J. D. Jackson
Centre for the History of Science, Technology & Medicine

Osborne Reynolds



The occasion of the centenary of the publication by the Royal Society of the paper `On the dynamical theory of incompressible viscous fluids and the determination of the criterion,' is an opportune moment to consider not only the paper itself but its place within the broader context of the complete works of its author, Osborne Reynolds. As a landmark contribution to the development of fluid mechanics the 1895 paper is without question the crowning achievement of Reynolds' long and distinguished career as the first Professor of Engineering at the University of Manchester. Indeed, the fact that one hundred years later the ideas contained in his paper remain central to current turbulent research and are widely used in the study of practical flows provides ample cause for celebration and underlines the continued relevance of this contribution.

By means of a detailed examination of his body of work I hope to disclose not only the development and emergence of the lines of thought so definitively realised in 1895, but also give something of an overview of Reynolds' many and diverse scientif ic interests. Consequently, I have sought to categorise the considerable output of published material Reynolds produced during his thirty-seven years at Manchester (1868-1905) and to offer a short review, highlighting those contributions which have proved to be of particular importance.

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Biographical Overview

What follows is a very brief biographical outline. Those who are interested to learn more about this may do so by reading the excellent paper by Professor Jack Allen [1], based on the invited lecture which he gave in August 1968 at the Symposium held to celebrate the centenary of Reynolds' appointment to the newly established Chair of Engineering at Manchester. Further insight into his life and work can be gained by viewing a permanent exhibition in the School of Engineering at Manchester featuring original equipment constructed and used by Reynolds. Working reproductions of a number of his experiments are available for `hands on' use, whilst general display boards provide visitors with additional biographical information.

Osborne Reynolds was born in Belfast on August 23rd, 1842. He came of a clerical family. His great-grandfather and grandfather were rectors of Debach-with-Boulge, Suffolk, while his father, the Rev. Osborne Reynolds, was a Fellow of Queens' College, Cambridge, Principal of the Belfast Collegiate School, Headmaster of Dedham Grammar School, Essex, and finally also Rector of Debach.

Reynolds' early education was undertaken mainly by his father, who in addition to being an extremely able mathematician had a keen interest in mechanics and mechanical matters and took out a number of patents concerned with improvements to agricultural equipment and machinery. The young Osborne Reynolds showed an early aptitude and liking for the study of mechanics and, at the age of nineteen, entered the workshop of Mr. Edward Hayes of Stony Stratford, a well known inventor and mechanical engineer. He remained with Edward Hayes for a year obtaining practical experience in the manufacture and fitting out of coastal steamers. During this period, to use his own words,

`my attention (was) drawn to various mechanical phenomena, for the explanation of which I discovered that a knowledge of mathematics was essential'.
He therefore decided to go to Cambridge to take a course in mathematics. His university career was highly successful. He graduated in 1867 and was immediately afterwards elected to a Fellowship at Queens' College. He then entered the office of a civil engineer, Mr. John Lawson, of London.

In 1868 he applied for and was elected to the newly instituted Chair of Engineering at Owens College - later to become The Victoria University of Manchester. In his application for the post Osborne Reynolds stated, `From my earliest recollection I have had an irresistible liking for mechanics and the physical laws on which mechanics as a science are based. In my boyhood I had the advantage of the constant guidance of my father, also a lover of mechanics and a man of no mean attainment in mathematics and their applications to physics'. He remained as Professor of Engineering at the University of Manchester until 1905 and died on February 21st 1912 at Watchet in Somerset at the age of sixty-nine.

He was awarded the degree of M.A. by the University of Cambridge in 1880 and elected Honorary Fellow of Queens' College Cambridge in 1882. In 1877, he was elected a Fellow of the Royal Society and in 1888 received the Royal Medal. In 1883, he became a Member of the Institution of Civil Engineers and was awarded the Telford Premium in 1885. The University of Glasgow conferred the Honorary Degree of LL.D. on him in 1884. He was elected President of the Manchester Literary and Philosophical Society in 1888 and received the Dalton Medal in 1903. His collected works were published by Cambridge University Press in three volumes with the title `Papers on Mechanical and Physical Subjects' (Volume I in 1900 [2], Volume II in 1901 [3] and Volume III in 1903 [4]). These contain most of his published papers, over seventy in all.

Osborne Reynolds was one of the most original and independent of men and had strong views as to the character of the training to be offered in this new discipline. He consequently organised a systematic course of lectures extending over three years which provided a thorough grounding in civil and mechanical engineering. In his view all engineering was one so far as the student was concerned, and the same essential training should be given irrespective of the type of specialisation to be pursued afterwards.

Osborne Reynolds' considerable mathematical ability was supplemented by an almost uncanny insight into the physical fundamentals of a problem. Shortly after coming to Manchester, Reynolds began a series of original researches which led, during the next thirty- five years, to the publication of many papers of outstanding interest. These covered a phenomenally wide range of physical problems and engineering applications and laid the foundations for much of the subsequent work on turbulent flow, hydraulic modelling, hydrodynamic lubrication, friction, heat transfer, and many other matters. His experiments on the origins of turbulence, the scaling of estuary models and the determination of the mechanical equivalent of heat remain classics of their kind. One is frequently reminded of the importance of his work in fluid mechanics and heat transfer by the widespread use of terms such as the Reynolds Number, Reynolds equations, Reynolds stresses and Reynolds Analogy. His study of turbulent transition in pipe flow `An experimental investigation of the circumstances which determine whether the motion of water shall be direct or sinuous and of the law of resistance in parallel channels' was one of the many highlights of Reynolds' research. The original Reynolds Tank experiment, which is still in use at Manchester University for demonstrating this key aspect of fluid mechanics to students, is no less than an object of pilgrimage for visitors.

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His Inaugural Lecture and Early Days at Owens College

It was the custom for the Academic Sessions at Owens College to be inaugurated by an Introductory Address. This task was entrusted to Osborne Reynolds for the opening of the Session 1868-69, the start of his career at Manchester. In this lecture, revealingly entitled `The progress of engineering with respect to the social conditions of this country' [5], he firmly rejects any notion of engineering as an `ivory tower' abstraction divorced from human context:

`The results, however, of the labour and invention of this century are not to be found in a network of railways, in superb bridges, in enormous guns, or in instantaneous communication. We must compare the social state of the inhabitants of the country with what it was. The change is apparent enough. The population is double what it was a century back; the people are better fed and better housed, and comforts and even luxuries that were only within the reach of the wealthy can now be obtained by all classes alike... But with these advantages there are some drawbacks. These have in many cases assumed national importance, and it has become the province of the engineer to provide a remedy.'

Made at the outset of his career these remarks show the youthful Reynolds clear in his mind as to what needed to be done, a figure charged with a sense of mission and full of ideas.

The Chair of Engineering at Owens College had been established by eminent local engineers and businessmen with a view to providing a source of well-educated young men trained in science and engineering. The hope was that they would take up employment in the Manchester area and feed ideas and initiatives into the many industrial organisations there in order to help to combat stiff competition from elsewhere, notably Germany and other parts of Europe. In those places industry was already benefitting as a direct result of the creation of teaching establishments which provided technical education to a high level. The major industrialists Joseph Whitworth, William Fairbairn, Charles Beyer and John Robinson all played a leading role in the foundation of the Chair at Manchester and in the selection of the 25 year old Osborne Reynolds to fill it.

At the time Reynolds arrived in Manchester in 1868 Owens College was housed in a building in Quay Street which had earlier been the home of Richard Cobden, the renowned former Member of Parliament for nearby Stockport. Little was available to him in the way of laboratory facilities for either teaching or research. Initially, he was restricted to research involving experiments of a very simple kind which could either be done at home or outdoors. We see this clearly reflected in the emphasis of his early work. It was not until much later, well after 1873 when Owens College moved to the present site of the University of Manchester in Oxford Road, that Reynolds was able to undertake experiments using sophisticated apparatus and it was even later before he had laboratory facilities which enabled him to perform tests on engineering plant.

In November 1869, Reynolds became a member of the Manchester Literary and Philosophical Society. At that time the President of the Society was the distinguished scientist James Prescott Joule, a man for whom Reynolds came to have the very highest regard. It was under the latter's encouraging eye that Osborne Reynolds read his first paper to the Literary and Philosophical Society in March 1870 on `The stability of a ball above a jet of water' (an interesting but rather academic problem). It marked the beginning of a close involvement with the `Lit. & Phil.' on Reynolds' part and he contributed papers regularly, a total of twenty-six in all. These were mainly on scientific topics of general interest and broad appeal to members of the Society.

In a successful bid to further extend both his own and the College's contacts with the scientific community of the area, Reynolds also actively involved himself with two other local societies, the Manchester Association of Employers, Foremen and Draughtsmen (a group consisting of men with technical interests and experience, first formed in 1856) and the Manchester Scientific and Mechanical Society (formed in 1870 by William Fairbairn with the intention of linking academics with local industrialists). Between 1871 and 1874 Reynolds addressed the first of these bodies on a number of directly practical topics, as their titles make clear: `Elasticity and fracture', `The use of high pressure steam' and `Some properties of steel as a material for construction.' In contrast, his lectures to the Scientific and Mechanical Society, whom he twice served as President, were of a far more general nature, as indicated by titles such as `Future progress', `Engineers as a profession' and `Mechanical advances'. It is interesting to observe how Osborne Reynolds set out to satisfy the specific needs of the rather different sections of his `scientific constituency' in the attentions he paid to the various Manchester societies.

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Reynolds' Contribution to Science and Engineering

The considerable diversity of the problems in both pure and applied science that Reynolds subsequently tackled provides a clear indication of an unusually wide ranging scientific curiosity. Six parallel streams of research falling into two groups and broadly corresponding to the nominal notion of `Reynolds the Scientist' and `Reynolds the Engineer' may be identified.

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Overview - Reynolds the Pioneer

Osborne Reynolds' thirty-seven year tenure at Owens College coincided with major changes in the scientific world, as the age of the gentleman-scientist and the self-taught devotee, embodied at its best in the form of Joule, gave way to that of the university-educated, research group leader such as Rutherford who took up his appointment in Manchester in 1907. Any overview of Reynolds' contribution must be made with this in mind together with the realisation that the ever more refined specialisation of today's complex science was a development that had scarcely started. The not unexpected consequence of this is that the range of Reynolds' interests and involvements has rather escaped general notice, and thus it is with a short summary of his achievements that I propose to conclude.

Firstly, although his name is not widely associated with the furtherance of the kinetic theory of gases, Reynolds' papers dealing with the communication of surface forces due to heating, taken together with his work on the transpiration of gases, arguably provided the first substantive experimental support for the ideas involved. If we add to this his detailed theoretical treatment of the problem of thermal transpiration, the contributions he made in the period 1874 to 1879 to the early advancement of the kinetic theory of gases were clearly of fundamental importance.

A classic example of Reynolds' pioneering work in a sphere far from that of turbulent flow are the two papers he produced on the dilatancy of granular materials, long acknowledged by practitioners of geotechnics but not so well known by those outside the field. The beautifully simple explanation of the mechanism involved in the property of dilatancy provided those working in soil mechanics with an understanding of the behaviour of granular materials which greatly assisted the subsequent development of this particular branch of engineering.

Nonetheless, it is within the field of fluid motion, and in particular turbulent flow, that Osborne Reynolds has received his fullest recognition from the scientific fraternity. His success in identifying the fundamental dimensionless parameter which characterises the behaviour of flowing fluids was unquestioningly a pioneering achievement and is what many people regard as Osborne Reynolds' most valuable scientific legacy. Linked as it is to the stability of flow and the occurrence of turbulence, it is of immense importance. His development of a dynamical theory of turbulent flow coupled with the experimental work on the circumstances under which flow is laminar or turbulent have together provided the true foundations for the subsequent development of the subject. Indeed it is difficult to exaggerate the importance of Reynolds' achievement in engineering fluid mechanics.

Similarly, Reynolds' contribution to another aspect of fluid flow, namely hydrodynamic lubrication, has also had far-reaching consequences. His lengthy and detailed paper on this topic provided a theoretical basis for the understanding and design of bearings which thirty- two years later (in 1918) Lord Rayleigh felt able to assert `includes most of what is now known on the subject'. Taken together, Reynolds' fundamental work on rolling friction and his theory of hydrodynamic lubrication provide ample justification for `the claim that he was indeed the dominant figure in the evolution of the subject of Tribology.' [9]

As we have seen, Reynolds' work in fluid mechanics was not merely confined to fundamental topics. His applied investigations into aspects of marine engineering and naval architecture had considerable impact in their own right. Reported as they were to a Committee of the British Association for the Advancement of Science composed of some of the most distinguished scientists and engineers of the day, Reynolds' conclusions concerning the propulsion and steering of ships had immediate and literally far-reaching consequences. His fundamental and innovative research into the modelling of water flow and sediment transport in rivers and estuaries has likewise had a profound effect, setting the scene for much of the work which has followed in this area.

However, for the earliest and perhaps the most directly practical of Reynolds' contributions we must turn to a little known publication entitled `On sewer gas and how to keep it out of houses' [10] which first appeared in 1872. This could possibly be connected with his time in London at the offices of John Lawson where he was engaged on matters connected with a sewage system for Croydon. His short monograph is a handbook on house drainage which provides the reader with clear and detailed guidance on sanitary systems designed to isolate sewers from houses. A new preface written for the 1876 reprint offers an invaluable insight into its author's practical side:

`The principal part of this book was written nearly four years ago. It has only been waiting in order that some suggestions it contains might have a thorough practical trial, and this being accomplished, it is now published in the hope that it may help those people who are in doubt and trouble with the drainage of their houses. It would be a public calamity if ... wide-spread alarm ... were allowed to subside without producing a beneficial effect; but there is danger that such will be the case, simply for the want of definite information as to what is amiss, and how it is to be set right.'
The booklet rapidly went through four editions and undoubtedly Reynolds' provision of `definite information' had an important impact on subsequent practice.

In the world of engineering heat transfer and thermal hydraulics too, Osborne Reynolds must also be viewed as a pioneer. His very simple experiments on the effect of the presence of air on the condensation of steam had important contemporary implications for the design of engines. Today the topic remains one which occupies the attention of power engineers. Turning next to convective heat transfer, if we take Reynolds' short but extremely important paper on heat transfer in the boiler tubes of steam locomotives, which contains the essence of the analogy between heat transfer and fluid friction, and link it with his study of frictional pressure drop in tubes, we have the basis of the empirical equations currently used in thermal design. Moreover, his invaluable contribution to this field was not simply limited to his own efforts, for his student T.E. Stanton went on to have a major impact on the subject.

Again, if we consider Reynolds `the inventor' then once more we are obliged to recognise a man who consistently went to the `heart' of scientific matter. Nowhere is this better seen than in his 1875 patent, `Improvements in apparatus for obtaining motive power from fluids and also for raising or forcing fluids'. Not only did his innovations provide ideas for the commercial multi-stage hydraulic pumps and turbines which subsequently came into widespread use, but they also led ultimately to today's steam turbines. The simple two-stage steam turbine which Osborne Reynolds designed and ran successfully in 1875 stands today in a showcase at the University of Manchester as a testament to this truly pioneering endeavour.

Reynolds' lifelong pursuit of scientific truth is particularly evident in his final contribution published in 1903 under the auspices of the Royal Society. His paper `On the Sub-Mechanics of the Universe' in which he utilised his ideas on dilatancy to construct a mechanical theory of the ether was certainly a bold and ambitious one. It well illustrates the wide-ranging nature of his interests, his dedication to science and his confidence that the most fundamental of matters could ultimately be explained in simple mechanical terms. Plate 3 shows the very fine portrait of Osborne Reynolds painted by John Collier in 1904 which depicts him holding a tray containing a number of spheres, one of the illustrations used in his Rede lecture on the subject [11]. Sadly, the contents of this intriguing final paper proved to be extremely difficult to appraise and the timing of its publication was such that the ideas contained in it were overtaken by events in the development of Physics.

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At the beginning of this paper I made reference to the excellent, but little known, paper by Professor Jack Allen on `The Life and Work of Osborne Reynolds'. Professor Allen was the Principal Speaker at the International Symposium held in Manchester in 1968 to mark the centenary of the appointment of Osborne Reynolds to the Chair of Engineering at Owens College. In my capacity as Organising Secretary for the Centenary Symposium, I gave Professor Allen what help I could in gathering material for his lecture. In turn he gave me much encouragement in the course of the preparations for the Symposium. I recall with great pleasure the contact which I had with him at that time.

Professor Allen approached the task of preparing his lecture with great dedication and produced what remains today the authoritative work on the life and work of Osborne Reynolds. Jack Allen's paper has been of considerable help to me in the preparation of the present paper. I have made extensive use of his material and wish to acknowledge this fact. I also wish to acknowledge the very considerable assistance which I have had from Dr. Ian Fishwick in researching material used in this paper and also in editing the final version. Finally, I would also like to thank Linda Jefferies, Pei An and Malcolm Firth for their invaluable help in producing the manuscript and diagrams.

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Patent Specifications by Professor Osborne Reynolds:

No. 1878, dated 2nd July 1870 - `Improvements in Machinery for Propelling Ships or Vessels'.

No. 724, dated 27th February 1875 - `Improvements in Apparatus for Obtaining Motive Power from Fluids and also for Raising or Forcing Fluids'.

No. 9603, dated 7th July 1887 - `Improvements in Friction Clutches'.

No. 9604, dated 7th July 1887 - `Improvements in Yielding Couplings for Rotating Shafts'.

No. 10482, dated 28th July 1887 - `Improvements in Hydraulic or Liquid Brakes for Causing and Measuring Resistances on Rotating Shafts'.

No. 781227, dated 31st January 1905, United States Patent Office - `Packing for Pistons'.

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Document written by
Prof. J.D. Jackson
Centre for the History of Science, Technology & Medicine
Faculty of Life Sciences
University of Manchester, Manchester M13 9PL
e-mail: jdjackson@manchester.ac.uk
Web Pages prepared by Dr. J. E. Byrne

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