Numerical Investigation of Dimensionless Numbers on Macro-scale Synthetic Jet Actuator in Quiescent Flow

Abstract

Synthetic jet is presently a novel technique for active flow control used for lift enhancement, improve boundary layer separation, and drag reduction, convective heat transfer enhancement and mixing enhancements. In this paper numerical simulation of macro-scale synthetic jet is carried out to investigate the effects of dimensionless numbers such as Stroke length (L), Stokes number (S) and Reynolds numbers (ReL) at constant orifice diameter of 5 mm. The computation is carried out by using commercial COMSOL Multiphysics 5.3a software for resolving the basic three dimensional incompressible unsteady Reynolds-averaged Navier-Stokes equations using k-turbulence model coupled with Moving Mesh ALE module to address the oscillating diaphragm movement. The oscillating diaphragm attached to the bottom of cavity is modelled as movable wall boundary in a sinusoidal manner with a peak-to peak displacement is equal to 0.247 mm at constant resonant frequency of 10 Hz. While the dimensionless Stroke length (L) ranges from 2 to 6, Stokes number S=7.2 to 22.9 and the Reynolds number establish on Stroke length ReL=11 to 1080 at distinct orifice diameters. Grid independence study has been invoked to confirm the authentication of extracted computational results. The radial velocity profiles at the orifice exit obtained in CFD simulations are compared with existing experimental data. A reasonable agreement between the modelling and experiment has been observed in specific domains of the flow field. The result obtained in the present study provides the basic design code for synthetic jet flow parameters for optimum output.

Current Review on Numerical Simulation of Synthetic Jet (SJ) Cooling

“…Dong et al, [54] has found that the primary clockwise vortex is favoured by low frequency and small amplitude, whereas the anticlockwise vortex is favoured by high frequency and large amplitude. Ahmad and Qayoum [55] has found that a SJ with a single orifice and a double orifice operates at its resonance frequency when its velocity reaches a maximum value to produce upward sweep vortices. The average HTC brought on by the double orifice SJ is 32% greater than the single orifice SJ at the resonance frequency and voltage.…”

“…An earlier attempt had been made to explore the SJ effect through numerical simulation research. In order to simulate the moving diaphragm of the jet as a moving wall boundary, user-defined function (UDF) has been used [29,40,45,52,55]. The governing equations of continuity, momentum and energy based on URANS (Unsteady Reynolds Averaged Navier-Stokes) has been mostly used [26,46,48,49,52,55].…”

Synthetic jet actuator with two opposite diaphragms

“…where Sn is the nozzle exit cross-section area, dS is the differential element of Sn, u(t) is the velocity measured along the nozzle axis, T E is the time of fluid extrusion from the actuator, T = 1/f is the actuation period, f is the actuation frequency. Parameters Re and L * are evaluated according to the following definition [16,27,28]:…”