CHARACTERIZATION OF SANDPAPER ROUGHNESS UNDER A TURBULENT INCOMPRESSIBLE BOUNDARY-LAYER

The work reported here extends the work of Nikuradse on the categorisa tion of surface roughness. Nikuradse's work considered pipe flow, whil st in this paper boundary layer flow is investigated. Important and fu ndamental differences between these two types of flow are shown. An ex periment upon turbulent boundary layers over sandpaper-type roughnesse s enabled a fluid-mechanic categorisation of these surfaces to be obta ined for this flow. This is compared with some shape and size categori sations of the roughnesses from detailed measurements.