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To investigate the energy-saving advantages of truck platoons, this study focused on two, three, and six-axle trucks as research subjects. A non-uniform platoon model of trucks was constructed based on braking performance differences. The aerodynamic characteristics of the non-uniform platoon fleet were analyzed in depth using numerical simulation methods, and the fuel consumption rate of the fleet was calculated. In a heterogeneous three-vehicle platoon, the 3-2-6 platooning approach exhibited the most effective reduction in fuel consumption, whereas the 3-6-2 platooning approach was the least effective. For a four-vehicle heterogeneous platoon comprising a three-axle truck, a six-axle truck, and two two-axle trucks, the 3-2-2-6 platooning approach yielded the best fuel efficiency. In a four-vehicle heterogeneous platoon with a two-axle truck, a six-axle truck, and two three-axle trucks, the 3-2-3-6 platooning approach proved to be the most effective in reducing fuel consumption. In a four-vehicle heterogeneous fleet composed of two-axle trucks, three-axle trucks, and two six-axle trucks, the 3-2-6-6 platooning approach achieved the best fuel efficiency. The conclusions of this study offer a fundamental scheme for truck formation, laying a crucial theoretical foundation for energy conservation and emissions reduction in transport systems. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Light Industry Machinery is the property of Light Industry Machinery Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Physics-based fluid simulation has played an increasingly important role in the computer graphics community. Recent methods in this area have greatly improved the generation of complex visual effects and its computational efficiency. Novel techniques have emerged to deal with complex boundaries, multiphase fluids, gas–liquid interfaces, and fine details. The parallel use of machine learning, image processing, and fluid control technologies has brought many interesting and novel research perspectives. In this survey, we provide an introduction to theoretical concepts underpinning physics-based fluid simulation and their practical implementation, with the aim for it to serve as a guide for both newcomers and seasoned researchers to explore the field of physics-based fluid simulation, with a focus on developments in the last decade. Driven by the distribution of recent publications in the field, we structure our survey to cover physical background; discretization approaches; computational methods that address scalability; fluid interactions with other materials and interfaces; and methods for expressive aspects of surface detail and control. From a practical perspective, we give an overview of existing implementations available for the above methods. [ABSTRACT FROM AUTHOR]

Traditional computational fluid dynamics(CFD) solver encounters significant computational costs and struggles with simulating fluids due to the inherently high-dimensional and nonlinear properties. To improve the computational efficiency, a framework combining multi-task learning and graph neural networks (GNN) was proposed here, which could predict unsteady flow quickly and efficiently. Firstly, the fluid computational domain's spatial distribution was modeled by unstructured grids. Then, GNN was employed to extract multidimensional spatial features from this distribution. Finally, the aggregation and updating properties of the message passing mechanism were used to simulate the spatio-temporal variation patterns of the fluid. Considering that there were some correlations between different physical fields, a multi-task learning strategy was adopted to learn the variations of multiple physical field parameters in parallel, which could improve the accuracy and generalization of the model. Validation experiments were carried out on a simulation dataset and compared with graph convolutional neural network. The results show that our model has the best prediction results, with a relative decrease of 7. 2% in mean square error (MSE) at 100 steps and 29. 9% at 200 steps. This model also has a large improvement in computational efficiency, and its prediction speed is improved by one to two orders of magnitude compared with the conventional CFD solver, which provides a good solution on real-time prediction. [ABSTRACT FROM AUTHOR]

Membrane separation technology is one of the most widely studied methods for wastewater treatment. This paper is based on the non-solvent-induced phase separation (NIPS) method, which is combined with phase-field simulation to develop a fluid model for the volume fraction of tetrameric polyvinylidene fluoride (PVDF).In this paper, DMSO, DMAc and DMF are used as solvents, and pure water is used as a gel bath to simulate the relevant parameters of PVDF membrane; and PVP and LiCl are used as additives, and DMF and DMAc are used as solvents for the two-by-two combinations, and by calculating the relevant parameters of the PVDF quaternary membrane system, comparing and verifying the simulation results through experiments. results show that: the different solvents on the PVDF membrane in the order of DMSO > DMAc > DMF; additive LiCl system, the polymer diffusion rate in the polymer solution layer are faster than the PVP system. However, the top layer of the polymer solution layer in the PVP system is relatively flat, while the top layer of the polymer solution layer in the additive LiCl system is more undulating or even broken, indicating that LiCl has a greater influence on the membrane than PVP. [ABSTRACT FROM AUTHOR]

Featured Application: Silicon-based material etching and thin film deposition. In this work, the two-dimensional fluid models for two types of inductively coupled plasma, Ar/O2 and Ar/SF6, are numerically solved by the finite element method. Four interesting phenomena revealed by the simulations are reported: (1) comet-shaped and semi-circle-shaped structures in Ar/O2 and Ar/SF6 plasmas, respectively; (2) blue sheaths that surround the two structures; (3) the collapse and dispersion of semi-circle-shaped structures of certain Ar/SF6 plasma cations and anions when they are observed separately; and (4) the rebuilding of coagulated structures by minor cations in the Ar/SF6 plasma at the discharge center. From the simulation detail, it was found that the cooperation of free diffusion and negative chemical sources creates the coagulated structure of anions, and the self-coagulation theory is therefore built. The advective and ambipolar types of self-coagulation are put forth to explain the co-existence of blue sheath and internal neutral plasma, among which the advective type of self-coagulation extends the Bohm's sheath theory of cations to anions, and the ambipolar type of self-coagulation originates from the idea of the ambipolar diffusion process, and it updates the recognition of people about the plasma collective interaction. During the ambipolar self-coagulation, each type of Ar/SF6 plasma cations and anions is self-coagulated, and the coagulated plasma species are then modeled as mass-point type (or point-charge type, more precisely). When the charge amounts of two point-charge models of plasma species with the same charge type are equal, the expelling effect caused by the Coulomb's force of them leads to the collapse or dispersal of heavily coagulated species. The simulation shows that the lighter the species is, the easier it self-coagulates and the more difficult its coagulation is broken, which implies the inertia effect of density quantity. Moreover, the collapse of cation coagulation creates the spatially dispersed charge cloud that is not shielded into the Debye's length, which indicates the anti-collective behavior of electronegative plasmas when they are self-coagulated. The rebuilt coagulated structure of minor Ar/SF6 plasma species at the discharge center and the weak coagulation of electrons in the periphery of the main coagulated structure that is under the coil are caused by the monopolar and spontaneous (non-advective) type of self-coagulation. The analysis predicts an intensity order of physically driven coagulation force, chemical self-coagulation force, and ambipolar self-coagulation force. The popular coagulated structure of the electronegative ICP sources is urgently needed to validate the experiment. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objectives: With the rapid development of electric vehicles (EVs), the maximum rotational speed of EV motors has reached up to 20 000 r/min. Precision polishing of gear surfaces after grinding has become a promising method for improving the noise, vibration, and harshness (NVH) performance of EVs. Abrasive Flow Machining (AFM) is one of the key technologies for efficiently polishing complex gear tooth surfaces. Fixture design plays a critical role in achieving process objectives, reducing surface ripple and roughness, and minimizing damage to the tooth surface accuracy. This article addresses the trade-off between selecting physical models and balancing the accuracy and computational cost of simulation results. It analyzes the impact of different simulation models on the results, providing guidance for AFM fixture design and offering practical experience for fixture optimization in AFM gear processing. Methods: Simulations are conducted using media with different viscosities, viscosity models, and flow models, within the simplest and most typical slit model. Fluid pressure distribution, velocity vectors, wall shear, and streamline distribution cloud mapsare analyzed to reflect machining uniformity. Based on the conclusions drawn from slit model simulations, the simplest Newtonian fluid—water—is selected as the medium for AFM gear shaft processing simulations. The focus is on the uniformity of streamline distribution in the machining area to optimize fixture design. Results: The analysis of slit model simulation results reveals that different physical models have varying impacts on the outcomes: (1) The selection of viscosity models decisively affects the pressure distribution of low-viscosity media. The type of viscosity and turbulence models has little impact on pressure distribution, but it significantly affects the velocity vector, wall shear, and streamline distribution within the abrasive cylinder. (2) For low-viscosity media: implementing a non-Newtonian fluid model has a significant impact on the pressure distribution. Different flow models show marked differences only in wall shear force distributions. Various viscosity models yield different cloud map distributions, but they produce numerically similar values. (3) For high-viscosity media: simulations with non-Newtonian and Newtonian fluid models show consistent results. However, different flow models greatly influence the results, while various viscosity models lead to changes in all simulation results, except for pressure distribution and streamlines within the slit. Despite these variations, the streamline distribution in the processing area remains largely unchanged. Based on the consistency of streamline distribution, fixture design optimization for the AFM gear shaft is carried out, successfully achieving the goal of eliminating gear "ghost frequencies". Conclusions: Despite variations in the physical models, the simulation results exhibit similar trends in distribution, enabling consistent streamline distribution in the processing area. For low-viscosity media, a non-Newtonian fluid viscosity model with laminar flow simulation can be used, and the selection of viscosity models can be simplified based on the rheological characteristics of the actual abrasive flow medium. For high-viscosity media, setting appropriate viscosity values and using laminar flow simulation with a Newtonian fluid model yields consistent pressure and streamline distribution in the processing area, similar to adding viscosity and turbulence models. The slit model simulation results and AFM gear shaft processing tests both demonstrate that streamline information derived from simple physical models can significantly assist in AFM fixture design. In cases where the physical properties of the abrasive flow medium are uncertain—especially in complex flow paths prone to divergence—using the simplest Newtonian fluid, such as water, with laminar flow simulation can provide a reasonable streamline distribution in the processing area. This approach aids in the analysis of processing uniformity, significantly reduces simulation difficulty and costs, and accelerates the fixture design cycle, ultimately enhancing optimization efficiency.

Hall thrusters are electric propulsion devices widely used on spacecraft. The stability of Hall thrusters is often disturbed by low-frequency oscillations (LFOs) around 5–100 kHz, known as the 'breathing mode', typically observed through fluctuations in channel discharge current and plasma parameters. Experimental studies on Hall thrusters with a wide range of sizes show that LFOs exhibit distinct characteristics depending on the channel structures. The size of the channel can modify the particle-wall interactions, electric potential distribution, and electron temperature, thereby influencing the performance of LFOs. Furthermore, the long-term operation of thrusters can cause significant wall erosion, altering the geometry of the discharge channel, which further impacts LFOs. In this work, a one-dimensional fluid model is established to explore the influences of structure sizes and wall erosion of the channel on the LFO characteristics. Both the thruster channel and the plume region are included in the model, and a modified and more precise approach to calculating the electron energy loss at the wall is proposed, which takes into account the influences of secondary electron emission and the channel cross-sectional area. The simulation results indicate that choosing a narrower or longer channel structure has a significantly suppressing effect on LFOs. An erosion model is established according to the cited experimental data to construct the eroded channel structure and to investigate the effect of channel erosion on the breathing mode, which shows that wall erosion can exacerbate LFOs and impact the performance of the thruster. [ABSTRACT FROM AUTHOR]

Aiming at the problem that inserting a needle into the abdomen of spindle-shaped fish can easily damage the internal organs during vaccine injection, this paper takes grass carp as the experimental object and designs a fry adsorption injection device. Through theoretical analysis, the key factors affecting the adsorption force are determined. The internal cavity of the adsorption block is simulated and optimized under the given boundary conditions. The single-factor test shows that the H-shaped suction head has the best adsorption effect. Further orthogonal experiments found that the height of the adsorption port, the adsorption port's length, and the diameter of the adsorption port are important factors that affect the test results, and they are arranged in descending order of their importance. The optimal parameter combination is the adsorption port height of 3 mm, adsorption port length of 15 mm, and adsorption pore diameter of 3 mm. Under these parameters, the success rate of needle insertion is 98%, and the survival rate of fry is 100%, which can meet the production requirements. In summary, the adsorption and injection device is simple in design, easy to operate, and can significantly reduce the damage to the fish body. It provides an effective solution and design reference for fish vaccination. [ABSTRACT FROM AUTHOR]

We propose an SPH‐based method for simulating viscoelastic non‐Newtonian fluids within a multiphase framework. For this, we use mixture models to handle component transport and conformation tensor methods to handle the fluid's viscoelastic stresses. In addition, we consider a bonding effects network to handle the impact of microscopic chemical bonds on phase transport. Our method supports the simulation of both steady‐state viscoelastic fluids and discontinuous shear behavior. Compared to previous work on single‐phase viscous non‐Newtonian fluids, our method can capture more complex behavior, including material mixing processes that generate non‐Newtonian fluids. We adopt a uniform set of variables to describe shear thinning, shear thickening, and ordinary Newtonian fluids while automatically calculating local rheology in inhomogeneous solutions. In addition, our method can simulate large viscosity ranges under explicit integration schemes, which typically requires implicit viscosity solvers under earlier single‐phase frameworks. [ABSTRACT FROM AUTHOR]

We present an Eulerian vortex method based on the theory of flow maps to simulate the complex vortical motions of incompressible fluids. Central to our method is the novel incorporation of the flow-map transport equations for line elements, which, in combination with a bi-directional marching scheme for flow maps, enables the high-fidelity Eulerian advection of vorticity variables. The fundamental motivation is that, compared to impulse m, which has been recently bridged with flow maps to encouraging results, vorticity ω promises to be preferable for its numerical stability and physical interpretability. To realize the full potential of this novel formulation, we develop a new Poisson solving scheme for vorticity-to-velocity reconstruction that is both efficient and able to accurately handle the coupling near solid boundaries. We demonstrate the efficacy of our approach with a range of vortex simulation examples, including leapfrog vortices, vortex collisions, cavity flow, and the formation of complex vortical structures due to solid-fluid interactions. [ABSTRACT FROM AUTHOR]

Abstract Because of the lack of good seedling positioning during vegetable grafting, there are issues such as high labor costs and long grafting time. This article proposes a negative pressure suction seedling positioning method for seed leaves based on the characteristic parameters of cucumber spike wood, and designs a flexible adsorption positioning mechanism for spike wood. Firstly, the ventral surface curve trajectories of cucumber cotyledons were extracted using Matlab software, and then a shape-adaptive design was applied to the attachment surface of the flexible suction positioning mechanism, and a computational fluid dynamics model of the airflow field was established. By combining Fluent simulation analysis with orthogonal experiments, the effect of suction hole diameter, vacuum negative pressure value, suction hole quantity, and suction hole depth on the adsorption effect of the suction head was analyzed, the main and secondary factors and operational indicators that affect the adsorption effect are evaluated. The optimal parameter combination: suction hole diameter of 1.5 mm, vacuum negative pressure value of 2 kPa, suction hole quantity of 42, and suction hole depth of 2 mm, has been found. A verification experiment was conducted on a test bench, and the experimental results show that the success rate of leaf absorption using the optimal parameter combination is 97.69%, which indicates that the suction head is designed reasonably and meets the requirements of grafting.

The cam tappet friction pair is one of the three major friction pairs in an internal combustion engine, and the surface of the tappet undergoes severe wear during operation. To improve the wear resistance of the cam tappet friction pair during operation, in this study, crescent-shaped micro-textures were prepared on the surface of the tappet material of GCr15 steel by laser machining technique, and the effects of the orientation and depth of the texture on the friction properties of GCr15 steel were studied. The processed test samples were tested and characterized by friction and wear tests, scanning electron microscopy (SEM), 3D morphometry, and EDS. The flow field simulation model of micro-texture was established by using Fluent finite element software. The simulation and experimental results show that the crescent-shaped microtexture prepared on the surface of GCr15 steel can play a certain role in reducing friction and wear resistance, meanwhile orientation and depth of the texture affect the friction performance. In the fluid simulation, the positively oriented texture can produce higher oil film pressure than the opposite texture. When the texture depth is 20 μm, it has a better friction and wear reduction effect, and the friction coefficient decreases by 65.81% compared with that of the untextured surface, and the amount of wear decreases by 74.19%. This is mainly due to the existence of texture in the friction process to reduce the contact area and the shallower depth of texture can produce a larger oil film pressure in the oil lubrication state, so it has better tribological performance. The research data provide a certain reference for the design and optimization of the cam tappet friction pair.

In bone-milling surgical procedures, the intense friction between the tool and bone material often results in high cutting temperatures, leading to the thermal necrosis of bone cells. This paper aims to investigate the effect of micro-texture on the tribological properties of YG8 cemented carbide in contact with bone. The main objective is to guide the design of tool surface microstructures to reduce frictional heat generation. To minimize experimental consumables and save time, numerical simulations are first conducted to determine the optimal machining depth for the texture. Subsequently, micro-textures with different shapes and pitches are prepared on the surface of YG8 cemented carbide. These textured samples are paired with bovine cortical bone pins featuring various bone unit arrangements, and friction and wear tests are conducted under physiological saline lubrication. The experimental results indicate that the appropriate shape and pitch of the micro-texture can minimize the coefficient of friction. The parallel arrangement of bone units exhibits a lower coefficient of friction compared to the vertical arrangement. This study holds significant implications for the design and fabrication of future micro-texture milling cutters. [ABSTRACT FROM AUTHOR]

Automated crack sealing could significantly benefit the maintenance of road pavements, but there is difficulty in depositing the correct volume of sealant material into the hidden crack space. A simulated model of the material flow within a crack space would allow the development of a predictive control scheme, such that the repair robot can apply suitable trajectories and operational parameters to accomplish neatly sealed surfaces. For the first time, the position‐based fluid (PBF) method, a computationally cheap and fast but approximate model of fluid flows, is studied for its feasibility for sealant flow simulation in the robotic injection crack sealing scenario. A Real‐to‐Sim experiment is performed, in which a PBF simulation of sealant in a virtual robotic crack sealing environment is mirrored from the physical lab setup. The fluid simulation is tuned to match the real‐world dynamics through comparison with 132 simulation runs, varying the artificial viscosity parameters U (fluid–fluid viscous interaction) and D (fluid–wall viscous interaction). It was found that U had a varied three‐stage influence on the simulation error while D 's negative influence on the simulation error only effectively applied to fluids satisfying 11\unicode{x0003C}U\unicode{x0003C}100. Through comparing the physical and virtual crack sealing results, the simulation was validated with an average fluid level error of 1.26 mm along a 3.1 mm wide, 16 mm deep and 80 mm long artificial crack, which shows the usefulness of the PBF method for robotic injection sealing. The accuracy and computational requirements of the PBF method are also discussed. [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Stem mustard, the main raw material for pickled mustard tuber, is widely planted in Chongqing, China, and is an important local cash crop. Under the working conditions of sticky and wet soil in the Chongqing area, conventional furrow seeding has problems such as soil sticking to the furrow opener, poor mulching effect, etc. In this regard, this paper proposes the use of non-contact, soil-based, pneumatic shot seeding, in which seeds are shot into the soil to a predetermined depth by a high-speed air stream. The diameter of stem mustard seeds was found to be 1.33 mm, with a spherical rate of 95.32% using physical and mechanical properties. The high-speed camera test was used to determine the air pressure at the appropriate sowing depth, and the seed entry process was simulated by EDEM 2021 software, which analysed the movement process of the seed after entering the soil, and the structure of the seeder was designed based on the resulting test data. The structural parameters of the shot seeding device were analysed by a hydrodynamic simulation using Fluent 2022 R1 software and the following results were obtained: an outlet pipe diameter DC of 2 mm, mixing zone length H of 10 mm, mixing zone inlet diameter D of 15 mm, and steady-state gas flow rate of 80 m/s. Simulation seeding verification was conducted on the final determined structural parameters of the seeding device, and the simulation results showed that the seed velocity could reach 32.3 m/s. In actual experiments, it was found that when the vertical velocity of the seeds was greater than or equal to 26.59 m/s, the seeds could be completely and stably seeded into the soil. Therefore, the designed seeding device can meet the conditions of actual seeding experiments. In conclusion, this research offers a practical guideline for the rapid and precise sowing of stem mustard. [ABSTRACT FROM AUTHOR]

Because of the lack of good seedling positioning during vegetable grafting, there are issues such as high labor costs and long grafting time. This article proposes a negative pressure suction seedling positioning method for seed leaves based on the characteristic parameters of cucumber spike wood, and designs a flexible adsorption positioning mechanism for spike wood. Firstly, the ventral surface curve trajectories of cucumber cotyledons were extracted using Matlab software, and then a shape-adaptive design was applied to the attachment surface of the flexible suction positioning mechanism, and a computational fluid dynamics model of the airflow field was established. By combining Fluent simulation analysis with orthogonal experiments, the effect of suction hole diameter, vacuum negative pressure value, suction hole quantity, and suction hole depth on the adsorption effect of the suction head was analyzed, the main and secondary factors and operational indicators that affect the adsorption effect are evaluated. The optimal parameter combination: suction hole diameter of 1.5 mm, vacuum negative pressure value of 2 kPa, suction hole quantity of 42, and suction hole depth of 2 mm, has been found. A verification experiment was conducted on a test bench, and the experimental results show that the success rate of leaf absorption using the optimal parameter combination is 97.69%, which indicates that the suction head is designed reasonably and meets the requirements of grafting. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Explosives & Propellants is the property of Chinese Journal of Explosives & Propellants Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In addition to water repellency, superhydrophobic leaves of plants such as Salvinia molesta adsorb oil and separate it from water surfaces. This phenomenon has been the inspiration for a new method of oil–water separation, the bionic oil adsorber (BOA). In this paper, we show how the biological effect can be abstracted and transferred to technical textiles, in this case knitted spacer textiles hydrophobized with a layered silicate, oriented at the biology push approach. Subsequently, the transport of the oil within the bio-inspired textile is analyzed by a three-dimensional fluid simulation. This fluid simulation shows that the textile can be optimized by reducing the pile yarn length, increasing the pile yarn spacing, and increasing the pile yarn diameter. For the first time, it has been possible with this simulation to optimize the bio-inspired textile with regard to oil transport with little effort and thus enable the successful implementation of a self-driven and sustainable oil removal method. [ABSTRACT FROM AUTHOR]

Fluid simulation is an essential tool to produce realistic looking animations. In particular, Lagrangian simulations offer interactive computation times with an easy integration of the two-way interaction with rigid bodies. However, the interactivity is lost for larger scenes even if only the areas around the bodies have any visual interest. In this paper, we present a novel approach to quickly initialize additional fluid in a rest state in simulations with any 3D boundary shape and able to preserve any already existing fluid. Our approach only uses the density property of the particles to allow compatibility with any smoothed-particle hydrodynamics (SPH) simulation scheme and any boundaries model. This initialization method is fast enough to allow the initialization of new fluid volumes interactively while the simulation is running. We showcase our approach by proposing a method to create a dynamic simulation window, allowing the restriction of simulating the fluid only around moving objects. We propose multiple experiments to demonstrate the capabilities and performance of our approach. [ABSTRACT FROM AUTHOR]

In order to meet the functional characteristics of the flying wall crawler, the structure of the flying wall crawler is such that the four rotors are not in the same plane but in a longitudinal arrangement when in flight. The CFD (computational fluid dynamics) simulation of the single-rotor flow field was carried out to verify its reliability. On the basis of these simulations, aerodynamic simulations were carried out for different horizontal spacing, different vertical spacing and different rotational speeds of the longitudinal double rotor. The results were then analysed to determine the effect of the horizontal and vertical spacing and the rotational speed on the aerodynamic characteristics of the front and rear rotor blades and the whole system. The simulation results show that the transverse pitch has a large aerodynamic interference between the longitudinal rotor blades, while the axial pitch is relatively small and the degree of interference is related to the rotational speed. It is clear that the conclusions can provide a basis for the rotor layout, rotational speed and feasibility of flying wall climbing robots. [ABSTRACT FROM AUTHOR]

In this work, the temporal evolution of secondary streamers in N2/O2 mixtures at atmospheric pressure under DC voltage were investigated using a two-dimensional axisymmetric fluid model. The effects of voltage amplitude, polarity and oxygen concentration were analyzed. The propagation of secondary streamers is divided into two stages: fast propagation followed by slow propagation. The interior of secondary streamers is filled with positive space charges, while the exterior contains negative space charges. The reduced electric field in the secondary streamer is initially linearly proportional to the applied voltage and decreases linearly with the length of secondary streamers. The length of secondary streamers is primarily determined by the applied voltage, regardless of the oxygen concentration. A reversed propagation direction is simulated under negative applied voltage. We propose a different mechanism for secondary streamers. The high-density positive charge layer near the electrode initiates the propagation of secondary streamers, and the extension of positive charge region dominates the propagation. The distribution of electric field along the channel is mainly determined by the distribution of net space charge. The propagation direction is opposite to the direction of electron drift. The secondary streamer eventually stagnates due to the decrease in electron density in high oxygen concentration, while it is caused by the uniform current density at the front of the secondary streamer in low oxygen concentration. [ABSTRACT FROM AUTHOR]

Introduction: One major obstacle in validating drugs for the treatment or prevention of hearing loss is the limited data available on the distribution and concentration of drugs in the human inner ear. Although small animal models offer some insights into inner ear pharmacokinetics, their smaller organ size and different barrier (round window membrane) permeabilities compared to humans can complicate study interpretation. Therefore, developing a reliable large animal model for inner ear drug delivery is crucial. The inner and middle ear anatomy of domestic pigs closely resembles that of humans, making them promising candidates for studying inner ear pharmacokinetics. However, unlike humans, the anatomical orientation and tortuosity of the porcine external ear canal frustrates local drug delivery to the inner ear. Methods: In this study, we developed a surgical technique to access the tympanic membrane of pigs. To assess hearing pre- and post-surgery, auditory brainstem responses to click and pure tones were measured. Additionally, we performed 3D segmentation of the porcine inner ear images and used this data to simulate the diffusion of dexamethasone within the inner ear through fluid simulation software (FluidSim). Results: We have successfully delivered dexamethasone and dexamethasone sodium phosphate to the porcine inner ear via the intratympanic injection. The recorded auditory brainstem measurements revealed no adverse effects on hearing thresholds attributable to the surgery. We have also simulated the diffusion rates for dexamethasone and dexamethasone sodium phosphate into the porcine inner ear and confirmed the accuracy of the simulations using in-vivo data. Discussion: We have developed and characterized a method for conducting pharmacokinetic studies of the inner ear using pigs. This animal model closely mirrors the size of the human cochlea and the thickness of its barriers. The diffusion time and drug concentrations we reported align closely with the limited data available from human studies. Therefore, we have demonstrated the potential of using pigs as a large animal model for studying inner ear pharmacokinetics. [ABSTRACT FROM AUTHOR]

In this paper, we propose a learning model for tracking the isolines of fluid based on the physical properties of particles in particle-based fluid simulations. Our method involves analyzing which weights, closely related to surface tracking among the various physical properties of fluid particles, are significant. These weights are used as input values for the learning algorithm, enabling relatively accurate isoline tracking. In addition, compared to existing learning models such as linear regression, LSTM (long short-term memory), and learning representation (1-layer) models, our method obtained superior surface tracking results without accumulating errors. By using our proposed network structure to track the fluid surface, it learns and predicts values derived from existing fluid simulation algorithms, eliminating the need for computational processes for level-set values and enabling real-time surface tracking. As the scale of the simulation increases, our method significantly reduces the time and resources consumed compared to traditional methods and can track the fluid surface without additional resource consumption. Furthermore, due to our method's simple network structure, the time consumed in the initial process of loading the model into memory is faster than models such as CNN and LSTM. Our proposed model occupies less than 30 kb of storage space, making it suitable for use in middleware. Lastly, to verify the generality of our method, we conducted tests in a total of five scenes, and in all test scenes, visually natural fluid isolines were represented. [ABSTRACT FROM AUTHOR]

An atmospheric pressure jet that effectively prevents inner wall deposition has been developed, and its precursor distribution and thin-film deposition characteristics have been studied. The laser scattering and fluid simulation results show that the precursor (C4H10Zn) flow out of the eight holes of the central electrode and diffuse into the discharge region. Under the action of a discharge gas (Ar) of 2 slm is blown out of the plasma jet device, and will not diffuse to the inner wall of the plasma jet device. The optical photographs of the discharge show that the site of the monomer cleavage is about 1 mm closest to the inner wall of the jet device. With optical emission spectra (OES), a large number of characteristic emission peaks of Zn and CH were detected. The pattern of the deposited film closely resembles the diffusion pattern of the precursor within the plasma jet apparatus. By investigating deposited films in different regions, the influence of precursor distribution on film morphology and composition has been studied. XPS detected films near (black film) and far (white film) from the central region, and the results showed that films near the central region contained more organic components. This plasma device offers a stable plasma plume for thin film deposition and nanoparticle preparation. [ABSTRACT FROM AUTHOR]

Fused Deposition Modeling (FDM), a widely-utilized additive manufacturing (AM) technology, has found significant favor among automotive manufacturers. Polypropylene (PP) compound is extensively employed in the production of automotive parts due to its superior mechanical properties and formability. However, aiming at the problem of poor dimensional accuracy of pure PP parts, the quality of products can be enhanced by optimizing the combination of processing parameters. In this paper, the dimensional accuracy of 3D-printed components made from pure PP material is investigated. Key influencing factors such as infill percentage, infill pattern, layer thickness, and extrusion temperature are considered. To gain a deeper understanding, fluid simulation is conducted, and mathematical models are established to correlate processing parameters with dimensional accuracy. Furthermore, the Taguchi's experiments are designed and the experimental data are subjected to rigorous Signal-to-Noise ratio and ANOVA analyses. Within the experimental range, the lower extrusion temperature, infill percentage and layer thickness yield the best dimensional accuracy. Considering the influence factors of X, Y and Z directions, the optimal processing parameters for PP prints using screw extrusion 3D printers are determined as follows: an extrusion temperature of 210 °C, an infill percentage of 40 %, a layer thickness of 0.3 mm, and a concentric circle infill pattern. This study provides reference value for the subsequent improvement of the dimensional accuracy of the printed parts.

Outdoor aerosol processes are often associated with disasters and diseases, which threaten human life and health. Outdoor aerosols are a fluid system affected by meteorological conditions and three-dimensional complex terrain. Their variable wind speed and direction and complex terrain boundary conditions make simulating advection processes difficult. Based on incompressible flow conditions, we designed an adaptive time step algorithm for forward advection for the rapid simulation of aerosol processes. The method is based on the first-order forward semi-Lagrangian advection method with unconditional mass conservation. The first-order truncated error coefficient function theory generates an adaptive time step to control the accuracy of forward advection. Smoke aerosol simulation experiments in two small outdoor scenes were designed, and the effects of the traditional backward advection and forward fixed step methods were compared with the algorithm in this study. The proposed simulation method showed improved accuracy compared with the other two methods in experimental scenarios; moreover, compared with those of the traditional backward method, the computation time was significantly reduced and the conservation of mass was significantly improved. Thus, the proposed method is a fast simulation method for outdoor aerosol numerical prediction.

In order to solve the problem that aluminum coating on bolt surface may be uneven in thickness when aluminum paint was used to coat the bolts, the influence of spraying angle on the uniformity of bolt surface coating is researched in this thesis. Nozzles and bolts of the spraying system were modeled and the computational fluid dynamics simulation software Fluent was used to establish the physical model of the gas-liquid two-phase flow of the atomization flow field. DPM model was used to analyze the interaction between the gas phase and the liquid phase in the flow field. Besides, the spray flow fields at different angles were obtained. The thickness of liquid film deposition on the bolt surface was also predicted and the spraying test system was set up. Results of this research were verified with the simulation results. The simulation and experimental results all show that the bolt surface coating is the most uniform when the spraying angle is 30°. [ABSTRACT FROM AUTHOR]

Copyright of South China Fisheries Science is the property of South China Fisheries Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Harbin University of Science & Technology is the property of Journal of Harbin University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The numerical simulation of surface tension is an active area of research in many different fields of application and has been attempted using a wide range of methods. Our contribution is the derivation and implementation of an implicit cohesion force based approach for the simulation of surface tension effects using the Smoothed Particle Hydrodynamics (SPH) method. We define a continuous formulation inspired by the properties of surface tension at the molecular scale which is spatially discretized using SPH. An adapted variant of the linearized backward Euler method is used for time discretization, which we also strongly couple with an implicit viscosity model. Finally, we extend our formulation with adhesion forces for interfaces with rigid objects. Existing SPH approaches for surface tension in computer graphics are mostly based on explicit time integration, thereby lacking in stability for challenging settings. We compare our implicit surface tension method to these approaches and further evaluate our model on a wider variety of complex scenarios, showcasing its efficacy and versatility. Among others, these include but are not limited to simulations of a water crown, a dripping faucet, and a droplet toy. [ABSTRACT FROM AUTHOR]

We present a framework that captures sparse Lagrangian flow information from a volume of real liquid and reconstructs its detailed kinematic information in real time. Our framework can perform flow reconstruction even when the liquid is disturbed by an object of unknown movement and shape. Through a large dataset of liquid moving under external disturbance, an agent is trained using reinforcement learning to reproduce the target flow kinematics with only the captured sparse information as inputs while remaining oblivious to the movement and the shape of the disturbance sources. To ensure that the underlying simulation model faithfully obeys physical reality, we also optimize the viscosity parameters in Smoothed Particle Hydrodynamics (SPH) using classical fluid dynamics knowledge and gradient-based optimization. By quantitatively comparing the reconstruction results against real-world and simulated ground truth, we verified that our reconstruction method is resilient to different agitation patterns. [ABSTRACT FROM AUTHOR]

When utilizing electrical discharge machining (EDM) for processing, the processing efficiency and quality will be significantly impacted, if the electrocorrosion residues in the gap flow field cannot be discharged in time. Numerical simulation is considered an effective means to simulate the flow field of EDM gaps. Based on simulation, this study investigates the processing time, depth, current, and dielectric (kerosene, water, and sunflower seed oil), on the movement of electrocorrosion residues within the dielectric. The simulation results demonstrate that an increase in processing time, current, or depth leads to a decrease in the escape rate of corrosion residues from the discharge gap. Compared with kerosene and sunflower seed oil, water has a higher residue escape rate, but the actual processing effect is not ideal. The escape rate of sunflower seed oil at any time was higher than that of kerosene,the highest was higher than 25%, and the average was higher than 22.21%. Sunflower seed oil can be used as a renewable dielectric to replace kerosene. Subsequently, verification experiments are conducted based on simulation results that demonstrate that the discrete phase model (DPM) fluid simulation exhibits excellent coupling with actual processing conditions. [ABSTRACT FROM AUTHOR]

The effects of mechanical energy input amount and input mode on the hydrophobic flocculation of coal particles in the stirring field were studied. Based on dimensional analysis, it was proved that the mechanical stirring speed can be used as the kinetic index of hydrophobic flocculation, and the mathematical expressions of floc formation and mechanical energy input were derived. Combined with the flotation tests, it was confirmed that the increase in stirring speed significantly promoted the hydrophobic flocculation of coal particles in a limited way. The full baffle stirred tank and three types of agitators, namely blade agitator, propeller agitator, and turbine agitator, were designed and manufactured. The turbulent kinetic energy and velocity distribution near the agitator were analyzed by fluid simulation, which showed that the axial flow field in the stirred tank was more conducive to the occurrence of flocculation. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Automobile Technology is the property of Automobile Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)