# Centennial of the Kármán-Pohlhausen Momentum-Integral Approach

We devote this special collection to Theodore von Kármán and Karl Pohlhausen, whose 1921 sequential papers have laid down the foundations of the momentum-integral approach. Besides adding a new and simple analysis tool to the fluid mechanics repertoire, this approach has proven to be extraordinarily useful in modeling viscous and thermal boundary layers in a wide variety of phenomenological applications. Although other methods of analysis have since emerged, the momentum-integral approach remains one of the most effective and widely taught techniques. It also represents the nearly perfect complement to Prandtl's 1904 formulation of the reduced boundary layer equations, as well as the 1908 self-preserving similarity solution by Blasius, which are counted among the most foundational achievements in boundary layer theory developed at the turn of the century.

Guest Editors: Joseph Majdalani and Chunxiao Xu