Analysis of the turbulent near wake at a sharp trailing edge.

The response of a turbulent boundary layer to the abrupt change in boundary conditions that occurs at a sharp trailing edge is considered using matched asymptotic expansions in the limit of infinite Reynolds numbers. The problem considered is that of a thin, finite flat plate, which is aligned with a constant velocity mainstream flow of infinite extent. Generality of results is a principal objective of the analysis; consequently, the governing equations are first considered without invoking a specific turbulence model. The turbulent near wake downstream of the trailing edge is determined to develop a double structure. A thin inner region near the wake centreline contains the primary effects associated with the change in conditions at the trailing edge; a similarity solution shows that this region grows linearly (to leading order) with distance from the trailing edge. In addition, it is demonstrated the the centreline velocity varies logarithmically with downstream distance, in a manner that is strongly supported by experimental measurements. (A)