The role of coordinate systems in boundary-layer theory

摘要: The boundary layer approximation to a given flow problem is not invariant if different coordinate systems are used in the process. However, correlation theorem (Theorem 1) given, which states that solution with respect any system can be found, by simple substitution, from other system. On basis of this theorem, dependence on choice coordinates investigated detail. skin friction invariant, but field invariant. At large distances wall, theory depends almost entirely coordinates, rather than physical problem. This may obtain complete matching between and external flow, following sense: Theorem 2 how found such valid as an for entire field. It contains due displacement thickness. The discussion restricted steady, two-dimensional, incompressible without separation. These restrictions, however, essential many results.