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Transcript of Turbulence closure models and sediment transport routines in ROMS John C. Warner, U.S. Geological...
![Page 1: Turbulence closure models and sediment transport routines in ROMS John C. Warner, U.S. Geological Survey Christopher R. SherwoodU.S. Geological Survey.](https://reader035.fdocuments.net/reader035/viewer/2022062714/56649d005503460f949d216b/html5/thumbnails/1.jpg)
Turbulence closure modelsand
sediment transport routinesin
ROMS
John C. Warner, U.S. Geological Survey
Christopher R. Sherwood U.S. Geological SurveyHernan G. Arango IMCS, Rutgers Richard Signell U.S. Geological SurveyMeinte Blaas IGPP / CESR / IoE, UCLABradford Butman U.S. Geological Survey
![Page 2: Turbulence closure models and sediment transport routines in ROMS John C. Warner, U.S. Geological Survey Christopher R. SherwoodU.S. Geological Survey.](https://reader035.fdocuments.net/reader035/viewer/2022062714/56649d005503460f949d216b/html5/thumbnails/2.jpg)
Outline• Turbulence Closure Models (focus on GLS)
– Available models in ROMS – Background of two-equation models– GLS method
• Numerical implementation• Applications
– Open channel flow(2)– Surface mixed layer deepening– Estuary (idealized + realistic)
• Sediment Transport Routines– Overview of routines– Applications
• Summary
![Page 3: Turbulence closure models and sediment transport routines in ROMS John C. Warner, U.S. Geological Survey Christopher R. SherwoodU.S. Geological Survey.](https://reader035.fdocuments.net/reader035/viewer/2022062714/56649d005503460f949d216b/html5/thumbnails/3.jpg)
Turbulence Closure Models in ROMS
![Page 4: Turbulence closure models and sediment transport routines in ROMS John C. Warner, U.S. Geological Survey Christopher R. SherwoodU.S. Geological Survey.](https://reader035.fdocuments.net/reader035/viewer/2022062714/56649d005503460f949d216b/html5/thumbnails/4.jpg)
Reynolds Averaged Navier Stokes Equations
Continuity
Momentum
Transport
Equation of State 000 TTβ)s(sα1ρρ
unknowns u, v, w, , temp, sal, ssc,
j
iij
ji
iljijl
j
ij
i
x
Uuu
xg
x
PU
x
UU
t
U
00
12
0
i
i
x
U
jj
jjj x
uxx
Ut
jsj
jjj x
Ssu
xx
SU
t
S
su j ju ijuu
![Page 5: Turbulence closure models and sediment transport routines in ROMS John C. Warner, U.S. Geological Survey Christopher R. SherwoodU.S. Geological Survey.](https://reader035.fdocuments.net/reader035/viewer/2022062714/56649d005503460f949d216b/html5/thumbnails/5.jpg)
Available turbulence closures in ROMS
• Background value
• Analytical expression• BVF - Brunt_Vaisala frequency
• LMD - Large / McWilliams / Doney
• Two equation models:– MY25 - Mellor/Yamada 2.5
– GLS - Umlauf/Burchard Generic Length Scale
![Page 6: Turbulence closure models and sediment transport routines in ROMS John C. Warner, U.S. Geological Survey Christopher R. SherwoodU.S. Geological Survey.](https://reader035.fdocuments.net/reader035/viewer/2022062714/56649d005503460f949d216b/html5/thumbnails/6.jpg)
Available turbulence closures in ROMS
• Background value– ocean.in
! Vertical mixing coefficients for active tracers: [1:NAT,Ngrids]
AKT_BAK == 5.0d-6 5.0d-6 ! m2/s
! Vertical mixing coefficient for momentum: [Ngrids].
AKV_BAK == 5.0d-6 ! m2/s
– mod_mixing.FDO itrc=1,NAT
MIXING(ng) % Akt(Imin:Imax,Jmin:Jmax,1:N(ng)-1,itrc) = & & Akt_bak(itrc,ng)
END DO
MIXING(ng) % Akv(Imin:Imax,Jmin:Jmax,1:N(ng)-1) = Akv_bak(ng)
![Page 7: Turbulence closure models and sediment transport routines in ROMS John C. Warner, U.S. Geological Survey Christopher R. SherwoodU.S. Geological Survey.](https://reader035.fdocuments.net/reader035/viewer/2022062714/56649d005503460f949d216b/html5/thumbnails/7.jpg)
Available turbulence closures in ROMS
• Analytical– cppdefs.h
#define ana_vmix
– analytical.F, ana_vmix# elif defined SED_TEST1
DO k=1,N(ng)-1 ! vonkar*ustar*z*(1-z/D) DO j=JstrR,JendR DO i=IstrR,IendR Akv(i,j,k)=0.025_r8*(h(i,j)+z_w(i,j,k))* & & (1.0_r8-(h(i,j)+z_w(i,j,k)) / (h(i,j)+zeta(i,j,knew))) Akt(i,j,k,itemp)=Akv(i,j,k)*0.49_r8/0.39_r8 Akt(i,j,k,isalt)=Akt(i,j,k,itemp) END DO END DO END DO
![Page 8: Turbulence closure models and sediment transport routines in ROMS John C. Warner, U.S. Geological Survey Christopher R. SherwoodU.S. Geological Survey.](https://reader035.fdocuments.net/reader035/viewer/2022062714/56649d005503460f949d216b/html5/thumbnails/8.jpg)
Available turbulence closures in ROMS
• BVF
• !-----------------------------------------------------------------------• ! Set tracer diffusivity as function of the Brunt-vaisala frequency.• ! Set vertical viscosity to its background value.• !-----------------------------------------------------------------------
– cppdefs.h– #define BVF_MIXING /* Activate Brunt-Vaisala frequency mixing */
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Available turbulence closures in ROMS
• LMD– cppdefs.h
/* Options for the Large/McWilliams/Doney interior mixing */# define LMD_MIXING
#undef LMD_SKPP /* surface boundary layer KPP mixing */#undef LMD_BKPP /* bottom boundary layer KPP mixing */#undef LMD_NONLOCAL /* nonlocal transport */
#undef LMD_RIMIX /* diffusivity due to shear instability */#undef LMD_CONVEC /* convective mixing due to shear instability */#undef LMD_DDMIX /* double-diffusive mixing */
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Available turbulence closures in ROMS
• MY25– cppdefs.h
#define MY25_MIXING
• GLS– cppdefs.h
#define GLS_MIXING
• For either MY25 or GLS – cppdefs.h
#define KANTHA_CLAYSON
or #define CANUTO_A
or #define CANUTO_B
#define N2S2_HORAVG
Two Equation Models
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Transport equation for Reynolds Stresses
Pij
ij
Bij
ij
ij
ij
ijij
ijij
ijij
ijjiij
Skc
PDc
BBc
PPc
kuuk
c
5
4
3
2
1
3
2
3
2
3
2
3
2
lB
q
1
3
5120320
20800
500
77600
52982
5
4
3
2
1
..
.
.
.
..
c
c
c
c
c
CAKC
pug
B
x
UuuP
i
jij
30
1
2 3
Pressure-strain correlation
dissipation Triple correlation
Reynolds Stress transport
kji
kij
jik
Tkji uux
uux
uux
uuu
l
i
l
j
ij
ji
ijji
mijlmmjilml
l
jli
l
ijl
jil
jiljill
ji
x
u
x
u
x
pu
x
pu
ugug
uuuu
x
Uuu
x
Uuu
uux
uuuuuUx
uut
2
1
1
2
0
0
j
i
i
jij
i
llj
j
lliij
x
U
x
US
x
Uuu
x
UuuD
2
1
ijij 3
2
1
2
3
![Page 12: Turbulence closure models and sediment transport routines in ROMS John C. Warner, U.S. Geological Survey Christopher R. SherwoodU.S. Geological Survey.](https://reader035.fdocuments.net/reader035/viewer/2022062714/56649d005503460f949d216b/html5/thumbnails/12.jpg)
Transport equation for Reynolds Stresses:scaled + boundary layer approximation
Pij
ij
Bij
ij
ij
ij
j
i
i
jijji
ijji
mijlmmjilml
l
jli
l
ijl
jil
lji
lij
jil
TCjill
ji
x
U
x
Ukckuu
kc
ugug
uuuu
x
Uuu
x
Uuu
uux
uux
uux
uux
uuUx
uut
3
2
2
1
3
2
1
2
51
0
Scaling by q3/
BL: - neglect rotation - neglect gradients parallel to boundary
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Algebraisation of second moment clsoures:eddy viscosity and diffusivity
z
US
kcuw M
2302
z
US
kcw H
2302
z
USlquw M
zSlqw H
2
2
1qk
l
kc
2330
/
))-C(B A(GA -
/BA - AS
hH
3212
112
1631
61
h
hh/-
M GAA-
G))S-C(AAAA(BS
21
2211131
1
91
1918
k
lNGh 2
22
Table 2. Kantha and Clayson (1994) stability function parameters
So now need 2 equations: one for q (or k)one for l (or )
or
MV SlqK
HH SlqK
“k” “e” notation “q” “l” notation
HH Sk
K
2
2
MV Sk
K
2
2
eddy viscosityeddy viscosity
eddy diffusivityeddy diffusivity
Parameter A1 A2 B1 B2 C2 C3
Value 0.92 0.74 16.6 10.1 0.7 0.2
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Two equation turbulence closuresMY25 (Mellor, Yamada 1982)
k - (Rodi, 1980)
k - (Wilcox, 1988)
εBPq
zSlq
z
q
xU
q
t qi
i
222
222
εBPz
kK
zx
kU
t
k
k
M
ii
k
cBcPckz
K
zxU
tM
ii
2
231
εBPz
kK
zx
kU
t
k
k
M
ii
k
cBcPckz
K
zxU
tM
ii
2
231
wallqi
i FB
qBPEllq
zSlq
zlq
xUlq
t 1
3
1222
2
21sb
sbwall dd
ddlEF
2
2 ,
11
sbwall ddMIN
lEF
2
4
2
21sb
wall d
lE
d
lEF
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Why does MY25 need a wall proximity function?
assume st st, no horiz grad, no B
2
21zL
lEF
where
in bottom constant stress layer : l = z, P = , q2 is const
FEB
qSq q 1
1
3230
1
21
B
FESq
Negative diffusion without a wall function
2
21zL
lEF
2
21
3
1222 1
zq
ii L
lE
B
qBPEllq
zSlq
zlq
xUlq
t
FB
qPEllq
zSlq
z q1
3
120
szbszbs
bsz dLddMINL
dd
ddL
;,;
E1 = 1.8 B1 =16.6 E2 = 1.33 Sq = 0.2
![Page 16: Turbulence closure models and sediment transport routines in ROMS John C. Warner, U.S. Geological Survey Christopher R. SherwoodU.S. Geological Survey.](https://reader035.fdocuments.net/reader035/viewer/2022062714/56649d005503460f949d216b/html5/thumbnails/16.jpg)
“Generic Length Scale” turbulence closure
nmp 0μ kcψ l
1-3/230μ εkcl
1/nm/n3/2p/n30μ ψkcε
Umlauf and Burchard (2003) J. Mar. Res.
εBPz
kK
zx
kU
t
k
k
M
ii
FcBcPckz
K
zxU
tM
ii
231
Warner, Sherwood, Arango, and Signell (2005) Performance of four turbulence closure models implemented using a generic length scale method, Ocean Modelling 8, p. 81-113.
c2: free decay of homogenous turbulencec1: homogenous sheared grid turbulence
c3: buoyancy parameter for unstable
k: diffusion of k: diffusion of fit to law of wall
p, m, n : define
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Determination of c3 buoyancy coefficient
31222/330
21 20 ccNlSkckccc H
Start with transport equation for Assume: P + B = Substitute expressions for KM, B, and can derive:
length scale limitation l < sqrt (0.56 k) / Nyields:
213 08.408.5 ccc for Kantha/Clayson stability functions
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Numerical implementationgrid + limitations
Length scale limitation:2
2 560
N
k.l
k (q2) limitation: k = MAX(k, 1e-8)
30
12330
NLεkcl -/
μ
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Numerical implementation
time step advective transport terms
time step with P, B
time step (F)
apply BCs, time step diff term, update values
calc length scale
calc buoyancy parameter Gh = ( L N / Q) ^2
limit Gh
calc stability functions Sm, Sh = functs (Gh)
calc eddy visc and eddy diffKm = Q L Sm, Kh = Q L Sh, Kq = Q
L Sq
MY25 GLS
εBPz
kK
zx
kU
t
k
k
M
ii
FcBcPckz
K
zxU
tM
ii
231
εBPq
zSlq
z
q
xU
q
t qi
i
222
222
2
21
3
1222 1
zq
ii L
lE
B
qBPEllq
zSlq
zlq
xUlq
t
22 NKB;MKP HM 22 NKB;MKP HM
lB
q
q
lql
1
3
2
2
; ; wall fnct (l).
q2, q2l at new time step
N
qlMINl
q
lql ited
53.0,; lim2
2
2
22lim
q
NlG ited
h
)(, hHM GfunctSS
MitedV SlqK lim
HitedH SlqK lim
2
2q
xU
ii
lqx
Ui
i2
ii x
U
ii x
kU
k, at new time step
/nm/n/p/n
μ ψkcε 12330
2
22lim
q
NlG ited
h
)(, hHM GfunctSS
MitedV SlkK lim2
HitedH SlkK lim2
nn/m p
μn NkcMINψ 202/56.0,
22 560
N
k.l
m/n1/np/n 0μ kψc
itedllim
32
1
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Test Cases
1) Open channel flow (2 simulations)
to compare closures with velocity log layer
2) Mixed layer deepening
to calibrate c3 buoyancy parameter
3) Estuary
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Test Case # 1: Steady Open Channel Flow:Experimental Description
L = 10000, W=1000, H=10 mZob = 0.005ubar = 1m/sS0 = 4x10-5 m/mtcr = 0.05 N/m2
E = 5x10-5 kg/m2/sPorosity = 0.90
grid spacings: dx = 100m, dy = 10m, dz = 0.25m)
dt = 30s5000 s simulated (st. st. reached)
Domain parameters
Model parameters2 simulations
Q
Q
1) and Q
2) and
zx
![Page 22: Turbulence closure models and sediment transport routines in ROMS John C. Warner, U.S. Geological Survey Christopher R. SherwoodU.S. Geological Survey.](https://reader035.fdocuments.net/reader035/viewer/2022062714/56649d005503460f949d216b/html5/thumbnails/22.jpg)
Test Case # 1: Steady Open Channel Flow:Analytical Results
uwzx
P
x
UU
t
U
0
1
momentum eq.
linear stress
0Z
zLn
uU
*
H
zzuKM 1*
sm
H
z
z
HLn
uu /.* 0620
1 0
0
H
z
c
uk 1
20
2
*= 0.013 m2/s2 at z = 0
shear velocity
velocity
eddy viscosity
turbulent kinetic energy
z
UK
H
z
xgH
H
zu M
112
*
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Simulation 1Depth and Flow
Q
Test Case # 1: Steady Open Channel Flow
z
UK
H
z
xgH
H
zu
M
1
12
*
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Test Case #2 : Surface mixed layer deepening
L = 5000, W=1000, H=50 mZos = 0.005u*surf = 0.01 m/sN0 = 0.01 /s
grid spacings: dx = 250m, dy = 100m, dz = 0.25m)
dt = 30s30 days simulated
Domain parameters
Model parameters
zxz
Dm
Means to confirm c3 buoyancy parameter
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Test Case #2 : Surface mixed layer deepening
2/12/1*05.1 tNuD osm
Mixed layer depth, Dm
(Price, 1979)
Critical Richardson No. controls evolution of mixed layer deepening
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Test case #3 : Idealized estuary
L = 100000, W=1000, H=5-10 mZob = 0.005River ubar = 0.08m/sTidal ubar = 0.40 m/sS0 = 5x10-5 m/mtcr = 0.05 N/m2 ws = 0.5mm/sE = 1x10-4 kg/m2/sPorosity = 0.90
grid spacings: dx = 500m, dy = 100m, dz = 0.25-0.5 m
dt = 30s20 days (~st. st. reached)
Domain parameters
Model parameters
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Test case #3 : Idealized estuary
L = 100000, W=1000, H=5-10 mZob = 0.005River ubar = 0.08m/sTidal ubar = 0.40 m/sS0 = 5x10-5 m/mtcr = 0.05 N/m2 ws = 0.5mm/sE = 1x10-4 kg/m2/sPorosity = 0.90
grid spacings: dx = 500m, dy = 100m, dz = 0.25-0.5 m
dt = 30s20 days (~st. st. reached)
Domain parameters
Model parameters
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Realistic estuary - Hudson RiverJohn C. Warner W. Rockwell Geyer
James A. Lerczak
200 along channel cells
20 lateral cells
20 vertical levels
![Page 29: Turbulence closure models and sediment transport routines in ROMS John C. Warner, U.S. Geological Survey Christopher R. SherwoodU.S. Geological Survey.](https://reader035.fdocuments.net/reader035/viewer/2022062714/56649d005503460f949d216b/html5/thumbnails/29.jpg)
Model parameters
Initial salinity
distributionlevel free surface
zero velocity
salt distribution
dt = 30s
z0 = 0.005
Simulate: - tides, salt, suspended-sediment
- for 50 days (days 100 – 150 , 2003)
Initial parameters
Operational parameters
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• Northern end: – Measured Q– Salinity = 0
• Southern end:– Tidal boundary using observed
free surface only
– Salinity gradient condition
Boundary conditions
salbndry = salj=1+ dSdx
t11
t00
t1
t1
d
tb
t1t
01t
0 ηhηh0.5
VvC
Δy
ηηgΔtvv
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Free surface model results
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Model-data comparison at site N3 (22 km)
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Comparison of vertical structure of salt and velocity (k-)
Neap tide
Spring tide
Model
Model
Observed
Observed
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Comparison of 3 closures
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Sediment transport routines in ROMS
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BBL and Sediment• Bottom boundary layer subroutines - enhance bottom
stress to include the average affect of surface waves on the mean currents
(mb_bbl.F and sg_bbl.F)
• Sediment transport subroutine – transport multiple classes of suspended sediment and track evolution of multi-layered bed framework (sediment.F)
• User can specify :
1) just BBL
2) just Sediment
3) or both BBL + Sediment
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Wave - Current BBL Physics• Increased turbulence• Enhanced drag• Enhanced mean stress• Increased maximum stress• Moveable bed roughness• Input:
– Current speed and direction at reference height
– Wave orbital velocity, period, and direction
– Bottom sediment characteristics
• Output:– Apparent drag coefficient– Wave-maximum shear stress– Bedform geometry
current/(current+wave) m
ean/
(cu
rren
t+ w
ave) Non-linear enhancementwave-mean bottom stress
Grant and Madsen (1986) Ann. Rev. Fluid Mech. 18:265-305
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W-C Bottom Boundary Layer Routines
SG_BBL
• Modifed Grant-Madsen w-c model (Styles & Glenn, 2000)
• Formally related to three-layer eddy viscosity profile
• Ripple roughness (Styles & Glenn, 2000)
• Immobile sediment roughness gets default value
• No skin friction / form drag partitioning; no sediment stratification
• Contributed by Rich Styles and Scott Glenn
MB_BBL
• Empirical DATA2 wave-current solution (Soulsby, 1995)
• Ripple geometry for sand or silty beds
• Nikuradse, saltation, ripple, and/or biogenic roughness (Combination of methods)
• Faster than SG_BBL• No skin friction / form drag
partitioning; no sediment stratification
• Contributed by Meinte Blass
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model “flow chart”
set_vbc.F
#if defined bbl_model #else
sg_bbl.F mb_bbl.F
hydrodynamic routines(advection-diffusion)
sediment.F(deposition and erosive fluxes,bed evolution)
#if defined sediment #else
bottom drag:ocean.in
rdrgrdrg2
Zo
waves data:SWAN.nc, ana_waves
T, Dir, Amp / Ub
surficial sed data:ana_sediment,forcing.nc, orsediment.F
bottom(i,j, isd50)idens)iwsed)itauc)
sediment data:ana_sediment or initial.ncbed (i,j,k, thick) botom(i,j, isd50)
age) idens)poro) iwsed)diff) itauc)
bed_frac(i,j,k,ised) irlen)bed_mass(i,j,k,ised) irhgt)
izdef)….. )
bustr, bustrcwmaxbvstr, bvstrcwmaxbottom(i,j, irlen)
irhgt)
bustrbvstr
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Sediment transport – bed layers
Activelayerthick
Activelayerthick
Erosion ceb ττfor
Deposition
502
cw1a
Dk
ττkz
502
cw1a
Dk
ττkz
Rule: create a newlayer for depositionif top layer > 5mm
z
Cw
t
Cs,i
i
iaiis,
ice,
wii
i
dep_fluxz*frac*poro1*ρ
;1τ
τ*frac*poro1*E*dt
MIN
eros_flux
Harris, Wiberg 1997
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Example application : Massachusetts Bay
multibeam backscatter intensity
Surficial mean grain size distribution- binned 2:6
Surficial sediment characteristics
http://pubs.usgs.gov/of/2003/of03-001/index.htm
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Wentworth grade scale
Phi
23456
d ws tce E
mm kg/m3 mm/s N/m2 kg/ m2 s
0.25000 2650 27.00 0.190 5.00E-06
0.12500 2650 8.70 0.140 5.00E-06
0.06250 2650 2.40 0.090 5.00E-06
0.03125 2650 0.62 0.061 5.00E-06
0.01560 2650 0.15 0.038 5.00E-06
Initial conditions:5 sediment classes
8 bed layers (5 cm ea.) Equal fractions
http://pubs.usgs.gov/of/2003/of03-001/htmldocs/nomenclature.htm
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Sed particle property calcs
http://woodshole.er.usgs.gov/staffpages/csherwood/sedx_equations/RunSedCalcs.html
Google: Sherwood USGS
+ other Sediment transport applets
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activate sediment and bbl
activate sediment
cppdefs.h
activate bbl
activate source of wave data
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specify input file and output parameters
activate output
ocean.in
identify name ofsediment.in file
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sediment.in example input file
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Establish sediment parameters
set grid size
mod_param.F
set :number of bed layersnumber of cohesive
sediment classesnumber of non-cohesive
sediment classes
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Initialize sediment arrays
bed(i,j,k, MBEDP)
bed_frac(i,j,k, ised)
bed_mass(i,j,k, ised)
bottom(i,j, MBOTP)
ana_sediment
ithck = 1 ! layer thicknessiaged = 2 ! layer ageiporo = 3 ! layer porosityidiff = 4 ! layer bio-diffusivity
isd50 = 1 ! mean grain diameteridens = 2 ! mean grain densityiwsed = 3 ! mean settle velocityitauc = 4 ! critical erosion stressirlen = 5 ! ripple lengthirhgt = 6 ! ripple heightibwav = 7 ! wave excursion amplitudeizdef = 8 ! default bottom roughnessizapp = 9 ! apparent bottom roughnessizNik = 10 ! Nikuradse bottom roughnessizbio = 11 ! biological bottom roughnessizbfm = 12 ! bed form bottom roughnessizbld = 13 ! bed load bottom roughnessizwbl = 14 ! wave bottom roughnessiactv = 15 ! active layer thicknessishgt = 16 ! saltation height
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Modeling of sediment transport in Mass Bay
Justification:• Relocation of Boston sewage outfall
(Sept 2000) • Habitats – fisheriesPurpose• simulate tidal currents and transport of
sediment due to combined tides and storm forcing
• determine transport pathways of sediment in Mass Bay (relative contribution of storms, tides, etc)
• test of numerical transport algorithms, bed model
Methods• Conduct 70 day simulation of currents
and sediment transport, driven by tides and 6 repeating storm events
Butman, Valentinehttp://woodshole.er.usgs.gov/project-pages/coastal_mass/html/intro.html
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20 vertical sigma layers68x68 horizontal orthogonal curvilinear
Grid
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Storm forcing
Use pattern of October 1996 event
To reperesent a “typical” storm
Repetition of October 1996 eventto simulate 6 storms
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SWAN output at peak of storm
SWAN inputs:
27 deg
Wind 15 m/s
Swell 6m, 11s
Boston buoy
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Mass Bay– Tides + Storm
initial evendistribution of
5 sediment classes:2, 3, 4, 5, and 6 phi
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Comparison of Observed – Model surficial sediment distribution
Modelled Observed
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Issues with negative sediment
TS_U3HADVECTION MPDATA-Positive definite
Simulation of river sediment dispersal on shelf
EAST_WALLWEST_WALLNS_PERIODICsvstr = -0.05 N/m2
west Qsource = 500 m3/swest Tsource = 1kg/m3
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Summary
Recent advancements to the model:
• Multiple two-equation turbulence closure schemes (GLS, Umlauf and
Burchard 2003)
• Sediment transport algorithms
- suspended sediment transport
- bed framework
- transport multiple grain sizes
• Interaction between sediment and wave/current modules
- Styles/Glenn (sg_bbl.F) – existing
- Soulsby (mb_bbl.F) – (Blaas, UCLA)
• MPDATA positive definite horizontal advection scheme
• Tidal elevation only boundary condition
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Conclusions• ROMS has many options for turbulence closure:
Analytical, BVF, KPP, MY25, GLS
• GLS method provides a canonical form to both recover existing models and to develop new models.
• Performance of GLS reveals:
– Model correctly simulates the bulk response of Hudson River estuary (L, strat, and ds/dx) to tidal spring/neap and fresh water inflow variations
– Model simulates the overall stratification well, but the vertical structure is more diffuse (mixed) in the model.
– 3 turbulence closures of k-, k-, and k-kl produce consistent results for salt transport
• Performance of sediment routines qualitatively reproduce observed surficial sediment distribution
• MPDATA advection ensures positivity of tracer values, but is less accurate.
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Future directions• Turbulence closures :
– continue evaluations /comparisons– compare to LES simulations
• Sediment transport :– suspended-sediment stratification effects in wave bl.– mixed grain bed mechanics (cohesive v. non-cohesive)– gravity-driven transport in bbl– aggregation / dissaggregation– wetting / drying– bioturbation in sediment layers– bedload transport (with wave effects)– radiation stresses– one layer BBL module
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arrivederci !