The flow-focusing method is a technology for microfluidic droplet control, and the temperature can effect on the droplet formation. In this study, the droplet formation in the flow-focusing method during the squeezing of dispersed phase by the continuous phase is simulated using CLSVOF, with the consideration of the effects of temperature on droplet size, shape and frequency. The simulation results are consistent with experimental data. The simulated results demonstrate that the droplet size increases with the increase of inlet phase temperature, while the shape regularity and forming frequency decrease, the maximum increase of droplet size is 16%, the biggest drop of droplets number is 29%, and the biggest drop of the roughness parameter is 5%. When the inlet temperatures of the continuous phase are not equal, dripping and jetting are observed in the flow regime of droplet dispersed phase. The mechanism of the temperature influence on droplet formation and the detailed process of droplet formation under different flow regimes are discussed. At the same time, the radial size of droplet breakup point under different flow regimes is compared. The simulation results provide insights in better selection of the control parameters for droplet formation technology.

One of obstacles in simulation of two phase flow is parasite currents. These currents cause unphysical distortion at interface which impairs interface capturing and numerical results. In present study, two methods (using Filter and s-CLSVOF) are implemented in Open FOAM two phase flow solver called inter Foam to reduce parasite current. 3 filters are added to color function volume of fluid (CF-VOF) method. These filters reduce parasite current in different ways, one smoothes color function, one smoothes curvature and the other one compresses the interface. The original and the modified solvers are tested with a quiescent bubble bench mark to investigate the effect of each filter on parasite currents. Then optimum arrangement of filters is compared with s-CLSVOF method and inter Foam. Present study shows parasite current magnitude can be reduced at least up to 50% in the modified solvers. Also, the comparison of pressure jump from numerical results and analytical result with Young-Laplace equation shows modified solvers can predict pressure jump better than original solver. The pressure jump error is reduced up to 400% in the modified solvers. Also present study shows filters have better performance than s-CLVOF method and it can be considered as a suitable substitution of coupled methods.

This research studies the pressure swirl injector’s internal and external flow under adiabatic and incompressible assumptions. A transient three-dimensional flow simulation has been employed. To mitigate computational costs, a periodic simulation approach, wherein only one-quarter of the injector geometry is solved, has been adopted. The Navier-Stokes equations have been solved using the CLSVOF method. This study aims to identify the effects of trumpet angle and orifice length on the flow parameters of the pressure swirl injector. At first, an injector with a trumpet angle is compared with a base injector (BI) with no trumpet angle. The results show that the trumpet angle affects flow by reducing film thickness and spray angle while increasing the velocity magnitude and the axial velocity component. However, the discharge coefficient remains relatively constant compared to the BI. In the second case, and as a novelty of the research, orifice length variations in the trumpet injector (TI) have been studied. The findings indicate that an increase in orifice length from 5 mm to 45 mm leads to an increase in liquid film thickness of about 6.5% and SMD 30%, while the spray angle, velocity magnitude, and axial velocity component decreased by 16%, 23%, and 16%, respectively.

Drop motion on a solid surface has many applications in science and engineering, such as in architecture, offshore structures, and electronics. The present paper aims to simulate the motion of a water droplet located on a hydrophobic inclined surface and investigate its deformation rate using ANSYS FLUENT software. The sessile droplet subjected to uniform airflow can be shed depending on the value of drag and drop’s adhesion forces. In the present work, coupled level set and volume of fluid method are employed to estimate the motion of the interface. The effect of drop size, wind velocity, drop contact angle, and drop size on the location, velocity, and drop deformation is investigated. The results demonstrate that the drop is splashed as the contact angle decreases. The drop acceleration has an approximately constant trend at Reynolds numbers ranging from 8000 to 80,000. The maximum acceleration corresponds to the hydrophilic surface and is equal to 0.9 m/s2. As the contact angle increases, the acceleration becomes constant. For instance, the drop acceleration is about -0.3 for a contact angle of 135°. The results reveal that the drop requires a longer time to reach the lowest point of the inclined surface by decreasing its diameter and increasing surface hydrophobicity and wind velocity. It is found that as surface hydrophobicity increases, the drop reaches the bottom of the surface in a long time in comparison with the deformed drop.