Westward Ho! Musing on Mathematics and Mechanics

摘要

Reflecting on an encounter with the Bath, Wiltshire and North Devon Gliding Club during a pleasant afternoon's walk around the Deverill valley, Alan Champneys ponders how aircraft actually stay in the air. This would seem a simple question,one whose answer is covered in A-levelphysics textbooks, and is drummed into successive cohorts of first-year undergraduate aerospace engineering students. Yet, digging a bit deeper, these simple explanations seem to differ widely. In each, many of the same words occur; Newton's second law, Bernoulli's principle, pressure differentials, boundary layers, vorticity, etc. Yet no single explanation really suffices, and some are just plain wrong. The real answer, as it often is, appears to be more subtle and gives us another glimpse at the complexity of fluid mechanics. This leads to an observation on the role of mathematical modelling both in aiding engineering design and in enabling simplified scientific explanations.