Stéphane Orieux

Numerical and Experimental Analysis of Monostable Mini- and Micro-Oscillators

An asymmetric micro-oscillator design based on a monostable fluidic amplifier is proposed. Experimental data with various feedback loop configurations point out that the main effect responsible for the oscillation is a capacitive and not a propagative effect. Actually, sound propagation in the feedback loop only generates a secondary oscillation which is not strong enough to provoke the jet switching. Data from a hybrid simulation using a commercial CFD code and a simple analytical model are in good agreement with the experimental data. A more compact plane design with reduced feedback loop volumes is also studied through a fully CFD simulation that confirms the previous conclusions.

Experimental and Numerical Study of the Frequency Response of a Fluidic Oscillator for Active Flow Control

A series of new bi-stable fluidic oscillators which can generate discrete pulsed jets in a wide frequency range (50-300Hz) with maximum velocities of the order of 200 m/s have been developed for flow separation control purposes. A preliminary experimental analysis of the prototypes has been performed thanks to a pressure sensor and the results have shown that the oscillation frequency has a nearly linear relationship with the length of its feedback loops. Thus, a new function is proposed to estimate the oscillation frequency according to the experimental results. In addition, numerical simulations are carried out in order to better understand the jet switching mechanism inside the oscillator and identify the parameters controlling the dynamics of these oscillations. Finally, it is verified that the switching process of the main jet is not only controlled by the pressure difference between the two control nozzles, but also by the pressure difference between the two main branches of the oscillator. This new finding will be of great help in future design of this kind of fluidic oscillators.