In this paper the flow field of a rectangular synthetic jet driven by a piezoelectric membrane issuing into a quiescent environment is studied. The similarities exhibited by synthetic and continuous turbulent jets lead to the hypothesis that a rectangular synthetic jet within a limited region downstream of the orifice be modeled using similarity analysis just as a continuous planar jet. Accordingly, the jet is modeled using the classic two-dimensional solution to a continuous jet, where the virtual viscosity coefficient of the continuous turbulent jet is replaced with that measured for a synthetic jet. The virtual viscosity of the synthetic jet at a particular axial location is related to the spreading rate and velocity decay rate of the jet. Hot-wire anemometry is used to characterize the flow downstream of the orifice. The flow field of rectangular synthetic jets is thought to consist of four regions as distinguished by the centerline velocity decay. The regions are the developing, the quasi-two-dimensional, the transitional, and the axisymmetric regions. It is in the quasi-two-dimensional region that the planar model applies, and where indeed the jet exhibits self-similar behavior as distinguished by the collapse of the lateral time average velocity profiles when scaled. Furthermore, within this region the spanwise velocity profiles display a saddleback profile that is attributed to the secondary flow generated at the smaller edges of the rectangular orifice. The scaled spreading and decay rates are seen to increase with stroke ratio and be independent of Reynolds number. However, the geometry of the actuator is seen to additionally affect the external characteristics of the jet. The eddy viscosities of the synthetic jets under consideration are shown to be larger than equivalent continuous turbulent jets. This enhanced eddy viscosity is attributed to the additional mixing brought about by the introduction of the periodic vortical structures in synthetic jets and their ensuing break down and transition to turbulence. Further, a semi-empirical modeling approach is proposed, the final objective of which is to obtain a functional relationship between the parameters that describe the external flow field of the synthetic jet and the input operational parameters to the system.
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e-mail: mohseni@colorado.edu
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December 2009
Research Papers
An Experimental and Analytical Investigation of Rectangular Synthetic Jets
Gopi Krishnan,
Gopi Krishnan
Department of Aerospace Sciences,
University of Colorado
, Boulder, CO 80309-429
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Kamran Mohseni
Kamran Mohseni
Department of Aerospace Sciences,
e-mail: mohseni@colorado.edu
University of Colorado
, Boulder, CO 80309-429
Search for other works by this author on:
Gopi Krishnan
Department of Aerospace Sciences,
University of Colorado
, Boulder, CO 80309-429
Kamran Mohseni
Department of Aerospace Sciences,
University of Colorado
, Boulder, CO 80309-429e-mail: mohseni@colorado.edu
J. Fluids Eng. Dec 2009, 131(12): 121101 (11 pages)
Published Online: November 10, 2009
Article history
Received:
November 29, 2008
Revised:
September 25, 2009
Online:
November 10, 2009
Published:
November 10, 2009
Citation
Krishnan, G., and Mohseni, K. (November 10, 2009). "An Experimental and Analytical Investigation of Rectangular Synthetic Jets." ASME. J. Fluids Eng. December 2009; 131(12): 121101. https://doi.org/10.1115/1.4000422
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