bj' w. ball, m.,...beelaatton ~ ht -.r31" reeeuch work and. tben teat• have not...
TRANSCRIPT
·,
001fST11JalI0ll PDISHES ilD
HlGH-'Rl.OOl.n' J'LOW
BJ' Jaaes w. Ball, M., ,..}/
ABSTIACT
I
The need tor cla.e eomtl'U,Qtica tin1abn tor •urf'acea nbJected to
hi&h--ftlocit7 nav 1a pouted out and maeroua irngul.ar1tin cC1WOal;y
totmd in coutruct1on are 111..trated.. fl» oantaticm potelt'tiala ot
theH irnpl.antiu and. ~ •tboda of a1D1a1aizll thue po'tea
t1ala a.re diacuaftd .. Sc.Ille ot tile aurt'ace aUpeeat 11111.ta uaed in
pft.Nll't 4ar' oout:ruction a.re giTen.
tor now aurtaee• are too rig1d and, in aOlle cues., a.laoat mpou1ble to
meet. J'raa atrtctl1' the caaatnaetion poiat ot Tin, thia ....,.. appear to
be true. lbweYer I traa the operational point of TiW., cl.oae finish
lillite are ffrf ....rt.ial, vben tlow Telocit1e• are high. ID t'a4t
11&13¥ ot the 11a:1t• -ued 1n p....-t-411¥ coutructton -.v aot be strict.
eJ:IOl1gh tor ~ high ftl.oe1t1ea.11 The JurpoM ot th1a »aper ie
t.o a,lafn wbl' cloae tiDiah ltait• a.re neceu&J.7 llD4er blpftlocit7 now and. to auunt allowable liaita and treataenta O't tm irnplaritl• to
I]iGietor, V.Gii 5iida ~c I..e.baratortu, o. 1. artnen ud Aaaoe1ates, TwOUYU', a. c., Canada. l'omerl,1' Blad, struetve• and a..\'d.plat Sectioc, Jtl'dr&ulica Braach, D1Tia1cn ot ~ Labontari.N, Bve&u ot Beclaattoa., llenYer, Co.1.c>ndo.
J/~o Luantor., lepoJ't a,«-W ·~ ot SlloOth surta.cea on. now !o\mdar1ea butreaa traa OUtlet Works Control O&te•," Bveau ot Beolaaation, luJ.y 1958.
2
IA tbe ear)¥ 1950'• tbe :Bureau ot Beclalatioo adopted cfl"t&in
speo1t1cattoiu C1'1teria for coutruction tiniah l.Ja1ta.. ·Tbeae
cr1ter1& ha.Te befJll ch&IICecl alJ&htl.J' tr<ll t:lae to t1M 1n a ;proc.eaa
ot Mintamiag &d.eqtate can.t.rol ad couistenc.,. Balle ot tbe criteria
an baM4. on actual tat. 4at&, otbera a.re baaed. on put experience.
leNIU'Ch U :,l'eMA~ 'beine CODd\lCttld. to detend.De vbethel" or not
thne f1a1ab lillite aN too atrict a.lid. to delineate tbl co1tat1ca
po1;elat1al ot 'VaJ'ioua tnu and •1HI t4 1:n,rp.l.vit1• tor Tarloue
pressure and veloctt7 coad1t1ou. 1':>wfffl", uatU 1\d':f'icient l'dea!'Ch
bu bee pertoraed. to tuUy delineate tbe ttnuh liai ta needed ~or
cartt&t1oa-tne OJMfJ'&tico, it v1ll be .prud.ent to continue to a.ppq
the BurNu•• preNllt apecUte&t1GN•
The intent of atr1ct d1w1onal tirl1-1le• tor flow .-urhce• ia to
pi'ffflat in'egu.l.a:rtt1ff tb&t Y1ll tr1gpr Offitat1oa., which :tn tura,
viU 1ntl.1ct exteutve 4 ap to tu structure &Dd :re4Uiro coat]¥
N:1*1.J' ud u.1.Dtqanee. 'ro Nt&blhb ftUODable ud Ide fin1eh
lill1t• tor c,eciticattou J>VIO.IH, it 1• neceuary to lmov two
tu.ton: (1) tJPN ot trnp.l.ar1t.1u to be encountered 1D comtructed
flow nrlac• ad (2) tbe a1se ot each tne tJf 1n'ttplartty that ca
be tolerated. llucb 1• known U<Nt tbe tY»Q ot 1rrepl&n1.1ea to be
enoouat.eNd, but little u movn about tbetr critical s1SN.
3
OOIS'tlCUC'nOll-SU!FACE .IBll!llULUITl!S
fnic&l tJpaa ot ~t1ea 1Del\Ule &hl'QPt QftMt'ta into tbe t'low,
abrupt. ottNta aw,q tl'OII tbe tl.ov, &bJ:'Qt c\U"f'&tu:res ad. ,al.ope• &'IJ8V
trm tlstt tlov, w1u, ~ ~, and l)l'Otl"WliCIGS (f!a'm'e 1).
Ottaet• occur ~ ad ere ooe of the ltOlt trotliblea<11e o£ the
Mn.Y tnea ot ~ti•• ottaeta u:, lie at arr, angle VS.th the
tl.ow, but are~ either pt.l'&Uel or perpmlieul&r to it. 'the
:p«rpad1cvl&r, or~ iDto-the-t'low ottMt• are UA1Jl7 tlM
aoat obJectlGllll.ble (n&un U). o.ttMta ..,. trca the no,,, and
~ Jotata (~ 11 and lG) are alao ol)Jeet!Oltillbt... otfaet•
1D Jotnt• pvallel to the d.1recttan ot flow ve aot obJecttoaabl.e in
tbauelv•a, wt irl'eplaritiu u. ttie JoiJrt.a-, be tJ.'Q.l'blelQIIIJ.
IIW:'te.e .. tbat C'Uffe too ~ __,. f:t'Clll the flow (J'S.pre lC} il'liluce
low prnaurea that cauae CM1.tat1ca. ~iable obeDpa 1.11 llo»e or
&11p!lllftt a._,. .:rrca t!Mt tlov (ftpn lD), votu in tbe aurtaeea
(..., lrolff"), »,l&1a P'OOfta (JS.g,.tn 1.1), rrr nrtaee ~"•
(PJ&m-e lP) v.tll eau.ee Clffitat.1ca und.er c«rtaln comli. ttoo.. ..
&.T1tat1GD
A 4eftm.t1oa ot e&Yitatioa v1U Ulwrtrat.e • atr.rface ineplaritia
C11D be to ol)J.cttcaJ>J.e. J:riefl1', cott&ttcn couiate al ti. rwtioa,
.,,,a:ent, and.~ or ftlOl' C&Tlti• 1D a ft\d.d. 'J.lhe:·ftPCJI' C&Y1t1u,
or ~ .. tom ~ the pnnure 1A toe fluid 'becalell _, ~
JMllll't1Te (11\lb&~) tbat ~ :fODUJ (41114 'boU.). ftia occurs
1n •ter at eea lffel wben the ~aure 1"MObu ldJma 33 feet ot w.ter,
• pge and at el.en,tton 5000 at about mnua 27 teet or nter, pp.
!be ftPOJ' C&Y1t1ea tomed are C&ffied. bJ the fluid to ng1oaa ot
biper preum:.,e where ftJJO%' cu no 141pr ex:tat. Bach csn.ty ecmden1ea
and. t:114danly and 'liolea~ collapeea. AD4 at each point ot collaJe•,
wtaatueous pn9nre• ot aam,.y tl:louaDda ot poad8 »er •qlJU'e 1Dch
occur. 'fJaNa ft%7 bigb, loc&Used, and ni>idl¥ f'luetuatuc p:rwaures
an ex:tNM1J dntnwti:n to 111V' tlov h%'faoe ua pro4uce the tn1ca1
QCM"CY ~ woc1&W Yitb -.rttattce-eroetm.
The tomatica ~ 1ov pnaaun z.onee and the action ot cartta.ttcm an
illustrated in ftp.ft 2. The 11Tep.l.u'it1• tead to a.tleot ta stnta
traa the •urtace. Ah" cmmot enter the area urader tbe Jet Jwrt down
atnaa fZ'QII the in'epl.u1.'t7, an4 tlNa a low preuure acne llW8t tom to
cau.ae tlla fiat1 to l'Wf' 1D coa.taet vttb tlae aurtace. The b.S.gber the
flow ft1ocity, the aore tbe teaclency tor the J4't to le&Te the IIUl"tace
and. the l<*V tbe pregu.rea beccae. Wlwn the Teloolty u 8uch that
the preNure 1D a sane 1a e._.i to 'tbe 'Ylli>OI." pnaure, ftP)r cavtt1u
tom, cantat1aa 'be&'• (1ac1»1errt oa:n.tattoa), and a,......,. nn1.t.
oac. wa;,o:r preuure s.. l"Hehecl, the preu1l'l'e can ao no l.owier., and. an
~ :bl ftloclt,' *111' ~· tbe YaPOr SCDt1 increuu t.be n.te
ot 4 e• 1p., ad aovea tbe d•• tutller 4o'lfutna. Aa a nie, ti.
1Upr' ti. ~tJ' the ~ the ftloctt,' wUl be to PYO tuipieDt
oantatioll. '1'be al:ulpe ot u. 1rnpl.&r11.J' Y1ll alao 1Df'lueace tbe
ftl.oe1ty at whicb 1Dc1»1at aarttatico rill occur. ~ :lllwrtntu the
need tor aon atrtct nm.ah Uld:ta u flow velocltiu ~ azl4
•
' upl.a:lu vby' tin11h l1aite ahou1d. be varied trm. point to poiat oa a
atructure nch u a lup a»Ul_,. tuaDtl •
The Pftll8m"e Yithin the water at tbe U'ftll,llanty (1nd.uced by 4epth
or c~) a.uo attect1 tbe OM'11&\1cn potea.ti&l of the u-,.
....,iu1:t7. The Meha' the preanre at a g1nm 1rrapl&r1:t7, tbe
ld,pe:r t.lle ftloc1t.J' -.st be to n41lce tJM local :pNUm'e to 'f1i>OZ'
preeare. Thia aeeu that for tM .._ ftl.ocS:t,' a &lffll 1n'llpl.&ritf'
_,. be crltle&l. on oae ~un where tt 1a ahalJ.owi, nl:INrpcl, ad
not crit1c&l 011 another vbell it ta dN»J.7 aumerged or a a preaeure
COIMbd.t. Tbe :,robl.-. thwa raolve• itNlt tato ~ tbe
critical.~ and. 'Yelooit7 nlatiou bi»s tor each tne ad •1•
ot ll'ftCUl.U1.t7 • Thil u 41tt1cult to do 1n the laborator., becauae it
1a 111,pncticable 1a llllD.1 cue• to re,naat con41 ticu tJat are
enc~ 1a the ftel.4. ltlnffr, JII\V1h hu bee ay:ccaplUbed 1n
tb1• area tn neat ,.._ ..
CAnTAflOW POTll'.rW, 01 SUIFACI IUIGOLABr.rIBS
'?'lfo ,,......i. liJ'1HIII ot 1nepl.Uit1U "1U be 4UeU8N4,., (l) tJroM that
~ :l.ato tbe tlOlft.»C atftlllll aa4 (2) tboN ti.at NCe4e ...,- t:raa
tlle atnlll.
Prat!3!YM ~tie,
@11:!J o01'IMtftl4 ottectt. an ~tl1' found 1n ccr.uttructiall at Joilm
in the foiu or Jotata 1n the nrlaoe• (J'tp:re lA). Toiu 1D eon
ente nr.r.ce., tnunne ~, or PJ'Otl'UIUlll Joiata are 1n
6
.cae ~· •1•:Jlu to diNCt offset• {'1cm'N ll and J.a). Slmll
offset• uto tblt tl.ow ct .1~ aubJeet.a to h1&h ftlocitr tlow
ban hip can:tat1m potentiala. In &4dit.tm tJaer ur ?av• the
ualestnble t•t.ure ot tul>Jeetblg tbe .Jouta to a:tNllel¥ high
:IJlpl.ot ,~. ~ nudiee bD'e dtabl.1ahe4 tbe "1oc1tJ•
~ ftlaticuhi:, for ~1ent "'1.tatioD tor a.tttenmt •1Me
ot ...-..ellee4 ottHt• into t.be now (nave 3). With a ltaalm
wloeity Md • known ~' it 1a JO,Mible to ~ tl*
•1H o:I ott .. t tb&t can 1- tolAnted.
loaDd. co:rund. ottNi 1ato the now, ottaet corner vtth l'O\lllde4
edp, 1• ~ the aotJt CcalOtl tne encountered 1n the tield.
t>ecwe aoat COJ."M'N an, or becCM, 1'0llDded durillC coutruct10D
and o,er&tiCJlll. leN&l'Ch voa .. bean done OQ th1a tn,e ct ottaet
am tbe Nftlta are elM:Ml in 11.gure i.. TM eriticel •1n ot auch
a.ttaeta t~ ftrl.oua pl'eQ\11ie aD4 wlocitr cana.ttiou can be 4eter
•1Md frail ttd.a chart.
§lee o.Ufttlt 1J.\to the tl.<:N- are nr,t in thaNl'Vff troablqcae •
.._.,, tbit cblu:lp :la .iote or &1111 1at needed. w retun,. th.1a
t1Je ot 1nepl.M1:tJ' to the ~ = izlteo:led w.u alf.&i 11zt
u 1Xldica:td in l:lpna le, U, 20, u4 21>, -, be tl'OliblelloM ..
'lhta u temacl en 1l'Npl.u1.tr that N!Cec1N f1*0II tha tlov and 1a
ducuue4 1D. d.et&U 1n • la~ le<)tf.OII cd th1a JNll'ff •
!E'E!!d .. ~a:e- _,. be a calbinlllti.Cb ot ~ and reeecliilg
1:rNip1ar1t1N vh1ch 1"U7 1a ..,_ ... Nll .. •t• (~ a and a).
1
8J)ec1&1 ftNUCh baa bee conduct.d on pt,rtteular ~
~.JI '!'be C&Yitat1CG potat:lal ~ ~ ca the
mture ml cc.mt1pntian ot tbe ~•, Md. qee:1&1 twtina ta
U1l\ally ~ at each ,urtaee to dete%1111t,e the ccoditiou tb&t
will pro4uae cavitattQQ.
~~it.ief
!!HI or !IS'!£! ~ ott-,. U1Q' fl'Qll tbe tlov an alao
eDOOUDten4 fl'~ (11p:Ns 11 ad 21 ). Altbl:Nflb. Nl"lotla, tbia
tJJe: or ottMt probfabl.J' does not .... tu1te the ccn.tat1Q1 pot.ct1&1
U tbe otf'Nt illto the flow. llltt1oulty at tNtil:tC tb1a t,:pe ot
ott&et vu ~e4 with teat tacU1t:Lea 1ll tbe Junau ot
Beelaatton ~ ht -.r31" reeeuch work and. tbeN teat• have
not 'beel1 NNled.
Jbm4 comered attaeta lllillq trail t:be tlolJF are IIOt Ulll1lll1ILl. in cOQCrete
c~1aa. Tb& ~ .u t?d.a ce.,e _,. worsen conrlitiom rather
t bu up:at"• tlra, u it 4oelt in the cue ot otteeta tnto the tlov.
TM etteet ot aise ot tbl ottuta and the ........ ot l'Ot:DUDC are not
lmow.a am. aore reaevch ta needed. w utahlilib the caritct:lcn
8
Ott.-tt .~· f!S2! !!fl traa ;tbe, ~ are ~ OCCU1mM,3.l,¥
(11prea 10, D, 20, u4. a). !be nrtace NC«Unc traa the t1aw
1D tb1a 1ISD.ller .,., have a high CM'itatioa ;poteatl&l due w the abnwt
ehaDle 1n altpeeat of the surface~ Ursleu t.be ql.e u v-, -.U,
or 1s so larp that tile ll&Ul tlov tlet1Attel1' NJU'flte# fl"QI. the aurt&ce,
cmt&ttoa. 19 ~·· fJ.'lle en.ti~ -.ie wU1 d.epm'l4 on now ftl.oott;J', •t«r paeeap PIil*, abict preen;re and. wbetber or not
tbll tlml' u 111 an o,en cbl.nllel or a elo!l•d COll4ult.. The bt&twr the
ftl.oc1t7, t.lle -ller t.be 11.DCl• au.at be to~ cavit&t1ac ~·
Ti. correct1m of tat,o...ti,e,,.tl.oir offaeta by ~ ~ reaul•
a llo,ped.. ~ that ~ tbe Jl&1n 8urfaoea a abort cliatance
ttow.at.flllll. Die etteet O'I the tibUpt ot &lS~ at then inter
aecticlM ta •iailAl" to tt.t at ottaete alo»Da a._, tran. tJite nov. S\lttiQteat ~ .awst be ~ to -- thla Ulll-e -.u enough,
or to l'0\1Dd. tbe 3t:llet1ou ~ ~ to Na<ff'e tbe1r cavitation
~1&1.. '!'he chU't in ftaun ; iJldicatea the "1c,e or chtlnp in
&11jpMD.IC tbat CU be ~ for YU'i~ :91."t'U'Un and Tel.od.tJ'
o<Jllb1MtiQDII ..
!f!t!!• .9'!!'!1M !!R ~ the ~ oa.n be cou14erd a nnattou
ot the ._...:1.a,,,~ty:pe (r:tgm.,u lC and. 20). !'be carttat1a
~1&1. ot a ~ or 'balpt!. eurtace vutes nth aomt. of c~
u4 the ate of ~. letteeirch 1- bee dCDI to utabliah
9 ' cr1t1cal C\U:'ft.turea tO"I! flrioua ftloo1t7 at.Dd. presaul'e Cfllt/U.ti~J/§/
but further studf ta Mede4 to ~ pnenJ. eritela.
~ ,aurtac~ ..,- a:i.o tall :la the ncedJ.Jlg cateaor,. The
d.owrwtreea •idea at ...-.te ar hf.ab QOt• in the Rrt&eea W1U be
sources tor cnitatiot1 .. s,ec1&l teat. tor each aur.taoe 11ft DeefflG'J'
to eata'bltah tbtir cantatiO&'l potat1a1,.
mISB LDtl"fS AID OOl:RelYI UASODS
Oeceral Cau14er&tiou
'fbe nature ot the~• and. it• 1ocat1on ca tbe #tr"QCtUN rill
d.et&rmne what t"irde I.fa.it wt be *4MNd to, and if the ottaet u,
too great, vbat correct.in trelltaent aut be anlie4. Actual caritat1ou
d!1f1Da8e a,q l."NCh a stable ccma.ttiaa, or it uy .Pl'OfP.'N• to reach exta
stve ~1ou, ~ 6.. Dt cue• 11beN the ~ eunature 18
&W¥ traa tha tlw CM'it&t1cn aaece vUl, Yben the ounature 1• Juet
right (7'1&Un &A.), na.eh a point where Neh-oulatiou ocC\fl. Thia
raiM8 tbe pnasure &boYe tbe vapor ~e and cavitaticD. ceues.
lll cuea Wbere nrtace• ~ u,on the tlotfUII nnaa (~ 61),
tbe a&Titati<e wUl be ~•iff ecwsns e:uwb'e tr ••ae• tld'Oa"
taa~ aon cuea are ct a ps·oa;rwa.:lve nature. ·
!J'icTiil-.'t Eioiniii lo. '8, ~ 'fallflJ' Aut.boftt,'., 1953.
S/"~ic Model. StudiN of: Vaq,uero Z. Outl.et 'bu," 1'm'Nll ot 'lec1•11ttc:a ~" ll:rwh leport. lo. Jt49., ~ 1959.
L111:1on ..i Battle n..," Corla.<II IDCSDMN, a~. 8t&tim JB.ao., hfel' Jlb. i!-l3T J . .,... 195'•
10
When repa.tre beca11e nee~, 1t 19 ~ tKrt autticient to repair
Olll1' tbe area dlafl8K 'by' ca1.tatian because th1a does not N110Ve the
aouree or cauae ot the trouble. owtt&tlorl and. a .. se vill recur u
eOCll u ~t7 tl.an apin pua over t1Mt untouebecl ~ty.
Por ~ re,e.11", the aource, 1. •· , the tlow atD!'face 1r.Ngul.anty
wt be reaoYed. or rec1uce4 to~ mtical ~ an4 diDl!maiorw. The
cauae ot the d••P ~ be ne&?", or at a coui&mt.'ble 41.ataAce ~
t.raa tbe ero4ed. vea, ~ au tba tJpa and. ext«l.t at ta ~tJ'
and tbe natun ot the 1Ul'T011Dt11ng IUl'f&cea. ~ cert.a1n coaditiou,
iSmge due to a pa:rt,1a.1J¥ ~ 1&te val.Te bu bee known to occur at
$ d1at&Dce ot 20 »i»e 41IIMrten do'tmat:rea hall the 'ftl.1.ftJI
'!'re&1aerrt ot ~~1-t
tbm:Mi1DI tbe comers ot abrupt surt&ce 1ffegulalritea Y.W. uereue tbe1.r oarita't.1QD pc,tefttial. Bale idea u to the ettect1Ten•• ot the
rou•U.nc ot a&baTp cornen 1D.to the .tlow can be detemtne4 traa tbe
chart 1n l'1gQN ...
aurtaee reaulttna fraa the grtD41:ag U ~. SCM wrk done
in recent yean c:a gat• ~ bu been 'ON4 u a pide 1n
f!J5iiiullc .·~ ae»ort' Bo. 31' •am,, ot Gate 'f&l.TN U.d Globe &lTea u ftow lepl.ato:rw tor J':nip.tlcn m..tribUticG Sp'Mll8 Uader
BNda u» to about U,-het. ot w.ter," Im-el.a ol lecl•nt1oll, lflll.U&'t7 1956. lf•---.uo Cbancter:tetics or Ollte stow,'' b:r .raaea w. Bllll .. Journal of ~ J)J:rutoo., ASCB., October 1959.
u ~ crit.1cal 1.1.opN. ...,. Neat atMiee wbich ban yt.el.614
-U. cla'l't 1ll n__.. S vUl wt.at ta 4el11llllt:t1J'.II crltlcal lll,.oJe
c••••• tor~ ftl.aoitt.t a4 p:reuw.
!be~ of Breol•ritlaft .,_1ttca.t100. ,..,17 nip1ft that ol,Jeo
tlQQlbl.e ~ties be t:IIIIIOVe4 Oil a1('JJN ~ 20tl., ,Otl, err 10Ch1
Vba:r'e llib!at ~ are low uc1 tbe ftlocd:t.T N:t1J1t 1a ltO to 90 tNt
per .... 90 to 120 feet ,.. ---1 .. ~ tbaD. 120 feet ,..
..-, noeett'Nll'·
a,edftoat1.CM ftl\d.ft tJat ottana SDto or --, trca ta now be
lJaitecl to tJ.oall 1/8- to 1P,,-taob ~t- Ql'l 1fbether t.be ~
ta tama4 or UIU"ome4 ua vbltbff t1ae 1r.Nplartty ta ~ or
Plftl,Ua1. to the nov. ·TtMt b'ntpl&r.lttee or o.tt.-. are a1wp t..reated
"' ~ vbea. tbQ' ..,..,. t.balle lild.ta. Wbell ~ 1rNp.1.arl- 1a
dolutNilll ft'all - ollt1et W011la p.te tbe ~· s. NIIOrtl4
~ m ti. llOpl q,eott144 to, ti. 'Nl.olt't;J'. ta otbW cu•
vblft tbeN ta ~:ty t• ,, llldu)'" i.,... ~ 1a tbe :nav. tb&t l,IIU't of tbt oft'Nt 1D .... Oil ti.bl lJa:1:ta ii naon4 m tbe
lllfNU'ucl aloJpe. All lrnpluttu. 111 Wl'tlNl 1'4:ael N1.1U nl,Jwc«t.
to ld.p ftlocd.t ... aft I 1B!WM ~ Oil thtl lfldftt4 ~
"'ll,l'll1eN ot tlJltU' ori.elrt&U.Olll 1d.'tb. 'tM tloW.
Jo,,._., i..,. bu a~ 'bNnq OD. ti. tf.aUh Uat:tt1 allc,a4.
~ rtlllM:Wal of ~ti. an ~ elo.PN b ~
... tbe: lt.<NI,-, l,llfW of '"'8 l'l.Aw' lu beta ~ or dU't.WNd
12
.. ~ f'ral. ptea ~ outlArt llOl"U- Wh«r• the bolmdal'y lapr
u ~ 4eftlaped, nch u 111 a -,m ... ebNmol, tlle apeeifi«\
fin:l.llh ll111ta are ,..S.twd and oa.11' the uce.. ottaet 1a J'lll'IIOfK oa
the spec1t1e4 aJ.a,ee. Reviaiou to thue apectn..ticma 11"7 be
dQ:lnbl.e and VU1 be Md.e u mceu&:l7 &ftai' & tboroagb .t'Qt\v' rA
nceat aDd f'uture reaeareh oa the 11a1q tn- ot hfffpal..arlts.e..
muxm,m VJD ~ • SURP.AC& llRJDJLABlTu:s
A c,_.. in. &l.:f.-,ent wba-e the ~e reofl4c4 f'rca the t1ov cauaed.
conaidenble c1..,..ge doVutrea hall ot1e or tbe pt• at P&UMdea n. (ftprea T wt 8). ~ alQJe cbanp ooeurN4 at a COftlli!'r iw:Uatel.¥
doltUtreea traa the pte t'.Nlle VbeN a concrete till.et a'boat 10 1nche8
laag al.Ol*l outw.rd hal the cur,e at tbe metal to tbe ehar,p comer ta.
the COllcrete. !he eroded area waa Ml'tenl feet lcmC, ahout 2 :t..i vld.e
and had • -.xsma depth of 7 !neba. 'l"he ~t7 vu ot the type
uown m J'j,gure ll).. lllr.;ai1" wu 1l&4e in such a wcr that the :rate ~
al.ape cllMp vu eutfteieatl¥ padull. to pre'fmt PNffUlff ~ '91ll)OI"
~-.. 1tllll.e.
~ ~ts.a which 1tduce CM'itatioa are ~
..,_t&ft494 1ato tlov n:r:rac.1. fld.a occurrence 1a now rue beC&UN at
tlw 'VUt. mowlAdp p.1M4 fl'al1 reMlll"cll :f.11 :tec4ll'lt ,-.an. AD «r81111e
ot an ~ty •1Ped mto a lhlrf'ace •aae 22 1'*Z'8 aao 1•
f'O\a'J4 1a tba utt cone am troQfltl 1A tb;.e v;p,pe!' eZl4 iDtemellSate tien
rd outlet.a at Orud. Coulee DIii (ftaqre 9). AD~ chiutp in 11.\tp
aent ~ tbe ~. at the me ~ about 1 1n 16, OCC"Un vbeN the
.•
13
eur.tace ot the coutat-w.ldt!l «dt trcach cant~ be;Joat1. tlw cooe ..
'.rbia. toma an trnrp1.u1:tJ' asauar to tbat ~ 1n J'1pre lJ).
frol:Natw ca,1.tat1r,o,.croe1on ftlalllted tr<111 tht. ~v vhiln
ti. OlltlAte were o,eft.t-4 for flood coatzo1 ~- (~ 10 ),.
1'he 11•rp 'ftl1.e4 'ldAal1' for tbe Ito outlet• cbMt to TU'ioue ltmlt'u ot
~at.tng ,-s.ou, dittenacee 1D. hM4, loc&1. bUllea 11.1. ocr.lCffte·
~ .. ~ iato all4 ....,. tJ:ca tat flow,. .a. ftl':t.oua roa,.,_..._ 1a the C<llllOS'et,e.. :npn u eon the ...-.i ,attc,,. ~ ~-.
uoaiOll ~· the cone IA oae ol tbl eoDd.ldta. !be con41t1ca. wa
~ bl' ~ the C:Ollduit .i the ead ot tbe coae wt ~
the CM'i.tat.t.on-tne .. t.e al.ot 'JflMIIJ.t,J•.J/
A aeotS.Oll ~ a "VOid or..._ bole• u aia!lu to that or a trw
verae poaye (l'ipft 11)11 Itl tMa t1J8 Olt ~v, tlle low Jl"elllJUN
zme fODLe JMt downstNtlll ma tu dowDlrtNlllll comer (ftgure 21). n.age
'to' ea1.tat:1.on bu beecl ob#e:ned dolfmrtNlll ma 'bua balee ot abcNt l/amcb ~ &ad ~ (:r.t.a=e 12). 0n tJ:aU buu 1t a be11eYed
t.bl.t btC balea u4 ¥GU. ahoal.d be tille4 to tom aootb coa.tt».uou
~ wtaer& t1ow ftl..octtt. ao,14 about ,:, t.et ,-. MCQDd.. '!lie
bole U'Jtb IID4 'fll4Q, ad thlt flow ffloct:Q" 1dU 1rd'l.uieDce ti. e&Yit.
tim ,otas.tS&l. ot MlCb ~t!N. fo Mt4, there hue 'NG in
aut.riciaGt ol>NS'tat1.aml to ..t:abliah., 4d1ntte ~.
" ~ .. reaultt-s traa an~ offaet into the ftov 1D. the coac.rete
1Rlll dolmatl"ellll tlUI, an outlet gate where tbe preuure tn the •ter at
the ~t.7 wu DIU"l1' ~c, ta NOVn m 11pre 13. !he
velod:ty ot the •tu wa about 100 terit i*' Mccat ana. the ottut vu
abou:t l/8-lMh. 'l't» chart ot r:tpre 3 dON not exteD4 ~ vel.ooitiee
ot 8o teet. per eeoant1, but ~ 4et.l.n1te.1¥ dOW9 that can:'8.tian
woul.d occur and that the 4ra IP abaal.4 be -,.et4t4. !Ida ottMt, vbich
lliP,-recl ll1*>r to the ~lon foroe1t, wa uacwed. and. no turt.l.liu'
carttatim-. beC1 onel"N4.
~
-., d1tteNGt tnea or wrtace 1rreplc1.ttu rill 1nduee cavtt&tim
1t e:,;aoeed. to bilb ftl.ooS.tJ" non. Oft'•eta at Jo~, ab;rtrft cbllo&N at a:uc,mnt, '¥Ola., eurtace ro,.,...,, &D4. 'bulpa are C<alOll ~ti• lilael.J to in4w!e daag.tag c&Titation.
flM cs,1tat1Gll ,otat1&1. ot the vartoue 1nepl.&r.tt:1ea 41tten v1del1',
~ on the •t• aa4 shape td the ~• and the preuure
end. T8locit7 1n the tlov.
Ccntl"o.l of ~ ~tlee -.wt 'be 1'1814 wblln aur.taeea are to
au.at.a1n hip Te1tJoity flon. acne nlu:ation ot .Jl'•••at lJmu ot u-
np.\u'tttea _,. 'beoale JON1ble after aore totOZM.t1on ~ &T&Sl&ble
t1lrouf;h NMUCh end. tbroulb field ear;erience.
arteuin ftel.4 ml l..abolw.tory at'Udiels are needed. 'to better eatN>l 1 eh
the g'Nlltut V1U'iations wtd.ch CC1 'be Mt~ pemitted. tor 'VU'iou
"Nloe1tf' -1 ;fl'NtNre coaditlane.
.. ,,
FLOW>
. . . . . . . . . . . . . . . . .. ~~~~~··· ······· ...... . ... ·.·.::::·.·.·.·.·.· .. ·.· ::·.:· .. ·.· ::-::·.·.·: .. . . . . . . . . . . . . . . . . . ...... . ·,,·.
A. OFFSET INTO FLOW
-> . . . . . . . . . . . . . . . . .. ·.·.·.·.·:::·:::::·.:·=·.·:···.·.··· .. ·. ·.· .·:.:. :·:: : .. ·:··· .. -:··:·:·.·.·.· . . .... . ·:. . . .... ~
C. ABRUPT CURVATURE AWAY FROM FLOW
-->
E. VOID OR TRANSVERSE GROOVE
--:>-
->
. . . . . . . . .. . .... ···········.·······~---·: ·.·.·.·.·.·.·.·.·.·.·: :·-·.··::.·.·::·.·:· . . . .· .· . . . . . . . . . . . . . . . . . . . . . ... 8. OFFSET AWAY FROM FLOW
->
D. ABRUPT SLOPE AWAY FROM FLOW
->
F. ROUGHENED SURFACE
G. PROTRUDING JOINT
FIGURE I. POSSIBLE CONSTRUCTION IRREGULARITIES ON FLOW SURFACES
FLOW --> ,.- Vapor cavities
__,....~·.: · ......... ·: -: ·.: :·: ····: .· .. . .-:.:·::. =-;":":\ r:-.: ·: · ·. oa m age ·-1 · · ·
A. OFFSET INTO FLOW
-> rVopor cavities ~
C. ABRUPT CURVATURE AWAY FROM FLOW
--> , Vapor cavities I
::? W-.&r ... .-.:; . ': \t ...... ;::-: ; ·: .. : ~ · .. : : <, ..... : .. :, • • • • •• • • • • •' I · ·.· ·· · ·. ·: Damage ....
E. VOID OR TRANSVERSE GROOVE
->
--> ,, Vapor cavities r '
• • • . : . . . . . c... c:::_ .> -:s -..... ,..I_--...::::: ': ... ·:·> ····=~·':.' .!.·::~::,·.:. . . . . . . . . . . .. . . . . . . ... . . '.. . . . . . : . . .. 'i". ·:; : · .. :.·: .·. ;
Damage-.,/
B. OFFSET AWAY FROM FLOW
--> , Vapor cavities I
D. ABRUPT SLOPE AWAY FROM FLOW
--> ,Vapor cavities , I
I
F. ROUGHENED SURFACE
,, Vapor cavities
.. ·:.·. :::--..~-s) ), --... ~-\-~ :,.....~? /·.: ?:'-: :·::: :': :~;f.-: -~·· .. • .. · _P._ ·: .~-... ~-: -:~: ·::'7:: ·. ·,:·: · .. : ·: ·:, ·."::'oamcig'e' ·.
G. PROTRUDING JOINT
FIGURE 2. POSSIBLE OCCURRENCE ,OF CAVITATION AT FLOW SURFACE
I RR EG U LAR ITIES
(JI 0 100 d\
w 1- 90 => ...J 0 (/) 80 m cl
a:: w 70 I-cl 3: LL
60 0
I-UJ 50 UJ LL
: J: 40 = 0 cl w J:
w a:: => 20 (/) (/)
w a:: 10 ll.
0 0
I :I: I
V ---:>-
Off set -.1---w/7777777777 7777777777))/77 /
I
Vapor pressure -
10 20 30 40 50 60 AVERAGE VELOCITY
11V
11 AT OFFSET
\
70
FIGURE 3. CRITICAL PRESSURES AND VELOCITIES
FOR SQUARE-EDGED OFFSET INTO FLOW
80
~ 90 t----t--_...______.....____.....____....._____. _ ____._--+----+---+--,.+-+------h,....._,..-+-
::> ..J 0 en 80 -m <(
a:: 70 -LIJ
~ 3 ~ 60 0
I I V
=f pr
Rounded _ 1 ·y corner----- ::r: R=rodius -~=rise
I
example: 3~ r x 1/8
R
~ LIJ~t---1---1-------1~-----1------1-~-~-~-LIJ ~
I I ,t
\ (+ \ ''" ----------- \ ---,,..~
----------......+--~~ ""-+--+--~
=x 40 t----1---1-----11-----1-----i----+-___,._---Jf~--+~~-,..--+---+---+---+---t :s 0 <(
~ 30 t---t---t----1f------i-----i--,i~~,-_----f:.,;c....~~--+--+---+---+--+---t
LI.I a:: ::> 20 t---t-----'-~----i~----i-.....,,,..~c,,,,,c+----:~~~---+---+--+---+---+--+---t Cl) Cl) LI.I a:: ~IOt----1---1---~~.--__...-.--+----+----+---+---+---+---+---+---+----t
o ~:::::::r::::::.._L_JL_Jl....__J _ __J _ __J _ _j _ _j _ _l _ _l _ _.L _ _.L_-1.. _ _J
0 10 20 30 40 50 60 AVE RAGE VELOC ITV 11 V .. AT ROUND ED CORNERS
FIGURE 4. AVERAGE VELOCITY RELATIONSHIP FOR INCIPIENT CAVITATION - ROUNDED CORNERS
70
100
t.&J 90 I--::> ..J
~ 80 m c:s:
A I I I
:I: I
V ---:>-
I '
.l ,------==---Che mfer ... ~J I 1----1t-1-~-+--+---+-+--+---+-~r+---~L--4---.~---.~
X ffiro~~-~-~-~-~-~~~-~~1--~-~-~~~~~~~~~~
~ 3 60 t-------+---+----+-----+--IL. 0 I--
I.LI 50 ------------.----------"--~-----LLI IL.
;x 40 1---t---+---+----+---+--+1--+-~+---J----------l1--#--+-~
C c:s: I.LI :I: 30 r----t---t------t---+---1-1--~-~-+----:.~~~..,._---7'-:.....__---+-:..,c--+--
LLI a: ~ 20 r----t---t------t---+--H-~-~-~~~~~~~~--:;J.,,,,IIIE:--+----+-----==-llfllE=-~~ C/) I.LI a: ~ IOr----t---t------t-~~~~~~~-r.--s.,,~---=-~~-----:=----=-+---+----+--+--~~
0 10 20 30 40 50 60 70 8 0 90 100 110 120 130 140 150 AVERAGE VELOCIT1
11V
11 AT C~AMFERS
FIGURE 5. AVERAGE VELOCITY RELATIONSHIP FOR INCi PIENT CAVITATION - INTO THE FLOW CHAMFERS
,,,.- Water surface
FLOW>
. A. CURVATURE AWAY FROM THE FLOW .
... -Water surface
B. CURVATURE INTO THE FLOW
FIGURE 6. CAVITATION ON CURVED SURFACES
)
P4!56-D-20711
!
'>
FIGURE 9. FLOW SURFACE IRREGULARITY GRAND COULEE DAM OUTLETS
