Suspension Flows in a Pipeline with Partial Phase Separation

The formulation of a model for the evolution of the flow of a solid-liquid mixture (coal-water) in a horizontal pipeline with partial phase separation is the aim of this work. Problems of instabilities due to complex eigenvalues, observed in previous models, seem to be completely solved in the present model, in which we give the genesis of the different terms written in the equations, coming from the natural definition of mass and momentum balance, and the consequent proof of well-posedness of the obtained PDE system with boundary-Cauchy data. The model describes a three-layer flow. Most of the material is carried by the upper layer, while the bottom layer consists of an immobile sediment. The intermediate layer grows to a maximum thickness and has the role of regulating the mass exchange between the extreme layers. In the last section we present some simulations for a particular choice of flow regime, and boundary-Cauchy data, that were suggested by experimental results provided by Snamprogetti (Fano, Italy).Comment: 29 pages, 7 figure

Viscosity effects on sand flow regimes and transport velocity in horizontal pipelines

Solids transport in multiphase systems is one of the issues under the umbrella of ‘‘flow assurance.’ But unlike issues such as waxes and hydrates, solids transport has received relatively little interest to date. The overall aim of this research was to investigate the fluid viscosity effects on sand particle transport characteristics in pipelines. Investigations were conducted using a 3-inch test facility for oil and a 4- inch flow loop for water and CMC experiments. Three oil viscosities were used including 105 cP, 200 cP and 340 cP. The sand used had a density of 2650 kg/m3 and a median diameter of 0.2 mm. The sand loadings were 50 lb/1000 bbl and 200lb/1000bbl. Based on the King et al (2000) sand minimum transport condition definition, the sand transport velocity for water, CMC solutions and oil (105 cP, 200 cP and 340 cP) were determined by visual observation and camera. The observed sand/oil flow regimes were compared. For oil/sand tests, it was observed that the dominant regime when approaching the critical sand transport velocity was the sliding sand bed, sand dunes were notably absent. However, for water and 7 cP CMC solution, sand dunes and sliding sand bed regimes were observed when approaching the sand transport velocity. For 20cP CMC solution, it was observed that the sand particles in the region between the main dunes were very active compared to those within the dunes

Characterization of liquid-liquid flows in horizontal pipes

Diverse flow regimes have been encountered in liquid-liquid flows. Some degree of consistency in the observed flow patterns is shown in reported studies, while inconsistency exits when physical properties of the two phases concerned are wide enough. An attempt was made in this study to investigate the mechanisms behind flow patterns of liquid-liquid flows in horizontal pipes. A literature review on flow patterns of liquid-liquid flows in horizontal pipes was conducted. The ratio of the gravitational force to viscous force was proposed to characterize liquid-liquid flows in horizontal pipes into gravitational force dominant, viscous force dominant and gravitational force and viscous force comparable flow featured with different basic flow regimes. Comparisons of the proposed characterization criterion with the literature data show good agreement

Rapid Filling Analysis with an Entrapped Air Pocket in Water Pipelines Using a 3D CFD Model

A filling operation generates continuous changes over the shape of an air–water interface, which can be captured using a 3D CFD model. This research analyses the influence of different hydro-pneumatic tank pressures and air pocket sizes as initial conditions for studying rapid filling operations in a 7.6 m long PVC pipeline with an irregular profile, using the OpenFOAM software. The analysed scenarios were validated using experimental measurements, where the 3D CFD model was suitable for simulating them. In addition, a mesh sensitivity analysis was performed. Air pocket pressure patterns, water velocity oscillations, and the different shapes of the air–water interface were analysed

Mechanistic Leak-Detection Modeling for Single Gas-Phase Pipelines: Lessons Learned from Fit to Field-Scale Experimental Data

The use of pipelines is one of the most popular ways of delivering gas phases as shown by numerous examples in hydrocarbon transportation systems in Arctic regions, oil and gas production facilities in onshore and offshore wells, and municipal gas distribution systems in urban areas. A gas leak from pipelines can cause serious problems not only because of the financial losses associated but also its social and environmental impacts. Therefore, establishing an early leak detection model is vital to safe and secure operations of such pipeline systems.A leak detection model for a single gas phase is presented in this study by using material balance and pressure traverse calculations. The comparison between two steady states, with and without leak, makes it possible to quantify the magnitude of disturbance in two leak detection indicators such as the change in inlet pressure (ΔPin) and the change in outlet flow rate (Δqout) in a broad range of leak locations (xleak) and leak opening sizes (dleak). The results from the fit to large-scale experimental data of Scott and Yi (1998) show that the value of leak coefficient (CD), which is shown to be the single-most important but largely unknown parameter, ranges from 0.55 to 4.11, and should be a function of Reynolds number (NRe) which is related to leak characteristics such as leak location (xleak), leak opening size (dleak), leak rate (qleak) and system pressure. Further investigations show that between the two leak detection indicators, the change in outlet flow rate (Δqout) is superior to the change in inlet pressure (ΔPin) because of larger disturbance, if the pressure drop along the pipeline is relatively small compared to the outlet pressure; otherwise, the change in inlet pressure (ΔPin) is superior to the change in outlet flow rate (Δqout).Key words: Leak; Leak detection modeling; Pipeline; Leak coefficient; Gas flow in pip

Effects of finite strains in fully coupled 3D geomechanical simulations

Numerical modeling of geomechanical phenomena and geo-engineering problems often involves complex issues related to several variables and corresponding coupling effects. Under certain circumstances, both soil and rock may experience a nonlinear material response caused by, for example, plastic, viscous, or damage behavior or even a nonlinear geometric response due to large deformations or displacements of the solid. Furthermore, the presence of one or more fluids (water, oil, gas, etc.) within the skeleton must be taken into account when evaluating the interaction between the different phases of the continuum body. A multiphase three-dimensional (3D) coupled model of finite strains, suitable for dealing with solid-displacement and fluid-diffusion problems, is described for assumed elastoplastic behavior of the solid phase. Particularly, a 3D mixed finite element was implemented to fulfill stability requirements of the adopted formulation, and a permeability tensor dependent on deformation is introduced. A consolidation scenario induced by silo filling was investigated, and the effects of the adoption of finite strains are discusse

A microwave cavity resonator sensor for water-in-oil measurements

Online monitoring of Water-Liquid Ratio (WLR) in multiphase flow is key in petroleum production, processing and transportation. The usual practice in the field is to manually collect offline samples for laboratory analysis, which delays data availability and prevents real time intervention and optimization. A highly accurate and robust sensing method is needed for online measurements in the lower end of WLR range (0%–5%), especially for fiscal metering and custody transfer of crude oil, as well as to ensure adequate flow assurance prevention and remedial solutions. This requires a highly sensitive sensing principle along with a highly precise measurement instrument, packaged together in a sufficiently robust manner for use in the field. In this paper, a new sensing principle is proposed, based on the open-ended microwave cavity resonator and near wall surface perturbation, for non-intrusive measurement of WLR. In the proposed concept, the electromagnetic fringe field of a cylindrical cavity resonator is used to probe the liquid near the pipe wall. Two of the cylindrical cavity resonance modes, TM010 and TM011 are energized for measurements and the shift in the resonance frequency is used to estimate liquid permittivity and the WLR. Electromagnetic simulations in the microwave frequency range of 4 GHz to 7 GHz are used for proof-of-concept and sensitivity studies. A sensor prototype is fabricated and its functionality demonstrated with flowing oil-water mixtures in the WLR range of 0–5%. The frequency range of the proposed sensors is 4.4–4.6 GHz and 6.1–6.6 GHz for modes TM010 and TM011, respectively. The TM011 mode shows much higher sensitivity (41.6 MHz/WLR) than the TM010 mode (3.8 MHz/WLR). The proposed sensor consists of a 20 mm high cylinder, with a diameter of 30 mm and Poly-Ether-Ether-Ketone (PEEK) filler. The non-intrusiveness of the sensor, along with the high sensitivity in the resonance shift, makes it attractive for practical applications

Asynchronous techniques for system-on-chip design

SoC design will require asynchronous techniques as the large parameter variations across the chip will make it impossible to control delays in clock networks and other global signals efficiently. Initially, SoCs will be globally asynchronous and locally synchronous (GALS). But the complexity of the numerous asynchronous/synchronous interfaces required in a GALS will eventually lead to entirely asynchronous solutions. This paper introduces the main design principles, methods, and building blocks for asynchronous VLSI systems, with an emphasis on communication and synchronization. Asynchronous circuits with the only delay assumption of isochronic forks are called quasi-delay-insensitive (QDI). QDI is used in the paper as the basis for asynchronous logic. The paper discusses asynchronous handshake protocols for communication and the notion of validity/neutrality tests, and completion tree. Basic building blocks for sequencing, storage, function evaluation, and buses are described, and two alternative methods for the implementation of an arbitrary computation are explained. Issues of arbitration, and synchronization play an important role in complex distributed systems and especially in GALS. The two main asynchronous/synchronous interfaces needed in GALS-one based on synchronizer, the other on stoppable clock-are described and analyzed

A study on high-viscosity oil-water two-phase flow in horizontal pipes

A study on high-viscosity oil-water flow in horizontal pipes has been conducted applying experimental, mechanism analysis and empirical modelling, and CFD simulation approaches. A horizontal 1 inch flow loop was modified by adding a designed sampling section to achieve water holdup measurement. Experiments on high-viscosity oil-water flow were conducted. Apart from the data obtained in the present experiments, raw data from previous experiments conducted in the same research group was collated. From the experimental investigation, it is found that that the relationship between the water holdup of water-lubricated flow and input water volume fraction is closely related to the oil core concentricity and oil fouling on the pipe wall. The water holdup is higher than the input water volume fraction only when the oil core is about concentric. The pressure gradient of water-lubricated flow can be one to two orders of magnitude higher than that of single water flow. This increased frictional loss is closely related to oil fouling on the pipe wall. Mechanism analysis and empirical modelling of oil-water flow were conducted. The ratio of the gravitational force to viscous force was proposed to characterise liquid-liquid flows in horizontal pipes into gravitational force dominant, viscous force dominant and gravitational force and viscous force comparable flow featured with different basic flow regimes. For viscous force dominant flow, an empirical criterion on the formation of stable water-lubricated flow was proposed. Existing empirical and mechanistic models for the prediction of water holdup and/or pressure gradient were evaluated with the experimental data; the applicability of different models is demonstrated. Three-dimensional CFD modelling of oil-water flow was performed using the commercial CFD code Fluent. The phase configurations calculated from the CFD model show a fair agreement with those from experiments and mechanism analysis. The velocity distribution of core annular flow is characterised with nearly constant velocity across the oil core when the oil viscosity is significantly higher than the water viscosity, indicating that the high-viscosity oil core flows inside the water as a solid body. The velocity profile becomes similar to that of single phase flow as the oil viscosity becomes close to the water viscosity