A numerical study over the effect of curvature and adverse pressure gradient on development of flow inside gas transmission pipelines

Abstract

In order to inspect the effects of adverse pressure gradient (APG) and curvature on the corrosion in the main gas transmission pipelines, the mean velocity and turbulence boundary layer on the walls of six different geometries including a straight pipe (A), a convex pipe (B1), a concave pipe (B2), a convex diffuser (C1), a concave diffuser (C2) and a straight diffuser (D) are calculated. The values of pressure gradient and curvature parameters are chosen 0.62 and 0.023, respectively. The results indicate that the corrosion in the concave curvature is greater than that the corrosion in the convex curvature, since the turbulence intensity increases in the concave curvature while it is suppressed in the convex curvature. In addition, when the boundary layer is exposed to APG and concave curvature simultaneously, the corrosion is greater than the situation when there is only APG or concave curvature. Ultimately, it was found that for the six studied geometries, there are two flow regimes (for velocities lower than 36 m/s) that the turbulence quantities are dependent on velocity. However, for velocities more than 36 m/s, the turbulence quantities and other affected quantities in the shear region are independent.