Mixing enhancement in 3D MHD channel flow by boundary electrical potential actuation

An electrically conductive fluid flowing inside a channel is prone to be affected by enormous magnetohydrodynamics (MHD) effects when the fluid interacts with an imposed magnetic field. Such effects often leads to higher pressure drop and lower heat transfer rate due to laminarization. Active boundary control, in either open loop or closed loop, can be used to enhance mixing and potentially increase heat transfer rate. Open-loop controllers are in general more sensitive to uncertainties of the system, which may result in a poorer performance. A closed-loop controller is proposed based on the linearized simplified magnetohydronamic (LSMHD) model. Micro pressure sensors and electrodes are embedded into the walls for measurement and actuation. Using the boundary vorticity flux as the input, the proposed feedback controller regulates the boundary electric potential at the channel walls in order to increase turbulence and mixing. By reversing the sign of a feedback controller designed to stabilize the LSMHD systems, a destabilizing controllers is achieved and used to excite multiple Fourier modes in simulations. The simulation results provided by a 3D simplified magnetohydronamic (SMHD) simulator show that the reversed controller successfully increases the turbulence inside an otherwise strongly stable MHD flow.