Numerical and Experimental Studies of Low Reynolds Number Synthetic Jets

Přednáška
Prednášející: Dr. Victoria Timchenko, School of Mechanical and Manufacturing Engineering, The University of New South Wales, Australia
Datum: 26. října 2011 (středa),10.30–11.30
Místo: Ústav termomechaniky AV ČR, v. v. i., Dolejškova 5, Praha, zasedací místnost A

Dr. Timchenko přednáší na School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, Austrálie. Zabývá se výpočetní dynamikou tekutin (CFD), přenosem tepla, konkrétně přirozenou konvekcí a problémy fázové přeměny, dále procesy solidifikace a tavení v gravitačním poli země a v podmínkách vesmírné mikrogravitace, chlazením fotovoltaických systémů integrovaných v budovách a mikroelektronických zařízení a biomedicínskými aplikacemi.

Abstract:
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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