Small-probe-volume laser Doppler anemometry measurements of turbulent flow near the wall of a rib-roughened channel
✍ Scribed by S.R. Martin; C.J. Bates
- Publisher
- Elsevier Science
- Year
- 1992
- Tongue
- English
- Weight
- 639 KB
- Volume
- 3
- Category
- Article
- ISSN
- 0955-5986
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✦ Synopsis
A special-purpose high-resolution laser Doppler optical system has been used to investigate the wall region of a turbulent water flow within a rectangular channel. The exceptionally small control volume (30 I~m x 17 I~m x 15 pom) has enabled unique LDA measurements to be achieved on two walls of the channel: one a plane smooth wall and the opposite one a rib-roughened wall. The plane wall measurements agree well with existing classical sublayer/bufferzone concepts. However, for the first time the near-wall experimental measurements between two successive ribs show that reattachment to the channel floor between the ribs may never be achieved for this particular geometry. Previous measurements on this geometry by using relatively large control volumes are therefore misleading. In view of this observation it is not surprising that the existing numerical models have difficulty in accurately predicting points of reattachment and separation for these types of geometries.