Slit Walls Research Articles

Study on the influence of slit pipe wall thickness on the rock breaking effect of slit charge explosion

AbstractIn this study, the influence of slit pipe wall thickness on shaped charge blasting efficiency was investigated. The influence of different slit pipe wall thicknesses on the dynamic behavior of slotted charge blasting was analyzed by a combination of experimental observations and numerical simulations. Polymethyl methacrylate (PMMA) was used as a rock simulation material to prepare slit pipes with different slit pipe wall thicknesses (0.5, 1.0, and 1.5 mm). A dynamic caustics system is used to capture the crack propagation process. ANSYS/LS‐DYNA was used for the numerical simulation analysis. The experimental results show that there is a positive correlation between the slit pipe wall thickness and the crack propagation length, velocity, and dynamic stress intensity factor. With increasing slit pipe wall thickness, the directional propagation and energy concentration ability of cracks are significantly improved, but an increase in the slit pipe wall thickness will also promote the propagation of secondary cracks. In addition, the numerical simulation results support the experimental observations and reveal the existence of an optimal slit pipe wall thickness that can maximize the blasting efficiency while maintaining structural integrity. This study not only deepens the understanding of the physical laws of the blasting process but also provides a practical reference for the optimal design of slotted charges in engineering applications.

The dynamics of red blood cells traversing slits of mechanical heart valves under high shear

Hemolysis, including subclinical hemolysis, is a potentially severe complications of mechanical heart valves (MHVs), which leads to shortened red blood cell (RBC) lifespan and hemolytic anemia. Serious hemolysis is usually associated with structural deterioration and regurgitation. However, the shear stress in MHVs’ narrow leakage slits is much lower than the shear stress threshold causing hemolysis and the mechanisms in this context remain largely unclear. This study investigated the hemolysis mechanism of RBCs in cell-size slits under high shear rates by establishing in vitro microfluidic devices and a coarse-grained molecular dynamics (CGMD) model, considering both fluid and structural effects simultaneously. Microfluidic experiments and computational simulation revealed six distinct dynamic states of RBC traversal through MHVs' microscale slits under various shear rates and slit sizes. It elucidated that RBC dynamic states were influenced by not only by fluid forces but significantly by the compressive force of slit walls. The variation of the potential energy of the cell membrane indicated its stretching, deformation, and rupture during traversal, corresponding to the six dynamic states. The maximum forces exerted on membrane by water particles and slit walls directly determined membrane rupture, serving as a critical determinant. This analysis helps in understanding the contribution of the slit walls to membrane rupture and identifying the threshold force that leads to membrane rupture. The hemolysis mechanism of traversing microscale slits is revealed to effectively explain the occurrences of hemolysis and subclinical hemolysis.

Dispersion in a slit with crossflow filtration through a porous wall

Crossflow filtration is a separation technique where fluid flows tangentially across a membrane or porous media, reducing clogging by sweeping away retained particles and allowing continuous filtration. Dispersion of solute matter in crossflow filtration plays an essential role in the separation performance of many industrial processes. The current work aims to generalize the Taylor dispersion theory and study the solute transport in a slit–porous medium system with a crossflow. The solute is depleted by the porous medium at the slit top porous wall or the interface between the slit and the porous medium, where the continuity of the solute concentration and mass flux is applied. The solute is simultaneously transported axially by the main flow along the slit and vertically by the crossflow perpendicular to the slit. Using the Reynolds decomposition and cross-sectional averaging techniques, the generalized reduced-order model for the advection-dispersion solute transport in the slit–porous medium system with the presence of a crossflow is established, where the effective velocity of the main flow and the effective dispersion coefficient are obtained. The analysis of the results reveals that the nondimensional Taylor dispersion coefficient scales with the Peclet numbers for the crossflow and the main flow, respectively, as DT∼Pev−5/3 (when Pev≥20) and DT∼Peu2. The proposed theoretical model, along with the findings of this study, paves the way for the fundamental study of dispersion in more complex systems.

Seismic performance of slit steel plate shear walls strengthened by FRP laminate

Steel plate shear walls with slits are widely used in high–rise building structures due to their flexible arrangement and high ductility. After long-term service, cracks may occur in the slit steel plate shear walls due to repeated buckling and stress concentration. In this study, an FRP–steel composite slit steel plate shear wall was proposed to improve its mechanical performance and service function. Experimental and finite element analysis were conducted to investigate the performance of slit steel plate shear walls reinforced with FRP under low cycle reciprocating load. It was shown that the use of FRP to strengthen slit steel plates can effectively improve the out–of–plane stability of the structure and reduce the stress concentration at the slits. The stiffness and load–bearing capacity of the reinforced slit steel plate shear walls were significantly enhanced. The reinforcement effect of FRP did not significantly affect the energy dissipation capacity of the shear walls. A numerical study was performed to investigate the optimal orientation of the FRP arrangement. The analysis revealed that when the carbon fibers were arranged horizontally and vertically orthogonally, the structure exhibited better seismic properties. This study can not only improve the seismic performance of slit steel plate shear walls, but also have engineering implications for the seismic reinforcement of existing slit steel plate shear walls.

Investigation on laminated steel slit shear walls with low yield steel

To improve the energy dissipation capacity of steel slit shear walls made of thin plates and mitigate the adverse effects from the large out-of-plane deformation and potential local buckling failure, a novel laminated steel slit (LSS) shear wall assembled from two single-layer steel slit (SSS) shear walls is proposed in this study. First, the theoretical analysis method for predicting the shear strength and stiffness of the LSS shear walls is proposed. To validate the theoretical method as well as investigate the hysteretic performance of the LSS shear walls, two specimens made from different materials, common carbon steel and low yield steel, are designed and tested experimentally under quasi-static cyclic loading. Refined finite element models are developed to simulate the hysteretic behaviors of the LSS shear walls, which show good agreement with the test results. Further, the performance differences between the LSS shear walls and SSS shear walls are analyzed using the validated numerical simulation approach. The strength and stiffness of the LSS shear walls are greater than the summation of the individual SSS shear walls, attributed to the interaction between the different layers in the LSS shear walls. The energy dissipation efficiency of the LSS shear walls is improved and the stiffness degradation is effectively delayed, thanks to the incorporation of the low yield steel material. Finally, to evaluate the effects of the contributing factors on the seismic performance of the LSS shear walls, a series of parametric analyses are performed. Parametric analysis results show that the use of the low yield steel helps to improve the ductility and energy dissipation capacity of the LSS shear walls and delay the stiffness degradation. A large link width ratio, small link length ratio and large link thickness ratio can all contribute to a large strength, stiffness and absolute energy dissipation of the LSS shear walls, but the former two at the same time deteriorate the stiffness degradation.

Effects of innovative reinforced concrete slit shaft configuration on seismic performance of elevated water tanks.

Elevated water tanks are considered crucial infrastructure due to their significant role in supporting essential services. A strong ground motion may result in a failure or significant damage to a reinforced concrete shaft of an elevated water tank because hysteric energy dissipation is limited to the formation of plastic hinges at the base of the shaft, while the nonlinear properties of the rest of the shaft remain underutilised. The innovative system of assembling RC shafts for elevated water tanks using a slit wall technique was developed to enhance energy dissipation along with the shaft height by introducing slit zones. The comparative nonlinear dynamic analysis between three-dimensional models of elevated water tanks with different shaft diameters and heights was conducted using SAP2000 software. The results of elevated water tanks with slit and solid reinforced concrete shafts were compared. The research findings showed that during a seismic event, the slit zones increased the ductility of the shaft, reduced stress concentration in the lower part of the shaft, and provided uniform stress distribution throughout the shaft's height. The effect of the innovative system is especially noticeable in the elevated water tanks with tall and slender shafts.

Molecular simulation of the adsorption and diffusion properties of CH4 and CO2 in the microporous system of coal

Micropores are the main adsorption sites for gases in coal. The research of the adsorption and diffusion pattern of gases in micropores is important for CO2-ECBM engineering and other measures to improve production. In this study, a multiscale microporous system with intramolecular pores, intermolecular pores, and slit pores is proposed. Adsorption and diffusion characteristics of CH4 and CO2 in different microporous systems were investigated. The results show that the adsorption of different microporous systems is basically consistent at low pressures (<2 MPa). Upon further increase in pressure, adsorption increases with increasing slit pore size. Gas molecules in coal are preferentially adsorbed in the intramolecular and intermolecular pores, and gas molecules in the slit pores are preferentially adsorbed in the slit pore walls. The increase in gas pressure and slit pore size decreases the proportion of gases adsorbed in the intramolecular and intermolecular pores and also increases the proportion adsorbed in the slit pores. Increase in size of the slit pores and decrease in adsorption will result in an increase in self-diffusion coefficients of gases. The results of self-diffusion coefficients of pores with different scales indicate that slit pores have the largest self-diffusion coefficients, followed by the intermolecular pores, and the smallest for the intramolecular pores. The isosteric heat of gases tends to decrease and then increase with increasing adsorption. The increase of slit pore size will decrease interaction energy. This study gives a reference for adsorption and diffusion mechanisms of gases in microporous systems, as well as a basis for gas injection displacement studies.

Molecular simulation of the impact of surface roughness on carbon dioxide adsorption in organic-rich shales

This study investigates the adsorption behavior of carbon dioxide in organic nanopores with different surface roughness. The nanopores are constructed by sinusoidally corrugating the graphite slit pore walls. By computing the density distributions, adsorption quantities and orientation of carbon dioxide under various pressure and roughness conditions, we elucidate the impacts of surface roughness on carbon dioxide adsorption in organic nanopores. The Langmuir-Freundlich adsorption model is utilized to fit the isotherms of CO2 adsorption under three different roughness conditions. the results show that increasing surface roughness led to the increase in the adsorption of carbon dioxide, as the relative roughness increased from 0% to 12.92%, the average CO2 adsorption capacity increased by 0.003 mmol/m2. Both the adsorbed layer density and monolayer maximum adsorption capacity increased concurrently with escalating roughness. Moreover, carbon dioxide molecules preferentially aligned parallel to the rough organic surface within the adsorption layer, consistent with the smooth graphitic wall configuration. All simulations, observations, and calculations were performed through grand canonical Monte Carlo (GCMC) simulations. These findings provide insights into the influence of surface roughness on CO2 adsorption, especially in organic nanopores, which has substantial implications for carbon capture and geological sequestration applications. The results could facilitate optimization of strategies for efficient, secure geological CO2 storage.

Heat transfer performance and entropy generation analysis of Taylor–Couette flow with helical slit wall

The turbulent flow between concentric cylinders and its heat transfer performance is studied by the large eddy simulation. The models with longitudinal slit and helical slit spacing in the range from 168 to 672 mm on the outer cylinder are investigated to compare their heat transfer ability. Further, the notion of field synergy and entropy formation serves as the foundation for evaluating heat transfer qualities. According to the results, the enhancement effect of helical slits on heat transfer is better than that of longitudinal slits. Helical slits are more effective in promoting fluid mixing at different temperatures within the annulus. In terms of field synergy, the helical slit models exhibit a smaller field synergy angle compared to the longitudinal slit model at various Reynolds numbers from 3061 to 4592. Results of using helical slits indicate an improved coordination between the velocity and temperature fields. Thermodynamic analysis reveals that the helical slit models have lower entropy generation as compared to the longitudinal slit models. Higher efficiency in energy utilization and superior heat transfer properties of the helical slit models are noticed. Findings of this study provide valuable insights for the optimal design of various rotating machinery applications.

Self-Assembly of Symmetric Copolymers in Slits with Inert and Attractive Walls.

Although the behavior of the confined semi-dilute solutions of self-assembling copolymers represents an important topic of basic and applied research, it has eluded the interest of scientists. Extensive series of dissipative particle dynamics simulations have been performed on semi-dilute solutions of A5B5 chains in a selective solvent for A in slits using a DL-MESO simulation package. Simulations of corresponding bulk systems were performed for comparison. This study shows that the associates in the semi-dilute bulk solutions are partly structurally organized. Mild steric constraints in slits with non-attractive walls hardly affect the size of the associates, but they promote their structural arrangement in layers parallel to the slit walls. Attractive walls noticeably affect the association process. In slits with mildly attractive walls, the adsorption competes with the association process. At elevated concentrations, the associates start to form in wide slits when the walls are sparsely covered by separated associates, and the association process prevents the full coverage of the surface. In slits with strongly attractive walls, adsorption is the dominant behavior. The associates form in wide slits at elevated concentrations only after the walls are completely and continuously covered by the adsorbed chains.

Transit Time Theory for a Droplet Passing through a Slit in Pressure-Driven Low Reynolds Number Flows.

Soft objects squeezing through small apertures are crucial for many in vivo and in vitro processes. Red blood cell transit time through splenic inter-endothelial slits (IESs) plays a crucial role in blood filtration and disease progression, while droplet velocity through constrictions in microfluidic devices is important for effective manipulation and separation processes. As these transit phenomena are not well understood, we sought to establish analytical and numerical solutions of viscous droplet transit through a rectangular slit. This study extends from our former theory of a circular pore because a rectangular slit is more realistic in many physiological and engineering applications. Here, we derived the ordinary differential equations (ODEs) of a droplet passing through a slit by combining planar Poiseuille flow, the Young-Laplace equations, and modifying them to consider the lubrication layer between the droplet and the slit wall. Compared to the pore case, we used the Roscoe solution instead of the Sampson one to account for the flow entering and exiting a rectangular slit. When the surface tension and lubrication layer were negligible, we derived the closed-form solutions of transit time. When the surface tension and lubrication layer were finite, the ODEs were solved numerically to study the impact of various parameters on the transit time. With our solutions, we identified the impact of prescribed pressure drop, slit dimensions, and droplet parameters such as surface tension, viscosity, and volume on transit time. In addition, we also considered the effect of pressure drop and surface tension near critical values. For this study, critical surface tension for a given pressure drop describes the threshold droplet surface tension that prevents transit, and critical pressure for a given surface tension describes the threshold pressure drop that prevents transit. Our solutions demonstrate that there is a linear relationship between pressure and the reciprocal of the transit time (referred to as inverse transit time), as well as a linear relationship between viscosity and transit time. Additionally, when the droplet size increases with respect to the slit dimensions, there is a corresponding increase in transit time. Most notably, we emphasize the initial antagonistic effect of surface tension which resists droplet passage but at the same time decreases the lubrication layer, thus facilitating passage. Our results provide quantitative calculations for understanding cells passing through slit-like constrictions and designing droplet microfluidic experiments.

Seismic behavior of self-centering concrete-filled square steel tubular frame with slit steel plate shear walls

A self-centering concrete-filled square steel tubular frame with slit steel plate shear walls (SC-SSPSW) adopting post-tensioned (PT) column base was proposed in this study. The slit steel plate shear walls (SSPSWs) with edge stiffeners were only connected to the beams. Cycle tests were conducted on three 1/3 scaled single-span two-story specimens to investigate their mechanical and seismic behavior, and the formulas for beam and column internal forces considering frame expansion effects were derived. Finite element (FE) models of SC-SSPSWs were established, and the FE results agreed well with the test results. The results indicate that the hysteretic curves of specimens exhibit a typical double flag shape, and the residual deformation of all specimens is approximately 0.20% when loading to 2.0% story drift. Damage is primarily concentrated in the SSPSWs while other structural members remain elastic, and favorable resilience and energy dissipation capacity are achieved. With an increase in the width-to-thickness ratio or aspect ratio of links while keeping the thickness of SSPSWs unchanged, the energy dissipation decreases, and the self-centering capacity improves. The column that expands in the same direction as the loading direction bears more lateral loads. The theoretical gap opening value, PT tendons force, as well as beam axial force agree well with the test and FE results.

All-Optical Rapid Formation, Transport, and Sustenance of a Sessile Droplet in a Two-Dimensional Slit with Few-Micrometer Separation.

We present a sessile droplet manipulation platform that enables the formation and transport of a droplet on a light-absorbing surface via local laser-beam irradiation. The mechanism relies on solutocapillary Marangoni flow arising from a concentration gradient in a binary mixture liquid. Because the mixture is strongly confined in a two-dimensional slit with a spacing of a few micrometers, the wetting film is stably sustained, enabling the rapid formation, deformation, and transport of a sessile droplet. In addition, to sustain the droplet in the absence of laser irradiation, we developed a method to bridge the droplet between the top and bottom walls of the slit. The bridge is stably sustained because of the hydrophilicity of the slit wall. Splitting and merging of the droplet bridges are also demonstrated.

Theoretical and experimental investigations of steel plate shear walls with diamond openings

Steel plate shear walls (SPSWs), used in many high-rise buildings, have been the focus of considerable research. In existing designs, stress concentrations occur at the two ends of the rectangular belt of a slit shear wall. In contrast, the middle region is virtually unable to enter into the plastic state. Consequently, the strength and ductility of these members are not fully utilized. To resolve this, an SPSW with diamond openings (SPSW-DO) is proposed. In the proposed design the seismic energy is dissipated through the flexure and shear deformations of butterfly links on the wall; hence, the energy dissipation capacity of the SPSW-DO is fully utilized. In this study, the theoretical formulas for predicting the strength and elastic stiffness of the SPSW-DO are derived. Each butterfly link has three potential failure modes depending on the opening parameters: bending, bending–shear, and shear. A design procedure to determine the parameters of the opening is suggested according to the shear requirement for the intermediate section of butterfly links. Based on the experimental results of two specimens with different height-to-width ratios subjected to cyclic loading, the SPSW-DO is found to have reliable seismic performance. Finite element models are also developed to reproduce the experimental behavior, and the structural characteristics of the wall and the potential locations of fractures on the infill plate are predicted. Theoretical formulas for the elastic stiffness and strength of the system are also verified through comparison with the experimental results.

Seismic behavior and shear capacity of shear-dominated T-shaped RC walls under cyclic loading

T-shaped walls are widely applied in tall buildings because of their high stiffness and the demand for structural layout, but the flange affects the shear performance of the wall. To investigate the shear failure mechanism of shear-dominated T-shaped reinforced concrete (RC) walls and the difference between the shear performance in the flange-in-tension and flange-in-compression directions, cyclic tests were carried out on three T-shaped RC walls. Numerical models were established for the parametric analysis of shear capacity in different loading directions, and the shear capacity calculation in various specifications was evaluated. The results showed that the failure regions of both specimens with flexural and shear failure were concentrated at the web tip, and the web tips of the shear failure specimens were more seriously damaged. Furthermore, reducing the shear span ratio significantly reduced ductility and energy dissipation capacity and increased the proportion of shear deformation to the total deformation in the plastic hinge area. The decrease in the horizontal distribution reinforcement ratio resulted in the slitting of the T-shaped wall, and the increase in deformation capacity owing to the slit wall compensated for the reduction in deformation capacity caused by the enhancement of the shear effect. Based on the results of the numerical simulation, the current codes failed to consider and distinguish the effect of the tensile and compressive flanges on the shear capacity of the T-shaped wall and were unable to predict the shear capacity of the T-shaped wall well.

Оценка степени влияния фактора подвижности стенок щели при расчёте величины протечек в рабочей части спирального компрессора. Часть 2

Leakage of the working substance in the compressor's flow gaps accounts for a large share of its volumetric losses. The optimality of calculated and approximated characteristics depends on the accuracy of quantitative component determination. Accordingly, an adequate and qualitative mathematical model should include the factor of non-stationarity of the leakage process, taking into account the mobility of scroll elements. At the same time, the real properties of the working medium, characterized by the compressibility coefficient, play an important role in the nature of leakage. Thus, in this article the task of creating a mathematical model adequate to the actual process of compression and allowing to estimate the degree of influence of the slit walls mobility on the leakage through them is set. The result of numerical calculations has a smaller error in relation to experimental data, and it also showed a significant influence on the leakage rate of both the pressure difference at the edges of the slot and the viscosity properties of the vapour-oil mixture, a significant percentage of which is oil.

Impedance Response of Ionic Liquids in Long Slit Pores

We study the dynamics of ionic liquids in a thin slit pore geometry. Beginning with the classical and dynamic density functional theories for systems of charged hard spheres, an asymptotic procedure leads to a simplified model which incorporates both the accurate resolution of the ion layering (perpendicular to the slit pore wall) and the ion transport in the pore length. This reduced-order model enables qualitative comparisons between different ionic liquids and electrode pore sizes at low numerical expense. We derive semi-analytical expressions for the impedance response of the reduced-order model involving numerically computable sensitivities, and obtain effective finite-space Warburg elements valid in the high and low frequency limits. Additionally, we perform time-dependent numerical simulations to recover the impedance response as a validation step. We investigate the dependence of the impedance response on system parameters and the choice of density functional theory used. The inclusion of electrostatic effects beyond mean-field qualitatively changes the dependence of the characteristic response time on the pore width. We observe peaks in the response time as a function of pore width, with height and location depending on the potential difference imposed. We discuss how the calculated dynamic properties can be used together with equilibrium results to optimise ionic liquid supercapacitors for a given application.

Modelling diffusive transport of particles interacting with slit nanopore walls: The case of fullerenes in toluene filled alumina pores

Accurate modeling of diffusive transport of nanoparticles across nanopores is a particularly challenging problem. The reason is that for such narrow pores the large surface-to-volume ratio amplifies the relevance of the nanoscopic details and of the effective interactions at the interface with pore walls. Close to the pore wall, there is no clear separation between the length scales associated with molecular interactions, layering of the solvent at the interface with the pore and the particle size. Therefore, the standard hydrodynamic arguments may not apply and alternative solutions to determining average transport coefficients need to be developed. We here address this problem by offering a multiscale ansatz that uses effective potentials determined from molecular dynamics simulations to parametrise a four state stochastic model for the positional configuration of the particle in the pore. This is in turn combined with diffusivities in the centre of the pore and at the pore wall to calculate the average diffusion constant. We apply this model to the diffusion of fullerenes in a toluene filled slit nanopore and calculate the mean diffusion coefficient as a function of the pore size. We show that the accuracy of our model is affected by the partial slip of the toluene on the pore wall.

Heat transportation performance and entropy generation analysis of Iron (II, III) oxide microparticles on Taylor Couette flow over a slit wall

Despite the significance of Taylor Couette flow over a slit wall in industries, little is known about the impact of Iron (II, III) oxide (Fe3O4) microparticle on the dynamics and heat transfer properties of Taylor-Couette flow. This study aims to investigate the effect of solid particles on heat transfer performance of Taylor-Couette flow over a slit wall. The trajectory of particles in the flow field is described utilizing Eulerian-Lagrangian method in this report. The Fe3O4-water suspension with particle size dp = 1μm, 5μm and particle volume fraction φ = 0.5 % , 1.0 % , 1.5% are considered. Results reveal that the heat transfer performance of Taylor vortex is remarkable enhanced by adding the solid particles inside the annular gap compared to pure water. Solid particles in the annular gap show the movement of migration from inner to outer cylinders due to the interaction with fluid, which causes more disordered flow field around the inner cylinder. The addition of particles could significantly thin the velocity and temperature boundary layers. Frictional and thermal entropy generation display a reverse tendency with increasing particle volume fraction and size. Thermal entropy generation appears obviously higher than frictional entropy generation. Suspension with φ = 1.5% and dp = 1μm makes optimal performance of Taylor vortex because of the minimum entropy generation and boundary layers.

Multi-level parabolic shape slit shear walls

This paper presents a new system called multi-level slit shear wall for improving the behavior of structures during low and moderate earthquakes. This system is similar to the slit shear wall that has several rows of parabolic shape slits, but each row participates in load bearing at a certain drift ratio. While maintaining ductility capacity, this system has smaller elastic stiffness and larger yield displacement compared to conventional slit shear wall. This will reduce the induced seismic force in the early stages of loading and will improve the structure behavior in the event of moderate earthquakes. Experimental study and finite element modeling are used to determine the proposed formulae related to elastic stiffness, yield strength, ultimate strength and demands on boundary element.