Coexistence properties of the hard-core attractive Yukawa potential with inverse-range parameter kappa=9, 10, 12, and 15 are calculated by applying canonical Monte Carlo simulation. As previously shown for longer ranges, we show that also for the ranges considered here the coexistence curves scaled by the critical density and temperature obey the law of corresponding states, and that a linear relationship between the critical density and the reciprocal of the critical temperature holds. The simulation results are compared to the predictions of the self-consistent Ornstein-Zernike approximation, and a good agreement is found for both the critical points and the coexistence curves, although some slight discrepancies are present.

Canonical Monte Carlo (NVT-MC) simulations were performed to obtain surface tension and coexistence densities at the liquid-vapor interface of one-site associating Lennard-Jones and hard-core Yukawa fluids, as functions of association strength and temperature. The method to obtain the components of the pressure tensor from NVT-MC simulations was validated by comparing the equation of state of the associative hard sphere system with that coming from isothermal-isobaric Monte Carlo simulations. Surface tension of the associative Lennard-Jones fluid determined from NVT-MC is compared with previously reported results obtained by molecular dynamics simulations of a pseudomixture model of monomers and dimers. A good agreement was found between both methods. Values of surface tension of associative hard-core Yukawa fluids are presented here for the first time.

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ResumenSe realizó una investigación numérica a fin de capturar la formación del vórtice y los parámetros hidrodinámicos (potencia, bombeo, torque, campo de velocidad y disipación viscosa) inducidos por un impulsor de alto corte tipo Hockmeyer ® usando un fluido newtoniano (disolución de glucosa). El estudio se realizó en un tanque cilíndrico sin deflectores a números de Reynolds menores a 138, usando FLUENT ® . La formación del vórtice se simuló empleando el modelo multifásico volumen de fluido (VOF) con un enfoque de marcos de referencia múltiples. En el marco de referencia móvil (región que encierra el impulsor) se utilizó un modelo de transición a turbulento y en el volumen restante un modelo laminar. Se usaron mediciones de potencia para validar las simulaciones. Se encontró que el modelo VOF reproduce en forma aceptable el vórtice alrededor del eje. El campo de velocidad obtenido mostró dos lazos de circulación, uno por arriba y otro por debajo del impulsor, lo cual es característico de impulsores de flujo radial.Palabras clave: parámetros hidrodinámicos; sistema de dispersión de pigmentos; impulsores de alto corte; tanque sin deflectores; disipación viscosa Abstract A numerical study has been done to capture the vortex formation and the hydrodynamic parameters (power draw, pumping, torque, field velocity and viscous dissipation) produced by a High Shear Impeller of two rings Hockmeyer ® type by using a Newtonian fluid (glucose solution). The study was carried out at low Reynolds numbers (Re<138) in an unbaffled cylindrical tank by using FLUENT ® . The multiphase Volume of Fluid model (VOF) was used to capture the vortex formation together with the multiple reference frame approach. In this way, a transition model from laminar to turbulent regimen can be used in the rotation reference frame (the region enclosing the impeller) and in the remaining volume the laminar model can be used. Experimental measurements of power draw were used to validate the computational results. It was found that the VOF model acceptably predicts the vortex formation in the region near the shaft. The velocity field shows two circulation loops above and below the impeller center, which is characteristic of radial flow impellers.