Download or read book The Instability Analysis and Direct Numerical Simulation of Turbulent Flows in Electromagnetically Levitated Droplets written by Xin Ai and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulence and Interactions written by Michel Deville and published by Springer Science & Business Media. This book was released on 2010-09-28 with total page 402 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains six keynote lectures and 44 contributed papers of the TI 2009 conference that was held in Saint-Luce, La Martinique, May 31-June 5, 2009. These lectures address the latest developments in direct numerical simulations, large eddy simulations, compressible turbulence, coherent structures, droplets, two-phase flows, etc. The present monograph is a snapshot of the state-of-the-art in the field of turbulence with a broad view on theory, experiments and numerical simulations.

Download or read book Large Eddy Simulations of Turbulence written by M. Lesieur and published by Cambridge University Press. This book was released on 2005-08-22 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: Large-Eddy Simulations of Turbulence is a reference for LES, direct numerical simulation and Reynolds-averaged Navier-Stokes simulation.

Download or read book Direct Numerical Simulation of Droplet laden Isotropic Turbulence written by Michael S. Dodd and published by . This book was released on 2017 with total page 199 pages. Available in PDF, EPUB and Kindle. Book excerpt: Interaction of liquid droplets with turbulence is important in numerous applications ranging from rain formation to oil spills to spray combustion. The physical mechanisms of droplet-turbulence interaction are largely unknown, especially when compared to that of solid particles. Compared to solid particles, droplets can deform, break up, coalesce and have internal fluid circulation. The main goal of this work is to investigate using direct numerical simulation (DNS) the physical mechanisms of droplet-turbulence interaction, both for non-evaporating and evaporating droplets. To achieve this objective, we develop and couple a new pressure-correction method with the volume-of-fluid (VoF) method for simulating incompressible two-fluid flows. The method's main advantage is that the variable coefficient Poisson equation that arises in solving the incompressible Navier-Stokes equations for two-fluid flows is reduced to a constant coefficient equation. This equation can then be solved directly using, e.g., the FFT-based parallel Poisson solver. For a $1024^3$ mesh, our new pressure-correction method using a fast Poisson solver is ten to forty times faster than the standard pressure-correction method using multigrid. Using the coupled pressure-correction and VoF method, we perform direct numerical simulations (DNS) of 3130 finite-size, non-evaporating droplets of diameter approximately equal to the Taylor lengthscale and with 5~\% droplet volume fraction in decaying isotropic turbulence at initial Taylor-scale Reynolds number $\Rey_\lambda=83$. In the droplet-laden cases, we vary one of the following three parameters: the droplet Weber number based on the r.m.s. velocity of turbulence ($0.1 \leq \Webrms \leq 5$), the droplet- to carrier-fluid density ratio ($1 \leq \rho_d/\rho_c \leq 100$) or the droplet- to carrier-fluid viscosity ratio ($1 \leq \mu_d/\mu_c \leq 100$). We derive the turbulence kinetic energy (TKE) equations for the two-fluid, carrier-fluid and droplet-fluid flow. These equations allow us to explain the pathways for TKE exchange between the carrier turbulent flow and the flow inside the droplet. We also explain the role of the interfacial surface energy in the two-fluid TKE equation through work performed by surface tension. Furthermore, we derive the relationship between the power of surface tension and the rate of change of total droplet surface area. This link allows us to explain how droplet deformation, breakup and coalescence play roles in the temporal evolution of TKE. We then extend the code for non-evaporating droplets and develop a combined VoF method and low-Mach-number approach to simulate evaporating and condensing droplets. The two main novelties of the method are: (i) the VOF algorithm captures the motion of the liquid gas interface in the presence of mass transfer due to evaporation and condensation without requiring a projection step for the liquid velocity, and (ii) the low-Mach-number approach allows for local volume changes caused by phase change while the total volume of the liquid-gas system is constant. The method is verified against an analytical solution for a Stefan flow problem, and the $D^2$ law is verified for a single droplet in quiescent gas. Finally, we perform DNS of an evaporating liquid droplet in forced isotropic turbulence. We show that the method accurately captures the temperature and vapor fields in the turbulent regime, and that the local evaporation rate can vary along the droplet surface depending on the structure of the surrounding vapor cloud. We also report the time evolution of the mean Sherwood number, which indicates that turbulence enhances the vaporization rate of liquid droplets.

Download or read book DNS of Wall Bounded Turbulent Flows written by Tapan K. Sengupta and published by Springer. This book was released on 2018-06-07 with total page 393 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book highlights by careful documentation of developments what led to tracking the growth of deterministic disturbances inside the shear layer from receptivity to fully developed turbulent flow stages. Associated theoretical and numerical developments are addressed from basic level so that an uninitiated reader can also follow the materials which lead to the solution of a long-standing problem. Solving Navier-Stokes equation by direct numerical simulation (DNS) from the first principle has been considered as one of the most challenging problems of understanding what causes transition to turbulence. Therefore, this book is a very useful addition to advanced CFD and advanced fluid mechanics courses.

Download or read book Direct Numerical Simulation of Turbulent Droplets Flow with Evaporation written by Yunliang Wang and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mathematics of Large Eddy Simulation of Turbulent Flows written by Luigi Carlo Berselli and published by Springer Science & Business Media. This book was released on 2006 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt: The LES-method is rapidly developing in many practical applications in engineering The mathematical background is presented here for the first time in book form by one of the leaders in the field

Download or read book New Perspectives in Turbulence written by L. Sirovich and published by . This book was released on 1991 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Secondary Instabilities of G rtler Vortices in High Speed Boundary Layers written by Jie Ren and published by Springer. This book was released on 2017-10-27 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis first reveals the mechanism of Görtler instabilities and then demonstrates how transitions at hypersonic flows can be effectively controlled (either promoted or suppressed) with Görtler or Klebanoff modes. It focuses on understanding and controlling flow transitions from mild laminar to fully turbulent flows at high speeds—aspects that have become crucial at the dawn of an incredible era, in which hypersonic vehicles are becoming available. Once this occurs, it will be possible to travel from Beijing to Los Angeles within just 2 hours, and we will all live in a genuinely global village—and not just virtually, but physically. Görtler instabilities have often been used to promote flow transition in hypersonic vehicles. However, how Görtler instabilities are excited and how they evolve in hypersonic flows are questions that have yet to be answered.

Download or read book Wavelet spectral Analysis and Large eddy Simulation Using Neural Networks of Droplet laden Decaying Isotropic Turbulence written by Andreas Freund and published by . This book was released on 2020 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work, we propose new methods for both the analysis and simulation of droplet-laden isotropic turbulence. First, we suggest using the wavelet energy spectrum to study multiphase turbulent flows to overcome the challenges of applying the Fourier energy spectrum to velocity fields with sharp velocity gradients. Also, we propose a new decomposition of the wavelet energy spectrum into three contributions corresponding to the carrier phase, droplets, and interaction between the two. We apply these new wavelet-decomposition tools in analyzing the direct numerical simulation (DNS) data of droplet-laden decaying isotropic turbulence of Dodd & Ferrante (2016, J. Fluid Mech. 806:3560́3412). Our results show that, in comparison to the spectrum of the single-phase case, the droplets (i) do not affect the carrier-phase energy spectrum at high wavenumbers (km/kmin>̲128), (ii) increase the energy spectrum at high wavenumbers (km/kmin>̲256) by increasing the interaction energy spectrum at these wavenumbers, and (iii) decrease the energy at low wavenumbers (km/kmin

Download or read book Theoretical Approaches to Turbulence written by D.L. Dwoyer and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 377 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulence is the lIDst natural nDde of fluid lIDtion, and has been the subject of scientific study for all Dst a century. During this period, various ideas and techniques have evolved to nDdel turbulence. Following Saffman, these theoretical approaches can be broadly divided into four overlapping categories -- (1) analytical lIDdelling, (2) physical lIDdelling, (3) phenomenologicalllDdelling, and (4) nurerical lIDdelling. With the purpose of stmtnarizing our =ent understanding of these theoretical approaches to turbulence, recognized leaders (fluid dynamicists, mathematicians and physicists) in the field were invited to participate in a formal workshop during October 10-12, 1984, sponsored by The Institute for CooIputer Applications in Science and Engineering and NASA Langley Research Center. Kraiciman, McCcxnb, Pouquet and Spiegel represented the category of analytical nDdelling, while Landahl and Saffman represented physical lIDdelling. The contributions of Latmder and Spalding were in the category of phenanenological lIDdelling, and those of Ferziger and Reynolds in the area of nurericalllDdelling. Aref, Cholet, Lumley, Moin, Pope and Temam served on the panel discussions. With the care and cooperation of the participants, the workshop achieved its purpose, and we believe that its proceedings published in this vol\. llre has lasting scientific value. The tone of the workshop was set by two introductory talks by Bushnell and ChaImm. Buslmell presented the engineering viewpoint while Chapman reviewed from a historical perspective developments in the study of turbulence. The remaining talks dealt with specific aspects of the theoretical approaches to fluid turbulence.

Download or read book Progress in Fluid Flow Research written by Herman Branover and published by AIAA (American Institute of Aeronautics & Astronautics). This book was released on 1998 with total page 976 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contains papers from a February 1996 seminar on magnetohydrodynamic (MHD) flows and turbulence, covering contemporary trends in both experimental and theoretical research and presenting recent results in many areas. Subjects include transition, turbulence, MHD and atmospheric turbulence, astrophysics, experimental methods and data analysis, energy conversion, solidification, incompressible flow, and plasma MHD. Some topics are structure of the velocity field of a turbulent line-fire plume, helical instability of magnetohydrodynamic turbulence, energy sources of planetary magnetic fields, and characterization of microfabricated shear stress sensors. No index. Annotation copyrighted by Book News, Inc., Portland, OR

Download or read book Direct and Large eddy Simulation XI written by Maria Vittoria Salvetti and published by . This book was released on 2019 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gathers the proceedings of the 11th workshop on Direct and Large Eddy Simulation (DLES), which was held in Pisa, Italy in May 2017. The event focused on modern techniques for simulating turbulent flows based on the partial or full resolution of the instantaneous turbulent flow structures, as Direct Numerical Simulation (DNS), Large-Eddy Simulation (LES) or hybrid models based on a combination of LES and RANS approaches. In light of the growing capacities of modern computers, these approaches have been gaining more and more interest over the years and will undoubtedly be developed and applied further. The workshop offered a unique opportunity to establish a state-of-the-art of DNS, LES and related techniques for the computation and modeling of turbulent and transitional flows and to discuss about recent advances and applications. This volume contains most of the contributed papers, which were submitted and further reviewed for publication. They cover advances in computational techniques, SGS modeling, boundary conditions, post-processing and data analysis, and applications in several fields, namely multiphase and reactive flows, convection and heat transfer, compressible flows, aerodynamics of airfoils and wings, bluff-body and separated flows, internal flows and wall turbulence and other complex flows.

Download or read book Direct Numerical Simulation of Particle Laden Turbulent Flows in the Particle Lagrangian Reference Frame written by Aureen Cyr Currin and published by . This book was released on 1997 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Direct Numerical and Large Eddy Simulations of a Non Equilibrium Turbulent Kolmogorov Flow written by S. L. Woodruff and published by . This book was released on 1999 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Instabilities of Flows and Transition to Turbulence written by Tapan K. Sengupta and published by CRC Press. This book was released on 2012-04-24 with total page 528 pages. Available in PDF, EPUB and Kindle. Book excerpt: Addressing classical material as well as new perspectives, Instabilities of Flows and Transition to Turbulence presents a concise, up-to-date treatment of theory and applications of viscous flow instability. It covers materials from classical instability to contemporary research areas including bluff body flow instability, mixed convection flows, and application areas of aerospace and other branches of engineering. Transforms and perturbation techniques are used to link linear instability with receptivity of flows, as developed by the author. The book: Provides complete coverage of transition concepts, including receptivity and flow instability Introduces linear receptivity using bi-lateral Fourier-Laplace transform techniques Presents natural laminar flow (NLF) airfoil analysis and design as a practical application of classical and bypass transition Distinguishes strictly between instability and receptivity, which leads to identification of wall- and free stream-modes Describes energy-based receptivity theory for the description of bypass transitions Instabilities of Flows and Transition to Turbulence has evolved into an account of the personal research interests of the author over the years. A conscious effort has been made to keep the treatment at an elementary level requiring rudimentary knowledge of calculus, the Fourier-Laplace transform, and complex analysis. The book is equally amenable to undergraduate students, as well as researchers in the field.

Download or read book Transition to Turbulence written by Tapan K. Sengupta and published by Cambridge University Press. This book was released on 2021-09-30 with total page 643 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Present understanding of transition to turbulence has now been studied over one hundred and fifty years. The path the studies have taken posed it as a modal eigenvalue problem. Some researchers have suggested alternative models without being specific. First-principle based approach of receptivity is the route to build bridges among ideas for solving the Navier-Stokes equation for specific canonical problems. This book highlights the mathematical physics, scientific computing, and new ideas and theories for nonlinear analyses of fluid flows, for which vorticity dynamics remain central. This book is a blend of classic with distinctly new ideas, which establish different dynamics of flows, from genesis to evolution of disturbance fields with rigorously developed methods to tracing coherent structures amidst the seemingly random and chaotic fluid dynamics of transitional and turbulent flows"--