Large-scale motions in turbulent pipe flow = 난류 파이프 유동 내 대형 구조에 관한 연구

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Direct numerical simulations (DNSs) of turbulent pipe flow at $Re_\tau$ = 180, 544, 934 and 3008 were performed. The range of the present Reynolds numbers covered being from low to high turbulent flow. $Re_\tau$ = 3008 became the highest Reynolds number in the area of pipe DNSs, which can provide clear comparison with the previous experimental studies and resolve the several controversial issues so far. Scale separation, one of the prominent features in high Reynolds number, was examined and interpreted in the perspective of turbulence structures. Scale separation between SSM and LSM (& VLSM) was achieved due to the occurrence of the strong outer energy from VLSM, whereas the power law occurred instead of the log law in the overlap layer, implying that the scale separation between the inner and outer length scales was not achieved. The contribution of the LSM was not strong enough to show the constant-stress layer in the Reynolds shear stress, which was related to the log law. LSM and VLSM, which played a significant role in the scaling, grew linearly in the statistical manner. The linearly growing behavior was consistent to the helical angles of the energetic proper orthogonal decomposition (POD) modes. The present DNS data and results could be significant in revealing the unknown nature of turbulence.
Advisors
Sung, Hyung Jinresearcher성형진researcher
Description
한국과학기술원 :기계공학과,
Publisher
한국과학기술원
Issue Date
2017
Identifier
325007
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 기계공학과, 2017.2,[vii, 88 p. :]

Keywords

direct numerical simulation; turbulent pipe flow; turbulent boundary layer; turbulence structure; large-scale motion; scale separation; 직접수치모사; 난류 파이프 유동; 난류 경계층; 난류 구조; 대형 구조; 스케일 분리

URI
http://hdl.handle.net/10203/241683
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=675638&flag=dissertation
Appears in Collection
ME-Theses_Ph.D.(박사논문)
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