RT Journal Article
T1 Marginally turbulent flow in a square duct
A1 Uhlmann, Markus
A1 Pinelli, Alfredo
A1 Kawahara, Genta
A1 Sekimoto, Atshushi
AB A direct numerical simulation of turbulent flow in a straight square duct was performed in order to determine the minimal requirements for self-sustaining turbulence. It was found that turbulence can be maintained for values of the bulk Reynolds number above approximately 1100, corresponding to a friction-velocity-based Reynolds number of 80. The minimum value for the streamwise period of the computational domain is around 190 wall units, roughly independently of the Reynolds number. We present a characterization of the flow state at marginal Reynolds numbers which substantially differs from the fully turbulent one: the marginal state exhibits a four-vortex secondary flow structure alternating in time whereas the fully turbulent one presents the usual eight-vortex pattern. It is shown that in the regime of marginal Reynolds numbers buffer-layer coherent structures play a crucial role in the appearance of secondary flow of Prandtl's second kind.
PB Cambridge University Press
SN 0022-1120
YR 2007
FD 2007
LK https://hdl.handle.net/20.500.14352/50708
UL https://hdl.handle.net/20.500.14352/50708
LA eng
DS Docta Complutense
RD 28 abr 2024