Download or read book Numerical Simulation of the Droplet surface Impact Using InterFoam written by Fei Gao and published by . This book was released on 2015 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt: Droplet dynamics involves multi-scale forces from inertia body force, interior viscous shear stress to surface tension. The main purpose of this thesis is to simulate the normal impact of a liquid droplet on a hydrophobic surface by solving for the Navier-Stokes equations. The numerical results obtained is used to evaluate the effects of variable parameters on the droplet deformation evolution. The numerical simulation also works as a complimentary part of the experimental exploration, by the group members in the Droplet-Surface Impact Project in Northeastern University. The computational tool used is OpenFOAM, an open source CFD software package licensed and distributed by the OpenFOAM Foundation. The specific solver used is interFoam for this two phase problem. Water is modeled as a representative of the Newtonian fluids, while blood is modeled to represent non-Newtonian fluids. Multiple variables of the droplet-surface impact are investigated numerically: initial velocity, droplet diameter, transport properties, all of which contributes to a variation of the Weber number. The numerical results obtained for water droplets are supported by experimental data and also semi-empirical correlations. The spreading behavior and generation of ripples are in good agreement with that observed in the experimental tests. As the capillary effects become more dominant in the recoiling period, a discrepancy starts to show by a pre-maturely generated secondary droplet in simulation. Possible reasons are speculated for this discrepancy between numerical and experimental results. In the numerical comparison between water and blood droplets, a resemblance of droplet behavior in the initial spreading process is observed, while the recoiling process shows differences: blood droplets rebound in an "irregular" way compared to water droplets. The difference in deformation behaviors caused by varied transport properties leads to a way of distinguishing liquids by simple droplet-surface impact tests.

Download or read book Numerical Simulation of Droplet Impact on Patterned Surfaces written by Christian Moreau and published by . This book was released on 2007 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Simulation of Droplet deformation by a Level Set Approach with Surface Tension written by Roberto Croce and published by . This book was released on 2008 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Droplet Dynamics Under Extreme Ambient Conditions written by Kathrin Schulte and published by Springer Nature. This book was released on 2022 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access book presents the main results of the Collaborative Research Center SFB-TRR 75, which spanned the period from 2010 to 2022. Scientists from a variety of disciplines, ranging from thermodynamics, fluid mechanics, and electrical engineering to chemistry, mathematics, computer science, and visualization, worked together toward the overarching goal of SFB-TRR 75, to gain a deep physical understanding of fundamental droplet processes, especially those that occur under extreme ambient conditions. These are, for example, near critical thermodynamic conditions, processes at very low temperatures, under the influence of strong electric fields, or in situations with extreme gradients of boundary conditions. The fundamental understanding is a prerequisite for the prediction and optimisation of engineering systems with droplets and sprays, as well as for the prediction of droplet-related phenomena in nature. The book includes results from experimental investigations as well as new analytical and numerical descriptions on different spatial and temporal scales. The contents of the book have been organised according to methodological fundamentals, phenomena associated with free single drops, drop clusters and sprays, and drop and spray phenomena involving wall interactions.

Download or read book A Numerical Simulation of Droplet Dynamics in Shear Layers written by Yuefa Xiao and published by . This book was released on 1994 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Simulation of Bubble and Droplet Deformation by a Level Set Approach with Surface Tension in Three Dimensions written by Roberto Croce and published by . This book was released on 2008 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Modeling and Numerical Simulation of Droplet Spreading and Solidification After Impact on a Solid Substrate written by Samuel B. Johnson and published by . This book was released on 2001 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Simulation of Droplet Deformation in Convective Flows written by Zheng-Tao Deng and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book 3D Numerical Study on Droplet solid Collisions in the Leidenfrost Regime written by Yang Ge and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: A 3-dimensional numerical model is developed to simulate the process of collision between an evaporative droplet and a high-temperature solid object in this study. Such phenomena are of direct relevance to many engineering problems. The simulation model of this study is built upon advanced DNS (direct numerical simulation) techniques, coupled with a finite-volume algorithm in the fixed Eulerian grid. The 3D level-set method is employed to portray the droplet surface variation during its deformation. The immersed boundary method is applied to impose the solid-fluid boundary condition at the particle surface. To account for the micro-scale resistant effect induced by the film-boiling evaporation of the droplet, a vapor flow model is developed to calculate the pressure and velocity distributions along the vapor layer between the droplet and the solid. The temperature fields in all phases and the evaporation rate on the droplet surface are illustrated using a full-field heat transfer model. The comparisons of the simulation result with the experimental observation reveal the accuracy of the model, and the convergence is analyzed and verified by using different grid sizes in the computation. For saturated impact, the oscillation of the thickness of the vapor layer and the temperature at solid surface are calculated and compared favorably with the experimental results. The sub-cooled impact yields a thinner vapor layer and a higher heat transfer rate compared to the saturated impacts, and thus the kinetic discontinuity at the liquid-vapor and solid-vapor boundaries in the slip flow regime need to be considered. The effects of the droplet's initial temperature are analyzed using the present model, and it shows that the droplet subcooling degree is significantly related to the thickness of the vapor layer and the heat flux at the solid surface. The collision process between an evaporative droplet and a high-temperature particle is investigated through numerical simulation and the experiment. The effects of the particle size and the collision velocity are examined numerically. Simulation model is further applied to study the oblique collision between the droplet and the particle. The effects of the obliquity on the outcome of the collision are analyzed.

Download or read book Numerical Simulation of Droplet Spreading written by Shiping Hu and published by . This book was released on 1997 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Numerical Simulation of Injection of Droplets in a Compressible Flow written by E. Daniel and published by . This book was released on 1992 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Simulation of Droplets with Dynamic Contact Angles written by and published by . This book was released on 2014 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Simulation of Time dependent Droplet Deformation in an Electric Field written by Graeme M. Supeene and published by . This book was released on 2006 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book OpenFOAM written by J. Miguel Nóbrega and published by Springer. This book was released on 2019-01-24 with total page 527 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains selected papers of the 11th OpenFOAM® Workshop that was held in Guimarães, Portugal, June 26 - 30, 2016. The 11th OpenFOAM® Workshop had more than 140 technical/scientific presentations and 30 courses, and was attended by circa 300 individuals, representing 180 institutions and 30 countries, from all continents. The OpenFOAM® Workshop provided a forum for researchers, industrial users, software developers, consultants and academics working with OpenFOAM® technology. The central part of the Workshop was the two-day conference, where presentations and posters on industrial applications and academic research were shown. OpenFOAM® (Open Source Field Operation and Manipulation) is a free, open source computational toolbox that has a larger user base across most areas of engineering and science, from both commercial and academic organizations. As a technology, OpenFOAM® provides an extensive range of features to solve anything from complex fluid flows involving chemical reactions, turbulence and heat transfer, to solid dynamics and electromagnetics, among several others. Additionally, the OpenFOAM technology offers complete freedom to customize and extend its functionalities.

Download or read book Droplet Impact on Dry Superhydrophobic Surfaces with Micro scale Roughness Elements written by Nadine Boufous and published by . This book was released on 2016 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt: Most aircraft accidents are caused by technical problems or weather-related issues. One cause of weather-related incidents is in-flight icing, which can induce negative performance characteristics and endanger the operation of an airplane. Various researchers investigating the problem of in-flight icing have proposed ice-phobic coatings as one viable solution. For this purpose, it is critical to study the behavior of a droplet impact on different types of surfaces. As an alternative to physical testing, three-dimensional numerical simulation using computational fluid dynamics offers a promising strategy for evaluating the effects of surface characteristics. Using the volume of fluid method, three simulations of high-speed droplet impact on superhydrophobic surfaces with and without micro-scale roughness elements, were generated. The simulations showed that, for the roughness configurations considered, the superhydrophobic surfaces with micro-scale roughness elements were significantly less effective at repelling the droplet than the smooth superhydrophobic surfaces.

Download or read book Numerical Simulation of Near contact Motion and Coalescence of Inertial Droplets in Turbulence written by Melanie Li Sing How and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: We investigate the evolution of the particle size distribution of a coalescing particle field under different conditions in turbulence and the role of hydrodynamic interactions on the coalescing rate for near-contact motion of inertial droplets in quiescent flow. The primary motivation of this work is to understand the evolution of atmospheric clouds. The 10 - 50 microns size range in the cloud droplet growth evolution, often referred to as the 'size gap', is underpredicted by current microphysical models. There is growing consensus that turbulence plays a critical role in accelerating the cloud evolution. The first part of the study was performed using direct numerical simulation (DNS) of an evolving Eulerian fluid velocity field with Lagrangian particle tracking. We present parametric studies of the effects of critical variables on the particle size distribution of an initially monodisperse particle field as it collides and coalesces in turbulence without hydrodynamic interactions. We describe a Collision Optimized Detection Algorithm (CODA), embedded in our DNS turbulence code, to identify and enact particle coalescence in a manner that is optimized for a parallelized architecture. The effects of the particle sub-Kolmorogov size parameter, particle inertia, volume fraction and Reynolds number on the size distribution are systematically investigated. We find that the particle size distribution in turbulence : (i) has an exponential shape in terms of the particle Stokes number, a measure of particle inertia; (ii) has a very weak dependence on Reynolds number; (iii) broadens with decreasing particle Stokes number and decreasing size parameter; and (iv) transitions from an exponential to a power-law behavior at higher volume fractions. In the second part of the study, we investigate the importance of hydrodynamic interactions in near contact motion between the droplets in determining whether a collision leads to molecular contact and coalescence. As the droplets approach, the air in the gap must be squeezed out of the way, which leads to a resistance force that diverges with decreasing gap according to the continuum lubrication theory, preventing contact. At separations on the order of the mean free path of air, the continuum approximation breaks down, and the lubrication flow is described by a non-continuum model. Treating accurately the continuum nature of the gas at the far field and transitioning to a non-continuum model at gap separations comparable to the mean free path of the gas is therefore critical to capture the behavior leading up to contact and eventually coalescence. Building on previous work, which derived a uniformly valid expression for the resistivity to normal motion, we use a similar matched asymptotic expansion technique to derive the uniformly valid resistivity functions for tangential motions. In the third part of the study, we apply the complete set of resistivity functions to a trajectory analysis of droplet pairs settling in quiescent flow to investigate the collision efficiency as a function of the droplet size ratio, Knudsen number and Stokes number. In the near-contact motion, the collision efficiency increases with increasing pairwise droplet inertia and size ratio. It is observed to have a larger dependence on the Knudsen number for lower Stokes numbers, and the curves approach an asymptotic limit for Stokes numbers below 0.1. The collision efficiency for realistic cloud droplets at 50 microns peaks at 0.82. We conclude by discussing the implications of this work for cloud microphysics modeling and suggest next steps for future research.

Download or read book Numerical Simulation of Droplet Dispersion and Deposition in Pipes written by Xavier Loyseau and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: