Investigation Of Fluid Flow Research Articles

Flow patterns of oil–water two-phase flow during pressure-driven process in nanoscale fluidic chips

Unconventional oil reservoirs have great potential to become significant sources of petroleum production in the future. Many shale oil systems consist of nanoscale pores and fractures that are significantly smaller than those from conventional reservoirs, and pore sizes are only slightly more than one order of magnitude of those of the saturating fluid molecules. This difference will cause abnormal wettability effect and typical fluid flow mechanisms in unconventional oil systems. Therefore, it is increasingly important to investigate fluid flow behaviours in nanoscale porous media. In this work, a lab-on-chip approach for the direct visualization of the water–oil flow in nanoscale channels was developed by using an advanced laser microscopy system combined with a nanofluidic chip. For the micro-scale study of interface transmission during the drainage and imbibition processes, parallel linear nanofluidic chips were used. A comprehensive study of water–oil flow behaviours is presented. During the drainage process, liquids tend to have a piston-like flow in nanoscale channels; both residual phase saturation and configuration affect the flow behaviour on such small scale; during the imbibition process, a fading-out phenomenon was observed. For a macroscale study of pressure and recovery relationships, unusual entrance pressure was discovered by using network nanofluidic chips comparing to conventional results.

Ghost Particle Velocimetry as an alternative to μPIV for micro/milli-fluidic devices

Ghost Particle Velocimetry (GPV) has only been recently introduced and has already been proven useful in small scale phenomena investigations, such as the study of the flow field during single droplets generation in microfluidic devices. In this work, GPV was used to experimentally investigate fluid flow close to a T-shaped branched junction in a millimetre sized device. The experimental setup allowed for the first time, the study of complex fluid dynamic structures such as vortices and recirculation zones. Several experiments were performed to exploit the capability of GPV in carrying out flow field measurements, at different Reynolds numbers within the laminar flow regime and for two channel sizes. The results were validated by verifying the steady state and stability conditions and by comparing them with results obtained using the well-established micron-scale Particle Image Velocimetry (μPIV). Differences between these two velocimetry techniques were analysed in terms of qualitative and quantitative parameters, to attain a performance comparison and understand the strengths and weaknesses of each respective method.

Fluid-flow measurements in low permeability media with high pressure gradients using neutron imaging: Application to concrete

This article focuses on a new experimental apparatus for investigating fluid flow under high pressure gradients within low-permeability porous media by means of neutron imaging. A titanium Hassler cell which optimises neutron transparency while allowing high pressure confinement (up to 50 MPa) and injection is designed for this purpose and presented here. This contribution focuses on the development of the proposed methodology thanks to some preliminary results obtained using a new neutron imaging facility named NeXT on the D50 beamline at the Institute Laue Langevin (Grenoble). The preliminary test was conducted by injecting normal water into concrete sample prepared and saturated with heavy water to take advantage of the isotope sensitivity of neutrons. The front between these two types of water is tracked in space and time with a combination of neutron radiography and tomography.

Numerical simulation of slab centerline segregation with mechanical reduction during continuous casting process

The mechanical reduction is an effective way to improve the strand center segregation during the continuous casting process, while the effect of reduction parameters on solute transport phenomenon has rarely been addressed. In the present work, a two-phase solidification model coupling the thermal shrinkage and mechanical reduction was established to investigate fluid flow and solute distribution in the continuous casting slab. In the model, an integrated method was used to define solid deformation, which was dependent on the solidification behavior in the center. The results show that the solidified shell contracting outward by thermal shrinkage will be compressed to slab center with mechanical reduction and the enriched liquid steel transporting downwards is suppressed, resulting in the center segregation improvement. The reduction zone should cover the solidification range in the slab center, where the liquid fraction is between 0.95 and 0.01. The mechanical reduction applied in the earlier stage strongly influences the solidification end, while that in the later stage obviously affects center segregation evolution. Moreover, it is found that the solid phase still contracts intensively to slab surface, even the liquid phase has already solidified. Therefore, the mechanical reduction should also be applied in the subsequent cooling stage to avoid the center porosity formation. Besides the reduction amount and position, the slab stretching in the reduction zone is also another important factor influencing the improvement of center segregation.

Gas-Water Two Phase Flow Simulation Based on Pore Network Model for Reservoir Rocks

The relative permeability and capillary pressure are essential to investigate fluid flow in porous media, in terms of studying seepage characteristics of gas -water for CO2 emission reduction through deep saline sequestration. In this paper, we presented gas -water phase flow numerical simulation based on pore network extractions of four rock samples. The influence of temperature, pressure and pore structure on relative permeability and capillary pressure were carefully investigated. Analysis of evaluated results demonstrated that pore structure has significant impact on relative permeability and capillary pressure both for gas/water drainage and imbibition cycles. However, the influence of temperature and pressure on relative permeability and capillary pressure for drainage cycle is neglect-able, while during the imbibition cycle, the gas phase relative permeability is decreasing with increasing pressure and temperature, while capillary pressure and wetting phase relative permeability are decreasing with increasing pressure and increasing with increasing temperature. That might cause by change of rock wetting behavior and interactions between fluid-gas-rock as temperature, pressure change which has more impact on gas flooding process than water flooding. After comparing numerical simulation results of drainage cycle based on Berea sandstone sample to the literature, it is seemed that numerical simulation based on pore network extractions is more efficient and economical method of studying seepage characteristics of gas -water at CO2 reservoir storage conditions.

An optimized transient technique and flow modeling for laboratory permeability measurements of unconventional gas reservoirs with tight structure

Considering the significance of pressure-dependent-permeability in characterizing fluid flow and production from gas reservoirs and the inaccuracy of the conventional transient technique in laboratory permeability measurements of core samples from unconventional reservoirs with tight structure and strong sorption potential, the conventional transient technique is optimized by using two equal-sized gas reservoirs mounted in the up and downstream sides of the experimental setup and creating same magnitude of pressure pulses in each reservoir concurrently. Applicability of the optimized transient technique is examined through both numerical simulation and laboratory tests. A mathematical model is firstly developed to numerically investigate fluid flow behavior in time and space domain. The results from numerical simulation showed that the optimized technique can greatly improve the efficiency and accuracy of the measurement, because a steady flow state as a function of time can be achieved much faster in comparison with the conventional transient technique when the same magnitude of initial pressure difference is established between the two ends of the sample. Given the difference in experimental design and procedures between the conventional and the optimized technique, it is questionable whether currently used analytical solutions developed for the conventional technique for permeability calculation can be applied for the optimized technique. Therefore, an analytical solution, corresponding to the optimized transient technique, has been then theoretically derived. It is finally experimentally verified that accurate permeability results can be obtained based on late-time pressure responses by the derived analytical solution. The optimized experimental method is capable of extending the application of the transient technique into permeability measurements of rocks with tight structure and strong gas sorption potential, providing a more reliable approach for laboratory permeability tests.

Effect of Roughness on Conservative Solute Transport through Synthetic Rough Single Fractures

Understanding solute transport in fractured rocks is of particular importance in many applications. Aperture values ranging from 4.7 to 8.7 mm and Reynolds number (Re) values at 9.38~1743.8 were set for investigating fluid flow through synthetic horizontal single smooth and rough fractures. The Brilliant Blue FCF dye was chosen as the tracer to visualize the transport process. This paper focuses on the dispersion process in rough single fractures under non-Darcian flow conditions. Non-Darcian flow existed in both smooth and rough single fractures and the average flow velocity–hydraulic gradient (V–J) relationships were best described by the Forchheimer equation. The main objectives were to check the existing flow and transport models and to study possible correlations between fitting parameters and heterogeneities. The classical advection dispersion equation (ADE) model failed to capture the long-tailing of breakthrough curves (BTCs). Instead, the continuous time random walk (CTRW) model was better at explaining BTCs in both smooth and rough fractures, especially in capturing the long-tailing feature. The non-Darcian coefficient βc in the Forchheimer equation and the coefficient β in the CTRW model appeared to be most relevant for characterizing the heterogeneity of the rough single fractures.

A numerical investigation on the heat and fluid flow of various nanofluids on a stretching sheet

AbstractFollowing the necessity of investigating fluid flow and heat transfer in the stretching sheet problem and effect of nanofluids on them, performance of various nanofluids were investigated in the present study. Three base fluids (deionized water, ethylene glycol, and engine oil) in combination with 18 nanoparticles (metals and their oxides) were investigated. While experimental methods are preferable, a mathematical model was developed and solved by applying differential quadrature method due to lack of such experimental data. With the results obtained in the real dimensions, the error caused by the cancellation of the viscosity effect due to the dimensionless variables was omitted. Effects of magnetic field and volume fraction of nanoparticle on the fluid flow and heat transfer characteristics were investigated. Highest heat transfer rate as well as small amounts of shear stress was obtained for deionized water–Al and deionized water–Mg nanofluids. Increasing volume fraction of nanoparticle was observed to increase both heat transfer and shear stress rates, while presence of a magnetic field caused an increase in shear stress and decrease in heat transfer rate.

Observations on fluid flow from exposed dentine in primary teeth: An in vitro study

ObjectiveTo investigate fluid flow through dentine in primary teeth in vitro using the replica technique, and to compare the results with those obtained from permanent dentine. DesignThe experiments were carried out on 22 extracted, mandibular, primary, incisor teeth. The incisal edge was removed to 1mm below the dentino-enamel junction and half the exposed surface etched with phosphoric acid. The exposed dentine was blotted dry and the pressure in the pulp cavity held at 0, 15, 30 or 45cm H2O above atmospheric for 30s. Fluid that accumulated on the dentine surface was recorded with impression material and a replica made with epoxy resin which was examined in a scanning electron microscope. ResultsStructures resembling fluid droplets were present in the replicas of unetched dentine in all 22 teeth, and at all the pulpal pressures tested. The droplets formed at 45cm H2O were significantly larger (median diam., 5.14mm; interquartile range, 3.26mm; Friedman repeated measures analysis of variance on ranks (RMAVR) and Tukey test) than those formed at other pressures. There was no evidence of droplets in the replicas of etched dentine with any of the pulpal pressures. ConclusionsThese results demonstrate that fluid will tend to flow from dentine in deciduous teeth when it is exposed. They are similar to those obtained in a previous study in this laboratory on permanent teeth. The fact that fluid droplets were absent from etched dentine suggests that, after being blotted, the etched dentine matrix absorbed fluid that tended to flow out through the dentinal tubules.

Numerical investigation on the effect of sudden contraction on flow behavior in a 90-degree bend

Here we investigate fluid flow in 90-degree bends with and without orifice-like constrictions. The results of flow in non-constricted bends were compared with experimental results for similar Reynolds numbers and found to be in good agreement. Calculations were then carried out for various Reynolds numbers in the laminar and turbulent regimes. In addition, constrictions up to a 60% blockage were incorporated. The present study shows that the Reynolds number and the presence of an orifice-like constriction affects the velocity profile and the pressure distribution. The results indicate that if a sudden contraction is encountered, the peak velocity is larger and the flow is more predisposed to the outer wall than it otherwise would be. In addition, a sudden contraction increases the pressure loss compared to the constant-area bend and it affects the pressure distribution throughout the entire bend. This paper provides a means to predict pressure losses (similar to minor loss coefficients) in rounded bends in the presence or absence of constrictions. Such information is important to practicing engineers for designing fluid-flow conveyance systems. The behavior of the fluid is shown to be connected to the constriction and is also affected by the Reynolds number.

Heterogeneous fluid flow in fractured layered carbonates and its implication for generation of incipient karst

We use numerical models to investigate fluid flow in layered fractured carbonate rocks, and specifically to investigate the effects of the structural and hydraulic properties of both joints and bedding planes on flow localization. Synthetic fracture networks made up of two jointed layers separated by a horizontal bedding plane are generated to represent the typical layered fracture systems often formed in carbonate rocks. A uniform aperture field is assumed for each joint set and for the bedding plane, but different joint sets and the bedding plane can have non-identical values. The aperture ratio of the joint sets to the bedding plane is found to dominate the behaviour of flow heterogeneity on the bedding plane. Three distinct flow regimes, i.e. joint-dominated, transitional and bedding plane-dominated, are recognized. The magnitude of the aperture ratio controls which flow regime develops. We further suggest that the different flow regimes may be responsible for the initiation of different types of incipient karst morphologies observed in nature: pipe karst, stripe karst and sheet karst.

Experimental and Numerical Investigation of a Longfin Inshore Squid’s Flow Characteristics

In the present study, a three-dimensional numerical squid model was generated from a computed tomography images of a longfin inshore squid to investigate fluid flow characteristics around the squid. The three-dimensional squid model obtained from a 3D-printer was utilized in digital particle image velocimetry (DPIV) measurements to acquire velocity contours in the region of interest. Once the three-dimensional numerical squid model was validated with DPIV results, drag force and coefficient, required jet velocity to reach desired swimming velocity for the squid and propulsion efficiencies were calculated for different nozzle diameters. Besides, velocity and pressure contour plots showed the variation of velocity over the squid body and flow separation zone near the head of the squid model, respectively. The study revealed that viscous drag was nearly two times larger than the pressure drag for the squid’s Reynolds numbers of 442500, 949900 and 1510400. It was also found that the propulsion efficiency increases by 20% when the nozzle diameter of a squid was enlarged from 1 cm to 2 cm.

Lattice Boltzmann simulation of 3-dimensional natural convection heat transfer of CuO/water nanofluids

The present study investigated fluid flow and natural convection heat transfer in an enclosure embedded with isothermal cylinder. The purpose was to simulate the three-dimensional natural convection by thermal lattice Boltzmann method based on the D3Q19 model. The effects of suspended nanoparticles on the fluid flow and heat transfer analysis have been investigated for different parameters such as particle volume fraction, particle diameters, and geometry aspect ratio. It is seen that flow behaviors and the average rate of heat transfer in terms of the Nusselt number (Nu) are effectively changed with different controlling parameters such as particle volume fraction (5 % ≤ φ ≤ 10 %), particle diameter (d p = 10 nm to 30 nm) and aspect ratio (0.5 ≤ AR ≤ 2) with fixed Rayleigh number, Ra = 105. The present results give a good approximation for choosing an effective parameter to design a thermal system.

Molecular dynamics simulation of fluid flow and heat transfer in an asymmetric nanochannel

Fluid flow and heat transfer in a nanochannel may depart from the traditional behavior due to the scale effect, and the velocity slip and temperature jump at the fluid-solid interface must be taken into account. A lot of papers about fluid flows in nanochannels with the same wettability at two surfaces have been published. It is necessary to investigate fluid flow and heat transfer in nanochannels with the asymmetric wettability by the molecular dynamics method. The fluid velocity and temperature distributions, interfacial velocity slip and temperature jump in a rough nanochannel are evaluated. The effects of asymmetric wettability on the velocity slip, temperature jump and internal fluid heat transfer are analyzed. The results indicate that the velocity of the fluid flow under an external force in a nanochannel in a bulk region is of a parabolic distribution, but the parabolic distribution is not centrosymmetric because of the centrosymmetric density profile. The difference in density distribution can affect the fluid flow. Viscous dissipation due to shear flow will increase the fluid temperature. The range that is affected by the interaction between solid and liquid is small. So the wettability of the cold wall hardly affects the velocity of the fluid near the hot wall, and the slip velocity is almost constant. At this time, the negative slip will take place at the fluid-solid interface near the hot wall. But the velocity of the fluid near the cold wall comes up with the increasing hydrophobicity of the cold wall, and the slip velocity increases. The temperature jump on both sides of interface increases with the increasing hydrophobicity of the cold wall, but the degree of temperature jump at a liquid-cold solid interface is higher than that at a liquid-hot solid interface. Then the fluid temperature near the cold wall gradually exceeds the fluid temperature near the hot wall. The internal heat flow of the fluid will be reversed. The inverted temperature profile of the fluid will appear. The inverted temperature profile becomes more obvious when the degree of asymmetric wettability increases.

Three-dimensional pore geometry and permeability anisotropy of Berea sandstone under hydrostatic pressure: connecting path and tortuosity data obtained by microfocus X-ray CT

Abstract Void space and permeability are two primary factors controlling the movement and storage of fluids in rock and sediments. To investigate fluid flow anisotropy in Berea sandstone, permeability was measured in three perpendicular directions under effective confining pressure as a function of pore pressure. Permeability anisotropy was observed slightly in the normal and in two parallel directions to the bedding planes. We introduced microfocus X-ray computed tomography (CT) as a non-destructive tool and the three-dimensional medial axis (3DMA) method to quantify the flow-relevant geometric properties of the voids structure. Using this apparatus and structure analysis software, we obtained the distributions of pore size, throat size and the number of connecting paths between two faces in an arbitrary region of Berea sandstone. Using these data, we also evaluated the number of connecting paths between two faces and tortuosity within an arbitrary region, and discussed the relationship between permeability anisotropy and voids geometry.

Selecting an Appropriate Upscaled Reservoir Model Based on Connectivity Analysis

Reservoir engineers aim to build reservoir models to investigate fluid flows within hydrocarbon reservoirs. These models consist of three-dimensional grids populated by petrophysical properties. In this paper, we focus on permeability that is known to significantly influence fluid flow. Reservoir models usually encompass a very large number of fine grid blocks to better represent heterogeneities. However, performing fluid flow simulations for such fine models is extensively CPU-time consuming. A common practice consists in converting the fine models into coarse models with less grid blocks: this is the upscaling process. Many upscaling methods have been proposed in the literature that all lead to distinct coarse models. The problem is how to choose the appropriate upscaling method. Various criteria have been established to evaluate the information loss due to upscaling, but none of them investigate connectivity. In this paper, we propose to first perform a connectivity analysis for the fine and candidate coarse models. This makes it possible to identify shortest paths connecting wells. Then, we introduce two indicators to quantify the length and trajectory mismatch between the paths for the fine and the coarse models. The upscaling technique to be recommended is the one that provides the coarse model for which the shortest paths are the closest to the shortest paths determined for the fine model, both in terms of length and trajectory. Last, the potential of this methodology is investigated from two test cases. We show that the two indicators help select suitable upscaling techniques as long as gravity is not a prominent factor that drives fluid flows.

CFD Simulation of Air Cyclone Separator

A computational fluid dynamics model was developed for air cyclone separator in order to predict the flow pattern inside the cyclone using an Eulerian approach, three dimensions Reynolds-Average Navier-Stokes equations, closed via the Reynolds Stress model as a turbulence model for air flow. The particles were modeled as a discrete phase model using the Lagrangian transport model with turbulent particle dispersion. Computational fluid dynamics modeling was employed to investigate fluid flow patterns and particle trajectories at steady state operating conditions of Stairmand cyclone. Analysis of a computational fluid dynamics simulation accurately revealed that the air flow behavior in cyclone separator consists of two vortexes : an outer vortex with a downwardly directed axial flow and an inner vortex with an upwardly directed flow, this flow profile known as Rankine vortex. A low-pressure zone appeared in the center line of the cyclone due to high swirling velocity. The results showed that the pressure drop increased with increasing the inlet air velocity. The results of the collection efficiency showed that the efficiency increased as the particles diameter increased. A good agreement achieved between the simulation results and published experimental results. The computational fluid dynamics code (ANSYS FLUENT 14.5) with the Reynolds Stress model as the turbulence model, predicted very well the flow field parameters of cyclones and can be used in cyclone design for any dimensions.

Analysis of Macrostep Formation during Top Seeded Solution Growth of 4H-SiC

We used numerical and analytical modeling to investigate fluid flow behaviors close to the growing 4H-SiC crystal surface in the top seeded solution growth process. First, we calculated the azimuthal and radial components of the fluid flow in front of the rotation disc. Second, we developed an analytical model describing the interaction between the step flow (of the vicinal crystal surface) and fluid flow components, considering the crystallography of 4H-SiC and introducing a phase parameter. The correlation of both models allows us to describe qualitatively the conditions for which macrosteps form and destabilize. This phenomenological description is in good agreement with the corresponding experimental observations that are also presented in this paper.

Vascular Endothelial Primary Cilia: Mechanosensation and Hypertension.

Primary cilia are sensory organelles that extend from the cell surface and sense extracellular signals. Endothelial primary cilia protruding from the inner surface of blood vessel walls sense changes in blood flow and convert this mechanosensation into an intracellular biochemical/molecular signal, which triggers a cellular response. Primary endothelial cilia dysfunction may contribute to the impairment of this response and thus be directly implicated in the development of vascular abnormalities such as hypertension and aneurysms. Using both in vitro techniques as well as in vivo animal models, we and others have investigated fluid flow mechanosensory functions of endothelial cilia in cultured cells, animal models and autosomal dominant polycystic kidney disease (ADPKD) patients. More in-depth studies directed at identification of the mechanisms of fluid flow sensing will further enhance our knowledge of cilia-dependent vascular pathology. Although the current treatments aimed at treating the cardiovascular symptoms in ADPKD patients successfully slowed the progression of cyst growth, there is growing evidence which suggests that drugs which interfere with primary cilia function or structure could reduce cardiovascular complications in ADPKD. This review is to summarize the most recent studies on primary endothelial cilia function in the vascular system and to present primary cilia as a novel therapeutic target for vascular hypertension.

Reduction of fine particle emission from a prilling tower using CFD simulation

Fine particle emission occurs in many gas solid operations including prilling towers, where highly concentrated solutions are converted to prills using showerheads followed by solidification and cooling through ambient air. These emissions are generally considered as air pollutants. Reduction of the fine particle emission from an industrial prilling tower for the production of ammonium nitrate (20t/day) is studied. Computational fluid dynamics (CFD) modeling is employed to investigate fluid flow patterns and fluid and particle trajectories at steady state operating conditions. The air flow is modeled using the Eulerian approach, where the turbulence is treated with the Reynolds Averaged Navier–Stokes (RANS) equations. Three design configurations with respect to the air exit were considered and tested using CFD. The concentrated solution was converted to droplets by operating the showerhead in the Rayleigh jet breakup regime. It was found that formation of a quiescent zone around the showerhead was crucial in minimizing secondary disintegration of particles and formation of fine powder. The optimum diameter and location of a spray showerhead ring were obtained. The design of air exit configuration had substantial effect on particle–air interaction and reduction of fine particle carry over.