Modelling roughness in scale models

Abstract

Physical hydraulic scale models are valuable tools for engineers to use when solving complex hydraulic problems. Several manuals exist to aid engineers in appropriately modelling a hydraulic structure; however, information on modelling hydraulic roughness in the current literature is scattered and incomplete. To assist the engineers in properly representing hydraulic roughness from a prototype to a scale model, a systematic approach was compiled from the available literature. A thorough literature search demonstrated that some important information was presently not available. This study investigates the hydraulic roughness scaling equations for Manning's n, focusing on accuracy and the limitations of these equations. The results of this study show that the use of these roughness scaling equations is limited to cases where prototype and model operate in the fully rough flow regime. Additionally, a procedure was developed to predict the hydraulic roughness coefficient of artificial roughness materials used in physical models.