On the Control of a Development of Turbulent Pipe Flow by a Ring-Type Manipulator

As a device in order to obtain a fully developed turbulent pipe flow as early as possible, a ringtype manipulator with a rectangular cross section was used. The experiment was performed in the situation where an air was flowing at Reynolds number of 9×104. Ring-type manipulator were placed immediately downstream of a bellmouth entry at 3 positions, which are on the pipe wall, the outer edge of turbulent boundary layer and in the potential core region. The mean flow field behind the manipulator in a smooth pipe has been investigated by measuring the wall static pressure and longitudinal mean velocity. From the results, the streamwise change in the boundary layer characteristic values suggests that the recovery distance from the ring disturbance is shortest when the manipulator is at the outer edge of the turbulent boundary layer.