Untersuchung von Turbulenten Scherströmungen durch aufprägung Äusserer Störungen

The use of imposed external disturbances to investigate the relationships among the structural elements of turbulent shear flows is examined in a review of published experimental investigations. The cases of a free axially symmetric shear layer and a plane wall boundary layer are considered, and graphs of typical results are provided. It is found that useful information can be obtained in the boundary-layer case by imposing a linear disturbance, while nonlinear disturbances (multiple-frequency excitation and measurement at the combination frequencies or at subharmonics) are required for the free shear layer.