Fluidic Oscillator

Bi-stable states jet inside a designed flow chamber.

Aeromines 2016 • Fluid Dynamics

Description

A fluidic oscillator generates periodically oscillating jets without any moving parts. The bi-stable states can be produced by instabilities of incoming flow or by feedback channels. In the following article we will focus on the second method.

V0015: Lagrangian coherent structures in the flow field of a fluidic oscillator

The fluid exits from a convergent nozzle and attaches to a wall side in the chamber due to the ‘wall-attachment’ effect also known as the ‘Coanda’ effect. The flow splashes against the wall and fill a feedback channel. The fluid in the feedback path perturbs the jet and forces it to attach to the other wall. The same thing repeats in the other branch. The output jet starts sweeping.

Create the mesh from an image

From the previous video, we capture an image at t=00:42. The solid part of the oscillator has been colored in white and the picture in $Figure 1$ is obtained. Then, we use the image color to determine the inside from the outside of the oscillator and mesh the edges of the oscillator resulting in the mesh presented in the $Figure 2$.

The mesh is composed of $180 000$ elements with a maximum aspect ratio of $500$ and a minimum mesh size of $10^{-4} m$.

The Simulation

Based on the previous mesh, the simulation was run with $220 000$ mesh elements in a $2 m$ long and $1 m$ high domain, a $10 m.s^{-1}$ water inflow and a time step of $10^{-3} s$. The result is summarized in the following video.

Benchmark your tools

Anyone can try to run this simulation: we provide in the following link the obtained mesh and the references in the section below. We are really looking forward to compare our results.

Download the mesh here

References

Gi-Hun Kim, A study of fluidic oscillators as an alternative pulsed vortex generating jet actuator for flow separation control, Master Degree University of Manchester, 2011
D. Hirsch, E. C. Graff, M. Gharib, Compressible Flows in Fluidic Oscillators, 2013 GFM
Surya Raghu, Fluidic oscillators for flow control, Experiments in Fluids, 2013, 54, 1-11

Acknowledgements


Transvalor
Ibm
Cemef
Carnot Mines
Armines
Mines ParisTech
CNRS

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