Boundary Lyer Theory

350 XIII. 1,mninnr honnclxry lnycrn in comprrrwihlo flow d. l%onnclsry lnycr with non-zero prrnwlro grndicnf. 35 1
It is wort,hy of notc that the system (13.61) subject to thc boundary conrlitions
(13.63) yirlcls t,wo pllysically sonsil)lc solutions wl~cn Jl < 0 (this is also lrue in the
cnsc of an atli:lbnt,io wnll. c/. Sca. IXn). Aceorcling to the vicws expressccl by C. B.
Cohen and 15. Itrshotlzo [lea], Lhc one ofthe two solutions which scls in in an expcriment
is clctnrnlinrtl by t.llc initsid ~ondit~ions which cstnblish t,he prcssrrrc field acting
1iig1trc.s l:%.l:~~l, c rvl~rwct~l, 1.11~
,Y, in lht: 11o111t~l:~r.y I:~,yc:r
ct~thlpy dis~d~~~~ior~,
it1
accorcJn.nc-o with cqn. (1:!.:!5) for '/I,, - 0.2 7',, nntl 7', 2 'I1,, rcspcc:t.ivcly. It is
socn tllnt, t,hc: prrssuro gr:l,clicvlt, nxnrl~ n consit1or:~l~ly stronger infIrlc:nna on the vr1ociI.y
prolilvs ~.II:I,II 011 lhc: (:t~l~I~:t.l~~y prolilvs.
Tlw figures c:orll,:ai~l I)lols of /"(71) for clifli:rrnt val~rc:s of tllo pnramcltrrs fl and
Whrn t,l~c cxt,c:rnn.l flow is nc:cclnrat.ecl (/I >O), thc lnrgest. shearing slrcss occurs at,
tho wall iLsdf (1, - - 0); wlwn the flow is tlccclern.t,ctl (P (O), t,his rnaxim~rm niovcf
away from the w:dl awl plnccs itself furlhcr from it ,as t,hc pressure rise is increased,
tllnl, is for 1:wgc:r nl)solutc v:~lucs of the: ncgntivc val~ro of Jl. lr~trotlrlcing the k ~al
skin-frirtion c:orffic:innt,
C, =-
b e,,, 16,
lG6. 13.14. l)ixlvilml,iw~ of dwnri~~g nl~rrw~:n i11 ~ I I I I -
prmsildo, I:tn~innr h~nclnry lnyorn wiLh prrnwrc
gradient and heat tmnsfer, after C. 1%. (hhen nntl
E. Rwhotko [IBa], and in conformity with eqns. (13.64)
I'rn~tcll.l n~~lnl~crr P -- I : ro -- 1
a: A', Y- 0; 'I*,,, 7 T,,; 1~1Ii1ilm1,io w~ll.
b: S,