Numerical and Experimental Studies of Low Reynolds Number Synthetic Jets

Lecturer: Dr. Victoria Timchenko, School of Mechanical and Manufacturing Engineering, The University of New South Wales, UNSW Sydney NSW 2052 Australia
Date: October 26, 2011 (Wednesday), 10:30-11:30
Location: Institute of Thermomechanics AS CR, v. v. i., Dolejškova 5, Prague, lecture room A

Dr. Timchenko is a senior lecturer at the School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, Australia. Her areas of expertise are computational fluid dynamics and heat transfer. Research interests include natural convection and phase change problems; solidification and melting processes under earth gravity and space microgravity conditions; cooling of building integrated photovoltaic systems and microelectronic devices; biomedical applications.

Since synthetic jets have high potential to increase mixing and heat transfer rates it is important to obtain a better understanding their formation and propagation at low Reynolds numbers for applications in micro or mini devices. In order to investigate the effects of synthetic jet interaction with cross flow in micro-channel for the cooling of microchips a three-dimensional computational model was developed. To account for the deflection of the membrane located at the bottom of the actuator cavity, a novel moving mesh algorithm to solve the flow and heat transfer has been adopted. To track the development of the flow and heat transfer when the actuator was switched on, numerical results of 40 full cycles of the actuator have been obtained. When the actuator was switched on, noticeable temperature drop was observed at all points in the substrate from those which existed when there has been a steady water flow in the channel. Also an experimental investigation of the flow field of a meso-scale synthetic jet in air was performed at the same Reynolds and Stokes numbers as those used in the numerical work on micro-scale devices. Excellent agreement between the experimental results and the numerically obtained data for the instantaneous position of the vortex core, in particular, and the flow field, in general, validated the numerical approach. Since such jets are likely to be used in the vicinity of a wall, the complex flows resulting from interaction between initially annular vortices generated by a circular synthetic jet and a nearby parallel wall have been studied.

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