"Making Little Things Count," ME Online Web Exclusive, Oct. 27, 2003

for 10/27/03

The Widening Gap Between Academia and The Practicing Engineer

And what to do about this.

by Sam Yedidiah

While attending the 2002 ASME International Fluids Engineering Conference in Montreal, Canada, I could not help to notice the ever-growing gap between academia and practical engineering.

I was not the only one who felt that way: In a paper presented by Okitsugu Furuya (Reference [1] ), the lecturer told us about the steps adopted by the academic community of Japan, in order to alleviate this problem.

It will take some time, before we shall be able to know, how effective the steps adopted in Japan will turn out to be. I know however for sure that, sooner or later, this problem will also have to be addressed by the engineering communities in all other countries of the world. In this respect, I have some ideas of my own, which I would wish to share with the engineering community.

Both the academician and the practicing engineer are fascinated by the seemingly unlimited possibilities that a sophisticated computer program is offering. This fascination goes so far, that it makes them often forget, that a mathematical equation is not a definition of an absolute law, but an expression of opinion, written in an array of mathematical symbols.

A mathematical expression does not mean that it is based on correct, relevant assumptions, or that it encompasses all of the existing parameters which are capable to affect a given event or process.

A similar possibility seems also to exist in relation to the cooperation between academia and the practicing engineer. The engineering community could benefit by adding to the engineering curriculum a subject that would teach how to translate an academic definition of a problem into a definition accessible to the practicing engineer, and vice versa.

Let us take, for example, the differential equation for the law of continuity of an incompressible liquid. Each term of that equation defines how the velocity varies in the direction of motion, at each end of a minuscule volume of that liquid. If this velocity is different, this means that the distance between these two ends is either expanding or contracting.

Consequently, the differential equation for an incompressible flow, as a whole, is simply a statement that an extension of the dimension of a given volume in one direction is accompanied by a corresponding contraction in one or more of the other directions. Also, this equation tells us that these expansions and contractions are occurring in such a manner, that the volume of the incompressible liquid remains unchanged (i.e., that the sum of these contractions and expansions is equal to zero.).

When defined in a manner described in the presented example, it is easy for the practicing engineer to recognize, how, where, and when the given differential equation is capable to provide a practical solution to a given problem.

Now let us see, how a better understanding between these two approaches may enhance the practical usefulness of the academic approach. We shall consider such a case on an example inspired by the proceeding of the 2002 ASME Fluids Engineering Conference.

Among the many slides presented during that conference, quite a few lecturers have presented a computer-generated picture of the velocity-distribution within the volute of a centrifugal pump. I have not paid attention, whether each of them has used the same computer program, but each of them came up with a velocity-distribution that reminded very much the distribution shown [2] in Fig.1. This flow pattern is in complete agreement with the differential equations, on which the respective program(s) has (have) been based.

The problem is that the actual flow through a volute occurs in the form of a pair of spirals, each similar to the flow presented schematically in Fig. 2.

My experience with centrifugal pumps extends over more than six decades. Still, the only practical application I am able to find for the illustration shown in Fig. 1 is to use it as a decoration on a letterhead. Against this the purely schematical flow-pattern shown in Fig. 2 is pointing towards a problem that could best be handled by an academic approach:

Recent measurements of the flow-pattern within the passages of an impeller of a centrifugal pump [2] lead to the conclusion that the distance a (Fig.2) is capable to affect significantly the performance of a given pump [4]. This conclusion implies that this distance a should be chosen in such a manner as to ensure that the maximum part of the flow which is exiting the impeller-rim should reach the volute-throat before it returns to a diameter that lies below the entrance to the discharge nozzle.

The reason for that conclusion is that the part of the flow, which fails to satisfy the above condition, is forced to make at least one more complete turn around the impeller before it becomes possible for it to exit the pump.

The theoretical justification for that conclusion has been discovered only recently, in the wake of the flow measurements published in Ref. [2]. However, without even knowing that such as condition exists, the pump industry has recognized, as early as over half a century ago, that higher specific speeds require larger distances a. This conclusion is in complete agreement with the most recent findings arrived at as a result of the test results presented in Ref. [2].

The industry has learned about the existence of such as relationship purely by trial and error. However, the magnitude of the optimum size of the distance a depends not only upon the specific speed of the given pump, but also upon a series of additional parameters.

Here, the academic approach is capable of providing the practicing engineer with enormous assistance in applying the recently found effects of the distance a on the performance of the pump. It could provide him with a computer program based on a theoretical analysis plus extensive experimental studies, which would have enabled the practicing engineer to choose the optimum magnitude of the distance a for a wide range of pump geometries and operating conditions.

The discussion presented above also brings to light one of the basic differences between the academic approach and the needs of the practicing engineer. Academia has its hands full in translating physical events or processes into mathematical expressions -- and verifying the correctness of these translations experimentally -- under controlled laboratory conditions. The practicing engineer, on the other hand, has to deal with real-life problems, which occur under a complexity of many secondary influences. This creates an ever-widening gap between these two approaches.

It is doubtful whether this gap could be eliminated completely. However, a means of translating one approach into the other in a manner accessible to the people proficient in each of these two approaches would have been able to narrow this gap significantly.

Of course, the translation from an academic approach into an engineering approach -- or vice versa -- is not always so easy and simple as in the cases presented in this discussion.

First, any translation can be formulated in many different words and sentences. Second, the physical meaning of each equation may be different in different applications. In many cases, such a translation could require the cooperation of a team of experts from several different disciplines. However, once established, the availability of a discipline capable of creating a better understanding between the academic community and the practicing engineer would be of immense help in narrowing the ever-growing gap between these two approaches.

Such an improvement in mutual understanding would undoubtedly reduce the gap between academia and practicing engineering, and even completely stop this gap from widening.

REFERENCES.
1.Furuya O.: " Effort in Change of Engineering Education in Japan" ASME-Paper #: FEDSM2002-31379.

2.Yu, S.C.M. et al.: "The angle-resolved velocity measurements in the impeller passages of a model biocentrifugal pump". Proc. Inst Mech Engrs., Vol 215, Part C, pp.547-568, 2001.

3. Eck, Bruno.: "Ventilatoren" (In German) Springer Verlag, Berlin, 1962, p.197.

4. Yedidiah, S.: "Effect of pump geometry on the flow within a centrifugal impeller". Proc. Inst. Mech. Eng. Vol 216, Part C, 2002 pp.1145-1149.

5. Yedidiah, S.: "Practical applications of a recently developed method for calculating the head of a rotodynamic impeller" Proc. Inst Mech, Eng. Vol.215, pp. 130-131 (APPENDIX 1), 2001.

6. Yedidiah, S.: "Science in the Design of Fluid Machines" ASME-Paper FEDSM2002-31323, (on a CD)

7. Yedidiah, S.: "Centrifugal Pump User's Guidebook" 2nd - Edition: in Preparation.

Sam Yedidiah is a centrifugal pump consultant who lives in West Orange, N.J. He is an ASME Life Member.