Multi phase Flows

This paper provides analysis of output capacitor effects to phase stability of a hysteretic mode controlled buck converter. The hysteretic control method is a simple and fast control technique for switched-mode converters, but the hysteresis control is not oscillator referenced. It results in difficulty to achieve stable switching phase and frequency. In recent papers, the authors propose a use of phase locked loops (PLL) to permit interleaved multiphase operation where each voltage regulator (VR) module is coupled together via output node and leads to a strong loop interaction. In this work analysis of this interaction is studied by Matlab Simulink simulations and a new solution how to partially suppress this effect is given. The proposed method confirms the theoretical analysis.

In this work an implementation of the Particle Finite Element Method Two (PFEM-2) based on the distributed-memory architecture is presented. PFEM-2 consists on a material derivative based formulation of the transport equations with an hybrid spatial discretization which uses an eulerian mesh and lagrangian particles. Strategies for the parallelization of eulerian methods based on mesh or lagrangian solutions based on particles which solve fluid-dynamics problems are widely studied separately, however not enough works treat the use of both approaches together. Typical solutions for domaindistribution on eulerian frames are not proper to balance the work-load on some lagrangian stages, then to achieve good performance must be analyzed the use of weighted decomposition to the partitioning. Performance analysis of the implementation running over a beowulf cluster are presented. The weighted partitioning can be used to improve the speed-up when the diffusion of the problem is low, on the other hand, with large diffusion a classical eulerian decomposition is the best choice. However the overall cpu-time required to solve the presented incompressible flow cases with the PFEM-2 method is lower than using classical eulerian solvers, which give auspicious future thinking in solving massively parallel simulations.

This study proposes a novel discrete-time integral sliding mode control (ISMC) framework for managing pressure in multi-phase flow systems (MPFS), a critical component of hydrocarbon production and transportation. The primary goal is to achieve precise pressure regulation and minimize fluctuations under diverse operational conditions. Unlike traditional approaches, this work employs a Hammerstein nonlinear modeling technique to accurately represent the system dynamics and design the control strategy. The contributions of this research include the development of a data-driven system identification methodology using a single-input, single-output (SISO) Hammerstein model, enabling precise pressure prediction based on experimental data collected from the lab. A robust ISMC algorithm is introduced to address the inherent nonlinearities, disturbances, and uncertainties in multi-phase flow dynamics. The proposed controller is comprehensively validated through numerical simulations and experimental data, demonstrating its capability to reduce pressure fluctuations, enhance stability, and maintain operational efficiency. This novel integration of Hammerstein modeling with discrete-time ISMC offers a scalable and reliable solution to the challenges of pressure control in MPFS. The results demonstrate significant advantages over conventional controllers, such as traditional sliding mode, in terms of robustness and precision, contributing to the safety, efficiency, and sustainability of oil and gas operations.

Accurate prediction of pressure drops in multi-phase flow systems is essential for optimizing processes in industries such as oil and gas, where operational efficiency and safety depend on reliable modeling. Traditional models often need help with the complexities of multi-phase flow dynamics, resulting in high relative errors, particularly under varying flow regimes. In this study, we simulate a comprehensive multiphase flow experimental data collected from the lab. This study presents innovative methods for accurately modeling pressure drops in multi-phase flow systems. It also studies the complicated dynamics of multi-phase flows, which are flows with more than one phase at the same time. It does this by using two different data-driven models, nonlinear ARX and Hammerstein-Wiener, instead of neural networks (NNs), so that the models don't get too good at fitting environments with lots of changes and little data. Our research applies system identification approaches to the intricacies of this domain, providing new insights into choosing the best appropriate modeling strategy for multi-phase flow systems, taking into account their distinct properties. The experimental results show that the nonlinear Hammerstein-Wiener and ARX models were much better than other methods, with fitting accuracy rates of 81.12% for the Hammerstein-Wiener model and 86.52% for the ARX model. This study helps the creation of more advanced control algorithms by providing a reliable way to guess when the pressure drops and showing how to choose a model that fits the properties of the multi-phase flow. These findings contribute to enhanced pressure management and optimization strategies, setting a foundation for future studies on real-time flow control and broader industrial applications.

Computational Fluid Dynamics (CFD) modelling is increasingly being used for studying various metallurgical processes. In secondary steelmaking, gas stirring is used in ladles to enhance the mixing of the steel. This work aims at numerical study to investigate the effect of different closure models on of the flow analysis in a two-phase gasstirred ladle. The study represents a cylindrical geometry, in which liquid Wood’s metal represents the liquid metal phase and nitrogen gas is injected through nozzle located centrically or eccentrically at the bottom of the vessel. Three-dimensional CFD simulations were carried out using the commercial software package ANSYS FLUENT using Euler-Euler multi-phase model. To study the influence of turbulence models on the accuracy of the CFD analysis, three different models Standard k-, k- and Reynolds Stress Model (RSM) were employed. Furthermore, four different gas flow rates (100, 200, 500 and 800 cm/s) were used for studying the effect of gas fl...

In secondary steelmaking, the optimal size and position of open‐eye is important for effective alloying practice. In the current work, the effect of the top layer thickness and density on the formation of open‐eye in a gas stirred ladle was investigated. A one‐fifth scale water model of 150‐ton ladle was established with single and dual plug configurations for the physical modeling measurements. Air, water and three different oils were used to simulate the argon, liquid steel and slag in the water model, respectively. A transient Computational Fluid Dynamics (CFD) model based on Eulerian Volume of Fluid (VOF) approach was developed for numerical modeling of the fluid flow behavior. The physical modeling results show that the relative open‐eye area decreases from 46.7 to 5.6% when top layer thickness was increased from 0.75 to 7.5 cm using a gas flow rate of 7.5 NL min−1. The effect of the number of plugs on the open‐eye area for the same range of top layer thickness mentioned above ...

In ladle metallurgy, gas stirring and behavior of the slag layer are very important for the quality of the steel. When gas is injected through a nozzle located at the bottom of the ladle into the metal bath, the gas jet exiting the nozzle breaks up into gas bubbles. The rising bubbles break the slag layer and create a slag eye. In this paper, the behavior of the slag eye area for different gas flow rates is been investigated through experimental measurements and CFD simulations. A 1/5-scale water model of 150 ton-ladle was deployed for the experimental measurements and for studying the effect of gas flow rate on the slag eye diameter. The physical modelling results show that the slag eye area changes from 20 to 182 cm 2 when the gas flow rate increases from 1.5 to 15 NL/min. The dimensionless area of the open eye was found to be in agreement with earlier studies. The simulations were carried out in the commercial CFD code ANSYS Fluent with mesh generation in ANSYS Workbench. The numerical model developed is based on the Eulerian Multiphase Volume of Fluid (VOF) approach and employs standard 𝑘 -𝜀 turbulence model for solving the turbulent liquid flow induced by bubble-liquid interaction. The simulation results of slag eye area showed a good agreement when compared to experimental results measured.

In ladle metallurgy of steelmaking, the role of gas injection into the metal bath is been studied to a great extent as it improves the quality of steel. The size of the open‐eye is associated with higher emulsification of top slag, which intensifies metal–slag reactions, and information about the position and size of the open‐eye is important for effective alloying practice. Moreover, the open‐eye has an effect on the energy balance since it increases heat losses. In this work, experimental measurements and numerical simulations are performed to study the effect gas flow rate on the formation of the open‐eye in a steelmaking ladle. A one‐fifth scale water model is constructed for studying gas injection with single and dual plug configurations. For the numerical modeling, the Multiphase Volume of Fluid (VOF) model is used for simulating the system including the behavior of the slag layer. The physical modeling results show that the open‐eye area changes from 9.22 to 198.34 cm2 when t...

In the state-of-the-art PIV, image sensors are growing in size and PIV algorithms are increasing in spatial resolution capabilities. These technological advances allow for the simultaneous measurement of increasingly larger spatial scales ranges in a single PIV snapshot. To take fully advantage of the available spatial scales range, PIV setup constraints establish a coupling between the laser sheet thickness and the time between laser pulses. This condition did not apply with older technologies. The resulting value for the optimum laser sheet thickness is in a range where the superposed flow information in the direction of the imaging sensor introduces special characteristics errors at the small scale limit. This may compromise the measurement of flow quantities like dissipation and turbulent kinetic energy (tke), for which the contribution of the small and medium scales may be relevant. Within this scenario the assessment of the smallest scale resolved in the PIV measurement is nec...

Conventional particle image velocimetry (PIV) processing techniques based on correlation show a limited range of application when they are used to describe a concentrated vorticity field. This work focuses on the evaluation of these range limits. In this frame, the application of an advanced PIV technique, namely Local Field Correction Particle Image Velocimetry (LFCPIV) is also evaluated, showing a significant performance enhancement. The magnitude of the measurement error is obtained for conventional and advanced PIV by means of synthetic images of an analytical vortex flow. This gives information on the behaviour to be expected when operating beyond the classical limits of applicability of conventional PIV algorithms. The study of relevant effects, like group-locking, allows for further understanding the sources of the measurement error. The knowledge of these characteristics helps in taking decisions regarding the experimental setup as well as the kind of PIV method to use for a certain application. Real PIV images obtained by partners within Europiv 2 are also analysed and the results commented.

Particle image velocimetry (PIV) is now applied with confidence in industrial facilities such as large wind tunnels, yielding data not possible before. Despite the difficulties that arise in such environments, the conventional PIV methods can provide high quality data, especially when dealing with spatial and temporal slowly varying values of the flow magnitudes. Obtaining highly spatially resolved velocity fields is still challenging due to the inherent difficulties in these industrial facilities, such as large velocity gradients, background light and reflections. This work has focused on: (i) the behaviour of conventional PIV when the conventional limits of the processing algorithm are approached or surpassed and (ii) which kind of advanced methods can reduce the main sources of error that are characterized in this paper. The focus is on the description of vortex flows. Group locking, a major source of error, is introduced, modelled and metrologically characterized. The part of the study devoted to advanced methods deals with one that has already shown to be of profit in images from industrial facilities, local field correction PIV (LFC-PIV). This is a robust and an accurate method, able to obtain a high yield of measurements in these environments, without the need of external adjustment to each particular situation. To illustrate this point, some examples of processing of real images are given. The conclusions of this work suggest guidelines about the error figures when measuring flows with embedded vortex using conventional and advanced methods in industrial facilities.

Local field correction particle image velocimetry (LFC-PIV) has become an established alternative among high-resolution PIV techniques. Previous works by the authors introduced its implementation by means of simple algorithms. In these works the initial limitation of the method, which was related to the mean distance between particles, was removed. Comparison with other contemporary high-resolution techniques indicates that it offers advantages in robustness and accuracy. The trade-off for this better performance is a heavier computing load. Until now, the computing time that this load requires has not been characterized in detail, since this computing time could be substantially reduced by accepting a reduction in accuracy. This paper focuses on the characterization of the trade-off between time and accuracy, thus offering a new perspective to PIV. In this field, LFC-PIV offers a wide range of possibilities that are described in the paper. Several alternative schemes for LFC-PIV are tested, together with an analysis of the influence of the number of iterations. Performance figures for both accuracy and expended time are given. Metrological evaluation is carried out over synthetic images. A test of coherence between these results and the performance on real images is also presented. The paper shows that even for a limited number of iterations this technique offers advantages.

In the past, the authors have addressed the tasks of assessing read-out and peak-locking errors separately. In this paper an improved approach is tested for assessing both errors simultaneously. The rationale is that, generally these errors are coupled in PIV images and the procedures described in previous works are not suitable to determine both errors together, especially when CCD cameras read-out error is relevant. The sources for each error are different enabling for any combination of relative magnitude between errors. The magnitude of the CCD read-out error seems to be related to camera operating conditions (temperature, humidity and sensor illumination) besides its own design, while peak-locking is related to the size of the tracer particle images, the truncation of particle images by window borders and the subpixel peak fitting or image deformation algorithms. The application of PIV in challenging conditions can generate situations where both errors combine with similar magnitude. For the error assessment in these conditions, the work proposes a methodology of general application to PIV. Once it is described, the application to selected synthetic and real cases is offered. The results indicate the possibility to asses bias errors in the order of 0.1 pixels for both sources (peak-locking and CCD read out) simultaneously. In addition, the determination of zones where these errors are not the dominant ones is presented.

This paper offers the fundamentals of a space-time reconstruction technique from non timeresolved, statistically independent data. An algorithm has been developed to identify and track traveling coherent structures in periodic flows. Flow field phase average is reconstructed with a correlation-based method, similar to POD. This method provides a tool for shedding light on flow dynamics and allows for global dynamics study, instead of being limited to mean statistics or point-based techniques. Flow field phase-average is reconstructed with this novel technique. Noteworthy, the involved computational time is relatively small. Phase-locked average data from time-resolved experiments have been used as a comparison basis. This allows for a direct comparison between real and reconstructed flow fields. Good agreement reveals the method suitability for Particle Image Velocimetry (PIV) measurements. The reconstruction technique is then applied to a set of non time-resolved SPIV measurements in an atmospheric burner, under combustion conditions. Finally, the limitation of the technique applicability to any pseudo periodic flow is further discussed on the basis of the relative modes strength of the Proper Orthogonal Decomposition (POD). The discussion offered allows defining a parameter that indicates the suitability of the technique.

Particle Image Velocimetry with Local Field Correction (LFC-PIV) has been tested in the past to obtain two components of the velocity in a two dimensional domain (2D2C). When compared with conventional correlation based algorithms, this advanced technique has showed improvements in three important aspects: robustness, resolution and ability to cope with large displacements gradients. A further step in the development of PIV algorithms consists in the combination of LFC with the Stereo technique, able to obtain three components of the velocity (2D3C PIV). To successfully apply stereoscopy, the laser sheet width is usually larger than in 2C velocimetry, in order to acquire the out of plane displacement of the particles. This peculiarity can make questionable the need for improved spatial resolution. In particular, if some factors concur the measurement of small scale features of the velocity along the laser sheet can be spoiled by the velocity variations across it, caused by the flow structures. Being the spatial resolution capabilities of LFC its main advantage, this paper focuses in establishing if there are advantages left for LFC-PIV in situations where only large scale features are of interest, thus making it difficult for this technique to show its attractiveness. The remaining benefits still to be analyzed are the robustness and the ability to cope with large displacement gradients. For both aspects, the performances of 2D3C-LFC-PIV are explored. These performances are characterized and compared with conventional and other advanced algorithms, when applied to synthetic PIV images. In addition, the coherence between these results and those coming from experimental PIV images is presented and discussed.

SUMMARYIn this paper, we present a computational algorithm for solving an important practical problem, namely, the thermoplastic polymer melting under fire conditions. We propose here a technique that aims at minimizing the computational cost. This is basically achieved by using the immersed boundary‐like approach, combining the particle finite element method for the polymer with an Eulerian formulation for the ambience. The polymer and ambience domains interact over the interface boundary. The boundary is explicitly defined by the position of the Lagrangian domain (polymer) within the background Eulerian mesh (ambience). This allows to solve the energy equation for both subdomains on the Eulerian mesh with different thermal properties. Radiative transport equation is exclusively considered for the ambience, and the heat exchange at the interface is modeled by calculating the radiant heat flux and imposing it as a natural boundary condition. Copyright © 2012 John Wiley & Sons, Ltd.

This study has been conducted on three types of reservoir rocks for core analysis of samples denoted by R-1, R-2 and R-3 of Ghani oil field from three reservoir include Farrud, Facha and Mabruk formations respectively. This analysis includes determination of physical characteristics e. g. porosity (∅), permeability (k), formation factor (FF) and resistivity index (RI). The purpose of this study is to how core petrophysical data might be most investigating effectively applied to the petrophysical prediction of petrophysical properties from core samples analysis. For Farrud reservoir of R-1 shows that the relation between degree of saturation (S w ) and relative oil permeability(Kro) equal the relative permeability of water(Krw) at which the intersection point between the two curves ; whereas, the flow with the same rate. FF and RI are vary with ∅ and the RI is a function of S w . The gas-oil relative permeability have been expressed graphically. Whereas, the intersection point between the two curves (Kro) equal the (Krg), at which both oil and gas are flow with the same rate. A similar results were obtained from Facha reservoir, R-2. The petrophysical properties of core samples for R-3 of Mabruk Formation have been performed including∅, k, and S w . The comparison between the three reservoirs by correlation between the average values such as ∅, k, grain density and RI; shows that the average of Mabruk reservoir k greater than the other two reservoirs, while the other properties seem to be close together.

In this paper, a new compositional mechanistic wellbore model, including gas lifting parameters, is presented. In the governing equations of this model, new terms for mass transfer between phases and the enthalpy of phase change, which are important in non-isothermal gas lift systems, have been considered. These terms have been ignored in some recent research studies and subsequent results show that by ignoring them, serious errors may arise. In the current research study, using a mechanistic drift-flux approach, the pressure distribution in a wellbore was modeled. To verify the new simulator, the results were compared with those of commercial simulators. They were also verified against the phase behavior analysis of the fluid flowing in the wellbore. In addition, in order to show the novel aspects of the new simulator, the results of the presented simulator were compared with the results of a recently proposed model found in the literature. It was concluded that neglecting phase ch...

The latest version of the Particle-Finite Element Method (PFEM), which incorporates the novel explicit integration strategy named eXplicit Integration of Velocity and Acceleration following Streamlines (X-IVAS), has proven to be fast and accurate to solve homogeneous flows, mainly thanks to the possibility of using large time-steps. In this work the extension of this strategy to solve multiphase flows is presented, where the calculation of the interface evolution is of fundamental importance. In Eulerian formulations, one of the most used strategies to determine the interface position is the advection of an indicator function. This approach is followed, by example, in the Volume of Fluid (VoF) technique, which can add limiters as a method of guaranteeing boundedness and/or sharpness of phasefractions. On the other hand, Lagrangian frames use typically marker particles. In the case of PFEM, the same set of particles transported for flow calculation allows to carry a marker function t...

Wind-and wave-generated spray fluxes to an object (cylinder and vertical plate) located on and above the deck of a medium-sized fishing vessel (MFV) are investigated. Using formulas derived for a fully arisen sea, sea-state was defined by the significant wave height, which is a function of wind speed and fetch. Formulas for the liquid water content (LWC) of windgenerated spray are reviewed. It was found that wind-generated spray does not affect an object located on and above the deck of a MFV. Such spray may affect only small ships with low freeboard and low bows in strong winds. Wave-generated spray is the one and only source of water delivery to an object if rain, drizzle, snow, fog, and the flooding of a ship deck by waves is neglected. The wave-generated spray flux was defined using derived formulas of the vertical distribution of the LWC and time of ship exposure to spray originating from spray cloud induced by ship/wave collision. These formulas were derived using published data on a Russian field experiment in the Sea of Japan. The time-averaged water flux to an object can be computed for any given wind speed, fetch, ship speed, and heading angle. These results are applicable for calculating the ice growth rates on medium fishing vessels.

Wind-and wave-generated spray fluxes to an object (cylinder and vertical plate) located on and above the deck of a medium-sized fishing vessel (MFV) are investigated. Using formulas derived for a fully arisen sea, sea-state was defined by the significant wave height, which is a function of wind speed and fetch. Formulas for the liquid water content (LWC) of windgenerated spray are reviewed. It was found that wind-generated spray does not affect an object located on and above the deck of a MFV. Such spray may affect only small ships with low freeboard and low bows in strong winds. Wave-generated spray is the one and only source of water delivery to an object if rain, drizzle, snow, fog, and the flooding of a ship deck by waves is neglected. The wave-generated spray flux was defined using derived formulas of the vertical distribution of the LWC and time of ship exposure to spray originating from spray cloud induced by ship/wave collision. These formulas were derived using published data on a Russian field experiment in the Sea of Japan. The time-averaged water flux to an object can be computed for any given wind speed, fetch, ship speed, and heading angle. These results are applicable for calculating the ice growth rates on medium fishing vessels.

In spray studies related to selective catalytic reduction (SCR) systems a common approach is to replace the urea–water solution (UWS) with pure water, even though there is very limited detailed information on the spray properties for these two liquids obtained under the same conditions using the same experimental equipment. Neither is it known how the possible differences in spray properties influence computational fluid dynamics (CFD) simulations. In this study, besides the flow characteristics, we compare both global and local spray parameters measured for UWS and pure water in the same conditions. To our knowledge, this is the first study which examines the influence on the injection process of replacing UWS with water over such a wide range. Moreover, the influence of different spray properties on CFD simulations is also examined. The experimental studies showed differences in almost all considered spray parameters. Moreover, different spray behaviour was noticed in terms of pri...

We propose a numerical technique for the 3D simulation of the glass forming (Counter Blow and Final Blow processes) based upon a Lagrangian formulation. Adopting the basic philosophy of the Particle Finite Element method (PFEM) [1,3], we introduce several new features adapting the strategy to suit the problem of interest. A smart mesh update strategy and a modification in the treatment of the mass conservation equation are introduced. A contact algorithm, particularly beneficial for the final blow process simulation is developed. The methodology allows for a precise prediction of the final topology of the glass.

Saudi Arabia has a variety of carbonate reservoirs of different geologic ages. Such reservoirs are characterized by extremely heterogeneous rock properties. These heterogeneities are caused by the wide spectrum of environments in which carbonates are deposited and subsequent alteration of the original rock fabric. In this paper, extensive SCAL work was carried out on preserved core plugs recovered from two distinct carbonate reservoirs. The first reservoir is a Late Jurassic Arab-D offshore carbonate reservoir (Abu Safah field). The second one is Shu’aiba reservoir (Shaybah field) located in the Rub’ Al-Khali in southeastern Saudi Arabia. The purpose of this study is to provide and evaluate waterflood recovery efficiency and residual oil saturations of the two distinct Arabian reservoirs. The variation of oil recovery and residual oil saturation between the two distinct reservoirs is due to variations of rock characteristics especially the relationship of textural and diagenetic fea...

In this study a computational method is presented which simulates the presence of a liquid layer on an airfoil and its effect on splashing of Supercooled Large Droplets (SLD). The thin liquid film is expected to have a significant influence on the impact behaviour of SLD. It will arise when the impacting droplets freeze only partially and leave behind a layer of runback water on top of the ice layer. The liquid film is modelled using the wall shear stress and by assuming a linear velocity profile within the water layer. The shear stress is calculated by coupling an integral boundary-layer method to a potential flow method. The SLD splashing model is extended with a deposition model that accounts for impact on a liquid film and includes the solidification time of the droplets. This solidification time is obtained using multiple approaches which are based on either planar solidification or dendritic solidification. Planar solidification is controlled by diffusion and based on the Stef...

Atmospheric ice accretion results from the exposure of technical equipment or facilities to cold and humid environments. Supercooled droplets in a cloud can impact an airplane's surface and quickly form an ice layer. The presence of air pockets in such a layer is well known and explains the white appearance of some of the accretions. However, estimation of its porosity values and studies on the pore formation mechanics remain limited. In this study, we performed tests in an icing wind tunnel and scans with micro-computed tomography to address these issues. Here, we show that the accretion has closed porosity below 1%, which is mostly produced by the interaction between a spray-like impact on the water surface. The insights we provide here are important to improve ice accretion modelling techniques and establish a different approach to address the interaction between the cloud and the surfaces exposed to atmospheric icing.

In this study a computational method is presented which simulates the presence of a liquid layer on an airfoil and its effect on splashing of Supercooled Large Droplets (SLD). The thin liquid film is expected to have a significant influence on the impact behaviour of SLD. It will arise when the impacting droplets freeze only partially and leave behind a layer of runback water on top of the ice layer. The liquid film is modelled using the wall shear stress and by assuming a linear velocity profile within the water layer. The shear stress is calculated by coupling an integral boundary-layer method to a potential flow method. The SLD splashing model is extended with a deposition model that accounts for impact on a liquid film and includes the solidification time of the droplets. This solidification time is obtained using multiple approaches which are based on either planar solidification or dendritic solidification. Planar solidification is controlled by diffusion and based on the Stef...

This study introduces an analytical model to predict the final average droplet size within a spray cloud that is formed due to wave interactions with marine objects. The process of spray cloud formation from wave impact involves several complicated processes, and each of these phenomena should be taken into account when considering an analytical approach. Following this process-based approach, the model first considers the wave characteristics and relates wave properties to the maximum impact pressure also considering the effect of air entrapment occurrence. Secondly, the maximum impact pressure is correlated empirically to the maximum wave run-up velocity. Finally, wave run-up velocity is linked with water sheet breakup models, which leads to the prediction of the final average diameter of ligaments and droplets. The prediction model is compared with experimental measurements from experiments conducted in a tow tank to form a spray cloud due to wave impact with two lab-scale models. Several measuring techniques such as image processing, bubble image velocimetry (BIV), and digital particle image velocimetry (DPIV) methods were implemented to measure the physical quantity of each phenomenon during the event of wave interaction. The effects of initial wave characteristics, the geometrical parameters of the impact condition and water sheet thickness at the moment of impact, on the final average droplet diameter were investigated. A sensitivity analysis of most of the principal parameters was performed to show the high veracity of the prediction model.

This study introduces an analytical model to predict the final average droplet size within a spray cloud that is formed due to wave interactions with marine objects. The process of spray cloud formation from wave impact involves several complicated processes, and each of these phenomena should be taken into account when considering an analytical approach. Following this process-based approach, the model first considers the wave characteristics and relates wave properties to the maximum impact pressure also considering the effect of air entrapment occurrence. Secondly, the maximum impact pressure is correlated empirically to the maximum wave run-up velocity. Finally, wave run-up velocity is linked with water sheet breakup models, which leads to the prediction of the final average diameter of ligaments and droplets. The prediction model is compared with experimental measurements from experiments conducted in a tow tank to form a spray cloud due to wave impact with two lab-scale models. Several measuring techniques such as image processing, bubble image velocimetry (BIV), and digital particle image velocimetry (DPIV) methods were implemented to measure the physical quantity of each phenomenon during the event of wave interaction. The effects of initial wave characteristics, the geometrical parameters of the impact condition and water sheet thickness at the moment of impact, on the final average droplet diameter were investigated. A sensitivity analysis of most of the principal parameters was performed to show the high veracity of the prediction model.

An oil/water capillary transition zone often contains a sizable portion of a field's initial oil in place, especially for those carbonate reservoirs with low matrix permeability. The field-development plan and ultimate recovery may be influenced heavily by how much oil can be recovered from the transition zone. This in turn depends on a number of geological and petrophysical properties that influence the distribution of initial oil saturation (S oi) against depth, and on the rock and fluid interactions that control the residual oil saturation (S or), capillary pressure, and relative permeability characteristics as a function of initial oil saturation. Because of the general lack of relevant experimental data and the insufficient physical understanding of the characteristics of the transition zone, modeling both the static and dynamic properties of carbonate fields with large transition zones remains an ongoing challenge. In this paper, we first review the transition-zone definition and the current limitations in modeling transition zones. We describe the methodology recently developed, based on extensive experimental measurements and numerical simulation, for modeling both static and dynamic properties in capillary transition zones. We then address how to calculate initial-oil-saturation distribution in the carbonate fields by reconciling log and core data and taking into account the effect of reservoir wettability and its impact on petrophysical interpretations. The effects of relative permeability and imbibition capillary pressure curves on oil recovery in heterogeneous reservoirs with large transition zones are assessed. It is shown that a proper description of relative permeability and capillary pressure curves including hysteresis, based on experimental special-core-analysis (SCAL) data, has a significant impact on the field-performance predictions, especially for heterogeneous reservoirs with transition zones. * Currently with Shell Technology Oman (STO). ** Currently with Petroleum Development Oman (PDO).

Summary An oil/water capillary transition zone often contains a sizable portion of a field's initial oil in place, especially for those carbonate reservoirs with low matrix permeability. The field-development plan and ultimate recovery may be influenced heavily by how much oil can be recovered from the transition zone. This in turn depends on a number of geological and petrophysical properties that influence the distribution of initial oil saturation (Sor) against depth, and on the rock and fluid interactions that control the residual oil saturation (Sor), capillary pressure, and relative permeability characteristics as a function of initial oil saturation. Because of the general lack of relevant experimental data and the insufficient physical understanding of the characteristics of the transition zone, modeling both the static and dynamic properties of carbonate fields with large transition zones remains an ongoing challenge. In this paper, we first review the transition-zone d...

Crystallization in liquids is critical to a range of important processes occurring in physics, chemistry and life sciences. In this article, we review our efforts towards understanding the crystallization mechanisms, where we focus on theoretical modelling and molecular simulations applied to ice and gas hydrate systems. We discuss the order parameters used to characterize molecular ordering processes and how different order parameters offer different perspectives of the underlying mechanisms of crystallization. With extensive simulations of water and gas hydrate systems, we have revealed unexpected defective structures and demonstrated their important roles in crystallization processes. Nucleation of gas hydrates can in most cases be characterized to take place in a two-step mechanism where the nucleation occursviaintermediate metastable precursors, which gradually reorganizes to a stable crystalline phase. We have examined the potential energy landscapes explored by systems during...

The inclined plane air classifier is a device designed for the classification of limestone particles. It presents a simple classification mechanism and low energy requirements. Despite its advantages, the industrial application of the classifier has not been reported. This study was carried out to model the classification mechanism inside the inclined plane classifier and to propose its use in the aggregate industry where the adjustment of the particle size distribution of manufactured sands is required. The velocity and pressure fields inside the equipment were modelled using computational fluid dynamics and the particle trajectories were computed using a Lagrangian discrete phase modelling. The collisions between particles were modelled by using the discrete element method. The Taguchi method was used to study the influence of the operational and design variables on the classification performance and to optimize the equipment. The inclined plane classifier was successfully modelled and optimized for the improvement of the particle size distribution of manufactured sands showing excellent results.

In the state-of-the-art PIV, image sensors are growing in size and PIV algorithms are increasing in spatial resolution capabilities. These technological advances allow for the simultaneous measurement of increasingly larger spatial scales ranges in a single PIV snapshot. To take fully advantage of the available spatial scales range, PIV setup constraints establish a coupling between the laser sheet thickness and the time between laser pulses. This condition did not apply with older technologies. The resulting value for the optimum laser sheet thickness is in a range where the superposed flow information in the direction of the imaging sensor introduces special characteristics errors at the small scale limit. This may compromise the measurement of flow quantities like dissipation and turbulent kinetic energy (tke), for which the contribution of the small and medium scales may be relevant. Within this scenario the assessment of the smallest scale resolved in the PIV measurement is nec...

Informasi tentang permeabilitas air-minyak dari batuan reservoar memainkan peranan yang penting dalam kegiatan pemodelan yang berhubungan dengan pemodelan reservoar dan peramalan produksi. Permeabilitas relatif dalam skema imbibisi-skema yang merupakan tema dari tulisan ini-berpengaruh besar atas berbagai proses dinamis di reservoar. Proses injeksi air dan masuknya air dari akuifer ke reservoar merupakan dua contoh yang membutuhkan data tersebut. Studi ini menggunakan model permeabilitas relatif Corey sebagai model permeabilitas relatif imbibisi yang digunakan. Data laboratorium dari 340 percontoh-batupasir dan batugamping-dengan berbagai permeabilitas dan wetabilitas yang diambil dari berbagai lapangan minyak di Indonesia digunakan. Kegiatan pemodelan yang dilakukan menunjukkan perlunya untuk menambahkan dua faktor empiris yang berhubungan dengan wetabilitas batuan dan hambatan diluar pembasahan ke dalam model. Peran kedua faktor tersebut dalam model senyara nyata meningkatkan kemampuan dari model, dan nilai-nilai yang dianggap paling baik untuk kedua faktor juga dihasilkan sesuai dengan jenis wetabilitas dan kategori permeabilitas batuan. Perbandingan antara hasil pemodelan sebelum dan sesudah modifi kasi menunjukkan perbaikan dalam validitas dari keluaran.

In response to current strict laws aiming to reduce motor vehicle emissions, more and more research projects are being carried out in order to enhance the flow of automotive catalysts. There have been substantial efforts to further refine the SCR technology (selective catalytic reduction) for diesel-powered vehicles. Furthermore, only a little distance from the catalytic input between the exhaust system is available for a mobile SCR system. This therefore leads to an insufficient urea residence period, and evaporation and thermolysis at the catalyst entry cannot therefore be completed. This can lead to substantial secondary ammonia and isocyanic acid emissions. Therefore, fast thermolysis, effective ammonia blend with exhaust gas and reduction of ammonia slip are crucial factors for the deployment of SCR technology on cars. The Computational Fluid Dynamics (CFD) approach is used for optimizing the exhaust gas flow inside the existing catalyst by changing intake cone designs which is intended to be used on Euro VI/Bharat Stage-VI emissions legislation compliant heavy-duty diesel engines in India. This study is divided in to two parts. The first part of the study deals with finding the optimized ammonia injector location, and in the second part, the proposed inlet cone design's flow velocity uniformity index is estimated and compared with that of the existing SCR catalyst model.

The paper proposes a way to control the viscosity of numerical approximation in the contact SPH method. This variant of SPH contains momentum and energy fluxes in the right-hand sides of the equations, which are calculated using the solution of the Riemann problem between each pair of neighboring particles within the smoothing kernel support radius, which is similar to the procedure for calculating fluxes across cell boundaries in Godunov schemes. Such SPH method does not require the use of artificial viscosity, because the significant numerical viscosity is already introduced by a Riemann problem solution. The magnitude of numerical viscosity decreases linearly with particle size, however, it becomes comparable with the physical viscosity for most materials when the particle size is about ∼ 1 nm, which hampers the correct accounting for viscous effects in real-life problems. In this study we develop a method for reducing the viscous stresses of numerical origin, for which a correcting viscous stress tensor is constructed on the basis of the analytical solution for discontinuous viscous flow. The use of such correction makes it possible to improve the agreement with the experiment in the simulation of viscous flows.

A new technique for obtaining water-oil capillary pressure curves, based on nuclear magnetic resonance ͑NMR͒ imaging of the saturation distribution in flooded cores is presented. In this technique, a steady-state fluid saturation profile is developed by flooding the core at a constant flow rate. At the steadystate situation where the saturation distribution no longer changes, the local pressure difference between the wetting and nonwetting phases represents the capillary pressure. The saturation profile is measured using an NMR technique and for a drainage case, the pressure in the nonwetting phase is calculated numerically. This paper presents the NMR technique and the procedure for calculating the pressure distribution in the sample. Inhomogeneous samples produce irregular saturation profiles, which may be interpreted in terms of variation in permeability, porosity, and capillary pressure. Capillary pressure curves for North Sea chalk obtained by the new technique show good agreement with capillary pressure curves obtained by traditional techniques.

A new technique for obtaining water-oil capillary pressure curves, based on nuclear magnetic resonance ͑NMR͒ imaging of the saturation distribution in flooded cores is presented. In this technique, a steady-state fluid saturation profile is developed by flooding the core at a constant flow rate. At the steadystate situation where the saturation distribution no longer changes, the local pressure difference between the wetting and nonwetting phases represents the capillary pressure. The saturation profile is measured using an NMR technique and for a drainage case, the pressure in the nonwetting phase is calculated numerically. This paper presents the NMR technique and the procedure for calculating the pressure distribution in the sample. Inhomogeneous samples produce irregular saturation profiles, which may be interpreted in terms of variation in permeability, porosity, and capillary pressure. Capillary pressure curves for North Sea chalk obtained by the new technique show good agreement with capillary pressure curves obtained by traditional techniques.

Orbitally shaken bioreactors are an emerging alternative to stirred-tank bioreactors for large-scale mammalian cell culture, but their fluid dynamics is still not well defined. Among the theoretical and practical issues that remain to be resolved, the characterization of the liquid free surface during orbital shaking remains a major challenge because it is an essential aspect of gas transfer and mixing in these reactors. To simulate the fluid behavior and the free surface shape, we developed a numerical method based on the finite element framework. We found that the large density ratio between the liquid and the gas phases induced unphysical results for the free surface shape. We therefore devised a new pressure correction scheme to deal with large density ratios. The simulations operated with this new scheme gave values of wave amplitude similar to the ones measured experimentally. These simulations were used to calculate the shear stress and to study the mixing principle in orbitally shaken bioreactors.

Injection of fuel into the exhaust system is used to support the operation of exhaust gas aftertreatment systems. When injecting a fluid into the exhaust system, one major challenge is to design the exhaust system for optimal fuel distribution and to define an appropriate injection pressure. Simulation techniques are a suitable measure to support the corresponding development process. Hence, the project "Exhaust Fuel Injection" was initiated. Project target is the alignment of simulation methods and measurement techniques to predict the HC distribution in radial and axial direction at the inlet of a catalyst. This includes the definition of suitable measurement techniques to determine the hydrocarbon concentrations upstream of a catalyst. Transient 3D Computational Fluid Dynamics (CFD) simulation was used to model the fuel injection into a purpose-built exhaust system. The simulation results of the distribution of hydrocarbons at catalyst inlet in radial and axial direction are compared with measurements performed at an engine test bench. In total 18 variations were simulated and measured and twelve of them showed deviations in the uniformity index (UI) below 2 %. Only two variations resulted in deviations in UI above 3%. The trends in axial distribution showed good correlation between test bench and simulation. Especially the influence of injection pressure and operating point was predicted well by the simulation.

The Particle Finite Element Method (PFEM) is a Lagrangian finite element method with frequent remeshing, particularly suited for the simulation of fluid motions with evolving free surfaces, e.g., in the case of breaking waves or fluid-structure interactions with large displacements of the interaction surface. While the method has been successfully employed in a number of different engineering applications, there are several circumstances of practical interest where the Lagrangian nature of the method makes it difficult to enforce non-homogeneous boundary conditions. A novel mixed Lagrangian-Eulerian technique is proposed to the purpose of simplifying the imposition of this type of conditions with the PFEM. The method is simple to implement and computationally convenient, since only nodes on the boundary are considered Eulerian, while nodes inside the fluid body maintain their Lagrangian nature. A number of 2D and 3D examples, with analytical and numerical validations, confirm the excellent performance of the method.

In order to investigate effects of injection rate and aquifer influx in imbibition processes and also wettability behaviour for CO 2 storage in aquifers, two representative fluids are chosen for relative permeability measurements. These two fluids represent CO 2 and brine at the reservoir conditions. The first set of experiments is done by n-heptane and a mixture of glycerol and water, flowing in a glass beads porous medium. The density difference and viscosity ratio are designed to be in the range of CO 2-brine systems normally found at reservoir conditions. Another set of experiments is designed based on dodecane and a mixture of glycerol and water. The second mixture is chosen so that the same ratios of density differences and viscosity ratios are maintained. Interfacial tension and contact angles are measured for both cases. By this set up, two cases of strongly water-wet and water-wet systems are designed. The purpose of this study is to quantify the impact of wettability and flow rate through relative permeability experiments. Results show that the relative permeability is sensitive to both rate and wettability, and after interpreting the data from experiments in a history matching process, based on the effects of drainage and imbibition rates and also the effect of wettability, correlations are developed to predict the amount of CO 2 trapped in the pores. This newly developed method will be useful in obtaining good estimations of real case trapping volume in CO 2 storage processes. Scaling analysis of the experiment shows that the tests are well designed in the range of real reservoir conditions.

Coupled large eddy simulation and the discrete element method are applied to study turbulent particle-laden flows, including particle dispersion and agglomeration, in a channel. The particle-particle interaction model is based on the Hertz-Mindlin approach with Johnson-Kendall-Roberts cohesion to allow the simulation of van der Waals forces in a dry air flow. The influence of different particle surface energies, and the impact of fluid turbulence, on agglomeration behaviour are investigated. The agglomeration rate is found to be strongly influenced by the particle surface energy, with a positive relationship observed between the two. Particle agglomeration is found to be enhanced in two separate regions within the channel. First, in the near-wall region due to the high particle concentration there driven by turbophoresis, and secondly in the buffer region where the high turbulence intensity enhances particle-particle interactions.