Conical Channel Research Articles

IMPROVEMENT OF THE SECURITY SYSTEM AGAINST POLLUTANTS USING A CIRCULAR CONE

This study focuses on the improvement of a security system against the pollutants dispersing from Industrial chimneys. In order to simulate the system, we study numerically a turbulent flow generated by a heated open cone at the extremities. Different control parameters were used to improve the thermal and dynamic behavior of the considered flow. In this study, the interaction of pollutants with its surrounding environment simulated by the cone walls was investigated. This study was focused on convection, which is natural, turbulent, steady, 2-D, incompressible flow passing through a vertical conical channel with a heated source at the center of the cone inlet that performed uniform heating at a constant temperature. The interior of the conical wall channel was reheated via the thermal radiation emitted by the hot source. The studied system was mathematically presented by the continuity, Navier stokes, energy and K-epsilon equations. The computational fluid dynamics analysisand ANSYS-FLUENT software were used. The optimal cone can provide further control of the pollutants velocity at the exit. The thermal and dynamic profiles exhibitedgood stability and homogeneity at the cone exit.

Conical focusing: mechanism for singular jetting from collapsing drop-impact craters

Fast microjets can emerge out of liquid pools from the rebounding of drop-impact craters, or when a bubble bursts at its surface. The fastest jets are the narrowest and are a source of aerosols both from the ocean and from a glass of champagne, of importance to climate and the olfactory senses. The most singular jets, which we observe experimentally at a maximum velocity of $137\pm 4\ {\rm m}\ {\rm s}^{-1}$ and a diameter of $12\ \mathrm {\mu }{\rm m}$ , under reduced ambient pressure, are produced when a small dimple forms at the crater bottom and rebounds without pinching off a small bubble. The radial collapse and rebounding of this dimple is purely inertial, but highly sensitive to initial conditions. High-resolution numerical simulations reveal a new focusing mechanism, which drives the fastest jet within a converging conical channel, where an entrained air sheet provides effective slip at the outer boundary of the conically converging flow into the jet. This configuration bypasses any viscous cutoff of the jetting speed and explains the extreme sensitivity to initial conditions observed in detailed experiments of the phenomenon.

Fick-Jacobs description and first passage dynamics for diffusion in a channel under stochastic resetting.

The transport of particles through channels is of paramount importance in physics, chemistry, and surface science due to its broad real world applications. Much insight can be gained by observing the transition paths of a particle through a channel and collecting statistics on the lifetimes in the channel or the escape probabilities from the channel. In this paper, we consider the diffusive transport through a narrow conical channel of a Brownian particle subject to intermittent dynamics, namely, stochastic resetting. As such, resetting brings the particle back to a desired location from where it resumes its diffusive phase. To this end, we extend the Fick-Jacobs theory of channel-facilitated diffusive transport to resetting-induced transport. Exact expressions for the conditional mean first passage times, escape probabilities, and the total average lifetime in the channel are obtained, and their behavior as a function of the resetting rate is highlighted. It is shown that resetting can expedite the transport through the channel-rigorous constraints for such conditions are then illustrated. Furthermore, we observe that a carefully chosen resetting rate can render the average lifetime of the particle inside the channel minimal. Interestingly, the optimal rate undergoes continuous and discontinuous transitions as some relevant system parameters are varied. The validity of our one-dimensional analysis and the corresponding theoretical predictions is supported by three-dimensional Brownian dynamics simulations. We thus believe that resetting can be useful to facilitate particle transport across biological membranes-a phenomenon that can spearhead further theoretical and experimental studies.

Unveiling the capabilities of bipolar conical channels in neuromorphic iontronics.

Conical channels filled with an aqueous electrolyte have been proposed as promising candidates for iontronic neuromorphic circuits. This is facilitated by a novel analytical model for the internal channel dynamics [T. M. Kamsma, W. Q. Boon, T. ter Rele, C. Spitoni and R. van Roij, Phys. Rev. Lett., 2023, 130(26), 268401], the relative ease of fabrication of conical channels, and the wide range of achievable memory retention times by varying the channel lengths. In this work, we demonstrate that the analytical model for conical channels can be generalized to channels with an inhomogeneous surface charge distribution, which we predict to exhibit significantly stronger current rectification and more pronounced memristive properties in the case of bipolar channels, i.e. channels where the tip and base carry a surface charge of opposite sign. Additionally, we show that the use of bipolar conical channels in a previously proposed iontronic circuit features hallmarks of neuronal communication, such as all-or-none action potentials and spike train generation. Bipolar channels allow, however, for circuit parameters in the range of their biological analogues, and exhibit membrane potentials that match well with biological mammalian action potentials, further supporting their potential biocompatibility.

A study of the aerodynamic properties of cotton fiber in the confusor tube of a rotor spinning machine

In this article, the movement of fibers in the air channel and the rotor in the rotor spinning machine was studied. In the experimental work, the uniformity and stability of the velocity field of each channel for moving fibers in an aerodynamic device were checked. In this case, the airflow speed was changed from 5 m/s to 30 m/s. Also, differential equations of motion along the OX and OY axes were created taking into account the air resistance. When determining the movement of fibers in a conical channel, the total speed was divided into components, constant values were found, and general equations of motion were derived.

Study of the influence of the output surface of the confusor inside the adapter on the location of fibers in the yarn in a rotor-spinning machine

In the article, the influence of the confusor inside the adapter on the output surface of the rotor-spinning machine on the location of the fibers in the yarn was studied. The properties of carding sliver for yarn production were investigated. In the experimental work, the uniformity and stability of the velocity field of each channel for moving fibers in an aerodynamic device were checked. Airflow was carried out at a speed of 20 m/s. During the research, 20-tex yarns were produced in 3 different samples by changing the output surfaces of the confusor inside the adapter S1=19.6 mm2, S2=12.6 mm2, S3=7.1 mm2 in the rotor-spinning machine. The cross-section and length of the produced yarns were examined under a microscope. The location of the fibers in the conical channel in the yarn was studied.

Bioinspired topological design with unidirectional water transfer for efficient atmospheric water harvesting

A sodium alginate-based hemisphere with centripetal conical channels loaded with CaCl2 crystals and coated with a photothermal layer was designed for moisture absorption, unidirectional water transfer and solar-driven water evaporation.

First-passage times in conical varying-width channels biased by a transverse gravitational force: Comparison of analytical and numerical results.

We study the crossing time statistic of diffusing point particles between the two ends of expanding and narrowing two-dimensional conical channels under a transverse external gravitational field. The theoretical expression for the mean first-passage time for such a system is derived under the assumption that the axial diffusion in a two-dimensional channel of smoothly varying geometry can be approximately described as a one-dimensional diffusion in an entropic potential with position-dependent effective diffusivity in terms of the modified Fick-Jacobs equation. We analyze the channel crossing dynamics in terms of the mean first-passage time, combining our analytical results with extensive two-dimensional Brownian dynamics simulations, allowing us to find the range of applicability of the one-dimensional approximation. We find that the effective particle diffusivity decreases with increasing amplitude of the external potential. Remarkably, the mean first-passage time for crossing the channel is shown to assume a minimum at finite values of the potential amplitude.

Ion Current Rectification and Long-Range Interference in Conical Silicon Micropores.

Fluidic devices exhibiting ion current rectification (ICR), or ionic diodes, are of broad interest for applications including desalination, energy harvesting, and sensing, among others. For such applications a large conductance is desirable, which can be achieved by simultaneously using thin membranes and wide pores. In this paper we demonstrate ICR in micrometer sized conical channels in a thin silicon membrane with pore diameters comparable to the membrane thickness but both much larger than the electrolyte screening length. We show that for these pores the entrance resistance is key not only to Ohmic conductance around 0 V but also for understanding ICR, both of which we measure experimentally and capture within a single analytic theoretical framework. The only fit parameter in this theory is the membrane surface potential, for which we find that it is voltage dependent and its value is excessively large compared to the literature. From this we infer that surface charge outside the pore strongly contributes to the observed Ohmic conductance and rectification by a different extent. We experimentally verify this hypothesis in a small array of pores and find that ICR vanishes due to pore-pore interactions mediated through the membrane surface, while Ohmic conductance around 0 V remains unaffected. We find that the pore-pore interaction for ICR is set by a long-ranged decay of the concentration which explains the surprising finding that the ICR vanishes for even a sparsely populated array with a pore-pore spacing as large as 7 μm.

Driven translocation of a semiflexible polymer through a conical channel in the presence of attractive surface interactions

We study the translocation of a semiflexible polymer through a conical channel with attractive surface interactions and a driving force which varies spatially inside the channel. Using the results of the translocation dynamics of a flexible polymer through an extended channel as control, we first show that the asymmetric shape of the channel gives rise to non-monotonic features in the total translocation time as a function of the apex angle of the channel. The waiting time distributions of individual monomer beads inside the channel show unique features strongly dependent on the driving force and the surface interactions. Polymer stiffness results in longer translocation times for all angles of the channel. Further, non-monotonic features in the translocation time as a function of the channel angle changes substantially as the polymer becomes stiffer, which is reflected in the changing features of the waiting time distributions. We construct a free energy description of the system incorporating entropic and energetic contributions in the low force regime to explain the simulation results.

Synergistic effect of urchin-like spherical Cu-based catalyst for enhanced dimethyl oxalate hydrogenation capacity

An urchin-like spherical Cu-based catalyst (Cu/KCC-U) with dendritic fibrous KCC-1 as support was developed using appropriate urea-assisted precipitation approach. Benefit from the radial conical channels, the dispersion of copper nanoparticles and the interaction between copper and support were greatly improved. As a result, the Cu/KCC-U catalyst owned plenty of highly dispersed Cu nanoparticles (4.10 nm), and the Cu+ ratio reached 77.38 %. The urchin-like spherical Cu/KCC-U catalyst, arising from the synergy of highly dispersed active copper species with 77.38 % Cu+ ratio and radial conical channel structure, demonstrated superior catalytic hydrogenation capacity, higher ethanol selectivity, and lower by-product selectivity when compared with reference Cu/KCC-I and Cu/SiO2-U catalysts. More crucially, the intimate interaction between copper species and KCC-1 support fibers enables the stable presence of Cu+ species in the hydrogenation reaction, resulting in the ultra-high stability of the catalyst. This urchin-like Cu/KCC-U provided a new perspective for designing and developing efficient hydrogenation catalysts with great selectivity and stability.

Pressure-sensitive ion conduction in a conical channel: Optimal pressure and geometry

Using both analytic and numerical analyses of the Poisson–Nernst–Planck equations, we theoretically investigate the electric conductivity of a conical channel which, in accordance with recent experiments, exhibits a strong non-linear pressure dependence. This mechanosensitive diodic behavior stems from the pressure-sensitive build-up or depletion of salt in the pore. From our analytic results, we find that the optimal geometry for this diodic behavior strongly depends on the flow rate with the ideal ratio of tip-to-base-radii being equal to 0.22 at zero-flow. With increased flow, this optimal ratio becomes smaller and, simultaneously, the diodic performance becomes weaker. Consequently an optimal diode is obtained at zero-flow, which is realized by applying a pressure drop that is proportional to the applied potential and to the inverse square of the tip radius, thereby countering electro-osmotic flow. When the applied pressure deviates from this ideal pressure drop the diodic performance falls sharply, explaining the dramatic mechanosensitivity observed in experiments.

Design and Implementation of an Additively Manufactured Reactor Concept for the Catalytic Methanation

The methanation process is discussed as one way to chemically store renewable energy in a future energy system. An important criterion for its application is the availability of compact, low-cost reactor concepts with high conversion rates for decentralized use where the renewable energy is produced. Current research focuses on the maximization of the methane yield through improved temperature control of the exothermic reaction, which attempts to avoid both kinetic and thermodynamic limitations. In this context, traditional manufacturing methods limit the design options of the reactor and thus the temperature control possibilities. The use of additive manufacturing methods removes this restriction and creates new freedom in the design process. This paper formulates the requirements for a novel methanation reactor and presents their implementation to a highly innovative reactor concept called ‘ADDmeth’. By using a conical reaction channel expanding from Ø 8 to 32 mm, three twisted, expanding heat pipes (Ø 8 mm in evaporation zone, Ø 12 mm in condenser zone) and a lattice structure for feed gas preheating and mechanical stabilization of the reactor, the design explicitly exploits the advantages of additive manufacturing. The reactor is very compact with a specific mass of 0.36 kg/kW and has a high share of functional volume of 52%. The reactor development was accompanied by tensile tests of additively manufactured samples with the used material 1.4404 (316 L), strength calculations for stability verification and feasibility studies on the printability of fine structures. Ultimate tensile strengths of up to 750 N/mm2 (at room temperature) and sufficiently high safety factors of the pressure-loaded structures against yielding were determined. Finally, the paper presents the manufactured bench-scale reactor ADDmeth1 and its implementation.

Determination of an implantation area for interstitial fluid extraction in cows and feasibility of adapted microneedles

We present a preliminary study of a wearable system to monitor biomarkers for dairy and suckling cattle. Finding the optimal location on the cow body (ears) and designing the adapted microneedles to reach the interstitial fluids underneath the cow skin are the two points addressed here. For the selection of the location, 4 breeds of suckling cows (Aubrac, Charolaise, Limousine, Salers) and 3 breeds of dairy cows (Abondance, Montbéliarde, Holstein) were chosen. Measurements of the thickness of the ear tissues were conducted on three areas of the ear (top, apex and base of the pinna), on the external and internal sides. Results show that the apex of the pinna, external side, is the best area for microneedle implantation with an implantation window of 1403 ± 589 μm (DeepDe), considering all breeds. To reach this implantation window located between the stratum corneum and the cartilage, the microneedle has to pass through 1323 ± 404 μm of tissues (SupDe), considering all breeds. From these results, a microneedle design was made on SolidWorks. With a conical shape 2.89 mm in height and a conical channel 300 μm in diameter (at the tip of the microneedle), the model was made using 3D printing. The resulting microneedles respect the SolidWorks design with fair accuracy. They were connected to a microfluidic channel for sampling or releasing fluids. • Structure of the cow ear tissues depends on side/area of the pinna and cow breed. • The apex of the pinna is the most convenient location for microneedle implantation. • Microneedles are a promising tool for the extraction of interstitial fluids. • 3D printing is a fast and inexpensive way to prototype microneedles.

A smart microhydrogel membrane sensor realized by pipette tip

In this paper, we describe a simple and practical way to prepare hydrogel membranes in a conical channel (pipette tip). We used a pipette to create a gas pressure difference on both sides of the gel precursor, which drove the gel precursor to move in the pipette tip. During movement, the shape of the hydrogel precursor gradually becomes thinner as the radius of the tapered channel becomes larger. We use this principle to realize the highly controllable preparation of the hydrogel membrane structure (130 μm at its thinnest). Moreover, we fabricated a hydrogel membrane sensor in one step by implanting smart molecules in the hydrogel, which achieved rapid and sensitive detection of 0.5 μM–500 mM potassium ions. This method of preparing the hydrogel membrane sensor does not rely on professional membrane production equipment and complex molecular design processes, has high gel utilization and simple and controllable membrane thickness, and has a wide range of application value in the field of intelligent hydrogel-based analysis technology.

Effect of Conical Spiral Flow Channel and Impeller Parameters on Flow Field and Hemolysis Performance of an Axial Magnetic Blood Pump

For a blood pump, the blood flow channel and impeller parameters directly affect the performance of the pump and the resulting blood circulation. The flow channel in particular has a great impact on the hydraulic performance of the pump (e.g., flow and pressure), which directly determines the overall performance of the blood pump. Traditional bearing-supported blood pumps can cause mechanical damage to blood cells, leading to hemolysis and thrombosis. In this study, therefore, we designed a conical spiral axial blood pump with magnetic levitation. The blood pump was supported by electrodynamic bearings in the radial direction and electromagnetic bearings in the axial direction. The impeller and the front and rear hubs were integrated to minimize blood stagnation and reduce the formation of thrombosis. The hub had a conical spiral flow channel design, which not only reduced the size of the impeller but also increased blood flow and pressure while meeting the design requirements. Computational fluid dynamics (CFD) analysis was used to analyze the flow field of the axial blood pump, a power function model was used to establish a hemolysis prediction model, and the particle tracking method was used to obtain the flow trajectories of individual blood cells, thereby predicting hemolysis-related performance of the blood pump. The simulation results showed that the main high shear stress area in the blood pump was located in the impeller inlet and the clearance between the top of the impeller and the inner chamber of the blood pump. When the hub taper angle of the blood pump was 0.72° and the clearance was 0.3 mm, the average hemolysis prediction value was 0.00216. This prediction value was smaller than that of traditional axial blood pumps. These findings can provide an important reference for the structural design of axial blood pumps and for reducing the hemolysis prediction value.

Mini-Hydropower Plant Based on Lenyov Hydrobelt and Volume-Sectional Hydraulic Engine

The use of the energy of small watercourses with the help of small hydropower plants is one of the promising directions for the development of renewable energy. This article presents the designs of two different hydraulic engines, each of which has its own advantage. Therefore, the task of calculating the real parameters of the design of a mini-hydropower plant based on Lenyov hydrobelt has been solved. Theoretical calculations were validated numerically by the finite volume method and computational fluid dynamics modeling; both methods gave similar results. According to the results of calculations, this design based on the Lenyov hydrobelt with the capacity of 16 kW is advisable to place in a river with a flow velocity of at least 4.5 m/s. The article also presents an alternative type of developed mini-hydropower plant, -a volume-sectional hydraulic engine. The proposed rotary-type positive displacement hydraulic engine can operate at low pressure on a flat surface. The advantage of the hydraulic engine is the sectional operation of several working chambers. It was established that a high water velocity and a large volume of passing water was not required. The total force acting in the hydraulic engine is 5430.19 N. Due to the use of conical inlet channels, the water flow velocity was increased and the water flow became directional. The frequency of rotation of the hydraulic engine shaft at a river flow velocity of 4 m/s was 60.43 rpm. The received power in these modes was 22.25 kW.

Vertical CMOS nanotransistors with a conical channel for three-dimensional integrated circuits

Vertical CMOS nanotransistors with a conical channel for three-dimensional integrated circuits

The characters exploration of a piezoelectric pump with fishtail-shaped bluffbody

This paper focuses on a new structure in the valveless piezoelectric pump, which has a combination structure of the conical flow channel and two fishtail-shaped bluffbodies in the chamber of the pump. The fishtail-shaped bluffbody is inspired by the shape of the swimming fish to diminish the backflow and optimize the performance of the pump. The performance is studied by changing the shape and size of the inlet and outlet, the bluff bodies’ height and the space between two bluff bodies. The results show that the 3 mm × 3 mm square inlet, 3 mm diameter round outlet, 3 mm height of bluffbodies, 6.8 mm pitch of bluffbodies has a best performance in all 10 prototypes, which implements a maximum flow rate of 87.5 ml/min at 170 V 40 Hz with a noise of 42.6 dB. This study makes a preliminary investigation and theoretical explanation for the subsequent optimization of this structure, improved the performance of the valveless piezoelectric pump, broaden the thinking of the design for the bluffbody for better performance of the valveless piezoelectric pump.

Anisotropic confinement of chromophores induces second-order nonlinear optics in a nanoporous photonic metamaterial.

Second-order nonlinear optics is the base for a large variety of devices aimed at the active manipulation of light. However, physical principles restrict its occurrence to non-centrosymmetric, anisotropic matter. This significantly limits the number of base materials exhibiting nonlinear optics. Here, we show that embedding chromophores in an array of conical channels 13 nm across in monolithic silica results in mesoscopic anisotropic matter and thus in a hybrid material showing second-harmonic generation. This nonlinear optics is compared to the one achieved in corona-poled polymer films containing the identical chromophores. It originates in the confinement-induced orientational order of the elongated guest molecules in the nanochannels. This leads to a non-centrosymmetric dipolar order and hence to a nonlinear light-matter interaction on the sub-wavelength, single-pore scale. Our study demonstrates that the advent of large-scale, self-organized nanoporosity in monolithic solids along with the confinement-controllable orientational order of chromophores at the single-pore scale provides a reliable and accessible tool to design materials with a nonlinear meta-optics.