Influence of high-permeability discs in an axisymmetric model of the Cadarache dynamo experiment
Influence of high-permeability discs in an axisymmetric model of the Cadarache dynamo experiment
复制标题
高渗透性圆盘对 Cadarache 发电机实验轴对称模型的影响
DOI：
10.1088/1367-2630/14/5/053005
复制
发表时间：
2011
影响因子：
3.3
通讯作者：
J. Guermond
中科院分区：
文献类型：
--
作者：
A. Giesecke;C. Nore;C. Nore;F. Stefani;G. Gerbeth;J. L'eorat;W. Herreman;W. Herreman;F. Luddens;J. Guermond;J. Guermond
Numerical simulations of the kinematic induction equation are performed on a model configuration of the Cadarache von-Kármán-sodium dynamo experiment. The effect of a localized axisymmetric distribution of relative permeability μr that represents soft iron material within the conducting fluid flow is investigated. The critical magnetic Reynolds number Rmc for dynamo action of the first non-axisymmetric mode roughly scales like Rmcμr − Rmc∞∝μ−1/2r, i.e. the threshold decreases as μr increases. This scaling law suggests a skin effect mechanism in the soft iron discs. More important with regard to the Cadarache dynamo experiment, we observe a purely toroidal axisymmetric mode localized in the high-permeability discs which becomes dominant for large μr. In this limit, the toroidal mode is close to the onset of dynamo action with a (negative) growth rate that is rather independent of the magnetic Reynolds number. We qualitatively explain this effect by paramagnetic pumping at the fluid/disc interface and propose a simplified model that quantitatively reproduces numerical results. The crucial role of the high-permeability discs in the mode selection in the Cadarache dynamo experiment cannot be inferred from computations using idealized pseudo-vacuum boundary conditions (H × n = 0).
