With this observation, was proposed that this energy is dissipated as an acoustic energy. This sound should also exist in the rupture of liquid bridge. Comparing the free energy of liquid bridge in the formation and rupture process was observed a hysteresis curve. It was also found an effect of finite size in the formation of small size of the liquid bridge. In the numerical model, the liquid bridge is always formed earlier than expected from the analytical model. In the thermodynamic study, the model was simplified removing both parallel planes. First, the simplest case of this model was studied, only two liquid particles in a large gas lattice. In this case, the specific heat and internal energy was numerically studied and the results was compared with analytical calculation. Subsequently, we carried out a study of the phase transition of this system. Then, the free energy and the force generated between two parallel planes due the presence of the liquid bridge. This studied was performed using two different temperatures and two distinct methods. In the first method the entropy was neglected, and in the second method not. The second method was the ``Overlapping Distribution\'\'. It was concluded that the entropy has a very small effect in the studied conditions. The model is viable for modeling fluids at macroscopic level and therefore can be used to quantify not only the internal forces of the lung structures, but evaluate the energies released after the rupture process of the formation of these bridges. (AU)

• FAPESP's process: 10/13953-8 - Analysis and thermodynamic modeling of liquid bridge ruptures: application to lung fluids
• Grantee: Alexandre Barros de Almeida
• Support Opportunities: Scholarships in Brazil - Master