<title>Video imaging measurement of interfacial wave velocity in air-water flow through a horizontal elbow</title>

Abstract

Two-phase flow in pipelines containing elbows represents a common situation in the oil and gas industries. This study deals with the stratified flow regime between the gas and liquid phase through an elbow. It is of interest to study the change in wave characteristics by measuring the wave velocity and wavelength at the inlet and outlet of the elbow. The experiments were performed under concurrent air-water stratified flow in a horizontal transparent polycarbonate pipe of 0.05m diameter and superficial air and water velocities up to 8.97 and 0.0778 m/s respectively. A non-intrusive video imaging technique was applied to capture the waves. For image analysis, a frame by frame direct overlapping method was used to detect for pulsating flow and a pixel shifting method based on the detection of minimum values in the overlap function was used to determine wave velocity and wavelength. Under superficial gas velocity of less than 4.44 m/s, the results suggest a regular pulsating outflow produced by the elbow. At higher gas velocities, more random pulsation was found and the emergence of localized interfacial waves was detected. Wave velocities measured by this technique were found to produce satisfactory agreement with direct measurements.

Developing a 3D CFD Code to Simulate Incompressible Simultaneous Two-Phase Flow through a Horizontal Bend Using VOF Principle

“…The liquid film variations shown in these results reveals the fact that it's build up upstream of the bend part is the main reason for slug formation. The results of these simulations are consistent with the findings presented in [1], [3], [4].…”

“…In order to qualify the outcomes of the code, simulation results have been compared with the results acquired from three different techniques developed for the same project. These techniques were: 1) High-accuracy pressure sensors used to probe pressure variation along the bend [1]; 2) Fiber optic sensing system (with Laser) used to determine the liquid film thickness and interfacial wave velocity [3]; and 3) High-speed video imaging system developed to determine the interfacial wave velocity [4]. The comparison showed a reasonable agreement.…”

“…Using explicit approximations to the momentum equations (3),(4) and(5) from time n values to find provisional values of the new time velocities; 2) Fixing the Donor-Acceptor Differencing (DAF); 3) Introducing a new control parameter (defoamer -IDIV)to further correct the value of F by a term proportional to the divergence of the actual velocity field, which is not rigorously zero; 4) Improving the algorithm for picking the fluid orientation flags; 5) Refining wall-adhesion via introducing an input parameter (NOWALL) to reduce possible substantial errors in wall adhesion forces caused by curved containing walls; 6) Developing and implementing a new subroutine (TILDE) to aid further tuning pressure and velocity variables through calculating provisional velocities; 7) Improving surface tension calculations through introducing the computational of surface tension pressure and imposing this pressure forces on all interfaces; and 8) Presenting qualitative description of the velocity field distribution for different flow conditions and locations; Furthermore, suitable boundary conditions have been imposed at all mesh, free surface and obstacle boundaries during each stage. Several debugs have been performed on the new code to ensure accomplishing reasonable simulation process.…”

A Critical Review of Advanced Experimental Techniques to Measure Two-Phase Gas/Liquid Flow

“…They observed several flow patterns such as bubbly, dispersed, elongated bubble, slug, stratified, wavy, wavy annular and annular flow patterns. Further studies on advanced photonics measurements can be found in literature [47,[91][92][93][94][95][96][97][98][99][100][101][102][103][104][105] In literature, different flow pattern maps were proposed to predict the two-phase gas/liquid flow regimes. Although in literature these flow maps were investigated for larger length scale experimental set-up, the applicability of these maps to smaller length scale set-up was not conducted extensively.…”

A Critical Review of Advanced Experimental Techniques to Measure Two- Phase Gas/Liquid Flow

“…They observed several flow patterns such as bubbly, dispersed, elongated bubble, slug, stratified, wavy, wavy annular and annular flow patterns. Further studies on advanced photonics measurements can be found in literature [47,[91][92][93][94][95][96][97][98][99][100][101][102][103][104][105] In literature, different flow pattern maps were proposed to predict the two-phase gas/liquid flow regimes. Although in literature these flow maps were investigated for larger length scale experimental set-up, the applicability of these maps to smaller length scale set-up was not conducted extensively.…”