Fluid Column Research Articles

Parametric studies on smoothed particle hydrodynamic simulations for accurate estimation of open surface flow force

The optimal parameters for the fluid-structure interaction analysis using the Smoothed Particle Hydrodynamics (SPH) for fluids and finite elements for structures, respectively, are explored, and the effectiveness of the simulations with those parameters is validated by solving several open surface fluid problems. For the optimization of the Equation of State (EOS) and the simulation parameters such as the time step, initial particle spacing, and smoothing length factor, a dam-break problem and deflection of an elastic plate is selected, and the least squares analysis is performed on the simulation results. With the optimal values of the pivotal parameters, the accuracy of the simulation is validated by calculating the exerted force on a moving solid column in the open surface fluid. Overall, the SPH-FEM coupled simulation is very effective to calculate the fluid-structure interaction. However, the relevant parameters should be carefully selected to obtain accurate results.

“Wall Viscosity” of Magnetic Fluid Oscillations in a Strong Magnetic Field

The authors provide an estimation of the “wall viscosity” and its increment (“magneto-viscous” effect) in a thin near-wall layer of a column of magnetic fluid oscillating in the tube when a strong transverse magnetic field is applied. The calculation is performed according to the formula obtained on the basis of two different theoretical approaches and applied to the previously published experimental results of the complex measurement of oscillation frequency and saturation magnetization of the magnetic fluid. These results are commented upon, stemming from the assumed absence of the field dependence of viscosity. The estimates of “wall viscosity” “from above” and “from below” are used to calculate their contribution to the damping coefficient of oscillations.

EBOLA VIRUS THREAT: AWARENESS, EDUCATION AND PREPAREDNESS

Background: Ebola virus (EBOV) is a real threat and Ebola virus disease (EVD) can be transferred to any country. International flights in a country enhance the risk of an EBOV outbreak and its spread, especially in thickly populated cities. There is a great need for awareness among common persons, health professionals and decision-makers about EVD and preparedness to manage an outbreak. Objective: The main objective of the study was to describe Ebola virus characteristics, mode of spread, risk factors, signs and symptoms, persistence, and preventions. Methods: PubMed was searched with keywords, and 700 articles were found. Abstracts of all searched articles were reviewed. WHO and CDC websites were explored for relevant information. Results: Contact with EVD patient's body fluids is the strongest risk factor. Although the incubation period of EBOV is from 2 to 21 days, while usually symptoms are developed between 4 and 10 days after exposure of Ebola virus. Similarities of signs and symptoms with other infectious diseases, mostly lead misdiagnosis. EBOV proteins reduce the human immune system's response to viral infections. In EVD survivors, Ebola virus can remain in semen, breast milk, ocular (eye) fluid, and spinal column fluid. It is very difficult to control and manage an outbreak of Ebola virus in areas of high population density areas. Conclusion: Awareness, knowledge, and education about EVD among populations and clinicians can decrease fear, risk, and fatalities. Preparedness and training to HCWs can minimise the risk of EVD especially in thickly populated cities and areas of a country.

Numerical Investigation of Regular and Hybrid Nanofluids Application as the Working Fluids on Thermal Performance of TPCT

Two-phase closed thermosyphon (TPCT) is a cost-effective heat transfer device with high thermal efficiency owing to extensive interphase heat and mass transfer. Thus, TPCT has found many industrial applications. Proper selection of the working fluid could further improve efficiency of TPCT, and nanofluids with superior thermal properties are suitable choices. Numerical simulation of boiling and condensation, natural circulation, and hybrid nanofluid modeling in a closed space is a notable challenge and current study is devoted to this subject. In this study, a novel methodology for incorporating the effects of compressibility and thermal expansion into all thermophysical properties of both phases is developed and programmed into a validated computational fluid dynamics (CFD) code. Distilled water, a regular nanofluid, Al2O3/water, and a hybrid nanofluid, TiSiO4/water are selected as the working fluids. Experimental data for wall thermal profile are employed to validate the numerical simulation. Then, overall thermal resistance is evaluated in terms of nanoparticles concentration and input power variations. Results indicate that the numerical methodology developed in this study could evaluate the optimum state of TPCT in an efficient and accurate manner and the optimum state for regular and hybrid nanofluid demonstrates 48% and 54% improvement over distilled water, respectively. Furthermore, a subtle relation between the thermal resistance and the height to which fluid column rises in TPCT has been discerned and quantified, which is used as a supplement to the conventional qualitative method of reasoning to justify the somewhat controversial behaviors of nanofluid application in TPCT.

Viscosity of Magnetic Fluid in Oscillation System in a Strong Magnetic Field

The article gives an assessment of viscosity and its increment (‘magnetoviscous’ effect) in a thin near-wall layer of the column of magnetic fluid that oscillates in the tube when applying a strong transverse magnetic field. Viscosity is calculated according to a formula derived from two different theoretical approaches. For calculation, previously published experimental results, which were discussed earlier on the assumption that there is no field dependence of viscosity, are used in the article. A comparative analysis of the “near-wall viscosity” estimates obtained using dynamic elasticity as well as the magnetization curve and the coefficient of static elasticity is carried out. The significance of the results obtained for ‘magnetoviscous’ effect for performing diagnosis of interparticle aggregation is indicated.

Charney’s Model—the Renowned Prototype of Baroclinic Instability—Is Barotropically Unstable As Well

The Charney model is reexamined using a new mathematical tool, the multiscale window transform (MWT), and the MWT-based localized multiscale energetics analysis developed by Liang and Robinson to deal with realistic geophysical fluid flow processes. Traditionally, though this model has been taken as a prototype of baroclinic instability, it actually undergoes a mixed one. While baroclinic instability explains the bottom-trapped feature of the perturbation, the second extreme center in the perturbation field can only be explained by a new barotropic instability when the Charney–Green number γ ≪ 1, which takes place throughout the fluid column, and is maximized at a height where its baroclinic counterpart stops functioning. The giving way of the baroclinic instability to a barotropic one at this height corresponds well to the rectification of the tilting found on the maps of perturbation velocity and pressure. Also established in this study is the relative importance of barotropic instability to baroclinic instability in terms of γ. When γ ≫ 1, barotropic instability is negligible and hence the system can be viewed as purely baroclinic; when γ ≪ 1, however, barotropic and baroclinic instabilities are of the same order; in fact, barotropic instability can be even stronger. The implication of these results has been discussed in linking them to real atmospheric processes.

X-ray densitometry of drilling fluids at the rig standpipe

Fluids used during well construction operations serve as a primary barrier for well control, with the fluid density generating sufficient hydrostatic pressure in the fluid column to control downhole formation fluids and gas. Real-time density measurement at the well inlet, where high pressures of many thousands of psi can occur, is highly desirable in order to maintain well control. This improved characterization of the well bore pressure profile allows one to drill wells with narrow drilling margins without non-productive time from well control events, resulting in safer and more cost-effective well construction operations. Gamma ray densitometers are suitable measuring devices for high-pressure density measurement. Typical flow conditions encountered at the inlet, such as a fully filled pipe and a homogeneously mixed mud, are very conducive to their use. In-spite of their high measurement accuracy and relatively fast response times, however, these meters have seen limited adoption in field. This is primarily because the meters come with safety concerns due to the radioactive source required for gamma ray generation. Additionally, the source has to be tracked throughout its life and properly handled during storage, transportation, installation and disposal. Given these concerns and challenges, a majority of oil and gas operating and service companies use manual density measurements at the mud pits using a pressurized mud balance. To help change this rather antiquated and infrequent practice that relies on manual labor, this paper evaluates the feasibility of using a non-radioactive, X-ray based densitometer as an alternative to the gamma ray meter. X-ray densitometry works on the same proven principles as gamma ray densitometry, without the latter's drawbacks. Two X-ray methods, an empirical method and a model-based method (inspired by a technique used in the medical field known as single X-ray absorptiometry) are presented here. Real-time density measurements on the high pressure line with an accuracy of 99% or better and a measurement frequency of 1 Hz are feasible using these methods.

Mercury vs. Water: An Analysis of Multi-Institutional Survey Data Assessing Intracranial Pressure Unit of Measure Awareness

Intracranial pressure (ICP) reporting impacts neurosurgical care. Millimeters of mercury (mmHg) and centimeters of water (cmH2O) are both used to report ICP in clinical practice and the literature. In this study, we investigated ICP unit of measure awareness in the neurosurgical community. A survey was conducted at four US academic neurosurgery departments asking the following questions: What is your threshold for a concerning ICP? How many minutes is that ICP sustained for you to be concerned? What unit are you implying when you state that ICP? What unit of measure is an ICP reported on the monitor when transduced? When setting an external ventricular drain Becker bag level, what unit of measure do you set it to? Do you ever manually check an ICP based on a column of cerebrospinal fluid? How many cmH2O is 20mmHg? An ICP of 20 and sustained for five minutes were the two most common answers. Some 71% of residents and 34% of attendings reported using cmH2O as the unit of measure; 18% of residents and 24% of attendings implied different units when discussing ICP than the unit they thought was transduced; and 53% of residents and 34% of attendings did not know the transduced ICP unit of measure reported in their intensive care unit. Variability and discrepancies regarding the ICP unit of measure exist in academic neurosurgery departments. Clinicians should familiarize themselves with their hospital's practices. Institutions and all of medicine may consider standardizing the ICP unit of measure, using mmHg as a universal nomenclature.

Emptying of a bottle: How a robust pressure-driven oscillator coexists with complex two-phase flow dynamics

The emptying of a bottle is one of the most common two-phase flows encountered in everyday’s life fluid mechanics. We report on a detailed experimental analysis of this flow configuration covering a wide range of neck-to-bottle diameter ratios, d*, and initial filling ratios, F. The joint use of a pressure sensor at the top of the bottle and a shadowgraph technique to track the evolution of the upper liquid surface allows the average gas volume fraction in the fluid column to be computed throughout the discharge. Variations of the bottle emptying time, gas content, and characteristics of the pressure signal as a function of d* and/or F are analyzed, and scaling or evolution laws are derived. A specific focus is put on the initial transient stages following the neck opening, especially on the nature and growth of the first bubble that reaches the upper free surface. Over a wide range of d*, this bubble takes the form of a large spherical cap or Taylor bubble, the rise speed of which is controlled by the bottle diameter. Such a bubble directly emerges from the neck for large enough d*, but rather results from successive coalescence of smaller bubbles for small d*. Whatever d*, the volume of this leading bubble increases over time, since a fraction of the small bubbles swarm trailed in its wake merges with its back face. This coalescence-induced growth is quantified through a simple model.

Strength of sandy and clayey soils cemented with single and double fluid jet grouting

Innovations in jet grouting technology have primarily focused on the cutting efficiency of the jets, with the aim of creating larger columns and increasing the productivity of construction sites. Relatively little attention has been paid to the consequences of the grouting system on the mechanical properties of the formed material. This paper investigates this aspect by analysing the results of two field trials carried out in both sandy and clayey soils, where single and double fluid jet grouting were simultaneously performed, with varied grout composition and injection parameters. Parallel uniaxial compressive tests on samples cored from the columns show that the material formed with the double system is systematically lower in strength than the material formed using the single fluid system. The mineralogical composition of samples cored from the columns was analysed by performing parallel Scanning Electron Microscopy (SEM), X-ray diffraction analysis (XRD), Differential Thermal Analysis (DTA) and Thermo-Gravimetric Analyses (TGA) to determine the reasons for this difference. A lower proportion of cementitious products, an accelerated carbonation of portlandite and a less homogeneous distribution of cement hydration products was found on the surface of the soil particles of the double samples than for the single fluid columns.

Elemental and isotopic fractionation of noble gases in gas and oil under reservoir conditions: Impact of thermodiffusion⋆.

Noble gases, and the way they fractionate, is a promising approach to better constrain origin, migration and initial state distributions of fluids in gas and oil reservoirs. Thermodiffusion, is one of the phenomena that may lead to isotope and elemental fractionation of noble gases. However, this effect, assumed to be small, has not been quantified, nor measured, in oil and gas under reservoir conditions. Thus, in this work, molecular dynamics simulations have been performed to compute the thermal diffusion factors of noble gases, in a dense gas (methane) and in an oil (n-hexane) under high pressures. Interestingly, it has been found that thermal diffusion factors, associated to both isotopic (36Ar, 40Ar) and elemental fractionations of noble gases (4He, 20Ne, 40Ar, 84Kr and 131Xe) in gas and oil, could be expressed as linear functions of the reduced masses. Regarding the amplitude of the phenomena, it has been found that, in a stationary 1D oil or gas fluid column, thermodiffusion due to a typical geothermal gradient has an impact on noble gas isotopic and elemental fractionation which is of the same order of magnitude than gravity segregation, but opposite in sign. In addition, the relative impact of thermodiffusion on isotopic and elemental fractionations depends on the fluid type which is another interesting feature. Thus, these first numerical results on isotopic and elemental fractionation of noble gases by thermodiffusion in simple pure gas and oil emphasize their interest as natural tracers that could be used to improve the pre-exploitation description of oil and gas reservoirs.

Simulation of viscoelastic two-phase flows with insoluble surfactants

A stabilized finite element scheme is developed for computations of buoyancy driven 3D-axisymmetric viscoelastic two-phase flows with insoluble surfactants. The numerical scheme solves the Navier–Stokes equations for the fluid flow, Giesekus constitutive equation for the effects of viscoelasticity and simultaneously an evolution equation for the surfactant concentration on the interface. The interface is tracked by the coupled arbitrary Lagrangian–Eulerian (ALE) and Lagrangian approach. The interface-resolved moving meshes allow accurate incorporation of the interfacial tension force, Marangoni forces and the jumps in the material properties. Further, the tangential gradient operator technique is used to handle the curvature approximation in a semi-implicit manner. An one-level Local Projection Stabilization (LPS), which is based on an enriched approximation space and a discontinuous projection space, where both spaces are defined on a same mesh is used to stabilize the model equations. The stabilized numerical scheme allows us to use isoparametric second order conforming finite elements enriched with cubic bubble functions for velocity and viscoelastic stress, second order finite elements for surfactant concentration and discontinuous first order finite element for pressure. A number of computations are performed for a Newtonian drop rising in a viscoelastic fluid column and a viscoelastic drop rising in a Newtonian fluid column with insoluble surfactants on the interface. The influence of the Marangoni number, initial surfactant concentration and Peclet number on the dynamics of the rising drop are analyzed. The numerical study shows that a viscoelastic drop rising in a Newtonian fluid column develops an indentation around the rear stagnation point with a dimpled shape without insoluble surfactants. The presence of insoluble surfactants forces the drop to rise slowly but the drop at the tail end is pulled up more. However, a Newtonian drop rising in a viscoelastic fluid column experiences an extended trailing edge with a cusp-like shape without insoluble surfactants. The presence of surfactants pulls the tail end of the drop up slightly and makes the tail flatter with/without small undulations depending on the magnitude of the surfactant concentrations.

Predicting the Dynamic Parameters of Multiphase Flow in CFD (Dam-Break Simulation) Using Artificial Intelligence-(Cascading Deployment)

Multiphase flow of oil, gas, and water occurs in a reservoir’s underground formation and also within the associated downstream pipeline and structures. Computer simulations of such phenomena are essential in order to achieve the behavior of parameters including but not limited to evolution of phase fractions, temperature, velocity, pressure, and flow regimes. However, within the oil and gas industry, due to the highly complex nature of such phenomena seen in unconventional assets, an accurate and fast calculation of the aforementioned parameters has not been successful using numerical simulation techniques, i.e., computational fluid dynamic (CFD). In this study, a fast-track data-driven method based on artificial intelligence (AI) is designed, applied, and investigated in one of the most well-known multiphase flow problems. This problem is a two-dimensional dam-break that consists of a rectangular tank with the fluid column at the left side of the tank behind the gate. Initially, the gate is opened, which leads to the collapse of the column of fluid and generates a complex flow structure, including water and captured bubbles. The necessary data were obtained from the experience and partially used in our fast-track data-driven model. We built our models using Levenberg Marquardt algorithm in a feed-forward back propagation technique. We combined our model with stochastic optimization in a way that it decreased the absolute error accumulated in following time-steps compared to numerical computation. First, we observed that our models predicted the dynamic behavior of multiphase flow at each time-step with higher speed, and hence lowered the run time when compared to the CFD numerical simulation. To be exact, the computations of our models were more than one hundred times faster than the CFD model, an order of 8 h to minutes using our models. Second, the accuracy of our predictions was within the limit of 10% in cascading condition compared to the numerical simulation. This was acceptable considering its application in underground formations with highly complex fluid flow phenomena. Our models help all engineering aspects of the oil and gas industry from drilling and well design to the future prediction of an efficient production.

Determining fracture properties from acoustic borehole waves: theory and experimental results

A borehole in the subsurface may penetrate rocks which are porous, permeable and fractured. Pressure transients in the borehole will therefore cause viscous fluid to flow into and out of the wall of the borehole. This forced flow consumes some energy and affects the phase velocity and amplitude of the waves traveling in the borehole fluid column. These effects can be evaluated to extract information about the rocks adjacent to the borehole, which is of paramount importance for the oil and gas industry. This work discusses laboratory wave experiments in a 7.5 m long vertical shock tube. Rock samples having a vertical borehole and horizontal fractures are installed in the shock tube and filled with water. The shock tube generates broadband pressure transients in the borehole. These are measured in the borehole at variable depth by means of a sliding pressure probe. Repetitive experiments are combined into borehole microseismograms. In this way borehole wave reflection and transmission coefficients over the fractures are determined. The results show good agreement with low-frequency theory, where it is assumed that the wavelengths are much larger than the tube diameter. Inversely, it is shown that the aperture and the length of the fracture can directly be inferred from acoustic borehole experiments.

Brecciation driven by changes in fluid column heights

AbstractA mechanism is presented for the pulses of high fluid pressure (PF) necessary for fluid‐assisted brecciation. Establishment of hydraulic‐ or pneumatic‐connectivity between rock masses with different PF can cause overpressure in the higher rocks because the PF gradient is parallel to the hydrostatic gradient (the centroid effect). PF can become high enough to create a fracture network, with an influx of fluids and mineralisation occurring as fluids migrate to areas of lower PF. Changes in PF caused by the centroid effect can cause other structures and seismicity.

Valve nozzle shape effect on gas lift system performance

Experiments were carried out using conical, bevelled entrance, bullet and orifice gas lift valve nozzle shapes with port diameter of 5 to 12 mm to study the effect of gas lift valve nozzle shape on the continuous flow gas lift system efficiency. A nitrogen-glycerin with nitrogen injection rate of 0.033 to 0.167 L/s flow through 50 mm diameter transparent vertical pipe and 3 m height to simulate a continuous flow gas lift system. Taylor bubble length and liquid produced mass were measured. The flow pattern was observed and the image was recorded using digital single-lens reflex camera. It was found that only slug flow occurred and gradual conical nozzle shape enlargement reduced the energy loss within the valve. The overall results show that conical nozzle produced the highest efficiency due to the less energy losses within the valve nozzle and most stable gas flow achieved in the fluid column pipe. [Received: December 24, 2015; Accepted: June 6, 2017]

An Approach for Passive Removal of Residual LNAPL from Groundwater

AbstractLight nonaqueous phase liquids (LNAPLs) are a problematic challenge for obtaining site closure or no further action remediation sites. The source of the LNAPLs varies from leaking underground petroleum storage tanks, to manufacturing facilities where oil leaks create LNAPL accumulations beneath factory floors. Active recovery using pumping or periodic vacuum recovery from wells or sumps is used for remediation, but usually has disappointing results when LNAPL reaccumulates to thicknesses exceeding the 0.01‐foot action level recognized by many states. This paper presents a simple passive approach for recovering persistent LNAPL using nonwoven hydrophobic oil absorbing cloth. The method used laboratory trials to assess physical properties of the cloth. Parameters observed and assessed included sorptive capacity and rate, buoyancy, and LNAPL wicking. It was determined that the cloth could be rolled and secured with cable ties for placement in the wells/sumps. Two placement designs were developed, one where rolled sorbent freely floated on the well/sump fluid surface and a second where the sorbent roll was placed in the fluid column at a fixed depth. Sorbents were then used at two manufacturing facilities where LNAPLs persisted for decades. In both instances, many wells/sumps were reduced to thicknesses below the action level in less than 2 months. In most wells, LNAPL did not reaccumulate. Where it did reaccumulate, it was less than 50% of the original thickness. Using laboratory‐derived recovery rates, cloth sorbents could be sized to minimize placement/recovery frequency while effectively recovering LNAPL.

Convection of a heat-generating fluid in a rotating cylindrical cavity subject to transverse vibrations

abstract The goal of this research is to study experimentally and theoretically the influence of transversal vibrations on the average convection of a non-isothermal fluid in a rotating cavity when the rotational frequency and vibration frequency approach each other. The research involves experimental studies of the convection of a heat-generating fluid in a rotating horizontal cylinder with isothermal boundaries subject to translational vibrations, perpendicular to the rotation axis. In the absence of vibrations, at fast cavity rotation the fluid is in an equilibrium state in the centrifugal force field with the temperature maximum at the cavity axis. The excitation of average convection and increase of heat transport is discovered when the vibration frequency is near to the rotation frequency. At some discrepancy between the frequencies, the resonance excitation of azimuthal two-dimensional inertial oscillations of the non-isothermal fluid column takes place. This results in significant decrease of the temperature at the cavity axis. When the frequencies coincide, the vibrations break the axial symmetry of the centrifugal force field. The resulting force field is stationary in the cavity frame and results in an intensive thermal convection; the theoretical analysis of this phenomenon is presented. The dependence of heat transport on the parameters of vibrations is determined both in the case of resonance liquid oscillations and in the case of equal frequencies. The vibrational and the centrifugal mechanisms play the key role in the convection. The transverse vibrations are demonstrated to be an efficient tool for the control of thermal convection in rotating systems.

Diffusion under micro‐gravity: Mass transfer from rising bubble in a stagnant fluid column

AbstractNumerical simulation of two‐phase flows using Volume of Fluid (VOF) method is known be to susceptible to parasitic currents, which arises due to erroneous interface curvature calculation to model the surface tension force. The interface curvature calculation scheme in OpenFoam has been modified according to the Sharp Surface Force (SSF) which reduced parasitic currents magnitude significantly. Alongside SSF method the Continuous Species Transfer (CST) equation is implemented in OpenFOAM 4.1 to simulate mass transfer from an Oxygen bubble to the surrounding stagnant water‐glycerol solution under micro‐gravity environment.

Numerical simulation of micro droplet formation combined with pneumatic and piezoelectric drive

3D printing has been widely used for rapid prototyping and rapid manufacturing. Achieving higher resolution is one of the main directions in the development of 3D printing technology. Inkjet printing has achieved micron level resolution with micro droplets produced by piezoelectric drive, and inkjet printing is considered to be a key technology in the field of 3D printing. The materials used in inkjet printing and 3D printing have different properties. The fluids or slurries used in 3D printing have higher viscosity than the ink. With the increase of the viscosity of materials, the diameter of droplets is increased and the resolution is decreased. In order to improve the printing performance of materials with high viscosity, a hybrid drive method based on piezoelectric drive and pneumatic drive is proposed. When fluid column with high viscosity is formed by pneumatic drive, the piezoelectric drive is combined to control the movement of monolithic structure. The breakage of the fluid column is accelerated by the vibration of print head and a smaller droplet is formed. The structure of print head with hybrid drive is designed, and a numerical analysis model is established to investigate the feasibility of micro droplets formation for fluids with different viscosity. The simulation results show that droplets with diameter smaller than the nozzle can be formed by the hybrid drive. With the increase of the viscosity, the advantages of hybrid drive are more significant than the single drive mode. The minimum diameter of the droplet is 47 μm when the viscosity is 1000 mPa·s, which is 55% of the single drive mode and 94% of the diameter of nozzle. The simulation results verified the feasibility of micro droplets formation for fluids with high viscosity by hybrid drive.