Download or read book An Evaluation of Computational Methods to Model Large Droplet Secondary Breakup written by Jason Turner and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Ice accretion on aircraft has been, and remains, a long-standing problem in the safe operation of flight vehicles. Ice can cause structural damage when ingested in engines and ruins the aerodynamic properties of lifting surfaces when it attaches to them. Ice accretion is typically simulated using a large scale model of an aircraft, or wing, with droplets treated as a dispersed phase. The dynamics of water droplets in the atmosphere are, thus, approximated with models. These models are tuned to match experimental data from in-flight and wind tunnel tests. Historically, icing from water droplets up to 50 micrometers in Mean Volumetric Diameter (MVD) has been considered. However, safety concerns have risen over the presence of droplets exceeding this size. Supercooled Large Droplets (SLD) are a class of droplets exceeding the 50-micrometer MVD limit. Increased droplet diameter complicates the physics of droplet deposition and breaks some of the assumptions enforced in models. This work attempts to provide a means of investigating the physics of an individual droplet, belonging to SLD regime, as it approaches a body in the most computationally efficient manner possible. A Galilean transformation is employed to isolate an individual droplet from a full model. Streamline data for this droplet is collected and then used as an input for an isolated droplet in a compact fluid domain. The droplet inside this domain is captured using a Volume of Fluid formulation of the Navier-Stokes equations. Early results suggest that assumptions of the stability of large droplets is not as certain as previous literature has suggested. This process can be used in any scenario where it is possible to capture a droplet streamline from an averaged data set.

Download or read book Development of a Computationally Inexpensive Method of Simulating Primary Droplet Breakup written by Brendon Cavainolo and published by . This book was released on 2020 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: Liquid droplet impingement on aircraft can be problematic as it leads to ice accretion. There have been many incidents of aircraft disasters involving ice accretion, such as American Eagle Flight 4184. Understanding liquid droplet impingement is critical in designing aircraft that can mitigate the damages caused by icing. However, the FAA’s regulations are only specified for “Appendix C” droplets; thus, aircraft designs may not be safe when accounting for droplets such as Supercooled Large Droplets. The assumptions of many models, such as the Taylor-Analogy Breakup (TAB) model, are no longer accurate for Supercooled Large Droplets, and the physics of those models break down. Computational modeling is used to simulate droplets in the SLD regime. A Lagrangian reference frame is used in this formulation. In this reference frame, a Volume of Fluid variation of the Navier-Stokes equations is used to resolve and isolate a single droplet. Experimental data shows conflicting results for Weber Number ranges in different primary breakup mechanisms. The goal of this research is to develop a computational model of a water droplet and test it against experimental data. This work shows that the scientific consensus on Weber Number ranges for different breakup modes may not necessarily be accurate, as the computational model agrees with some sets of experimental data but contradicts others.

Download or read book A Computational Model for the Prediction of Droplet Shapes and the Onset of Droplet Breakup written by Mark A. Ruman and published by . This book was released on 1988 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Droplet Deformation Prediction with the Droplet Deformation and Breakup Model written by Mario Vargas and published by BiblioGov. This book was released on 2013-07 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Droplet Deformation and Breakup Model was used to predict deformation of droplets approaching the leading edge stagnation line of an airfoil. The quasi-steady model was solved for each position along the droplet path. A program was developed to solve the non-linear, second order, ordinary differential equation that governs the model. A fourth order Runge-Kutta method was used to solve the equation. Experimental slip velocities from droplet breakup studies were used as input to the model which required slip velocity along the particle path. The center of mass displacement predictions were compared to the experimental measurements from the droplet breakup studies for droplets with radii in the range of 200 to 700 mm approaching the airfoil at 50 and 90 m/sec. The model predictions were good for the displacement of the center of mass for small and medium sized droplets. For larger droplets the model predictions did not agree with the experimental results.

Download or read book Handbook of Atomization and Sprays written by Nasser Ashgriz and published by Springer Science & Business Media. This book was released on 2011-02-18 with total page 922 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atomization and sprays are used in a wide range of industries: mechanical, chemical, aerospace, and civil engineering; material science and metallurgy; food; pharmaceutical, forestry, environmental protection; medicine; agriculture; meteorology and others. Some specific applications are spray combustion in furnaces, gas turbines and rockets, spray drying and cooling, air conditioning, powdered metallurgy, spray painting and coating, inhalation therapy, and many others. The Handbook of Atomization and Sprays will bring together the fundamental and applied material from all fields into one comprehensive source. Subject areas included in the reference are droplets, theoretical models and numerical simulations, phase Doppler particle analysis, applications, devices and more.

Download or read book COMPUTATIONAL METHODS FOR THE INVESTIGATION OF LIQUID DROP PHENOMENA IN EXTERNAL GAS FLOWS written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract : Computational methods for the investigation of drop deformation, drop breakup and drop solidification are developed and implemented in the open source computing environment OpenFOAM® [63]. The goal of this research is to simulate these drop phenomena by resolving all the relevant time and length scales in order to obtain correlations and statistical information which then can be used in the modeling of dispersed multiphase flows such as sprays. The use of such models is central for the simulation of dispersed multiphase flows because present-day computational technology does not have the capacity to resolve millions of droplets, as is typically encountered in sprays. There are three aspects to this thesis. Three types of simulations are performed. First, the two-phase flow solver, interFoam, is modified to allow for simulating a moving droplet in an external airflow within a fixed computational domain. The modified solver is then used for the modeling and simulation of deformation and breakup of drops in axisymmetric and three dimensional symmetric flows, and the results are utilized to validate drop deformation and breakup theories, and to derive statistical information for the product drop size distributions in the various flow regimes. The Taylor Analogy Breakup (TAB) model has been modified and this modified TAB model is also presented and validated. Second, the feasibility and accuracy of calculating convective heat transfer coefficients using CFD is studied for two test cases: the flow between parallel flat plates and the flow past a cylinder. The feasibility and accuracy is demonstrated and achieved by comparing the results with the literature. Third, for the investigation of the solidification of drops, an enhanced enthalpy- porosity model [6] is presented and implemented into OpenFOAM® to form a new solver, modPolyMeltFoam. Two test cases are used to validate the model and its implementation: the pure natural convection of water in a cavity and the solidification of water in a cavity. These tests show that the code performs very well comparing with results from the literature. The code is then coupled with the conjugate heat transfer solver, chtMultiRegionFoam, to create the solver modFluidFluidChtMultiRegionFoam which is able to simulate a stationary water droplet solidifying in a cold airflow. The results of the solidification studies are used to obtain correlations for the convective heat transfer coefficients, which in turn can be utilized in the modeling of freezing sprays where the solidification of millions of droplets needs to be described.

Download or read book Droplets and Sprays Simple Models of Complex Processes written by Sergei S. Sazhin and published by Springer Nature. This book was released on 2022-06-28 with total page 603 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book acts as a guide to simple models that describe some of the complex fluid dynamics, heat/mass transfer and combustion processes in droplets and sprays. Attention is focused mainly on the use of classical hydrodynamics, and a combination of kinetic and hydrodynamic models, to analyse the heating and evaporation of mono- and multi-component droplets. The models were developed for cases when small and large numbers of components are present in droplets. Some of these models are used for the prediction of time to puffing/micro-explosion of composite water/fuel droplets — processes that are widely used in combustion devices to stimulate disintegration of relatively large droplets into smaller ones. The predictions of numerical codes based on these models are validated against experimental results where possible. In most of the models, droplets are assumed to be spherical; some preliminary results of the generalisation of these models to the case of non-spherical droplets, approximating them as spheroids, are presented.

Download or read book Computational Studies for Extending Understanding of Complex Droplet Breakup Mechanisms written by Caroline Jean Anderson and published by . This book was released on 2021 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: Conventional methods of classifying droplet breakup are evaluated in the context of unique variation in environmental and droplet fluid conditions. Most characterization is developed for subsonic speeds and Newtonian fluids, so this study extends understanding on how these forms change to a span of applications outside these conditions. Presented examples include the impact effects on hypersonic vehicles travelling through precipitation, where even smallest of rain drops at such speeds can cause damage. Before the droplet even reaches the vehicle, it interacts with the detached bow shock that leads it. Another example of exceptional recent concern is risk of viral transmission by breakup function within human saliva in sneezes, coughs and speaking. Such biofluid behavior is complicated by viscous and elastic properties, subject to molecular composition that varies person to person by function of their age, gender, and medical conditions.

Download or read book Oil Droplet Impact Dynamics in Aero Engine Bearing Chambers Correlations derived from Direct Numerical Simulations written by Davide Peduto and published by Logos Verlag Berlin GmbH. This book was released on 2015-06-30 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bearing Chambers in Aero-Engines are located near the rolling-element type of bearings which support the shafts and accomodate the resulting thrust loads. One of the main task of the bearing chambers is, beside an efficient scavenging of the lubricating oil, the cooling of the hot compartments. A very complex two-phase air-oil flow takes usually place in these bearing chambers consisting of oil droplet-laden air flows and shear-driven liquid wall films. The interaction of the droplets with the wall films is significantly influencing the wall heat transfer and the cooling performance of these systems. For this reason, a detailed characterization and modelling of the mass and momentum exchange between droplets and wall films for the unique impingement parameter range in bearing chambers is inevitable. This scientific report investigates the oil droplet impact dynamics for typical impingement regimes relevant to aero-engine bearing chambers. The application of a Direct Numerical Simulation (DNS) technique based on the Volume-of-Fluid (VOF) method and coupled with a gradient-based adaptive mesh refinement (AMR) technique allowed to characterize the drop impact dynamics during various single micro- and millimeter drop impacts onto thin and thick films. With the help of a special numerical treatment, a self-perturbing mechanism is installed that leads to the correct resolution of the crown disintegration process. The numerical methodology was thoroughly validated using the experimental results of millimeter sized drop impacts onto deep liquid pools. These results were developed with an enhanced back-illuminated high-speed imaging and Particle Tracking Velocimetry (PTV) technique. New insights into the cavity penetration, the crown's breakup dynamics and the secondary droplet characteristics following a single drop impact have been developed with the help of the isolated variation of different parameters of influence. Particularly the influence of the Froude number, the impingement angle, and the cavity-wall interaction delivered results to date not reported in scientific literature. Beside the advances in fundamental physics describing the drop impact dynamics with the help of the numerical and experimental results, a set of correlations could also be derived. From these correlations, a drop-film interaction model was formulated that is suitable for the parameter range found in bearing chambers.

Download or read book Fluid Dynamics and Transport of Droplets and Sprays written by W. A. Sirignano and published by Cambridge University Press. This book was released on 2010-01-11 with total page 481 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book discusses the theoretical foundations of spray and droplet applications relevant to the technology for active control of sprays applied to new products and applications, improved product performance, cost reductions, and improved environmental outcomes. It also covers theory related to power and propulsion; materials processing and manufacturing technologies including droplet-based net form processing, coating, and painting; medication; pesticides and insecticides; and other consumer uses.

Download or read book Proceedings of the 1st International Conference on Fluid Thermal and Energy Systems written by Sudev Das and published by Springer Nature. This book was released on 2024-01-17 with total page 840 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book comprises the proceedings of the 1st International Conference on Fluid, Thermal and Energy Systems. The contents of this book focus on phase change heat transfer, advanced energy systems, separated flows, turbulence and multi-phase modeling, computational fluid flow and heat transfer, thermal energy storage systems, integrated energy systems, nuclear thermal hydraulics, heat transfer in nanofluids, etc. This book serves as a useful reference to researchers, academicians, and students interested in the broad field of thermo-fluid science and engineering.

Download or read book Emission Control and Fuel Economy written by John H Johnson and published by SAE International. This book was released on 2005-06-27 with total page 700 pages. Available in PDF, EPUB and Kindle. Book excerpt: Emission and fuel economy regulations and standards are compelling manufacturers to build ultra-low emission vehicles. As a result, engineers must develop spark-ignition engines with integrated emission control systems that use reformulated low-sulfur fuel. Emission Control and Fuel Economy for Port and Direct Injected SI Engines is a collection of SAE technical papers that covers the fundamentals of gasoline direct injection (DI) engine emissions and fuel economy, design variable effects on HC emissions, and advanced emission control technology and modeling approaches. All papers contained in this book were selected by an accomplished expert as the best in the field; reprinted in their entirety, they present a pathway to integrated emission control systems that meet 2004-2009 EPA standards for light-duty vehicles.

Download or read book Annular Two Phase Flow written by Geoffrey Hewitt and published by Elsevier. This book was released on 2013-10-22 with total page 327 pages. Available in PDF, EPUB and Kindle. Book excerpt: Annular Two-Phase Flow presents the wide range of industrial applications of annular two-phase flow regimes. This book discusses the fluid dynamics and heat transfer aspects of the flow pattern. Organized into 12 chapters, this book begins with an overview of the classification of the various types of interface distribution observed in practice. This text then examines the various regimes of two-phase flow with emphasis on the regions of occurrence of the annular flow regime. Other chapters consider the single momentum and energy balances, which illustrate the differences and analogies between single- and two-phase flows. This book discusses as well the simple modes for annular flow with consideration to the calculation of the profile of shear stress in the liquid film. The final chapter deals with the techniques that are developed for the measurement of flow pattern, entrainment, and film thickness. This book is a valuable resource for chemical engineers.

Download or read book 41st AIAA ASME SAE ASEE Joint Propulsion Conference Exhibit 10 13 July 2005 Tucson Arizona 05 3950 05 3999 written by and published by . This book was released on 2005 with total page 502 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Classical Nucleation Theory in Multicomponent Systems written by Hanna Vehkamäki and published by Springer Science & Business Media. This book was released on 2006-03-22 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nucleation is the initial step of every first-order phase transition, and most phase transitions encountered both in everyday life and industrial processes are of the first-order. Using an elegant classical theory based on thermodynamics and kinetics, this book provides a fully detailed picture of multi-component nucleation. As many of the issues concerning multi-component nucleation theory have been solved during the last 10-15 years, it also thoroughly integrates both fundamental theory with recent advances presented in the literature. Classical Nucleation Theory in Multicomponent Systems serves as a textbook for advanced thermodynamics courses, as well as an important reference for researchers in the field. The main topics covered are: the basic relevant thermodynamics and statistical physics; modelling a molecular cluster as a spherical liquid droplet; predicting the size and composition of the nucleating critical clusters; kinetic models for cluster growth and decay; calculating nucleation rates; and a full derivation and application of nucleation theorems that can be used to extract microscopic cluster properties from nucleation rate measurements. The assumptions and approximations needed to build the classical theory are described in detail, and the reasons why the theory fails in certain cases are explained. Relevant problems are presented at the end of each chapter.

Download or read book Computational Fluid and Particle Dynamics in the Human Respiratory System written by Jiyuan Tu and published by Springer Science & Business Media. This book was released on 2012-09-18 with total page 383 pages. Available in PDF, EPUB and Kindle. Book excerpt: Traditional research methodologies in the human respiratory system have always been challenging due to their invasive nature. Recent advances in medical imaging and computational fluid dynamics (CFD) have accelerated this research. This book compiles and details recent advances in the modelling of the respiratory system for researchers, engineers, scientists, and health practitioners. It breaks down the complexities of this field and provides both students and scientists with an introduction and starting point to the physiology of the respiratory system, fluid dynamics and advanced CFD modeling tools. In addition to a brief introduction to the physics of the respiratory system and an overview of computational methods, the book contains best-practice guidelines for establishing high-quality computational models and simulations. Inspiration for new simulations can be gained through innovative case studies as well as hands-on practice using pre-made computational code. Last but not least, students and researchers are presented the latest biomedical research activities, and the computational visualizations will enhance their understanding of physiological functions of the respiratory system.

Download or read book One dimensional Two phase Flow written by Graham B. Wallis and published by . This book was released on 1969 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt: