Unsteady symmetryplane boundary layer and 3D unsteady separation. Part 1: High incidence
Abstract
The symmetryplane laminar boundary layer of an impulsivelystarted ellipsoid of revolution at high incidence is solved to shed light on some basic characteristics of three dimensional, unsteady flows. The governing equations are formally similar to those for the 3dimensional, steady case, so the same method of solution and computer programs previously developed were employed in the present work. The most important result obtained is concerned with the meridional skin friction c(fu). The zeroc(fu) point (at which c(fu) vanishes) does not, as expected, move forward as time increases, instead it remains over the rear body. As t approaches infinity, it jumps to the front nose. This implies that there is no flow separation over the symmetryplane at finite times. In the meanwhile, it is argued that separation must occur on two sides of the body. This situation leads us to propose a new unsteady separation sequence, i.e. an open type separation prevails at earlier times, while a closed type of separation occurs only at the steadystate condition. This sequence presents a sharp contrast to the conventional notion of unsteady separation which consists of a series of closed separations only. Furthermore, this sequence with the time as the parameter is found to be similar to that for previouslystudied steady flows with varying incidences.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 January 1982
 Bibcode:
 1982STIN...8225471W
 Keywords:

 Bodies Of Revolution;
 Ellipsoids;
 Laminar Boundary Layer;
 Three Dimensional Flow;
 Unsteady Flow;
 Boundary Layer Equations;
 Incidence;
 Separated Flow;
 Skin Friction;
 Fluid Mechanics and Heat Transfer