Channel Shape Research Articles

Phase-field modeling of ductile fracture in bioinspired interfaces with dissipative structures

Intrinsic toughening, which occurs during ductile fracture and is motivated by plasticity, plays an important role in the industrial design of biomimetic composites. The interface structure in biomimetic composites can serve as a source of energy dissipation and stress relaxation, thereby achieving the goal of toughening. A new ductile fracture mechanism is proposed considering the influence of accumulated plastic deformation on local fracture toughness in a ductile phase-field model. The inducement to control the toughening mechanism is local energy dissipation, and the possible arrangement and shape of the dissipative structure are designed to capture the corresponding interface toughening mechanism. The channel structures of the barnacle substrate provide great inspiration for the structural toughening of the interface. The toughening mechanisms of weak interfaces are further explored by 3D printing structure specimens. The results indicate that the form of the R-curve is like a mixture of local J shaped and Γ shaped R-curves, which can also be called a periodic alternating mode. The J shaped R-curve represents the dissipation mechanism of the channel shape, while the Γ shaped R-curve represents the periodic crack arrest caused by local deformation of the channel.

Radiation Patterns Formed by Sapphire Capillary Needles with Different Shapes of Internal Channels

Radiation Patterns Formed by Sapphire Capillary Needles with Different Shapes of Internal Channels

Modeling and Dynamic Analysis of Fish Robot with Soft Fluidic Actuation

A biomimetic robotic fish tailored for environmental monitoring and hydrographic exploration is examined in this study. Traditional fish robots, driven by tail oscillations, often grapple with constrained maneuverability in a single plane. This article focuses on mitigating these limitations through an exploration of the dynamic behavior of a bioinspired soft robotic fish. Unlike prior designs that employed similar actuators for the robot's tail, which either lacked the ability for out-of-plane motion or relied on other propulsion systems, the single propulsion design proposed in our model enables movement along three-dimensional trajectories, leading to improved efficiency and maneuverability due to tail oscillation dynamics. The proposed design integrates strategically positioned nozzles for out-of-plane movements, alongside parallel fluid channels on the tail's neutral plate. Actuation is achieved by manipulating the internal fluid pressure within these channels. To precisely model tail deflection, we introduce a novel method utilizing Euler–Bernoulli beam theory considering nonlinear characteristics arising from internal fluid stress. For instance, following the proposed approximate analytical method, we optimize the fluidic actuator, considering that the soft tail deformation increases by 65% as the channel shape transitions from a semicircular to a square cross-section. The comprehensive comparison with analytical nonlinear method, finite element method, and experimental-driven analytical method extends our approach as an effective tool in terms of accuracy and computation time, demonstrating the effectiveness of validation processes. This study unveils a simplified and robust fish robot design, outperforming traditional mechanisms in efficacy. Despite its simplicity, the proposed design delivers comparable performance, presenting an effective alternative for achieving requisite functionality in fish robots.

Summary of the results of field and laboratory studies of hydraulic resistance during channel bending

The reliability of channel forecasts, performed using mathematical modeling methods in the design of engineering activities on shipping rivers, largely depends on the accuracy of the assessment of hydraulic resistance and sediment transport parameters. Therefore, the hydraulic resistance of natural channels is one of the largest problems in the dynamics of channel flows and is the object of close attention of scientists. In the resistance of natural channels, roughness appears in three forms: the first of them is the roughness of the granular surface of the bottom; the second is the roughness created by boulders and the third type is the roughness of microforms: ripples and ridges. Channel mesoforms also contribute to the resistance to water movement: spits, side streams, middle streams, islands, bends of the channel and such complex formations as riffles. This type of resistance is usually called the resistance of the channel form. The resistance of the natural channel shape due to the movement and deformation of mesoforms can change significantly over time. The complexity and insufficient study of this issue significantly limit the possibilities of a theoretical approach to its solution. Therefore, the obtained results are mainly empirical or semiempirical in nature. The paper presents the results of experimental and field studies that allowed us to identify the main features of flow movement in winding sections of rivers. One of the features of flow movement at channel turns is the possibility of additional energy losses. The total resistance of a curved section of a channel is made up of three main parts: the resistance of the granular surface of the bottom, the resistance of the bottom ridges, and the resistance of the channel shape. The additional resistance created by the bend depends on the curvature of the channel, the rate of change in depth along the length of the bend, and also reflects the impact of side streams formed near the convex bank on the flow.

Detection of oesophageal cancer based on the JS-DETR model

Oesophageal cancer is a serious threat to human health and life due to its high incidence levels and mortality rates. Early detection and diagnosis are crucial. However, existing oesophageal cancer detection models are plagued with missed detections and false-positives, especially with small and irregular lesions. To address these challenges, a novel approach called JS-DETR has been proposed, which combines Joint position channel attention and Shape adaptation improvement loss with DEtection TRansformer (DETR). In JS-DETR, several key improvements are made to enhance the accuracy of automated oesophageal cancer detection and localization. First, the DETR backbone is reinforced by incorporating joint position channel attention, enhancing the model’s ability to learn and utilize crucial features effectively. Second, shape adaptation improvement loss is employed to refine the model’s regression loss function, resulting in more accurate predictions of the precise locations of oesophageal cancer targets. Finally, transfer learning is utilized to fine-tune the enhanced model by transitioning it from the COCO dataset to the oesophageal cancer barium swallow imaging dataset. The JS-DETR model achieves a precision of 76.9%, a recall of 79.4%, an average precision of 87.0%, and an F1-score of 78.1% in the experimental results. Compared to other currently popular object detection models. The JS-DETR model enables more precise detection and localization of oesophageal cancer, offering clinicians a more accurate means of oesophageal cancer detection. Our code is available at https://github.com/learningmuch/JS-DETR.

Trp-574-Leu and the novel Pro-197-His/Leu mutations contribute to penoxsulam resistance in Echinochloa crus-galli (L.) P. Beauv.

Recently, due to the widespread use of the acetolactate synthase (ALS)-inhibiting herbicide penoxsulam in paddy fields in China, Echinochloa crus-galli (L.) P. Beauv. has become a problematic grass weed that is frequently not controlled, posing a threat to weed management and rice yield. There are many reports on target-site mutations of ALS inhibiting herbicides; however, the detailed penoxsulam resistance mechanism in E. crus-galli remains to be determined. Greenhouse and laboratory studies were conducted to characterize target-site resistance mechanisms in JL-R, AH-R, and HLJ-R suspected resistant populations of E. crus-galli survived the field-recommended dose of penoxsulam. The whole-plant dose-response testing of E. crus-galli to penoxsulam confirmed the evolution of moderate-level resistance in two populations, JL-R (9.88-fold) and HLJ-R (8.66-fold), and a high-level resistance in AH-R (59.71-fold) population. ALS gene sequencing identified specific mutations in resistant populations, including Pro-197-His in ALS1 for JL-R, Trp-574-Leu in ALS1 for AH-R, and Pro-197-Leu in ALS2 for HLJ-R. In vitro ALS activity assays demonstrated a significantly higher activity in AH-R compared to the susceptible population (YN-S). Molecular docking studies revealed that Trp-574-Leu mutation primarily reduced the enzyme's ability to bind to the triazole-pyrimidine ring of penoxsulam due to decreased π-π stacking interactions, while Pro-197-His/Leu mutations impaired binding to the benzene ring by altering hydrogen bonds and hydrophobic interactions. Additionally, the Pro-197-His/Leu amino acid residue changes resulted in alterations in the shape of the active channel, impeding the efficient entry of penoxsulam into the binding site in the ALS protein. The three mutant ALS proteins expressed via the Bac-to-Bac baculovirus system exhibited notably lower activity inhibition rates than the non-mutant ALS proteins to penoxsulam, indicating all three ALS mutations reduce sensitivity to penoxsulam. This study elucidated the distinct impacts of the Pro-197-His/Leu and Trp-574-Leu mutations in E. crus-galli to penoxsulam resistance. Notably, the Trp-574-Leu mutation conferred stronger resistance to penoxsulam compared to the Pro-197-His/Leu mutations in E. crus-galli. The Pro-197-His/Leu mutations were first detected in E. crus-galli conferring penoxsulam resistance. These findings provide deeper insights into the molecular mechanisms underlying target-site resistance to penoxsulam in E. crus-galli.

A High-Speed Silicon-Photonics WDM Switch for Optical Networks Applications

This article introduces the design of a novel high-speed silicon-photonics hitless switch that adheres to wavelength-division multiplexing (WDM) standards for channel 3 dB bandwidth, channel free spectral range, crosstalk, shape factor, and dispersion. The design combines the advantages of two structures, a compound ring resonator structure, and a Mach–Zehnder interferometer (MZI) modulator. The mathematical treatment for the proposed device is detailed, and two designs are presented. For a switch of five ring resonators, the through (drop) channel 3 dB bandwidth is 60 GHz (38 GHz), channel crosstalk is −24 dB (−24 dB), dispersion is 22 ps/nm (21 ps/nm), shape factor is 0.66 (0.5), and insertion loss is 0.3 dB (1.7 dB). For a switch of nine ring resonators, the through (drop) channel 3 dB bandwidth is 59 GHz (38 GHz), channel crosstalk is −37 dB (−24 dB), dispersion is 28.5 ps/nm (29 ps/nm), shape factor is 0.8 (0.73), and insertion loss is 0.3 dB (2.3 dB). For the five-ring design, the switch-on/off ratio is 30 dB, and for the nine-ring design, it is 31 dB. For both designs, the switching speed is 100 GHz.

Performance Characteristics of a Free-Breathing Polymer Electrolyte Fuel Cell with Various Channel Shapes

Free-breathing fuel cells of channel-type cathodes have straight vertical channels with open ends to supply oxygen to their cathode by natural convection. The channel structure should efficiently feed air to the cathode and ensure uniform contact between the electrode and the electrolyte. Several studies have reported the performance characteristics of free-breathing fuel cells with channel-type cathodes, including the effects of the width and the depth of the channels, the thickness of the gas diffusion layers, and the air blowing into the channels. However, we have seen no full reports investigating the performance characteristics of free-breathing fuel cells as a function of their channel shapes. This study utilized a small free-breathing fuel cell, with an active area of 4 cm2 (2 cm × 2 cm), and channel cathodes with various channel shapes, to experimentally investigate the effect of channel structure on cell performance, to numerically analyze the natural convection air flow in channels, and to compare with the results of performance characteristics.Our free-breathing fuel cell used a solid polymer electrolyte membrane of Nafion 112, with a thickness of 50 μm. The electrodes with gas diffusion layers were carbon paper (TGP-H-120) with a thickness of 0.37 mm, loaded with 1.0 mg/cm2 platinum. A separator on the anode had a meander channel with a width of 2 mm and a depth of 1 mm. The various channel-type separators on the cathode were based on a separator with four straight channels with a width of 3 mm, a depth of 3 mm, and a rib width of 2 mm, then some of the ribs were eliminated or their shapes were modified to promote natural convection through the channels.Experiments were carried out with the cell center plane perpendicular to the ground, and the channels of the cathode separator oriented vertically. The cell voltage and resistance (at a frequency of 10 kHz) were measured, by increasing current density in increments of 5 mA/cm2, until the cell voltage dropped to 0.3 V, at a non-humidified hydrogen supply rate of 7.0 cm3/min (normal). Experiments were conducted at ambient temperatures of 16 - 22 ºC and relative humidities of 35 - 40%.The experimental results indicated that, compared with a conventional cathode separator with four straight channels, cell performance was improved by eliminating some of the channel ribs and increasing the opening ratio, up to a point. A separator with 2 mm square ribs rotated by 45° further improved cell performance. However, when the opening ratio became too large, cell performance leveled off.CFD ULTIMATE (Autodesk Inc.) software was used to analyze the natural convection air flow. The analytical model consisted of the cathode separator, the electrode, the gasket, and their separating spaces, as well as spaces above and below the cathode separator (3 mm thick x 31 mm wide x 100 mm long). Natural convection of air was analyzed in these spaces. The temperature was set at 25 ºC on the electrode surface and 20 ºC on the other surfaces. The gauge pressure at the inlet of the space below the separator and at the outlet of the space above was set to 0 Pa. No air flow was allowed in the vertical direction on the sides of the spaces above and below the separator. The turbulence model was a low Reynolds number k-ε model and the analysis method was incompressible steady flow.The analysis results showed that, compared with a conventional cathode separator with four straight channels, eliminating some of the ribs and increasing the opening ratio resulted in higher flow velocities in the channels. In addition, a separator with 2 mm square ribs rotated by 45° showed even higher velocities next to the ribs. These analysis results revealed that separators with modified channels improved cell performance by promoting natural convection.

Enhancing double-slope solar still performance through integrated channel shape variations: An experimental and numerical simulation investigation

The solar still system effectively addresses water scarcity concerns by adopting suitable methods for enhancing yields. Incorporating a preheating system, such as channels within solar still leads to an increased yield from the conversion of saline water. This research integrates various channel shapes (square, rectangular, triangular, and trapezoidal) into double-slope solar stills (DSSS) and their internal properties using numerical simulation and experimental processes under similar climatic conditions. A three-dimensional, multi-phase computational fluid dynamics (CFD) model of solar still was developed using Ansys Fluent 18.1 to compare simulation results with experimental data under the atmospheric conditions of Chengalpattu. The simulation predicted a maximum water yield of 0.44 kg/m2/h, while experimental data showed a peak yield of 0.41 kg/m2/h between 1 p.m. and 2 p.m. There is a 6.82 % variation between the simulations and the experiments. According to the experimental results, the modified system shows a maximum variation of 8.13 % in influence parameter; the yield rate differences for the square, rectangular, triangular, and trapezoidal channels are 8.13, 7.24, 6.73, and 6.52 %, respectively. Trapezoidal channels are superior to other shapes due to their large evaporation capacity, higher wall temperatures due to increased solar absorption area, and superior base resistance. The simulation further explains the heat and mass transfer mechanics into the channel due to resistance from the feed water surface. The research suggests that varying channel shapes inside solar still enhance evaporation and yield rates compared to DSSS systems.

Study on Springback Behavior in Hydroforming of Micro Channels for a Metal Bipolar Plate.

Bipolar plates are one of the most important components of proton exchange membrane fuel cells. With the miniaturization of bipolar plate flow channel sizes and the increasing demand for precision, springback has become a key focus of research in the bipolar plate forming process. In this paper, the hydroforming process for 316L stainless steel bipolar plates was studied, and an FEM model was built to examine the stress and strain at various locations on the longitudinal section of the plate. Modeling accuracy was validated by the comparison of experimental profile and thickness distribution. The effects of forming pressure and grain size on springback behavior are discussed. The results show that with increasing forming pressure, the springback value decreases initially, followed by an increase, but then again decreases. When the forming pressure is 80 MPa-100 MPa, the deformation of the lower element of the upper rounded corner is not uniform with more elastic regions, and the springback is positively correlated with forming pressure. The springback distribution pattern on the cross-section of the bipolar plate changes from a normal distribution to a distribution of "M" shape with increased pressure. The larger the grain size, the lower the yield strength elastic proportion, resulting in a decrease in springback of the sheet. The maximum amount of springback of the bipolar plate is 3.1 μm when the grain size is 60.7 μm. The research results provide a reference for improving the forming quality of metal bipolar plates with different flow channel shapes.

Wood Chippers

The position and shape of the feed channel (FC) in low-power woodchippers significantly affect the way machine operators' upper limbs move. The execution of operator's movements can be accomplished in different working areas: comfortable, acceptable, or not recommended due to overloads in the musculoskeletal system. Three groups of male subjects from Central Europe, divided according to anthropometric dimensions from centile groups C5, C50 and C95, were selected to assess upper limb movement, by adopting a Motion Capture measurement method. The tests have shown that the limb closer to the FC (left hand in this study) carries out all the movements in the allowed zone (AZ), while between 79% and 96% of the limb movement is contained within the comfort zone (CZ). The right limb has a greater amplitude of motion outside the CZ working area – from 0% to 69% and for AZ – in the CZ can vary by up to 51%. It was found that commercial low-power woodchippers deployed in urban areas, typically induce overloads in the musculoskeletal system of the operator during the use. Based on the research results, the authors see the need to improve FC position adjustment for the operators of these machines.

Wave Reformer Channel Shape Design for Enhanced Hydrogen Pyrolysis

Wave Reformer Channel Shape Design for Enhanced Hydrogen Pyrolysis

Application of 3D Geological Modeling Technology for Single Sand Body in Block S

Abstract The P oil layer is generally in a medium to high water cut period, with scattered macroscopic residual oil distribution. The reserves are mainly distributed in the microfacies of river sand bodies, and the main layer is severely flooded with water, resulting in ineffective circulation in some areas. Therefore, it is necessary to tackle the modeling technology within the layer and describe the remaining oil within the layer to meet the needs of tapping the potential of remaining oil during the high water cut period. This article takes the establishment of a three-dimensional geological model of a single sand body within the S block layer as an example. Based on the establishment of a fine structural model, the “plane and vertical dual control” modeling method is used. The implementation method is: controlling the range of sedimentary facies maps → using the top surface of the sand body as the top depth of the river channel → controlling the vertical shape of the river channel through the facies controlled sandstone contour map, thereby achieving the vertical shape of the river channel through the facies controlled sandstone contour map, and establishing a three-dimensional sedimentary facies model of a single sand body. Optimize the method for characterizing interlayers, achieve modeling of single sand body interlayers, and perform random simulation interpolation in phases to obtain attribute models. The use of a single sand body model within a layer can visually display the three-dimensional channel morphology and classify the identified connected bodies within the study area. The upscaling method of sedimentary facies models with irregular boundaries greatly reduces the number of model grids and provides a relatively refined geological model for numerical simulation.

Performance Characteristics of a Free-Breathing Polymer Electrolyte Fuel Cell with Various Channel Shapes

This study utilized a small free-breathing fuel cell, with an active area of 4 cm2 (2 cm x 2cm), and channel cathodes with various channel shapes, to experimentally investigate the effect of channel structure on cell performance, to numerically analyze the natural convection air flow in channels, and to compare with the results of performance characterisitics. The results indicated that, compared with a conventional cathode separator with four straight channels (with a width of 3 mm, a depth of 3 mm, and a rib width of 2 mm), cell performance was improved by eliminating some of the channel ribs and increasing the opening ratio, up to a point. A separator with 2 mm square ribs rotated by 45° further improved cell performance. However, when the opening ratio exceeded 72% with a straight center rib of 2 mm width, cell performance leveled off. The analysis results revealed that separators with modified channels promoted natural convection.

Performance Characteristics of a Free-Breathing Polymer Electrolyte Fuel Cell with Various Channel Shapes

This study utilized a small free-breathing fuel cell, with an active area of 4 cm2 (2 cm x 2cm), and channel cathodes with various channel shapes, to experimentally investigate the effect of channel structure on cell performance, to numerically analyze the natural convection air flow in channels, and to compare with the results of performance characterisitics. The results indicated that, compared with a conventional cathode separator with four straight channels (with a width of 3 mm, a depth of 3 mm, and a rib width of 2 mm), cell performance was improved by eliminating some of the channel ribs and increasing the opening ratio, up to a point. A separator with 2 mm square ribs rotated by 45° further improved cell performance. However, when the opening ratio exceeded 72% with a straight center rib of 2 mm width, cell performance leveled off. The analysis results revealed that separators with modified channels promoted natural convection.

Assessment of Additive Manufactured Micro-Channel Characteristics: Impact of Hydraulic Diameter Evaluation

Abstract Among internal cooling techniques for gas turbines components, skin cooling is recognized as one of the most promising, especially thanks to the spread of additive manufacturing techniques. In this regard, several studies have tried to characterize heat transfer and pressure loss performance of additive manufactured micro-channels, as well as the impact of AM characteristic parameters, mainly in the form of building angle, and resulting surface roughness and channel shape. The open literature offers several correlations in terms of friction and heat transfer coefficient using a representative hydraulic diameter. Despite that, little attention is given on the importance of such characteristic length definition which may lead to under/over estimation of the cooling rates when correlations are used in the design In this work, coupons featuring circular micro-channelswith diameters of 0.5 and 1 mm and different building angles have been tested, to retrieve pressure losses and an average heat transfer coefficient through a lumped approach. The coupons were additive manufactured using the Laser Powder Bed Fusion (L-PBF) technique. Exploiting the experimental survey, the impact of the considered hydraulic diameter was investigated, by comparing different approaches based on a direct measurement. An additional and new approach, aimed at the identification of an “effective” diameter, based on fluid-dynamic considerations, was also considered. The data correlation and the comparison with available correlations from different authors showed the newly proposed approach to provide superior scaling capabilities and, in turn, allowing for the development of more accurate prediction methods

Twice-topology optimized heat sinks for enhanced heat transfer performance: Numerical and experimental investigation

Since the heat dissipation problem is always confusing and hindering the computing power improvement of electronic chip, an effective thermal management strategy is critical to relieve these problems. In this work, a new twice topology optimization design method combining topology optimization and image processing to design heat sinks is presented, which extends topology optimization from 2Dimention (2D) to 3Dimention(3D). Firstly, on the horizontal design domain, the conventional topology optimization is conducted for the minimization of average temperature/standard deviation. Then the optimal shape of liquid domain is converted into 1D flow routine by thinning algorithm. After that, another topology optimization is performed on the flow channel cross-section plane to get the best cross-section shape of channels. The liquid domain of the final heat sink is then obtained by scanning the optimized flow channel cross-section along the 1 Dimension (1D) flow routine and solving the interference by introducing cylinder joints. Finally, two kinds of twice topology optimized heat sinks including TTOHS-1 with minimized temperature variation as optimal goal and TTOHS-2 with minimized average temperature as optimal goal are generated by combining the liquid domain and a cuboid using Boolean Operation. The performance of heat sinks is numerically investigated, and the results indicate that the thermal performance of TTOHS-1 and TTOHS-2 are much better than that of the traditional heat sink with straight channels (TSCHS). When Re = 689, the average temperature and the maximum temperature of the heat source surface of TTOHS-1 are decreased by 4.99 % and 6.29 % respectively, compared to the TSCHS. The Nusselt number is increased by 46.16 % while the thermal resistance is reduced by 33.13 %. At last, the thermal and flow performance of the TTOHS-1 is studied by conducting experiments, showing that the numerical results agree well with that of the experiment.

Numerical investigation for the effects of surface roughness in counter flow microchannel heat exchanger with different channels geometries

This article presents a numerical investigation focused on how roughness of surface affects the overall performance of a counter-flow microchannel heat exchanger (CFMCHE). The study examines various microchannel shapes, including triangles, squares, circles, and trapezoids, to evaluate their performance within the context of CFMCHE. Water with consistent properties flows through aluminum microchannels used as the working fluid. The analysis employs the roughness-viscosity method to assess how surface roughness influences the CFMCHE’s performance. The study’s findings emphasize that the trapezoidal channel shape exhibits the most favorable performance among the shapes investigated. Additionally, among the operational parameters considered, the hydraulic diameter emerges as the most influential factor in determining the most suitable characteristics for CFMCHE. The presence of surface roughness was found to marginally improve thermal performance while slightly reducing hydraulic efficiency. This research provides valuable insights into the intricate interplay between surface roughness and channel shape. Notably, the impact of roughness is more pronounced in the case of the trapezoidal shape compared to other geometries.

Three-dimensional numerical simulation of two-phase flow in a proton exchange membrane electrolysis cell and study of the effect of flow channel depth

Abstract The flow channel play a critical role in water-gas transfer within an electrolysis cell, directly impacting its mass and heat transfer capacity. While most studies concentrate on the overall shape and structure of the flow channel, limited attention has been given to its dimensions. This paper investigates the influence of various operational conditions and changes in flow channel depth on the electrolytic cell using a three-dimensional numerical model of PEMEC. Results indicate that higher temperatures enhance electrolysis cell performance, whereas the impact of water inlet velocity on the polarization curve is insignificant. Under constant inlet velocity, increasing the depth of the flow channel improves mass and heat transfer as well as electrolysis performance, whereas, under constant water flow rate, changes in inlet velocity have a greater effect than alterations in flow channel depth.

Simulation analysis on the influence of airflow channel shape on the thermal storage and release performance of solid heat storage device

Simulation analysis on the influence of airflow channel shape on the thermal storage and release performance of solid heat storage device