Download or read book Numerical Simulation of Oscillation Collision and Coalescence of Drops written by Mohammad Reza Heyrani Nobari and published by . This book was released on 1993 with total page 346 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Numerical Simulations of Drop Collisions written by M. R. H. Nobari and published by . This book was released on 1994 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Head On Collision of Drops written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-05 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: The head-on collision of equal sized drops is studied by full numerical simulations. The Navier-Stokes equations are solved for fluid motion both inside and outside the drops using a front tracking/finite difference technique. The drops are accelerated toward each other by a body force that is turned off before the drops collide. When the drops collide, the fluid between them is pushed outward leaving a thin later bounded by the drop surface. This layer gets progressively thinner as the drops continue to deform and in several of the calculations this double layer is artificially removed once it is thin enough, thus modeling rupture. If no rupture takes place, the drops always rebound, but if the film is ruptured the drops may coalesce permanently or coalesce temporarily and then split again. Nobari, M. R. and Jan, Y.-J. and Tryggvason, G. Glenn Research Center NSF CTS-91-32140; NCC3-233; NAG3-1317; RTOP 505-90-5K...
Download or read book Second Microgravity Fluid Physics Conference written by and published by . This book was released on 1994 with total page 494 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Numerical Simulation of the Head on Collisions of Two Equal sized Drops written by Xueli Jiang and published by . This book was released on 2006 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Head on Collision of Drops A Numerical Investigation written by and published by . This book was released on 1993 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Head on Collision of Drops a Numerical Investigation written by M. R. Nobari and published by . This book was released on 1993 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Third Microgravity Fluid Physics Conference written by and published by . This book was released on 1977 with total page 916 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 Computational Studies of Bubble Dynamics written by Yi-Jou Jan and published by . This book was released on 1994 with total page 460 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Numerical Simulations of High Speed Droplet Collision written by Roman Adrien Blancher and published by . This book was released on 2002 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Particle Methods for Multi Scale and Multi physics written by Moubin E. T. Al LIU and published by World Scientific. This book was released on 2015-12-28 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multi-scale and multi-physics modeling is useful and important for all areas in engineering and sciences. Particle Methods for Multi-Scale and Multi-Physics systematically addresses some major particle methods for modeling multi-scale and multi-physical problems in engineering and sciences. It contains different particle methods from atomistic scales to continuum scales, with emphasis on molecular dynamics (MD), dissipative particle dynamics (DPD) and smoothed particle hydrodynamics (SPH). This book covers the theoretical background, numerical techniques and many interesting applications of the particle methods discussed in this text, especially in: micro-fluidics and bio-fluidics (e.g., micro drop dynamics, movement and suspension of macro-molecules, cell deformation and migration); environmental and geophysical flows (e.g., saturated and unsaturated flows in porous media and fractures); and free surface flows with possible interacting solid objects (e.g., wave impact, liquid sloshing, water entry and exit, oil spill and boom movement). The presented methodologies, techniques and example applications will benefit students, researchers and professionals in computational engineering and sciences --
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2007 with total page 1044 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 994 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Eighth Conference of Space Simulation written by and published by . This book was released on 1975 with total page 884 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Acoustic Droplet Vaporization for Diagnostic and Therapeutic Applications written by Oliver D. Kripfgans and published by . This book was released on 2002 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt:
