Direct numerical simulations of gas-liquid multiphase flows / / by Grétar Tryggvason, Ruben Scardovelli, Stéphane Zaleski [[electronic resource]]

• Record Nr.: UNINA9910781866203321
• Autore: Tryggvason Gretar
• Pubbl/distr/stampa: Cambridge : , : Cambridge University Press, , 2011
• ISBN: 1-107-21807-1; 1-283-34214-6; 1-139-15978-X; 9786613342140; 1-139-16078-8; 1-139-15522-9; 1-139-15873-2; 1-139-15697-7; 0-511-97526-0
• Descrizione fisica: 1 online resource (x, 324 pages) : digital, PDF file(s)
• Disciplina: 532.56
• Soggetti: Multiphase flow - Mathematical models; Gas-liquid interfaces
• Lingua di pubblicazione: Inglese
• Formato: Materiale a stampa
• Livello bibliografico: Monografia
• Note generali: Title from publisher's bibliographic system (viewed on 05 Oct 2015).
• Nota di bibliografia: Includes bibliographic references (p. 295-321) and index.
• Nota di contenuto: Cover; DIRECT NUMERICAL SIMULATIONS OF GAS-LIQUID MULTIPHASE FLOWS; Title; Copyright; Contents; Preface; 1 Introduction; 1.1 Examples of multiphase flows; 1.2 Computational modeling; 1.2.1 Simple flows (Re = 0 and Re = 8); 1.2.2 Finite Reynolds number flows; 1.3 Looking ahead; 2 Fluid mechanics with interfaces; 2.1 General principles; 2.2 Basic equations; 2.2.1 Mass conservation; 2.2.2 Momentum conservation; 2.2.3 Energy conservation; 2.2.4 Incompressible flow; 2.2.5 Boundary conditions; 2.3 Interfaces: description and definitions; 2.4 Fluid mechanics with interfaces; 2.4.1 Mass conservation and velocity conditions2.4.2 Surface tension; 2.4.3 Momentum conservation with interfaces; 2.4.4 Free-surface flow; 2.5 Fluid mechanics with interfaces: the one-fluid formulation; 2.6 ; Nondimensional numbers; 2.7 Thin films, intermolecular forces, and contact lines; 2.7.1 Disjoining pressure and forces between interfaces; 2.7.2 Contact line statics and dynamics; 2.8 Notes; 2.8.1 Fluid and interface mechanics; 2.8.2 Thin films and contact lines; 3 Numerical solutions of the Navier-Stokes equations; 3.1 Time integration; 3.2 Spatial discretization; 3.3 Discretization of the advection terms3.4 The viscous terms; 3.5 The pressure equation; 3.6 Velocity boundary conditions; 3.7 Outflow boundary conditions; 3.8 Adaptive mesh refinement; 3.9 Summary; 3.10 Postscript: conservative versus non-conservative form; 4Advecting a fluid interface; 4.1 Notations; 4.2 Advecting the color function; 4.3 The volume-of-fluid (VOF) method; 4.4 Front tracking; 4.5 The level-set method; 4.6 Phase-field methods; 4.7 The CIP method; 4.8 Summary; 5 The volume-of-fluid method; 5.1 Basic properties; 5.2 Interface reconstruction; 5.2.1 Convergence order of a reconstruction method5.2.2 Evaluation of the interface unit normal; 5.2.3 Determination of a; 5.3 Tests of reconstruction methods; 5.3.1 Errors measurement and convergence rate; 5.3.2 Reconstruction accuracy tests; 5.4 Interface advection; 5.4.1 Geometrical one-dimensional linear-mapping method; 5.4.2 Related one-dimensional advection methods; 5.4.3 Unsplit methods; 5.5 Tests of reconstruction and advection methods; 5.5.1 Translation test; 5.5.2 Vortex-in-a-box test; 5.6 Hybrid methods; 6 Advecting marker points: front tracking; 6.1 The structure of the front; 6.1.1 Structured two-dimensional fronts6.1.2 Unstructured fronts; 6.2 Restructuring the fronts; 6.3 The front-grid communications; 6.3.1 Locating the front on the fixed grid; 6.3.2 Interpolation and smoothing; 6.4 Advection of the front; 6.5 Constructing the marker function; 6.5.1 Constructing the marker function from its gradient; 6.5.2 Construction of the volume fraction from the front location; 6.6 Changes in the front topology; 6.7 Notes; 7 Surface tension; 7.1 Computing surface tension from marker functions; 7.1.1 Continuous surface force method; 7.1.2 Continuous surface stress method; 7.1.3 Direct addition and elementary smoothing in the VOF method
• Sommario/riassunto: Accurately predicting the behaviour of multiphase flows is a problem of immense industrial and scientific interest. Modern computers can now study the dynamics in great detail and these simulations yield unprecedented insight. This book provides a comprehensive introduction to direct numerical simulations of multiphase flows for researchers and graduate students. After a brief overview of the context and history the authors review the governing equations. A particular emphasis is placed on the 'one-fluid' formulation where a single set of equations is used to describe the entire flow field and interface terms are included as singularity distributions. Several applications are discussed, showing how direct numerical simulations have helped researchers advance both our understanding and our ability to make predictions. The final chapter gives an overview of recent studies of flows with relatively complex physics, such as mass transfer and chemical reactions, solidification and boiling, and includes extensive references to current work.

Methods for characterizing a radiation detector for specifying radiation fields during testing against standards for homeland security applications / / A. L. Sallaska; L. Pibida; B. Minniti; C. M. O Brien

• Record Nr.: UNINA9910711380103321
• Autore: Sallaska A. L
• Pubbl/distr/stampa: Gaithersburg, MD : , : U.S. Dept. of Commerce, National Institute of Standards and Technology, , 2016
• Descrizione fisica: 1 online resource (17 pages) : illustrations (color)
• Collana: NIST technical note ; ; 1916
• Altri autori (Persone): MinnitiB; O'BrienC. M (Carl M.); PibidaLeticia; SallaskaA. L
• Soggetti: Detection; Homeland security; Radiation
• Lingua di pubblicazione: Inglese
• Formato: Materiale a stampa
• Livello bibliografico: Monografia
• Note generali: April 2016.; Contributed record: Metadata reviewed, not verified. Some fields updated by batch processes.; Title from PDF title page (viewed April 30, 2016).
• Nota di bibliografia: Includes bibliographical references.
• Sommario/riassunto: A wide variability exists among commercial radiation detection instruments used to measure exposure rate or ambient dose equivalent rate. These instruments are used to measure both the radiation background and the radiation field produced by radioactive sources that are used to test other types of radiation detection systems against different consensus document standards. Most radiation fields specified in the ANSI standard are quite low, ranging from 0.05 Sv/h to 0.5 Sv/h above background. Due to the radiation fields being so low in intensity, the uncertainty of the measurements made with these instruments can be potentially quite large. As a result of these large uncertainties, it is possible that the response of the various parameters being tested by the standards (e.g., alarm indication, radionuclide ; identification) will be dependent on the specific radiation detector employed by the testing laboratory. In this work, we used two different methods to set the radiation fields to analyze the differences that can be expected. One method is based on measurements performed with a high pressure ion chamber while the second method is based on calculating the radiation fields from a known source activity using a point source estimate. The sources of uncertainties in both methods are identified and are reflected in the differences that can be expected in setting the radiation fields. In order to achieve consistency across different testing laboratories in setting radiation fields, we provide insight to what are the most relevant factors that affect the determination of the field using either one of the two methods.