別紙41 (課程博士(英文))Date ofsubmission σanuary 61h,2023)

Akiyoshilida
Department ofMechanicalEngineenng

S加dentlD
Nulnber

D199103

Supervisors

Yuji Nakamura

HiroshiYokoyama
Applicant's name

Qidun Maulana Binu soesantoAbstract(Dodor)
Title ofThesis

Analysis a11d a11址y6Calmode1血g ofwake aerod沖ω〕証Cs be1血d hori加ntal・axis
WmdtTlrb血es

Approx.80o words

Ihe wake transition mechanisln behind an isolated non・ya、Ned horizontal、axis windturbine (HAい11T) has been investigated using a lo、V・cost analytical model. The wake itself isdefined as the region downsu'eam oft11e HA、NT identiaed by reduced wh)d speed. There are
two main regions within the wake aowfield behind the HA＼NT:(i) the near・wake region 6i)
the far・wake region. xvithin the near・、Nake region, tl〕e velocity pl'0負le resembles a double、

Ga11Ssian shape with tw010cal minima located around the blade midspan due to the suboptimal
Shape ofthe blade root and the effect of tip v01'tices at the blade tip. Meanwhile,圦/ithin thefar・、Nake region, the 、Nake is completely developed and fonηS a single‑Gaussian shape
distribution、 xvithin a fU11・wake region, it was clarified that the wake expands linearly in ananisotropic n)anner. AⅡ the mentioned wake characteristics are considered in the presentstudy
to modelthe wake transition mechanism within a fUⅡ・wake reσion of the HA圦11.1hePreliminary study was conducted to investigate the wake characteristics within the near、、Nakeregion using high・fidelity lm'ge eddy simulation (LES) data by finite element code

FrontFIOW/blue (FFB). R 、Nas clarified that the 、Nake 郡'061e could be approxilnated bybimodal distribution.1he 、Nake 、Nas found to recover faster in the lateral direction tl〕an in theVe11ical direction, thus confirn〕ing the anis0れ'opic manner ofthe wake expansion.1n addition,
it was observed that the 、Nake tends to expand linearly with the downstream distance behindthe HA圦IT.

Results in the prelimin釘'y study 、Nere considered in further work to propose an anisotropic
double、Gaussian wake model for predicting the wake transition mechanism within a fUⅡ・wakeregion behind the non、yawed HA圦,'T. The transition of the wake velocity from the double・
gaussian (DG) shape in the near・wake Ngion to the single・Gaussian (SG) shape in the far・
Wake region by considering the anisotropic 、Nake expansion has been successfUⅡy modeled.
The effectiveness of the proposed model was vaHdated using LEs resuHs and Hdar
measurements.1t was shown that the proposed model could give good agreement 、vith thebenchmark datasets.1n addition, the perfonnance ofthe proposed model was comPω'ed to theOther analytical models based on ule top・hat and single・Gaussian shapes.1n general, theProposed model has better P引formance than the other analytical models to predict the wake
Shape distribution, particularly within u〕e near・wake region 、Nhere the wake formed thedouble・Gaussian velocity profile.
Another work in this study intended to propose a linear wake expansion 会,1nction for the DG

analytical wake model.1he μ'oposed expansion 会.1nction forthe DG model was constructed fromSeveralexisting fonnulationsbased on the conselNation ofmass and momentum. By considering thePhysical and statistical approaches, a linear wake expansion 会.1nction was derived, thus a110wing its
direct usabiHw xvithout a prior adjustmenvtuning of the wake expansion parameter. The
effectiveness ofthe expa11Sion function was validated with the LEs and experimental measurement
results, and its perfonnance was also compared to the existing expansion alnction 圦lith tuning. R、¥as clarified both qualitatively and statistica11y thatthe proposed expansion 6.1nction could provide
reasonable estimations ofthe wake expansion 圦lithin 会.1Ⅱ・wake regions and had comparable results

With the tuned expansion 員.1nction.1hese results indicate the practicability of tl)e proposedexpansion function forthe DG wake modelto predictthe wake recovery within a 丘111・wake region
Ofthe 1玉へ圦IT. FUHhermore,the proposed expansion 6.1nction was also evaluated t0 皿'edict nlultゆleWakes behind three aHgned turbines.1n general, the result sho、Ns thatthe analytical prediction could
give a good agreement wi血 the benchmark dataset 介om high・fidelity LEs by FFB. This indicatesthe ability ofthe proposed expansion function to be used in predicting multゆle wakes behind the11Awls in addition to the sinσle wake cases.

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