Validating a Reduced-Order Model for Synthetic Jet Actuators Using CFD and Experimental Data

Tim Persoons,Rick Cressall,Sajad Alimohammadi

doi:10.3390/act7040067

Tim Persoons, Rick Cressall + Show 1 more

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https://doi.org/10.3390/act7040067

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Journal: Actuators	Publication Date: Sep 28, 2018
Citations: 5	License type: CC BY 4.0

Affiliation: Trinity College Dublin, University of Notre Dame

Abstract

Synthetic jet actuators (SJA) are emerging in various engineering applications, from flow separation and noise control in aviation to thermal management of electronics. A SJA oscillates a flexible membrane inside a cavity connected to a nozzle producing vortices. A complex interaction between the cavity pressure field and the driving electronics can make it difficult to predict performance. A reduced-order model (ROM) has been developed to predict the performance of SJAs. This paper applies this model to a canonical configuration with applications in flow control and electronics cooling, consisting of a single SJA with a rectangular orifice, emanating perpendicular to the surface. The practical implementation of the ROM to estimate the relationship between cavity pressure and jet velocity, jet velocity and diaphragm deflection and applied driving voltage is explained in detail. Unsteady Reynolds-averaged Navier Stokes computational fluid dynamics (CFD) simulations are used to assess the reliability of the reduced-order model. The CFD model itself has been validated with experimental measurements. The effect of orifice aspect ratio on the ROM parameters has been discussed. Findings indicate that the ROM is capable of predicting the SJA performance for a wide range of operating conditions (in terms of frequency and amplitude).

Highlights

Synthetic jet actuators (SJAs) generate a train of vortices which are formed by periodic suction and ejection of the same amount of fluid across an orifice
An synthetic jet actuator (SJA) typically consists of a piezoelectric or electromagnetic driver deflecting a flexible membrane inside a cavity, which is connected to an external body of fluid through a short nozzle or orifice (The terms ‘nozzle’ and ‘orifice’ will be used interchangeably in this paper)
The frequency domain results are plotted as a function of the normalized frequency ω/ω H (= f / f H ), where f H takes the aforementioned values for 2D and 3D data

Summary

Introduction

Synthetic jet actuators (SJAs) generate a train of vortices which are formed by periodic suction and ejection of the same amount of fluid across an orifice. This establishes a directional flow with zero net mass input, formed from the ambient fluid surrounding the orifice, “synthetic” jet [1,2]. These types of actuators have been used to control flow separation and noise, e.g., in aviation applications, as well as more recently in the thermal management of electronics. At a sufficiently high stroke length [3], a stable vortex detaches from the orifice and propagates into the surrounding flow field, thereby imparting momentum to a boundary layer

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