Numerical Simulation of Microscale Ionic Wind for Local Cooling Enhancement

Microscale ionic wind is a method of generating local boundary layer distortion to enhance convective heat transfer. An extension of the microscale ion driven airflow (MIDAF) concept, microscale ionic wind exerts a body force on an existing bulk flow through the phenomenon of ion drag. Ion drag results from repeated collisions between positive or negative ions with neutral air molecules. The ion-induced body force facilitates local boundary layer distortion analogous to the well-known active techniques of suction or blowing, and passive techniques such as surface protrusions. The reported method of ion and ionic wind generation utilizes emerging nanoscale electrode materials and micro-fabricated electrodes for electron field emission. The advantage of microscale geometries is that both the operating voltage (< 100V) and electrode spacing (< 100 mum) are small. A two-dimensional numerical model of the electrohydrodynamics predicts the behavior of the microscale ionic wind. The model solves steady-state continuity, momentum, and energy equations together with ion transport and electric potential equations. The model describes two electrodes on a flat plate and a superimposed bulk flow. Results reveal an improvement in local heat transfer coefficient of approximately 50% as compared to undisturbed boundary-layer flow