Feedback Control for Promoting or Suppressing the Transition to Weak Turbulence in Porous Media Convection

2015 ◽  
pp. 479-490 ◽  
Keyword(s):  
Porous Media ◽  
Feedback Control ◽  
Weak Turbulence

Promoting or Suppressing Transition to Weak Turbulence in Porous Media Convection via Feedback Control

2011 ◽  
Author(s):  
Peter Vadasz
Keyword(s):  
Porous Media ◽  
Feedback Control ◽  
Transition Point ◽  
Initial Conditions ◽  
Practical Significance ◽  
Weak Turbulence ◽  
Simple Transformation ◽  
Transition To Chaos ◽  
Main Effect ◽  
Transformation Of Variables

A method of using feedback control to promote or suppress the transition to chaos in porous media convection is demonstrated in this paper. Feedback control is used in the present paper to provide a comparison between an analytical expression for the transition point to chaos and numerical results. In addition it is shown that such a feedback control can be applied as an excellent practical means for controlling (suppressing or promoting) chaos by using a Magyari transformation. The latter shows that the controlled model can be transformed into the uncontrolled one via a simple transformation of variables implying that the main effect the feedback control has on the solution is equivalent to altering the initial conditions. The theoretical and practical significance of such an equivalent alteration of the initial conditions is presented and discussed.

Weak Turbulence in Small Prandtl Number Convection in Porous Media

2010 ◽  
Author(s):  
Peter Vadasz
Keyword(s):  
Porous Media ◽  
Stability Analysis ◽  
Prandtl Number ◽  
Linear Stability ◽  
Linear Stability Analysis ◽  
Weak Turbulence ◽  
Numerical Computations ◽  
Prandtl Numbers ◽  
Convection In Porous Media

The dynamics of weak turbulence in small Prandtl number convection in porous media is substantially distinct than the corresponding dynamics for moderate and large Prandtl numbers. Linear stability analysis is performed and its results compared with numerical computations to reveal the underlying phenomena.

Feedback control of temperature in specific geometry of porous media: application to hyperthermia

2020 ◽  
Vol 141 (5) ◽  
pp. 1559-1568
Author(s):  
Amir Rezvanian ◽  
Borhan Beigzadeh ◽  
Amir Hossein Davaei Markazi ◽  
Mahdi Halabian
Keyword(s):  
Porous Media ◽  
Feedback Control ◽  
Specific Geometry

Sudden and Smooth Transitions to Weak Turbulence in Porous Media Convection

2003 ◽  
Author(s):  
Johnathan J. Vadasz ◽  
Joseph E. A. Roy-Aikins
Keyword(s):  
Porous Media ◽  
Three Dimensional ◽  
Flow In Porous Media ◽  
Lorenz Attractor ◽  
Weak Turbulence ◽  
Periodic Regime ◽  
Linear Interaction ◽  
Isothermal System ◽  
Smooth Transitions ◽  
Convection In Porous Media

The fundamental understanding of the transition from laminar to turbulent convection in porous media is far from being conclusive. In isothermal flow in porous media no experiments identifying the three dimensional nature of a transition from the Darcy regime, via an inertia dominated regime, towards turbulence are available. In particular this detailed description of turbulence is missing in the problem of porous media convection where an additional non-linear interaction appears as a result of the coupling between the equations governing the fluid flow and the energy equation. The latter can typically cause a transition to a non-steady and non-periodic regime (referred to as weak turbulent) at much lower values of the parameter controlling the flow, when compared to the corresponding isothermal system. The present paper identifies the conditions for sudden and smooth transitions. In addition it attempts to address the question related to the reason for the subcritical transition to weak turbulence and the existence of a range of values of the porous media Rayleigh number over which the transition occurs, i.e. the Lorenz attractor.

scholarly journals VELOCITY CHARACTERISTICS IN WAKE OF A NON-SPHERE BODY AND IN PORE OF POROUS MEDIA COMPOSED OF NON-SPHERES

2020 ◽  
pp. 58
Author(s):  
Yuji Yamamura ◽  
Takaaki Shigematsu ◽  
Sota Nakajo
Keyword(s):  
Porous Media ◽  
Velocity Field ◽  
Steady Flow ◽  
Turbulence Intensity ◽  
Angle Of Attack ◽  
Prolate Spheroid ◽  
Weak Turbulence ◽  
Velocity Change ◽  
Hydraulic Experiment ◽  
Significant Change

Details of a velocity field around a prolate spheroid in a steady flow with different angles of attack were investigated by carrying out a hydraulic experiment using the PTV technique. It was found that characteristics of the vortex in the wake of the prolate spheroid were different depending on the angle of attack. It was clearly found that the velocity field changes significantly in the wake. That is to say that there were some areas with strong and weak turbulence and that also some areas with a certain periodic and unclear periodic velocity change with significant change. It was clear that these characteristics depend on the angle of attack of the spheroid. Further, it was confirmed that the distribution of the turbulence intensity was different between the horizontal and vertical components.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/34Dw1CSLEz4

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