Turbulent flow inside longitudinally corrugated pipes

Abstract

Longitudinally corrugated pipes can be described as pipes with periodically converging-diverging cross-area arranged along the flow course. These pipes are mainly utilized in engineering applications, for example, pipe flow in a heat exchanger where wall corrugation improves heat convection,gas to liquid contractors in the chemical business, ventilation, air conditioning, drag reduction and mass transfer efficiency. Both experimental and analytical works detailed the impact of corrugation amplitude and distance in the turbulent flow by investigation of a few turbulent characteristics,for example,Reynolds stress and velocity variation. In our examination, we are concerned in assessing friction factor for turbulent flow inside longitudinally corrugated pipes as a function of the amplitude of the pipe. Mass and momentum conservation equations are reviewed and particular boundary conditions are fixed to describe a completely developed periodic system in a solitary axisymmetric bidimensional module which signifies the periodically corrugated pipe configuration. Two two-equation turbulence models (k− andk−ω) are utilized in the calculations. The numerical simulation of the isothermal, single phase and incompressible flow is prepared utilizing Computational Fluid Dynamics methods, using the commercially available CFD software ANSYS FLUENT. To begin with, the completely developed turbulent flow in a smooth pipe is studied. Simulations are carried out to authenticate the preferred models, computational meshes and boundary conditions. Next a longitudinally corrugated pipe of length 7λ is studied. Impact of surface corrugation, controlled by wavelength-amplitude proportionλ/a on the flow is exhibited. The simulation work has been completed forλ/a = 1, 11 and 19 for a Reynolds number range of 10 000 to 20 000. Flow phenomena like flow separation and vortex caused by the corrugation are described. The friction factor for various values of the wave length is calculated by operating aset of simulations. The friction factor for a given Reynolds number in a longitudinally corrugated pipe decreases with increase of the wavelength.