Experimental and numerical investigation of coherent structures in turbulent wake flows
Abstract
Recent x wire measurements in a plane turbulent wake are presented. Sinuous disturbances at several amplitudes and frequencies were introduced to the wake by oscillating a small trailing edge flap. The Strouhal numbers of the perturbations were specially chosen so that the downstream location of the neutral point (where the spatial amplification rate obtained from linear stability theory vanishes) was well within the range of measurements. The stream wise variation of the half width of the wake and the centerline velocity deficit was dependent on the amplitude level and showed dramatic deviations at large forcing levels from the wellknown square root behavior of the unforced case. The measured coherent Reynolds stressed were observed to change sign in the neighborhood of the location of the neutral point as predicted by linear viscous theory. The numerical simulations of free shear layers and progress towards the wake simulations are also discussed.
 Publication:

Arizona Univ., Tucson Report
 Pub Date:
 April 1987
 Bibcode:
 1987uat..rept.....C
 Keywords:

 Perturbation;
 Shear Layers;
 Trailing Edge Flaps;
 Turbulent Flow;
 Turbulent Wakes;
 Amplitudes;
 Numerical Stability;
 Prediction Analysis Techniques;
 Spatial Distribution;
 Stable Oscillations;
 Velocity Measurement;
 Viscosity;
 Fluid Mechanics and Heat Transfer