TY - JOUR
T1 - Marginally turbulent flow in a square duct
AU - Uhlmann, Markus
AU - Pinelli, Alfredo
AU - Kawahara, Genta
AU - Sekimoto, Atsushi
N1 - Funding Information:
Collaboration between the two groups was supported by the Center of Excellence for Research and Education on Complex Functional Mechanical Systems (COE program of the Ministry of Education, Culture, Sport, Science, and Technology of Japan). M.U. was supported by the Spanish Ministry of Education and Science under contract DPI-2002-040550-C07-04. G.K. was partially supported by a Grant-in-Aid for Scientific Research (B) from the Japanese Society for the Promotion of Science.
PY - 2007/10/10
Y1 - 2007/10/10
N2 - 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.
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.
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U2 - 10.1017/S0022112007007604
DO - 10.1017/S0022112007007604
M3 - Article
AN - SCOPUS:37749030468
SN - 0022-1120
VL - 588
SP - 153
EP - 162
JO - Journal of Fluid Mechanics
JF - Journal of Fluid Mechanics
ER -