scholarly journals Experiments on the stabilization of the no-motion state of a fluid layer heated from below and cooled from above

1998 ◽  
Vol 363 ◽  
pp. 153-171 ◽  
Author(s):  
JIE TANG ◽  
H. H. BAU
Keyword(s):  
Control System ◽  
Feedback Control ◽  
Circular Cylinder ◽  
Silicon Wafer ◽  
Fluid Layer ◽  
Sensors And Actuators ◽  
Multiple Sensors ◽  
Motion State ◽  
Rayleigh Benard ◽  
Conductive State

It is demonstrated experimentally that through the use of feedback control, it is possible to stabilize the no-motion (conductive) state of a fluid layer confined in a circular cylinder heated from below and cooled from above (the Rayleigh–Bénard problem), thereby postponing the transition from a no-motion state to cellular convection. The control system utilizes multiple sensors and actuators. The actuators consist of individually controlled heaters microfabricated on a silicon wafer which forms the bottom of the test cell. The sensors are diodes installed at the fluid's midheight. The sensors monitor the deviation of the fluid temperatures from preset, desired values and direct the actuators to act in such a way as to eliminate these deviations.

Stabilization of the no-motion state in the Rayleigh–Bénard problem

1994 ◽  
Vol 447 (1931) ◽  
pp. 587-607 ◽  
Keyword(s):  
Fluid Layer ◽  
Critical Rayleigh Number ◽  
Control Flow ◽  
Feedback Controller ◽  
Linear Stability Theory ◽  
Motion State ◽  
Conduction State ◽  
Bénard Problem ◽  
Benard Problem ◽  
Rayleigh Benard

Using linear stability theory and numerical simulations, we demonstrate that the critical Rayleigh number for bifurcation from the no-motion (conduction) state to the motion state in the Rayleigh–Bénard problem of an infinite fluid layer heated from below and cooled from above can be significantly increased through the use of a feedback controller effectuating small perturbations in the boundary data. The controller consists of sensors which detect deviations in the fluid’s temperature from the motionless, conductive values and then direct actuators to respond to these deviations in such a way as to suppress the naturally occurring flow instabilities. Actuators which modify the boundary’s temperature or velocity are considered. The feedback controller can also be used to control flow patterns and generate complex dynamic behaviour at relatively low Rayleigh numbers.

scholarly journals Robust feedback control of Rayleigh–Bénard convection

2001 ◽  
Vol 437 ◽  
pp. 175-202 ◽  
Author(s):  
A. C. OR ◽  
L. CORTELEZZI ◽  
J. L. SPEYER
Keyword(s):  
Feedback Control ◽  
Critical Rayleigh Number ◽  
Linear Quadratic ◽  
Parameter Uncertainties ◽  
Sensor Model ◽  
Motion State ◽  
Bénard Convection ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

We investigate the application of linear-quadratic-Gaussian (LQG) feedback control, or, in modern terms, [Hscr ]2 control, to the stabilization of the no-motion state against the onset of Rayleigh–Bénard convection in an infinite layer of Boussinesq fluid. We use two sensing and actuating methods: the planar sensor model (Tang & Bau 1993, 1994), and the shadowgraph model (Howle 1997a). By extending the planar sensor model to the multi-sensor case, it is shown that a LQG controller is capable of stabilizing the no-motion state up to 14.5 times the critical Rayleigh number. We characterize the robustness of the controller with respect to parameter uncertainties, unmodelled dynamics. Results indicate that the LQG controller provides robust performances even at high Rayleigh numbers.

Real-time feedback control system for ADITYA-U horizontal plasma position stabilisation

2021 ◽  
Vol 165 ◽  
pp. 112218
Author(s):  
Rohit Kumar ◽  
Pramila Gautam ◽  
Shivam Gupta ◽  
R.L. Tanna ◽  
Praveenlal Edappala ◽  
...  
Keyword(s):  
Control System ◽  
Feedback Control ◽  
Real Time ◽  
Feedback Control System ◽  
Plasma Position

Electro-magneto wave propagation analysis of viscoelastic sandwich nanoplates considering surface effects

2016 ◽  
Vol 231 (2) ◽  
pp. 387-403 ◽  
Author(s):  
A Ghorbanpour Arani ◽  
M Jamali ◽  
AH Ghorbanpour-Arani ◽  
R Kolahchi ◽  
M Mosayyebi
Keyword(s):  
Zinc Oxide ◽  
Wave Propagation ◽  
Feedback Control ◽  
Graphene Sheet ◽  
Surface Effects ◽  
Structural Damping ◽  
Sensors And Actuators ◽  
Velocity Feedback ◽  
Oxide Layers ◽  
Propagation Analysis

The original formulation of the quasi-3D sinusoidal shear deformation plate theory (SSDPT) is here extended to the wave propagation analysis of viscoelastic sandwich nanoplates considering surface effects. The sandwich structure contains a single layered graphene sheet as core integrated with zinc oxide layers as sensors and actuators. The single layered graphene sheet and zinc oxide layers are subjected, respectively, to 2D magnetic and 3D electric fields. Structural damping and surface effects are assumed using Kelvin–Voigt and Gurtin–Murdoch theories, respectively. The system is rested on an elastic medium which is simulated with a novel model namely as orthotropic visco-Pasternak foundation. An exact solution is applied in order to obtain the frequency, cut-off and escape frequencies. A displacement and velocity feedback control algorithm is applied for the active control of the frequency through a closed-loop control with bonded distributed zinc oxide sensors and actuators. The detailed parametric study is conducted, focusing on the combined effects of the nonlocal parameter, magnetic field, viscoelastic foundation, surface stress, applied voltage, velocity feedback control gain and structural damping on the wave propagation behavior of nanostructure. Results depict that with increasing the structural damping coefficient, frequency significantly decreases.

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