Pulsating and Synthetic Impinging Jets

Article type: Research Article

Authors: Tesař, V. | Trávníček, Z.

Affiliations: Process Fluidics Group, Department of Chemical and Process Engineering, The University of Sheffield, Mappin Str., Sheffield S1 3JD, United Kingdom. E-mail: v.tesar@sheffield.ac.uk | Institute of Thermomechanics, Academy of Sciences of the Czech Republic, Dolejškova 5, 182 00 Prague 8, Czech Republic

Abstract: This is the second part of a survey summarizing authors' research over a period of two decades on enhancing impinging jet heat and/or mass transfer by periodic unsteadiness of nozzle flow rate. The first part, Tesař and Trávníček (2004 b), identified the reasons why pulsation does not always improve the transfer rate: the pulses do not reach up to the wall. The authors nevertheless demonstrate a transfer rate improvement, but in flows with inherent instability found in annular impinging jet. The excitation there causes a topological metamorphosis (reversal of flow character). Also in the extreme case of the synthetic (zero time-mean flow) jets the authors demonstrated a substantial improvement with the annular nozzle. The new approaches presented in the paper offer increased performance of drying and heating/cooling systems, in particular in microdevices with otherwise low or absent levels of natural jet turbulence.

Keywords: Visualization, Unsteady jets, Periodic jet flows, Synthetic jets

Journal: Journal of Visualization, vol. 8, no. 3, pp. 201-208, 2005