On the origin of streamwise vortices in a turbulent boundary layer
Abstract
Several experiments have suggested that the streamwise vortices, with their accompanying low momentum streaks, in a turbulent boundary layer have a characteristic spanwise wavelength of approximately lambda ^{+ subscript z} = 100. A mechanism is proposed which selects a comparable spanwise wavelength and produces counterrotating streamwise vortices in a turbulent boundary layer. Examining the equations which describe the small deviation of the velocity field from its timeaverage, it is found that the BenneyGustavsson resonance (Studies in Applied Mathematics 3, 1981) occurs with such a boundary layer velocity profile. It is shown that, as an integral part of this resonance, there is a mean secondary flow which has a spanwise wavelength lambda ^{+, subscript z} = 90 and whose velocities exhibit a counterrotating streamwise vortex structure.
 Publication:

Final Report Dynamics Technology
 Pub Date:
 March 1985
 Bibcode:
 1985dti..rept.....J
 Keywords:

 Flow Distribution;
 Resonance;
 Streams;
 Turbulent Boundary Layer;
 Vortices;
 Environment Effects;
 Low Speed;
 Momentum;
 Nonlinear Systems;
 Origins;
 Rotation;
 Secondary Flow;
 Velocity Distribution;
 Vertical Orientation;
 Fluid Mechanics and Heat Transfer