The Effects of Roughness on Turbulent Boundary Layers
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Date
2014-12-02
Authors
Meng, Fanxiao
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Abstract
In this thesis, the effects of roughness on turbulent boundary layers are investigated by both the experimental and analytical methods. Two aspects of roughness are investigated, including the similarity between the smooth and rough turbulent boundary layers, and the characteristics of the flow over the step changes in roughness. Based on the data from the thesis of Akinlade (2005), the validity of three different kinds of outer scales is examined for the defect law in the context of smooth surface and three different types of rough surfaces. Furthermore, a mathematical relation is derived to further investigate the roughness effects. For the second topic, experiments were performed on a smooth-rough-smooth transition in a wind tunnel using a boundary layer Pitot tube. In addition, the growth rates of internal boundary layer thicknesses are determined using the method of Antonia and Luxton (1971, 1972), and the results are compared with the previous studies.
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Keywords
Turbulence, Boundary Layer, Roughness