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The objective of this study is to analyze the influence of the physical properties of Newtonian and Non-Newtonian fluids, such as density, effective viscosity and surface tension, as well as operational parameters of the piping, such as diameter, length and angle of inclination, on the drift velocity for two-phase gas-liquid flow. This study compri...
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... It is relevant to mention that recent studies, such as Andreussi et al. (2009) andPico et al. (2018), have demonstrated that the drift velocity exhibits an inverse relationship with the distance travelled by the bubble, and that this relationship becomes more prominent as the viscosity of the liquid phase increases. Hence, the drift velocity cannot be considered a constant parameter during the development of an individual test. ...
... Previous CFD studies have found that the results obtained with the standard settings of the VOF method implemented in STAR-CCM + tend to be significantly less accurate when handling liquid phases with viscosities over a value of 0:3 PaÁs (Pico et al., 2018). Based on the VOF calibration made in the study by Pineda-Pérez et al. (2018), three different VOF parameters related to the HRIC discretization scheme or the phase interaction were tested in order to obtain the best configuration for the simulations. ...
... Considering this, the geometry was discretized using an unstructured, nonconformal grid that included polyhedral-shaped cells in the core regions of the geometry, as well as five prism layers in the zones near the lateral and posterior walls. While previous studies of flow through pipelines have mostly used some variation of orthogonal or tetrahedral grids (Pineda-Pérez et al., 2018); (Martins et al., 2014); (Martins et al., 2016) , some other authors have recommended the use of polyhedral cells given that the number of neighboring cells tends to be higher, resulting in a better approximation of the gradients, lower skewness angles between cells (less sensitive to cell stretching) and lower numerical diffusion (Pico et al., 2018;Spiegel, 2011). Additionally, these studies have found that, in general, a lower number of polyhedral volumes is needed to obtain that same level of accuracy when compared to tetrahedral volumes. ...
In the past 50 years, several correlations have been developed in order to predict the drift velocity of a liquid-air slug-flow system inside horizontal pipelines. However, a great portion of these correlations is based on either very limited experimental data in terms of fluid properties and operating conditions or on often invalid assumptions. Considering this, the present study assesses the accuracy and validity of seven of the most common non-complex drift velocity correlations through the development of a 3D-Computational Fluid Dynamics (CFD) model using the commercial software Star-CCM+. For this assessment, 13 experimental measurements from the literature were used to validate the CFD model, and 11 case-studies were proposed in order to expand the range of analysis to high-viscosity fluids (μ>0.3 Pa·s) often found in industrial settings. The two-phase system was modelled with an Eulerian-Eulerian approach, coupled with the Volume of Fluid (VOF) method. Three VOF parameters were calibrated in order to obtain the best configurations for different viscosity ranges. The results indicated that the CFD model offers an excellent prediction of the drift velocity given than the average absolute relative error obtained was 6%, even considering highly viscous fluids (μ ∼6.86 Pa·s). The model allowed to confirm that the slug units and gas bubbles do not behave symmetrically in the axial direction and therefore, a 3-D approach substantially improves the accuracy of the model when compared with some 2-D models developed previously. The correlations that showed the highest predicting capabilities were Jeyachandra’s 2012 correlation and Livinus’ 2018 correlation. These two studies considered the combined effect of the Viscosity and Eötvös Numbers, indicating that both parameters significantly influence the drift velocity. In addition, a new correlation was developed by the fitting of the CFD results for all the case-studies proposed. This new correlation slightly improves the prediction achieved by other authors as the overall average error obtained (18%) is 4% lower than the one found for the correlations of Livinus (2018) and Jeyachandra (2012) and around 11% and 6% lower for the high-viscosity range (Nvis > 0.1) when compared to those two correlations, respectively.
... Due to the compact structure and the high coefficient of heat transfer in the coils, spiral tube of heat exchangers is used in a variety of industries such as cryogenic industries, natural gas liquefaction, food and pharmaceutical industries, refrigeration, and air conditioning. [1][2][3][4][5] Different non-Newtonian fluids such as polyox and clay suspensions have been used in numerous industries. Regarding the complexity of flow behavior of non-Newtonian fluids in spiral tubes or coiled pipes, it is necessary to rearrange the derived formulas according to the characteristics of these fluids. ...
Non‐Newtonian fluids are considered to those types of fluids that do not follow Newton's law of viscosity where viscosity would change in either more solid or liquid. The objective of this study, a parametric simulation, was performed to investigate the considerable influence of non‐Newtonian fluids on different parameters on spiral tubes. Firstly, governing equations have derived by computational fluid dynamics methods to compare the laminar and turbulent flows. Then, the turbulent flow, the non‐Newtonian flow, power law flow, and cross models are simulated according to the boundary conditions. Consequently, for the Reynolds range of 600‐2500, increasing the Reynolds number decreases the friction coefficient. It is observed that in slow flow, there is no significant difference between the results of cross and power law models. The distribution of velocity profile has slight variation at the pipe outlet for Reynolds 9000 and 20 000. In other words, the flow is constant in developed region inside the spiral pipe. Moreover, the investigation of pressure drop inside the pipe revealed that regarding the increase in Reynolds number, the friction coefficient decreases. In spiral tubes, due to the presence of secondary currents, the friction coefficient is higher than the direct tube.
This article presents the development of a fifth-order multi-resolution finite volume weighted essentially non-oscillatory (WENO) scheme combined with the advection upstream splitting method based on flux vector splitting (AUSMV) numerical flux for analyzing two-phase flow in both horizontal and vertical pipelines. The drift flux flow model comprises of two separate mass conservation equations for each phase for liquid and gas and one momentum equation for mixture and submodels for thermodynamics and hydrodynamics. The two mass conservation equations describe the behavior of each phase in the flow. The mixture-momentum equation takes into account the frictional and gravitational forces acting on the mixture of both phases. The thermodynamic and hydrodynamic submodels provide additional information to fully describe the flow and close the drift flux model. In the presence of these source terms and submodels, it is a challenging task to develop a high order efficient and accurate numerical schemes. The proposed numerical technique captures the peaks of pressure wave, suppresses the erroneous oscillations at the transition zones and resolves the discontinuities more efficiently and accurately. The accuracy of proposed numerical technique is verified by solving the various test problems. Furthermore, the solution obtained by developed numerical technique are compared to those attained with the high-resolution improved CUP and simple finite volume WENO numerical schemes.
Accurate knowledge of flow behaviors of gas/water two-phase flow in pipeline is crucial to production optimization, production string selection, production logging interpretation, down-hole metering, and artificial lift design and modeling. In this study, two-dimensional simulation model of a large-diameter vertical pipe was established by using the software of FLUENT 19.0, which with 125 mm I.D., and 10 m long. Based on the verification of grid independence and comparison of quantitative results of simulations with experimental tests, the effects of input water content and flow rates on flow patterns, phase distribution, holdup, and average velocity distribution along the pipeline were examined using a VoF approach. The results show a quantitative agreement between calculations and experimental data for the liquid holdup. Additionally, the flow pattern will change from bubble flow to cap flow and slug flow with the increase of input gas content when the flow rates of mixtures are unchanged, and it also will gradually transit from dispersed bubble flow to cap flow and slug flow with the increase of input flow rate when setting same input water contents. Furthermore, when the total flow rate less than 50 m3/d, the flow pattern of mixtures is stably bubble flow. In all simulation studies, the phase distribution of mixtures shows the same characteristics, i.e. the water holdup of the three section in the order of highest to lowest as follows: the top section of pipe, the bottom of pipe, and the whole section of pipe. While, the average velocity distribution of the mixture is affected by the input water content, and presents diversification in different ranges of water contents. When the input water contents in the range of 30% to 60%, the average velocity of the three section in the order of highest to lowest as follows: the top section of pipe, the whole of pipe, and the bottom section of pipe. While when the input water contents small than 30% or larger than 60%, the average velocity of the three section in the order of highest to lowest as follows: the bottom section of pipe, the whole of pipe, and the top section of pipe. The systematic analysis of flow characteristics for gas/liquid two-phase flow with low flow rate in a large-diameter pipe can lay a theoretical foundation for the study of logging data interpretative method of gas wells.KeywordsGas/water two-phase FlowLarge diameter pipeFlow behaviorsNumerical simulation
In this article, adaptive THINC-BVD (Tangent of Hyperbola for Interface Capturing)-(Boundary Variations Diminishing) numerical scheme with AUSMV (Advection Upstream Splitting Method based on flux vector splitting) numerical flux is developed for solving the two-phase drift flux model. The drift flux model is considered for analyzing the transient two-phase flow phenomenon in the pipe-lines. This model comprises the two mass conservation equations, one for each phase, and a momentum equation for the mixture of both phases. The mixture momentum equation contains the non-conservative terms. Further, for computation purpose, thermodynamic and hydrodynamic sub-models are considered to close the drift flux model. These non-conservative terms and sub-models offer difficulties in designing the efficient numerical schemes. In the considered adaptive numerical scheme, THINC functions are used for the spatial reconstruction and BVD algorithm is used to minimize the large variations of reconstructed variables at the cell-interfaces. Thus, the developed numerical scheme has great potential to resolve the sharp discontinuities in an efficient and simple way. Various benchmark test problems are considered to verify the robustness of developed adaptive numerical scheme.
In this article, the space-time conservation element and solution element scheme is extended to simulate the unsteady compressible two-phase flow in pipes. The model is non-conservative and the governing equations consist of three equations, namely, two mass conservation equations for each phase and one mixture-momentum equation. In the third equation, the non-conservative source term appears, which describes the sum of gravitational and frictional forces. The presence of source term and two mass conservation equations in considered model offers difficulties in developing the accurate and robust numerical techniques. The suggested space-time conservation element and solution element numerical scheme resolves the volume-contact discontinuities efficiently. Furthermore, the modified central upwind scheme is also extended to solve the same two-phase flow model. The number of test problems is considered, and the results obtained by space-time conservation element and solution element scheme are compared with the solutions of modified central upwind scheme. The numerical results show better performance of the space-time conservation element and solution element method as compare to the modified central upwind scheme.
