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| Marie, Louis; Normand, C; Daviaud, F. |
| We investigate dynamo action by solving the kinematic dynamo problem for velocity fields of the von Karman type between two coaxial counter-rotating propellers in a cylinder. A Galerkin method is implemented that takes advantage of the symmetries of the flow and their subsequent influence on the nature of the magnetic field at the dynamo threshold. Distinct modes of instability have been identified that differ by their spatial and temporal behaviors. Our calculations give the result that a stationary and antisymmetric mode prevails at the dynamo threshold. We then present a quantitative analysis of the results based on the parametric study of four interaction coefficients obtained by reduction of our initially large eigenvalue problem. We propose these... |
| Tipo: Text |
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| Ano: 2006 |
URL: https://archimer.ifremer.fr/doc/00253/36474/35014.pdf |
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| Marie, Louis; Daviaud, F. |
| We report measurements linking velocity fluctuations with the turbulent drag in a turbulent closed flow, namely the von Karman flow. Making use of the angular momentum balance equation in integral form, we obtain a simple expression for the torque applied by the forcing mechanism, which we check against quantitative laser Doppler velocimetry measurements. We then decompose the angular momentum flux into contributions coming from the different spectral components of the flow. We provide evidence of the fact that the turbulent drag is dominantly generated by coherent structures at the largest scales of the flow. (C) 2004 American Institute of Physics. |
| Tipo: Text |
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| Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/00254/36475/35019.pdf |
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