#### Spanwise behavior of large-scale motions in turbulent minimal pipe flow = 미니멀 파이프 유동 내 대형 구조의 횡 방향 거동 특성

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Direct numerical simulation data from a turbulent minimal pipe flow is used to explore the spanwise behavior of large-scale motions (LSMs) at $Re_{\tau}$ = 927, 1990, and 2916. A streamwise-minimal unit with a streamwise domain length ($L_x^{+}$ = 1000) is chosen to extract the spanwise behavior of LSMs effectively, and the minimal simulation exhibits well-established spanwise organization of LSMs. The important spanwise behaviors in high Reynolds number turbulent pipe flow are the self-similarity of energy-containing motions and two outer peaks in pre-multiplied spanwise energy spectra of streamwise velocity fluctuations (u). In this present study, we observed that these behaviors are mainly arisen from the wall-attached structures. The conditional two-point correlation represents that the outer peaks in energy spectra are strongly related with attached structures. In particular, the reconstructed pre-multiplied spanwise energy spectra of $u^{2D}$, which is the time evolution of streamwise-averaged u, showed that the two outer peaks are mainly contributed by the tall and wide attached $u_{2D}$ structures ($l_y$ > 0.2). The spanwise scales of attached $u^{2D}$ structures reveal a linear growth with respect to the distance from the wall, which supports the self-similar behavior of energy-containing motions. In addition, the enhanced attached u structures have strong connection with the near-wall region, affecting the spanwise movement of near-wall structures and the near-wall turbulent kinetic energy; the top-down influence of LSMs.
Sung, Hyung Jinresearcher성형진researcher
Description
한국과학기술원 :기계공학과,
Publisher
한국과학기술원
Issue Date
2019
Identifier
325007
Language
eng
Description

학위논문(석사) - 한국과학기술원 : 기계공학과, 2019.2,[iv, 30 p. :]

Keywords

Direct numerical simulation▼aturbulent pipe flow▼alarge-scale motions▼aspanwise behavior; 직접수치모사▼a난류 파이프 유동▼a대형 구조▼a횡 방향 거동 특성

URI
http://hdl.handle.net/10203/265881