Atsushi YAMAGUCHI and Takeshi ISHIHARAThe University of Tokyo

Flow simulation around met mast

Objectives
In Fukushima Floating Offshore Wind Farm
Demonstration Project (Fukushima FOWarD),
wind speed measurement is carried out at amet mast located on the floating substation.
The structure member of this met mast tends
to be thicker compared to the usual onshoreor bottom mounted offshore met masts,
results in the violation of the condition
specified in the standards such as IEC6140012-1. This implies even if the met mast isequipped with multiple anemometers, simple
choice of anemometer depending on thewind direction1) cannot be used. Some studies
have been done on the flow simulation
around met mast 2) but there was novalidation of flow simulation.
In this study, first, flow simulation around themast is carried out and validated by using thethree anemometers located at the sameheight of the met mast. Then, the wind speed
which is not affected by the met mast is
estimated and results are compared with themeasured wind speed by doppler lidar.

Floating met mast at Fukushima• Three cup anemometers are installed ateach height, at No.12 flat, No.8 flat and No.
4 flat.
No. 12 flat

No. 8 flat

No. 4 flat

Plan of No.4flat

Standard k-e model was used for flow
simulation around the met mast. 16 winddirection with 22.5 direction intervals weresimulated.
Computation domain and grid
• Computational domain size:
10km x 10km x185m

From CFD simulation, the free wind speed
without met mast was estimated by dividing
the measured wind speed by using cup
anemometer by the wind seed ratio.

• Unstructure grid around the mast

1.2
1.1
10.9
0.80.7• Total number of grid:
10,000,000

0.6
0Computational
domainmodel ofthe metmast
180m

R=4,000m

10,000m• It was confirmed that the boundary layer ismaintained without met mast.

270

360

105

Lidarcup(before correction)cup(after correction)

2015/3/8

2015/3/8

Time series of thecorrected windspeed
Comparison of thecorrected windspeed and lidar
measurement• Mean wind speed profile with a=0.1 wasused as inflow.

180wind direction

15

10,000m

Inflow profile

90

200

2015/3/9

2015/3/10• Estimated free wind speed shows good
agreement with lidar.

70Ua=0.1Conclusions

No.12 Flat

60

No.8 Flat

50

In his study, flow simulation around floating
met mast was carried out to estimate the freeflow field. Following results were obtained.

No.4 Flat

40
30
20

Flow field without
met mast

100051015

20

2530

35

Flow simulation results and validation
LAcknowledgement

LF

This research is carried out as a part of a projectof Fukushima floating offshore wind farmdemonstration project (Fukushima FORWarD)
funded by the Ministry of Economy, Trade andIndustry (METI), Japan. The authors wish to express
their deepest gratitude to the concerned parties fortheir assistance during this study.

FRR

simulated wind speed field at No. 4 flat
Wind speedratio between
twoanemometers(F/R) at No. 4flat• Simulated wind speed ratio between twoanemometers shows good agreement withmeasurement.
• Estimated free flow field shows goodagreement wit lidar measurement.

2References

Measurement
CFD
1.5

10.5

Fukushima
floating
substation

F(front)
R(right)
L(left)1.3

wind speed ratio

Wind speed ratio ofeach anemometers
location to freewind speed.

1.4cup anemometer + CFD [m/s]Due to the restrictions of the structure designof the met mast on the floater, the effect of
met mast on the wind speed measurement isnot negligible. In this study, flow simulation
around the met mast of Fukushima FORWarD
is carried out to correct the effect of the met
mast. Simulated wind speed ratio between
two anemometers shows good agreementwith measurement. Estimated free flow fieldshows good agreement wit lidar
measurement.

Wind speed correction

wind speed [m/s]

Abstract

wind speed ratio

PO.036The effect of met mast on wind speed measurement
and its correction by using computational fluid dynamics

090180wind direction

270360• Simulated wind speed ratio between twoanemometers shows good agreement withmeasurement.

offshorewind2017.com#offshore2017

1.J.W. Wagenaar and P.J. Eecen, Measurements ofWind, Wave and Currents at the Offshore Wind
Farm Egmond aan Zee, ECN-E--09-015, 2009.
2.M. Stickland, T. Scanlon, S. Fabre, A. Oldroyd andD. Kindler, Measurement and Simulation of theFlow Field around a Triangular Lattice
Meteorological Mast, Journal of Energy and PowerEngineering (7) 1934-1939, 2013

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