bluuebunny/crossref_metadata_2025 huggingface dataset:
Shallow water hydrodynamics: Surge propagation and sill-controlled flows
Authors: Cantero-Chinchilla Francisco Nicolás , Castro-Orgaz Oscar , Ali Sk Zeeshan , Dey Subhasish
Published: December 2024

Accurate flow models are crucial for simulating shallow water hydrodynamics, particularly in predicting and mitigating the impacts of extreme events involving free-surface flows. Many of these extreme scenarios in river environments involve fluid dynamics with significant dynamic pressures, invalidating the use of standard Saint-Venant-type models. This study presents a robust and accurate novel alternative based on the Reynolds-averaged Navier–Stokes (RANS) equations solved through variational methods. Despite their potential, variational methods have been underutilized in the literature, and their application has been limited to low-level expansions. Moreover, they are rarely validated against experiments that simulate complex flows. This study addresses both challenges. First, a general mathematical framework is developed for the variational RANS (VR) model of arbitrary high-level. The VR level III model is presented and is solved numerically using a robust finite volume-finite difference solver for turbulence flow modeling. Second, an extensive experimental program was conducted to validate this new flow modeling tool, focusing on two challenging flow scenarios. The first scenario involves the propagation of turbulent breaking waves over an irregular, uneven bathymetry—conditions similar to those observed during bedform development in riverine environments. This scenario involved the experimental characterization of unsteady surges over an array of obstacles in series. The second scenario investigated sill-controlled released discharges, similar to those occurring in estuary inlets with sediment bars. Comparisons between the new experimental data and the predictions from the VR level III model reveal the model's accuracy and robustness, making it a highly suitable tool for simulating free-surface flows.
High sensitivity direct magnetic field detection based metrology for ultra-thin magnetic films and Li-ion cells
Authors: Sharma Som Shekhar , Kurian K. K. George , Maity Dipak , Yadav Preeti , Narayanan Tharangattu N. , Rajalakshmi G.
Published: December 2024

Ultra-low magnetic field sensing is emerging as a tool for materials’ diagnostics, particularly for the operando studies of electrochemical systems. A magnetic metrology system having the capability of sensing fields as low as ∼1.88 pT has been setup for such studies using a commercial atomic magnetometer. The magnetometer setup is isolated from environmental perturbations, such as mechanical vibrations, electrical noises, and ambient magnetic fields, in order to measure small signals from the samples under study. Magnetic field measurements on ferromagnetic (permalloy, Ni0.8Fe0.2) thin films, monolayers of MoS2, vanadium doped MoS2, and lithium electro-deposited copper electrodes are performed to demonstrate the sensitivity of the setup. Magnetic field scanning of commercial Li-ion cells has also been performed using this magnetic metrology method, indicating the scope of the setup for operando diagnostics.
Immunogenic cell death-related cancer-associated fibroblast clusters and prognostic risk model in cervical cancer
Authors: Wu Fei , Xu Yue
Published: December 2024

Cervical cancer (CC) remains a leading cause of female cancer mortality globally. Immunogenic cell death (ICD) influences the tumor microenvironment (TME) and adaptive immune responses. Cancer-associated fibroblasts (CAFs) within the TME suppress anti-tumor immunity and contribute to CC progression. This study identified three ICD-related CAF clusters linked to patient survival, including IL6+CAF and ILR1+CAF, which were associated with clinical outcomes. Using a nine-gene risk model, patients were stratified into risk groups, with high-risk individuals showing worse survival and correlations with pathways such as hypoxia and TGFβ. The model also predicted immunotherapy responses, highlighting immune infiltration differences across risk groups. These findings provide insights into the role of CAF clusters in CC and present a risk model that supports prognosis prediction and personalized therapy.
Effects of a streamwise magnetic field on the exact coherent states in a channel flow
Authors: Wang Lebing , Li Sen , Shi Xiaomeng , Dong Shuai
Published: December 2024

This study provides a comprehensive investigation into the influence of a uniform, constant streamwise magnetic field on Exact Coherent States (ECS) in channel flows, an area unexplored within magnetohydrodynamic (MHD) research compared to spanwise or wall-normal magnetic field orientations. Utilizing direct numerical simulation and the standard bisection method, we examine ECS behavior across a range of computational domains with Reynolds numbers Re spanning from 3000 to 9000 and Hartmann numbers Ha ranging from 0 to 100. The results reveal a previously unobserved second saddle-node bifurcation of ECS with respect to Ha, occurring around Ha = 30 – 0.002Re for Re > 4000. This phenomenon is unique to the streamwise magnetic field configuration, and is absent under either spanwise or wall-normal magnetic fields. Additionally, the streamwise magnetic field prolongs the cycle time of relative periodic orbits (RPOs), contrasting with the cycle time reduction typically induced by other magnetic orientations, and induces a more gradual decay of streamwise perturbation energy, sustaining streamwise streaks in the channel flow. Furthermore, it is observed that, at Re = 6000 and Ha = 10, RPOs bifurcate into traveling waves (TWs) as the spanwise domain length Ly reaches approximately 2.683, with TWs remaining spanwise localized as Ly increases further.
Effects of droplet evaporation on turbulence characteristics in a supersonic mixing layer
Authors: Guo Zeqing , Li Haoyong , Dai Qi , Chen Zhihua
Published: December 2024

The effects of droplet evaporation on turbulence characteristics are systematically investigated in a three-dimensional spatially developing supersonic mixing layer at the convective Mach number of 1.2 via direct numerical simulation. With the point-particle approach, the fluid–droplet interactions are achieved through the two-way coupling in the Eulerian–Lagrangian frame. Two droplet-laden simulations with different diameters are conducted and compared with the droplet-free mixing layer, where the dispersion and evaporation of droplets, and the turbulent structures and fluctuations are analyzed. The droplets tend to accumulate in the peripheries of vortices with high density, low vorticity, and low temperature and show preferential concentration in the high-density regions behind shocklets on the cold side. Some droplets entrained into the mixing layer can collect in the vortex cores with high vorticity, where the droplets evaporate and absorb heat. Compared with large droplets, small droplets evaporate more rapidly and produce more vapor. Consequently, the vorticities and Reynolds stresses in the initial shear layer are enhanced by small droplets, but reduced by large droplets. Nevertheless, the small and large droplets both augment the turbulent structures and fluctuations in the fully developed region. Thus, the mixing layer thickness is enhanced with stronger turbulence anisotropy, and the degree of enhancement increases as the droplet size decreases. In addition, the droplet evaporation attenuates the density fluctuation, but augments the fluctuations of temperature and pressure. The vapor mass fraction fluctuation exhibits two peaks in the hot and cold stream, which are both enhanced with the decrement of the droplet diameter.
Measuring complex SFG: Characterizing a phase reference
Authors: Xiong Ziqing , Lynch Rebecca G. , Gubbins Emma F. , Shultz Mary Jane
Published: December 2024

Reactions and interactions at interfaces play pivotal roles in processes ranging from atmospheric aerosols influencing climate to battery electrodes determining charge–discharge rates to defects in catalysts controlling the fate of reactants to the outcome of biological processes at membrane interfaces. Tools to probe these surfaces at the atomic-molecular level are thus critical. Chief among non-invasive probes is the vibrational spectroscopy sum frequency generation (SFG). The complex signal amplitude generated by SFG requires techniques to interfere the unknown amplitude with a well-characterized one. An interferometric method is described to characterize the signal from any nonresonant reference material. The technique is demonstrated by measuring the phase of polycrystalline GaAs, chosen due to the strong signal and insensitivity to surface contamination. With a 515 nm visible field, the phase of GaAs is 54.5° ± 0.5°. The capability of choosing a reference based solely on its signal intensity enables probing a wide range of interfaces.
Transition metal atom supported on N-terminated diamond (100) surface as an efficient electrocatalyst for oxygen evolution and reduction reactions
Authors: Li Gaoxian , Wang Yuanhang , Gao Nan , Li Hongdong
Published: December 2024

To alleviate the increasingly serious energy issues, it is essential to develop highly efficient and stable electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). In this study, we employed density functional theory to investigate a broad spectrum of transition metal (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Mo, Ru, Rh, Ag, W, Ir, and Pt) atoms supported on N-terminated diamond (100) surface (TM@ND) as single-atom catalysts for their OER and ORR performances. TM atoms (Sc, Ti, V, Cr, Mn, Y, Zr, and Ir) show large binding energy with substrate and thermal stability, which is advantageous for electrocatalytic reactions. Especially, Ir@ND demonstrates high efficacy as an OER electrocatalyst, and Mn@ND is identified as an efficient ORR electrocatalyst, exhibiting the theoretical overpotentials smaller than 1 V. Consequently, it suggests that diamond-based catalysts could serve as promising candidates for energy conversion and storage applications.
Observation of a large stable anticyclone in rotating turbulence
Authors: Tumachev Daniil D. , Levchenko Alexanrd A. , Vergeles Sergey S. , Filatov Sergey V.
Published: December 2024

A new turbulent regime in a rotating liquid system was discovered experimentally. A cubic aquarium with an edge of 1 m was filled with distilled water and mounted on a rotating platform. Turbulence was excited by vertically non-homogeneous mixers mounted in the corners of the cube. At a fixed intensity of turbulence forcing, a certain range of aquarium rotation frequency was found, within which a stable large-scale anticyclone was observed in the center of the aquarium, around which a peripheral cyclonic current was formed. The parameters of the turbulent regime obtained were measured for different cube rotation frequencies. A model was proposed, according to which the anticyclonic flow is supported by absorption of inertial waves that propagate toward the vortex axis from the peripheral region and carry an anticyclonic angular momentum. Such a wave with a fixed frequency, vertical wave number, and axial number is absorbed at a certain distance from the vortex axis in the critical layer. On the contrary, waves that carry a cyclonic momentum are reflected and, hence, eventually transfer their angular momentum to the peripheral cyclonic current. This separation of waves in an ensemble leads to the formation of the tangential Reynolds stress, which maintains the anticyclone. The separation process has a general nature, meaning that this mechanism of the stress formation should be relevant in all rotating turbulent flows with an axially symmetric mean current.
Quantitative characterization of synergistic effect in CO2 storage and enhanced recovery systems with considering CO2–water–salinity–rock reactions
Authors: Hu Ting , Cui Yunfeng , Duan Binghong , Xu Baoju , Zhao Zhencheng , Deng Haiyang , Dindoruk Birol , Yang Tao , Rui Zhenhua
Published: December 2024

CO2 geological utilization and storage (CGUS) is one of the crucial steps to achieve carbon neutrality goals. Partial and permanent mineralization of CO2 is seen as a secure means of storage. However, the quantitative characterization of essential geochemical processes involving in carbon sequestration under realistic system conditions, are yet to be considered fully. As a result, we developed an optional CGUS simulator: (1) detailed geochemical reactions and mineralization capabilities, (2) CO2 oil water rock interactions, and (3) synergistic CO2 storage and utilization. Using the methodologies and tools developed, we studied and quantitatively characterized the synergistic effects of CO2 sequestration and geological utilization during the critical 30 year period of carbon capture, utilization and storage (CCUS) demonstration sites in China. The results indicated that even depleted oil reservoirs can be the favorable sinks of CO2 sequestration as the remaining oil phase can enhance the migration of CO2. Dissolution of CO2 in the oil and water phases is not a mutually exclusive process, and there is inherent thermodynamic equilibrium that exists between the phases, while contributions by each phase can be optimized: the oil saturation at the startup of the injection, porosity, and injection rate has impact on incremental recovery and amount of carbon sequestered; the single injection slug size has a completely opposite effect on the geological utilization and sequestration, which needs to be optimized for more practical situations. Reservoirs rich in Mg-bearing minerals are favorable to CO2 mineralization and make storage more permanent as they lead to stable mineralization as a result of reactions with CO2. This study provides the important guidelines to achieve both efficient sequestration and geological utilization to increase the subsurface storage capabilities today and as well as the near future.
A systematic study on the aerodynamic performance enhancement in H-type Darrieus vertical axis wind turbines using vortex cavity layouts and deflectors
Authors: Hosseini Rad Sina , Ghafoorian Farzad , Taraghi Morteza , Moghimi Mahdi , Ghoveisi Asl Fatemeh , Mehrpooya Mehdi
Published: December 2024

The advantages of vertical axis wind turbines (VAWTs) have increasingly been recognized as effective turbomachines. Nonetheless, significant challenges remain regarding their efficiency and operational range. One promising approach to enhance their aerodynamic performance is the integration of vortex cavities, which can contribute to improved operational efficiency. This study utilizes computational fluid dynamics (CFD) to analyze the placement of vortex cavities systematically. The research investigates different configurations, such as suction side layout (SSL) and pressure side layout within single, double, triple, and quadruple arrangements to forecast their effect on H-type Darrieus VAWT aerodynamic performance. The findings show that the optimal configuration, with a concentration of 0.2 and 0.8 C in SSL, led to a 25% increase in power coefficient (Cp) at the tip speed ratio (TSR) of 3.3. Conversely, the suboptimal configuration, with a concentration of 0.2 and 0.4 C in SSL, resulted in a substantial 54% decrease in Cp at the same TSR due to issues with flow separation and lack of flow attachment after the vortex cavity. To optimize efficiency within the high-TSR range, a double, top, and bottom deflector configuration has been developed. Findings indicate that incorporating the double deflector has broadened the rotor's operational range from TSR 3.5 to 4.2 and concurrently elevated the rotor efficiency to 86%.
Dynamics of wingtip vortex in natural samaras
Authors: Yogeshwaran Govindharaj , Rao Srisha M. V. , Jagadeesh Gopalan
Published: December 2024

Natural samaras are winged seeds that fall with very low descent velocity due to thrust forces generated by the autorotation of the seed. Engineering bio-inspired samaras has potential applications in the air-dropping of impact-sensitive payloads, which brings about the need to understand and model the flow field around it comprehensively. Previous studies focused on the local flow around the samara and explained the formation of the leading edge vortex, which is responsible for much of its thrust generation. Nonetheless, limited focus has been given to the dynamics of wingtip vortex, which are essential for accurately modeling induced velocity at the rotational plane. This study addresses this lacuna through an experimental investigation of the wake flow of natural mahogany samaras at steady-state, using particle image velocimetry (PIV) in a seeded glass chamber. By capturing PIV planes slicing through helical wingtip vortex, we accurately identify the vortex centers, circulation strengths, and demarcate the upstream region, wake core, vortex regions, and outer wake regions. These data allow for the first detailed measurement of induced velocity at the rotational plane of samara, with streamlines revealing that the samara operates in a windmill brake state, analogous to helicopter autorotation. This comprehensive wake analysis not only provides novel insights into the thrust mechanics of bio-inspired samaras but also lays the groundwork for a simplified mathematical model for rapid geometry estimation of bio-inspired samaras.
On the circulation prediction of shock-accelerated polygonal heavy gas cylinders
Authors: Deng Zhiwei , Guan Ben , Li Dongdong , Wang Ge , Zhang Bin
Published: December 2024

A modified theoretical model is presented to predict the circulation generation in the interactions of a shock wave with polygonal heavy gas cylinders. In the present work, numerical methods are used to examine the interactions of square-, circular-, and diamond-shaped cylinders that filled with SF6/air mixture under the impact of incident shock with Mach numbers ranging from 1.21 to 2.50. The evolution of shock wave systems, vorticity deposition, and cylinder deformation are demonstrated; the static area measurements resulting from the shock compression and hydrodynamic instabilities and circulation measurements calculated over the entire computational domain and cylinder interface region are analyzed. It is found that the initial cylinder geometry determines the shock refraction types, which in turn determines the vorticity deposition. Different from the circular-shaped cylinder, large vorticity deposition and thus large vortex pairs are concentrated at the corners of the square and diamond-shaped cylinders, so that inaccurate prediction of the original circulation model results. The geometry of the cylinders does not apparently affect the area variation driven by the wave system effect but does affect the area driven by the hydrodynamic instability effect, which can be well manifested by the fast interface diffusion at the late stage. For the square- and diamond-shaped cylinders, the previous circulation prediction is found to agree well with the simulated circulation deposited over the cylinder interface region rather than over the entire computational domain. Finally, a modified circulation model is proposed for the polygonal cylinders considering both the influence of large vorticity generation at interface corners and shock strength reduction. This model provides an interface circulation prediction with relative errors of 0.55%–6.24% and 0.12%–3.04% for the square and diamond-shaped cylinders, respectively.
Parameter optimization for natural gas hydrate solid fluidization
Authors: Zhang Geng , Li Jun , Yang Hongwei , Huang Honglin , Liu Gonghui , Wang Biao , Chen Mian
Published: December 2024

The marine shallow gas hydrate reservoirs consist mainly of non-diagenetic hydrates, characterized by shallow burial, weak cementation, loose mineral deposition, and fragility. By non-diagenetic, we mean hydrates that have not undergone significant post-depositional chemical or physical alteration processes, unlike diagenetic hydrates, which form through chemical and structural changes in sediments after their deposition. Conventional extraction methods for non-diagenetic hydrates often lead to uncontrollable and unsafe issues, such as gas collection challenges and leakage risks. To address these, this paper presents a gas–liquid–solid multiphase non-isothermal transient flow model incorporating hydrate phase transitions for the solid fluidization exploitation method. The model couples multiphase flow, heat, and mass transfer in the wellbore with a dynamic decomposition model for hydrate-bearing particles. An optimization method for key parameters in hydrate solid fluidization is also proposed. The results show that the critical depth of hydrate decomposition increases over time, with a rising gas phase volume fraction. Increasing mining rate, seawater temperature, and salinity accelerates decomposition, while adjusting wellhead pressure controls the decomposition depth. Higher mining rates, seawater temperature, and salinity enhance gas production, while greater wellhead pressure and larger wellbore diameters boost solid production. These findings provide key insights for the safe and efficient transport of hydrate-bearing particles and advancing solid fluidization technology.
The effects of aspect ratio on the heat transfer characteristics of boiling mini-channel flow
Authors: Lu Wei , Chen Yujie , Zhang Benxi , Yu Bo , Sun Dongliang , Wang Bohong , Yang Yanru , Wang Xiaodong
Published: December 2024

Flow boiling demonstrates superior heat transfer performance and holds significant potential for thermal management applications. In this study, the great effects of aspect ratios of mini-channel on flow boiling heat transfer are reported by the numerical simulation method. Regarding the heat transfer coefficient (HTC), a boiling number threshold of 5.0 × 10−4 is obtained. Below this value, bubble detachment is not yet constrained by the channel, reducing the dry patches and providing better heat transfer at larger aspect ratios. Above this threshold, boiling becomes more intense, bubble size increases, making detachment easier in smaller aspect ratios, which show superior heat transfer performance. For the critical heat flux (CHF), at a flow rate of 0.1 m/s, the CHF for smaller aspect ratios is 77.78% higher than for larger aspect ratios. As the flow velocity increases, inertial forces begin to dominate bubble behavior, reducing the influence of channel size effects, and the differences in CHF gradually decrease. When the flow velocity exceeds 0.5 m/s, bubble behavior becomes similar, and the difference in CHF drops to less than 10%. This research highlights key parameters for optimizing mini-channel design, promoting the refinement and development of mini-channel structures.
Water nanodroplets freezing and ice crystal formation on subcooled surfaces
Authors: Yang Jing-Jing , Wang Bing-Bing , Wang Xin , Xu Zhi-Ming , Zhang Ben-Xi
Published: December 2024

The freezing behavior of liquid water, resulting in solid phases such as glassy structures, hexagonal crystals, or cubic crystals, is influenced by surface supercooling. This study identifies three distinct freezing modes of water nanodroplets on platinum surfaces through molecular dynamics simulations. At surface temperatures below 175 K, water nanodroplets freeze into a solid phase characterized by a glassy structure. Between 176 and 195 K, nucleation begins within the amorphous solid, resulting in crystalline ice formations. In the temperature range of 196–209 K, nucleation and growth occur within the liquid nanodroplets, culminating in the formation of ice crystals exhibiting cubic and hexagonal morphologies. Interestingly, the water temperature rises by 20–37 K during ice crystal nucleation and growth, and the proportion of cubic ice relative to hexagonal ice decreases as the temperature rises. Additionally, a specific threshold involving molecular distance and kinetic energy is essential for the formation of regular ice crystals, thereby confining heterogeneous nucleation to a defined range of surface temperatures. This study offers valuable insights that could inform strategies for controlling ice crystallization in various applications.
Optimized neural network for supersonic isolator flow field prediction incorporating prior information and attention mechanisms
Authors: Han Yunxiao , Kong Chen , Wang Xuan , Chang Juntao
Published: December 2024

The rapid and accurate prediction of the flow field during supersonic isolator operation is crucial. Deep learning-based pressure monitoring during operation is an effective method for flow field prediction. A supersonic isolator flow field dataset was produced for a ground-based experiment with a variable incoming Mach number and back pressure. An approach for predicting the future flow field based on isolator pressure monitoring was proposed. A flow field prediction model incorporating long short-term memory, temporal convolutional network, and convolutional block attention module structures has been proposed. The performance of the proposed model was analyzed and compared with those of other time-series neural networks for flow field prediction. The location of the shock train leading edge was introduced as a priori information to enhance the model prediction performance. The impact of the weights associated with the a priori information in network training on the performance of the flow field prediction model was analyzed and discussed. This study presents an optimization scheme for neural network flow field prediction models specifically tailored for the supersonic isolator flow field prediction problem.
The shale gas flow in the complex porous media based on the lattice Boltzmann method
Authors: Li Zhenglan , Ma Haiji , Peng Yu , Wu Yijia , Wu Jiwei , Sepehrnoori Kamy
Published: December 2024

Due to the tightness of shale, its fluid microflow mechanism has always been a hot topic of research. The lattice Boltzmann method has become an effective way to study this mechanism in the gradual improvement over the past few decades. However, current research has not yet provided a unified analysis of various microscale effects and heterogeneity of porous media. By introducing regularization equations, correcting local Knudsen numbers, modifying boundary conditions, and combining with the generalization processing of microscale effects, this article proposes a fully coupled shale gas lattice Boltzmann model that includes all the above-mentioned factors. The simulation results show that the microscale effects will have a significant impact on gas flow when the pore diameter is below 10 nm. When the pore size is greater than 50 nm and the pressure is greater than 20 MPa, the influence of Knudsen diffusion can be ignored. Compared to Knudsen diffusion, surface diffusion requires lower pressure and smaller pores to manifest. The surface diffusion rate will reach its optimal state at a pore size of 5 nm and a pressure of 10–20 MPa. The impact of surface diffusion can be ignored when the pore size is larger than 20 nm.
Shock oscillation and fluctuation mechanisms of wall pressure on a V-shaped blunt leading edge
Authors: Li Shenghan , Yin Tong , Bai Ruijie , Yan Chao , Jiang Zhenhua
Published: December 2024

This paper studies the shock oscillation and the fluctuating behavior of wall pressure on a V-shaped blunt leading edge. Utilizing numerical simulation and the proper orthogonal decomposition technique, this study analyses the primary modes of shock oscillation and their effect on wall pressure for both a V-shaped blunt leading edge and an improved heat flux reduction configuration. The findings reveal that the shock interaction structures on these models are responsive to the downstream subsonic flow, thereby triggering two distinct oscillation modes: “swinging” and “breathing.” These modes drive the main shock interaction structure and the near-wall shock interaction structure in a quasi-periodic motion. Concurrently, the complex shock oscillation phenomenon exerts three distinct influences on wall pressure: the positional oscillation of the shock wave/boundary layer interaction structures, the instability of the shear layer bounding the supersonic jet, and the positional oscillation of the jet collision structure near the stagnation point. Furthermore, the study demonstrates that the improved heat flux reduction configuration is more effective at suppressing wall pressure fluctuations, indicating its potential value in designing hypersonic vehicles. This paper offers valuable insights into understanding shock oscillations and their effect mechanisms on wall pressure within hypersonic flows.
Toward physically realistic ablation modeling in direct simulation Monte Carlo
Authors: Hong Andrew Y. K. , Gallis Michael A. , Moore Stan G. , Plimpton Steven J.
Published: December 2024

The ablation of solid objects embedded in hypersonic flows can be simulated via the direct simulation Monte Carlo method. However, current ablation algorithms can suffer from numerical and geometric issues which distort the receding surface. This in turn can affect near-surface flow behavior and the overall ablation rate. To minimize these effects and enable more physically realistic ablation models, two algorithmic modifications are proposed here. The first is to store multiple values in each grid cell surrounding the surface so that the Marching Cubes algorithm (which triangulates the surface from the grid values) can be made more accurate. The second is to adjust grid values (due to collisions and reactions) in a mass-flux-preserving manner by decrementing multiple grid values simultaneously. Several ablation test cases are simulated to illustrate the effect of these enhancements.
Simulation of an anti-sloshing technique using floating foams based on the moving particle semi-implicit method—The discrete element method algorithm
Authors: Geng Chong , Wang Wen-Hua , Piao Tai-Wei , Chen Yu-Qing , Heng Meng-Yuan , Zhou Zi-Qi , Yu Xue-Jie , Huang Yi
Published: December 2024

The moving particle semi-implicit (MPS) method can simulate nonlinear, large-deformation fluid flows, and the discrete element method (DEM) is effective in modeling the interaction of solid bodies. Therefore, it is feasible to simulate the influence of floating foam balls on sloshing by establishing the coupling effect between solid and liquid phases. In this study, the MPS method, with an improved source term and the optimized DEM, is verified by simulations of sloshing and solid-body movements, respectively. The proposed coupling algorithm behaved with acceptable performance in the simulation of the dam break scenario involving multiple layers of solid cylinders. The sloshing numerical tests with floating foams are carried out to demonstrate the accuracy of the MPS-DEM coupling algorithm when the transient behavior is compared.
Influences of depressurization rate on natural gas hydrate production characteristics in stepwise depressurization: Two-dimensional experimental study
Authors: Yan Peng , Jiang Yujing , Ma Xianzhuang , Luan Hengjie , Shan Qinglin , Du Xiaoyu , Chen Hongbin , Chen Yongqiang , Li Xinpeng
Published: December 2024

The stepwise depressurization method offers substantial advantages in terms of mitigating the risk of pipeline blockages, ensuring production stability, and reducing environmental impact. This study employs a self-developed two-dimensional production simulation test system for natural gas hydrate. It enables precise control of depressurization rates through a servo system, allowing for stepwise depressurization within a single horizontal well at three different rates: high, medium, and low. The experiment investigates the temperature–pressure responses within the reservoir during the production, as well as gas production characteristics, including gas production and gas production rate. The results reveal that choosing a medium depressurization rate significantly increases gas production, achieving a gas production proportion of 59%. However, there is a considerable risk associated, with a peak gas production rate of 8.894 l/min, severely impacting reservoir stability and jeopardizing well control safety in the late-stage production. In the third depressurization stage, there is a relatively weak linear relationship between the normalized multiples of average gas production rate and depressurization rate, with the average gas production rate increasing to 5.78 times and 5.76 times the original rate when the depressurization rate is raised to 1.5 times and 3 times, respectively.
The effects of train blockage ratio and speed on power pack flow field under train passing through tunnel
Authors: Chen Chunjiang , Peng Zijian , Guo Yuhan , Zheng Qiyao , Zhang Qiyue , Li Zhuojun , Gong Peilin , Niu Jiqiang
Published: December 2024

Diesel trains have a wide range of applications, especially in nonelectrified mountainous regions with many tunnels, where the ventilation performance of the power packs is crucial to ensure the smooth operation of the trains in tunnels. The smoke emitted from the power packs affects indoor air quality through air conditioning units (ACUs) on the top of the train. In this study, the interest is to understand the flow field around the power pack at the bottom of the train and diffusion of smoke on the top of the train. Numerical simulations were conducted using the incompressible unsteady Reynolds-averaged Navier–Stokes and shear stress transport k-ω two-equation turbulence model along with the slip-mesh technique. The simulation method and parameter settings were verified based on experimental data. The results show that the upstream fan flow is greater than the downstream in the same power package. The downstream fan flow fluctuates to a greater extent. The increase in train speed leads to a decrease in the fan flow and has a greater impact on the upstream fan flow. The downstream smoke concentration in the same ACU intake in the head car tail car is greater than that in the upstream. Compared to the train speed, the blockage ratio has a limited effect on fan flow and smoke diffusion. Therefore, to optimize the ventilation performance, a priority should be given to the speed of the train.
Uncertainty quantification in the motion of a water-exit vehicle and analysis of the robustness enhancement characteristics of pressure-equalizing exhaust
Authors: Ma Guihui , Lu Chenxin , Fang Ming , Zhao Bin , Fan Shiqi , Zhou Qiang , Lu Jiaxing , Yao Xiongliang
Published: December 2024

In the presence of complex wave and current interactions, the carrying platform for a water-exit vehicle frequently exhibits random motions across all six degrees of freedom (6-DOF). The quantification of the robustness of the vehicle's motion under the perturbations induced by the platform's stochastic movements is of paramount importance. Additionally, it is crucial to conduct research into methods that may enhance the robustness of the vehicle's trajectory against such disturbances. In this study, we employ the non-intrusive polynomial chaos expansion for the uncertainty quantification analysis. We construct a sample space and utilize the least angle regression algorithm within the framework of compressed sensing to determine the polynomial chaos expansion coefficients. The research focuses on analyzing the uncertainties in the motion and attitude of a water-exit vehicle influenced by the random 6-DOF motions of the carrying platform. It also examines the mechanism by which pressure-equalizing exhaust contributes to the enhancement of robustness in multi-degree-of-freedom motions. The study performs a sensitivity analysis using the Sobol index to evaluate how the 6-DOF motions of the carrying platform affect the water-exit vehicle's attitude and the pressure inside the exhaust bubble. The study's results demonstrate that the water-exit vehicle undergoes pitch, yaw, and roll deviations attributed to the random 6-DOF motions of the platform. Importantly, the platform's pitch, heave, and forward velocity significantly influence the uncertainty bandwidth regarding the vehicle's pitch attitude. Upon water exit, the vehicle's pitch motion shows heightened sensitivity to the platform's forward velocity, whereas its sensitivity to the platform's heave and pitch motions declines. The roll, sway, and yaw motions of the carrying platform predominantly influence the radial dimension and shape of the exhaust bubble, explaining a significant portion of the variance in bubble pressure. The pressure-equalizing exhaust, which forms a gas film over the vehicle's surface, creates an “equal pressure and robustness” effect. This results in an ‘adaptive’ righting moment and enhances robustness against 6-DOF disturbances.
Hydrodynamic theory of premixed flames under Darcy's law
Authors: Rajamanickam Prabakaran , Daou Joel
Published: December 2024

This paper investigates the theoretical implications of applying Darcy's law to premixed flames, a topic of growing interest in research on flame propagation in porous media and confined geometries. A multiple-scale analysis is carried out treating the flame as a hydrodynamic discontinuity in density, viscosity, and permeability. The analysis accounts in particular for the inner structure of the flame. A simple model is derived allowing the original conservation equations to be replaced by Laplace's equation for pressure, applicable on both sides of the flame front, subject to specific conditions across the front. Such model is useful for investigating general problems under confinement including flame instabilities in porous media or Hele-Shaw channels. In this context, two Markstein numbers are identified, for which explicit expressions are provided. In particular, our analysis reveals novel contributions to the local propagation speed arising from discontinuities in the tangential components of velocity and gravitational force, which are permissible in Darcy's flows to leading order, but not in flows obeying Euler or Navier–Stokes equations.
Uptake of guideline-based testing for chronic viral hepatitis in Australian primary care: retrospective analysis of electronic medical record data
Authors: MacLachlan Jennifer H. , Allard Nicole , Tran Lien , Savage Amelia , Adamson Emily , Price Vanessa , Pearce Christopher , Dore Gregory J. , Cowie Benjamin C.
Published: December 2024

Background Diagnosis is essential for engagement in care for chronic hepatitis B (CHB) and chronic hepatitis C (CHC), however, many Australians remain undiagnosed, especially for CHB. Primary care represents an important setting for testing, and this study sought to examine coverage in a large representative cohort of patients. Methods We analysed retrospective data from the electronic medical records of active patients visiting 566 primary care clinics in Victoria, Australia. Pathology records were assessed to identify the proportion of patients with a record of CHB/CHC serology testing based on risk factors identified in national guidelines (ethnicity, Indigenous status, history of injecting drug use, diagnosed HIV, and/or indications of liver disease). Results Of 1,593,774 patients, 393,948 (24.7%) had an indication for testing for CHB and/or CHC, of which 150,821 (38.3%) had evidence of testing. This proportion was highest in patients with HIV (65.6%) or injecting drug use history (60.0%), and lowest for those whose Indigenous status/ethnicity indicated testing (38.2%) or with elevated liver enzymes (39.1%). The proportion with evidence of testing was only moderate among those with a cirrhosis diagnosis (48.6%) or probable cirrhosis based on laboratory testing (50.6%). Conclusions This analysis demonstrated considerable gaps in testing for CHB and CHC in a large population of patients, including many with evidence of cirrhosis, suggesting higher risk of adverse outcomes. Primary care practices should be supported to comprehensively offer testing for viral hepatitis, particularly where there is evidence of liver disease, and these findings should be used to guide future interventions.
Emergent polar order in nonpolar mixtures with nonreciprocal interactions
Authors: Pisegna Giulia , Saha Suropriya , Golestanian Ramin
Published: December 2024

Phenomenological rules that govern the collective behavior of complex physical systems are powerful tools because they can make concrete predictions about their universality class based on generic considerations, such as symmetries, conservation laws, and dimensionality. While in most cases such considerations are manifestly ingrained in the constituents, novel phenomenology can emerge when composite units associated with emergent symmetries dominate the behavior of the system. We study a generic class of active matter systems with nonreciprocal interactions and demonstrate the existence of true long-range polar order in two dimensions and above, both at the linear level and by including all relevant nonlinearities in the Renormalization Group sense. We achieve this by uncovering a mapping of our scalar active mixture theory to the Toner–Tu theory of dry polar active matter by employing a suitably defined polar order parameter. We then demonstrate that the complete effective field theory—which includes all the soft modes and the relevant nonlinear terms—belongs to the (Burgers-) Kardar–Parisi–Zhang universality class. This classification allows us to prove the stability of the emergent polar long-range order in scalar nonreciprocal mixtures in two dimensions, and hence a conclusive violation of the Mermin–Wagner theorem.
Time-dependent effect of FKBP12 loss in the development of dilated cardiomyopathy
Authors: Chan Joan A. , Munro Michelle L.
Published: December 2024

Hanna et al. reveal that early, but not late, developmental cardiac FKBP12 deficiency leads to dilated cardiomyopathy in the adult heart.
Path integral derivation of the thermofield double state in causal diamonds
Authors: Chakraborty Abhijit , Ordóñez Carlos R , Valdivia-Mera Gustavo
Published: December 2024

In this article, we adopt the framework developed by Laflamme (1989 Physica A 158 58–63) to analyze the path integral of a massless—conformally invariant—scalar field defined on a causal diamond (CD) of size 2α in 1+1 dimensions. By examining the Euclidean geometry of the CD, we establish that its structure is conformally related to the cylinder

S

β

1

⊗

R

, where the Euclidean time coordinate τ has a periodicity of β. This property, along with the conformal symmetry of the fields, allows us to identify the connection between the thermofield double (TFD) state of CDs and the Euclidean path integral defined on the two disconnected manifolds of the cylinder. Furthermore, we demonstrate that the temperature of the TFD state, derived from the conditions in the Euclidean geometry and analytically calculated, coincides with the temperature of the CD known in the literature. This derivation highlights the universality of the connection between the Euclidean path integral formalism and the TFD state of the CD, as well as it further establishes CDs as a model that exhibits all desired properties of a system exhibiting the Unruh effect.
A depth-averaged heart model for the inverse problem of cardiac electrophysiology
Authors: Lagracie Emma , Bourgault Yves , Coudière Yves , Weynans Lisl
Published: December 2024

The inverse problem of cardiac electrophysiology is notoriously ill-posed, but is nonetheless extremely useful. In particular, it is difficult to reconstruct the transmembrane voltage in the volume of the heart, since an infinite dimensional space of transmembrane voltages can produce the same observation on the body surface. A widely used alternative is to consider only the outer surface of the heart, the epicardium, and solve a Cauchy problem for the Laplace equation in the torso domain. However, this approach only allows reconstruction of the extracellular potential on the epicardium, thus missing the information contained in the volume of the heart and in the transmembrane voltage. We propose a new methodology for reconstructing activation maps from torso surface data, which incorporates information from the myocardial volume, while solving a surface problem on the heart. We formulate a static forward model, derived from the bidomain model, by averaging equations in the heart. The averaged equations are coupled with the usual Laplace equations in the surrounding domains. For solving the inverse problem, this «depth-averaged» forward model is used as a constraint in an optimal control problem that allows to recover depth-averaged transmembrane voltage and extracellular potential in the heart, corresponding to observations on the body surface. Activation maps are computed by post-processing the recovered signals in the heart. This method retains the ability to include the interactions between the heart, torso and blood cavities, while maintaining the simplicity of the usual inverse procedure. The inverse problem is solved with a simple linear system, using the Lagrangian formalism, and thus in a single iteration. We emphasize on the post-processing techniques for recovering activation maps. We observe that using a threshold on the transmembrane voltage allows to recover smoother and more accurate activation maps than with a maximal deflection method on the extracellular potential.
Energy and cost efficient manufacturing of uniform periodic nanostructures enabled by an adaptable beam flattening device
Authors: Yang Yin-Kuang , Wu Yu-Xiang , Lin Te-Hsun , Fu Chien-Chung
Published: December 2024

High-precision fabrication of nanoscale periodic structures is utilized in a wide range of applications, including wire grid polarizers, photonic crystals, and light-emitting diodes. Among the fabrication methods, laser interference lithography (LIL) is one of the most widely applied techniques for nanoscale periodic structures, due to its advantages of being maskless, low cost, having an infinite depth of focus, and the capability of large-area patterning with a single exposure. However, since LIL requires uniform illumination of the coherent laser light, the illuminating laser beam is typically expanded and only the central part with uniform intensity is used, rendering LIL low in energy efficiency. In this study, we introduced a simple and cost-effective design of beam-flattening device with tunable performance that improves the energy efficiency and throughput of LIL for fabrication of nanoscale periodic structures. The design of the device was based on thin-film interference, where device parameters were obtained from optimizing performance. The as-fabricated beam-flattening device demonstrated a 4-fold improvement in throughout, as compared to the conventional LIL method. The capability of fabricating large-area (2000 mm2) gratings demonstrated the scalability of our beam-flattening device. We expect our device to be readily integrable to LIL systems and applicable for a wide range of fabrication processes.