Solid Wall Research Articles

Skin Cooling of Turbine Airfoils by Single Wall Effusion: Part I—Reduced Order Modeling

Abstract A quasi-1D conjugate reduced order model (ROM) is developed to capture aero-thermal physics of effusion cooling in turbine airfoils. This framework explicitly considers the coolant supply from the leading edge and its distribution to both suction and pressure sides, the internal boundary layer flow between the shell and the inner core, the hole flow, the conduction on the solid walls, as well as the external film coverage. The solid temperature is allowed to vary both in metal shell thickness and the streamwise directions. Empirical correlations are employed to model pressure loss and heat transfer in the internal sections. Compound effect of multiple effusion cooling rows are utilized to capture cooling effectiveness and the heat load. Influence of mainstream static pressure, varying blowing ratios, hole’s diameter, hole’s pitch, coolant total pressure, and total temperature distributions along streamwise direction are taken into account. In Part I, the development and validation of the model is presented, which is shown to be capable of capturing complex internal aero-thermal physics of a turbine airfoil. Film coverage capability is separately validated successfully against available flat plate experimental data, with one case including internal channel and metal conduction. In Part II of this work, effusion cooling configuration is applied over an entire micro turbine vane and an exemplary optimization is carried out in the design space to minimize coolant flow while retaining metal temperature and its gradient below some limits. It is shown in the two-part work that the developed model is suitable for parametric studies of single-wall effusion turbine cooling such that comparative accuracy is obtained at a computational time 105 times lower than computational fluid dynamics (CFD) on a whole turbine vane/blade. Together, these two papers are intended to present, validate, and optimize the ROM for skin cooling in turbine airfoils by single-wall effusion.

Разработка метода и прибора для измерения сил в контактах частиц в условиях флотации микродисперсий золота

Introduction. In flotation of gold-containing ores, metal losses with tailings are mainly related to the fine particle size classes - micro dispersions. Study of the physical nature of the forces in the contacts between the particles, including gold micro dispersions, allows gaining new knowledge associated with the solution of the pressing problem of effective extraction of difficult to extract forms of the precious metal by flotation. Materials and methods. Measurement of the forces in contacts of particles was carried out by sediment volumetric method using the developed device. The method allows to determine the forces in contacts of particles by the volume of their sediment, formed as a result of kinetic destruction of the disperse system. Alluvial gold from the collection formed during the experimental tests of the equipment of separation complexes "Shlich", "Shlich-2", "PGShOK-50-2" was used in the experiments. The results of measuring the forces were supplemented by theoretical studies, which had the aim to estimate the contribution of the fluid volume held by capillary forces in contacts of particles to the volume of sediment. Results. It was found that the volume formed by the kinetic destruction of the disperse system is determined by the force in the contacts of particles, and the volume of capillary held liquid is of subordinate importance. Discussion. It is shown that the results obtained can be explained by involving the notions of boundary layers of fluids with a structure changed under the influence of surface forces. The low-entropic structure of liquid in the boundary layer of hydrophobic surface is caused by forces arising inside liquid itself near weakly interacting surface, and is energetically the least favorable, corresponding to the maximum of free energy. Therefore, the particles behave as if there are hydrophobic attraction forces among them. Conclusion. Uncompensated charges near hydrophilic surface create high-entropic structure of water with normal orientation of its dipoles and increased density, which causes the appearance of structural hydrophilic repulsive forces among particles. Resume. Structural hydrophobic attraction and hydrophilic repulsion are endothermic processes. Their violation will be an exothermic process and its exo-thermicity increases as the temperature rises. The developed method of flotation is based on this property of structural forces: the stability of wetting films in flotation processes of micro-dispersions of minerals is changed by heating water in the boundary layers of air bubbles - hydrophobic cavities in water - due to the condensation heat of hot water vapor. For this purpose, aeration of the flotation system is carried out by a mixture of air and steam. Proposals for practical application and direction of future research. Practical significance of the project is to develop technology for flotation of the most difficult to extract forms of gold. Its essence is based on the effect of preferential adhesion of gold micro-dispersions on its own hydrophobic large particles - a solid wall. Thin plates, flakes and sheets of native gold are used as it. The aggregates formed by the above described mechanisms from poly disperse particles are extracted by flotation. In case of extraction in several steps the rough concentrate can be used as a solid wall (carrier minerals). In further research it is necessary to develop an organizational mechanism of joint processing of ores and gold placers.

Особенности взаимодействия полидисперсных частиц в процессах флотации микродисперсий золота

Introduction. In flotation of large particles, the approach of a particle to a bubble is provided by inertial forces, while in the case of small particles this process proceeds inertially. Inertia less hydrodynamic interaction with the bubble - movement with the liquid flow without contact with the surface of the bubble up to its lower hemisphere - is the main reason for losses of small particles in flotation. Materials and methods. Research was carried out on washing wastes of gold placers of the Petinikan-Bastakh group of deposits and on a sample of ore from the Natalka deposit. Results. It is shown that in a poly disperse system the aggregates are formed mainly from small and large particles with a density greater than the density of the disperse medium. It has been revealed that the mathematical expectation of the number of collisions of particles of the same size is negligibly small. On the other hand, provided that the concentration of small particles in a poly disperse system is not small, the relative frequency of their collision with large particles is close to 1. The obtained result proves the probability of adhesion of small particles to the surface of a large particle. It does not contradict the results obtained by other authors and methods. At flotation extraction of fine particles at the expense of their capture by fast moving coarse particles can make 50 %. Discussion. Theoretical and experimental research of the fine gold extraction technology by flotation with carrier minerals (or solid wall by another terminology), whose distinctive feature is the use of extremely related to the fine ore gold surfaces as carrier minerals - the large metallic gold extracted from the techno-genic placer. It is shown that enhancement of technological performance is achieved through the effective interaction of poly disperse particles with the formation of aggregates extracted by the mechanism of inertial flotation of large particles. Conclusion. The calculation shows that the economic effect is achieved, firstly, by increasing the production of marketable products by reducing metal losses with wastes of processing. Secondly, due to obtaining a higher total cost as a result of reducing the unit cost of gold production in the joint processing of gold-containing raw materials. Resume. The results of the study can be used in the joint ore and placer processing according to the scheme - separation of gold enriched product from the placer with minimal metal losses with the wastes of processing - formation of goldbearing aggregates by adhesion of fine gold ore on thin plates and flakes of placer gold - flotation of fine gold ore on the carrier minerals.

A cellular automata framework for porous electrode reconstruction and reaction-diffusion simulation

Due to the high charge transfer efficiency compared to that of non-porous materials, porous electrodes with larger surface area and thinner solid pore walls have been widely applied in the lithium-ion battery field. Since the capacity and charge-discharge efficiency of batteries are closely related to the microstructure of porous materials, a conceptually simple and computationally efficient cellular automata (CA) framework is proposed to reconstruct the porous electrode structure and simulate the reaction-diffusion process under the irregular solid-liquid boundary in this work. This framework is consisted of an electrode generating model and a reaction-diffusion model. Electrode structures with specific geometric properties, i.e., porosity, surface area, size distribution, and eccentricity distribution can be constructed by the electrode generating model. The reaction-diffusion model is exemplified by solving the Fick’s diffusion problem and simulating the cyclic voltammetry (CV) process. The discharging process in the lithium-ion battery are simulated through combining the above two CA models, and the simulation results are consistent with the well-known pseudo-two-dimensional (P2D) model. In addition, a set of electrodes with different microstructures are constructed and their reaction efficiencies are evaluated. The results indicate that there is an optimum combination of porosity and particle size for discharge efficiency. This framework is a promising one for studying the effect of electrode microstructure on battery performance due to its fully synchronous computation way, easy handled boundary conditions, and free of convergence concerns.

Numerical simulation of subcooled flow boiling for nuclear engineering applications using OpenFOAM

Abstract This work is focused on the development and validation of models and methods for the simulation of wall boiling in nuclear engineering applications with the computational fluid dynamics (CFD) code OpenFOAM. The new chtMultiRegionReactingTwoPhaseEulerFoam solver was developed based on the reactingTwoPhaseEulerFoam solver of OpenFOAM Foundation version 7. The solver is used for the simulation of two-phase flow under consideration of wall boiling and conjugate heat transfer (CHT) between solid structure and two-phase fluid regions. The Euler–Euler approach for two-phase flows was used. The heat flux during wall boiling was calculated with the help of the extended Rensselaer Polytechnic Institute wall heat flux partitioning model, in which the convective heat flux between solid wall and two-phase flow with high void fractions was also considered. The solver was validated against experimental data from the OECD/NEA PWR Subchannel and Bundle Tests benchmark. This Nuclear Power Energy Corporation (NUPEC) database provides data for different fuel assembly subchannel geometries at different thermal-hydraulic conditions. 10 experimental runs with different boundary conditions of the benchmark exercise I-1 were simulated with the chtMultiRegionReactingTwoPhaseEulerFoam solver. The solver showed good numerical stability in all examined cases, which captured different boiling regimes with up to cross-section averaged void fractions of 0.6. The results were compared with measured data for the averaged over the cross-section of the investigated geometry void fractions. Good agreement with experimental data was observed.

Assessment of solving the RANS equations with two-equation eddy-viscosity models using high-order accurate discretization

A challenge that faces high-order methods for industrial applications generally is turbulence modeling at high Reynolds numbers. Large eddy simulation is studied extensively for high-order methods, nevertheless, its computational cost is enormous for industrial applications. The hybrid LES/RANS compromises the computational cost and the modeling error, however, solving the Reynolds-averaged Navier-Stokes equations is a resilient task for high-order methods, due to the non-smooth profiles of the turbulence quantities. Taking into account the complexity with high-order methods and the fairly large modeling errors of the RANS modeling, low-order methods has proved to be more pragmatic. For instance, in the discontinuous Galerkin framework, the polynomial approximation for these quantities leads to large oscillations that obstructs the non-linear solver. To use the high-order methods for industrial cases it is essential to have reliable implementations of two-equation turbulence models in RANS formulations. In this paper, a RANS discretization based on hybridizable discontinuous Galerkin is presented for the standard, TNT, BSL and SST versions of the k−ω model for applications at Reynolds numbers up to 109. A particular focus is given to the treatment of the specific rate of turbulence dissipation ω in the high-order framework. The complexity increases with these types of models as the value of ω goes to infinity at solid walls. Additionally, with minor modifications to the numerical flux definition, the turbulence model formulation can be solved by discontinuous Galerkin method as well. The results show remarkable improvements regarding the error magnitudes and non-linear convergence rate (iterative error) compared to second-order finite volume based solvers.

Prioritising Climate Change Mitigation Behaviours and Exploring Public Health Co-Benefits: A Delphi Study.

Climate change requires urgent action; however, it can be challenging to identify individual-level behaviours that should be prioritised for maximum impact. The study aimed to prioritise climate change mitigation behaviours according to their impacts on climate change and public health, and to identify associated barriers and facilitators-exploring the impact of observed behaviour shifts associated with COVID-19 in the UK. A three-round Delphi study and expert workshop were conducted: An expert panel rated mitigation behaviours impacted by COVID-19 in relation to their importance regarding health impacts and climate change mitigation using a five-point Likert scale. Consensus on the importance of target behaviours was determined by interquartile ranges. In total, seven target behaviours were prioritised: installing double/triple glazing; installing cavity wall insulation; installing solid wall insulation; moving away from meat/emission heavy diets; reducing the number of cars per household; walking shorter journeys; and reducing day/weekend leisure car journeys. Barriers related to the costs associated with performing behaviours and a lack of complementary policy-regulated subsidies. The target behaviours are consistent with recommendations from previous research. To ensure public uptake, interventions should address behavioural facilitators and barriers, dovetail climate change mitigation with health co-benefits and account for the long-term impacts of COVID-19 on these behaviours.

Rectal Bleeding in a Child Revealing a Cavernous Hemangioma of the Sigmoid

Hemangiomas are the most common benign vascular tumors in the pediatric age group. They originate from embryonic remnants of unipotent angioblastic cells. Although hemangiomas may occur anywhere within the abdomen, including the solid organs, hollow viscera, ligaments, and abdominal wall, the liver is the most common site. Cavernous hemangiomas of the sigmoid colon are uncommon vascular malformations usually found in young adults with a long history of episodic and painless rectal bleeding. Imaging plays an essential role in diagnosis and post-therapeutic follow- up. The diagnosis of certainty remains histological and the treatment is essentially surgical. We report a case of cavernous hemangioma of the sigmoid diagnosed in a 5-year-old boy admitted to our hospital for investigation of repeated episodes of rectal bleeding. The diagnosis was confirmed after a histological examination.

Theoretical and experimental study of damaged reinforced concrete shear walls strengthened with FRP composites

The present paper presents the results of a theoretical and experimental program developed to study the seismic performance of precast reinforced concrete wall panels, strengthened with composite materials. These type of elements, also known nowadays as lightly reinforced shear walls with medium ductility (DCM), were widely used between 1955 and 1990 in different European countries (Serbia, Bulgaria, Polonia, Romania etc) being designed at that time without using the principle of shear force associated to the bending resisting moment. The current results refer to the investigation made on five specimens, one “as-built” solid wall, two walls with initial opening and two walls with cut-out opening. Usually, the cut-out procedure is applied cutting the concrete and reinforcements in order to create a new opening or enlarging an existing one. This intervention is widely requested by owners of apartments when they reconfigure the architecture of flats, but this procedure could influence the seismic behaviour by weakening the initial performance of the wall, especially due to the reduction of stiffness. In order to investigate the specimens’ seismic behaviour, in-plane reversed cyclic lateral loadings were applied together with axial vertical loads. The specimens were monitored through the experimental tests using strain gauges, pressure and displacement transducers. Based on the experimental investigations performed on the reference undamaged walls, the specimens were repaired, then after were strengthened with the aim to reestablish the initial capacity of the elements without an important influence to the stiffness. The strengthening strategy proposed had used externally bonded FRP composite reinforcement (EBR-CFRP) and near-surface mounted FRP composite reinforcement (NSM-CFRP). The strengthened elements were tested again to study the behaviour of elements and the effectiveness of the proposed solutions. A numerical analysis was performed in order to check on the accuracy of using simple numerical models to predict the behaviour of strengthened shear walls.

Hydrodynamic Analysis Inside a Circulating Fluidized Bed Boiler Based on Time Change Using CFD

The power generation industry has progressively improved the design of power plants to tackle global climate change. Coal-fired power plants will be cleaner and more efficient with the CFB (Circulating Fluidized Bed) technology in the boiler. CFB boilers have the advantage where the resulting carbon dioxide, SOx, and NOx emissions are significantly reduced. This makes research on CFB boilers widely carried out, especially those using CFD (Computational Fluid Dynamic). This study aims to determine the most appropriate turbulence model using CFD simulations on CFB boilers to analyze the hydrodynamic elements in the boiler against time changes, including the distribution of solid volume fractions, pressure, velocity, and wall shear stress. Three turbulence models were tested as part of the simulation: standard , RNG , and RSM, which were then compared to earlier research. The RNG model produces the closest result to the experimental data, with an error value of 6.24%. Solid volume fraction area is increasingly widespread with values ranging from 0.05 to 0.1 from the furnace’s bottom to a height of 15 m. The high-pressure area further expands at the bottom of the furnace to a height of 15 m, with values ​​ranging from 3 kPa to 10 kPa. The outlet line velocity has increased from 43 m/s to 50 m/s. The wall shear stress increases from 0.75 Pa to 1.1 Pa at the outlet wall.

Improved partially saturated method for the lattice Boltzmann pseudopotential multicomponent flows.

This paper extends the partially saturated method (PSM), used for curved or complex walls, to the lattice Boltzmann (LB) pseudopotential multicomponent model and adapts the wetting boundary condition to model the contact angle. The pseudopotential model is widely used for various complex flow simulations due to its simplicity. To simulate the wetting phenomenon within this model, the mesoscopic interaction force between the boundary fluid and solid nodes is used to mimic the microscopic adhesive force between the fluid and the solid wall, and the bounce-back (BB) method is normally adopted to achieve the no-slip boundary condition. In this paper, the pseudopotential interaction forces are computed with eighth-order isotropy since fourth-order isotropy leads to the condensation of the dissolved component on curved walls. Due to the staircase approximation of curved walls in the BB method, the contact angle is sensitive to the shape of corners on curved walls. Furthermore, the staircase approximation makes the movement of the wetting droplet on curved walls not smooth. To solve this problem, the curved boundary method may be used, but due to the interpolation or extrapolation process, most curved boundary conditions suffer from massive mass leakage when applied to the LB pseudopotential model. Through three test cases, it is found that the improved PSM scheme is mass conservative, that nearly identical static contact angles are observed on flat and curved walls under the same wetting condition, and that the movement of a wetting droplet on curved and inclined walls is smoother compared to the usual BB method. The present method is expected to be a promising tool for modeling flows in porous media and in microfluidic channels.

Harnessing structural hierarchy and multi-material approaches to improve crushing performance of re-entrant honeycombs

This study proposes to improve the crushing performance of re-entrant honeycombs by considering both mechanistic and material ingredients. First, a set of novel hierarchical configurations possessing hexachiral auxetic subordinate cells was designed by replacing the solid cell walls of the conventional re-entrant honeycomb. Then the voids of the modified re-entrant honeycombs and the proposed hierarchical metamaterials were filled with a flexible material by using a multi-material 3D printer. Parametric numerical analyses were performed using validated Finite Element models to identify optimal metamaterial architectures. A set of samples, including traditional and developed configurations, were 3D printed and subjected to uniaxial compression loading. The deformation mechanism, compressive strength, and energy absorption of the samples were compared at different strain levels. The results show that introducing hexachiral hierarchies along the ribs prolongs the duration of plastic deformation and keeps the auxeticity of the samples at larger strains. This provides a stable and long post-yield plateau in the compressive stress-strain curve that brings considerable improvement in energy absorption and compressive strength. In addition, multi-material approaches with the combination of rigid photopolymer and flexible rubber-like material also contribute to stabilizing the deformation mechanism of both conventional and developed hierarchical re-entrant auxetic configurations. The proposed hierarchical auxetic structures present more specific compressive strength and specific energy absorption (up to ~150 %) compared to conventional re-entrant auxetic honeycombs. Overall, the proposed hybrid designed strategies can be leveraged to manipulate the collapse mechanism and improve crushing performance.

Criterion for bubble encapsulation on drop impact onto a liquid film

The phenomenon of bubble encapsulation results from droplet impact on a liquid film for specific impact conditions, but there is no established criterion for predicting its onset. Phenomenon visualization from two perspectives, the common lateral perspective and a bottom perspective, provided insights into the dynamics and formation mechanisms. Namely, the bottom shadowgraphs show capillary wavy patterns and perturbations imposed on the steady liquid film, which suggests a greater role of the liquid film in the onset of bubble encapsulation. Also, some considerations about the cavity development underneath the bubble limited by the solid wall allow concluding that the cavity shape is independent of the bubble encapsulation phenomenon. Additionally, using the bottom shadowgraphs, the crown closure time shows a systematic decrease in the dimensionless film thickness of 0.5<δf<0.6, which will be subject of future work. Finally, while most drop impact correlations focus on using the droplets' characteristics and thermophysical properties, the experimental results point in a different direction. Considering correlations relating the Ohnesorge and Reynolds numbers, the new criterion for the onset of bubble encapsulation uses drop characteristics and properties in the Reynolds number, while the liquid film thickness and thermophysical properties are used in the Ohnesorge number because most of the crown material comes from the liquid film. Therefore, the criterion based on 100% occurrence of bubble encapsulation is not a threshold, but a range: kbe=ln(34.5/ReD)/ln(Ohf), with kbe∈[1.022,1.142]. Other authors observed this phenomenon and despite being outside the validation range of this correlation, the values are close to their boundaries.

Insulation behavior of foamed based geopolymer as a thermally efficient sustainable blocks

The importance of sustainability and energy efficiency in the construction and design of houses is crucial in today's environment. The material used as an insulation layer within the building envelope restricts heat transfer through it. However, heat transfer depends upon the characteristics of the insulating layers and their properties. Therefore, creating materials that possess low thermal conductivity while maintaining their mechanical, physical and durability properties is of utmost significance. The aim of this research is to explore the feasibility of utilizing foamed insulating geopolymer blocks as a means to address energy efficiency and environmental sustainability issues. The research involves utilizing copper slag and glass powder as the primary raw materials to produce the geopolymer. Additionally, the technique of foaming is applied to enhance the thermal resistance of the resulting product. The study results revealed that the foamed geopolymer material exhibited thermal conductivity in the range of 0.13 to 0.16 W/mK. Also, the developed product was subjected to conjugate thermal analysis to understand the heat transfer behavior of material. The heat transfer analysis is performed by in-house developed conjugate heat transfer solver in OpenFOAM. The variation of temperature through the solid geopolymer walls to internal room environment is reported, and Nusselt number at the solid–fluid interface is plotted to observe the insulation strength of developed geopolymer. The findings suggest the developed product can provide better thermal insulation than conventional material, in addition to this the foamed geopolymer can be treated as sustainable material as it utilizes waste and reduces the energy requirements of buildings.

Thermal Cnvection of Two Immiscible Liquids in a 3D Channel with a Velocity Field of a Special Type

The three-dimensional stationary flow of two immiscible liquids in a layer bounded by solid parallel walls is investigated. The upper wall is thermally insulated, and the lower one has a temperature field quadratic in horizontal coordinates. Velocity fields in liquids have a special form: their horizontal components are linear in the coordinates of the same name. The resulting conjugate boundary value problem in the framework of the Oberbeck–Boussinesq model is inverse and is reduced to a system of ten integro-differential equations. For small Marangoni numbers (creeping current), the problem is solved analytically. The nonlinear problem is solved by the tau method. It is shown that the solution of the nonlinear problem with a decrease in the Marangoni number is approximated by the solution of the creeping flow problem. The analysis of the influence of physical and geometric parameters, as well as the behavior of temperature on the substrate, on the structure of convection in layers is carried out.

Effect of Opening on the Performance of Bamboo-Reinforced Concrete Wall Panels under One-Way In-Plane Action

This study focuses on the effect of opening on the performance of bamboo-reinforced concrete wall panels subjected to one-way in-plane action. The study evaluates the performance of six bamboo-reinforced concrete wall panels, of which three are solid wall panels and the remaining three specimens are having an opening at its center. All the prototype specimens were subjected to a uniformly distributed load that was applied at an eccentricity of 1/6 of its wall thickness. The specimens considered in this study had a constant slenderness ratio of 25, with varying aspect ratios and thinness ratios. The aspect ratio considered for the wall panels were 1, 1.20, and 1.52, and thinness ratios considered include 16.50, 20.75, and 25. The area of the opening provided was exactly 25% of the area of the specimen and was provided at the center of the specimen. The study reveals that the load-carrying capacity of a wall panel is dependent on its aspect ratio and thinness ratio. The ultimate load was found to decrease with an increase in aspect ratio, whereas it increased with increase in thinness ratio irrespective of the presence of the opening.

Improvement of cleaning parameters of pipeline elements based on simulation of movement of solid magnetite particles in electrically conductive liquid

The unique properties of liquids that can interact with electric and magnetic fields are used in mechanical engineering, technology and medicine. The possibility of the influence of the magnetic field on the solid particles of the liquid in the pipeline allows cleaning of the solid walls of the pipeline, which is the object of the study. Magnetic liquids are solutions of ferromagnets in a liquid, and their physical properties in a magnetic field cause structural transformations in such liquids. The treatment of electrically conductive liquids in a magnetic field and their use for cleaning water from oil or oil residues are considered. On the basis of numerical modeling, the movement of solid particles of magnetite, which is part of an electrically conductive liquid, was investigated by jointly solving the equations of Reynolds, Maxwell, non-discontinuity and the turbulence model. The physical phenomena of the movement of solid particles of magnetite-based conductive liquid in various elements of the pipeline were determined, which improved the parameters of cleaning liquids contaminated with oil and oil. The magnetic particles of the electrically conductive liquid quite nicely fill the boundaries of the intersection if there is a flow reversal, as it happens in radiators. An increase in the intensity of the magnetic field leads to a change in the velocity profile of the conductive liquid, which prevents magnetite particles from penetrating close to the wall. An increase in the power of the magnetic field makes it possible to detach the contamination from the walls of the pipeline together with the solid particle of magnetite. A 73 % increase in wear in certain sections of the pipeline is due to the effect of the centrifugal force acting on the particle during rotation. The sudden expansion of the flow makes it difficult for particles to reach the pipe surfaces, which worsens the cleaning conditions. The number of particles on the surface is 82 % less compared to the absence of sudden expansion

Comparative study of the imbibition patterns of two types of surfactants and their residual oil morphology in low-permeability reservoirs

Forward imbibition and reverse imbibition are common imbibition modes in reservoir development. In order to understand the characteristics of recovery efficiency, sweep mode and residual oil morphology of Surfactin (reverse imbibition) and an anionic gemini surfactant (AG, forward imbibition) systems, multiscale imbibition experiments were carried out. The core and microtube experiments showed that the capillary force was dominant in the Surfactin solution and the Marangoni force was dominant in the AG solution, when the model was horizontal. In the two-dimensional pore network imbibition experiment, the recovery rate of reverse imbibition was higher than that of forward imbibition, which was consistent with the core experiment. In Surfactin solution, the dominant imbibition channel formed and swept in a fan-like pattern, however, in AG solution it failed to form a dominant imbibition channel and swept in a finger-in pattern. In the initial stage, the imbibition rate in Surfactin solution was significantly higher than that of AG solution, and its sweep efficiency was 1.5 times higher than that of AG solution. In terms of the morphology of residual oil, less oil remains on the wall during reverse imbibition, and columnar and cluster residual oil was easy to form in the channel. After long-term molecular diffusion, the Marangoni effect can effectively improve mixing between the oil and water phases, thus improving the sweep efficiency. In the case of forward imbibition, there were more residual oil films on the solid wall and punctiform residual oil was easily formed in the channel. These discoveries provide a basis for the selection of imbibition fluids or the optimization of oil recovery processes in reservoir development.

Molecular biological features of cyst wall of adamantinomatous craniopharyngioma

The molecular biological differences between cyst walls and those in solid bodies are the foundation of the outcomes. In this study, the CTNNB1 mutations were confirmed by DNAsequencing; CTNNB1 expression levels were detected by PCR; the differences between solid bodies and cyst walls in proliferative capacity and tumor stem cell niches were assessed by immunohistochemistry; the effect of the residual cyst wall on recurrence was assessed by follow-up. Mutations in the CTNNB1 in the cyst wall and the solid body were identical in each case. No differences were found in the transcriptional level of CTNNB1 between the cyst walls and the solid bodies (P = 0.7619). The cyst wall showed a pathological structure similar to the solid body. Proliferative capacity of cyst walls was stronger than that of solid body (P = 0.0021), and β-catenin nuclear positive cells (cell clusters) in cyst walls were more than that in solid tumor (P = 0.0002). The retrospective 45 ACPs showed residual cyst wall was significantly associated with tumor recurrence or regrowth (P = 0.0176). Kaplan–Meier analysis showed there was a significant difference in the prognosis between GTR and STR (P < 0.0001).The cyst wall of ACP contained more tumor stem cell niches which could lead to the recurrence. According to the above-mentioned, a special attention to the management of the cyst wall should be paid.

Analytical study on an oscillating buoy integrated with a perforated structure with a quadratic pressure drop condition: A case study on a WEC-perforated breakwater integration system

A general analytical method for solving the linear wave interactions with the integration systems comprising an oscillating buoy and perforated structure is presented, with a quadratic pressure drop condition on the perforated surface. Using the method of variable separation and eigenfunction expansion, the motion response of the buoy and total velocity potential can be solved using a two-loop iterative method. The method is validated against the published results. The integration system with a heaving WEC arranged inside a perforated breakwater was investigated particularly. Under the quadratic pressure drop condition, the symmetry of the hydrodynamic coefficients and Haskind relation, are found no longer satisfied, and the dissipation through the perforated wall also contribute to the damping coefficient. Effects of the damping of the power take-off system, front wall porosity, wave amplitude, and position of the WEC are investigated in particular. It was found that the horizontal and vertical wave forces on the WEC increase significantly as wave amplitude increases; however, the hydrodynamic efficiency decreases. When the WEC is near the solid rear wall, the horizontal wave forces on the WEC and solid rear wall increase significantly at the frequencies of piston mode gap resonance and heave motion resonance.