流体力学セミナー

皆様、6/26日(月)の流体力学セミナーを御案内いたします。
御来聴歓迎いたします。

日時:2016年 6月 26日(月) 15:00 から 16:30

場所: 京都大学 数理解析研究所 204号室

講師: Prof. Tamer A. Zaki
(Mechanical Engineering, Johns Hopkins University)

講演題目:
LARGE-SCALE STRUCTURES IN TRANSITIONAL AND TURBULENT BOUNDARY LAYERS

講演要旨:
In transitional and turbulent boundary layers, an interface separates
the non-turbulent and turbulent regions of the flow. In the transition
zone, this interface surrounds localized patches of turbulence that
are formed sporadically and spread to consume the surrounding laminar
flow. In the turbulent regime, the interface marks the free-stream
edge of the boundary layer and separates the vortical near-wall motion
from the outer potential flow. Using direct numerical simulations, we
examine characteristics of this turbulent/non-turbulent (T/NT)
interface. In the case of transition we relate its formation, or the
inception of turbulence patches, to the streaky structures known as
Klebanoff distortions. In the fully turbulent boundary layer,
statistical evidence is presented that the interface is locally
modulated by the large-scale velocity perturbations in both the
streamwise and spanwise directions. The modulation is different when
the coherent structure is high- versus low-speed motion: high-speed
structures lead to a wedgeshaped deformation of the T/NT interface,
which causes an anti-correlation between the angles of the interface
and the internal shear layer. On the other hand, low-speed structures
are correlated with crests in the interface. Finally, the sudden
changes in turbulence statistics across the interface are in line with
the changes in the population of low-speed structures, which consist
of slower mean streamwise velocity and stronger turbulence than the
high-speed counterparts.

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世話人:山田 道夫(京大数理研), 竹広 真一(京大数理研),
    藤 定義(京大),松本 剛(京大理)
アドバイザー:水島 二郎(同志社大工), 余田 成男(京大理)
連絡先:山田道夫 yamada_at_kurims.kyoto-u.ac.jp
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