Two-dimensional Physical Model Research Articles

Towards the understanding of convective dissolution in confined porous media: thin bead pack experiments, two-dimensional direct numerical simulations and physical models

We consider the process of convective dissolution in a homogeneous and isotropic porous medium. The flow is unstable due to the presence of a solute that induces a density difference responsible for driving the flow. The mixing dynamics is thus driven by a Rayleigh–Taylor instability at the pore scale. We investigate the flow at the scale of the pores using Hele-Shaw type experiment with bead packs, two-dimensional direct numerical simulations and physical models. Experiments and simulations have been specifically designed to mimic the same flow conditions, namely matching porosities, high Schmidt numbers and linear dependency of fluid density with solute concentration. In addition, the solid obstacles of the medium are impermeable to fluid and solute. We characterise the evolution of the flow via the mixing length, which quantifies the extension of the mixing region and grows linearly in time. The flow structure, analysed via the centreline mean wavelength, is observed to grow in agreement with theoretical predictions. Finally, we analyse the dissolution dynamics of the system, quantified through the mean scalar dissipation, and three mixing regimes are observed. Initially, the evolution is controlled by diffusion, which produces solute mixing across the initial horizontal interface. Then, when the interfacial diffusive layer is sufficiently thick, it becomes unstable, forming finger-like structures and driving the system into a convection-dominated phase. Finally, when the fingers have grown sufficiently to touch the horizontal boundaries of the domain, the mixing reduces dramatically due to the absence of fresh unmixed fluid. With the aid of simple physical models, we explain the physics of the results obtained numerically and experimentally. The solute evolution presents a self-similar behaviour, and it is controlled by different length scales in each stage of the mixing process, namely the length scale of diffusion, the pore size and the domain height.

Simulation Study on the Prediction of Macroscale Young’s Modulus Based on the Mesoscale Characteristics of Tight Glutenite Reservoirs

To obtain the macroscale Young’s modulus of glutenite under gravel inclusions, a numerical simulation of macroscale Young’s modulus prediction based on the mesoscale characteristics of glutenite was carried out. Firstly, the micron indentation test was used to obtain the meso-mechanical parameters of gravel and matrix in glutenite to ensure the reasonableness of the numerical simulation parameter settings; secondly, a two-dimensional glutenite physical model generation method based on the secondary development of Python was put forward; and then, the macroscale Young’s modulus variation rule of glutenite under different gravel sizes, particle size ratios, and content characteristics were analyzed using the finite element method (FEM). The results show that Young’s modulus of gravel is larger than Young’s modulus of the matrix, and Young’s modulus of different gravel and matrix has some differences. The gravel content is the main controlling factor affecting the macroscale Young’s modulus of glutenite; the gravel content and Young’s modulus of glutenite show a strong positive correlation, and the gravel size and particle size ratio have less influence on the macroscale Young’s modulus of glutenite. The difference in Young’s modulus between gravel and matrix causes the formation of local stress concentrations during loading and compression of glutenite. The smaller the gravel grain size, the higher the degree of non-uniformity of the grain size, the more likely it is to form higher local stresses. The results of the study provide a new prediction method for the prediction of the macroscale Young’s modulus of a glutenite reservoir.

Numerical Technique for a Darcy-Forchheimer Casson CuO-MgO/Methanol Hybrid Nanofluid Flow due to an Elongated Curved Surface with Chemical Reaction

The insight of the present work is for analyzing the Darcy-Forchheimer model on energy and mass transfer fluid flow with the impact of CuO and MgO metallic nanoparticles with methanol as base fluid due to an elongated curved surface in uniform porous media numerically. For the two-dimensional physical model, the governing nonlinear coupled partial differential equations are derived with suitable boundary conditions and in turn, using appropriate similarity transformation transferred to nonlinear coupled ordinary differential equations. Runge-Kutta Felhberg (RKF) computational results are carried out using Maple software to understand the characteristics variations of momentum fluid flow, heat and mass transfer on various control non-dimensional parameters of the model viz local Reynolds number, Schmidt number, porosity and curvature parameters. The findings are shown numerically and graphically to demonstrate the performance of flow-related physical parameters on energy, velocity, and concentration patterns. Furthermore, the Nusselt number, skin friction coefficient and Sherwood number for the currently stated system are numerically computed. The Prandtl number denotes the deterioration of the temperature profile's performance. It is believed that increasing the Casson parameter value lowers the velocity field. Moreover, the concentration field declines as the Schmidt number grows. The findings are compared to previous studies which turn out to be in good accord.

Performance evaluation and optimization of hollow fiber membrane contactors for carbon dioxide absorption: A comparative study of ammonia, ethanolamine, and diethanolamine solvents

Membrane absorption is an emerging technology that amalgamates the merits of chemical absorption and membrane separation. However, the pivotal choice of solvent profoundly influences the overall performance of the membrane contactor. In this paper, a robust two-dimensional (2D) steady-state non-wetting mathematical and physical model of a hollow fiber membrane contactor (HFMC) was established. COMSOL software was used to solve the model equation of the membrane contactor. The impacts of ammonia, ethanolamine (MEA) and diethanolamine (DEA) on carbon dioxide absorption under different operating conditions and membrane geometry properties were simulated and compared. Results showed that the utilization of NH3 as the solvent in HFMC showcases performance akin to that of MEA, a substantial advantage over DEA. Notably, the performance disparity between ammonia and MEA might alter significantly in response to varying operating parameters. For instance, the CO2 removal performance of HFMC using aqueous ammonia surpasses that of MEA when the CO2 volume fraction exceeds 19 %. Moreover, hollow fibers featuring larger inner diameters and lengths endow a heightened effective mass-transfer area, thereby facilitating superior carbon dioxide removal performance.

Multi-method joint monitoring study on strata behavior in shallow seam mining under bedrock gully

The Baijigou Coal Mine in Helan mountain mining area is alpine gully landform, and the double key stratums are cut by the gully. A two-dimensional physical similarity model under this condition was established in the laboratory. The strain field, deformation field and pressure field of the model are jointly and accurately monitored by BOTDA, DIC and pressure sensors. The rock behavior in shallow coal seam mining under bedrock gullies are studied. In the mining stage under the gully, the deformation of overburden is intense because overburden is thin, and the surface is easy to form a depression basin. In the mining stage far away from the gully, the deformed rock mass lacks horizontal support in the process of deflecting to the lower goaf, and the movement rock is in a multilateral block. The multilateral block rock periodically deflects and rotates, resulting in the periodic deformation and break of the inferior key stratum. At the mining stage of away from the gully, nine times of roof weighting occurred. And there are large and small periodic weighting phenomenon with the average roof pressure concentration coefficient is 1.37. The distance between the peak point of advance abutment pressure and the coal wall is 6–18 cm, and the influence distance decreases with the advancing of the working face. The inferior key stratum has a significant impact on the weighting process and the weighting strength. In the mining stage under the mountaintop, large downward inclined tension crack is prone to produce in the slope on the side of the stope line, and the roof weighting is the most severe. In the mining stage close to the gully, the overburden falls in layers from bottom to top, and the overburden at the slope toe is prone to slip. At the mining stage under the mountaintop and close to the gully, five times of roof weighting occurred. And the roof weighting concentration coefficient is 1.46 on average. The distance between the peak point of advance abutment pressure and the coal wall is always kept at 6–16 cm, and the influence distance is 33–41 cm. The study can provide a reference for mining design and ensures safe and efficient mining in this condition.

Performance analysis of ice storage tank with smooth-tube and corrugated-tube heat exchangers based on numerical simulation

The ice storage system is of great value to improve the flexibility of building cooling load. In this paper, the two-dimensional physical models of smooth-tube and corrugated-tube heat exchangers ice-storage tank is established with consideration of natural convection. The ice storage process of tubes is numerically simulated using Computational Fluid Dynamics (CFD). The effects of structural parameters on the ice storage performance are comprehensively analyzed, including the pitch and height of corrugation. The results indicate that the ice storage duration of the corrugated-tube heat exchanger is shortened by 7.1% compared with that of the traditional smooth-tube heat exchanger, which is due to the fact that corrugations disrupt the development of the boundary layer and strengthen the fluid mixing. There is the thicker ice layer outside the corrugated tube in comparison with the smooth tube at the same time. In addition, the influence of the corrugated tube structure on its ice storage performance is studied by varying the corrugation pitch and height. If the corrugation pitch is decreased by 41.7% and the corrugation height is increased by 28%, the heat transfer performance of corrugated tubes is improved by 10.3% and 29.4%, respectively.

Switching the Moiré Lattice Models in the Twisted Bilayer WSe2 by Strain or Pressure.

Moiré superlattices of twisted van der Waals heterostructures provide a promising and tunable platform for simulating correlated two-dimensional physical models. In twisted bilayer transition-metal dichalcogenides with twist angles close to 0°, the Γ and K valley moiré bands are described by the honeycomb and the triangular effective lattice models, respectively, with distinct physics. Using large-scale first-principles calculations, we show that in-plane biaxial strain and out-of-plane pressure provide effective knobs for switching the moiré lattice models that emerged at the band edges in twisted bilayer WSe2 by shifting the energy positions of the Γ and K valley minibands. The shifting mechanism originates from the differences in the orbital characters of the Γ and K valley states and their responses to strain and pressure. The critical strain and pressure for switching the Γ/K valleys are 2.11% and 2.175 GPa, respectively.

Probing the temperature structure of the inner region of a protoplanetary disk

Context. Disk temperature structure is crucial for the formation of planets. Midplane heating induced by disk accretion plays a key role in determining the disk temperature, particularly at the inner disk midplane where planets are formed. However, the efficiency of accretion heating has been not well constrained by observations. Aims. Our aim is to observationally constrain the physical properties of the inner region of the CW Tau disk, where the midplane heating potentially takes place. Methods. We constructed two-dimensional physical models of the CW Tau disk that take the midplane heating into account. We compared the models with the ALMA dust continuum observations at Bands 4, 6, 7, and 8, with an angular resolution of 0″. 1. The observed brightness temperatures are almost wavelength-independent at ≲10 au. Results. We find that if the maximum dust size is amax ≲100 µm, the brightness temperatures predicted by the model exceed the observed values, regardless of the efficiency of accretion heating. The low observed brightness temperatures can be explained if millimeter scattering reduces the intensity. If the disk is passive, amax needs to be either ~150 µm or more than a few cm. The accretion heating significantly increases the brightness temperature, particularly when amax ≲ 300 µm; thus, the value of amax must be either ~300 µm or over a few cm. The midplane temperature is expected to be ~1.5–3 times higher than the observed brightness temperatures, depending on the models. The dust settling effectively increases the temperature of the dust responsible for the millimeter emission in the active disk, which leads to the model with 300 µm-sized dust overpredicting the brightness temperatures when strong turbulence is absent. Porous dust (porosity of 0.9) makes the accretion heating more efficient, so that some sort of reduction in accretion heating is required. Conclusions. The brightness temperature is not a simple function of the dust temperature because of the effect of scattering and midplane heating – even when the disk is optically thick. The current data of the CW Tau disk are not sufficient to allow us to discriminate between the passive and active disk models. Future observations at longer wavelengths and higher angular resolution will help to constrain the heating mechanisms of the inner regions of protoplanetary disks.

Physical Model Tests for Mean Wave Overtopping Discharge of Rubble-mound Structure Covered by Tetrapods: <i>R<sub>C</sub>/A<sub>C</sub></i> = 1 and cot<i>a</i> = 1.5 Conditions

The allowable mean overtopping discharge is used as a design parameter for coastal structures. The crest elevation of coastal structures should ensure the wave overtopping discharge within acceptable limits for structural safety and the safety of pedestrians, vehicles, operations, and so on. In this study, two-dimensional physical model tests on typical rubble-mound structure geometries were performed and the the mean wave overtopping discharges under various water depth and wave conditions were measrued. The various test conditions were applied to the tests with the change of the wave steepness, relative freeboard and relative wave height. An empirical formula from the experimental data was proposed to predict the mean wave overtopping volumes.

DETERMINATION OF WAVE RUN-UP THROUGH THE TIMESTACK METHODOLOGY AND THROUGH A RESISTIVE WAVE GAUGE. A COMPARATIVE ANALYSIS

The objective of this work is the comparison of two methodologies used for run-up measurements in a two-dimensional physical model, which represented the protection breakwaters of the Peniche and Ericeira’s ports. Tests were carried out in the scope of the BSafe4sea project. The methodologies used were: a) the traditional measurement of the run-up height with a resistive wave gauge; b) the use of video cameras and image processing techniques images to infer the run-up heights, having its performance evaluated for some of the test conditions. Regarding the results obtained, in terms of Ru2% and Rumax, it was found that the magnitude of the values obtained with the two techniques were quite similar, although the video analysis returned slightly higher values than the wave gauge. Thus, it was found that the video image technique is a viable alternative to measure the run-up. It is recommended the use of diffused light during the tests, along with stabilizing the video camera, to improve the accuracy of the results obtained by the video-based technique. Besides, the quality of the video image and the use different colors of the armour units of the phicial model, could contribute to achieve better results with the TimeStack methodology.

Revolutionising Precision and Efficiency of Dental Implant Placement through Digital Planning Software: A Narrative Review

Advancements have transformed dentistry, and digital planning software has emerged as a revolutionary tool in implantology. The present review explores the capabilities, benefits, and limitations of digital planning software in implantology, emphasising its impact on clinical practice and patient outcomes. Traditional implant planning relied on Two-dimensional (2D) radiographs and physical study models, limiting accuracy and predictability. Digital planning software utilises advanced imaging technologies to generate precise Threedimensional (3D) models of the patient’s dentition, enabling comprehensive treatment planning. Key features include 3D visualisation, virtual implant placement, prosthetic-driven planning, and simulations. These features enhance accuracy, enable collaborative decisionmaking, and streamline the treatment process. Commercially available digital planning software options offer similar advantages but also have unique features. Studies support the clinical efficacy of digital planning in implant placement, showing improved accuracy, patient satisfaction, and reduced complications. However, more randomised controlled trials are needed to evaluate the clinical outcomes of digitally guided implant placement. Considerations include the need for high-quality input data, a learning curve for software proficiency, and cost considerations. Nevertheless, digital planning software has become an indispensable tool in implantology, enhancing treatment outcomes and patient satisfaction. The future of digital planning software in implantology lies in Artificial Intelligence (AI) integration, automation, and personalised recommendations. With ongoing advancements, digital planning software will continue to revolutionise implantology, optimising treatment planning and execution for improved patient care.

Simulation of pore space production law and capacity expansion mechanism of underground gas storage

One-dimensional gas injection storage building and one-cycle injection-production modeling experiment, and two-dimensional flat core storage building and multi-cycle injection-production modeling experiment were carried out using one-dimensional long core and large two-dimensional flat physical models to find out the effects of reservoir physical properties and injection-production balance time on reservoir pore utilization efficiency, effective reservoir capacity formation and capacity-reaching cycle. The results show that reservoir physical properties and formation water saturation are the main factors affecting the construction and operation of gas-reservoir type underground gas storage. During the construction and operation of gas-reservoir type gas storage, the reservoir space can be divided into three types of working zones: high efficiency, low efficiency and ineffective ones. The higher the reservoir permeability, the higher the pore utilization efficiency is, the smaller the ineffective working zone is, or there is no ineffective working zone; the smaller the loss of injected gas is, and the higher the utilization rate of pores is. The better the reservoir physical properties, the larger the reservoir space and the larger the final gas storage capacity is. The higher the water saturation of the reservoir, the more the gas loss during gas storage capacity building and operation is. Optimizing injection-production regime to discharge water and reduce water saturation is an effective way to reduce gas loss in gas storage. In the process of multiple cycles of injection and production, there is a reasonable injection-production balance time, further extending the injection-production balance period after reaching the reasonable time has little contribution to the expansion of gas storage capacity.

Visualizing Groundwater Dispersion: Laboratory Exercise on Dispersivity with Hands-on and Online Students

Longitudinal groundwater dispersion is measured by calculating the spreading of a solute in the direction of groundwater flow as a function of time, with dispersivity being the plume dispersion divided by the groundwater velocity. Two-dimensional physical groundwater flow models were used in a laboratory exercise to illustrate groundwater dispersion to hands-on and online students. Learning assessment of the pedagogical value of the laboratory exercise was based on a student survey and an independent laboratory assignment graded by the course instructor. Both tools indicated that student learning was effectively enhanced by the dispersivity laboratory exercise; however, it was more effective for the hands-on students.

Remediation characteristics of surfactant-enhanced air sparging (SEAS) technology on volatile organic compounds contaminated soil with low permeability

Surfactant-enhanced air sparging (SEAS) is an effective technology for the remediation of volatile organic compounds contamination of medium and high-permeability soil, though applying SEAS to low-permeability soil contamination has rarely been explored. In this study, a series of two-dimensional physical model tests were designed to explore the feasibility and remediation characteristics of SEAS on low-permeability soil. In the test results, the incorporation and increase in surfactant concentration promoted air channel formation in the low-permeability soil, finally reduced the capillary breakthrough pressure and improved the airflow rate. The majority of the exhausted gaseous contaminants were distributed along the horizontal direction, differing from the results observed in medium and high-permeability soils. The exhausted gaseous contaminant concentration changed slightly when the sparging pressure and surfactant concentration increased at relatively low levels and increased as the sparging pressure and surfactant concentration increased further. Increasing the air sparging pressure without surfactant incorporation or with a low surfactant concentration cannot effectively remove the contaminant, while the removal efficiency can be enhanced with further increases in surfactant concentration. The discrete remediation characteristics had been confirmed during SEAS application on low-permeability soil, then the relationships between the ratios of remediation area and remediation extent under different surfactant concentrations and sparging pressures were established for remediation efficiency evaluation. Using this method, the discrete remediation characteristics can be recreated once the surfactant concentration and the sparging pressure were chosen. On the other side, targeted improvements in the remediation area or extent can be achieved by controlling the surfactant concentration and sparging pressure. Through this study, SEAS technology and the proposed evaluation method were successfully implemented in soil with hydraulic conductivity around 9E-7 m/s, which expanded the application scope of SEAS technology for contaminant removal.

The effect of gas injection velocity and pore morphology on displacement mechanisms in porous media based on CFD approach

Because of the unique advantages such as easy miscibility, high temperature resistance and so on, hydrocarbon gas flooding has proved to be a promising technology for enhanced oil recovery in deep reservoirs. In order to reveal the potential mechanism of miscibility and displacement of crude oil and hydrocarbon gas, an innovative two-dimensional physical field model is constructed by coupling Navier-Stokes equations and mass transfer equation. Accordingly, the effect of gas injection velocity and pore morphology on fluid transport and miscibility properties is investigated based on computational fluid dynamics approach. The simulation results demonstrated that the residual oil (RO) content is lower at low gas injection velocity than that at high gas injection velocity due to the better miscibility of fluids. For pore morphology, the RO content increases with increasing pore throat ratio and pore throat angle, which are not related to the gas injection velocity. The blocked pore structure has a negative effect on hydrocarbon gas flooding, resulting in the higher RO content. In addition, the influence of the pore throat length on the RO content is related to the gas injection velocity, which means the RO content increases at low gas injection velocity and decreases at high gas injection velocity with increasing pore throat length.

Two-Dimensional Computational and Physical Modeling of High-Speed Oil Spill Containment Booms

Abstract The main measure of response to aquatic oil spills is the mechanical containment and recovery from the water surface. The majority of containment booms are not effective when the relative ...

Evaluation of By-Pass Fishway Operation for Attraction Efficiency Based on GPS Drifter Field Experiments

The attraction efficiency of a by-pass fishway installed at Gangjeong-Goryeong Weir on the Nakdong River in South Korea was evaluated according to flow rate variation of the main channel. Optimal flow rate that achieved the maximum value of attraction efficiency at the fishway entrance was also determined. The weir can adjust the flow rate of the main channel and the fishway by operating sluice gates. The weighted usable area (WUA) calculated on the basis of habitat suitability criteria (HSC) for target species using River2D (a two-dimensional physical habitat model) was regarded as an indicator of attraction efficiency. The simulated velocity field by River2D was validated by virtue of measured data acquired from GPS drifter field experiments. Additionally, monthly fish monitoring data obtained with a fish trap served as supporting data to confirm the validity of the estimated attraction efficiency. The monitoring results revealed that the fishway attraction efficiency was the highest during the spawning season (from April to June). The target fish used the fishway most frequently in April. However, many other fish species used the fishway in June. Simulation results revealed that the flow rate of the main channel at the weir should be maintained at 190 m3/s in order to most effectively attract the target fish species into the fishway entrance. Managing the optimal flow rate by operating the sluice gate is especially important during the spawning season of the target fish to facilitate upstream and downstream migration.

Stability Analysis and Fracture Patterns of Hard Main Roof in Longwall Top Coal Caving with Large Mining Height

In order to study the fracture patterns of hard main roof in longwall top coal caving (LTCC) with large mining height, a two-dimensional physical similarity model was created to simulate the mining process of No. 8100 large mining height face in Tongxin coal mine, China. The results show that there are three positions of broken line in hard main roof presented with the advance of longwall face, and the underground pressure induced by hard main roof fracturing presents the effect of superposition of large and small periods. It is found that there are two fracture patterns of main roof during the mining process: composite structure of lower cantilever beam and upper voussoir beam with hard main roof and composite structure instability of lower and upper voussoir beam with hard main roof. The underground pressure induced by these two fracture patterns is also analyzed by building mechanical models. In the end, the hydraulic fracture technique is introduced to presplit the main roof and weaken the effect of dynamic loads induced by composite structures instability.

Modeling and simulation of dissolution process of bulk carbide in Fe–1C–1.44Cr low-alloy steel

Because of the complex morphology of bulk carbides in the core of as-cast bearing steel, their dissolution process is complicated to model, since it is difficult to rationally simplify the bulk carbides using a simple geometric shape. In this study, a metallographic image of an actual bulk carbide is transformed into a two-dimensional physical model. A dissolution model for such bulk carbides is established using thermodynamic and kinetic methods, where the diffusion coefficients for carbon and chromium in austenite and the solute concentrations at the phase interface are calculated assuming local equilibrium conditions. The calculation results from the model are compared with the experimental values, after the bearing steel was soaked at 1150 °C, 1175 °C and 1200 °C, the difference between the measured area of bulk carbides in the core and the model calculation results was 65 μm2, 12 μm2 and 30 μm2, respectively.

Experimental Study on the Physical Model of Breakwater at a LNG Wharf in Pakistan

In this paper, a two-dimensional physical model was established in a laboratory sink, the stability of a breakwater structure at a LNG terminal in Pakistan was studied, and the wave propagation simulation of two designed cross-sections was studied. And make conclusions to evaluate the layout scheme and provide a reference for other similar structures.