Solid-liquid Interactions Research Articles

Studies on flow properties of Bengal gram (Cicer arietinum) flour for effective handling and storage strategies

AbstractBengal gram flour is in great demand and has extensive application due to its nutritional, functional, and sensory properties. The study summarizes the characteristics and compared the flow behavior of two varieties of Bengal gram flour (P372 and P3043) with commercial Barik sample with respect to chemical composition, wettability, physical properties, shear properties, compressibility, and dynamic properties, along with particle size and shape. The result showed that the median particle size distribution of the Bengal gram flour samples ranged between 53.59 and 63.46 μm. More fine particles were found in commercial Barik sample (11.09 μm), and larger particles were found in P372 (118.07 μm) and P3043 (116.47 μm). Similarly, the particle shape (circularity) was found higher in P372 (0.84) and P3043 (0.73) as compared to the commercial Barik sample (0.65). The chemical composition of mainly fat (%) and protein (%) was higher and lower in commercial Barik sample, respectively, compared to P372 and P3043 Bengal gram flour. Wettability (contact angle) determined the solid–liquid interaction of Bengal gram flour, where the commercial Barik sample showed a higher contact angle compared to P372 and P3043. The flow properties of Bengal gram flour, that is, compressibility, shear, and dynamic measurements were analyzed using an FT4 powder rheometer. The results indicated better flow behavior of the two varieties P372 and P3043 compared to commercial Barik sample.Practical ApplicationsThe flow properties of Bengal gram flour are essential during the handling, processing, transportation, mixing, compression, and packaging. The consistent flow of flour without excessive dust generation and spillage during handling is of great concern in the food industry. The flow properties of flour characterize its behavior during handling, conveying and storage. It is crucial for the design of storage and conveying systems such as hopper and silos in order to maximize the use of discharge units to their design capacity to prevent expensive downstream handling problems. The practical application obtained from the comparative study would be useful to determine the effect of various environmental conditions on the flowability of Bengal gram flour. Thus, it provides critical factors in optimizing the processing, designing of equipment, hoppers, and silos used to produce Bengal gram flour in the food industry.

Durable Super-repellent Surfaces: From Solid–Liquid Interaction to Applications

ConspectusA super-repellent surface is a type of liquid-repellency material that allows for various liquid drops to bead up, roll off, or even bounce back. Known for its ability to remain dry, perform self-cleaning, and have a low adhesion, a super-repellent surface presents great advantages in a number of applications. These include antifogging, anti-icing, oil/water separation, and fluid drag reduction. To fend off the liquids or drops, super-repellent surfaces combine the merits of surface chemistry and physical structure. By taking advantage of a low surface energy to prevent liquid from spreading, the super-repellent surfaces utilize the micronano structure to provide a framework that confines the solid–liquid interactions. Compared to beading up the drop of water, the repellence of liquid with low surface tension requires the subtle design of surface structure to resist the wetting of liquids. However, the inherent instabilities of the fragile micronano structure of super-repellent surfaces and solid–liquid interactions further make the fabrication of super-repellent surfaces complex to withstand dynamic environments (friction or wear) during application. In addition, the transparency and thermal stability of super-repellent surfaces are also the restrictive factors in some special application scenarios. To solve these challenges, durable super-repellent surfaces that can repel various liquids, possess robust mechanical and thermal stability, and show high transparency have been explored extensively in recent years.In this Account, we systematically review our recent efforts to promote the super-repellent surfaces for real-world applications. Super-repellent surfaces that exhibit excellent resistance to various liquids, including liquids with low surface tension or high viscosity, were subtly designed and fabricated in some manner. Considering the stability of the wetting state at the solid–liquid interface, we established an evaluation system that includes highly curved surfaces and high Laplace-pressure conditions. To further perfect the wetting mechanism at the solid–liquid interactions, the dynamic wettability of super-repellent surfaces regulated by surface charge enrichment that was generated from solid–liquid interface separation was investigated. To resolve the bottleneck problem of the mechanical stability of super-repellent surfaces in real-world applications, a new decoupling material design mechanism was proposed, with a nanostructure that maintains water repellency and a microstructure providing durability. On the basis of the performance of the liquid-repellency, transparency, and mechanical and thermal stability of the super-repellent surfaces, a series of applications were demonstrated, such as microsphere synthesis, drop transportation and manipulation, and self-cleaning solar panels. Finally, a concise summary of this Account, including challenges and opportunities in super-repellent materials, has been provided. This research provides important guidance on solid–liquid interactions for the design of functional super-repellent surfaces and plays an important role in promoting large-scale industrial applications.

Roles of energy dissipation and asymmetric wettability in spontaneous imbibition dynamics in a nanochannel

HypothesisThe imbibition dynamics is controlled by energy dissipation mechanisms and influenced by asymmetric wettability in a nanochannel. We hypothesize that the imbibition dynamics can be described by a combined model of the Lucas–Washburn equation and the Cox-Voinov law considering velocity-dependent contact angles. MethodsMolecular dynamics simulations are utilized to investigate the imbibition dynamics. A wide range of wetting conditions is achieved via adjusting the liquid–solid interaction parameters, and the spontaneous imbibition processes are quantified and compared. FindingsThe critical condition for the occurrence of spontaneous imbibition is analyzed from a surface energy perspective. The analyses of energy conversion and dissipation indicate that the viscous dissipation is dominant during spontaneous imbibition. The classical Lucas-Washburn equation is modified with the Cox–Voinov law considering the effect of the dynamic contact angle and an effective equilibrium contact angle. We show that the proposed theory well captures the imbibition dynamics embodied in the growth of imbibition length as well as the transient interface shape and velocity for both the symmetric and asymmetric wetting conditions. In nanochannels with asymmetric wettability, the imbibition length difference between the sidewalls and interface oscillations increases with wetting disparity. Our findings deepen the understanding of imbibition dynamics on the nanoscale, and provide a theoretical reference for relevant applications.

Prediction of maximum spreading time of water droplet during impact onto hot surface beyond the Leidenfrost temperature

When a water droplet impacts on a heated surface in the film boiling regime, it will spread, recede, and finally bounce off from the heated surface. These unique liquid-solid interactions only occur at high surface temperatures. Our main objective in this research is to measure the maximum spreading and residence time of the droplet and the findings were compared to theory. We focused our study in the film boiling regime. Brass material was selected as the test surface and was polished until it became a mirror polished surface. The temperature range for this experimental work was between 100 °C up to 420 °C. Degassed and distilled water was used as the test liquid. The high speed video camera recorded the images at the rate of 10,000 frames per second (fps). As a result, it was found that the experimental value of maximum spreading and residence time agreed closely with the theoretical calculation. A new empirical formula that can be used to predict the maximum spreading time in the film boiling regime is also proposed.

Effect of the interface between magnetic particles and carrier liquids on magnetorheological properties and sedimentation of magnetorheological fluids: A molecular dynamics simulation and experimental insights

Theoretically, solid-liquid interactions play an important role in the rheological properties of magnetorheological (MR) fluids. In this study, interface molecular models of silicone oil (SO) and ionic liquid (IL)-based MR fluids are established. Based on the two kinds of interface models, molecular dynamics (MD) simulations directly revealed the adsorption behavior and the interaction between magnetic particle surfaces and SO or IL molecules. The main factor for the difference in the magnetorheological properties and sedimentation stability between the two MR fluids is revealed at the atomic scale, combining experimental results. The simulation results confirm that the nonbond attraction, wettability, and interface stability of the Fe/IL interface structure are higher than those of the Fe/SO structure. Moreover, compared to SO molecules, the evolution of the interface microstructure shows that IL molecules are more easily adsorbed on the surface of magnetic particles, resulting in the sedimentation stability of the IL MR fluid being reduced in 100 h. Meanwhile, the rheological properties are enhanced because of the stronger interface binding of Fe/ILs. Therefore, the interface strength between two phases and the aggregation of carrier liquid molecules on the surface of magnetic particles have a great influence on the magnetorheological properties and sedimentation stability of MR fluids.

Controlling impact behavior on superhydrophobic surfaces for droplets of nonionic surfactants by tailoring hydrophilic chain length

The behavior of high-speed droplets impacting on superhydrophobic surfaces plays an essential role in many daily applications. Adding surfactants is one excellent approach to improve droplet retention through enhancing the solid-liquid interface interaction. However, the regulating of the impact process has been rarely concerned about the effect of molecular structure on it. In our work, we study the impact behavior of nonionic surfactants Triton X (TX) on superhydrophobic surfaces by characterizing the diffusion rate of surfactant molecules and the receding contact angle and adhesion of surfactant solution on surfaces. We reveal that droplets of TX surfactant solution can deposit better on superhydrophobic surfaces as hydrophilic (ethylene oxide, EO) chain length increasing, which is mainly attributed by the faster diffusion speed towards the newly formed interface during the spreading phase, leading to better wettability transition and larger pinning area on the substrate. Our work promotes the understanding of the mechanism that controls the impact behavior of droplets of surfactant by adjusting the EO chain length, which provides an effective strategy to control droplet deposition on superhydrophobic surfaces.

Destabilization of Immersed Dense Granular Material Submitted to Localized Fluidization: An Experimental and Numerical Study

An alternative experimental approach and a numerical analysis for the study of destabilization by localized fluidization of an immersed dense granular material are presented. To visualize the evolutions of the internal structure of the granular medium, the hydrogel beads, composed of about 99% of water and having substantially the same refraction indexes, are used as solid phase. A LED lighting system is used in place of a laser lighting system. As a result, the optical access restriction of porous structure is removed. A real economic alternative for the experimental study of fluid-grain coupling during destabilization by localized fluidization of a granular material is created. The experimental phenomenology presented in the literature is verified: the system passes successively through three different stationary regimes: static regime, fluidized cavity regime, and fluidized chimney regime. Some restrictions of using hydrogel beads as particles in the study of liquid-solid interaction are also discussed.

Seismic Response considering LSI for Steel Rectangular Water Purification Structures

In this paper, the finite element method (FEM) is used to analyze the dynamic response of steel rectangular water purification structure (SRWPS) considering liquid-solid interaction (LSI) in the water treatment project of the Zhuanglang Water Supply Company in Zhuanglang County. The near-field non-pulse Friuli wave, the near-field pulse Chi-Chi wave, the far-field long-period TOM wave and the Lanzhou wave are inputted along the x-direction of SRWPS, and LSI dynamics of the structure are studied under different earthquakes. The displacement, stress and liquid sloshing laws of SRWPS are obtained. SRWPS exhibits different displacement and stress responses under the action of four different seismic waves. The liquid sloshing wave height is only sensitive to long-field long-period waves. However, the structural deformation and liquid sloshing wave height are more sensitive to the Lanzhou wave. The structural deformation nephogram shows that the structural deformation of SRWPS is located in the middle of the non-hole partition, and the deformation between the open partition and the wallboard is small.

Laser texturing of a St. Jude Medical RegentTM mechanical heart valve prosthesis: the proof of concept.

The liquid-solid interactions have attracted broad interest since solid surfaces can either repel or attract fluids, configuring a wide spectrum of wetting states (from superhydrophilicity to superhydrophobicity). Since the blood-artificial surface interaction of bileaflet mechanical heart valves essentially represents a liquid-solid interaction, we analysed the thrombogenicity of mechanical heart valve prostheses from innovative perspectives. The aim of the present study was to modify the surface wettability of standard St. Jude Medical Regent™ occluders. Four pyrolytic carbon occluders were irradiated by means of ultra-short pulse laser, to create 4 different nanotextures (A-D), the essential prerequisite to achieve superhydrophobicity. The static surface wettability of the occluders was qualified by the contact angle (θ) of 2 µl of purified water, using the sessile drop technique. The angle formed between the liquid-solid and the liquid-vapour interface was the contact angle and was obtained by analysing the droplet images captured by a camera. The morphology of the occluders was characterized and analysed by a scanning electron microscope at different magnifications. The scanning electron microscope analysis of the textures revealed 2 different configurations of the pillars since A and B showed well-rounded shaped tops and C and D flat tops. The measured highest contact angles were comprised between 108.1° and 112.7°, reflecting an improved hydrophobicity of the occluders. All the textures exhibited, to different extents, an orientation (horizontal or vertical), which was strictly related to the observed anisotropy. In this very early phase of our research, we were able to demonstrate that the intrinsic wettability of pyrolytic carbon occluders can be permanently modified, increasing the water repellency.

The electrosorptive response of a carbon nanotube flow-through electrode in aqueous systems

The capture and recovery of valuable products from wastewater and/or bio-broths is one of today’s industrial challenges. Potential-controlled chromatography is a versatile solution to separate charged or polarized target species from aqueous systems. This capacitive flow-through technique combines the advantages of capacitive desalination and ion-exchange chromatography. The separation principle is controlled by system-dependent solid–liquid interaction mechanisms at the potential-controlled interface and characterized by the electrochemical double layer (EDL) formation. We conducted new experiments on the process- and environment-dependent surface effects in aqueous systems to better understand electrically driven processes inside a macroporous multi-walled carbon nanotube electrode. Here, the column and current response are investigated as a function of flow rate, as well as mobile phase pH-value, composition and concentration. Due to the strong water affinity of the material, water ions significantly co-define the EDL. The current response depends particularly on the ion properties and concentration. The use of electrolytes promotes capacitive and faradaic current and diminishes pH-deviation occurring at a negative potential. The effective range of the EDL decreases with increasing shear forces. Finally, a better performance for electrosorbing maleic acid is guaranteed at higher electrolyte concentration and low flow rate. This paper successfully addresses research gaps in potential-dependent effects that occur in multi-walled carbon nanotube electrodes.

Fluorinated Metal-Organic Coatings with Selective Wettability.

Surface chemistry is a major factor that determines the wettability of materials, and devising broadly applicable coating strategies that afford tunable and selective surface properties required for next-generation materials remains a challenge. Herein, we report fluorinated metal-organic coatings that display water-wetting and oil-repelling characteristics, a wetting phenomenon different from responsive wetting induced by external stimuli. We demonstrate this selective wettability with a library of metal-organic coatings using catechol-based coordination and silanization (both fluorinated and fluorine-free), enabling sensing through interfacial reconfigurations in both gaseous and liquid environments, and establish a correlation between the coating wettability and polarity of the liquids. This selective wetting performance is substrate-independent, spontaneous, durable, and reversible and occurs over a range of polar and nonpolar liquids (60 studied). These results provide insight into advanced liquid-solid interactions and a pathway toward tuning interfacial affinities and realizing robust, selective superwettability according to the surrounding conditions.

Effects of Layering and Supporting Substrate on Liquid Slip at the Single-Layer Graphene Interface

Understanding modulation of liquid molecule slippage along graphene surfaces is crucial for many promising applications of two-dimensional materials, such as in sensors, nanofluidic devices, and biological systems. Here, we use force measurements by atomic force microscopy (AFM) to directly measure hydrodynamic, solvation, and frictional forces along the graphene plane in seven liquids. The results show that the greater slip lengths correlate with the interfacial ordering of the liquid molecules, which suggests that the ordering of the liquid forming multiple layers promotes slip. This phenomenon appears to be more relevant than solely the wetting behavior of graphene or the solid-liquid interaction energy, as traditionally assumed. Furthermore, the slip boundary condition of the liquids along the graphene plane is sensitive to the substrate underneath graphene, indicating that the underlying substrate affects graphene's interaction with the liquid molecules. Because interfacial slip can have prominent consequences on the pressure drop, on electrical and diffusive transport through nanochannels, and on lubrication, this work can inspire innovation in many applications through the modulation of the substrate underneath graphene and of the interfacial ordering of the liquid.

An analysis of major scientific problems and research paths of Gulong shale oil in Daqing Oilfield, NE China

After the preliminary basic research on the problems encountered during the production period of Gulong shale oil in the Songliao Basin, NE China, and the scientific exploration, the special characteristics of Gulong shale oil in terms of reservoir space, phase distribution, flow pattern, and mineral evolution are proposed. The main results are as follows : (1) The source of organic matter, mechanism of hydrocarbon generation and expulsion, and key factors affecting shale oil abundance; (2) The types and structural characteristics of the reservoir and their contribution to porosity and permeability; (3) The mineral origin and evolution of minerals and their influence on reservoir availability, sensitivity, and compressibility; (4) The rock mechanical characteristics and fracture propagation law of Gulong shale; (5) The shale oil products, phase change law and main control factors of adsorption and desorption conversion of Gulong shale oil; (6) The mechanism of shale oil-liquid, solid-liquid gas interaction and enhanced oil recovery. Three key research suggestions are proposed to realize the large-scale economic utilization of the Gulong shale oil as follows: (1) Deepen research on the mechanism of oil and gas generation and discharge, storage and transportation, to guide the selection of geological sweet spots of shale oil; (2) Deepen research on the compressibility and fracture initiation mechanism to support the selection of engineering sweet spots and optimization of engineering design; (3) Deepen research on the fluid interaction mechanism under reservoir conditions, os us to guide the optimization of development schemes and the selection of EOR technologies. A successful development of Gulong shale oil requires global experts and scholars to contribute multidisciplinary innovative ideas and technical ideas to solve production problems.

CONCEPTUALIZATION, THERMAL ANALYSIS, AND MANUFACTURING OF NANO-TEXTURED MICRO-STRUCTURED SURFACES FOR ENHANCED CONDENSATION HEAT TRANSFER

In the present study, nano-micro-structured surfaces have been systematically designed and manufactured in order to generate controlled dropwise condensation mode for enhanced heat transfer during phase-change from vapor to liquid. The conceptualization of micro-structures was conducted by using thermal modelling of an individ-ual droplet pinned at a single micro-hexagonal cavity. By varying droplet radius, resulting contact angles and geo-metric dimensions of micro-structure, threshold values have been determined for the later manufacturing process. According to the calculations for instance at contact angles of 150°, a subcooling of 1 K and a maximum droplet radius of 100 µm, the edge length and the depth of the micro-structures should be kept below 50 µm and 25 µm, respectively. Ensuring these parameters, a roughly 100 % larger heat transfer coefficient would result compared to that predicted by the classical Nusselt theory for filmwise condensation. Taking into account the mathematical analysis, laser ablation technique was adopted on 7075 aluminum samples to emboss hexagonal structures with respect to the predicted dimensions. After this step, the samples were electrochemically etched in order to achieve contact angles of more than 150° to ensure superhydrophobic solid-liquid interaction at the surface. Measurements with a high-precision microscope show that most of the structure dimensions and geometric shape were precisely manufactured. The Tensiometer results disclosed that the surface topography at all samples exhibit contact angles larger than 150° for a sessile droplet with a radius of 100 µm pinned on an individual micro-hexagon.

Virtual Experiments of Particle Mixing Process with the SPH-DEM Model.

Particle mixing process is critical for the design and quality control of concrete and composite production. This paper develops an algorithm to simulate the high-shear mixing process of a granular flow containing a high proportion of solid particles mixed in a liquid. DEM is employed to simulate solid particle interactions; whereas SPH is implemented to simulate the liquid particles. The two-way coupling force between SPH and DEM particles is used to evaluate the solid-liquid interaction of a multi-phase flow. Using Darcy’s Law, this paper evaluates the coupling force as a function of local mixture porosity. After the model is verified by two benchmark case studies, i.e., a solid particle moving in a liquid and fluid flowing through a porous medium, this method is applied to a high shear mixing problem of two types of solid particles mixed in a viscous liquid by a four-bladed mixer. A homogeneity metric is introduced to characterize the mixing quality of the particulate mixture. The virtual experiments with the present algorithm show that adding more liquid or increasing liquid viscosity slows down the mixing process for a high solid load mix. Although the solid particles can be mixed well eventually, the liquid distribution is not homogeneous, especially when the viscosity of liquid is low. The present SPH-DEM model is versatile and suitable for virtual experiments of particle mixing process with different blades, solid particle densities and sizes, and liquid binders, and thus can expedite the design and development of concrete materials and particulate composites.

Atomistic Insight into the Effects of Depositional Nanoparticle on Nanoscale Liquid Film Evaporation.

Nanoscale liquid film evaporation plays an essential role in many engineering applications. This study carries out molecular dynamics simulations on the effects of the depositional nanoparticle's wettability and volume in base fluid on the evaporation process to understand how the depositional nanoparticle affects the evaporation heat transfer. Increasing the nanoparticle's wettability can enhance the evaporation heat transfer process, and the enhancement effect of the hydrophobic surface is more remarkable than that of the hydrophilic surface. This because the increasing wettability causes more significant solid-liquid interaction. However, the potential energy of argon atoms at the liquid-vapor interface is almost unaffected by wettability. Moreover, when the depositional nanoparticle locates below the free liquid film, increasing the nanoparticle volume has a better heat transfer performance. As the volume increases, the heat transfer through the nanoparticle becomes more obvious, which effectively enhances the heat transfer at the solid-liquid interface and the liquid-vapor interface. The latent heat of phase change at the liquid-vapor interface is almost unchanged so that the evaporation can be enhanced. This research provides an understanding of the effects of depositional nanoparticles on nanoscale evaporation, which can impact several engineering applications, including devices' cooling and fluid transport.

Characterizing Solid–Liquid Interactions in a Mesoporous Catalyst Support Using Variable-Temperature Fast Field Cycling NMR

Variable-temperature fast field cycling NMR measurements are used to probe the surface dynamics of different liquids imbibed within a γ-alumina catalyst support material. The imbibed liquids were g...

A modified smoothed particle hydrodynamics for modelling fluid-fracture interaction at mesoscale

This study presents a modified smoothed particle hydrodynamics (SPH) for modelling liquid-fracture interaction at mesoscale. In this approach, an interparticle force that can provide repulsive force in the short-range and attractive force in the long-range is introduced to model the liquid–liquid and liquid–solid interactions. This interparticle force prevents the SPH particles from clustering and having high compressibility when under high pressure. The formation of a droplet, different contact angles and realistic compressibility of liquid are achieved to demonstrate the capability of the proposed SPH based approach. Moreover, the Drucker–Prager model and the Grady–Kipp damage model are implemented in SPH to describe the solid failure. The results show that the mixed-mode can reproduce the fracture patterns of available Brazilian disc tests on rock-like 3D printed material. Finally, a process of hydraulic fracturing is simulated at mesoscale. The results demonstrate that the proposed SPH framework has potential in modelling liquid-fracture interaction with the consideration of interfacial effects at mesoscale and solid fracture.

Nano-confinement effects on liquid pressure

In this study, molecular dynamics simulations are performed to estimate the equilibrium pressure of liquid confined in nanopores. The simulations show that pressure is highly sensitive to the pore size and can significantly change from absolute positive to absolute negative values for a very small (0.1 nm) change in the pore size. The contribution from the solid–liquid interaction always dominates the pressure in the first liquid layer adjacent to the surface and the sensitiveness of pressure on the pore size is dependent on the atom distribution in the liquid layers. A surface influence number S is introduced to quantitatively characterize the degree of the confinement. At constant system temperature, the S number decreases with increasing pore size based on a power-law function. In nanopores with large S number, the pore liquid pressure is found to be independent of bulk liquid pressure, whereas in nanopores with small S number, the pore pressure is dependent and increases with bulk pressure.

Simulation of liquid flow transport in nanoscale porous media using lattice Boltzmann method

Clarifying the confined liquid flow in nanoscale porous media is crucial for many science and engineering applications, such as shale/tight oil recovery. However, most of the investigations are focused on the single pore and the uniform wet, and there are few effective nanoscale pore-scale simulation methods. In this paper, we comprehensively study the confined water flow in shale porous media from the theoretical analysis to a new nanoscale lattice Boltzmann method (LBM). The nanoscale effects of the slip boundary and the varying interfacial water viscosity caused by the solid-liquid molecular interactions are considered. Additionally, the water flowing in shale porous media coupling different transport mechanisms in the water-wetting inorganic and oil-wetting organic media is simulated and discussed. The results show that the water flow behaviors obtained by (LB) simulations fit well with that calculated by the theoretical analysis. Then, the controllable nanoscale effects are successfully brought into LB simulation. Additionally, the nanoscale effects of the slip boundary and the interfacial fluid viscosity have a great impact on the water flow capacity, and the confined water flow behaviors are sensitive to heterogeneous wettability and pore size.