References

changes in the basic flow structure as the wall roughness is varied. Probably the most important reason for this is the fact that the roughness elements occupy the region where turbulence is produced in the smooth pipe by the three-dimensional streaky structure observed by Kline, et al. [19]. Moreover, the possi-bility of structural changes in going from the transition regime to the fully rough flow regime has been indicated. Descriptions of these various changes in the flow structure, as determine