Two-phase Flow Theory Research Articles

Optimization on the Structure of Ceramic Nozzles by FLUENT Simulation

Based on the theory of gas-solid two-phase flow, abrasive flows in ceramic nozzles with different structures are simulated by FLUENT software and the outflow velocity of particles is compared. The results show: the abrasive outflow velocity of ceramic nozzle with cone angle is large than that of ceramic nozzle with through-hole structure, and the distribution of abrasive particles is more uniform for the ceramic nozzle with cone angle. The best entrance cone angle of ceramic nozzle is 10o30o, and the maximum abrasive outflow velocity of the ceramic nozzle with cone angle of 20o is 90.16 m/s. The simulation results have a good agreement with the experimental results.

Kinematic Law of Solids on a Drilling Fluid Vibrating Screen

Based on solid-liquid two-phase flow theory and dynamic principle of a vibrating screen, the kinematic behavior of solids on the vibrating screen is studied. In submersed condition, the formula of suspension size of solids, the terms of free flight and suspension motions are developed, and the kinematic behavior of solids when they enter free flight is discussed. After the liquid endpoint, the kinematic terms of sliding backward and forward, free flight, remaining in contact with the screen and staying stationary on the screen for solids are obtained, and a mathematical model that can predict solids conveyance velocity is developed.

Mechanism analysis and process optimization of sand and plug removal with rotating jet in horizontal well

In the view of the problems existing in horizontal well, such as sand depositing and cleaning difficulty of borehole, a technology with rotating jet suitable to resolution of the problems was presented. Based on liquid-solid two-phase flow theory, the analyses on the sand movement law and the swirling field influential factors were conducted. Results show that: 1) With the increasing of displacement in horizontal section annulus, swirling field strength increases, and when the displacement is constant, the closer from the nozzle, the stronger the swirling field strength is; 2) Head rotating speed and liquid viscosity have little influence on the swirling field strength, but the sand-carrying rate of fluid can increase by increasing liquid viscosity in a certain range; 3) Rotating the string and reducing its eccentricity in annulus are conducive for sand migration in the annulus; 4) The sand can be suspended and accelerated again and the swirling field strength is enhanced by the helix agitator. Hence, the research results provide the theoretical basis for the design and application of rotating jet tool.

A review of recent experimental investigations and theoretical analyses for pulsating heat pipes

Pulsating heat pipe (PHP), or oscillating heat pipe (OHP), a novel type of highly efficient heat transfer component, has been widely applied in many fields, such as in space-borne two-phase thermal control systems, in the cooling of electronic devices and in energy-saving technology, etc. In the present paper, the characteristics and working principles of the PHPs are introduced and the current researches in the field are described from the viewpoint of experimental tests, theoretical analyses as well as practical applications. Besides, it is found that the state-of-the-art experimental investigations on the PHPs are mainly focused on the flow visualization and the applications of nanofluids and other functional fluids, aiming at enhancing the heat transfer performance of the PHPs. In addition, it is also pointed out that the present theoretical analyses of the PHP are restricted by further development of two-phase flow theories, and are concentrated in the non-linear analyses. Numerical simulations are expected to be another research focus, in particular of the combination of the nanofluids and functional fluids.

Load Analysis of Offshore Wind Turbine Tower Based on Multi-Physics Coupling Analysis

The offshore wind turbine (OWT) tower is the important support of the whole wind turbine components, it is necessary to design and research the tower reasonably in order to ensure reliable operation of the OWT. In this paper, 3MW OWT tower is chosen as the object of study. A gas-liquid-solid model of the OWT tower and its external environment is built using COMSOL Multiphysics software. Combined with the two-phase flow theory of gas-liquid, loads of the tower under the coupling action of wind and wave are computed, which provides a new direction for the load analysis of the tower. The results calculated by this method are closer to the physical truth, which provides a more reliable basis for analyzing the fatigue life of the tower further.

이상 유동에 놓인 관군의 표면에 작용하는 압력 분포

이상 횡 유동은 응축기, 증발기와 원자로 증기발생기와 같은 쉘과 튜브의 열 교환기에서 볼 수 있다. 이상 유동장에 놓인 구조물에 작용하는 수동력을 이해하기 위해서는 이상유동의 특성을 이해하는 것이 중요하다. 이상 유동의 유동특성과 유동변수를 소개하고 관군에서의 압력손실과 실린더에 작용하는 압력분포에 의한 수동력을 평가하기 위한 실험을 수행하였다, 실험부 입구에서 이상유동은 혼합되었으며 실험은 횡 방향 이상 유동장에 놓인 정규 삼각형 배열을 갖는 관군을 사용하여 수행하였다. 관군에서의 흐름방향 압력손실을 측정하여 이상유동의 마찰승수를 계산하고 이론적 결과와 비교하였다. 또한 특정 실린더에 작용하는 원주 방향 압력 분포의 측정결과와 이상유동의 기초이론에 근거하여 압력손실계수의 분포 및 항력계수에 미치는 체적건도와 단위면적당 질량유량의 효과를 평가하였다. 튜브 표면에 작용하는 측정된 압력을 수치해석방법으로 적분하여 항력계수를 계산하였다. 작은 질량 유량의 경우에 측정된 마찰 승수는 기존의 이론 결과와 잘 일치하며 압력분포에 의한 항력계수에 작용하는 기공률의 영향은 기존의 실험결과와 정성적으로 유사한 경향을 보이고 있다.

Inverse Problem Models of Oil-Water Two-Phase Flow Based on Buckley-Leverett Theory

Based on Buckley-Leverett theory, one inverse problem model of the oil-water relative permeability was modeled and proved when the oil-water relative permeability equations obey the exponential form expression, and under the condition of the formation permeability that natural logarithm distribution always obey normal distribution, the other inverse problem model on the formation permeability was proved. These inverse problem models have been assumed in up-scaling cases to achieve the equations by minimization of objective function different between calculation water cut and real water cut, which can provide a reference for researching oil-water two-phase flow theory and reservoir numerical simulation technology.

Prediction on Vibration Response of Cantilever Particle-damping Beam Based on Two-phase Flow Theory of Gas-particle

An improved analytical model using the two-phase flow theory of gas-particle is presented based on previous work,in which the effects due to inter-particle collision and friction are all expressed as the equivalent viscosities in a unified way.This makes the entire model has a more complete uniformity and provides convenience for further studies in depth.The analysis results of the free vibration and forced vibration of SDOF systems with particle damping show that the prediction of the improved model is more accuracy than that of the origin model.Furthermore,the forced response of a typical continuum structure,i.e.the cantilever particle-damping beam is predicted and analyzed using this improved model and the finite element method.Numerical results show that the particle damping is a kind of nonlinear damping,which is highly depended on the vibration amplitude.When the particle damper is exerted on different positions of the beam,the damping properties can present an obvious change.The ideal damping effect can be achieved by putting the particle damper on the position of the structure with high-level vibration.The improved model of equivalent viscous damping based on two-phase flow theory of gas-particle developed can lay a theoretical foundation for the prediction on the vibration and sound radiation of more complicated particle-damping composite structures.

Gas flow in Callovo-Oxfordian claystone (COx): results from laboratory and field-scale measurements

AbstractTo understand the fate and impact of gas produced within a repository for radioactive waste, a series of laboratory and field scale experiments have been performed on the Callovo-Oxfordian claystone (COx), the proposed host rock for the French repository. Results show the movement of gas is through a localized network of pathways, whose properties vary temporarily and spatially within the claystone. Significant evidence exists from detailed laboratory studies for the movement of gas along highly unstable pathways, whose aperture and geometry vary as a function of local stress, gas and porewater pressures. The coupling of these parameters results in the development of significant time-dependent effects, impacting on all aspects of COx behaviour, from gas breakthrough time, to the control of deformation processes. Variations in gas entry, breakthrough and steady-state pressures are indicative of microstructural heterogeneity which exerts an important control on the movement of gas. The localization of gas flow is also evident in preliminary results from the large scale gas injection test (PGZ) where gas flow is initially focussed within the excavation damaged zone (EDZ), which acts as a preferential pathway for gas. Numerical models based on conventional two-phase flow theory are unable to adequately describe the detailed observations from laboratory tests.

Computational Fluid Dynamics Analysis of Working Fluid Flow and Machining Debris Movement in End Electrical Discharge Milling and Mechanical Grinding Compound Machining

The working fluid flow and the machining debris movement in the machining gap exercise a great influence on the process performance in end electrical discharge milling and mechanical grinding compound machining. In this paper, the working fluid flow and the machining debris movement in the machining gap are modeled based on the liquid-solid two-phase flow theory. The gap flow field is calculated with the software of Fluent, and the velocity field and the pressure field are analyzed. The results show that in the gap flow field of the compound machining, the working fluid flow can be accelerated, and the machining debris can be ejected timely by the rapid rotation of the tool electrode, so the compound process performance can be enhanced.

Study on Dynamic Properties of Solid-Liquid Separator Entrance

Using of two-phase flow theory to set up liquid-solid separator inside the water and slag particles separation model, studied the strainer inlet and the relative relationship between the inlet and outlet, obtained the corresponding two-phase flow rate and the concentration distribution. It is shown that, entry form using the reverse side of slag cyclone and centrifugal separation methods to achieve the self-scouring effect and fluid, more conducive to the dispersed particles and continuous phase separation; From the strainer inlet and outlet position relationship point of view, taking into account the water uses from the side into the bottom and out from the top side is more reasonable and effective.

Calculation of Chip Removal Air Volume of Blasthole Drill

Whether selection of chip removal air volume is reasonable or not, do affect the performance of blasthole drill and bit’s life. How to calculate air volume always make the designers confused. In this paper, writer use theory of gas-solid two-phase flow and energy principle combined with characteristic of rock ballasts from the mine site to determine particle rising speed, free floating speed and air flow rate of the rock ballasts. And according to the relation between particle and particle group’s floating speed calculate floating speed and the corresponding chip removal air volume among different diameter of particle of the same minerals. It can provide a method of calculation to designer, which is very reference value to for the practical application.

Study on Consolidation Mechanism of Debris Flow Deposit

The damage of debris flow effected on highway subgrade, pavement, protective structure, bridge and culvert laid on debris flow impact fracture and buried damage. Thus far, research on debris flow burying mechanism is still fuzzy. According to the two-phase flow theory of debris flow deposit, analyzed the consolidation mechanical mechanism of highway debris flow deposit. On the basis of Terzaghi one-dimensional consolidation theory, established the consolidation formula, which described the change process of excess pore water pressure, consolidation degree, settlement and compression with the consolidation time and deposit size, and then verified the correctness and feasibility of the formula by the indoor consolidation test. It adopted these results and combined it with the field survey data, it could develop a proper program for emergency mitigation of highway debris flow buried disaster more quickly and accurately.

Study on Consolidation Mechanism of Debris Flow Deposit

The damage of debris flow effected on highway subgrade, pavement, protective structure, bridge and culvert laid on debris flow impact fracture and buried damage. Thus far, research on debris flow burying mechanism is still fuzzy. According to the two-phase flow theory of debris flow deposit, analyzed the consolidation mechanical mechanism of highway debris flow deposit. On the basis of Terzaghi one-dimensional consolidation theory, established the consolidation formula, which described the change process of excess pore water pressure, consolidation degree, settlement and compression with the consolidation time and deposit size, and then verified the correctness and feasibility of the formula by the indoor consolidation test. It adopted these results and combined it with the field survey data, it could develop a proper program for emergency mitigation of highway debris flow buried disaster more quickly and accurately.

Study of the Effects of Shearer’ Kinematic Parameters on on-Way Distribution of Dust on Coal Face

In order to research the effects of shearer’ kinematical parameters on on-way distribution of dust on coal face, according to the theory of suspension gas-solid two-phase flow and the theory of cutting dust formation, mathematical model of on-way dust concentration was established, methods of determining parameters were given, dust migration was simulated by using the discrete phase model (DPM) in FLUENT, on-way distribution regularity of dust was found. According to calculation of the quantity of cutting dust at different hauling speed and different rotational speed of drum, dust migration was simulated and migration regularity was showed as follows: dust concentration of every point on a coal face increased as hauling speed decreased or rotational speed increased. In addition, with rotational speed increased, the position of concentration maximum moved a little along downwind.

Numerical simulation of ice accretions on an aircraft wing

An approach based on the Eulerian two-phase flow theory to numerically simulate ice accretions on an aircraft wing is developed. The air flowfield is obtained through Euler flow computation. The water dropletsʼ flowfield is solved through proposing a permeable wall to simulate the droplets impingement. The droplets collection efficiency is calculated according to the droplets velocity and apparent density distribution. The thermodynamic model of ice accretion is based on the classical Messinger model and an integral boundary layer method is employed to account for roughness effect in calculating the convective heat transfer coefficient. The ice shape is built with the assumption that ice grows in the direction normal to the airfoil/wing surface. The ice accretions on a NACA0012 airfoil and a GLC-305 wing model under different icing conditions are evaluated and the comparison between the predicted results and experimental data indicates that the simulation approach developed in this paper is feasible and effective.

Orientation of cylindrical particles in gas–solid circulating fluidized bed

The orientation of cylindrical particles in a gas–solid circulating fluidized bed was investigated by establishing a three-dimensional Euler–Lagrange model on the basis of rigid kinetics, impact kinetics and gas–solid two-phase flow theory. The resulting simulation indicated that the model could well illustrate the orientation of cylindrical particles in a riser during fluidization. The influences of bed structure and operation parameters on orientation of cylindrical particles were then studied and compared with related experimental results. The simulation results showed that the majority of cylindrical particles move with small nutation angles in the riser, the orientation of cylindrical particles is affected more obviously by their positions than by their slenderness and local gas velocities. The simulation results well agree with experiments, thus validating the proposed model and computation.

Numerical studies of electrically induced pattern formation by coupling liquid dielectrophoresis and two‐phase flow

Electrically induced patterning process, as a novel micro- or nano-structuring approach for fabrication of various micro- or nano-systems, is usually implemented by applying a voltage to an electrode pair consisting of a patterned or non-patterned template and a polymer-coated substrate separated in parallel by an air gap, followed by photo- or thermo-curing of the fluidic and dielectric polymer. The analyses performed so far to characterize this patterning process have been based on linear thermodynamics for a thermally instable thin film perturbed by an electrostatically induced hydraulic pressure. For mathematical simplicity, these analyses were formulated only for a flat template and a flat film surface with infinite planar area, demonstrating the tendency of initial pattern growth on the polymer film, but being unable to visualize the dynamic evolution of micro- or nano-structure growth throughout the patterning process for a real-life template in practical applications. This paper attempts to provide another insight into this patterning process from a viewpoint of liquid dielectrophoresis (L-DEP), by presenting an approach for numerical simulation of the patterning process based on a coupling of L-DEP and two-phase flow theories. First, a numerical analysis has been made for the electrocoalescence of a water droplet with bottom water in silicone oil to benchmark effectiveness of the proposed numerical approach against published experimental observations. More numerical results have then been provided to show effects of some process variables on the evolution of the polymer micro- or nano-structures for this patterning process.

A general two-phase turbulent flow model applied to the study of sediment transport in open channels

A numerical model for the general description of the sediment-laden flow is developed based on an Euler–Euler approach of the two-phase turbulent flow theory. The basic equations of the model are the Reynolds averaged equations of motion for both the fluid and the sediment phase in addition to the Reynolds averaged continuity equations for the mixture and for the sediment phase. The fluid phase and the sediment phase are coupled through their interaction forces including resistance force, inertia force, and lift force. Turbulence closure of the fluid phase is based on the conventional k– ε model while an algebraic particle turbulence model is applied to the sediment phase. The numerical method is based on the modified SIMPLE scheme. The model is applied to the computation of saturated sediment-laden flows and also the non-equilibrium transport of sediment by unidirectional flows under simple erosion and simple deposition conditions. The numerical results are well verified by the available experimental data. The vertical velocity of the sediment phase is also shown to be in very good agreement with the fall velocity of the sediment particles, which strongly support the assumption of Rouse’s diffusion theory for suspended sediment under steady state.

Study on the Damage Mechanism of Bridge Pier and Foundation by Turbulent Debris Flow

The debris flow is the uppermost water-destroyed type of highway, which caused large direct economic loss annually in china, especially in mountainous area highway small bridges and culvert damaged seriously. This paper started from the theory of debris flow two-phase flow, it is divide turbulent debris flow into liquid and solid, and with the turbulent debris flow wash against bridge pier increased, the erode depth overpass the burial depth of foundation, base bearing capacity reduced gradually and then result bridge pier instability; in addition for the strong force of impact of debris flow resulted in resistance to capsizing weaken. The damage of bridge and culvert’ foundation mainly duo to the erosion, which lead to the erode depth overpass the burial depth of foundation, furthermore, debris flow force of impact greater then structure resistance and result the structure instability and damaged.