Boundary Lyer Theory

invc?st.igai.ctl. In this msc too, sltl~st~:~.nti:rl rcc1uc:tiorm in tlrn,g were achicvccl, allowing
for lhc mnclrnriic::t,l work roqrtirctl to maintain it.
W11(?tt an n.t.t,cmpt is matlc t,o prcscrve a laminar I~olinclary laycr citllcr by
suction, or, as already rncnt,ionctl, merely by proper slln.ping, it is vcry important,
t,o have a gootl Irnowlctlgc of bllc potcntti:d velocitcy clistrib~~tion. In cither case it
is ncccssn.r.y tt.o arrangc for t,Ilc prcssltrr 1.0 t1c:crcnsc ovcr as Iargr. a portmion of the
section as possible. Very oxt.cllsivc cxpcrimcrrts on this sul)ject were carried out,
by S. C;loltlst,cin 1311 n.ntl Iiis coll:tl)or:tl,ors. 'I%(: cnlc:ulxtions lccl to the tlct.crnlinat,ion
of the* sl~n.pc of I.llc? scc:l,ion of t,lto :~.c:rofoil which wo~~lcl procltlcc: n ~)rcsc:rilml pot.cnl.inl
vvloc.it.y clislril,ttl.io~~. III ortlvr to ol)t.:r.itl :tc~roli)ils which nlnintnitl n. Inminar 1)ountl:l.ry
l:~.yc:r :IS hr :IS lilt- tr:lilillg c~ljy: it. W:I.S s~tgg(~st.ecI 1.0 ltsn slinpcs sliowing a
dcerc;:lsc: ill prcwttrc: (:it1 itlcw:lsc: in vchc-il.,y) ovvr l.11~ wholo Iotiglh, n.nd otrly
(lisl)l:~.yi~~g :IWI :I.IwII~~, prwsltrc in(wxsc :~t, on(: posiI,ion, n.s sl~own in Vig. 14.20.
If t.Iw slils arc nrr:~.t~grtl nt. 1.11~ ~)oint~ of prcssltro jump, n.s snggcst,ctl by (:riflil,li 1731,
it is possible t,o secure a laminar bonndn.ry Iaycr otl thick nerofids as far as the
lit and separat,ion is prevcntctl 1)chirid it. B. Itcgcnscllcit 171, 721, and B. 'l'l~wait.os
[Mj proposcd Lo 'regulate' tho lift on vrry t,lliclc norofoils by varying the
intcnsit,y of sl~ctdon ant1 so to obtain a lift which is intlcpcntfcnt of the angle of
incitlrncc. In morc recent times there were many proposals to use tho air srtclretl
aurn.y from the bountlnry laycr for the purpose of irlcreasirtg the thrust of :t jat
a.ircraft [87].
'1'11~ papers 1j.y F.X. Wortmnnn [I051 and W. I'frnningrr 102, (31 rrport, on more
rc~c-nt~ r~s~tlt,~ (:onc:orning tlic design of latninar acrofoils and of the tlcl:ty of t,r:tnsit.io11
o~t xwc:pt-l):tcrlc wings.
,, I ho ~WO~:CSS 01' t.rn.risition frorn hninnr to trrrl)~~l~:i~l~ Ilow in tho Im~~rcli~ry
layer witl~ s~i(:t.ion will 1)r. stltdicd in (lrt.:til in Sc:n. XVl l c:.
1. Theore~ical results.
U
.-
urn
c. Injcctinn of a diflcrent gns (Ihnry boendnry layers)
1.1. The fundamental equations. Whrn R sp,zco-vn11ic:lo robr~r~~s to the tlcnaor layers of the
nt~nospl~rro, t.lw ~l,zjinnt.ion cfTccct whir11 is protl~~ortl nt t.l~c? t~ose or in 1,110 I ~ o I I I I ~ Inycrs : ~ ~ ~ along
1,110 wdls givc8 risc l,o vcry high t.c!t~~l~er~il,~~rt*.q.
111 ortlvr Lo rcx111w 1.11~ q~~:inLit,y of 11c1at Lr:u~sfwwd
to tile vchicle to s~~tell proportions, it is possil~lc t,o i~~jcct, n light. g:ts or a fluid tl~ror~glr a porous
well. l'hc light gns or thr v:rponrizing fluid thus rrcnls n thin filw nlong tho wdls. A si~nil~r ctl'rct
ran :also IN: procl~~nc~l il 1.1~: rnn1nri:al of t.lw will (r.g. grnphitn. gl:wn, or n ~ynthct.ic ~l~:al~.rinl)
i~ nllowctl Co sublit~wtc thtm rrdl~cing it8 tl~ick~lcss (n.blat.ion). III :dl S I I ~ onnrs, I I~o~rnd:iry Inycrs arc
for~ncd in which two or morc gases mix with one anot.lrcr by din'~minr~.