Abstract: The stability of conducting fluid flow in ducts under magnetic field is vital to materials preparation and the design and operation of thermonuclear fusion cooling system. A model of MHD duct flow which is known as Hunt’s flow is simulated by non-normal mode stability analysis in this study^.. The amplification and distribution of optimal primary perturbations are obtained by solving iteratively the direct and adjoint governing equations with respect of the perturbation variables. Four modes of perturbations with different symmetries in the space are considered, and the effect of the low-intensity magnetic field is also taken into account. The results show that, when the Hartmann number Ha is small, the perturbations in the form of different modes exhibit transient growth. By contrast, when Ha is large, these perturbations behave differently: the perturbations in the form of mode I, III and IV grow transiently; the perturbations of mode II grows exponentially, meanwhile, the flow stability is related to jets.

Key words: Hunt's flow, stability, non-normal mode, transient growth, exponential growth