Boundary layer(边界层) Although frictional effects in slightly viscous fluid are indeed present, they are confined to a thin layer near the surface of the body, and the rest of the flow can be considered inviscid. (1904, Prandt/)
Chapter 1 Introduction 1.1 Preliminary Remarks When you think about it, almost everything on this planet either is a fluid or moves within or near a fluid. -Frank M. White What is a fluid?