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Special Issue "Physics in Engineering: A Themed Issue in Honour of Professor Peter Vadasz on the Occasion of His 70th Birthday"

A special issue of Physics (ISSN 2624-8174). This special issue belongs to the section "Classical Physics".

Deadline for manuscript submissions: 31 October 2021.

Special Issue Editors

Dr. D. Andrew S. Rees
E-Mail Website
Guest Editor
Department of Mechanical Engineering, University of Bath, Bath BA2 7AY, UK
Interests: convection; porous media; instability; numerical simulation; asymptotic analysis; non-Newtonian fluids
Special Issues and Collections in MDPI journals
Dr. Saneshan Govender
E-Mail
Guest Editor
1. Eskom Holdings SOC, Maxwell Drive, Sunninghill, Sandton, PO Box 1091 Johannesburg, South Africa
2. School of Mechanical Engineering, University of Kwa Zulu Natal, Durban 4000, South Africa

Special Issue Information

Dear Colleagues,

text

It is our priviledge and honour to guest edit this Special Issue, which is dedicated to Professor Peter Vadasz on the occasion of his 70th birthday. Although he has many interests, he is an eminent leader and authority on the study of convective instabilities in porous media and has a particular interest in rotating systems of different kinds. He has dedicated much of his career to such systems and has recently published the well-received monograph, “Fluid Flow and Heat Transfer in Rotating Porous Media”. He has also been honoured by having the Vadasz number named for him.

Besides being an exemplary scientist he was/is known for having the “Vadasz Effect” as a teacher. He joined the University of Durban-Westville in 1991 at a crucial time in the engineering faculty’s history. As a start, he led a team that resulted in the engineering faculty receiving full accreditation from the Engineering Council of South Africa (ECSA). From that point on, his academic and administrative prowess became legendary. His students have described him as someone who is down to earth and approachable, to the extent that his lectures were always filled with interesting content, international affairs and very interesting scientific titbits that you could never read about. A student can attest to this. His inspiration, openness, and willingness to share his knowledge has inspired hundreds of students that graduated under him. To that end, most of those students try to mimic his work ethic and principles and today hold important and influential positions in key institutes/organizations. In 2002, Professor Peter Vadasz joined Northern Arizona University as the chair of mechanical engineering, where he is currently employed today. 

Dr. D. Andrew Rees
Dr. Saneshan Govender
Guest Editors

Manuscript Submission Information

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Keywords

  • instability
  • convection
  • rotating systems
  • weak turbulence
  • nanofluids
  • transport phenomena in porous media
  • fluid dynamics
  • heat transfer
  • nanotechnology–nano-heat transfer
  • biological engineering
  • investigation of nonlinear effects-stability, bifurcation, and routes to chaos
  • physical and mathematical modeling and simulations

Published Papers (5 papers)

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Research

Article
Instability of Vertical Throughflows in Bidisperse Porous Media
Physics 2021, 3(4), 821-828; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3040052 (registering DOI) - 23 Sep 2021
Viewed by 154
Abstract
In this paper, the instability of a vertical fluid motion, or throughflow, is investigated in a horizontal bidisperse porous layer that is uniformly heated from below. By means of the order-1 Galerkin approximation method, the critical Darcy–Rayleigh number for the onset of steady [...] Read more.
In this paper, the instability of a vertical fluid motion, or throughflow, is investigated in a horizontal bidisperse porous layer that is uniformly heated from below. By means of the order-1 Galerkin approximation method, the critical Darcy–Rayleigh number for the onset of steady instability is determined in closed form. The coincidence between the linear instability threshold and the global nonlinear stability threshold, in the energy norm, is shown. Full article
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Article
Vadasz Number Effects on Convection in a Vertical Rotating Porous Layer, Placed Far from Axis of Rotation, and Subjected to Internal Heat Generation and Centrifugal Jitter
Physics 2021, 3(3), 728-738; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3030044 - 01 Sep 2021
Viewed by 407
Abstract
The flow and heat transfer in a rotating vertical porous layer, placed far from the axis of rotation, and subjected to internal heat generation and centrifugal jitter, is considered. The linear stability theory is used to determine the convection threshold, in terms of [...] Read more.
The flow and heat transfer in a rotating vertical porous layer, placed far from the axis of rotation, and subjected to internal heat generation and centrifugal jitter, is considered. The linear stability theory is used to determine the convection threshold, in terms of the critical Rayleigh number. Typical liquids used in engineering applications and heavy liquid metals are used to demonstrate conditions at which the Vadasz number is sufficiently small to warrant the retention of the time derivative in the momentum equation. When considering low amplitude and high frequency approximation, the results show that vibration has a stabilizing effect on the onset of convection. The impact of increasing the Vadasz number is to stabilize the convection, in addition to reducing the transition point from synchronous to subharmonic solutions. In summary, when the Vadasz number is large, centrifugal jitter has no impact on the convection stability criteria. In contrast, when the Vadasz number is small, centrifugal jitter impacts the convection stability criteria. Full article
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Article
Spatially Developing Modes: The Darcy–Bénard Problem Revisited
Physics 2021, 3(3), 549-562; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3030034 - 30 Jul 2021
Viewed by 291
Abstract
In this paper, the instability resulting from small perturbations of the Darcy–Bénard system is explored. An analysis based on time–periodic and spatially developing Fourier modes is adopted. The system under examination is a horizontal porous layer saturated by a fluid. The two impermeable [...] Read more.
In this paper, the instability resulting from small perturbations of the Darcy–Bénard system is explored. An analysis based on time–periodic and spatially developing Fourier modes is adopted. The system under examination is a horizontal porous layer saturated by a fluid. The two impermeable and isothermal plane boundaries are considered to have different temperatures, so that the porous layer is heated from below. The spatial instability for the system is defined by taking into account both the spatial growth rate of the perturbation modes and their propagation direction. A comparison with the neutral stability condition determined by using the classical spatially periodic and time–evolving Fourier modes is performed. Finally, the physical meaning of the concept of spatial instability is discussed. In contrast to the classical analysis, based on spatially periodic modes, the spatial instability analysis, involving time–periodic Fourier modes, is found to lead to the conclusion that instability occurs whenever the Rayleigh number is positive. Full article
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Article
Considerate Regulation of Output Disturbances
Physics 2021, 3(2), 173-186; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3020014 - 02 Apr 2021
Viewed by 543
Abstract
Recently, I have considered a multi-variable feedforward control practice in a novel way being called “considerate control”. It was shown how the considerate control is related to Bristol gains, which indicate accurately either the required increase in input scope or the reduced output [...] Read more.
Recently, I have considered a multi-variable feedforward control practice in a novel way being called “considerate control”. It was shown how the considerate control is related to Bristol gains, which indicate accurately either the required increase in input scope or the reduced output scope as compared to inconsiderate control. Here, considerate control is expanded to regulating control, necessitating some feedback design. Clearly, high-gain feedback leads to considerate control results in low frequency. Considerate pre-compensation decouples loops also at higher frequencies. However, as an analysis of the included examples demonstrates, such considerate design may insert non-minimum phase-lag into loops that did not have it, thus, reducing the loop bandwidth relative to that achievable in a skillful inconsiderate design, sometimes very significantly. As is often the case, there is a trade-off between consideration and performance. Full article
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Article
A Hidden Anomaly in the Binary Mixture Natural Convection Subject to Flux Boundary Conditions
Physics 2021, 3(1), 144-159; https://0-doi-org.brum.beds.ac.uk/10.3390/physics3010012 - 23 Mar 2021
Viewed by 526
Abstract
The problem of natural convection in a binary mixture subject to realistic boundary conditions of imposed zero mass flux on the solid walls shows solutions that might lead to unrealistic negative values of the mass fraction (or solute concentration). This anomaly is being [...] Read more.
The problem of natural convection in a binary mixture subject to realistic boundary conditions of imposed zero mass flux on the solid walls shows solutions that might lead to unrealistic negative values of the mass fraction (or solute concentration). This anomaly is being investigated in this paper, and a possible way of addressing it is suggested via a mass-fraction-dependent thermodiffusion coefficient that can have negative values in regions of low mass fractions. Full article
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