Abstract

Synthetic jets are produced by devices that enable a suction phase followed by an ejection phase. They can be generated with Helmholtz resonators that equip aircraft fan duct or through the motion of actuators for cooling or flow control. The objective of an experimental rig mounted at Institut Pprime (France) is to understand how synthetic jets can enhance heat transfer in a multi-perforated configuration. Large-Eddy Simulations are produced and analyzed in the present document to investigate the flow behavior and the impact of the synthetic jets on wall heat transfer.

The experimental system consists in a perforated heated plate where pistons are used to control the synthetic jets. Placed in a wind tunnel test section, the device can be studied with a grazing flow and multiple operating points are available. The one considered here implies a grazing flow velocity of 12.8 m/s, and a piston displacement of 22 mm peak-to-peak at a frequency of 12.8 Hz, leading to a jet Reynolds number of about 830.

A good agreement is found between numerical results and experimental data. The simulations are used to provide a detailed understanding of the flow. During the ejection phase, the flow transitions to turbulence and the formation of characteristic structures is observed; the plate is efficiently cooled. During the suction phase the main flow is stabilised; the heat enhancement is particularly efficient in the hole wakes but not between them, leading to a heterogeneous temperature field.

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