Hassan Pouraria

Burst strength behaviour of an aging subsea gas pipeline elbow in different external and internal corrosion-damaged positions

Abstract Evaluation of the performance of aging structures is essential in the oil and gas industry, where the inaccurate prediction of structural performance can have significantly hazardous consequences. The effects of structure failure due to the significant reduction in wall thickness, which determines the burst strength, make it very complicated for pipeline operators to maintain pipeline serviceability. In other words, the serviceability of gas pipelines and elbows needs to be predicted and assessed to ensure that the burst or collapse strength capacities of the structures remain less than the maximum allowable operation pressure. In this study, several positions of the corrosion in a subsea elbow made of API X42 steel were evaluated using both design formulas and numerical analysis. The most hazardous corrosion position of the aging elbow was then determined to assess its serviceability. The results of this study are applicable to the operational and elbow serviceability needs of subsea pipelines and can help predict more accurate replacement or repair times.

Comparison of different two equation turbulence models for studying the effect of cold outlet diameter on cooling performance of vortex tube

This paper presents a comparison between different two equation turbulence models, in order to find appropriate turbulence model for studying the effect of cold outlet diameter on cooling performance of vortex tube. The standard k-ε, RNG k-ε, Realizable k-ε and standard k-ω model, have been used in this study. Comparison between numerical and experimental results indicates that standard k-ε model predicts energy separation phenomenon better than others. Distribution of static temperature, total temperature, static pressure, components of velocity and angular velocity have been obtained in order to understand the flow behavior inside the tube. Moreover, standard k-ε model has been used for studying the effect of cold outlet diameter on cooling performance of vortex tube.

Numerical study of erosion in critical components of subsea pipeline: tees vs bends

Elbows are a vulnerable part of piping systems in erosive environments. Traditionally, plugged tees are used instead of elbows when the erosion rate is high. However, the advantage of plugged tees over elbows in large-scale pipelines is unclear. A comprehensive computational fluid dynamics study was carried out to predict the erosion rate in plugged tees and elbows. A numerical method was first used for aluminium elbows and tees with available experimental data through which the accuracy of the numerical solution was verified. After validating the model, numerical modelling was used to compare the erosion rates of plugged tees and elbows in varying geometrical conditions, ranging from 0.0254 to 0.6 m diameter carbon steel pipes transmitting multiphase gas/sand flow. The effects of internal flow velocity and sand particle size on erosion rates were also investigated. The numerical results revealed that the erosion ratio between plugged tees and elbows strongly depends on the internal diameter of the pipe, the flow velocity and particle size. Hence, the influence of these parameters should be considered for proper selection of the fittings to be used. Finally, numerical modelling of erosion in two subsea jumpers outfitted with standard elbows and plugged tees was presented.

Modeling of Two-Phase Oil/Water Flow in Horizontal Pipeline Using CFD Technique

In spite of the importance of the flows of two immiscible liquids in diverse range of process, the existing literature does not cover this topic satisfactorily. In the present study, numerical modeling of dispersed oil-water flow through horizontal pipeline has been carried out using Eulerian-Eulerian approach. Three different turbulence models namely the standard k-e, RNG k-e and Reynolds Stress Model (RSM) have been used in this study to identify the best model. Numerical solution was performed using FLUENT 6.3.26 and the results regarding the distribution of volume fraction were compared with published experimental and numerical data. According to the present numerical results, the Reynolds Stress Model can predict the distribution of phases better than the used two-equation turbulence models in this study. Furthermore, it was observed that the present model could predict the trend of pressure drop at different water cuts better than the commonly used homogeneous model. However, the accuracy of the results is not much better than the homogeneous model.Copyright