2D numerical study of circular synthetic jets in quiescent flows

Abstract

2D numerical simulations of flows generated by a synthetic jet actuator with a circular orifice were conducted at two different diaphragm displacement settings, one representing a typical laminar case and the other a fully turbulent case. The flow in the cavity was included in the computation in order to provide more accurate predictions. A velocity boundary condition was applied at the neutral position of the diaphragm to account for its temporal deformation. Comparisons were made between the computational results and existing PIV and hot-wire data in terms of the time sequence of the velocity vector field, velocity variations in space and with time. It is found that computational results for the laminar case agree well with the experimental data. Four turbulent models were tested for the fully turbulent case. It was found that the predictions using the RNG κ-ε and Standard κ-ε models were reasonably close to the experimental data. This initial study has produced some encouraging evidence for the capacity of FLUENT in simulating the key features of synthetic jets. THE AERONAUTICAL JOURNAL FEBRUARY 2005 89 Paper No. 2938. Manuscript NOMENCLATURE

Towards the Design of Synthetic-jet Actuators for Full-scale Flight Conditions

“…The timestep used for the simulations is T/80. A sensitivity study undertaken previously showed that the choices of mesh size and time-step used in the present study are adequate [9].…”

“…The capability of Fluent in simulating both laminar and turbulent flows of circular synthetic jets in quiescent conditions has been validated using PIV results [9]. According to the experimental observation, the initial vortex rings and near-field flows of all the selected cases to be presented here are laminar.…”

“…To account for the compressibility in the actuator cavity, the compressible flow model is used in the simulation unless specified otherwise. Further details about the simulations can be found in reference [9]. The DI model aims at establishing the relationships between the actuator performance parameters and the operating conditions for actuators in which the flow can be treated as incompressible.…”

“…Equations (7)(8)(9)(10)(11)(12)(13)(14) can be used to calculate the performance parameters for a given actuator geometric and operating condition. Note that the effect of orifice depth and cavity depth is not included in this model because of the incompressible flow assumption.…”

“…Hence although (7)(8)(9)(10)(11)(12)(13)(14)(15)17) become invalid for actuators in which the flow is compressible, the linear relationships given in (18a, b, c, d) still appear to hold [14] as shown in Fig. 4.…”