# Closed-loop enhancement of jet mixing with extremum-seeking and physics-based strategies

Closed-loop enhancement of jet mixing with extremum-seeking and physics-based strategies The closed-loop control of a turbulent round air jet is experimentally investigated based on two unsteady minijets, with a view to enhancing jet mixing. The two minijets are placed at diametrically opposite locations upstream of the nozzle exit. The open-loop control experiments are first performed. Given the mass flow rate ratio C m of the minijets to that of the main jet, the decay rate $$\overline{K}$$ K ¯ of jet centerline mean velocity exhibits a maximum at the frequency ratio f e/f 0 ≈ 1.0, where f e and f 0 are the excitation frequency of minijets and the preferred mode frequency of the natural main jet, respectively. An extremum-seeking feedback control has been developed to achieve autonomously the optimal control performance. It has been found that, given C m, this closed-loop control technique may obtain automatically and rapidly the optimal value of f e and the desired or maximum $$\overline{K}$$ K ¯ , as achieved in the open-loop control. This control technique is robust and adaptable when the Reynolds number and initial excitation frequency are changed separately. A flow-physics-based feedback control strategy has also been investigated, which could achieve the optimal control performance automatically with a shorter convergence time than the extremum-seeking control, not robust though. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experiments in Fluids Springer Journals

# Closed-loop enhancement of jet mixing with extremum-seeking and physics-based strategies

, Volume 57 (6) – Jun 8, 2016
14 pages

/lp/springer_journal/closed-loop-enhancement-of-jet-mixing-with-extremum-seeking-and-pssjbVMS2u
Publisher
Springer Berlin Heidelberg
Subject
Engineering; Engineering Fluid Dynamics; Fluid- and Aerodynamics; Engineering Thermodynamics, Heat and Mass Transfer
ISSN
0723-4864
eISSN
1432-1114
D.O.I.
10.1007/s00348-016-2194-9
Publisher site
See Article on Publisher Site

### Abstract

The closed-loop control of a turbulent round air jet is experimentally investigated based on two unsteady minijets, with a view to enhancing jet mixing. The two minijets are placed at diametrically opposite locations upstream of the nozzle exit. The open-loop control experiments are first performed. Given the mass flow rate ratio C m of the minijets to that of the main jet, the decay rate $$\overline{K}$$ K ¯ of jet centerline mean velocity exhibits a maximum at the frequency ratio f e/f 0 ≈ 1.0, where f e and f 0 are the excitation frequency of minijets and the preferred mode frequency of the natural main jet, respectively. An extremum-seeking feedback control has been developed to achieve autonomously the optimal control performance. It has been found that, given C m, this closed-loop control technique may obtain automatically and rapidly the optimal value of f e and the desired or maximum $$\overline{K}$$ K ¯ , as achieved in the open-loop control. This control technique is robust and adaptable when the Reynolds number and initial excitation frequency are changed separately. A flow-physics-based feedback control strategy has also been investigated, which could achieve the optimal control performance automatically with a shorter convergence time than the extremum-seeking control, not robust though.

### Journal

Experiments in FluidsSpringer Journals

Published: Jun 8, 2016

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