Sharif Digital Repository

In this research, droplet motion in symmetric and asymmetric junctions in micro and nano scales was investigated. Droplets motion in symmetric and asymmetric junctions have many applications in many industries such as chemical and pharmacy. In this research symmetric T-junction in micro and nano sizes was simulated numerically in 2D and 3D formes. Also asymmetric T-junction (with unequal width branches) was simulated numerically in two cases, 2D and 3D. In the asymmetric T-junction, also an analyrical theory was developed. Numerical simulation was performed by using VOF techniqe and analytical theory was developed by thin film theory. For verifying the accuracy of numerical solution, grid... 

Entrance of air to close water conduits occurs in many ways. This phenomenon makes displeasing effects on water transport structures. Two-phase flows in closed conduits are studied experimentally, numerically and theoretically. Even after decades, due to the complexity of the subject, these studies still require development and reformation. Numerical and theoretical two-phase models are often limited to a special regime of flow."Volume Of Fluid"(VOF) is a model for non-mixing two-phase flows. "Fluent" software uses this model in this field of flows. Volume of fluid is used successfully in some problems like dam break or rising bubbles. Main disadvantage of this model is distribution of the... 

In the present study a through comparison has been made between different free surface modeling methods. Methods for improving the current schemes are analyzed and studied. Among different proposed methods and based on the current in-house CFD solver’s limitations and capabilities, the Flux-Blending Strategy has been used for interface capturing in the framework of the Finite Volume Method (FVM). The proposed scheme has been coupled with other algorithms for improving the capabilities and functionality of the general computational fluid dynamic software, NUMELS, in order to simulate fluid flows with sharp interface.
The improved interface capturing scheme uses the continuous switching... 

Dense underflows are continuous currents that move down-slope due to their density being heavier than that of the ambient water. This difference between the dense fluid and environment fluid can be due to temperature difference, chemical materials, solved materials or suspend solid particles. In these currents, the effect of buoyancy force is produced by this difference density. In this research, many experiments performed in different flow rates, slopes and concentrations to understand the current structure and turbulence specification of the salt solution density currents and particle-laden density currents. Acoustic Doppler Velocimeter is used to measure the velocity fluctuations. The...