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Numerical study of a transitional synthetic jet in quiescent external flow


The flow associated with a synthetic jet transitioning to turbulence in an otherwise quiescent external flow is examined using time-accurate three-dimensional numerical simulations. The incompressible Navier–Stokes solver uses a second-order accurate scheme for spatial discretization and a second-order semi-implicit fractional step method for time integration. The simulations are designed to model the experiments of C. S. Yao et al. (Proc. NASA LaRC Workshop, 2004) which have examined, in detail, the external evolution of a transitional synthetic jet in quiescent flow. Although the jet Reynolds and Stokes numbers in the simulations match with the experiment, a number of simplifications have been made in the synthetic jet actuator model adopted in the current simulations. These include a simpler representation of the cavity and slot geometry and diaphragm placement. Despite this, a reasonably good match with the experiments is obtained in the core of the jet and this indicates that for these jets, matching of these key non-dimensional parameters is sufficient to capture the critical features of the external jet flow. The computed results are analysed further to gain insight into the dynamics of the external as well as internal flow. The results indicate that near the jet exit plane, the flow field is dominated by the formation of counter-rotating spanwise vortex pairs that break down owing to the rapid growth of spanwise instabilities and transition to turbulence a short distance from the slot. Detailed analyses of the unsteady characteristics of the flow inside the jet cavity and slot provide insights that to date have not been available from experiments.

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Q. Gallas , R. Holman , T. Nishida , B. Carroll , M. Sheplak & L. Cattafesta 2003 aLumped element modeling of piezoelectric-driven synthetic jet actuators. AIAA J. 41, 240247.

H.-J. Kaltenbach , M. Fatica , R. Mittal , T. S. Lund & P. Moin 1999 Study of flow in a planar asymmetric diffuser using large-eddy simulation. J. Fluid Mech. 390, 151186.

C. Loudon & A. Tordesillas 1998 The use of the dimensionless Womersley number to characterize the unsteady nature of internal flow. J. Theor. Biol. 191, 6378.

R. Mittal 2000 Response of the sphere wake to freestream fluctuations. Theoret. Comput. Fluid Dyn. 13, 397419.

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Journal of Fluid Mechanics
  • ISSN: 0022-1120
  • EISSN: 1469-7645
  • URL: /core/journals/journal-of-fluid-mechanics
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