The relationship between the pressure drag of a Tayler-Couette flow over rough structures including semi-sphere shaped, conically-shaped and painting irregularly distributed on a wall surface was investigated experimentally. A concentric cylinder device composed of an inner test cylinder and an outer cylinder was employed. The 2-dimensional roughness height of painting surfaces are measured by inline profile measuring instrument, and the roughness curve and the probability density function (PDF) of 2-dimensional roughness height can be obtained at the same time. Then, the 3-dimensional roughness surface can be modeled by the “Set of Multi dispersed Cone Model” which is characterized by the PDF of 2-dimensional peak heights. The PDF of 3-dimensional roughness can be calculated based on bayesian estimation method. After that, the total friction irregular roughness surface can be estimated by summing the contribution of cones composing the SMCM. For the verification of estimation, the estimated value was compared with the measured friction. As a result, it was found that prediction results of five cylinders with sand-grain type roughness by present estimation method agree very well with experiment results, except for one cylinder with relatively smooth and long wave length wavy.

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