A proposed NMR solution for multi-phase flow fluid detection

In the petroleum industry,detection of multi-phase fluid flow is very important in both surface and down-hole measurements.Accurate measurement of high rate of water or gas multi-phase flow has always been an academic and industrial focus.NMR is an efficient and accurate technique for the detection of fluids;it is widely used in the determination of fluid compositions and properties.This paper is aimed to quantitatively detect multi-phase flow in oil and gas wells and pipelines and to propose an innovative method for online nuclear magnetic resonance(NMR)detection.The online NMR data acquisition,processing and interpretation methods are proposed to fill the blank of traditional methods.A full-bore straight tube design without pressure drop,a Halbach magnet structure design with zero magnetic leakage outside the probe,a separate antenna structure design without flowing effects on NMR measurement and automatic control technology will achieve unattended operation.Through the innovation of this work,the application of NMR for the real-time and quantitative detection of multi-phase flow in oil and gas wells and pipelines can be implemented.

Numerical simulation of complex multi-phase fluid of casting process and its applications

The fluid of casting process is a typical kind of multi-phase flow. Actually, many casting phenomena have close relationship with the multi-phase flow, such as molten metal filling process, air entrapment, slag movement, venting process of die casting, gas escaping of lost foam casting and so on. Obviously, in order to analyze these phenomena accurately, numerical simulation of the multi-phase fluid is necessary. Unfortunately, so far, most of the commercial casting simulation systems do not have the ability of multi-phase flow modeling due to the difficulty in the multi-phase flow calculation. In the paper, Finite Different Method (FDM) technique was adopt to solve the multi-phase fluid model. And a simple object of the muiti-phase fluid was analyzed to obtain the fluid rates of the liquid phase and the entrapped air phase.

Multi-phase computer modeling and laboratory study of dust capture by an inertial Vortecone scrubber

Dust generated in mining and tunneling activities is hazardous to health of persons and safety of operations. These projects employ pick-milling machines to extract minerals and rock by mechanical breakage.The machines are equipped with flooded-bed scrubbers that encase dust particles within fine water films as particles encounter a flooded wire-mesh screen. A major disadvantage is that the screen gets clogged when particles become trapped within the wire mesh, reducing airflow through the scrubber and increasing ambient dust concentrations. Thus, the system requires frequent maintenance or replacement. The application of a Vortecone scrubber as an improved alternative to conventional fibrous type scrubbers is investigated. A Vortecone forces dust-laden air and water to follow a complex, rapidly swirling motion.The momentum drives dust particles towards the periphery where they are captured by the water film.The operating characteristics of a reduced-scale physical model of a Vortecone, with its primary axis mounted in the horizontal orientation, was analyzed numerically and experimentally. Computational fluid dynamics(CFD) models depicting the spraying action and multi-phase air/water flows using the volume of fraction(VOF) approach, are presented. Experimental results, utilizing an optical particle counting technique to establish the dust-cleaning capabilities of the model, are also described.

Micro-nano-fabrication of green functional materials by multiphase microfluidics for environmental and energy applications

Multiphase microfluidic has emerged as a powerful platform to produce novel materials with tailor-designed functionalities,as microfluidic fabrication provides precise controls over the size,component,and structure of resultant materials.Recently,functional materials with well-defined micro-/nanostructures fabricated by microfluidics find important applications as environmental and energy materials.This review first illustrated in detail how different structures or shapes of droplet and jet templates are formed by typical configurations of microfluidic channel networks and multiphase flow systems.Subsequently,recent progresses on several representative energy and environmental applications,such as water purification,water collecting and energy storage,were overviewed.Finally,it is envisioned that integrating microfluidics and other novel materials will play increasing important role in contributing environmental remediation and energy storage in near future.

纳米多孔介质中的流体流动

Fluid flow at nanoscale is closely related to many areas in nature and technology(e.g.,unconventional hydrocarbon recovery,carbon dioxide geo-storage,underground hydrocarbon storage,fuel cells,ocean desalination,and biomedicine).At nanoscale,interfacial forces dominate over bulk forces,and nonlinear effects are important,which significantly deviate from conventional theory.During the past decades,a series of experiments,theories,and simulations have been performed to investigate fluid flow at nanoscale,which has advanced our fundamental knowledge of this topic.However,a critical review is still lacking,which has seriously limited the basic understanding of this area.Therefore herein,we systematically review experimental,theoretical,and simulation works on single-and multi-phases fluid flow at nanoscale.We also clearly point out the current research gaps and future outlook.These insights will promote the significant development of nonlinear flow physics at nanoscale and will provide crucial guidance on the relevant areas.

Wellbore drift flow relation suitable for full flow pattern domain and full dip range

Aiming at the simulation of multi-phase flow in the wellbore during the processes of gas kick and well killing of complex-structure wells(e.g.,directional wells,extended reach wells,etc.),a database including 3561 groups of experimental data from 32 different data sources is established.Considering the effects of fluid viscosity,pipe size,interfacial tension,fluid density,pipe inclination and other factors on multi-phase flow parameters,a new gas-liquid two-phase drift flow relation suitable for the full flow pattern and full dip range is established.The distribution coefficient and gas drift velocity models with a pipe inclination range of-90°–90°are established by means of theoretical analysis and data-driven.Compared with three existing models,the proposed models have the highest prediction accuracy and most stable performance.Using a well killing case with the backpressure method in the field,the applicability of the proposed model under the flow conditions with a pipe inclination range of-90°–80°is verified.The errors of the calculated shut in casing pressure,initial back casing pressure and casing pressure when adjusting the displacement are 2.58%,3.43%,5.35%,respectively.The calculated results of the model are in good agreement with the field backpressure data.

Numerical simulation of flow field and optimization of structure parameters of seed precipitation tank for production of alumina

In order to overcome the defects of air-agitated seed precipitation, such as scaring, liquid short-(circuiting,) the three-dimension flow fields with different structure are numerically simulated by computational fluid dynamics software. Euler/Euler approach was used to study the effects of structure on the flow field in the tank. Multi-fluid model, body-fitted coordinates and multi-block gird were adopted in the simulation. The simulating results are well consonant with the practical situations. The flow field is improved obviously when the flow velocity increases from (0.089m/s) to 0.1920.300m/s at the bottom of the optimized tank and therefore the scaring is reduced greatly in the industrial production. With a gathering sill, the problem of short-circuiting, which always appeares in the upper of the tank, can be solved very well.

An efficient multi-resolution SPH framework for multi-phase fluid-structure interactions

Applying different spatial and temporal resolutions for different sub-systems is an effective approach to increase computational efficiency for particle-based methods. However, it still has many challenges in terms of achieving an optimized computational efficiency and maintaining good numerical robustness and accuracy for the simulation of multi-phase flows involving large density ratio and interacting with rigid or flexible structures. In the present work, based on the multi-resolution smoothed particle hydrodynamics(SPH) method [Zhang et al., JCP 429, 110028(2021)], an efficient multi-resolution SPH framework for multi-phase fluid-structure interactions(FSI) is proposed. First, an efficient multi-phase model, exploiting different density reinitialization strategies instead of applying different formulations to implement mass conservation to the light and heavy phases, respectively,is developed and the same artificial speed of sound for both phases can be used. Then, the transport velocity formulation is rewritten by applying temporal local flow state dependent background pressure to eliminate the unnatural voids, unrealistic phase separation and decrease the numerical dissipation. Finally, the one-sided Riemann-based solid boundary condition is modified to handle the FSI coupling in both single-and multi-resolution scenarios in the triple point. A set of examples involving multi-phase flows with high density ratio, complex interface and multi-phase FSI are studied to demonstrate the efficiency, accuracy and robustness of the present method.

A Hybrid Scheme of Level Set and Diffuse Interface Methods for Simulating Multi-Phase Compressible Flows

We propose a hybrid scheme combing the level set method and the multicomponent diffuse interface method to simulate complex multi-phase flows.The overall numerical scheme is based on a sharp interface framework where the level set method is adopted to capture the material interface,the Euler equation is used to describe a single-phase flow on one side of the interface and the six-equation diffuse interface model is applied to model the multi-phase mixture or gas-liquid cavitation on the other side.An exact Riemann solver,between the Euler equation and the six-equation model with highly nonlinear Mie-Gr¨uneisen equations of state,is developed to predict the interfacial states and compute the phase interface flux.Several numerical examples,including shock tube problems,cavitation problems,air blast and underwater explosion applications are presented to validate the numerical scheme and the Riemann solver.

A General Moving Mesh Framework in 3D and its Application for Simulating the Mixture of Multi-Phase Flows

In this paper, we present an adaptive moving mesh algorithm for meshesof unstructured polyhedra in three space dimensions. The algorithm automaticallyadjusts the size of the elements with time and position in the physical domain to resolvethe relevant scales in multiscale physical systems while minimizing computationalcosts. The algorithm is a generalization of the moving mesh methods basedon harmonic mappings developed by Li et al. [J. Comput. Phys., 170 (2001), pp. 562-588, and 177 (2002), pp. 365-393]. To make 3D moving mesh simulations possible,the key is to develop an efficient mesh redistribution procedure so that this part willcost as little as possible comparing with the solution evolution part. Since the meshredistribution procedure normally requires to solve large size matrix equations, wewill describe a procedure to decouple the matrix equation to a much simpler blocktridiagonaltype which can be efficiently solved by a particularly designed multi-gridmethod. To demonstrate the performance of the proposed 3D moving mesh strategy,the algorithm is implemented in finite element simulations of fluid-fluid interface interactionsin multiphase flows. To demonstrate the main ideas, we consider the formationof drops by using an energetic variational phase field model which describesthe motion of mixtures of two incompressible fluids. Numerical results on two- andthree-dimensional simulations will be presented.

Implication of Geochemical Simulation for CO2 Storage Using Data of York Reservoir

In this paper, we build up a three-dimensional model for CO2 storage in the deep reservoir. And this paper gives the mathematical formalism of combined geochemical and multi-phase flow. The results give us the information about geochemical changing caused by CO2 injection into aqueous, the dissolution or precipitation of reservoir minerals caused by aqueous components change, the change of water density, also the differences between this model and the simulation model without considering geochemical. The basic data for simulation is from York Reservoir.

The Game Theoretical Approach for Multi-phase Complex Systems in Chemical Engineering

This paper explores the application of noncooperative game theory together with the concept of Nash equilibrium to the investigation of some basic problems on multi-scale structure, especially the meso-scale structure in the multi-phase complex systems in chemical engineering. The basis of this work is the energy-minimization-multi-scale （EMMS） model proposed by Li and Kwauk （1994） and Li, et al. （2013） which identifies the multi-scale structure as a result of ＇compromise-in-competition between dominant mechanisms＇ and tries to solve a multi-objective optimization problem. However, the existing methods often integrate it into a problem of single objective optimization, which does not clearly reflect the ＇compromise-in-competition＇ mechanism and causes heavy computation burden as well as uncertainty in choosing suitable weighting factors. This paper will formulate the compromise in competition mechanism in EMMS model as a noncooperative game with constraints, and will describe the desired stable system state as a generalized Nash equilibrium. Then the authors will investigate the game theoretical approach for two typical systems in chemical engineering, the gas-solid fluidiza- tion （GSF） system and turbulent flow in pipe. Two different cases for generalized Nash equilibrinm in such systems will be well defined and distinguished. The generalize Nash equilibrium will be solved accurately for the GSF system and a feasible method will be given for turbulent flow in pipe. These results coincide with the existing computational results and show the feasibility of this approach, which overcomes the disadvantages of the existing methods and provides deep insight into the mechanisms of multi-scale structure in the multi-phase complex systems in chemical engineering.

ELECTROMAGNETIC TOMOGRAPHY (EMT): THEORETICAL ANALYSIS OF THE FORWARD PROBLEM

Inductance-bared electromagnetic tomography (EMT) is a novel industrial process tomographic technique. Exact expressions of the magnetic field distribution in a two-dimensional object space were derived by analytically solving the forward problem for a particular two-component pow. The physical mechanisms within the sensor and the detectability limits of the EMT technique were quantitatively analyzed. Direct mathematical expressions for the field sensitivity and the sensitivity maps were established. To a certain extent, mathematical and theoretical bares are given for quantitative design of the sensor, detectability analysis of the EMT technique and image reconstruction of two-component processes based on the linear back-projection algorithm.

Influence of Diesel Nozzle Geometry on Cavitation Using Eulerian Multi-Fluid Method

Dependent on automatically generated unstructured grids, a comprehensive computational fluid dynamics(CFD)numerical simulation is performed to analyze the influence of nozzle geometry on the internal flow characteristics of a multi-hole diesel injector with the multi-phase flow model based on Eulerian multi-fluid method.The diesel components in nozzle are considered as two continuous phases, diesel liquid and diesel vapor respectively.Considering that both of them are fully coupled and interpenetrated, sepa...

Crude oil wax:A review on formation,experimentation,prediction,and remediation techniques

Wax deposition during crude oil production,transportation,and processing has been a headache since the early days of oil utilization.It may lead to low mobility ratios,blockage of production tubing/pipelines as well as fouling of surface and processing facilities,among others.These snags cause massive financial constraints increasing projects’turnover.Decades of meticulous research have been dedicated to this problem that is worth a review.Thus,this paper reviews the mechanisms,experimentation,thermodynamic and kinetic modeling,prediction,and remediation techniques of wax deposition.An overall assessment suggests that available models are more accurate for single than multi-phase flows while the kind of remediation and deployment depend on the environment and severity level.In severe cases,both chemical and mechanical are synergistically deployed.Moreover,future prospective research areas that require attention are proposed.Generally,this review could be a valuable tool for novice researchers as well as a foundation for further research on this topic.

Mechanism of the Large Surface Deformation Caused by Rayleigh-Taylor Instability at Large Atwood Number

Studying the dynamical behaviors of the liquid spike formed by Rayleigh-Taylor instability is important to understand the mechanisms of liquid atomization process. In this paper, based on the information on the velocity and pressure fields obtained by the coupled-level-set and volume-of- fluid (CLSVOF) method, we describe how a freed spike can be formed from a liquid layer under falling at a large Atwood number. At the initial stage when the surface deformation is small, the amplitude of the surface deformation increases exponentially. Nonlinear effect becomes dominant when the amplitude of the surface deformation is comparable with the surface wavelength (~0.1λ). The maximum pressure point, which results from the impinging flow at the spike base, is essential to generate a liquid spike. The spike region above the maximum pressure point is dynamically free from the bulk liquid layer below that point. As the descending of the maximum pressure point, the liquid elements enter the freed region and elongate the liquid spike to a finger-like shape.

Towards a Micromechanical Understanding of Landslides—Aiming at a Combination of Finite and Discrete Elements with Minimal Number of Degrees of Freedom

In this paper, we propose a combination of discrete elements for the soil and finite elements for the fluid flow field inside the pore space to simulate the triggering of landslides. We give the details for the implementation of third order finite elements (“P2 with bubble”) together with polygonal discrete elements, which allows the formulation with a minimal number of degrees of freedom to save computer time and memory. We verify the implementation with several standard problems from computational fluid dynamics, as well as the decay of a granular step in a fluid as test case for complex flow.

Further Stabilization and Power Density Improvement of Stack-Type Thermoelectric Power Generating Module with Biphasic Medium by Using Various Flexible Metals as Electrodes

In order to realize further stability of a stack-type thermoelectric power generating module (i.e. no electrical connections inside), flexible materials of metal springs and/or rods having restoring forces were installed between lower-temperature-sides of thermoelectric elements. These flexible materials were expected to play three important roles of interpolating different thermal expansions of the module components, enlarging heat removal area and penetration of any media through themselves. Then, a low-boiling-point medium (i.e. NOVEC manufactured by 3M Japan Ltd.) was also applied for a high-speed direct heat removal via its phase change from the lower-temperature-sides of the thermoelectric elements in the proposing stack-type thermoelectric power generating module. No electrical disconnections inside the module were confirmed for more than 9 years of use, indicating further module stability. The power generating density was improved to about 120 mW·m-2 with SUS304 springs having 0.7 mm diameter. Increasing power generating density can be expected in terms of suitable selection of flexible metal with high Vickers hardness, cavities control on the spring surface, more vigorous multiphase flow with adding powders to the medium and optimization of the module configurations according to numerical simulations.

Numerical modeling of sediment transport based on unsteady and steady flows by incompressible smoothed particle hydrodynamics method

The purpose of the present paper is to introduce a simple two-part multi-phase model for the sediment transport problems based on the incompressible smoothed particle hydrodynamics（ISPH） method. The proposed model simulates the movement of sediment particles in two parts. The sediment particles are classified into three categories, including the motionless particles, moving particles behave like a rigid body, and moving particles with a pseudo fluid behavior. The criterion for the classification of sediment particles is the Bingham rheological model. Verification of the present model is performed by simulation of the dam break waves on movable beds with different conditions and the bed scouring under steady flow condition. Comparison of the present model results, the experimental data and available numerical results show that it has good ability to simulate flow pattern and sediment transport.

PARTICLE METHODS FOR COMPLEX FLOWS IN CHEMICAL ENGINEERING ——THE PSEUDO-PARTICLE APPROACH

The multi-scale structures of complex flows in chemical engineering have been great challenges to the design and scaling of such systems, and multi-scale modeling is the natural way in response. Particle methods (PMs) are ideal constituents and powerful tools of multi-scale models, owing to their physical fidelity and computational simplicity. Especially, pseudo-particle modeling (PPM, Ge & Li, 1996; Ge & Li, 2003) is most suitable for molecular scale flow prediction and exploration of the origin of multi-scale structures; macro-scale PPM (MaPPM, Ge & Li, 2001) and similar models are advantageous for meso-scale simulations of flows with complex and dynamic discontinuity, while the lattice Boltzmann model is more competent for homogeneous media in complex geometries; and meso-scale methods such as dissipative particle dynamics are unique tools for complex fluids of uncertain properties or flows with strong thermal fluctuations. All these methods are favorable for seamless interconnection of models for different scales. However, as PMs are not originally designed as either tools for complexity or constituents of multi-scale models, further improvements are expected. PPM is proposed for microscopic simulation of particle-fluid systems as a combination of molecular dynamics (MD) and direct simulation Monte-Carlo (DSMC). The collision dynamics in PPM is identical to that of hard-sphere MD, so that mass, momentum and energy are conserved to machine accuracy. However, the collision detection procedure, which is most time-consuming and difficult to be parallelized for hard-sphere MD, has been greatly simplified to a procedure identical to that of soft-sphere MD. Actually, the physical model behind such a treatment is essentially different from MD and is more similar to DSMC, but an intrinsic difference is that in DSMC the collisions follow designed statistical rules that are reflection of the real physical processes only in very limited cases such as dilute gas. PPM is ideal for exploring the mechanism of complex flows ab initio. In final analysis, the complexity of flow behavior is shaped by two components on the micro-scale: the relative displacements and interactions of the numerous molecules. Adding to the generality of the characteristics of complex system as described by Li and Kwauk (2003), we notice that complex structures or behaviors are most probably observed when these two components are competitive and hence they must compromise, as in the case of emulsions and the so-called soft-matter that includes most bio-systems. When either displacement or interaction is dominant, as in the case of dilute gas or solid crystals, respectively, complexity is much less spectacular. Most PMs consist explicitly of these two components, which is operator splitting in a numerical sense, but it is physically more meaningful and concise in PPM. The properties of the pseudo-particle fluid are in good conformance to typical simple gas (Ge et al., 2003; Ge et al., 2005). The ability of PPM to describe the dynamic transport process on the micro-scale in heterogeneous particle-fluid systems has been demonstrated in recent simulations (Ge et al., 2005). Especially, the method has been employed to study the temporal evolution of the stability criterion in the energy minimization multi-scale model (Li & Kwauk, 1994), which confirms its monotonously asymptotic decreasing as the model has assumed (Zhang et al., 2005). Massive parallel processing is also practiced for simulating particle-fluid systems in PPM, indicating an optimistic prospect to elevate the computational limitations on their wider applications, and exploring deeper underlying mechanism in complex particle-fluid systems.