multiphase flow

Based on experimental evidence, the presence of thermocouples in solid phase change materials affects the results and changes the melting regime from unconstrained melting to constrained melting. In this study, a new method for direct measurement of liquid mass fraction of phase change materials during melting was proposed based on the image processing technique. In this method, images of the melting process are prepared in controlled conditions at successive times. By performing image processing techniques, the boundary of the solid core is determined and the enclosed surface area is calculated and divided by the initial surface of the solid phase. This method was applied to unconfined paraffin melting inside a horizontal cylinder. The problem was also numerically simulated by the multi-phase method (VOF) and the change in the total volume of paraffin (total volume of solid and liquid phases) due to the difference between solid and liquid density was taken into account. A good agreement between numerical and experimental results was observed. The shape and sizes of the solid core in the experimental images and the numerical results at different times match well.

In this article, the simulation methods of multiphase flow in the presence of surfactants are classified into 3 categories based on Navier-Stokes, distribution function, and based on intermolecular forces, and each one is described separately. Navier-Stokes-based methods fall into two categories: interface tracking methods and interface capture methods. Methods based on intermolecular forces act as particle-based methods with a Lagrangian perspective in dealing with the flow field. The widely used models in the methods based on the distribution function are also introduced at the end. A wide range of numerical methods has put many choices in front of researchers. Knowing and understanding the capabilities and details of these methods will help to select the most appropriate numerical method and obtain reliable and cost-effective results according to the hardware facilities.

In this article, Surface Active Agents (Surfactants) and its effect on the Multiphase Flow have been studied. First, the functioning of surfactants has been explained. For this purpose, the definitions of surface tension and how it changes in the presence of surfactants have been investigated. Also, the physics of surfactant distribution in multiphase flow and its absorption and repulsion at the interface have been reported. The physical changes of the two-phase interface due to the presence of surfactants have been investigated through the balance of forces and the change in surface tension and the definition of the Marangoni effect. Types of surfactants and their properties are stated. Finally, the important applications of surfactants in industry and daily life are mentioned in detail. This review shows that surfactants as one of the effective factors on multiphase flow need to be studied more and more. A better understanding of these materials can be very useful in manipulating and optimizing multiphase flow applications. 

In this paper, the effect of evaporating sprays of Ethanol and Acetone injected into a cylindrical gaseous environment is numerically investigated. To make this investigation the Eulerian gas phase equations together with the Lagrangian liquid phase equations are solved assuming a two-way coupling between the two phases. According to the results, after a certain time from the start of injection, the overall percentage of total evaporation of acetone becomes significantly higher than ethanol, but at the early spraying time, both alcohols had similar overall evaporation rates. Also, in terms of spray tip penetration, they have almost the same amount of progress and more or less the same behaviour. Also due to the almost identical injection flow rate of the droplets, the effects on the velocity fields in the gas phase have been almost similar. The important point to compare is the gas phase temperature field for both sprays after 1.5 ms of injection. Due to the fact that most of the evaporation occurs when the particles reach boiling temperature and the fact that all the heat required for evaporation is taken from the gas phase, the ambient temperature becomes much lower in ethanol spray because ethanol’s boiling temperature and latent heat are both much higher than acetone.

In order to simulate multiphase flow in the presence of dielectric current using the Lattice Boltzmann Method (LBM), three distribution functions are used, two of which for using the He-Chen-Zhang phase field model and one for solving the potential field. Initially, the ability of the code to apply surface tension was tested using the Laplace law and the drop release test. The results show that the present numerical program is capable of modeling well the regulated surface tension force. Then, the Rayleigh–Taylor instability simulation is used to evaluate the codechr('39')s ability in applying volume forces. The results by the developed numerical program are in good agreement with the numerical results in the references. In this study, for the first time, the effect of electric field on a droplet immersed in another fluid and the presence of droplet in a porous medium is investigated by LBM. For this purpose, first the droplet motion due to the potential difference in the porous and non-porous media is investigated. After modeling the droplet motion due to the potential difference, two electric fields areapplied to the droplet to reverse the droplet deformation. Through various tests, it is shown that at a given potential difference, the droplet breaks down after much deformation and is divided into smaller droplets. The decomposition of droplets in a pre-mixed emulsion is a common technique in the production of monodisperse droplets. The presence of monodisperse droplets in an emulsion improves the physical properties of polymer science experts.