Author(s)

V. E. M. G. Diniz & P. A. Souza

Abstract

This paper presents four explicit formulae to calculate the friction factor for all flow regimes present at Moody diagram without iterations, including the critical zone, for four different problems. The first formula is used to calculate the head losses of pipes given its discharges, lengths, diameters, absolute roughness, the kinematic viscosity of the fluid that flows in the pipes and the gravity acceleration. The second formula is used to calculate the discharges of pipes given its head losses, lengths, diameters, absolute roughness, the kinematic viscosity of the fluid that flows in the pipes and the gravity acceleration. The third formula is used to calculate the diameters of pipes given its discharges, lengths, head losses, absolute roughness, the kinematic viscosity of the fluid that flows in the pipes and the gravity acceleration. The fourth formula is used to calculate the diameters of pipes given its lengths, head losses, absolute roughness, the kinematic viscosity of the fluid that flows in the pipes, the fluid velocities in the pipes and the gravity acceleration. The calculated friction factors are used to calculate the discharges, head losses and diameters of pipes for the steady state and for the extended period state. A case study is presented where it was possible to apply the first two formulae to calculate the friction factors for the steady state in a water main with nine pipes. The results show that the two applied formulae are working well because the calculated pressure heads of some nodes of the water main were compared to the pressure heads gauged in situ on the same nodes of the water main and the results were close. Keywords: friction factor calculation, explicit formulae, Moody diagram, four different problems, steady state, case study.

Keywords

friction factor calculation, explicit formulae, Moody diagram, four different problems, steady state, case study