An optical technique was developed to make possible a study of the instantaneous structure of the turbulent wall-pressure field. The approach involved the use of real-time laser-holographic-moiré interferometry.
A moiré fringe pattern generated by the holographic method was superimposed on the surface of a specially-fabricated compliant pipe wall. The compliant surface, in response to wall-pressure changes, introduces optical path length changes which are manifested by distortions in the fringe field.
The fringe distortions, observed during flow, were recorded (framed area, 11 mm x 34 mm) by means of medium-speed motion photography. The amplitude of fringe distortion provides a measure of the pressure magnitude at the wall.
A 26.3 mm ID horizontal glass pipline (7.0 m long) supplied with distilled water from a constant head reservoir was used in the study. Photographs taken of the fringe patterns observed at a flow velocity (U) of 0.47 m/sec (Re[sub=d] = 12,300) were analysed.
Results show that the wall-pressure field consists of a positive and negative pressure region. A statistical analysis reveals that the wall-pressure distribution is asymmetrical (Skewness = -0.29).
From an analysis of the pressure patterns, a relationship between the generation of wall-pressure fluctuations and known wall-layer flow characteristics is inferred.
A flow model is proposed to explain some aspects of the wall region dynamics and a mechanism for particle detachment from a wall, during turbulent flow, is also presented. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/24385 |
| Date | January 1982 |
| Creators | Williams, Norman S.W. |
| Publisher | University of British Columbia |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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