Frequency-lock reactive control of a separated flow enabled by visual sensors

Abstract

In this study, a simple model based closed-loop algorithm is used to control the separated flow downstream a backward-facing step. It has been shown in previous studies that the recirculation bubble can be minimized when exciting the shear layer at its natural Kelvin-Helmholtz instability frequency. In this experiment, the natural shedding frequency is identified through real-time analysis of 2D velocity fields. Actuation (pulsed jet) is then locked on this frequency. If flow characteristics stray too far from a set point, shedding frequency is updated and actuation changed. The present work demonstrates the efficacy and robustness of this approach in reducing recirculation while Reynolds number is randomly varied between 1400 and 2800. arXiv:1311.0696v1 [physics.flu-dyn]

Analysis and characterization of ramp flow separation

“…The separation can interact with solid walls and, in this case, a recirculation bubble can be observed. The separation can also be generated by geometry discontinuities as for backward facing step (Gautier and Aider 2015). While the separation point can either be fixed or not, the reattachment position is not fixed and depends on many parameters such as the upstream boundary layer, the Reynolds number, the type of ramp or geometric discontinuity.…”

Prediction of the dynamics of a backward-facing step flow using focused time-delay neural networks and particle image velocimetry data-sets

“…It was subsequently improved by Zhou et al [60] and by Chakraborty et al [61]. It was also successfully applied by [62], to visualise the 3D vortices created by a Jet in Cross-Flow measured by Volumetric Velocimetry, and by Gautier et al [63] in a closed-loop flow control experiment using a similar visual sensor. For 2D data, λ Ci can be computed quickly and efficiently using equation 5, when such a quantity is real (else λ Ci = 0):…”

Data-driven order reduction and velocity field reconstruction using neural networks: The case of a turbulent boundary layer

“…The advantage of this algorithm compared to a standard FFT-PIV algorithm is its high computational speed when implemented on GPUs with CUDA functions 8 . The code has been used many times both for timeresolved PIV measurements with a high spatial resolution 31 as well as for closed-loop flow control experiments [10][11][12]32 .…”

“…It was subsequently improved by 36 and by 4 . It was also successfully applied by 3 to visualize the 3D vortices created by a Jet in Cross-Flow measured by Volumetric Velocimetry or by 12 in a closed-loop flow control experiment using a similar visual sensor. For 2D data, λ Ci can be computed quickly and efficiently using eq.…”