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Tensors and Differential Forms on Vector Spaces
APPENDIX A TENSORS AND DIFFERENTIAL FORMS ON VECTOR SPACES Since only so much of the vast and growing field of differential forms and differentiable manifolds will be actually used in this survey, we shall attempt to briefly review how the calculus of exterior differential forms on vector spaces can serve as a replacement for the more conventional vector calculus and then introduce only the most elementary notions regarding more topologically general differentiable manifolds, which will mostly be used as the basis for the discussion of Lie groups, in the following appendix. Since exterior differential forms are special kinds of tensor fields – namely, completely-antisymmetric covariant ones – and tensors are important to physics, in their own right, we shall first review the basic notions concerning tensors and multilinear algebra. Presumably, the reader is familiar with linear algebra as it is usually taught to physicists, but for the “basis-free” approach to linear and multilinear algebra (which we shall not always adhere to fanatically), it would also help to have some familiarity with the more “abstract-algebraic” approach to linear algebra, such as one might learn from Hoffman and Kunze [ 1], for instance. 1. Tensor algebra. – A tensor algebra is a type of algebra in which multiplication takes the form of the tensor product. a. Tensor product. – Although the tensor product of vector spaces can be given a rigorous definition in a more abstract-algebraic context (See Greub [ 2], for instance), for the purposes of actual calculations with tensors and tensor fields, it is usually sufficient to say that if V and W are vector spaces of dimensions n and m, respectively, then the tensor product V ⊗ W will be a vector space of dimension nm whose elements are finite linear combinations of elements of the form v ⊗ w, where v is a vector in V and w is a vector in W. -
Tensors Notation • Contravariant Denoted by Superscript Ai Took a Vector and Gave for Vector Calculus Us a Vector
Tensors Notation • contravariant denoted by superscript Ai took a vector and gave For vector calculus us a vector • covariant denoted by subscript Ai took a scaler and gave us a vector Review To avoid confusion in cartesian coordinates both types are the same so • Vectors we just opt for the subscript. Thus a vector x would be x1,x2,x3 R3 • Summation representation of an n by n array As it turns out in an cartesian space and other rectilinear coordi- nate systems there is no difference between contravariant and covariant • Gradient, Divergence and Curl vectors. This will not be the case for other coordinate systems such a • Spherical Harmonics (maybe) curvilinear coordinate systems or in 4 dimensions. These definitions are closely related to the Jacobian. Motivation If you tape a book shut and try to spin it in the air on each indepen- Definitions for Tensors of Rank 2 dent axis you will notice that it spins fine on two axes but not on the Rank 2 tensors can be written as a square array. They have con- third. That’s the inertia tensor in your hands. Similar are the polar- travariant, mixed, and covariant forms. As we might expect in cartesian izations tensor, index of refraction tensor and stress tensor. But tensors coordinates these are the same. also show up in all sorts of places that don’t connect to an anisotropic material property, in fact even spherical harmonics are tensors. What are the similarities and differences between such a plethora of tensors? Vector Calculus and Identifers The mathematics of tensors is particularly useful for de- Tensor analysis extends deep into coordinate transformations of all scribing properties of substances which vary in direction– kinds of spaces and coordinate systems. -
AST242 LECTURE NOTES PART 3 Contents 1. Viscous Flows 2 1.1. the Velocity Gradient Tensor 2 1.2. Viscous Stress Tensor 3 1.3. Na
AST242 LECTURE NOTES PART 3 Contents 1. Viscous flows 2 1.1. The velocity gradient tensor 2 1.2. Viscous stress tensor 3 1.3. Navier Stokes equation { diffusion 5 1.4. Viscosity to order of magnitude 6 1.5. Example using the viscous stress tensor: The force on a moving plate 6 1.6. Example using the Navier Stokes equation { Poiseuille flow or Flow in a capillary 7 1.7. Viscous Energy Dissipation 8 2. The Accretion disk 10 2.1. Accretion to order of magnitude 14 2.2. Hydrostatic equilibrium for an accretion disk 15 2.3. Shakura and Sunyaev's α-disk 17 2.4. Reynolds Number 17 2.5. Circumstellar disk heated by stellar radiation 18 2.6. Viscous Energy Dissipation 20 2.7. Accretion Luminosity 21 3. Vorticity and Rotation 24 3.1. Helmholtz Equation 25 3.2. Rate of Change of a vector element that is moving with the fluid 26 3.3. Kelvin Circulation Theorem 28 3.4. Vortex lines and vortex tubes 30 3.5. Vortex stretching and angular momentum 32 3.6. Bernoulli's constant in a wake 33 3.7. Diffusion of vorticity 34 3.8. Potential Flow and d'Alembert's paradox 34 3.9. Burger's vortex 36 4. Rotating Flows 38 4.1. Coriolis Force 38 4.2. Rossby and Ekman numbers 39 4.3. Geostrophic flows and the Taylor Proudman theorem 39 4.4. Two dimensional flows on the surface of a planet 41 1 2 AST242 LECTURE NOTES PART 3 4.5. Thermal winds? 42 5. -
Multilinear Algebra
Appendix A Multilinear Algebra This chapter presents concepts from multilinear algebra based on the basic properties of finite dimensional vector spaces and linear maps. The primary aim of the chapter is to give a concise introduction to alternating tensors which are necessary to define differential forms on manifolds. Many of the stated definitions and propositions can be found in Lee [1], Chaps. 11, 12 and 14. Some definitions and propositions are complemented by short and simple examples. First, in Sect. A.1 dual and bidual vector spaces are discussed. Subsequently, in Sects. A.2–A.4, tensors and alternating tensors together with operations such as the tensor and wedge product are introduced. Lastly, in Sect. A.5, the concepts which are necessary to introduce the wedge product are summarized in eight steps. A.1 The Dual Space Let V be a real vector space of finite dimension dim V = n.Let(e1,...,en) be a basis of V . Then every v ∈ V can be uniquely represented as a linear combination i v = v ei , (A.1) where summation convention over repeated indices is applied. The coefficients vi ∈ R arereferredtoascomponents of the vector v. Throughout the whole chapter, only finite dimensional real vector spaces, typically denoted by V , are treated. When not stated differently, summation convention is applied. Definition A.1 (Dual Space)Thedual space of V is the set of real-valued linear functionals ∗ V := {ω : V → R : ω linear} . (A.2) The elements of the dual space V ∗ are called linear forms on V . © Springer International Publishing Switzerland 2015 123 S.R. -
Tensor Calculus and Differential Geometry
Course Notes Tensor Calculus and Differential Geometry 2WAH0 Luc Florack March 10, 2021 Cover illustration: papyrus fragment from Euclid’s Elements of Geometry, Book II [8]. Contents Preface iii Notation 1 1 Prerequisites from Linear Algebra 3 2 Tensor Calculus 7 2.1 Vector Spaces and Bases . .7 2.2 Dual Vector Spaces and Dual Bases . .8 2.3 The Kronecker Tensor . 10 2.4 Inner Products . 11 2.5 Reciprocal Bases . 14 2.6 Bases, Dual Bases, Reciprocal Bases: Mutual Relations . 16 2.7 Examples of Vectors and Covectors . 17 2.8 Tensors . 18 2.8.1 Tensors in all Generality . 18 2.8.2 Tensors Subject to Symmetries . 22 2.8.3 Symmetry and Antisymmetry Preserving Product Operators . 24 2.8.4 Vector Spaces with an Oriented Volume . 31 2.8.5 Tensors on an Inner Product Space . 34 2.8.6 Tensor Transformations . 36 2.8.6.1 “Absolute Tensors” . 37 CONTENTS i 2.8.6.2 “Relative Tensors” . 38 2.8.6.3 “Pseudo Tensors” . 41 2.8.7 Contractions . 43 2.9 The Hodge Star Operator . 43 3 Differential Geometry 47 3.1 Euclidean Space: Cartesian and Curvilinear Coordinates . 47 3.2 Differentiable Manifolds . 48 3.3 Tangent Vectors . 49 3.4 Tangent and Cotangent Bundle . 50 3.5 Exterior Derivative . 51 3.6 Affine Connection . 52 3.7 Lie Derivative . 55 3.8 Torsion . 55 3.9 Levi-Civita Connection . 56 3.10 Geodesics . 57 3.11 Curvature . 58 3.12 Push-Forward and Pull-Back . 59 3.13 Examples . 60 3.13.1 Polar Coordinates in the Euclidean Plane . -
CONTINUUM MECHANICS for ENGINEERS Second Edition Second Edition
CONTINUUM MECHANICS for ENGINEERS Second Edition Second Edition CONTINUUM MECHANICS for ENGINEERS G. Thomas Mase George E. Mase CRC Press Boca Raton London New York Washington, D.C. Library of Congress Cataloging-in-Publication Data Mase, George Thomas. Continuum mechanics for engineers / G. T. Mase and G. E. Mase. -- 2nd ed. p. cm. Includes bibliographical references (p. )and index. ISBN 0-8493-1855-6 (alk. paper) 1. Continuum mechanics. I. Mase, George E. QA808.2.M364 1999 531—dc21 99-14604 CIP This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonable efforts have been made to publish reliable data and informa- tion, but the author and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage or retrieval system, without prior permission in writing from the publisher. The consent of CRC Press LLC does not extend to copying for general distribution, for promotion, for creating new works, or for resale. Specific permission must be obtained in writing from CRC Press LLC for such copying. Direct all inquiries to CRC Press LLC, 2000 N.W. Corporate Blvd., Boca Raton, Florida 33431. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are only used for identification and explanation, without intent to infringe. -
Downstream Instability of Viscoelastic Flow Past a Cylinder
Proceeding of the 12-th ASAT Conference, 29-31 May 2007 CFD-02 1 12-th International Conference Military Technical College on Kobry El-Kobba Aerospace Sciences & Cairo, Egypt Aviation Technology DOWNSTREAM INSTABILITY OF VISCOELASTIC FLOW PAST A CYLINDER H. KAMAL§*, H. NAJI*, L. THAIS* & G. MOMPEAN* ABSTRACT This work aims at simulating two-dimensional viscoelastic incompressible fluid flow past a non-confined cylinder. The finite volume method is used to descritize the governing equations written in the generalized orthogonal coordinate system. For the viscoelastic constitutive equation, two models are studied; the Oldryod-B model and the Phan-Thien-Tanner model PTT model. The quadratic scheme QUICK is employed to evaluate the convection terms. The terms of diffusion, advection and acceleration are treated explicitly. The Elastic Viscous Split Stresses (EVSS) scheme is used to decompose the stress tensor to enhance the stability of computations. The obtained results indicate that, for Newtonian flow, the onset of von Karman street occurs at Reynolds number Re ≥ 47. Upon the onset of vortex shedding the downstream instability zone is elongated and the shedding frequency is reduced. The PTT model proves more stability of computations and reached higher Deborah numbers. KEY WORDS Viscoelastic Fluids, Generalized Orthogonal Coordinates, Flow past a Cylinder § Egyptian Armed Forces * Laboratoire de Mécanique de Lille, UMR-CNRS 8107 Université des Sciences et Technologies de Lille, Polytech’Lille - Cité Scientifique, 59655 Villeneuve d’Ascq Cedex, France [email protected] Proceeding of the 12-th ASAT Conference, 29-31 May 2007 CFD-02 2 NOMENCLATURE Latin symbols: A cylinder radius. aˆ i covariant base vectors . -
A Mathematica Package for Doing Tensor Calculations in Differential Geometry User's Manual
Ricci A Mathematica package for doing tensor calculations in differential geometry User’s Manual Version 1.32 By John M. Lee assisted by Dale Lear, John Roth, Jay Coskey, and Lee Nave 2 Ricci A Mathematica package for doing tensor calculations in differential geometry User’s Manual Version 1.32 By John M. Lee assisted by Dale Lear, John Roth, Jay Coskey, and Lee Nave Copyright c 1992–1998 John M. Lee All rights reserved Development of this software was supported in part by NSF grants DMS-9101832, DMS-9404107 Mathematica is a registered trademark of Wolfram Research, Inc. This software package and its accompanying documentation are provided as is, without guarantee of support or maintenance. The copyright holder makes no express or implied warranty of any kind with respect to this software, including implied warranties of merchantability or fitness for a particular purpose, and is not liable for any damages resulting in any way from its use. Everyone is granted permission to copy, modify and redistribute this software package and its accompanying documentation, provided that: 1. All copies contain this notice in the main program file and in the supporting documentation. 2. All modified copies carry a prominent notice stating who made the last modifi- cation and the date of such modification. 3. No charge is made for this software or works derived from it, with the exception of a distribution fee to cover the cost of materials and/or transmission. John M. Lee Department of Mathematics Box 354350 University of Washington Seattle, WA 98195-4350 E-mail: [email protected] Web: http://www.math.washington.edu/~lee/ CONTENTS 3 Contents 1 Introduction 6 1.1Overview.............................. -
Appendix a Relations Between Covariant and Contravariant Bases
Appendix A Relations Between Covariant and Contravariant Bases The contravariant basis vector gk of the curvilinear coordinate of uk at the point P is perpendicular to the covariant bases gi and gj, as shown in Fig. A.1.This contravariant basis gk can be defined as or or a gk g  g ¼  ðA:1Þ i j oui ou j where a is the scalar factor; gk is the contravariant basis of the curvilinear coordinate of uk. Multiplying Eq. (A.1) by the covariant basis gk, the scalar factor a results in k k ðgi  gjÞ: gk ¼ aðg : gkÞ¼ad ¼ a ÂÃk ðA:2Þ ) a ¼ðgi  gjÞ : gk gi; gj; gk The scalar triple product of the covariant bases can be written as pffiffiffi a ¼ ½¼ðg1; g2; g3 g1  g2Þ : g3 ¼ g ¼ J ðA:3Þ where Jacobian J is the determinant of the covariant basis tensor G. The direction of the cross product vector in Eq. (A.1) is opposite if the dummy indices are interchanged with each other in Einstein summation convention. Therefore, the Levi-Civita permutation symbols (pseudo-tensor components) can be used in expression of the contravariant basis. ffiffiffi p k k g g ¼ J g ¼ðgi  gjÞ¼Àðgj  giÞ eijkðgi  gjÞ eijkðgi  gjÞ ðA:4Þ ) gk ¼ pffiffiffi ¼ g J where the Levi-Civita permutation symbols are defined by 8 <> þ1ifði; j; kÞ is an even permutation; eijk ¼ > À1ifði; j; kÞ is an odd permutation; : A:5 0ifi ¼ j; or i ¼ k; or j ¼ k ð Þ 1 , e ¼ ði À jÞÁðj À kÞÁðk À iÞ for i; j; k ¼ 1; 2; 3 ijk 2 H. -
Mechanics of Continuous Media in $(\Bar {L} N, G) $-Spaces. I
Mechanics of Continuous Media in (Ln, g)-spaces. I. Introduction and mathematical tools S. Manoff Bulgarian Academy of Sciences, Institute for Nuclear Research and Nuclear Energy, Department of Theoretical Physics, Blvd. Tzarigradsko Chaussee 72 1784 Sofia - Bulgaria e-mail address: [email protected] Abstract Basic notions and mathematical tools in continuum media mechanics are recalled. The notion of exponent of a covariant differential operator is intro- duced and on its basis the geometrical interpretation of the curvature and the torsion in (Ln,g)-spaces is considered. The Hodge (star) operator is general- ized for (Ln,g)-spaces. The kinematic characteristics of a flow are outline in brief. PACS numbers: 11.10.-z; 11.10.Ef; 7.10.+g; 47.75.+f; 47.90.+a; 83.10.Bb 1 Introduction 1.1 Differential geometry and space-time geometry arXiv:gr-qc/0203016v1 5 Mar 2002 In the last years, the evolution of the relations between differential geometry and space-time geometry has made some important steps toward applications of more comprehensive differential-geometric structures in the models of space-time than these used in (pseudo) Riemannian spaces without torsion (Vn-spaces) [1], [2]. 1. Recently, it has been proved that every differentiable manifold with one affine connection and metrics [(Ln,g)-space] [3], [4] could be used as a model for a space- time. In it, the equivalence principle (related to the vanishing of the components of an affine connection at a point or on a curve in a manifold) holds [5] ÷ [11], [12]. Even if the manifold has two different (not only by sign) connections for tangent and co-tangent vector fields [(Ln,g)-space] [13], [14] the principle of equivalence is fulfilled at least for one of the two types of vector fields [15]. -
Viscoelastic Analogy for the Acceleration and Collimation of Astrophysical Jets
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by CERN Document Server Viscoelastic Analogy for the Acceleration and Collimation of Astrophysical Jets Peter T. Williams Department of Physics, University of Florida, Gainesville, FL 32611 1 ABSTRACT Jets are ubiquitous in astronomy. It has been conjectured that the existence of jets is intimately connected with the spin of the central object and the viscous an- gular momentum transport of the inner disk. Bipolar jet-like structures propelled by the viscous torque on a spinning central object are also known in a completely different context, namely the flow in the laboratory of a viscoelastic fluid. On the basis of an analogy of the tangled magnetic field lines of magnetohydrodynamic (MHD) turbulence to the tangled polymers of viscoelastic polymer solutions, we propose a viscoelastic description of the dynamics of highly turbulent conductive fluid. We argue that the same mechanism that forms jets in viscoelastic fluids in the laboratory may be responsible for collimating and powering astrophysical jets by the angular momentum of the central object. Subject headings: MHD — turbulence — stars: winds, outflows — galaxies: jets 1. Introduction Viscoelastic behavior is characteristic of fluids such as polymer suspensions in which long molecular chains become entangled. The deformation and disruption of this entanglement that occurs when the fluid is subjected to shear, and the relaxation to a new entangled state, give such fluids a “memory” that ordinary Newtonian fluids do not have. Egg whites are one common household example. These fluids are in a sense midway between being elastic solids and Newtonian fluids, being more one or the other depending upon the ratio of the relaxation time of the entangled polymers to the deformation time scale. -
Arxiv:1412.2393V4 [Gr-Qc] 27 Feb 2019 2.6 Geodesics and Normal Coordinates
Riemannian Geometry: Definitions, Pictures, and Results Adam Marsh February 27, 2019 Abstract A pedagogical but concise overview of Riemannian geometry is provided, in the context of usage in physics. The emphasis is on defining and visualizing concepts and relationships between them, as well as listing common confusions, alternative notations and jargon, and relevant facts and theorems. Special attention is given to detailed figures and geometric viewpoints, some of which would seem to be novel to the literature. Topics are avoided which are well covered in textbooks, such as historical motivations, proofs and derivations, and tools for practical calculations. As much material as possible is developed for manifolds with connection (omitting a metric) to make clear which aspects can be readily generalized to gauge theories. The presentation in most cases does not assume a coordinate frame or zero torsion, and the coordinate-free, tensor, and Cartan formalisms are developed in parallel. Contents 1 Introduction 2 2 Parallel transport 3 2.1 The parallel transporter . 3 2.2 The covariant derivative . 4 2.3 The connection . 5 2.4 The covariant derivative in terms of the connection . 6 2.5 The parallel transporter in terms of the connection . 9 arXiv:1412.2393v4 [gr-qc] 27 Feb 2019 2.6 Geodesics and normal coordinates . 9 2.7 Summary . 10 3 Manifolds with connection 11 3.1 The covariant derivative on the tensor algebra . 12 3.2 The exterior covariant derivative of vector-valued forms . 13 3.3 The exterior covariant derivative of algebra-valued forms . 15 3.4 Torsion . 16 3.5 Curvature .