Prandtl, the advisor

In the last months I have sustained that, unfortunately, advisors and supervisors in Universities are not real researchers and that, in my experience, they hardly go into the lab once they get their position. I assume that papers are cosigned in occasions by people who scarcely know the details of the experimentation of the topics in the publication, if not the complexities of the theory. Advisors and supervisors play the role of managers and strive to keep in motion the machinery of their living.

As opposed, I normally mentioned the example of Ludwig Prandtl: a photograph of his in his laboratory of the University of Gottingen, bent over his water tunnel, watching diverse motions of the fluid. He is a man of smart, neat aspect, well into the middle-age (see, first page here). I could only with difficulty imagine nowadays advisors looking so thoroughly at something that basic in the lab, at that point of their lives and careers, and so I did point it out.

However, I read what Von Karman, a graduate student with Prandtl in the old ages, wrote about the water tunnel in his Aerodynamics (1954). Read this, and tell me what conclusions you extract. I can see through it that Pradtl looked rather like a distant man from his graduate student, who build and operate the water tunnel; the student was doing and apparently stupid and childish thing to further prove the break-through work of his master: drag a cylinder suddenly from rest within the fluid in steady motion at speed V; and that, from this apparently childish occupation, even a big mind like Prandtl's fail to recognize (insist: from the observation of Nature) a well-sustained phenomenon, known later as Von Karman vortex sheet, although a very unexpected one:

"(...) Prandtl had a doctoral candidate, Karl Hiemenz, to whom he gave the task of constructing a water channel in which he could observe the separation of the flow behind a cylinder. The object was to check experimentally the separation point calculated by means of the boundary-layer theory. For this purpose, it was first necessary to know the pressure distribution around the cylinder in a steady flow. Much to his surprise, Hiemenz found that the flow in his channel oscillated violently.

When he reported this to Prandtl, the latter told him: 'Obviously, your cylinder is not circular'.

However, even after very carefully machinery of the cylinder, the flow continued to oscillate. Then Hiemenz was told that possibly the channel was not symmetric, and he started to adjust it.

I was not concerned with this problem, but every morning when I came in the laboratory I asked him, 'Herr Hiemenz, is the flow steady now?'

He answered very sadly, 'It always oscillates' ".

(Von Karman, T., 1954: "Aerodynamics: selected topics in the light of their historical development". Cornell University Press, Ithaca, New York).

I can see the episode described in the last paragraphs, so familiar, so universal.

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