Characterization of a Bubble Curtain for PIV Measurements - Selected Topics of Computational and Experimental Fluid Mechanics - page 254

better resolution was needed. Also, because the motion of the bubbles is not strictly
vertical, a more detailed characterization of the curtain was required.
3 Methodology
A new device that allowed control of the size and number of the generated bubbles
was developed. Very small, equally sized holes were made on a tube using a laser
cutting machine. One end of the tube was sealed, and the other was connected to a
continuous supply of air. To create an almost uniformflow inside the bubble generator,
an inner tube was introduced as shown in Fig. 4 .
The characterization of the bubble curtain was conducted in the wave flume at the
“Coast and Ports Laboratory” at the Engineering Institute of the UNAM, where the
environment is controlled. A video camera with a speed of 120 frames per second
was used. To ensure a constant flow of air, the pressure is monitored with a mercury
manometer connected between the air pump and the bubble generator as shown in
Fig. 5 .
The study was divided into three stages. First, the behavior of bubbles generated
by one hole was analyzed. Bubbles have a spiral trajectory as they travel upwards.
Fig. 4 Diagram of the bubble generator
Fig. 5 Experimental setup to characterize the behavior of the bubbles