Computational fluid dynamics analyses on the hydrodynamic entry length in internal flows

Abstract

In the present numerical study, effects of the shape of the cross-section and their surface roughness on the pipe hydrodynamic entry length have been investigated for various Reynolds (Re) numbers. Standard k-epsilon turbulence model has been adopted to analyze the turbulent flows in circular, square and equilateral triangle cross-sectional pipes. Analyses indicate that the rough surfaces have the shorter entry lengths than that of the smooth surfaces and increasing surface roughness reduces the entry length regardless of the cross-section of the pipes. The equilateral triangle pipes have the longest while circular cross-sectional pipe has the shortest entry lengths. Re number has the significant effect on the entry length and it is seen that the higher the Re number the longer the entry length.