Wide Range Of Fluid Properties Research Articles

CFD modeling of emulsions inside static mixers

Emulsification carried out in continuous devices offers a series of advantages over batch emulsion, such as better control of the droplet size distribution, reduced volume equipment, and lower operative costs. This paper investigates through Computational Fluid Dynamics simulations the emulsification process inside Sulzer Static Mixers. An analysis aimed to identify the most appropriate turbulence model, from a practical point of view, was performed, finding that the realizable k−ϵ model is more suitable than the well-known k−ω model. Moreover, an operative correlation linking the Sauter diameter to the main operating parameters, in a wide range of fluid properties and operating conditions, was developed.

Flow Characterisation Using Fibre Bragg Gratings and Their Potential Use in Nuclear Thermal Hydraulics Experiments

With the ever-increasing role that nuclear power is playing to meet the aim of net zero carbon emissions, there is an intensified demand for understanding the thermal hydraulic phenomena at the heart of current and future reactor concepts. In response to this demand, the development of high-resolution flow analysis instrumentation is of increased importance. One such under-utilised and under-researched instrumentation technology, in the context of fluid flow analysis, is fibre Bragg grating (FBG)-based sensors. This technology allows for the construction of simple, minimally invasive instruments that are resistant to high temperatures, high pressures and corrosion, while being adaptable to measure a wide range of fluid properties, including temperature, pressure, refractive index, chemical concentration, flow rate and void fraction—even in opaque media. Furthermore, concertinaing FBG arrays have been developed capable of reconstructing 3D images of large phase structures, such as bubbles in slug flow, that interact with the array. Currently a significantly under-explored application, FBG-based instrumentation thus shows great potential for utilisation in experimental thermal hydraulics; expanding the available flow characterisation and imaging technologies. Therefore, this paper will present an overview of current FBG-based flow characterisation technologies, alongside a systematic review of how these techniques have been utilised in nuclear thermal hydraulics experiments. Finally, a discussion will be presented regarding how these techniques can be further developed and used in nuclear research.

Data driven prediction of oil reservoir fluid properties

Accuracy of the fluid property data plays an absolutely pivotal role in the reservoir computational processes. Reliable data can be obtained through various experimental methods, but these methods are very expensive and time consuming. Alternative methods are numerical models. These methods used measured experimental data to develop a representative model for predicting desired parameters. In this study, to predict saturation pressure, oil formation volume factor, and solution gas oil ratio, several Artificial Intelligent (AI) models were developed. 582 reported data sets were used as data bank that covers a wide range of fluid properties. Accuracy and reliability of the model was examined by some statistical parameters such as correlation coefficient (R2), average absolute relative deviation (AARD), and root mean square error (RMSE). The results illustrated good accordance between predicted data and target values. The model was also compared with previous works and developed empirical correlations which indicated that it is more reliable than all compared models and correlations. At the end, relevancy factor was calculated for each input parameters to illustrate the impact of different parameters on the predicted values. Relevancy factor showed that in these models, solution gas oil ratio has greatest impact on both saturation pressure and oil formation volume factor. In the other hand, saturation pressure has greatest effect on solution gas oil ratio.

Validation of droplet-generation performance of a newly developed microfluidic device with a three-dimensional structure

We fabricated a microfluidic device with a three-dimensional (3D) structure and verified its droplet-generation performance for the stable production of droplets of around 10 μm in size. We compared the performance of the 3D device with that of conventional simple T-junction and cross-junction structures. The continuous phase sheared the dispersed phase into droplets from eight directions in the 3D device, compared with only one direction in the T-junction device and two in the cross-junction device. Droplets were produced efficiently over a wide range of fluid properties and flow conditions with the 3D device, unlike with the two conventional planar devices. Fluidic experiments were conducted using mineral oil with a surfactant as the continuous phase, deionized (DI) water as the dispersed phase, and DI water with glycerin to change the viscosity of the dispersed phase. The minimum droplet length was 47.2 μm in the T-junction device, 39.0 μm in the cross-junction device, and 22.4 μm in the 3D device when using a water and glycerin mixture with a viscosity of 9.0 mPa·s. Compared with the conventional devices, smaller droplets were produced using our 3D device, indicating that it has excellent droplet-generation performance.

Understanding the effect of counterpressure buildup during syringe injections

The pain felt during injection, typically delivered via a hypodermic needle as a single bolus, is associated with the pressure build-up around the site of injection. It is hypothesized that this counterpressure is a function of the target tissue as well as fluid properties. Given that novel vaccines target different tissues (muscle, adipose, and skin) and can exhibit a wide range of fluid properties, we conducted a study of the effect of volumetric flow rate, needle size, viscosity and rheology of fluid, and hyaluronidase as an adjuvant on counterpressure build-up in porcine skin and muscle tissues. In particular, we found a significant increase in counterpressure for intradermal (ID) injections compared to intramuscular (IM) injections, by an order of magnitude in some cases. We also showed that the addition of adjuvant affected the tissue back pressure only in case of subcutaneous (SC) injections. We observed that the volumetric flow rate plays an important role along with the needle size. This study aims to improve the current understanding and limitations of liquid injectability via hypodermic needles, however, the results also have implications for other technologies, such as intradermal jet injection where a liquid bleb is formed under the skin.

Computational Fluid Dynamics (CFD) Simulations of Taylor Bubbles in Vertical and Inclined Pipes with Upward and Downward Liquid Flow

Summary Two-phase flow is a common occurrence in pipes of oil and gas developments. Current predictive tools are based on the mechanistic two-fluid model, which requires the use of closure relations to predict integral flow parameters such as liquid holdup (or void fraction) and pressure gradient. However, these closure relations carry the highest uncertainties in the model. In particular, significant discrepancies have been found between experimental data and closure relations for the Taylor bubble velocity in slug flow, which has been determined to strongly affect the mechanistic model predictions (Lizarraga-García 2016). In this work, we study the behavior of Taylor bubbles in vertical and inclined pipes with upward and downward flow using a validated 3D computational fluid dynamics (CFD) approach with level set method implemented in a commercial code. A total of 56 cases are simulated, covering a wide range of fluid properties, pipe diameters, and inclination angles: Eo ∈ [10, 700]; Mo ∈ [1×10–6, 5×103]; ReSL ∈ [–40, 10]; θ ∈ [5°, 90°]. For bubbles in vertical upward flows, the simulated distribution parameter, C0, is successfully compared with an existing model. However, the C0 values of downward and inclined slug flows where the bubble becomes asymmetric are shown to be significantly different from their respective vertical upward flow values, and no current model exists for the fluids simulated here. The main contributions of this work are (1) the relatively large 3D numerical database generated for this type of flow, (2) the study of the asymmetric nature of inclined and some vertical downward slug flows, and (3) the analysis of its impact on the distribution parameter, C0.

Separation dynamics of immiscible liquids

In this paper, the geometric design of a gravity-based separator is studied with a computational fluid dynamics method. ANSYS Fluent (18.2) is used to model the ratio of horizontal and vertical lengths with three dimensionless groups. A dimensional analysis method is used to develop a new correlation of separator geometric design. Corresponding plots were created and analyzed using nonlinear regression on the x–y Cartesian coordinate system. Also, manual iterations were performed to determine the coefficients in the general correlation relationship. The dimensional analysis results show that the Reynolds and Euler numbers have a direct correlation with separator design, which means increasing the Reynolds and Euler numbers require a separator with a larger length to height ratio to achieve the same separation efficiency. However, the Weber number has an inverse correlation with separator design, which means an increase in the Weber number requires a separator with a smaller length to height ratio. The new correlation developed in this paper can be used as a reference for separator geometry design to separate immiscible fluids with a wide range of fluid properties.

An improved drift-flux correlation for gas-liquid two-phase flow in horizontal and vertical upward inclined wells

Drift-flux model has been diffusely applied to characterize two-phase flow in pipes and wellbores owing to its accuracy and simplicity. The constitutive correlations used in the drift-flux model specifying the relative motion between the phases have been extensively investigated leading to the development of multitudinous correlations. However, previous studies reveal that most of the correlations can either be proper for limited two-phase flow conditions or the applicability is extended by increasing the complexity of the correlation. This study attempts to propose an improved drift-flux correlation concerning the distribution coefficient and drift velocity applying for a wide range of fluid properties, pipe orientations, and flow patterns without complicating the correlation. In this study, the drift velocity is defined in terms of pipe diameter, inclination angle, and void fraction while the distribution coefficient is correlated as a function of mixture Reynolds number and a Yield-Power-Law correlation in terms of void fraction. A comprehensive experimental database consisted of 1865 data records collected from 13 distinct sources is used for correlation parameterization and performance estimation. The proposed correlation shows comparable or even better performance in comparison to the other three well-established drift-flux correlations for predicting void fraction. The proposed correlation has also demonstrated outstanding performance in case where high liquid viscosity is involved.

Treatment of Rate-Transient Analysis During Boundary-Dominated Flow

Summary Significant advances have been made in the development of analytical models for performing rate-transient analysis (RTA) for single-phase oil and gas reservoirs. The primary complication associated with the adaptation of these solutions to wells exhibiting multiphase flow is the single-phase assumption in the development of the material-balance time function. Despite some efforts in modifying existing dry-gas formulations for use with gas/condensate reservoirs, that approach is not practical for analyzing multiphase flow from oil wells with multiphase-flow characteristics. In this work, we present a simple yet semianalytical model that provides a solution for analyzing production data from wells exhibiting multiphase flow during boundary-dominated flow periods. The solution is obtained by combining the material-balance equation and the productivity index (PI) for all flowing phases. Appropriately defined total pseudopressure and total pseudotime are introduced to handle the associated multiphase nonlinearities in the governing flow equations of oil, gas, and water phases simultaneously. A generalized flowing-material-balance (FMB) equation is derived from the total pseudovariables to estimate original fluid in place and drainage area (given volumetric input). The presented model provides a theoretical framework for analyzing production data considering a wide variety of reservoir-fluid systems. The new method is validated against numerical simulation, covering a wide range of fluid properties and operating conditions. In all simulated cases, the new method matches simulation input acceptably. Two field examples are also analyzed to demonstrate the practical applicability of this approach. This work serves as a practical and simple engineering tool for production-data analysis on wells exhibiting single and multiphase flow during boundary-dominated flow.

Designing a high temperature high pressure mesh sensor

Abstract State-of-the-art turbulence models are expected to accurately predict flow behavior in a wide range of geometries and flow conditions for a wide range of fluid properties. These models rely on accurate time resolved measurements of scalar and vector flow variables. One such measurement technique for obtaining a high density of flow field variables with high time resolution is in the form of electrode-mesh sensors (WMS) which measure the local instantaneous electrical conductance of a flow at a large number of positions, typically in the cross-section of a conduit at frequencies up to 10 kHz. Extensive studies on single and multiphase flows have been carried out with mesh sensor technology in the past 15 years, often focused on flows directly related to nuclear power generation. However, essentially all of these experiments have taken place at low temperatures ( A new mesh sensor construction has been designed at the ETH Zurich for operation in high temperature and pressure pipelines by implementing novel materials, assemblies and a new sealing methodology. The mesh sensor package design is scalable so as to be compatible with standard flanged pipelines of size estimated to be DN10. The new design solves the problems discussed related to prior state of the art while at the same time allowing the sensor to operate at higher temperatures and to be manufactured and assembled more easily and more cheaply. The pressure barrier is no longer guaranteed by an epoxy, as in prior state of the art developed by other researchers, but rather by a standard graphite gasket between the sensor housing flanges, the same type that would normally be sealing a bolted flange joint, and commercially available threaded sealing glands. While still maintaining space for the standard number of bolts for a given flange size, such sealing glands could conceivably allow for a very high number of electrode signals to be extracted. The ability to carry a large number of conductors through the pressure barrier, in addition to the housing flange design, enables the installation of multiple mesh sensors, three layer sensors, or other instrumentation such as thermocouples, enabling the reconstruction of additional flow properties from measured data such as velocity and interfacial area concentration. A 16-transmitter, 16-receiver prototype sensor has been constructed for a DN80 pipeline; its individual components and some assemblies thereof have been tested in an autoclave at temperatures up to 285 °C in a liquid water-vapor environment with boiling at saturation pressure. Furthermore, a test section construction has enabled the sensitivity of the sensor to temperature changes via the variable electrical conductivity of deionized water as a function of temperature to be investigated.

Towards the understanding of bubble-bubble interaction upon formation at submerged orifices: A numerical approach

Present study reports numerical investigations on the bubble evolution at submerged orifices and their mutual interactions in quiescent liquid under constant inflow condition of air. In finite volume based 3D domain, breaking and making of interfaces are tracked using volume of fluid (VOF) solver. Binary interaction dynamics is studied for a wide range of fluid properties (3.85×10−11<Mo<4.645×10−6), orifice diameters (1, 1.5 and 2mm) and spacings (2–10mm). Apart from observed coalescence and non-coalescence, fusion of bubbles before and after pinch off from orifice mouth at different Mo are presented. Using velocity patterns inside the bubble, explanation of different merging pattern is proposed. A 3D map for distinct behaviour while merging, in terms of Mo, orifice diameter and spacing is also tried. Finally, effect of velocity of gaseous phase on merging between sister bubbles are assessed numerically.

A nonlinear flow-transition criterion for the onset of slugging in horizontal channels and pipes

In this work, the interfacial instability and transition of a two-fluid flow from a stratified state to large amplitude waves or slugs is considered. By combining an asymptotic approximation of the linear Orr-Sommerfeld analysis with nonlinear resonant wave interaction theory, a novel nonlinear slug-transition criterion is derived. This criterion corresponds to a bounding condition on the upper fluid’s velocity in order to limit the amount of energy (provided by the linear instability) which is transferred to long waves through resonant wave interactions. It is proposed that such a condition can predict the formation of large-amplitude long waves and/or slugs. Quantitative comparisons of the onset of slugging are made between the prediction by the nonlinear transition criterion and the experimental measurements carried out in a horizontal square channel. Good agreement is observed. An additional heuristic model is developed which generalizes the transition criterion to flow through horizontal pipes. Comparisons are made for flows through different pipe diameters and over a wide range of fluid properties. Good agreement between the present theoretical predictions and the experimental measurements is also observed.

History Matching and Forecasting Tight Gas Condensate and Oil Wells by Use of an Approximate Semianalytical Model Derived From the Dynamic-Drainage-Area Concept

SummaryRecently, low-permeability (tight) gas condensate and oil reservoirs have been the focus of exploitation by operators in North America. Multifractured horizontal wells (MFHWs) producing from these reservoirs commonly exhibit long periods of transient flow, during which two-phase flow of oil and gas begins because of well flowing pressures dropping to less than saturation pressure. History matching and forecasting of such wells can be rigorously performed by use of numerical simulation, but this approach requires significant data and time to set up. Analytical methods, although requiring fewer data and less time to apply, have historically been developed only for single-phase-flow scenarios. In this work, a novel and rigorous analytical method is developed for history matching and forecasting MFHWs experiencing multiphase flow during the transient and boundary-dominated flow periods.The distance-of-investigation (DOI) concept has been used for many years in pressure-transient analysis to estimate distances of reservoir boundaries to wells, among other applications. In the current work, the DOI concept is used to estimate dynamic drainage area (DDA) to forecast tight gas condensate and oil wells; a linear flow geometry is assumed. During transient flow, the DDA is calculated at each timestep by use of the linear-flow DOI formulation; a multiphase version of the linear-flow productivity-index (PI) equation and material-balance equations for gas, condensate, and oil are solved iteratively for pressure, saturation, and fluid-production rate. The PI equations for gas and oil use pseudopressure, which is evaluated with saturation/pressure relationships derived from pressure/volume/temperature data. For boundary-dominated flow, when the drainage area is static, the inflow equations are again coupled with material balance for both phases.The new method is validated against numerical simulation, covering a wide range of fluid properties and operating conditions. The new method matches the simulation acceptably for all cases studied. Field examples of MFHWs are also analyzed to demonstrate the practical applicability of the approach. The three liquid-rich shale examples analyzed were also chosen to represent a wide range of fluid properties. In all cases, acceptable history matches are achieved.The new analytical forecasting/history-matching procedure developed in this work provides a practical alternative to numerical simulation for tight gas condensate and oil experiencing two-phase flow during the transient-flow period. The method, which does not rely on Laplace-space solutions, is conceptually simple to understand, easy to implement, and avoids the inconvenience of Laplace-space inversion.

Model Investigations on the Stability of the Steel-Slag Interface in Continuous-Casting Process

In the continuous-casting mold, the mold powder in contact with the liquid steel surface forms a liquid slag layer. The flow along the steel-slag interface generates shear stress at the interface, waves, and leads to fingerlike protrusions of liquid slag into steel. Reaching a critical flow velocity and thereby shear stress, the protrusions can disintegrate into slag droplets following the flow in the liquid steel pool. These entrained droplets can form finally nonmetallic inclusions in steel material, cause defects in the final product, and therefore, should be avoided. In the current work, the stability of a liquid-liquid interface without mass transfer between phases was investigated in cold model study using a single-roller driven flow in oil-water systems with various oil properties. Applying the similarity theory, two dimensionless numbers were identified, viz. capillary number Ca and the ratio of kinematic viscosities ν 1/ν 2, which are suitable to describe the force balance for the problem treated. The critical values of the dimensionless capillary number Ca* marking the start of lighter phase entrainment into the heavier fluid, are determined over a wide range of fluid properties. The dimensionless number ν 1/ν 2 was defined as the ratio of kinematic viscosities of the lighter phase ν 1 and heavier phase ν 2. The ratios of kinematic viscosities of different steel-slag systems were calculated using measured thermophysical properties. With the knowledge of thermophysical properties of steel-slag systems, Ca* for slag entrainment as a function of v 1/v 2 is derived. Assuming no reaction between the phases and no interfacial flow, slag entrainment should not occur under the usual casting conditions.

Two-phase Inflow Performance Relationship Prediction Using Two Artificial Intelligence Techniques: Multi-layer Perceptron Versus Genetic Programming

A genetic programming model has been compared with multi-layer perceptron (MLP) and empirical correlations to predict the inflow performance of vertical oil wells experiencing two-phase flow. The genetic programming under discussion in this work relies on tree-like building blocks, and thus supports process modeling with varying structure. The necessary training data have been obtained from 16 different simulated reservoir models, covering a wide range of fluid properties and relative permeabilities. The results show that the fitted genetic programming model gives the smallest error for unseen data, when compared with MLP and empirical correlations.

Measurements of liquid film flow as a function of fluid properties and channel width: Evidence for surface-tension-induced long-range transverse coherence

We study experimentally the influence of the transverse dimension on film flow in relatively wide channels with sidewalls. Large deviations from two-dimensional predictions are observed in the primary instability and in the post-threshold traveling waves, and the deviations are presently shown to depend strongly on fluid physical properties. Measurements for a wide range of fluid properties are found to correlate with the Kapitza number, which represents the ratio of capillary to viscous stresses. These observations point to an unexpected long-range effect of surface tension that provides transverse coherence to the flow.

Predicting sizes of droplets made by microfluidic flow-induced dripping

We present a model to predict the size of droplets dripping into an immiscible flowing fluid in glass capillary microfluidic devices. Despite the complex flow behavior in the confined geometry of microfluidic devices, we find that the size of dripping droplets can be accurately predicted by a simple analytic expression based on the ratio of shear and interfacial forces acting on the droplet surface, also known as the Capillary number. We show that data obtained for a wide range of fluid properties and flow conditions including single and multiple dripping events and other experimental data previously reported in the literature can be quantitatively described using one single universal value for the critical Capillary number leading to droplet rupture.

Equilibrium shape and contact angle of sessile drops of different volumes—Computation by SPH and its further improvement by DI

Equilibrium shapes of sessile liquid drops over horizontal substrates are modeled using smoothed particle hydrodynamics (SPH). The model can predict the variations of shape and contact angle of drops as a function of drop volume. In the model, a scheme of repositioning the particle at the triple line has been incorporated to attain the in situ contact angle. The simulations show a reasonable match with available analytical results. However, some mismatch of the drop shape near the three-phase contact line is observed. To improve the predictability, combined diffused interface smoothed particle hydrodynamics model ( Das and Das, 2009b) is employed. The developed hybrid simulations improve the prediction. Estimated drop shapes and contact angle agree with experimental data reasonably well over a wide range of fluid properties and drop volume. The technique establishes the suitability of a particle-based hydrodynamic simulation for the modeling of complex interfaces and three-phase contact lines.

The coefficient of restitution for air bubbles colliding against solid walls in viscous liquids

The motion of air bubbles undergoing collisions with solid walls was studied experimentally. Using a high speed camera, the processes of approach, contact, and rebound were recorded for a wide range of fluid properties. The process is characterized considering a modified Stokes number, St∗=(CAMρdeqU0)/(9μ), which compares the inertia associated with the bubble (added mass) and viscous dissipation. We found that the dependence of the coefficient of restitution, ϵ=−Ureb/U0, with the impact Stokes number can be approximated by −log ϵ∼(Ca/St∗)1/2, where Ca is the capillary number; this behavior is very different from that found for the case of solid spheres. Most importantly, it shows that ϵ does not depend on the approach velocity. Considering a model for the process of contact and rebound of a deformable particle, this dependence is validated. Furthermore, by comparing the experimental trajectories and velocities of the bubble approach with model predictions, it was found that the film drainage is dominated by inertial effects; viscous effects, which would dominate for the case of approaching solid particles, are of secondary importance in this case.

Modeling and experimental studies of large amplitude waves on vertically falling films

Experimental data on the amplitude of large waves on vertically falling films are presented over a wide range of fluid properties and flow rates. Attempts are made to correlate the amplitude of these naturally excited and saturated waves to the Weber ( We) and Kapitza numbers ( Ka), the two dimensionless groups characterizing the film. For viscous fluids (with 2 < Ka < 200 ), the wave amplitude increases with the reciprocal of the Weber number and saturates at values around 3 ( h max / h N ∼ 3 ) while the dependence on Ka is found to be weak. For less viscous fluids ( 200 < Ka < 3890 ), the waves are found to be much more dynamic with amplitudes saturating at much higher values of around 10. The film roughness, or more precisely, the standard deviation (r.m.s) of the film thickness is also found to be correlated with the reciprocal of the Weber number. Scaling arguments are used to explain the initial increase in wave amplitudes. A two-equation h– q model is used to study the spatio-temporal dynamics of waves on long domains with periodic inlet forcing. The model is used to examine the amplitude–celerity relation for three families of solitary waves: the slow moving γ 1 family, the fast moving γ 2 family and the very fast moving ‘tsunami ( Γ 2 ) family’ having Nusselt film as the substrate. It is found that the film profile at short distances depends on the forcing amplitude and frequency but once the wave amplitude exceeds a critical value, the amplitude–celerity relationship is linear for all solitary waves that exist on the film and is independent of the forcing frequency or amplitude. It is also found that for a fixed set of fluid properties and flow rate ( We and Ka), the Γ 2 wave has the largest amplitude and wavelength. Local bifurcation and computational results are used to explain the experimentally observed wave amplitudes on naturally excited films.