Growth rate of azimuthal perturbation modes in an ideal annular linear induction pump

Abstract

This study is aimed at investigating the growth rate of azimuthal perturbation modes in an ideal annular linear induction pump model. The positive growth rate of azimuthal perturbation modes is associated with the unstable behaviour of the annular linear induction pump and is known in the literature as MHD instability characterized by strong low-frequency oscillations of magnetic field, flowrate, and pressure. A linear stability analysis of a height-averaged quasi-stationary main flow in the ideal annular linear induction pump has been conducted, where only temporally evolving azimuthal modes of the axial velocity and magnetic field perturbations were considered. The obtained results predict damped or damped oscillating perturbations in a stable regime as a function of Rm, Rms, N and κm. In the studied parameter range, an amplification of perturbations without oscillations was observed above the instability threshold. It can be concluded that the analysed model of the ideal annular linear induction pump cannot predict experimentally and numerically the observed low frequency oscillations. Figs 4, Refs 17.