Plate roughness and hydrodynamic drag

Previous work on plate roughness and hydrodynamic drag is critically reviewed. Much disagreement is suggested to be due to confusion between definitions and imperfect understanding of the nature of surface roughness. Some common problems of surface roughness measurement, ambiguities and inadequacies of description are discussed. Current experimental measurements of flow and roughness are described for a number of plates coated with ablative paint. Velocity profiles are determined by laser Doppler anemometry in an open flume water channel (20 m in length), while roughness is measured with a computerized stylus instrument. Drag characterization is based on the velocity similarity laws. Results are compared with an existing correlation; fair agreement is found, but some deficiencies of the correlation itself emerge. © 1982.