Minimization of Poloidal Viscosity in Tokamaks Using the FLOW Code

Extensive experimental evidence shows that the inclusion of poloidal flow in tokamaks can dramatically improve transport properties. However, theory shows that these flows are damped by poloidal viscosity. In this work, we utilize the FORTRAN code FLOW [1] to calculate ideal magnetohydrodynamic (MHD) equilibria and estimate the poloidal viscosity with a postprocessor. We then minimize a norm of the viscosity over the input parameters of the calculation, i.e. the input free functions for FLOW, which are associated with intuitive physical quantities. In order to achieve this minimization, the FLOW code has first been functionalized and then wrapped within a Python script for easy use with an open source parallel minimization package. Here, we present and compare results of minimized poloidal viscosities for varying some or all of the FLOW input free functions as well as plasma shapes. We also compare our numerical results with an analytical minimization of the poloidal viscosity. [1] L. Guazzotto et. al., Physics of Plasmas, 11, 604 (2004).