Measurement of Reynolds Stress Distribution in a Fluidic Element by the Laser Doppler Velocimeter

The one-phase flow and the two-phase flow in a fluidic element are investigated by measuring Reynolds stress distributions of the main jets using the laser Doppler velocimeter. In the one-phase flow, a water flow jets from a main nozzle into water and in the two-phase flow, a water fiow jets into air. Some results with the one-phase flow are as follows. When either of the two control ports is closed without an impedance at the output ports, the jet is influenced with a low pressure vortex in the jet attaching side, so that the shear stress and the longitudinal normal stress in the jet attaching side become larger than those in the jet unattaching side. Then, also the jet engulfs the water flow from the control port and the output port in the jet unattaching side, so that the transverse normal stress in the jet unattaching side becomes larger than that in the jet attaching side. When the control port in the jet attaching side is opened, the jet is not influenced with a low pressure vortex. As a result, Reynolds stresses show symmetrical distributions. When either of two control ports is closed and the impedance of the output port in the jet attaching side increases, Reynolds stresses increase. Then transverse normal stress of those, in the jet unattaching side, increases most. These phenomena are caused with the increase of the spill flow. Some results with the two-phase flow are as follows. When either of the two control ports is closed without an impedance at the two output ports, Reynolds stresses of the two-phase flow are smaller than those of the one-phase flow and are very small especially near the air boundary. This is because the mometum exchange between the water jet and the ambient air is smaller than that between the water jet and the ambient water, so that the water jet diffuses little to the transverse direction in a two-phase flow. With the increase of impedance at the output port in the jet attaching side, Reynolds stresses increase little, for the air arround the jet prevent it to engulf a spill water flow.