H Sarlak Chivaee JN Sørensen RF Mik H. Sarlak Chivaee

Large
g Eddy
y Simulation of Fully
y Developed
p
Wind
T bi
Turbine
B
Boundary
d
L
Layer
H Sarlak Chivaee
H.
Chivaee,, J
J. N
N. Sørensen,
Sørensen, R.
R F.
F Mikkelsen
1 Motivation:
1.
Department of Wind Energy, Technical University of
Denmark 2800 Kgs.
Denmark,
Kgs Lyngby,
Lyngby Denmark
Denmark.
{h
{hsar,
j
jns,rm}
} @ mek.dtu.dk
k dt dk
2 Definitions and Mathematical Modeling
2.
• Fast
as modeling
ode g o
of wind
d turbine
u b e wakes
a es in shear
s ea
flows using prescribed boundary layer technique
• Modeling in deferent atmospheric boundary
layer regimes
• Test performance of different sub-grid scale
models
d l
2.1. Actuatorr disc ((AD)) model of wind turbines
AD Pros
P
:
• Low computatio
onal cost
• Works with sim
mple structured grids
• Suitable for larg
g
ge wind farm simulation
AD Cons:
• Simulation
Si l ti ressults
lt are based
b
d on input
i
t airfoil
i f il data
d t
AD modeling s
strategy:
• Obtain flow fielld from the CFD solver
• Find the forcess on airfoil sections based on the velocityy field
• Integrate and in
nterpolate the forces back to the
t ti
l do
domain
i
computational
Wake Effects in Horns Rev Wind Farm
2 2 Governin
2.2.
G
ing
g equations
q ti
for
f fluid
fl id
Right: Stable –vsvs
Convective (unstable)
ABL velocity
yp
profiles
(Wyngaard,
(Wyngaard 2010):
Bottom: Diurnal ABL
Cycle (Stoll 1988)
2.3. SGS mod
deling
4 different mode
els are tested,
tested ii.e.
e the implicit
LES,, the standard Smagorinsky,
g
y, and two
variants of the mixxed scale model based on
(S
(Sagaut
t 1995) and
d (T
(Ta Phouc
Ph
1994) See
1994).
S
Table to the right:
3 Results
3.
4 Conclusions
4.
Domain Comparison1
1 AD,, 750 x 1500 x 750 m
ABL Comparison
SGS Co
omparison
4 AD, 3000 x 1500 x 750 m
W [m/s] :
•PBL
PBL method offers significant computational cost saving
while giving
g g acceptable
p
estimates of the flow structures at
different atmospheric boundary layer regimes.
regimes It can be
used
d for
f wind
i d turbine
t bi model
d l evaluations
l ti
iin the
th sheared
h
d
flow.
flow
•Some of the statistics,, however,, might
g be q
questionable
especially close to the wall since the effects of roughness
are nott modeled
d l d in
i a physically
h i ll consistent
i t t way.
Furthermore, so-called
so called low-level
low level jet cannot be seen in
SBL.
SBL
WWrms [N/m2]:
VWrms [N/m2]:
•The
The domain sensitivity study shows that having a small
d
domain
i iin the
th streamwise
t
i direction
di ti lilimits
it the
th llargestt
structures in the flow to the domain size and at least a
domain with the streamwise direction twice as large as the
h ight should
height
h ld b
be employed.
pl y d L
Large
g structures
t t
can be
b
clearly seen in the figures to the left.
left
• In terms of the SGS modeling
g all models are able to
predict a similar trend in the flow field in the average
sense.
-----------------------------1- ((x,y,z)
y ) coordinates ((and corresponding
p
g velocity
y components
p
u,v,w)) are along
g spanwise,
p
wall normal and the streamwise
components.
References: [1] J Wyngaard,
Wyngaard Turbulence in theAtmosphere,
theAtmosphere 2010.
2010 [2] R Stull,An
Stull An intro.
intro To Boundary Layer Meteorology,1998.
Meteorology1998