An experimental study of an axisymmetric turbulent boundary layer disturbed by a periodic free stream

Behavior of an axisymmetric equilibrium turbulent boundary layer disturbed by a propeller wake in the freestream was investigated experimentally. Tests were conducted in a low speed wind tunnel and measurements of turbulence quantities were made using an X wire probe and a constant temperature anemometer. The boundary layer flow on a cylindrical body was characterized by measuring its gross parameters and comparing them with classical values. Propeller speed was measured using an electronic circuit whose output signal was also used to trigger hot wire probe. Gross boundary later characteristics of the disturbed boundary layer did not deviate appreciably from the classical two-dimensional turbulent boundary layer except immediately behind the propeller. From conditional sampling it was found that the near wall periodic Reynolds stress approached 30% of the conventional time averaged Reynolds stress. Turbulent kinetic energy, kinetic energy of the organized field and various kinetic energy production terms responsible for exchange of turbulent kinetic energy between different flow fields were calculated from the experimental data. It was found that kinetic energy was being transferred from the organized flow field to the "random" turbulent flow field, as expected. The variation of both periodic and turbulent kinetic energy were governed by similar equations. A mechanism for the transport of turbulent kinetic energy has been suggested.