Application of Defocusing Technique to Bubble Depth Measurement

The thesis presents a defocusing technique to extract bubble depth information. Typically, when a bubble is out of focus in an image, the bubble is ignored by applying a filter or thresholding. However, it is known that a bubble image becomes blurred as the bubble moves away from the focal plane. Then, this technique is applied to determine the bubble distance along the optical path based on the blurriness or intensity gradient information of the bubble. Using the image processing algorithm, images captured in three different experiments are analyzed to develop a correlation between the bubble distance and its intensity gradient. The suggested models to predict the bubble depth are also developed based on the measurement data and evaluated with the measured data. When the intensity gradient of the bubble is lower or when a bubble is located farther from the focal plane, the model can predict the distance more accurately. However, the models show larger absolute and relative error when the bubble is near the focal plane. To improve the prediction in that region, another model should be considered. Also, depth of field analysis is introduced in order to compare three experimental results with different imaging setups. The applicability of the approach is analyzed and evaluated.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Nuclear Engineering

Department dc:contributor.department

Mechanical Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2017

Author dc:creator

• Mugikura, Yuki

Chair dc:contributor.committeechair

• Liu, Yang

Committee members dc:contributor.committeemember

• Xiao, Heng
• Pierson, Mark A.

• bubble
• depth of field
• defocusing

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10919/78197

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/78197