The objective of this study is to experimentally investigate the effect of the top elbow on two-phase flow behavior in a hill configuration of hilly-terrain pipelines. The data used in this study was acquired from the University of Tulsa 420-m long, 50.8-mm. inner diameter flow loop with a hilly-terrain unit consisting of 21-m uphill and 21-m downhill sections. To investigate the effect of the top elbow on the flow behavior, three measurement locations along the test section were selected to analyze the flow behavior, they are 2.5-m upstream of the top elbow, 2.5-m downstream of the top elbow, and at the top elbow.
Preliminary results showed that the top elbow effect on two phase flow behavior depends on the flow behavior upstream of the top elbow, namely the characteristics of the slugs and film. For example, when stable slug flow exists upstream of the top elbow, short slugs completely dissipate forming a smooth film, moderate slugs completely dissipate to form a wavy film at the top elbow and long slugs partially dissipate downstream of the top elbow. In the case of pseudo-slugs entering the top elbow, small roll waves with a smooth film were observed at the location of the top elbow and downstream of it. When slug flow with smooth film flow enters the top elbow, complete dissipation occurs leading to a smooth film or partial dissipation leads to a wavy liquid layer. Uniquely, a slug flow with a large entrapped gas bubble in each slug is observed in which the slugs are partially dissipated into shorter slugs as they reach the top elbow.
