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Boundary Lyer Theory

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Turbulent flow through pipee<br />

n. Experirnentnl results for smootli pipes<br />

\\'111*n :i Ilttitl is :11Io\vrtl to cnlcr :L circ111:w pip front a largc ronl,:~inrr, tltc<br />

vc~loc~i(,y tlis(,ril,r~( io11 in t.11~ rross-sections of tho idrt lan~~th vnrios with thc tlisCnncc<br />

from the: itliti:il cross-swI.ion. In sections (:IOSC to that at cntrancc the velocity<br />

tlisl.ril)~lt.ion is nearly uniform. Il'11rt1wr t1ownstrt:am tlhc vclocity tlistribr~t,ion<br />

cltnttgrs, owing 1.0 t,Itt: ir~ll~tr~tcc: of frict,ion, rrnI.il :I f~llly tlcvclopctl velocity profile<br />

is :~l,l.:~inc:tl :rt, :L given cross-scc:l.ion :LII(~ rcmains constm~t~ downstream of it,. Tllc<br />

vn.ri:ll~ion of t11t: vr1orit.y profile in the inlet length of a pipe in lam.innr flow was<br />

tlcwrilrctl in Scc:. XI11 (l'ig. 11.8). 11,s length is approximatdy 1, = 0.03 rl . R<br />

so I Il:tI, for R := 5,000 l,o 10,000 it, rangcs front 160 t,o 300 pipe-din~net~crs. 'rhc inletf<br />

Irng1.h in /?o.b~drt~l flow is consitlrmltly sllort.cr t,h:rn in lan~inar flow. According<br />

1.0 1.11~ IIIC:I.SI~~~III~-II~.S p(vforn1~t1 by I[. I

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