Sharif Digital Repository

Drop penetration into the capillary tube, as a classical problem, has been studied over 100 years. But there are a few studies that investigate forced impregnation of capillary tubes, which has major application in coating, inkjet printing and rain drop penetration into the soil, have been made. A comprehensive numerical investigation on millimeter droplet impact dynamics on a thick capillary tube with micrometer sized pore is conducted and validated against experimental data. This work is extended to oblique impact of drops into pores and normal impact on nanoscaled pores. We apply the finite volume numerical method to solve the time-dependent governing equations of continuity, momentum in... 

When a liquid drop impacts on a hot non-flat surface the curvature of the surface and its geometrical characteristics transmute the physical regimes and their boundary compared to a flat surface impact. The present experimental study is focused on water drop impingement on the mimetic solid semi-cylindrical convex and concave hot surfaces. The thermal versus inertia map of generated regimes is obtained, while some well-known regimes associated with a flat surface are not observed for the present non-flat impacts. The maximum spreading of the droplet is measured at different surface temperatures and impact Weber numbers for the case of droplet impingement on the convex surface. In directrix... 

Spray-wall impingement is one of the phenomenon that associated in different subject such as spray cooling, combustion chamber and gas turbine. With the impingement of spray to the wall, liquid film begins to form. Wall film characteristics is still an important subject to study. Due to the various stages of liquid film formation from injection of spray till spray-wall impingement, the investigation of this phenomenon is far more complicated. This paper is meant to provide detailed data on spray-wall impingement and wall film formation physics with the help of computational analysis of OpenFOAM . A Lagrangian-Eulerian method based on discrete phase model (DPM) was employed to model... 

Encompassing an interaction between the phase change material (PCM) and the droplets of a heat transfer fluid, the direct contact (DC) method provides a state-of-the-art solution for the meager melting and solidification rates of PCMs. In the DC procedure, when impinging on the molten PCM pool, droplets evaporate, solidifying the portion of the PCM. For the first time, the impact of single and simultaneous double ethanol droplets, having an average diameter of 2.68 mm, on the molten paraffin wax has been scrutinized exhaustively. Experiments have been carried out through high-speed imaging for various Weber numbers ranging from 179 to 464, pool temperatures from 70 to 95°C, and horizontal... 

Improving the discharge process of phase-change materials (PCMs) is of great importance. In this study, the process of acetone drop impact on molten paraffin, as a direct-contact solidification method, is experimentally investigated. Four Weber numbers (corresponding to heights of 10, 20, 30, and 40 cm) for the acetone drop and six surface temperatures (66, 68, 70, 75, 80, and 90 °C) for the molten paraffin are considered. As the acetone drop impacts the molten paraffin, the drop absorbs heat from the melting paraffin and boils, solidifying a portion of the molten paraffin. Two important parameters that govern the acetone drop dynamics and the solidification of the molten paraffin are the... 

The impact of droplets is a widely used method for creating direct heat transfer between two fluids. This method enhances heat transfer between the working fluid and the phase change material (PCM). Therefore, a thorough investigation has been carried out on the impact of an acetone droplet on the surface of a pool of molten paraffin, which leads to the simultaneous boiling of the acetone droplet and solidifying part of the paraffin in contact with the acetone. The dynamics of impact, the depth and width of the crater, the jet, and the crown formed as a result of the impact have been reported with varying Weber numbers (ranging from 74 to 375), and the temperature of the pool surface of the... 

In this research, numerical simulation of the impact of a drop on a flat surface with oblique velocity has been performed, using two-phase model of Lattice Boltzmann Method (conservative phase-field). During impact, it is important to investigate two-dimensional drop dynamics and to evaluate the effectiveness of the numerical method used. The model used here restores conservative phase field and preserves mass both locally and globally. In addition, to calculate the slope of the phase field, it calls the center points without engaging finite difference calculations. This makes it efficient for running parallel computations. A fixed dry and hard surface is considered and the drop impacts it... 

Various situations of drop impact on solid surfaces occur widely in natural phenomena and industrial applications, as well as involve in the development of some new technologies, such as, 3D printers, interfacial materials, microfluidics, and biotechnology. Therefore, the relevant investigations have been increasing considerably in the last two decades. Most of these studies are related to the simple case of vertical drop impact on horizontal stationary surfaces, while in most cases vertical/oblique drop impact on horizontal/inclined stationary/moving surfaces in the absence/presence of a crossflow and their various combinations occur. One of the most important situations is drop impact on...