Experiments on Management of Free-Stream Turbulence

Abstract

The effects of various passive devices (screens, perforated plates, porous foam, and honeycomb-like matrices formed with closely packed plastic drinking straws) on free-stream turbulence and mean velocity profiles are studied in air with hot-wire anemonetry and in water using hydrogen-bubbles visualization. These 'turbulence manipulators' are viewed as operators which suppress the level of the incoming turbulence and generate, primarily through documented instabilities, new turbulences with scales characteristic of the device and its shear layers. In this sense these manipulators can be used to control, manage and/or modify the incoming turbulence flow to yield the one appropriate to the application.