Abstract
Non-metallic flexible pipes are widely used in industry. They are comprised of fabric
wrapped over a spiral metal framework. Due to this construction, they respond very well
to bending and they are cheaper and much easier to install than metal pipes. Because of
the specific construction, the pipe walls are corrugated and the fabric which covers the
steel spiral is much rougher than the wall of a metal pipe. In this investigation we are
interested in estimating the friction factor for the flow in this type of pipes.
Two-equation turbulence models (k -?? and k -!) are used in the computations. The
process of deriving these models is presented first. Then we look at turbulent boundary
layers and the law of the wall which gives the velocity profile near the wall. Its use as a
boundary condition is explained.
After the theoretical ideas have been exposed, we look at fully developed turbulent flow
in a conventional pipe. Simulations are performed to validate the chosen models, boundary
conditions and computational grids. Then a new boundary condition is implemented based
on the "combined" law of the wall. It enables us to model the effects of roughness. The
new boundary condition is validated by performing simulations of turbulent flow in rough
pipes and comparing the computed friction factor to the one given by the Moody diagram.
Finally, turbulent flow in periodically corrugated (flexible) pipes is considered. New
flow phenomena (such as flow separation) caused by the corrugation are pointed out and
the essence of periodically fully developed flow is explained. The friction factor for different
values of relative roughness of the fabric is estimated by performing a series of simulations.
Conclusions are drawn based on the results of the computations. Some of them are that
the k - ?? model performs slightly better than the k - ! model in predicting both regular
and separated flow and that the friction factor in a flexible corrugated pipe is mostly
determined by the shape and size of the steel spiral, and not by the type of the fabric
which is wrapped around the spiral.
| Original language | English |
|---|---|
| Title of host publication | Proceedings of the ASME 28th International Conference on Ocean Offshore and Arctic Engineering (Honolulu HI, USA, May 31-June 5, 2009) |
| Publisher | American Society of Mechanical Engineers |
| Pages | OMAE2009-79854- |
| Publication status | Published - 2009 |