Measurement of Liquid Flow Field Using Micro Bubbles Instead of Solid Particles

The authors have studied for the effect of supplying oxygen into water with micro bubbles produced by the shearing method, and found that the micro bubbles are very effective for the oxygen supplying compared with general size bubbles. We also generate micro bubbles which make water cloudy through the pressurizing dissolution method. The average diameter of micro bubbles generated with this method is about 40 micro meters in our laboratory. They are much smaller than those produced by the shearing method, and are the similar size to the tracer or the reflector used to measure the flow field by the PIV or the UVP (Ultrasonic Velocity Profile monitor). Moreover, they are very economical and ecological compared with solid tracer particles. Therefore, we examine to apply micro bubbles generated with the pressurizing dissolution method to the measurement of liquid flow field using the PIV or the UVP. A flow in a square cavity at Re = 1000 was measured using the PIV and the UVP. We could recognize a clear vortex. A flow around a circular cylinder was also measured using the PIV. We can recognize the possibility of micro bubbles for these applications.