Turbulent flow inside longitudinally corrugated pipes

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.