A numerical study on water wetting associated with the internal corrosion of oil pipelines

Long distance pipelines are considered as the vein of the oil and gas industry on land and offshore. A well often produces water along with crude oil. The presence of water as well as dissolved gases such as CO2 and H2S introduces a serious menace of internal corrosion. It is well known that the distribution of water and oil inside the pipeline has a great influence on the corrosion rate. As a matter of fact, internal corrosion occurs when a free layer of water comes in contact with the pipe. Hence, predicting the distribution of water inside the pipe and identifying the continuous phase that directly wet the wall is of foremost importance when dealing with internal corrosion of oil pipelines. The accurate prediction of the distribution of water significantly increases the accuracy of corrosion prediction as well as the confidence regarding the integrity of the pipelines. In spite of all the great efforts toward studying different influential factors associated with the internal corrosion of steel pipelines, a large gap of knowledge is observed in predicting the water wetting. The objective of the present study is to employ a tuned two-fluid model by taking advantage of computational fluid dynamics, that is capable of predicting the distribution of water and the type of wetting (water wetting/oil wetting) at the bottom of the pipe. Furthermore, the effect of different parameters such as pipe diameter, oil density, oil viscosity and interfacial tension on the transition from water wetting to oil wetting is studied

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

Phosphorus forms of the surface sediment in the Iranian coast of the southern Caspian Sea

Sediments from the southern Caspian Sea, located in Iranian coast were examined on the basis of P-fractionation (five forms of phosphorus) by a sequential extraction scheme. Ninety-six surface sediment samples (for each season with triplicate) were collected from eight sampling transects in 10 and 100 m depths during summer and winter in 2010-2011. The result indicated that the most abundant forms of phosphorus were calcium bound phosphorus. Relative abundance of other forms of phosphorus follow the order: organic-P>Fe-P>Al-P>Absorbed-P. The loosely absorbed phosphorus represented <1% of the sedimentary inorganic phosphorus, while the Fe/Al phosphorus ranged 5–6%.The calcium bound phosphorus showed considerable contribution (88%) to the sedimentary inorganic P-loads

Elasticity of Carrier Fluid: A Key Factor Affecting Mechanical Phenotyping in Deformability Cytometry

Recently, microfluidics deformability cytometry has emerged as a powerful tool for high-throughput mechanical phenotyping of large populations of cells. These methods characterize cells by their mechanical fingerprints by exerting hydrodynamic forces and monitoring the resulting deformation. These devices have shown great promise for label-free cytometry, yet there is a critical need to improve their accuracy and reconcile any discrepancies with other methods, such as atomic force microscopy. In this study, we employ computational fluid dynamics simulations and uncover how the elasticity of frequently used carrier fluids, such as methylcellulose dissolved in phosphate-buffered saline, is significantly influential to the resulting cellular deformation. We conducted CFD simulations conventionally used within the deformability cytometry field, which neglect fluid elasticity. Subsequently, we incorporated a more comprehensive model that simulates the viscoelastic nature of the carrier fluid. A comparison of the predicted stresses between these two approaches underscores the significance of the emerging elastic stresses in addition to the well-recognized viscous stresses along the channel. Furthermore, we utilize a two-phase flow model to predict the deformation of a promyelocyte (i.e., HL-60 cell type) within a hydrodynamic constriction channel. The obtained results highlight a substantial impact of the elasticity of carrier fluid on cellular deformation and raise questions about the accuracy of mechanical property estimates derived by neglecting elastic stresses

The Relationship Between Physical Activity and Balance Control in the Elderly

Objectives: Aging is a process which causes some changes in physical, psychological, and social aspects&nbsp;of human body. These changes result in decrease in the quality of life and independency. Senility is an&nbsp;important part of the human society and the established changes in the elderly influence his or her relatives&nbsp;and the whole society. Regarding the importance of this topic and a few studies in this field, the purpos&nbsp;of the study is to study the physical activity, the balance control, and their relationship in the elderly. Methods & Materials: In this cross-sectional study, 1614 old people living in Amir Kola City, Iran participated.&nbsp;The research conducted between 2012 and 2013. Their physical activity was measured using&nbsp;standard questionnaire of the physical activity of PASE (the physical activity scale for the elderly), their&nbsp;balance control by Berg Balance test. Then, the data were analyzed through the Chi-square and t test&nbsp;using SPSS. P values less than 0.05 were considered significant. Results: A total of 1614 the elderly people were analyzed in this study (883 males and 733 females). The&nbsp;mean (SD) age of men was 69.96(7.68) and for women it was 68.66(7.02). The relationship between the&nbsp;degree of physical activity and balance control in studied people was statistically significant and direct&nbsp;(P=0.000). Conclusion: The results of this study indicate the existence of significant relation between balance control&nbsp;and physical activity in the elderly. The result also suggests that it is possible to improve the balance&nbsp;control in the elderly by planning to increase the physical activity among them and decrease the related&nbsp;problems such as falling

CFD modelling of the influence of particle loading on erosion using dense discrete particle model

The present study aims at modelling erosion using Dense Discrete Particle Model (DDPM). The numerical model is based on Eulerian-Eulerian-Lagrangian approach which has been developed for modelling both dilute and dense particulate flows. In this approach, the continuous phase is modelled on a fixed Eulerian grid and particles are tracked by using Lagrangian model. However, the particulate phase is also represented on the Eulerian grid and the inter-particle interactions are modelled by employing the kinetic theory of granular flows. Numerical simulations are first performed for a low Stokes number flow of slurry jet test and a high Stokes number flow of dry jet test. The numerical results for slurry jet test indicate a reasonable accuracy of the model in predicting the erosion distribution. Furthermore, the obtained numerical results suggest a reduction of erosion ratio at high particle loadings which agree well with the experimental data in this study. However, the predicted erosion reduction for the high Stokes number flow of dry jet test is significantly higher than that in low Stokes number slurry flow. The present results indicate that there exist a critical particle loading beyond which the erosion reduction becomes significant (more than 20%). However, the magnitude of the critical particle loading for the high Stokes number flow is significantly lower than that in low Stokes number flow. Moreover, the influence of particle loading on the erosion ratio and the flow-field in an elbow conveying two-phase gas-sand flow is investigated. The numerical results clearly revealed a reduction of erosion ratio at high particle loading conditions. Furthermore, a comparison of the obtained results by using DDPM and one-way coupled DPM model shows the importance of considering the influence of inter-particle collisions as wells as coupling between the fluid and particles at high particle loading conditions.N