Friction factors and velocity distributions have been measured for a fluid flowing past a rough surface, which formed the core of a rough-smooth annulus. Pressure drops along and velocity profiles across the annulus were measured for annular Reynolds numbers of up to 4 times 104. A transformation suggested by Hall (1)† was then used to isolate the effects of the rough inner surface from those of the smooth outer surface. When the velocity profiles for the rough part of the annulus were plotted in universal form, with all radial dimensions reduced to an effective diameter form, the results agreed well with data for circular pipes. When the friction factor-Reynolds number relationships were compared with those of Nikuradse (2) in his experiments with sand-roughened pipes, it was seen that a close resemblance in the roughness type existed.
