TY - GEN

T1 - The effect of coherent structures on the secondary flow in a square duct

AU - Sekimoto, A.

AU - Pinelli, A.

AU - Uhlmann, M.

AU - Kawahara, G.

N1 - Publisher Copyright:
© 2009, Springer-Verlag Berlin Heidelberg.

PY - 2009

Y1 - 2009

N2 - The appearance of secondary flow of Prandtl’s second kind is a well-known phenomenon in fully developed turbulent rectangular duct flow. The intensity of the secondary flow is two orders of magnitude smaller than that of the mean streamwise velocity; however, it plays an important role in the crossstreamwise momentum, heat and mass transfer. Our recent study [1] revealed that the mean secondary flow is a statistical footprint of the turbulent flow structures, i.e. streamwise vortices and streaks which are observed in the nearwall region, whose cross-sectional positions are constrained by the presence of the side walls at marginal Reynolds number (approximately 1100, based on the bulk velocity and the duct half width, corresponding to a friction Reynolds number of about 80). In this marginal case, one low-speed streak associated with a pair of counter-rotating streamwise vortices can exist over each wall and they are self-sustained [2]. When considering the higher Reynolds numbers, the increment of duct width in wall unit allows the simultaneous presence of multiple low velocity streaks and pairs of streamwise vortices upon the wall.

AB - The appearance of secondary flow of Prandtl’s second kind is a well-known phenomenon in fully developed turbulent rectangular duct flow. The intensity of the secondary flow is two orders of magnitude smaller than that of the mean streamwise velocity; however, it plays an important role in the crossstreamwise momentum, heat and mass transfer. Our recent study [1] revealed that the mean secondary flow is a statistical footprint of the turbulent flow structures, i.e. streamwise vortices and streaks which are observed in the nearwall region, whose cross-sectional positions are constrained by the presence of the side walls at marginal Reynolds number (approximately 1100, based on the bulk velocity and the duct half width, corresponding to a friction Reynolds number of about 80). In this marginal case, one low-speed streak associated with a pair of counter-rotating streamwise vortices can exist over each wall and they are self-sustained [2]. When considering the higher Reynolds numbers, the increment of duct width in wall unit allows the simultaneous presence of multiple low velocity streaks and pairs of streamwise vortices upon the wall.

KW - Coherent Structure

KW - High Reynolds Number

KW - Reynolds Number

KW - Secondary Flow

KW - Wall Shear Stress

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U2 - 10.1007/978-3-642-03085-7_80

DO - 10.1007/978-3-642-03085-7_80

M3 - Conference contribution

AN - SCOPUS:84858424096

SN - 9783642030840

T3 - Springer Proceedings in Physics

SP - 329

EP - 332

BT - Advances in Turbulence XII - Proceedings of the 12th EUROMECH European Turbulence Conference, 2009

A2 - Eckhardt, Bruno

PB - Springer Science and Business Media Deutschland GmbH

T2 - 12th EUROMECH European Turbulence Conference, ETC12 2009

Y2 - 7 September 2009 through 10 September 2009

ER -