Lecture 2 on Vectors and Tensors 3-7-2008

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Louisiana Tech University Learning Objectives You should be able to: Define and recognize scalars, vectors, and tensors. Describe the difference between continuum and statistical mechanics, the advantages and disadvantages of each, and their applications Understand and perform standard vector and tensor mathematical operations Define the material derivative and use it to convert between spatial and material coordinates and to describe motion in engineering problems Define, calculate, and use pathlines, streamlines, and streaklines for a given flow

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vectors and tensors

Transcript of Lecture 2 on Vectors and Tensors 3-7-2008

Louisiana Tech UniversityRuston, LA 71272Learning ObjectivesYou should be able to!"e#ine and recogni$e scalars, vectors, and tensors%!"escribe the di##erence bet&een continuu' and statistical 'echanics, the advantages and disadvantages o# each, and their a((lications!Understand and (er#or' standard vector and tensor 'athe'atical o(erations!"e#ine the 'aterial derivative and use it to convert bet&een s(atial and 'aterial coordinates and to describe 'otion in engineering (roble's!"e#ine, calculate, and use (athlines, strea'lines, and strea)lines #or a given #lo&Louisiana Tech UniversityRuston, LA 71272*otivating +uestionYou &ish to generate a ,A" 'odel o# an arterial bi#urcation, &hich you re(resent as the union o# t&o cylinders%1% -o& do you describe the hori$ontal cylinder 'athe'atically.2% -o& do you describe the diagonal cylinder 'athe'atically.Louisiana Tech UniversityRuston, LA 71272*otivating +uestion1% -o& do you describe the hori$ontal cylinder 'athe'atically./t de(ends on the coordinate syste' you choose%( ) ( )( ) ( )2 2 2, , , , 0, , , , 0r z f r z r Rxyz f xyz x y R + Louisiana Tech UniversityRuston, LA 71272*otivating +uestion-o& do you describe the diagonal cylinder 'athe'atically.You have already done it #or the hori$ontal cylinder%/# you &ere to choose a coordinate syste' #or &hich the a0is is aligned &ith the $1coordinate, you just need to rotate( )( ) ( )2 2 21 1 1 1 21 1 1, , 01 0 0where , , , , 0 cos sin0 sin cosf x y z x y Rx y z xyz + 1 1 1 1 ]Louisiana Tech UniversityRuston, LA 71272*otivating +uestion( )( ) ( )2 2 21 1 1 1 21 1 1, , 0cos sin 0where , , , , sin cos 00 0 1f x y z x y Rx y z xyz + 1 1 1 1 ]This set o# e2uations loo)s co'(licated, but you &ill not need to &orry about the details%The so#t&are you use &ill ta)e care o# the tedious calculations%Rotation 'atri0 3tensor4vectorLouisiana Tech UniversityRuston, LA 71272*otivating +uestion( )( ) ( )2 2 21 1 1 1 21 1 1 0, , 0where , , , ,f x y z x y Rx y z x x yz + /# you &anted to shi#t the cylinder in the 01direction, you &ould do so'ething li)e this( ) ( ) ( )1 1 1 01 0 0, , , , 0 cos sin , 0, 00 sin cosx y z xyz x 1 1 1 1 ]And i# you &anted to rotate and then shi#tLouisiana Tech UniversityRuston, LA 71272*otivating +uestion/# you &anted a 'ore general rotation( )( ) ( )2 2 21 1 1 1 211 12 131 1 1 21 22 2331 32 33, , 0cos cos coswhere , , , , cos cos coscos cos cosf x y z x y Rx y z xyz + 1 1 1 1 ]5here ij is the angle through &hich the i1a0is in the original coordinate syste' 'ust rotate to align &ith the j1a0is in the ne& coordinate syste'%Louisiana Tech UniversityRuston, LA 71272A0is Rotation612Louisiana Tech UniversityRuston, LA 71272A0is Rotation126126131112Louisiana Tech UniversityRuston, LA 712727ur(ose o# the 8tress Tensor9or solids11 12 133 1 221 22 231 2 331 32 333 1 1 2 11 2 1 3 13 2 1 2 21 2 2 3 23 11 31 0 00 1 00 0 11 12 21 122 212u u ux x xu u u u ux x x x xu u u u uGx x x x xu ux x 11 _ 11 + + + 11 , 11 ] ] _ _ + + , , _ _ + + , , + 3 3 22 3 312u u ux x x 1 1 1 1 1 1 1_ _ 1+ 1 , , ]E One di'ensionalThree1"i'ensional, &here u is dis(lace'entLouisiana Tech UniversityRuston, LA 712727ur(ose o# the 8tress Tensor9or #luids11 12 1321 22 2331 32 333 1 1 2 11 2 1 3 13 2 1 2 21 2 2 3 23 3 1 21 3 2 31 0 00 1 00 0 11 12 21 122 21 12 2Pu u u u ux x x x xu u u u ux x x x xu u u ux x x x 11 11 + 11 11 ] ] _ _ + + , , _ _ + + , , _ _ + + , ,33ux 1 1 1 1 1 1 1 1 1 ]vy One di'ensionalThree1"i'ensional, &here u is velocityLouisiana Tech UniversityRuston, LA 71272Tensor :otation3 1 1 2 11 2 1 3 13 2 1 2 21 2 2 3 23 3 3 1 21 3 2 3 31 12 21 12 21 12 2u u u u ux x x x xu u u u ux x x x xu u u u ux x x x x 1 _ _ + + 1 , , 1 1 _ _ 1 + + 1 , , 1 _ _ 1+ + 1 , , ]/s called the rate o# strain tensor%/t can be &ritten 'ore si'(ly 3in tensor notation4 as12jiijj iuux x _ + ,and2ij ij ijP +Louisiana Tech UniversityRuston, LA 71272 A 8calar! -as 'agnitude only 3e%g% T;te'(erature4! Re(resented by a single nu'ber A 8calar 9ield! A scalar as #unction o# (osition 3e%g% T;T30,y,$44! Re(resented by a single nu'ber &hose value varies in s(ace% A