TY - JOUR
T1 - Mechanism of drag reduction by pre-determined spatio-temporally periodic control of wall turbulence
AU - Yakeno, Aiko
AU - Hasegawa, Yosuke
AU - Kasagi, Nobuhide
N1 - Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 2010/4
Y1 - 2010/4
N2 - We evaluate pre-determined controls with temporally- and spatially-periodic spanwise velocity inputs at the wall in a fully developed turbulent channel flow. The spatially-periodic control generally achieves better performance than the temporally-periodic one, which is conventionally called the spanwise wall-oscillation control. Particular attention is paid to the Reynolds stress, which dominates the skin friction. We apply a conditional sampling technique in order to clarify the response of the Reynolds stress around a particular rotation direction of a longitudinal vortex to the spanwise control input. Quadrant analysis of the Reynolds stress shows that the phase-dependencies of Q2 and Q4 events around a longitudinal vortex are totally different. Based on this knowledge, the drag reduction mechanisms in the two controls are discussed.
AB - We evaluate pre-determined controls with temporally- and spatially-periodic spanwise velocity inputs at the wall in a fully developed turbulent channel flow. The spatially-periodic control generally achieves better performance than the temporally-periodic one, which is conventionally called the spanwise wall-oscillation control. Particular attention is paid to the Reynolds stress, which dominates the skin friction. We apply a conditional sampling technique in order to clarify the response of the Reynolds stress around a particular rotation direction of a longitudinal vortex to the spanwise control input. Quadrant analysis of the Reynolds stress shows that the phase-dependencies of Q2 and Q4 events around a longitudinal vortex are totally different. Based on this knowledge, the drag reduction mechanisms in the two controls are discussed.
KW - Coherent structure
KW - Flow control
KW - Friction drag reduction
KW - Wall turbulence
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U2 - 10.1299/kikaib.76.764_555
DO - 10.1299/kikaib.76.764_555
M3 - Article
AN - SCOPUS:77954746084
VL - 76
SP - 555
EP - 562
JO - Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B
JF - Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B
SN - 0387-5016
IS - 764
ER -