Coherent structures in turbulent boundary layers with adverse pressure gradients = 역압력구배가 있는 난류 경계층의 응집구조

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Coherent structures of turbulent boundary layers (TBLs) subjected to adverse pressure gradients (APGs) were scrutinized by analyzing the database of direct numerical simulations. Equilibrium adverse pressure gradient flows were established by using a power law free-stream distribution. A ZPG flow was also examined for comparison. Population trends of spanwise vortices in APG TBLs showed that hairpin-like vortices are densely populated in the outer region of APG TBLs. These vortical structures induce low-momentum regions in the middle of the boundary layer which lead to the outer peak of the Reynolds shear stress. Wall-normal spatial characteristics of hairpin packets were investigated in the spanwise-wall-normal plane to examine three-dimensional features of the hairpin packets. Conditionally averaged velocity fields showed that there are counter rotating v-w swirling motions which represent cross-sectional evidences of the packets. Moreover, two-point correlations and linear stochastic estimations were employed to provide statistical evidence of the hairpin packet motions in the cross-stream plane of APG TBLs.
Advisors
Sung, Hyung-Jinresearcher성형진researcher
Description
한국과학기술원 : 기계공학전공,
Publisher
한국과학기술원
Issue Date
2010
Identifier
418949/325007  / 020083421
Language
eng
Description

학위논문(석사) - 한국과학기술원 : 기계공학전공, 2010.2, [ v, 46 p. ]

Keywords

population trends of spanwise vortices; turbulent boundary layer (TBL); adverse pressure gradient (APG); coherent structure; 응집구조; 밀집 경향; 난류경계층; 역압력구배

URI
http://hdl.handle.net/10203/45785
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=418949&flag=dissertation
Appears in Collection
ME-Theses_Master(석사논문)
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