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Professor Ken Walters at 80
Journal of Non-Newtonian Fluid Mechanics 222 (2015) vi–vii
Contents lists available at ScienceDirect
Journal of Non-Newtonian Fluid Mechanics journal homepage: http://www.elsevier.com/locate/jnnfm
Professor Ken Walters at 80 I first met Ken Walters in 1964 as an undergraduate member of his hydrodynamics class, going on later to become one of his early postgraduate students. Those were exciting times at Aberystwyth, where Ken led pioneering work, both experimental and theoretical, including some of the first computer simulation predictions. Over the years the Aberystwyth group grew to be a leader in the rheology community, attracting visitors from around the world. In 1994, Elsevier dedicated a special issue of the Journal of Non-Newtonian Fluid Mechanics (Volume 54) to Ken on the occasion of his 60th birthday and I was privileged to write a tribute to Ken as an introduction to that volume. Well he was nearing retirement wasn’t he. What a ridiculous idea. Twenty years later he is still publishing research papers and giving plenary lectures.
searched for Rheology’s missing link, a model which is simple enough to lead to tractable boundary-value behaviour in simple rheometrical flow situations. The undoubted failure to find such a model up to the present time is one of the sorrows of some of us who have invested a lifetime’s research in the field. However, the discovery of the Boger constant-viscosity highly elastic liquid has recently given renewed hope in this direction at least for a small sub-set of real elastic liquids, with the side effect that some of the early analyses for simple fluid models may not be as obsolete is their dating would suggest.’’
In 1994 I wrote: ‘He(Ken) is not only a brilliant researcher himself, but also a great motivator of others. A whole host of his past research students owe their careers to the start given to them at Aberystwyth. There will be few indeed in the rheology community at large who have not benefited in some way from his contributions, whether it be through the Journal(JNNFM), through the host of courses to which he has contributed, and through the many different meetings he has organised’
Conceived, initiated, and driven to completion by Ken was the book Rheological Phenomena in Focus (1993). The same enthusiasm and drive saw the completion of two DVDs produced by the Institute of Non-Newtonian Fluid Mechanics: Boger Fluids in 2004 and Yield Stress Fluids in 2008.
That statement is even more true today, for he remains a very active member of the community. I considered approaching some of Ken’s collaborators for their memories but the list of names just grew and grew. I’ve chosen just three particularly close collaborators: David Boger, Marcel Crochet and Roger Tanner. To the many who would have wished to contribute to this introduction, I must apologise for it would take a significant volume in itself to record the recollections of each one. David writes: Ken has been a friend and mentor for as long as I can remember. He really is the brother I never had. I was aware of Ken’s reputation as early as 1971 when I arrived at Aberystwyth unannounced while visiting Manchester University. Unfortunately he was not there (travelling, as usual) and I was entertained by Mervyn Jones. The first formal meeting was in 1974 at the Theoretical Rheology meeting at Cambridge University organised by Ken and Anthony Pearson. The most important event in my career was an IUTAM symposium on Non-Newtonian Fluid Mechanics organised by Marcel Crochet in Louvain-la-Neuve in 1978. The scientific committee for the meeting was Marcel, Ken, Ronald Rivlin, and Hanswalter Giesekus. Here we presented our observations on elastic effects in creeping flow in a 4 to1 contraction where the experimental observations were made with constant viscosity elastic fluids (JNNFM 3(1), 87-91 (1977)). The 4 to1 contraction later became a test problem for the Numerical Simulation community and the workshops that were held annually thereafter. At this meeting Ken highlighted our work when he said in his Plenary introduction to the conference: ‘‘Researchers have
Since the Louvain-la-Neuve meeting I have enjoyed many activities with Ken, including presentation of intensive courses in Belgium, Italy, USA and Australia. Other lecturers in these course included H. Giesekus, B. Bird, M. Crochet, G. Marucci, Z. Tadmor and O. Hassager.
Over the years I have enjoyed many, many visits to Aberystwyth, hosted by Ken and Mary, kicking the bar on every occasion, and have thoroughly enjoyed the annual Easter meeting of the Non-Newtonian Fluid Mechanics Institute. There have been some amazing dinners at country houses and of course I have followed Ken, with others, on many occasions in search of ice cream. Some of my most memorable experiences, however, were when travelling with the Welsh Mafia (Peter Townsend, Russell Davies, Eirian Jones). On one such occasion we met in Seattle, Washington, rented cars and travelled for days to the American Society of Rheology meeting in Sacramento, California. What happened on these trips has stayed and will stay on these trips. Ken has had a great career with many achievements and awards but really the greatest achievement of all was marrying Mary; she has been a fabulous support. ‘‘Behind every great man is an exhausted woman’’. Well done, Mary. Happy Birthday Ken. I wish I could have attended the meeting in your honour. David Marcel writes: Ken and I must have met for the first time in 1975 on the occasion of a symposium in Toulouse. We discovered a common desire to go past the analytical calculation of Poiseuille and Couette flows of viscoelastic fluids and to use numerical methods for simulating and understanding more complex experimental observations. Ken had the great advantage of combining experimental expertise – he was just publishing his bestseller ‘‘Rheometry’’ – and high level mathematical training.
Professor Ken Walters at 80 / Journal of Non-Newtonian Fluid Mechanics 222 (2015) vi–vii
We sympathized immediately and we began to cooperate and exchange information. Soon, Ken invited me to visit Aberystwyth. A wonderful expedition at the time! Flight to London, train to Birmingham, Wolverhampton and finally Aberystwyth on a single track – I was told that the train drivers were exchanging a baton – before landing at the Bellevue Hotel where I could hear the seagulls crying on the waves. These visits were great days! Meetings in Ken’s office with members of his research team, seminars, discussions with Ph.D. students, visit to the lab to observe the latest experiments. Ken is a wonderful host. I remember the nice lunches offered by Mary at Pen-y-Graig, dinners in a recently recommended pub followed by a walk on the seafront to ‘‘kick the bar’’. The atmosphere was very relaxing, despite the fact that Ken, a hard worker, must have endured some stress over all these years – publishing a book, advising a team of Ph.D. students, launching and editing a very successful journal, giving lectures all over Europe. Our respective visits to Aberystwyth and Louvain-la-Neuve would continue for many years, fed by numerous participations to Ph.D. committees and also lectures at the Von Karman Institute near Brussels. In the mid-seventies, the challenges in non-Newtonian fluid mechanics were such that it was decided to hold a IUTAM symposium on the subject in Louvain-la-Neuve in 1978. The scientific committee was composed of Ken, Ronald Rivlin, Hanswalter Giesekus and myself. Ken was of considerable help. He had a deep knowledge of who were the pioneers in the field and he knew everyone. We were anxious at the time to progress in the field of numerical simulation, all excited too by the extraordinary films which David Boger had just produced, exhibiting unexpected flow bifurcations. The IUTAM symposium became the origin of the ‘‘Workshops on numerical methods in viscoelastic flow’’, of which some of the major participants were the Welsh team (Ken, Russel Davies, Peter Townsend and several others), Roger Tanner, Bruce Caswell, David Boger. . . A couple of years later, it was Ken’s idea to coauthor a book on numerical simulation with Russel and myself. It was particularly exciting to exchange and comment on the presentation of constitutive equations, confronting the Oldroyd school to the ‘‘simple fluid’’ theory of Coleman and Noll. We met several times before completing the book. The field was progressing month after month (and of course it continued after its publication in 1984), requiring frequent modifications, while Ken’s secretary was typing under his supervision a very difficult manuscript. The decade which followed was marked by a continuous exchange of information, new topics fed by Ken’s imagination and curiosity, such as interfacial effects which led to a joint publication, lectures for the benefit of Polyflow customers in Japan, where I remember Ken being a complete evening on a diet because he could not possibly eat a fish so fresh that its eyes were blinking. My own life reached a bifurcation point in 1995 which prevented me from pursuing my scientific career. While we maintained the friendly relationship that we had built over the years, I missed the professional exchange which was so enriching. I am however fully aware that Ken has pursued his scientific leadership associated with the friendliest presence. Thank you, Ken, and Happy Birthday ! Marcel.
vii
And finally, Roger writes: As far as I remember. I first met Ken around 1958 during a visit to Professor Oldroyd in Swansea, where Ken was doing his PhD. I was also doing my PhD (in Manchester) and I had begun to read Oldroyd’s seminal papers and needed some help. Our next meeting, I believe, was in 1963 in Providence, Rhode Island during the Fourth International congress on Rheology where we read papers and had a good time. I recall Ken visiting me at Brown University later, about 1974. At that time he was promoting the founding of the JNNFM and he asked me what I thought of the idea, citing some opposition to the concept from existing fluid mechanics journals. Typically, he made his case and the JNNFM began in 1976 and continues to gather strength. We met many times after that and my wife and I were the recipients of much generous Aberystwyth hospitality from Ken and Mary. A vivid memory of ‘younger Ken’ is from the 1984 (Mexico) International Congress where he was often seen in the annular swimming pool or at the island bar in the centre where they dispensed coco-locos, pina coladas and other exciting drinks. (This sort of scene was not possible when Ken organised the 2000 International Congress in Cambridge, even though the weather was good by British standards). We wrote a book entitled ‘Rheology: An Historical Perspective’ (Elsevier 1998) and I have commented on this experience in the British Society of Rheology Bulletin (Vol 53, No 3 2012,pp 91-96), showing that Ken can be a slave-driver in these situations. The other document we wrote together was a chapter entitled ‘ The motion of a sphere through an elastic fluid’ pp73-86 in a book edited by R.P. Chhabra and D.De Kee entitled ‘Transport processes in bubbles, drops and particles’ published by Hemisphere, New York (1992). The chapter reviewed the progress made in finding the drag on a sphere falling centrally in a tube filled with an Oldroyd-B model fluid.. It seemed easy (no sharp corners) but it proved otherwise. Not until the work of Yurun Fan (JNNFM 84,233-256,1999) was it realised that beyond a critical Weissenberg number of about one the stress field in the wake of the sphere was not able to be converged. Ken stepped down as Editor of the JNNFM in 2002, and since then there have often been two Editors to carry the load. I have already commented in the September issue of the Journal on Ken’s many attributes and achievements, and here I would like to reiterate these and thank him again for his devotion to the health of the rheological world. Roger To close, I need to say a few words about the Institute of NonNewtonian Fluid Mechanics. Ken was the prime mover in establishing the Institute almost 25 years ago, and one of its key roles is to bring together active researchers in the field through the organisation of workshop conferences. In this it has been extremely successful, attracting high quality talks from speakers from around the world. I’m sure my Institute colleagues would agree that this is entirely down to Ken, for without him, there would have been no Institute. So a big thank you, Ken, from all your Institute colleagues. It has been a pleasure and privilege working with you all these years and we look forward to your continued leadership of the Institute for many years to come. We wish you a very happy 80th birthday. Peter Townsend (on behalf of all your friends in the Institute).
Contents lists available at ScienceDirect
Journal of Non-Newtonian Fluid Mechanics journal homepage: http://www.elsevier.com/locate/jnnfm
Professor Ken Walters at 80 I first met Ken Walters in 1964 as an undergraduate member of his hydrodynamics class, going on later to become one of his early postgraduate students. Those were exciting times at Aberystwyth, where Ken led pioneering work, both experimental and theoretical, including some of the first computer simulation predictions. Over the years the Aberystwyth group grew to be a leader in the rheology community, attracting visitors from around the world. In 1994, Elsevier dedicated a special issue of the Journal of Non-Newtonian Fluid Mechanics (Volume 54) to Ken on the occasion of his 60th birthday and I was privileged to write a tribute to Ken as an introduction to that volume. Well he was nearing retirement wasn’t he. What a ridiculous idea. Twenty years later he is still publishing research papers and giving plenary lectures.
searched for Rheology’s missing link, a model which is simple enough to lead to tractable boundary-value behaviour in simple rheometrical flow situations. The undoubted failure to find such a model up to the present time is one of the sorrows of some of us who have invested a lifetime’s research in the field. However, the discovery of the Boger constant-viscosity highly elastic liquid has recently given renewed hope in this direction at least for a small sub-set of real elastic liquids, with the side effect that some of the early analyses for simple fluid models may not be as obsolete is their dating would suggest.’’
In 1994 I wrote: ‘He(Ken) is not only a brilliant researcher himself, but also a great motivator of others. A whole host of his past research students owe their careers to the start given to them at Aberystwyth. There will be few indeed in the rheology community at large who have not benefited in some way from his contributions, whether it be through the Journal(JNNFM), through the host of courses to which he has contributed, and through the many different meetings he has organised’
Conceived, initiated, and driven to completion by Ken was the book Rheological Phenomena in Focus (1993). The same enthusiasm and drive saw the completion of two DVDs produced by the Institute of Non-Newtonian Fluid Mechanics: Boger Fluids in 2004 and Yield Stress Fluids in 2008.
That statement is even more true today, for he remains a very active member of the community. I considered approaching some of Ken’s collaborators for their memories but the list of names just grew and grew. I’ve chosen just three particularly close collaborators: David Boger, Marcel Crochet and Roger Tanner. To the many who would have wished to contribute to this introduction, I must apologise for it would take a significant volume in itself to record the recollections of each one. David writes: Ken has been a friend and mentor for as long as I can remember. He really is the brother I never had. I was aware of Ken’s reputation as early as 1971 when I arrived at Aberystwyth unannounced while visiting Manchester University. Unfortunately he was not there (travelling, as usual) and I was entertained by Mervyn Jones. The first formal meeting was in 1974 at the Theoretical Rheology meeting at Cambridge University organised by Ken and Anthony Pearson. The most important event in my career was an IUTAM symposium on Non-Newtonian Fluid Mechanics organised by Marcel Crochet in Louvain-la-Neuve in 1978. The scientific committee for the meeting was Marcel, Ken, Ronald Rivlin, and Hanswalter Giesekus. Here we presented our observations on elastic effects in creeping flow in a 4 to1 contraction where the experimental observations were made with constant viscosity elastic fluids (JNNFM 3(1), 87-91 (1977)). The 4 to1 contraction later became a test problem for the Numerical Simulation community and the workshops that were held annually thereafter. At this meeting Ken highlighted our work when he said in his Plenary introduction to the conference: ‘‘Researchers have
Since the Louvain-la-Neuve meeting I have enjoyed many activities with Ken, including presentation of intensive courses in Belgium, Italy, USA and Australia. Other lecturers in these course included H. Giesekus, B. Bird, M. Crochet, G. Marucci, Z. Tadmor and O. Hassager.
Over the years I have enjoyed many, many visits to Aberystwyth, hosted by Ken and Mary, kicking the bar on every occasion, and have thoroughly enjoyed the annual Easter meeting of the Non-Newtonian Fluid Mechanics Institute. There have been some amazing dinners at country houses and of course I have followed Ken, with others, on many occasions in search of ice cream. Some of my most memorable experiences, however, were when travelling with the Welsh Mafia (Peter Townsend, Russell Davies, Eirian Jones). On one such occasion we met in Seattle, Washington, rented cars and travelled for days to the American Society of Rheology meeting in Sacramento, California. What happened on these trips has stayed and will stay on these trips. Ken has had a great career with many achievements and awards but really the greatest achievement of all was marrying Mary; she has been a fabulous support. ‘‘Behind every great man is an exhausted woman’’. Well done, Mary. Happy Birthday Ken. I wish I could have attended the meeting in your honour. David Marcel writes: Ken and I must have met for the first time in 1975 on the occasion of a symposium in Toulouse. We discovered a common desire to go past the analytical calculation of Poiseuille and Couette flows of viscoelastic fluids and to use numerical methods for simulating and understanding more complex experimental observations. Ken had the great advantage of combining experimental expertise – he was just publishing his bestseller ‘‘Rheometry’’ – and high level mathematical training.
Professor Ken Walters at 80 / Journal of Non-Newtonian Fluid Mechanics 222 (2015) vi–vii
We sympathized immediately and we began to cooperate and exchange information. Soon, Ken invited me to visit Aberystwyth. A wonderful expedition at the time! Flight to London, train to Birmingham, Wolverhampton and finally Aberystwyth on a single track – I was told that the train drivers were exchanging a baton – before landing at the Bellevue Hotel where I could hear the seagulls crying on the waves. These visits were great days! Meetings in Ken’s office with members of his research team, seminars, discussions with Ph.D. students, visit to the lab to observe the latest experiments. Ken is a wonderful host. I remember the nice lunches offered by Mary at Pen-y-Graig, dinners in a recently recommended pub followed by a walk on the seafront to ‘‘kick the bar’’. The atmosphere was very relaxing, despite the fact that Ken, a hard worker, must have endured some stress over all these years – publishing a book, advising a team of Ph.D. students, launching and editing a very successful journal, giving lectures all over Europe. Our respective visits to Aberystwyth and Louvain-la-Neuve would continue for many years, fed by numerous participations to Ph.D. committees and also lectures at the Von Karman Institute near Brussels. In the mid-seventies, the challenges in non-Newtonian fluid mechanics were such that it was decided to hold a IUTAM symposium on the subject in Louvain-la-Neuve in 1978. The scientific committee was composed of Ken, Ronald Rivlin, Hanswalter Giesekus and myself. Ken was of considerable help. He had a deep knowledge of who were the pioneers in the field and he knew everyone. We were anxious at the time to progress in the field of numerical simulation, all excited too by the extraordinary films which David Boger had just produced, exhibiting unexpected flow bifurcations. The IUTAM symposium became the origin of the ‘‘Workshops on numerical methods in viscoelastic flow’’, of which some of the major participants were the Welsh team (Ken, Russel Davies, Peter Townsend and several others), Roger Tanner, Bruce Caswell, David Boger. . . A couple of years later, it was Ken’s idea to coauthor a book on numerical simulation with Russel and myself. It was particularly exciting to exchange and comment on the presentation of constitutive equations, confronting the Oldroyd school to the ‘‘simple fluid’’ theory of Coleman and Noll. We met several times before completing the book. The field was progressing month after month (and of course it continued after its publication in 1984), requiring frequent modifications, while Ken’s secretary was typing under his supervision a very difficult manuscript. The decade which followed was marked by a continuous exchange of information, new topics fed by Ken’s imagination and curiosity, such as interfacial effects which led to a joint publication, lectures for the benefit of Polyflow customers in Japan, where I remember Ken being a complete evening on a diet because he could not possibly eat a fish so fresh that its eyes were blinking. My own life reached a bifurcation point in 1995 which prevented me from pursuing my scientific career. While we maintained the friendly relationship that we had built over the years, I missed the professional exchange which was so enriching. I am however fully aware that Ken has pursued his scientific leadership associated with the friendliest presence. Thank you, Ken, and Happy Birthday ! Marcel.
vii
And finally, Roger writes: As far as I remember. I first met Ken around 1958 during a visit to Professor Oldroyd in Swansea, where Ken was doing his PhD. I was also doing my PhD (in Manchester) and I had begun to read Oldroyd’s seminal papers and needed some help. Our next meeting, I believe, was in 1963 in Providence, Rhode Island during the Fourth International congress on Rheology where we read papers and had a good time. I recall Ken visiting me at Brown University later, about 1974. At that time he was promoting the founding of the JNNFM and he asked me what I thought of the idea, citing some opposition to the concept from existing fluid mechanics journals. Typically, he made his case and the JNNFM began in 1976 and continues to gather strength. We met many times after that and my wife and I were the recipients of much generous Aberystwyth hospitality from Ken and Mary. A vivid memory of ‘younger Ken’ is from the 1984 (Mexico) International Congress where he was often seen in the annular swimming pool or at the island bar in the centre where they dispensed coco-locos, pina coladas and other exciting drinks. (This sort of scene was not possible when Ken organised the 2000 International Congress in Cambridge, even though the weather was good by British standards). We wrote a book entitled ‘Rheology: An Historical Perspective’ (Elsevier 1998) and I have commented on this experience in the British Society of Rheology Bulletin (Vol 53, No 3 2012,pp 91-96), showing that Ken can be a slave-driver in these situations. The other document we wrote together was a chapter entitled ‘ The motion of a sphere through an elastic fluid’ pp73-86 in a book edited by R.P. Chhabra and D.De Kee entitled ‘Transport processes in bubbles, drops and particles’ published by Hemisphere, New York (1992). The chapter reviewed the progress made in finding the drag on a sphere falling centrally in a tube filled with an Oldroyd-B model fluid.. It seemed easy (no sharp corners) but it proved otherwise. Not until the work of Yurun Fan (JNNFM 84,233-256,1999) was it realised that beyond a critical Weissenberg number of about one the stress field in the wake of the sphere was not able to be converged. Ken stepped down as Editor of the JNNFM in 2002, and since then there have often been two Editors to carry the load. I have already commented in the September issue of the Journal on Ken’s many attributes and achievements, and here I would like to reiterate these and thank him again for his devotion to the health of the rheological world. Roger To close, I need to say a few words about the Institute of NonNewtonian Fluid Mechanics. Ken was the prime mover in establishing the Institute almost 25 years ago, and one of its key roles is to bring together active researchers in the field through the organisation of workshop conferences. In this it has been extremely successful, attracting high quality talks from speakers from around the world. I’m sure my Institute colleagues would agree that this is entirely down to Ken, for without him, there would have been no Institute. So a big thank you, Ken, from all your Institute colleagues. It has been a pleasure and privilege working with you all these years and we look forward to your continued leadership of the Institute for many years to come. We wish you a very happy 80th birthday. Peter Townsend (on behalf of all your friends in the Institute).