cfd for nuclear systems - lecture 16
TRANSCRIPT
LWRi
i
161
45L
EC
TU
RE
16
CFD
for
Nuc
lear
Sys
tem
s
Chr
isto
pher
Boy
dO
ffic
e of
Nuc
lear
Reg
ulat
ory
Res
earc
hl
li
iN
ucle
ar R
egul
ator
y C
omm
issi
on
LWRi
i
162
45W
hat i
s CFD
?
•C
ompu
tatio
nal F
luid
Dyn
amic
s (C
FD)
–a
“num
eric
al si
mul
atio
n” o
f flu
id fl
ow a
nd h
eat t
rans
fer
–“c
olor
ful f
luid
dyna
mic
s”
•C
FDis
com
mon
lyas
soci
ated
with
anu
mer
ical
solu
tion
of•
CFD
is c
omm
only
ass
ocia
ted
with
a n
umer
ical
solu
tion
of
the
sing
le-p
hase
Rey
nold
s-A
vera
ged
Nav
ier-
Stok
es (R
AN
S)
equa
tions
.–
CFD
is a
lso
appl
ied
loos
ely
to a
var
iety
of o
ther
rel
ated
met
hods
.–
The
term
num
eric
al si
mul
atio
n of
flui
d flo
w c
over
s a w
ider
ran
ge
of a
pplie
d m
athe
mat
ical
topi
cs.
•O
ur fo
cus w
ill b
e on
the
com
mon
tech
niqu
es a
pplie
d to
N
ucle
ar S
yste
ms.
y
LWRi
i
163
45W
hat
does
CFD
pro
vide
?
•CF
D p
rovi
des
velo
city
, pr
essu
re,
and
tt
hit
ii
thdi
ite
mpe
ratu
re h
isto
ries
in t
hree
dim
ensi
ons.
•vel
ocit
y
•tem
pera
ture
•Pre
ssur
ized
The
rmal
Sho
ck S
imul
atio
n
LWRi
i
164
45Co
mm
on T
erm
s
•D
NS
dire
ct n
umer
ical
sim
ulat
ion
of t
he
Nav
ier-
Stok
es e
quat
ions
q•
LES
num
eric
al s
imul
atio
n w
here
the
lar
ger
eddi
esar
edi
rect
lysi
mul
ated
and
the
eddi
es a
re d
irec
tly
sim
ulat
ed a
nd t
he
smal
ler
scal
e tu
rbul
ence
is m
odel
ed•
RAN
Snu
mer
ical
solu
tion
ofth
eRe
ynol
ds•
RAN
Snu
mer
ical
sol
utio
n of
the
Rey
nold
s Av
erag
ed N
avie
r-St
okes
equ
atio
nsl
fd
tCF
D-
com
mon
ly r
efer
red
to a
s CF
D
•CM
FDCo
mpu
tati
onal
Mul
tiph
ase
Flui
d D
iD
ynam
ics
–RA
NS,
LES
, an
d D
NS
vari
atio
ns e
xist
LWRi
i
165
45Tu
rbul
ence
–M
ost
flow
s in
nat
ure
and
engi
neer
ing
are
turb
ulen
t.–
A pr
ecis
e de
fini
tion
of
Turb
ulen
ce is
dif
ficu
lt.
–Ch
arac
teri
stic
s (r
ef:
Tenn
ekes
and
Lum
ley,
A F
irst
Cou
rse
in T
urbu
lenc
e)(
y,)
•ir
regu
lari
ty (
chao
tic
or r
ando
m)
•di
ffus
ivit
y•
larg
e Re
ynol
ds n
umbe
rs•
thre
e-di
men
sion
al v
orti
city
fluc
tuat
ions
•di
ssip
atio
n•
cont
iuum
not
afe
atur
eof
flui
dsbu
tof
“flu
idfl
ows”
•no
t a
feat
ure
of f
luid
s bu
t of
“fl
uid
flow
s”
–“t
urbu
lenc
e pr
ovid
es m
any
of t
he m
ost
chal
leng
ing
prob
lem
sin
flui
dm
echa
nics
”ch
alle
ngin
g pr
oble
ms
in f
luid
mec
hani
cs•
(ref
: A.
J. R
eyno
lds,
Tur
bule
nt F
low
s in
Eng
inee
ring
)
LWRi
i
166
45Tu
rbul
ent
Obs
erva
tion
s
•lig
ht s
heet
imag
e of
tur
bule
nt b
ound
ary
laye
r
•tim
e hi
stor
y of
vel
ocit
ies
in d
owns
trea
m a
nd la
tera
l dir
ecti
on
LWRi
i
167
45Tu
rbul
ent
Stru
ctur
es •vor
tici
tyco
ntou
rs o
n
a fl
at p
late
com
pute
d
by D
NS
•ref
: Pa
rviz
Moi
n,
cent
erfo
rtu
rbul
ence
cent
er f
or t
urbu
lenc
e
rese
arch
.•w
ww
.sta
nfor
d.ed
u/gr
oup/
ctr
LWRi
i
168
45Tu
rbul
ence
, W
hy d
o w
e ca
re?
•Tu
rbul
ence
impa
cts
heat
tra
nsfe
r, p
ress
ure
drop
s,
and
mix
ing.
The
se b
asic
issu
es a
re a
t th
e he
art
of
man
y sa
fety
pro
blem
s.•
Cons
ider
flo
w o
ver
a he
ated
wal
l.
Lam
inar
flo
w
Hea
t is
con
duct
edf
thll
Turb
ulen
t fl
ow
Hea
t is
con
vect
edaw
ayf
thll
thh
away
from
the
wal
lth
roug
h la
yers
.fr
om t
he w
all t
hrou
gh
turb
ulen
t fl
uctu
atio
ns.
LWRi
i
169
45H
ow d
o w
e de
al w
ith
Turb
ulen
ce?
•D
irec
t N
umer
ical
Sim
ulat
ion
–Pr
ovid
esa
tim
eac
cura
teso
luti
onfo
ral
lsca
les
Prov
ides
a t
ime
accu
rate
sol
utio
n fo
r al
l sca
les
of t
urbu
lenc
e.
•Fi
rst
prin
cipl
es a
ppro
ach.
Cl
li
il!
!•
Com
plet
ely
impr
acti
cal!
!
Reyn
olds
Aver
aged
Nav
ier
Stok
es(R
ANS)
•Re
ynol
ds-A
vera
ged
Nav
ier-
Stok
es (
RAN
S)–
106
–10
8re
duct
ion
in c
ompu
ting
req
uire
men
ts
com
pare
dto
DN
Spo
ssib
lefo
rin
dust
rial
scal
epr
oble
ms
com
pare
d to
DN
S po
ssib
le f
or in
dust
rial
sca
le p
robl
ems.
–Av
erag
ing
away
the
tur
bule
nce
resu
lts
in t
he n
eed
for
a tu
rbul
ence
mod
el t
o ac
coun
t fo
r im
pact
of
Turb
ulen
ce.
–Th
ere
is n
o ge
nera
l app
roac
h fo
r th
e so
luti
on
(mod
elin
g) o
f tu
rbul
ence
.
LWRi
i
1610 45
Reyn
olds
Ave
ragi
ng •The
ave
rage
of
the
prod
uct
of t
wo
term
s
resu
lts
in t
he p
rodu
ct o
f
tht
gt
the
two
aver
age
term
s
plus
the
ave
rage
of
the
prod
uct
of t
he
p fluc
tuat
ions
(≠
0).
LWRi
i
1611 45
The
Turb
ulen
ce C
losu
re P
robl
em
•N
avie
r-St
okes
mom
entu
m e
quat
ion
•RA
NS
mom
entu
m e
quat
ion
•Th
eRe
ynol
dsst
ress
esad
dun
know
nsw
ith
no•
The
Reyn
olds
str
esse
s ad
d un
know
ns w
ith
no
furt
her
phys
ical
law
s av
aila
ble
to “
clos
e”
the
equa
tion
sth
e eq
uati
ons.
LWRi
i
1612 45
DN
S vs
RAN
S
•Ef
fect
s of
Tur
bule
nce
are
mod
eled
in R
ANS
•Co
nsid
era
heat
edpi
pew
all
•Co
nsid
er a
hea
ted
pipe
wal
l.
DN
Sor
Phys
ical
Flow
sRA
NS
Mod
elD
NS
or P
hysi
cal F
low
s
Turb
ulen
cedi
ffus
eshe
at a
way
fro
m t
he
RAN
S M
odel
Flow
pat
h pa
ralle
ll to
w
all.
La
min
ar d
iffu
sion
is
yw
all (
very
eff
ecti
ve).
augm
ente
d by
a t
urbu
lent
di
ffus
ion
term
.
LWRi
i
1613 45
Impa
ct o
f Tu
rbul
ence
Mod
els
–3
pred
icti
ons
Thre
e as
sum
ptio
ns f
or t
urbu
lenc
e yi
eld
thre
edi
ffer
ent
resu
lts
for
heat
flux
heat
flu
x.
LWRi
i
1614 45
Turb
ulen
ce M
odel
ing
is a
Pra
ctic
al N
eces
sity
LWRi
i
1615 45
Stat
e of
the
“A
RT”
•RA
NS
appr
oach
es d
omin
ate
due
to t
he in
here
nt e
ffic
ienc
y an
d de
mon
stra
ted
usef
ulne
ss.
–D
NS
is im
prac
tica
l (no
t on
the
hor
izon
for
indu
stri
al p
robl
ems)
.–
LES
use
is g
row
ing.
•CF
Dan
alys
tsbe
nefi
tfr
om:
CFD
ana
lyst
s be
nefi
t fr
om:
–do
cum
ente
d co
des
and
mod
els
–ov
er 1
00 y
ears
of
turb
ulen
ce r
esea
rch
bli
hd
bt
tig
idli
(lt
il
)–
publ
ishe
d be
st p
ract
ice
guid
elin
es (
mul
tipl
e so
urce
s)–
publ
ishe
d be
nchm
ark
and
asse
ssm
ent
stud
ies
–ve
rifi
cati
on a
nd v
alid
atio
n gu
ides
–de
dica
ted
jour
nals
and
con
fere
nces
–a
very
larg
e us
er b
ase
–ge
nera
lpur
pose
tool
sal
ong
wit
hsp
ecia
lized
sing
lepu
rpos
eco
des
gene
ral p
urpo
se t
ools
alo
ng w
ith
spec
ializ
ed s
ingl
e pu
rpos
e co
des
•Is
CFD
rea
lly a
n "A
RT ?
”
LWRi
i
1616 45
CFD
as
an A
rt
•“i
n th
is f
ield
, th
ere
is a
t le
ast
as m
uch
arti
stry
assc
ienc
e”ar
tist
ry a
s sc
ienc
e–
Roac
he,
P.,
Fund
amen
tals
of
Com
puta
tion
al F
luid
Dyn
amic
s, p
age
1, 1
998.
•Tu
rbul
ence
mod
elin
g ca
n be
the
leas
t of
our
g
conc
erns
. M
odel
ing
also
invo
lves
:–
phys
ical
des
crip
tion
s of
the
dom
ain,
bou
ndar
y p
yp
,y
and
init
ial c
ondi
tion
s, a
nd t
he m
ater
ials
–se
lect
ion
of m
odel
s, o
ptio
ns,
and
a co
mpu
tati
onal
mes
h–
solu
tion
pro
cedu
res
–se
nsit
ivit
y st
udie
s an
d va
lidat
ion
LWRi
i
1617 45
Two
Use
rs >
> D
iffe
rent
Sol
utio
ns?
•Be
st P
ract
ice
guid
elin
es l
ayou
t m
odel
ing
appr
oach
esth
atca
nle
adto
som
ede
gree
ofap
proa
ches
tha
t ca
n le
ad t
o so
me
degr
ee o
f co
nsis
tenc
y.
–Th
ese
can
befo
llow
edfo
rsm
allp
robl
ems
Thes
e ca
n be
fol
low
ed f
or s
mal
l pro
blem
s.
•La
rge
indu
stri
al s
cale
CFD
mod
els
typi
cally
re
quir
eco
mpr
omis
e(
db
fti
t!!)
requ
ire
com
prom
ise.
(nee
d an
swer
s be
fore
ret
irem
ent!
!)
–si
mpl
ifie
d ge
omet
ry a
nd b
ound
ary
cond
itio
nsi
lifi
dd
lid
lh
–si
mpl
ifie
d m
odel
s, n
on-i
deal
mes
h–
com
prom
ised
sol
utio
n pr
oced
ures
lii
dlid
iff
–lim
ited
val
idat
ion
effo
rts
LWRi
i
1618 45
ESBW
R Ex
ampl
e
•Lar
ge c
ompl
ex m
odel
•Sim
plif
icat
ions
are
nee
ded
to m
odel
the
core
byp
ass
regi
on.
•Tw
o se
para
te C
FD u
sers
sol
ved
the
•ABW
R Fi
gure
for
illu
stra
tion
sam
e by
pass
mix
ing
prob
lem
.
•Ref
: w
ww
.ge-
ener
gy.c
om
LWRi
i
1619 45
ESBW
R M
odel
s (T
wo
App
roac
hes)
•det
aile
d•C
ompl
ete
bloc
kage
•46M
cel
ls
•Con
trol
rod
mod
el•S
LCS
inje
ctio
n no
zzle
•45M
cel
ls•s
impl
ifie
d•D
etai
led
mod
el u
sed
to
com
pute
blo
ckag
e.•3
day
s fo
r 1s
tra
nsie
nt o
n 60
cpu
s
LWRi
i
1620 45
ESBW
R M
odel
ing
Resu
lts
•SLC
S no
zzle
flo
ws
•bul
k by
pass
flo
ws
LWRi
i
1621 45
ESBW
R M
odel
ing
Sum
mar
y
•Int
egra
ted
resu
lts
show
ed r
easo
nabl
e ag
reem
ent
and
conf
irm
ed t
hat
syst
em
code
ass
umpt
ions
wer
e ap
prop
riat
e. L
ocal
det
ails
wer
e no
t co
mpa
red.
Thi
s
exam
ple
high
light
s ho
w li
mit
ed r
esou
rces
can
res
ult
in c
reat
ive
sim
plif
icat
ions
for
larg
e pr
oble
ms.
•Som
e ot
her
mod
elin
g di
ffer
ence
s in
clud
ed:
•pas
sive
sca
lar
vs.
sepa
rate
den
sity
for
inj
ecti
on f
luid
tb
ld
l•t
urbu
lenc
e m
odel
•bou
ndar
y co
ndit
ions
/ w
all t
reat
men
ts
•vol
ume
diff
eren
ces
due
tosi
mpl
ific
atio
nsvo
lum
e di
ffer
ence
s du
e to
sim
plif
icat
ions
•out
let
boun
dary
det
ails
•mes
h qu
alit
y an
d ty
pe
•dif
fere
nt c
odes
LWRi
i
1622 45
Code
s an
d M
etho
ds
•N
umer
ical
met
hods
hav
e be
en d
evel
opin
g fo
rov
er10
0ye
ars.
The
adve
ntof
the
for
over
100
yea
rs.
The
adv
ent
of t
he
mod
ern
com
pute
r ha
s ac
cele
rate
d th
e pr
oces
s.Th
eva
riet
yof
tech
niqu
esar
eto
opr
oces
s.
The
vari
ety
of t
echn
ique
s ar
e to
o nu
mer
ous
to li
st.
•Th
ena
ture
ofth
eN
avie
r-St
okes
equa
tion
s•
The
natu
re o
f th
e N
avie
r-St
okes
equ
atio
ns
and
boun
dary
con
diti
ons
mak
e it
alm
ost
impo
ssib
leto
find
asi
ngle
“bes
t”m
etho
dim
poss
ible
to
find
a s
ingl
e be
st m
etho
d.•
Code
s ar
e co
mm
only
cre
ated
for
spe
cifi
c fl
bd
diti
flow
or
boun
dary
con
diti
ons.
LWRi
i
1623 45
Com
mon
Cho
ices
•A
few
gen
eral
pur
pose
cod
es a
re w
idel
y us
ed.
Thes
eco
des
rely
ona
rela
tive
lysm
all
used
. T
hese
cod
es r
ely
on a
rel
ativ
ely
smal
l nu
mbe
r of
wel
l do
cum
ente
d op
tion
s co
veri
nga
rang
eof
met
hods
wit
hin
asi
ngle
cove
ring
a r
ange
of
met
hods
wit
hin
a si
ngle
us
er in
terf
ace.
•Th
em
ost
wid
ely
used
code
sin
the
nucl
ear
•Th
e m
ost
wid
ely
used
cod
es in
the
nuc
lear
sa
fety
com
mun
ity
incl
ude:
ANSY
S/FL
UEN
Tan
dAN
SYS/
CFX
–AN
SYS/
FLU
ENT
and
ANSY
S/CF
X–
CDAd
apco
’sst
arcc
m+
and
Star
CDO
F–
Ope
nFoa
m–
Nep
tune
_CFD
LWRi
i
1624 45
Typi
cal F
eatu
res
for
Gen
eral
Pur
pose
CFD
Too
ls
•Cu
stom
inte
rfac
e fo
r ge
omet
ry a
nd m
esh
desi
gn•
Stea
dy o
r tr
ansi
ent
solv
ers
in b
oth
2D,
axis
ymm
etri
c, a
nd 3
D•
Inco
mpr
essi
ble
or c
ompr
essi
ble
opti
ons
•La
min
ar o
r tu
rbul
ent
opti
ons
•Tu
rbul
ent
RAN
SD
ESLE
S•
Turb
ulen
t RA
NS,
DES
, LE
S•
RAN
S 1-
equa
tion
, 2-
equa
tion
, an
d Re
Str
ess
opti
ons.
•Co
uple
d he
at t
rans
fer
wit
h st
ruct
ures
•Ra
diat
ion
exch
ange
wit
h or
wit
hout
flu
id p
arti
capa
tion
•Ch
emic
al r
eact
ions
•M
ulti
ple
flui
dsp
ecie
s•
Mul
tipl
e fl
uid
spec
ies
•M
ulti
-pha
se o
ptio
ns (
CMFD
)•
Segr
egat
ed a
nd C
oupl
ed s
olve
r ap
proa
ches
•M
ulti
grid
solv
er t
echn
olog
y
LWRi
i
1625 45
Pipe
T-J
unct
ion
Exam
ple
•Th
e O
ECD
/NEA
spo
nsor
ed a
blin
d be
nchm
ark
onsi
ngle
phas
em
ixin
gat
api
pebe
nchm
ark
on s
ingl
e ph
ase
mix
ing
at a
pip
e T-
junc
tion
(saf
ety
issu
e re
late
d to
the
rmal
fat
igue
).
LWRi
i
1626 45
T-Ju
ncti
on A
ppro
ach
•LE
S ne
eded
to
pred
ict
fluc
tuat
ions
–D
NS
not
prac
tica
lD
NS
not
prac
tica
l–
DES
cou
ld b
e co
nsid
ered
•Re
lati
vely
smal
lpro
blem
atm
odes
tRe
#•
Rela
tive
ly s
mal
l pro
blem
at
mod
est
Re#
•W
ell d
efin
ed b
ound
ary
cond
itio
ns•
Adeq
uate
lit
erat
ure
on s
imila
r pr
oble
ms
•Si
mpl
e, w
ell
defi
ned
geom
etry
p,
gy
LWRi
i
1627 45
T-Ju
ncti
on M
odel
•Ap
proa
ch b
ased
on
dem
onst
rate
d be
st
prac
tice
sfo
rsi
mila
rpr
oble
ms.
prac
tice
s fo
r si
mila
r pr
oble
ms.
–LE
S –
dyna
mic
sub
grid
turb
ulen
ce m
odel
–va
riab
lem
ater
ialp
rope
rtie
s–
vari
able
mat
eria
l pro
pert
ies
–bo
unde
d ce
ntra
l dif
fere
nce
for
ener
gy e
quat
ion
seco
ndor
der
spat
iald
eriv
ativ
esfo
rm
omen
tum
–se
cond
ord
er s
pati
al d
eriv
ativ
es f
or m
omen
tum
–se
cond
ord
er im
plic
it t
ime
adva
ncem
ent
tim
est
ep0
0005
s(C
FL<
10)
–ti
me
step
= 0
.000
5s (
CFL
< 1.
0)–
hexa
gona
l (AR
= 1
.0)
mes
h in
cen
tral
reg
ion
•1
5mm
cube
s•
1.5m
m c
ubes
•0.
2mm
at
wal
l bou
ndar
y•
34 M
illio
n ce
lls
LWRi
i
1628 45
T-Ju
ncti
on (
LES)
Sol
utio
n
LWRi
i
1629 45
T-Ju
ncti
on R
esul
ts
LWRi
i
1630 45
T-Ju
ncti
on (
LES)
Log
isti
cs
•SO
LUTI
ON
PRO
CED
URE
•co
mpu
te u
pstr
eam
flo
w b
ound
ary
cond
itio
ns•L
ES
•co
mpu
te s
tead
y RA
NS
init
ial c
ondi
tion
•co
mpu
te 5
-10
seco
nds
of L
ES s
tart
up
2030
df
LES
d•
com
pute
20-
30 s
econ
ds o
f LE
S da
ta
•pr
oces
s 40
,000
–60
,000
dat
a sa
mpl
es t
o es
tabl
ish
stat
isti
cal r
esul
ts
•CO
MPU
TIN
G•C
OM
PUTI
NG
•6
wee
ks o
n 14
0 cp
u(3
.2 G
Hz)
64
bit
linux
clus
ter
•ea
ch c
ompl
ete
solu
tion
sav
ed o
n di
sk =
5 G
bp
•RAN
S
•CO
MPA
RE -
RAN
S so
luti
on (
<1 d
ay)
LWRi
i
1631 45
Seve
re A
ccid
ent
Nat
ural
Cir
cula
tion
Exa
mpl
e
•Th
e N
RC h
as b
een
stud
ying
the
rmal
-hyd
raul
ic
phen
omen
are
late
dto
low
prob
abili
tyse
vere
phen
omen
a re
late
d to
low
-pro
babi
lity
seve
re-
acci
dent
indu
ced-
failu
resc
enar
ios
in p
ress
uriz
ed
wat
erre
acto
rs(P
WRs
).w
ater
rea
ctor
s (P
WRs
).•
Thes
e sc
enar
ios
are
impo
rtan
t be
caus
e of
the
po
tent
ial f
or c
onta
inm
ent
bypa
ss c
ause
d by
an
pyp
yin
duce
d st
eam
gen
erat
or (
SG)
tube
fai
lure
.•
Seve
re a
ccid
ent
anal
ysis
too
ls s
uch
as M
ELCO
R or
y
SCD
AP/R
ELAP
5 (a
nd o
ther
s) a
re u
sed
to p
redi
ct
the
syst
em b
ehav
ior
duri
ng t
hese
typ
es o
f ev
ents
.
LWRi
i
1632 45
Low
Pro
babi
lity
Seve
re A
ccid
ent
Indu
ced
Failu
re
A F
ast
Scen
ario
•lo
ss o
f of
fsit
e po
wer
, fa
ilure
of
dil
td
dies
el g
ener
ator
s, a
nd
auxi
liary
fee
dwat
er•
reac
tor
cool
ant
pum
p se
al
LOCA
and
sec
onda
ry s
ide
boil
off
off
•se
cond
ary
syst
em d
ry o
ut,
prim
ary
inve
ntor
y lo
st t
hrou
gh
safe
ty v
alve
s an
d pu
mp
seal
s•
loop
circ
ulat
ion
stop
s•
loop
cir
cula
tion
sto
ps
•w
ater
leve
l bel
ow h
ot le
gs,
natu
ral c
ircu
lati
on o
f su
perh
eate
d st
eam
core
nco
ers
oid
ies
and
•co
re u
ncov
ers,
oxi
dize
s an
d re
leas
es s
igni
fica
nt e
nerg
y.
Indu
ced
failu
re is
pre
dict
ed f
or
RCS
•hi
gh-d
ry-l
owco
ndit
ions
•hi
gh-d
ry-l
ow c
ondi
tion
s ch
alle
nge
the
SG t
ubes
LWRi
i
1633 45
CFD
Mod
el
•pri
mar
y si
de o
f SG
•371
indi
vidu
al t
ubes
•Pre
serv
e fl
ow a
rea
•Mod
els
adde
d fo
r
heat
tran
sfer
and
heat
tra
nsfe
r an
d
shea
r.
•hot
leg
and
surg
e lin
es
•sim
plif
ied
vess
el r
egio
n
•hyd
roge
n in
clud
ed
•tra
nsie
ntRA
NS
•tra
nsie
nt R
ANS
•sec
ond
orde
r Re
ynol
ds
Stre
ss t
urbu
lenc
e m
odel
ing
•7.8
Mill
ion
cells
LWRi
i
1634 45
Stea
m G
ener
ator
Tub
e M
odel
ing
•D
esig
n G
oals
–m
atch
flo
w a
rea,
hei
ght,
pr
essu
re d
rop,
and
hea
t tr
ansf
er
tit
hi
lifi
dt
bra
tes
wit
h a
sim
plif
ied
tube
bu
ndle
•Ap
proa
ch–
redu
ce n
umbe
r of
tub
es–
poro
us m
edia
mod
els
in b
undl
e•
augm
ents
pre
ssur
e dr
op•
augm
ents
heat
tran
sfer
rate
•au
gmen
ts h
eat
tran
sfer
rat
e–
deve
lop
pres
sure
dro
p an
d he
at
tran
sfer
bas
ed u
pon
deta
iled
mod
el
•Re
sult
s–
mat
ch f
low
are
a, h
eigh
t,
pres
sure
dro
p, a
nd h
eat
tran
sfer
al
ong
tube
sal
ong
tube
s–
a pr
acti
cal t
ube
bund
le a
t ab
out
5% o
f th
e co
mpu
tati
onal
cos
t
LWRi
i
1635 45
Ani
mat
ed T
empe
ratu
re C
onto
urs
LWRi
i
1636 45
Seve
re A
ccid
ent
Nat
ural
Cir
cula
tion
Res
ults
–ho
t le
g fl
ow r
ate
corr
elat
ion
corr
elat
ion
–su
rge
line
flow
/tem
pera
ture
p–
mix
ing
and
entr
ainm
ent
in t
he
hot
leg
and
inle
tho
t le
g an
d in
let
plen
um–
SG t
ube
bund
le
flow
s an
d fl
ow a
rea
–ho
t-tu
be
dist
ribu
tion
sdi
stri
buti
ons
LWRi
i
1637 45
Seve
re A
ccid
ent
Nat
ural
Cir
cula
tion
Res
ults
•Pre
dict
ions
pro
vide
dist
ribu
tion
of
tem
pera
ture
s.
•Num
erou
sse
nsit
ivit
y•N
umer
ous
sens
itiv
ity
stud
ies
are
com
plet
ed t
o
dete
rmin
e ke
y
para
met
ers.
•Res
ults
exp
and
on t
he
know
ledg
e fr
om t
he
avai
labl
e ex
peri
men
tal
data
.da
ta.
LWRi
i
1638 45
Seve
re A
ccid
ent
Ana
lysi
s Ch
alle
nges
•Se
vere
acc
iden
t bo
unda
ry c
ondi
tion
s an
d be
havi
orha
vela
rge
unce
rtai
nty.
beha
vior
hav
e la
rge
unce
rtai
nty.
•Re
lief
valv
es c
ause
rap
id d
epre
ssur
izat
ions
.L
ti
ld
lit
•La
rge
geom
etri
c sc
ale
and
com
plex
ity.
•H
eat
exch
ange
wit
h co
mpl
ex s
truc
ture
s.•
Valid
atio
n fo
r m
odel
s is
nee
ded.
–m
ixed
con
vect
ion
in h
ot le
g g–
radi
ativ
ehe
at e
xcha
nge
–ri
sing
plum
ebe
havi
orin
conf
ined
geom
etry
risi
ng p
lum
e be
havi
or in
con
fine
d ge
omet
ry
LWRi
i
1639 45
CMFD
Exp
erie
nce
–Pr
essu
rize
d Th
erm
al S
hock
•CM
FD (
or s
impl
y m
ulti
-pha
se C
FD)
tech
niqu
esar
est
illin
ape
riod
ofra
pid
tech
niqu
es a
re s
till
in a
per
iod
of r
apid
de
velo
pmen
t.
The
num
ber
and
com
plex
ity
ofco
rrel
atio
nsin
volv
edin
the
phas
eto
of c
orre
lati
ons
invo
lved
in t
he p
hase
to
phas
e ex
chan
ges
and
phas
e to
tur
bule
nce
exch
ange
sm
akes
CMFD
muc
hm
ore
diff
icul
tex
chan
ges
mak
es C
MFD
muc
h m
ore
diff
icul
t th
an C
FD.
•Th
enu
clea
rsa
fety
com
mun
itie
sef
fort
sto
•Th
e nu
clea
r sa
fety
com
mun
itie
s ef
fort
s to
re
fine
the
rmal
-hyd
raul
ic p
redi
ctio
ns f
or P
TS
anal
yses
isa
good
exam
ple
ofth
eef
fort
anal
yses
is a
goo
d ex
ampl
e of
the
eff
ort
requ
ired
in C
MFD
.
LWRi
i
1640 45
Med
ium
to
Larg
e Br
eak
PTS
Scen
ario
•Sa
fety
inje
ctio
n w
ater
ent
ers
dow
ncom
er
from
cold
leg
(hig
hpr
essu
rest
eam
from
col
d le
g (h
igh
pres
sure
ste
am
envi
ronm
ent)
.
LWRi
i
1641 45
PTS
Inte
rnat
iona
l Com
para
tive
Ass
essm
ent
•Te
mpe
ratu
re
pred
icti
ons
1m
eter
pred
icti
ons
1 m
eter
be
low
col
d le
g.10
0ova
riat
ion
–10
0ova
riat
ion
Ht
tf
•H
eat
tran
sfer
pr
edic
tion
s 1
met
er
bl
ldl
belo
w c
old
leg.
–10
,000
W/m
2 -K
iti
vari
atio
n•1
990’
s C
MFD
was
not
att
empt
ed
LWRi
i
1642 45
Euro
pean
Eff
orts
on
PTS
•EU
ROFA
STN
ET (
–20
02)
iden
tifi
es P
TS a
s a
key
safe
tyis
sue
key
safe
ty is
sue
•N
URE
SIM
( -
2008
) an
d N
URI
SP:
foc
used
si
gnif
ican
tre
sour
ces
onth
ePT
San
alys
issi
gnif
ican
t re
sour
ces
on t
he P
TS a
naly
sis
issu
e an
d CM
FD.
OEC
D/N
EACF
Dk
h(X
CFD
4NRS
2008
•O
ECD
/NEA
CFD
wor
ksho
ps (
XCFD
4NRS
, 20
08
and
CFD
4NRS
-3,
2010
) ha
d se
ssio
ns
ddi
td
tPT
Sl
ide
dica
ted
to P
TS a
naly
sis.
•M
any
test
s ha
ve b
een
com
plet
ed o
r pl
anne
d to
sup
port
the
dev
elop
men
t of
CM
FD f
or
PTS.
LWRi
i
1643 45
Stat
us o
f CM
FD f
or P
TS
•G
ener
ally
spe
akin
g, C
MFD
is s
till
an a
rea
for
rese
arch
and
not
rea
dy f
or a
pplic
atio
n.y
pp–
wit
h th
e ex
cept
ion
of a
few
spe
cial
cas
es
•Si
gnif
ican
tim
prov
emen
tsha
vebe
enm
ade
•Si
gnif
ican
t im
prov
emen
ts h
ave
been
mad
e an
d ne
w a
ppro
ache
s ar
e be
ing
appl
ied
to
the
PTS
prob
lem
the
PTS
prob
lem
.•
Som
e in
divi
dual
phe
nom
ena
are
fair
ly w
ell
mod
eled
but
inte
rgra
ted
solu
tion
sar
em
odel
ed b
ut in
terg
rate
d so
luti
ons
are
gene
rally
sti
ll un
sati
sfac
tory
.Th
il
kf
it
ld
tf
•Th
ere
is a
lack
of
expe
rim
enta
l da
ta f
or
cert
ain
key
phen
omen
a.
LWRi
i
1644 45
CMFD
for
PTS
(D.
Luca
s, D
. Be
stio
n, N
URE
TH-1
2 “
On
the
Sim
ulat
ion
of T
wo-
Phas
e Fl
ow P
ress
uriz
ed T
herm
al S
hock
(PT
S),
2007
)
•An
y co
rrel
atio
n ba
sed
mod
el is
cha
lleng
ed
by t
he v
arie
ty o
f fl
ow r
egim
es.
yy
g•
Code
s re
lyin
g m
ore
on f
irst
pri
ncip
le
appr
oach
esha
vea
bett
erch
ance
ofso
lvin
gap
proa
ches
hav
e a
bett
er c
hanc
e of
sol
ving
th
ese
type
s of
pro
blem
s in
the
long
ter
m.
LWRi
i
1645 45
Sum
mar
y
•CF
D u
se f
or n
ucle
ar s
yste
ms
is g
row
ing.
•RA
NS
met
hods
dom
inat
ebu
tD
ESan
dLE
S•
RAN
S m
etho
ds d
omin
ate
but
DES
and
LES
m
etho
ds a
re b
ecom
ing
popu
lar.
Af
lt
lt
idl
•A
few
gen
eral
pur
pose
too
ls a
re m
ost
wid
ely
used
but
a m
ulti
tude
of
tool
s ar
e av
aila
ble.
•CF
D f
or in
dust
rial
sca
le p
robl
ems
relie
s on
ex
peri
ence
and
cre
ativ
ity
in m
any
case
s.–
“the
ART
of
CFD
”
•G
ener
al p
urpo
se C
MFD
is a
n ar
ea o
f p
pre
sear
ch m
ore
than
an
appl
icat
ion.