Boundary Lyer Theory

CIIAPTER XIV
Boundary-layer control in laminar flow t
a. Mntliod~ of boundnry-layer control
,.
l iicrc art. in existence several ineLliods which have been devcloped for the
purpose of nrt.iGcinlly conbrolling the Imliaviour of the bonntlary layer. The: piirposc
of fhcsc mctliods is to affect the wliolc flow in a clcsircd dircction by infl~rcricing
the strtrctmrc of the boundary layer. As early as in his first paper published in 1904,
1,. I'rantltl rlrscril~cd sevrrnl cxperirnents in which tlie borl~ldary layer was cont,rolled.
Ire: inl,cndctl to prove t h validity of his funtfamonta.l ideas by suitahly designed
ex~)crilncnt,s n.nd arliicvctl quite: rcmarltn.l)lc rcsr~lts in this WRY. Fiprc 14.1 shows the
flow p;mt n c:ircr~l:\r c:ylititlor witli s~ict,ion :~pplit:d on one sitlc of it t,hrotrgh a srnall
slit.. 011 t.hc s~~ct,ion sitlo tho llow ndhnrrs t.o I.lic cylintlcr over a consitlcrably larger
~,ort.ion of its srirf;lce: nntl scpnr:rt.ion is nvoitlctl; 1.11~ tlrng is rcduoctl npprcci:~ldy,
anti si~nnlt~niiconsly n Inrgc cross-force: is intlt~cctl owing to the lack of syrnnictry
in the flow pnt,tcrii.
1 I'roft~swr I),.. \IT. \VIWS(, t~sxixl~~l ill l,lw lm~1x1r:tI.itm
b'illll IC11ilio11 of I h i ~ lmk
of t,Ilt: ~ ~tw vorsitm of lhi8 rIlnplt*r for l h
in nct,r~al npplio:~tioris it is oftcri norcssary to prevcrit scp:~ml.io~i in ortlor to rc-clnc:t:
tlr:ig ant1 t.o athin high lift. Several niethods of cont,rolling the botrntlnry lnyor
I~nvc \)con clcvclol~cc~ expcriniontnlly, nnrl nlso on the h ~ix of I,lioorotic::~l norrsidc:rntioiis
16, 76, 701. Tlicsc can t~c t:lnssifictl as follows:
hlot.ion of tlie solitl wall
Accclcrat,ion of the boundary hycr (blowing)
Suct.ion
1njac:l.iori of :I. cliffcrerit gas (biriiwy Imnndary Inyc:r~)
I'rovt:nt.ior~ or t,rnnsit,iori to L~~rlmlonl flow I)y t11t: provi.siori of utliL:~I~It!
(I:i.minnr :~t~ohiIs)
('ooli~ig or Llio wrdl.
NII:L~;(:H
Mrthotls 1 to 4 will be discussetl in (.his chnptrr. Methods 5 antl fi will be
tlcscri1)rtl in (:II:L~. SVII in conriexion with tho rorisitlrration of I.lw t.liwry of
t rnnsil ion from I:ui~in;w to ti~rl)tiIriit~ flow.
r
I . lio t.rcat.isc: e~it.it,lt:cI "Bo11ncl:wy-1,i~ycr antl I'low (hl.rol" 1441 Ily (:. V. I,;L~:IImann
~ont.:~ins a summary of the sirl~jcct of boi1nd;~ry-layer control accorcti~ip to
the state of rcscnrcli at t.lic time; compare also I.'. I