Direct numerical simulations of localized disturbances in pipe Poiseuille flow |
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Authors: | Per-Olov Å sé n,Gunilla Kreiss |
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Affiliation: | a Linné Flow Center, CSC, KTH, SE-100 44 Stockholm, Sweden b Department of Information Technology, Uppsala University, Box 120, S-751 04 Uppsala, Sweden c Illinois Institute of Technology, 243c Engineering1, 3110 South State Street, Chicago, IL 60616, USA |
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Abstract: | We consider pipe Poiseuille flow subjected to a disturbance which is highly localized in space. Experiments by Peixinho and Mullin have shown this disturbance to be efficient in triggering turbulence, yielding a threshold dependence on the required amplitude as R-1.5 on the Reynolds number, R. The experiments also indicate an initial formation of hairpin vortices, with each hairpin having a length of approximately one pipe radius, independent of the Reynolds number in the range of R=2000-3000. We perform direct numerical simulations for R=5000. The results show a packet of hairpin vortices traveling downstream, each having a length of approximately one pipe radius. The perturbation remains highly localized in space while being advected downstream for approximately 10 pipe diameters. Beyond that distance from the disturbance origin, the flow becomes severely disordered. |
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Keywords: | Direct numerical simulations Pipe Poiseuille flow Hydrodynamical stability Incompressible Navier-Stokes equations |
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