Book Description

Measurements of cross-stream and streamwise vorticity have been made over important regions of an experimental simulation of the bursting process of turbulent boundary layers. Vorticity measurements have also been made of the starting vortex of an airfoil, in a vortex ring, and in a Stokes' layer. Using a new technique developed under this contract, these measurements have been made at approximately fifty simultaneous positions over the flow structures of interest. The technique can accurately measure vorticity and strain rate, as well as instantaneous Reynolds stress and velocities over a field. It requires only a clock and ruler for calibration. It also directly measures these quantities, avoiding indirect interpretations. It uses long time persistence of irradiation of a photochemical to mark fluid particles. The technique has been named LIPA, (Laser Induced Photochemical Anemometry). Its accuracy has been measured by comparing it to an exact solution of the Navier-stokes equations. This indicated an absolute accuracy of cross-stream vorticity of + or - 1 sec. Data reduction procedures have been developed which use high resolution digitization and image processing. Algorithms have been written and tested which allow almost complete automation of the data reduction procedure. (EDC).