Some Unanswered Questions in Fluid Mechanics

Perhaps a hundred questions are imbedded in this collection. It is an experiment that brings together the contributions of many people. Questions are not widely used in the authors literature. The typical paper in fluid mechanics, or in science and engineering generally, contains not a single question. Some people are clearly reluctant to pose questions for which they have no answers. But the absence of questions is also in part because they are not part of their profession's tradition. Not so in mathematics, where the first question column in a magazine appeared 250 years ago. The custom continues today, e.g. as a regular column in the American Mathematical Monthly. A major hope behind the assembling of the questions in this paper is that they may bring into focus some of the unresolved problem in fluid mechanics. Another hope, of course, is that questions from a variety of fields may stimulate the kind of interdisciplinary ideas juxtaposition has so often spawned in the past. Finally, the authors are curious as to whether questions are potentially more useful or less useful than their current frequency of occurrence indicates.