Synthetic jets are generated by an equivalent inflow and outflow of fluid into a system. Even though such a jet creates no net mass flux, net positive momentum can be produced because the outflow momentum during the first half of the cycle is contained primarily in a vigorous vortex pair created at the orifice edges whereas in the backstroke, the backflow momentum is weaker, despite the fact that mass is conserved. As a consequence of this, the approach can be potentially utilized for the impingement of a cooling fluid over a heated surface. In the present study, a canonical geometry is presented, in order to study the flow and heat transfer of a purely oscillatory jet that is not influenced by the manner in which it is produced. The unsteady Navier-Stokes equations and the convection-diffusion equation were solved using a fully unsteady, two-dimensional finite volume approach in order to capture the complex time dependent flow field. A detailed analysis was performed on the correlation between the complex velocity field and the observed wall heat transfer. A fundamental frequency, in addition to the jet forcing frequency, was found, and was attributed to the coalescence of consecutive vortex pairs. In some instances, this vortex pairing can lead to zones of low heat transfer. Two point correlations showed that the Nusselt number Nu, showed stronger correlation with the vertical velocity v although the spatial-temporal dependencies are not yet fully understood. It was found that the Reynolds number and the Strouhal number, are sufficient to successfully scale the problem at larger dimensions and this is presently being exploited in order to design validation experiments using jets large enough to allow careful local measurements.
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Numerical Simulation of Local Heat Transfer and Scaling of a Synthetic Impinging Jet in a Canonical Geometry
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Silva, L, & Ortega, A. "Numerical Simulation of Local Heat Transfer and Scaling of a Synthetic Impinging Jet in a Canonical Geometry." Proceedings of the ASME 2011 Pacific Rim Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Systems. ASME 2011 Pacific Rim Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Systems, MEMS and NEMS: Volume 2. Portland, Oregon, USA. July 6–8, 2011. pp. 113-121. ASME. https://doi.org/10.1115/IPACK2011-52053
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