Progress Update: Effect of Pipe Diameter on Drift Velocity for High Viscosity Liquids
February 26, 2010
Experimental study on the high oil viscosity effect on drift velocity for slug flow was studied in 2 in. diameter pipe by Gokcal (2008). Drift velocity measurement in 3 in. pipe diameter was conducted by Sharma (2008). In continuation, experiments were conducted for 6 in. pipe diameter by Benin Chelinsky. A force analysis was done and based on the recommendations; the experimental set up was modified. An aluminum support for the 6 in. pipe was provided to distribute the increased stress. A new pulley system was used to easily maneuver the 6 in. pipe to different inclination angles and to withstand the load. The viscosity of the oil was varied by heating or cooling the oil. The experiment was carried out at viscosities of 0.574 Pa.s, 0.378 Pa.s, 0.265 Pa.s, 0.154 Pa.s. The experiments were conducted for inclination angles of 0, 10, 30, 50, 70, and 90 degrees. Significant effect of viscosity, diameter and inclination angle was found. These data can be used to test correlations developed for drift velocity of High viscosity oil–gas flow.
On a parallel effort, Dr. Abdel Al-Sarkhi is using a Computational Fluid Dynamics to model drift velocity in horizontal pipes. The purpose of the CFD is to verify the experiments, to have a confidence of using a CFD technique, and to run cases in which conducting experiments is difficult (e.g. 12 in. diameter pipe and very high viscosity). Effects of pipe diameter, high oil viscosity and partially the surface tension have been explained. Based on the experimental data and the CFD result, the drift velocity in horizontal pipes has been modeled using Froude, Inverse viscosity and Eotvos Numbers.
The data for the horizontal cases from experiments and CFD were combined together in a paper entitled “Effect of pipe diameter and high oil viscosity on drift velocity for horizontal pipes” and it will be presented in the BHRg 2010 conference.
The future work on drift velocity is to run CFD in inclined pipe, and to capture, in detail, the effect of surface tension. The effect of surface tension and its physics on drift velocity will be tackled by running (which is in process) the CFD code in small pipe diameter for one case (1/2 in. diameter) and by setting the surface tension value to very small number in the larger diameter pipe and then comparing the results without surface tension.