Memory effects in turbulence
Abstract
The wake flow generated by a hemispherical cap on the wall of a constantpressure turbulent boundary layer, and the wake flow of a circular cylinder in a uniform free stream are analyzed numerically. The result is that the extra memory effects are important in both the disturbed boundary layer and the developing part of the wake at short distances from the cylinder. In the first case the eddy viscosity sub m when corrected for the extra memory effect and rendered dimensionless with the local wall friction velocity and boundary layer thickness, still follows the same distribution as for the undisturbed boundary layer. For the undisturbed boundarylayer the extramemory effects are negligible. In the second case the corrected eddy viscosity also becomes quantitatively equal to the constant value of the fully developed self preserving wake flow. It further turns out that the extra memory effects in the self preserving wake flow remain hidden. It is conjectured that in selfpreserving free turbulent flows the extra memory effects are not negligible but are not directly observable because of the selfpreservation.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 September 1975
 Bibcode:
 1975STIN...7625524H
 Keywords:

 Nonnewtonian Fluids;
 Turbulent Flow;
 Viscoelasticity;
 Eddy Viscosity;
 Flow Distribution;
 Turbulent Boundary Layer;
 Velocity Distribution;
 Wakes;
 Fluid Mechanics and Heat Transfer