Pergamon lilt .I M~tch Fool~ Manulhct. Vol. 38. Nos 5 6. pp. 451 457, 1998 ( 1998 Elsevier Science Ltd. All rights reserved Printed in Great Britain PIE ~O~glJ-Dg:~D{971iJOO~[9-~[ 0890-6955 98 $1900 + 000 Visual Comparators of Propeller Surface Roughness M. A. Mosaad Department of Ship Engineering, Faculty of Engineering and Technology, University of Suez Canal, Port Said, Egypt Abstract: Visualization has played an effective role in supporting many en~neering applications. In this paper, standard reference surfaces taken from actual propellers were measured using a surface profilin~ system. The measurement d~a were then preprocessed and exported to a graphics workstation. For each sample surface, points were selected and input into a geometric modeling and interrogation system, PRAXITELES. These points were then approximated by a non-uniform r~oual B-spline (NURBS) which is the standard format for representing surfaces in modem geometric modeling systems. The surfaces were visualized and can be used as standard visual comparators to assess the roughness of measured manufactured and in-service propeller surfaces. ~" 1998 ElsevierScience Ltd Keywords: Geomelric modeling and interrogation, propeller surface roughness, roughness characterization, visual comparators, visualization. 1- Introcluc~Jon The increase of fluid drag with blade surface roughness is a complicated and expensive phenomenon. A moderate level of propeller blade surface roughness may increase a shipowner's fuel bill by 5% which can be translate into millions of dollars for a sit, nificant fleet. However, the link between surface roughness and fluid drag is as yet imperfectly understood. One of the main reasons is the lack of standardization and method divergence in surface profile characterization. Roughness characterization parameters can be divided into two categories, roughness height parameters and texture parameters. The height parameters most commonly in use for propeller roughness are the center line average, R a, peak to trough height, R t, and ten point height, R z. There are many texture parameters which can be used to characterize the surface roughness [1]. This includes the average slope, SI, average wavelength, "ga, and the correlation length, B*. A better parameter is peak count wavelength, :tpc, or the peak count per mclL Pc- It is generally agreed that one height and one texture parameter are probably sufficient to correlate surface roughness with fluid drag. A stylus insmanent commonly used to measure blade surface finish provides two parameters Ra, and Pc, which can be used in diydock. For the measuremem of propeller surfaces, a standard procedure has been developed [2] using Ra as a height parameter and Pc as a texture parameter. Any more detailed analysis of in-service propeller surfaces would involve a replication technique [3] and laboratory ~trumentation. 451