Rocking motion, trajectory and shape of bubbles rising in small diameter pipes
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The trajectory, rocking motion, and shape of a single air bubble rising in water were investigated utilizing the particle tracking velocimetry (PTV) measurement technique. The three components of the velocity and acceleration vectors of the bubble were obtained by employing a stereoscopic technique. This technique allowed for a better description of rising bubble behavior. Four charged coupled device (CCD) cameras at different view angles acquired the view volume images. Two experimental configurations were employed in this study. In the first setup the bubbles were tracked for a duration of 133.3 ms. The viewing area was 24.6 mm high and 18.6 mm wide, so the bubbles trajectories could be determined. In this configuration, the bubbles rose in a stagnant and a laminar water flow. The average equivalent spherical diameter of the bubbles was 3.6 mm. In the second experimental setup configuration, the bubbles were tracked for 66.7 ms, but the viewing area was reduced to 11.0 mm high and 13.0 mm wide. In addition, a combined shadow particle image velocimetry (SPIV) technique was employed. This technique allowed for an accurate description of the bubble shape. The results indicate that the trajectory of the bubbles was zigzag or helical, and the shape was oblate spheroidal. The period of the cyclic motion and the amplitude decreased as a result of the wall effect. The bubbles rising close to the pipe wall have more rotational behavior than the bubbles flowing through the pipe center. This is a consequence of bubble/wall interaction. © 2001 Elsevier Science Inc. All rights reserved.
author list (cited authors)
Ortiz-Villafuerte, J., Schmidl, W. D., & Hassan, Y. A.