Andrew Rees

Dr D A S Rees

Department: Mechanical Engineering
Job Title: Reader in Fluid Dynamics
                 Visiting Professor at the Université Paul Sabatier, Toulouse, France

Qualifications: PhD (Applied Mathematics, Bristol, 1986)
                         BSc (1st in Mathematics, Imperial College, 1980)
                         ARCS (Royal College of Science/I.C., 1980)
                         ATCL (Trinity College of Music, London, 1977).

Telephone: (01225) 386775 (Office)
E-mail Address: D.A.S.Rees@bath.ac.uk  or  ensdasr@bath.ac.uk
Fax: (01225) 386928

Work Address:

Extracurricular activities

Bristol Christian Fellowship
St. John's Keynsham
Bristol Concert Orchestra .
Keynsham Orchestra .
Orchestra for the Bristol Catholic Players
Bristol/Bath cyclepath homepage photos Other cycling sites Facility of the month (link at bottom left) Bike bits
Siân Rees: Supporting Head-Injured Pupils in School. The SHIPS project.
Local research seminars

Undergraduate matters....

Mathematics 1 (ME10304)
Mathematics 2 (ME10305)
Modelling Techniques 2 (ME20021)

Academic background

After A-levels in Chemistry, Physics, Pure Maths, Applied Maths and Music, Dr. D. A. S. Rees obtained a first class honours degree in Mathematics from Imperial College in 1980 and then worked for two years at British Aerospace, Filton, on problems in structural dynamics and aeroelasticity. He subsequently studied for a Ph.D. in Applied Mathematics at University of Bristol under the supervision of Professor David Riley who is now at University of Nottingham. The thesis was entitled "Convection in porous media" and the degree awarded in 1986. Following a three year postdoctoral research assistantship under the same supervisor he was employed as a temporary lecturer in Applied Mathematics at the University of Exeter for two years. He then joined the Department of Mechanical Engineering at Bath in April 1990, and was promoted to a Readership in September 1998. He currently has 137 journal papers in print with 3 submitted and 6 review chapters. My current publication list is here, and papers in the press are here.

In 2006 he was presented with the Mary Tasker Award for Teaching Excellence by the University of Bath.

In 2007 he presented the G I Taylor Memorial Lecture at the 52nd ISTAM conference in Bangalore, India.

In 2009 he became a visiting professor at the Université Paul Sabatier, Toulouse, France.

He also has an A.T.C.L. diploma in violin performance from the Trinity College of Music, London which he obtained in 1977, and is a former member of the Cerddorfa Genedlaethol Ieuenctid Cymru.

He is an associate editor for the journals:
   Journal of Porous Media (from 1998)
   International Journal for Numerical Methods in Heat and Fluid Flow (from 2004)
   Computational Thermal Sciences (from 2008)
   The Open Transport Phenomena Journal (from 2009).
   Special Topics & Reviews in Porous Media - An International Journal (from 2010).

Research Interests (Updated 5/2007)

I am interested in many areas of fluid dynamics especially convective flows, such as free convection boundary layers, convection in layers and buoyancy induced flows in porous media. In particular, my aim is to investigate the stability of these flows, to determine how, where or when they become unstable, and to follow the subsequent evolution of such instabilities. To this end I use a combination of analytical methods such as parallel and nonparallel stability theory, weakly nonlinear theory, and numerical methods such as direct solvers, multigrid methods and direct numerical simulation.

To date I have 137 journal publications, 63 conference papers, 6 review chapters and two sets of typeset lecture notes for overseas courses entitled: Perturbation Methods for solving ODEs and PDEs (University of Dhaka, September 2000) and The Stability of Darcy-Bénard Convection (Summer School on Porous Media, Neptun, Constanţa, Romania, July 2001). The course on Darcy-Bénard convection summarises aspects of the linear and weakly nonlinear stability analyses which may be undertaken for this problem both in its classical form and for some of its various modifications. Should anyone download either of of these courses, then please let me know by email so that I can gauge the level of interest in these topics.

At present I am collaborating with a number of researchers from different countries. Prof Ioan Pop (University Babes Bolyai, Cluj, Romania) and I are undertaking work on thermal boundary layer flows in porous media, the effects of g-jitter, the effects of local thermal nonequilibrium in porous medium free convection, and free convection boundary layer flows of micropolar fluids. With Prof Leiv Storesletten (Agder University College, Kristiansand, Norway) I am looking at the effect of mechanical and thermal anisotropy on convection in porous media. Dr Adrian Postelnicu (Transilvania University of Brasov, Romania) and I have also been investigating the stability of convection in inclined anisotropic porous layers. Prof Andrew Bassom (UWA Perth, Australia) and I are investigating thermal boundary layer instabilities.

In addition to the above, I am currently developing codes to simulate vortex instabilities in free convective boundary layer flows in porous media. When the heated surface is close to the vertical, the distance from the leading edge beyond which vortex disturbances grow is very large. Thus it is possible to apply the boundary layer approximation to the disturbance equations to obtain a mathematically consistent description of the fate of disturbances. Moreover, nonlinear vortex development and secondary instabilities may also be described within this framework.

My recently graduated PhD student, Manosh Paul (now lecturing at the University of Glasgow), undertook a numerical study of the linear and nonlinear development of two-dimensional waves in the classical vertical free convection boundary layer flow of Newtonian fluid from a constant temperature surface. The code solves the fully elliptic system and the work concentrates on (1) how an isolated thermal disturbance evolves in time and develops spatially and (2) how the boundary layer responds to an oscillatory disturbance. For (1) we find that the flow exhibits the (confusingly so-called) convective instability which we attribute to the fact that the basic flow accelerates. In (2) we find that the boundary layer has a resonant frequency in the sense that there is one specific frequency of disturbance which maximises the linear response. More recent work has extended the analysis to nonlinear convective waves.

Recent work in collaboration with Prof Storesletten and Prof Bassom on the effect of anisotropy and/or nonsymmetrical bounding surfaces on line-source plumes has show that the position of the centreline of the plume is affected very strongly by the asymmetric perturbations.

A very recent research focus has been the microscopic modelling of local thermal non-equilibrium effects in porous medium conection. Many situations exist where the usage of a single thermal energy equation fails to describe adequately the development of the thermal field in a porous medium. Such situations often involve relatively fast fluid motion so that hot fluid, for instance, may penetrate a great distance into a porous medium before the solid phase is able to heat up substantially. In such instances two energy equations may be used to model the evolution of the temperature fields in the two phases. These equations are coupled by a simple linear source/sink term to allow heat to transfer between the phases. A heat transfer coefficient has been postulated, but little is known about how it depends on the physical structure of the porous medium and the thermal properties of the fluid and solid phases. A paper on this topic has just been submitted to the Journal of Porous Media and it may be found here.

Current collaborative projects:

Ibrahim Jais (PhD - writing up)
Effect of unsteady heating on Darcy-Bénard convection in porous media.

Asma Selim (PhD - writing up)
Instabilities of unsteady boundary layers in porous media.

Greg Tourte (PhD 4th year, part time)
Numerical simulations of three dimensional convection in porous media.

Michele Celli (Visiting student, Bologna), Antonio Barletta (DIENCA, Bologna)
Convective instability with viscous dissipation in porous media.
(1/2/2008 to 31/7/2008)

Adekojo Waheed (Visiting fellow, Ladoke Akintola University of Technology, Ogbomoso, Nigeria)
Feedback control of convection in porous media.
(1/1/2008 to 30/6/2008)

Abdelkader Mojtabi (Visiting Scientist, Université Paul Sabatier, Toulouse, France)
Some problems in Darcy-Bénard convection.
(4/4/2008 to 28/4/2008)

Estelle Guillot (ENSEEIHT, Toulouse, France)
Network modelling of strong convection in porous media.
(1/7/2008 to 31/8/2008)

Harry Zhang (MSc, Aero Eng)
Instability of a developing vertical thermal boundary layer.

Susanna Nilsson (MSc, Applicable Mathematics)
CO2 sequestration.

Craig Dickinson (MSc, Applicable Mathematics)
tbc

Jennifer Papke, Ada Md Zubir, Ricardo Ramos Tomas (MEng, F.Y.P.)
Microscopic modelling of local thermal nonequilibrium in porous media.

Christian Odenthal (MEng F.Y.P.)
Convective instability in an infiltrating channel flow.

Pradeep Siddheshwar (Department of Mathematics, Bangalore University, India)
Stability of Lapwood-Prats convection with local thermal nonequilibrium.

Andrew Bassom (Mathematics, UWA Perth, Australia)
Infiltration fronts in porous media with local thermal nonequilibrium.

Manosh Paul (Mechanical Engineering, Glasgow)
Vertical thermal boundary layer instabilities.

Don Nield (Auckland), Andrey Kuznetsov (North Carolina State University)
Boundary layers in bidisperse porous media.

Recent Collaborators:

Adrian Postelnicu Thermal Engineering and Fluid Mechanics, Transylvania Universitu of Brasov, Romania.
Aminreza Noghrehabadi Mechanical Engineering, Chamran University of Ahvaz, Ahvaz, Iran.
Andrew Bassom Mathematics and Statistics, University of Western Australia, Crawley, Perth, Australia.
Andrey Kuznetsov Mechanical Engineering, North Carolina State University, Raleigh, NC 27695-7910, USA.
Antonio Barletta Dipartimento di Ingegneria Energetica, Nucleare e del Controllo Ambientale, Alma Mater Studiorum - Universita di Bologna, Bologna, Italy.
Gamze Genç Department of Mechanical Engineering, Erciyes University, Kayseri, Turkey.
Anwar Hossain, Mathematics, University of Dhaka, Bangladesh, and COMSATS University, Islamabad, Pakistan.
Arunn Narasimhan Mechanical Engineerning, IIT Madras, Chennai, India.
Don Nield Engineering Science, University of Auckland, New Zealand.
Ioan Pop, Mathematics, University Babes Bolyai, Cluj-Napoca, Romania.
Leiv Storesletten Mathematics, Agder University, Kristiansand, Norway.
Manosh Paul Mechanical Engineering, Glasgow University, Scotland.
Peder Tyvand Mathematics, Norwegian University of Life Sciences, Aas, Norway.
Pradeep Siddheshwar, Mathematics, Bangalore University, Bangalore, India.

Last updated April 2008.