Thermal control of electronic devices has been an active research area of heat transfer technologies. The impetus is straightforward: decreasing the temperature of a component increases its performance as well as its reliability. In the present study, a single microchip is placed in a 2D channel. A simple triangular cavity configuration is used to investigate the effectiveness of a synthetic jet for its thermal management. The study presents altered main channel flow results for various synthetic jet configurations and different membrane oscillation frequencies. The effect is that synthetic jet enhances mixing by imparting momentum to the channel flow thus manipulating the temperature field in a positive manner. Computations carried out for both continuum and slip flow regimes.

A computational analysis and design methodology is presented for effective microflow control using synthetic jets. The membrane is modeled as a moving boundary to accurately compute the flow inside the jet cavity. Compressible Navier-Stokes equations are solved with boundary conditions for the wall slip and the temperature jump conditions encountered for a specific range of Knudsen numbers. For validation, microchannel flow and microfilter flow are successfully computed. Then, flow past a backward-facing step in a microchannel is considered. Analysis is coupled with a design methodology to improve the actuator effectiveness. The objective function is selected to be the square of the vorticity (enstrophy) integrated over a separated region. First, from a design of experiments study, orifice and actuator cavity widths are identified as the most effective design variables. Then, a response surface method is constructed to find the improved control of the flow. This optimization results in more than 83% reduction of the enstrophy of the recirculation region.

A key concern for micro device design is its power consumption. When such a device involves microflows, actively controlling the flow losses often reduces the power requirements. In the present study, a micro synthetic jet is proposed as a flow control device. The method used is an automated design optimization methodology coupled with computational fluid dynamics. Microflows in the Knudsen range of 10−3 to 10−1 are modeled using a Navier-Stokes solver but with slip velocity and temperature jump boundary conditions derived for micro-sized geometries. First, an uncontrolled flow past a backward facing step in a channel is computed. Then, a synthetic jet actuator is placed downstream of the step where the separation occurs. A large number of test cases have been analyzed. It has been observed that the reattachment point of the separated flow and the flow dissipation are quite sensitive to the location and the geometry of the synthetic jet as well as the parameters of the oscillating membrane. The best flow control, defined as the largest decrease in dissipation, is obtained when the actuator cavity width and the membrane oscillation amplitude are increased simultaneously.

Flow field generated in and around micro synthetic jet actuator is analyzed using the an existing Navier-Stokes solver.The solver is modified to accomodate slip wall boundary condition proposed in literature for micro scale flow problems. Two actuator cavity shapes, rectangular and triangular, are investigated for quiscent and cross-flow external domain conditions.

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