Turbulent swirling water flow with oil droplets

We have carried out measurements of the flow field of swirling water flow with immiscible oil droplets in a horizontal pipe. The swirl is obtained with a stationary vane inside the pipe. The flow is visualized with tracer particles and the images of visualized flow are captured from the side and downstream-end of the pipe with a progressive-scan video camera. The velocity field is measured from the captured images with the velocity gradient tensor method. The experimental results show that the low-density droplets have relative motion to the water flow. The axial mean velocity decreases because the droplets injected into the flow have had lower velocity than the local flow velocity. The periodic pulsative wake flow of some droplets causes the increase in the turbulence intensity.