Search Results (12,358)

Relativistic heavy-ion collisions generate ultra-strong magnetic fields that interact with the quark–gluon plasma (QGP), a key focus of high-energy physics research. This study investigates QGP energy density evolution under time-dependent magnetic fields within a (1+1)D relativistic magnetohydrodynamic (RMHD) framework integrated with Bjorken flow. Three magnetic field temporal evolution models (Type-1, Type-2, Type-3) are analyzed for two different equations of state: (1) p = c_s ²e (simplified ultra-relativistic), and (2) p = c_s ²e − 2MB (simplified ultra-relativistic), and (2)  (magnetized conformal), incorporating a temperature-dependent magnetic susceptibility derived from lattice QCD. Results show that stronger magnetic fields consistently suppress QGP energy density decay, with suppression magnitude dependent on the magnetic field’s temporal profile. Ultra-relativistic fluids exhibit slowed energy decay due to magnetic pressure counteracting hydrodynamic expansion. In contrast, magnetized conformal fluids display faster energy dissipation under identical conditions, arising from the synergistic effect of enhanced magnetic fluid coupling, increased energy dissipation during interaction, and QGP’s perfect fluid expansion at elevated temperatures. Temperature-dependent magnetic susceptibility reveals a transition from diamagnetic (confined phase) to paramagnetic (deconfined QGP phase) behavior, introducing a feedback mechanism that strengthens energy retention at higher temperatures. This work clarifies the interplay between magnetic field dynamics, QCD phase structure, and hydrodynamic expansion, providing key observational signatures for distinguishing fluid types in heavy-ion collisions and advancing realistic modeling of magnetized QGP.  (magnetized conformal), incorporating a temperature-dependent magnetic susceptibility derived from lattice QCD. Results show that stronger magnetic fields consistently suppress QGP energy density decay, with suppression magnitude dependent on the magnetic field’s temporal profile. Ultra-relativistic fluids exhibit slowed energy decay due to magnetic pressure counteracting hydrodynamic expansion. In contrast, magnetized conformal fluids display faster energy dissipation under identical conditions, arising from the synergistic effect of enhanced magnetic fluid coupling, increased energy dissipation during interaction, and QGP’s perfect fluid expansion at elevated temperatures. Temperature-dependent magnetic susceptibility reveals a transition from diamagnetic (confined phase) to paramagnetic (deconfined QGP phase) behavior, introducing a feedback mechanism that strengthens energy retention at higher temperatures. This work clarifies the interplay between magnetic field dynamics, QCD phase structure, and hydrodynamic expansion, providing key observational signatures for distinguishing fluid types in heavy-ion collisions and advancing realistic modeling of magnetized QGP. Full article

Several studies have investigated counterflow and concurrent flow in channels separated by a membrane to simulate mass transfer through membranes; however, few of them have used computational fluid dynamics (CFD). The current study aimed to numerically simulate and physically describe the distribution of pressure and velocity in counter-current flow by solving Navier-Stokes (N-S) equations in the channel and membrane pores (vertical channels). This is in contrast to most previous studies, in which the channel flow was simulated using N-S equations while ultra-filtration membrane flow was simulated using Darcy’s law. Consequently, the current study was executed using a CFD simulation to achieve several significant features: avoiding the execution of experimental tests, reducing the effort of model design and the expense and time consumption of fabrication, and facilitating the easy observation of variations in the pressure and the horizontal and vertical velocity for each point in the model. Two-dimensional CFD methods directly simulated the flow in channels and membrane pores to solve the N-S equations for each point in the whole domain, for which the velocity (horizontal and vertical) and pressure were calculated. In the current study, it was found that the pressure decreased from the inlet to the outlet of the channel, the horizontal velocity decreased from the inlet to the middle of the channel length and then increased to the outlet of the channel, and the vertical velocity decreased from the inlet to the middle of the channel length (L/2) with an upward direction (positive) and from L/2 to the outlet of the channel with a downward direction (negative). The analytical solution (1D model) was used to validate a numerical simulation (CFD) for the current study, but there were slight differences in the results between them. The results were perfectly explored and displayed the flow distribution patterns inside the channels and the membrane pores (vertical channels). The current study model represents the hemodialysis process. Full article

To achieve high-precision and real-time quantitative evaluation of gas production in underground gas storage (UGS), this study focused on 11 typical injection-production wells in the Sudong UGS group. To address the common challenges posed by deviated well structures and complex wellbore temperature field distributions, a gas flow-rate calculation method based on Distributed Temperature-Sensing (DTS) data was developed. By standardizing the processing of multi-well temperature data, deviated wellbore trajectories were straightened to convert measured depth (MD) to true vertical depth (TVD). By incorporating a geothermal correction mechanism, temperature anomalies closely related to fluid flow were extracted, and a spatially unified temperature field model was constructed. On this basis, a “Dual-Point Temperature Difference Method” is proposed as a novel approach for single-well production evaluation. Based on thermodynamic phenomena such as the Joule–Thomson effect and expansion cooling, two critical sensing points, upstream and downstream of the production layer, were selected, with their temperature anomaly difference (∆T) serving as a sensitive indicator of flow rate variations. Combined with downhole pressure parameters and synchronized wellhead metering data, a nonlinear quantitative relationship model between ∆T and gas production rate Q was established, enabling accurate conversion of wellbore thermal response to macroscopic flow parameters. The results indicated that the gas production rates calculated by this method align well with traditional wellhead metering data, with errors maintained within engineering tolerances. Notably, the method demonstrates higher reliability and corrective capabilities in wells with drifting or faulty meters. This achievement breaks the reliance of traditional methods on specific layers or mechanical meters. It enables the effective application of multi-well, full-section, and non-contact temperature data in gas volume assessment. This research provides new technical support for dynamic monitoring, efficient operation, and remaining gas evaluation of UGS, offering significant prospects for engineering applications. Full article

Bone is a dynamic and multifunctional tissue that provides mechanical support, regulates mineral homeostasis, supports hematopoiesis, and relies on complex interactions among multiple cell types. The increasing incidence of bone-related diseases, such as osteoporosis, osteoarthritis, fracture non-union, and bone cancer, highlights the need for in vitro models that better reflect human bone physiology. Bone-on-a-chip technology, developed through advances in microfluidics, biomaterials, and tissue engineering, offers a promising approach to recreate key features of the bone microenvironment in vitro. By incorporating bone-mimicking materials, relevant bone cells, vascular components, fluid perfusion, and mechanical stimulation, these platforms allow more realistic investigation of bone remodeling, regeneration, disease mechanisms, and drug responses. In parallel, bone organoids and their integration with microfluidic chips have further expanded the capabilities of in vitro bone models by enabling the formation of self-organized, human-relevant bone tissues with increased cellular complexity. This review summarizes recent progress in bone-on-a-chip systems, including models for osteogenesis and bone regeneration, vascularized bone, bone marrow and hematopoietic niches, cancer bone metastasis, and mechanobiological studies. Key design principles, materials, cellular components, and applications in disease modeling, drug screening, toxicity assessment, and personalized medicine are discussed. Current challenges and future directions are also discussed to support the continued development of more physiologically relevant in vitro bone models. Full article

This study investigates the application of computational hemodynamic modeling, involving both FSI and CFD models, using SimVascular to simulate blood flow in the right pulmonary artery for patient-specific cardiovascular assessment. The artery’s three-dimensional geometry was reconstructed from a computed tomography (CT) image, and pressure measurements from a CardioMEMS™ device were used as clinical ground truth for validation. To represent the arterial hemodynamics, we initially formulated a fluid–structure interaction (FSI) approach to capture wall mechanics. However, given the high computational cost of fully patient-specific FSI simulations for routine clinical decision-making, we evaluated the validity of key simplifications by assuming rigid vessel walls coupled with a three-element Windkessel (3WK) model and applying a half-sine inflow waveform derived from the patient’s cardiac output. These simplifications yielded results with minimal error: the rigid-wall assumption introduced a 1.1% deviation, while the idealized waveform resulted in a 0.56 mmHg offset. Crucially, while wall rigidity was acceptable, we found that arterial compliance in the boundary conditions is non-negotiable; reducing the model to a pure resistance approach resulted in non-physiological pressures (130 mmHg). A subsequent parametric analysis examined how varying resistance (R) and compliance (C) distinctively alter the pressure waveform morphology. The results underscore the potential of combining remote monitoring data with validated computational simulations to deepen the understanding of cardiovascular dynamics and enhance diagnostic and therapeutic approaches for cardiovascular diseases. Full article

Precise drug delivery remains a critical challenge in nanomedicine, with conventional nanocarriers suffering from significant drug leakage during circulation, limited control over release kinetics, and a lack of temporal control. This study presents a computational design and multiphysics simulation of a Smart Biodegradable Nanosystem. Through COMSOL Multiphysics simulations encompassing heat transfer, mass diffusion, and fluid dynamics, we validated the theoretical feasibility of a seven-layer architecture. The computational model predicts that mapping a re-entrant auxetic metamaterial topology onto a spherical scaffold enables geometric locking under fluidic stress, theoretically minimizing drug leakage. Furthermore, modeled thermosensitive dynamic covalent bonds demonstrate highly controlled release kinetics. All performance metrics presented herein are derived from predictive mathematical modeling. Theoretical degradation profiles indicate complete breakdown within 90–180 days into endogenous substances. This simulation-based study establishes a rigorous theoretical blueprint to guide future empirical fabrication in precision nanomedicine. Full article

Accurate wind flow prediction is essential for various applications, including the placement of wind turbines and a multitude of environmental assessments. Traditionally this can be achieved by using time-consuming computational fluid dynamics (CFD) simulations on reanalysis data. This study explores the performance of an autoencoder (AE) and a variational autoencoder (VAE) in approximating downscaled wind speed and direction using real-world reanalysis data and reference geo- and vegetation data. The AE model was trained for 2000 epochs and demonstrates the ability to replicate wind patterns with a mean absolute error (MAE) of approximately −0.9. However, the AE model exhibited a consistent underestimation of wind speeds and a directional shift of approximately 10 degrees compared to CFD reference simulations. The VAE model produced visually improved results, capturing complex wind flow structures more accurately than the AE model. It mainly achieves better local accuracy and a reduced variance of the results. The overall result suggests that while autoencoders can approximate wind flow patterns, challenges remain in capturing the full variability of wind speeds and directions with sufficient precision. The study highlights the importance of balancing reconstruction accuracy and latent space regularization in VAE models. Future work should focus on optimizing model architecture and training strategies to enhance accuracy, prediction reliability and generalizability across diverse wind conditions and various locations. Full article

The present study demonstrates a step-by-step method for optimizing the outflow valve geometry and maximizing thrust generation. In this system, the skin-mounted OutFlow Valve (OFV) acts as a convergent–divergent nozzle and, as such, the De Laval nozzle equations are considered as guidance for the shape optimization. The performance of the skin-mounted flapped OFV optimized designs is assessed with a combination of analytical equations and Computational Fluid Dynamics (CFD) methods. The three-dimensional Reynolds-Averaged Navier–Stokes (RANS) yield reliable thrust recovery estimates and reveal key aspects of the aerodynamic flow behaviour through the valve, highlighting the interaction between the skin-mounted flapped OFV components. The results compare well with the analytical approach, providing a basis upon which a skin-mounted flapped OFV can be tailored for a specific mission. Full article

During multi-layer commingled production of coalbed methane (CBM), fluid interference induced by interlayer pressure differences is a major constraint on productivity, representing a dynamic coupling process of reservoir pressure, temperature, and deformation. To elucidate this mechanism, we constructed a four-layer superimposed reservoir physical model using a self-developed large-scale true triaxial multi-field coupling test system, which reflects the geological conditions of the Eastern Yunnan and Western Guizhou region. We precisely regulated interlayer pressure differences and monitoring multi-physical parameters in real time to analyze the dynamic evolution of reservoir temperature, pressure, and deformation fields. The findings reveal that: (1) Increased interlayer pressure difference intensifies fluid interference in low-pressure reservoirs, causing abnormal pressure buildup. For example, when the pressure difference rose from 0.2 MPa to 0.6 MPa, the maximum pressure increase in Reservoir I grew from 1.03 MPa to 1.13 MPa. (2) The high-pressure reservoir (Reservoir IV) remained largely unaffected throughout production, with its temperature decline rate consistently correlated positively with pressure difference, indicating a distinct response behavior. (3) Reservoir deformation correlates positively with initial pressure. When the initial pressure of Reservoir II increased from 1.2 MPa to 1.6 MPa, its volumetric strain rose from 1.81‰ to 2.21‰, attributable to the combined effects of matrix shrinkage, elevated effective stress, and desorption-induced thermal cooling. This study demonstrates how interlayer pressure differences regulate the coupled evolution of reservoir pressure, temperature, and deformation, providing experimental evidence and theoretical support for identifying interference mechanisms and optimizing development strategies in CBM commingled production. Full article

The widespread abundance of silicified wood and fossil leaves in southwestern Georgia is associated with the upper Miocene-lower Pliocene volcanic deposits of the Goderdzi Formation. Neogene volcanic terrains frequently preserve exceptionally detailed fossil records, providing valuable insights into ancient environments, climate regimes, and vegetational dynamics. Extensive upper Miocene volcanic activity produced thick pyroclastic deposits, lahar flows, and localized sedimentary basins that facilitated the rapid burial and preservation of diverse plant remains, including silicified wood and well-preserved fossil leaves. The mineralogy of Goderdzi Formation fossil woods is surprisingly complex, with compositions that include opal-A, opal-Ct, chalcedony, and microcrystalline quartz. These minerals are evidence of variations in hydrothermal fluid circulation that led to episodes of mineral precipitation that typically occurred in several discrete steps. Full article

Conventional thermoelectric generators (TEGs) suffer from thermal resistance introduced by ceramic substrates and thermal interface materials, which limits the achievable temperature gradient across the junctions and reduces conversion efficiency. To overcome this limitation, a pin-fin integrated thermoelectric device (iTED) is proposed, in which the hot-side heat exchanger is incorporated directly into the hot-side interconnector, eliminating the ceramic and associated greases. An explicitly coupled thermal-fluid-electric finite-volume model is developed in ANSYS Fluent’s user-defined scalar (UDS) environment to quantify the simultaneous thermal-fluid-electric behavior of the iTED for inlet temperatures of 350 $\le T_{\mathrm{in}}\mathrm{K}\le$ 650, Reynolds numbers of 3000 $\le \mathrm{Re}\le$ 15,000, and load resistances ranging from 0.01 to ${10}^6$% of the internal device resistance ($R_{\mathrm{int}}$), for a fixed cold-side temperature of 300 K. The model is validated against established tube-bank correlations (2.2% agreement in pumping power) and a one-dimensional Explicit Thomson Model (1.2–6.9% agreement across all electrical system response quantities). Compared with an equivalently sized conventional TEG, the iTED achieves a 4.6-fold higher maximum power output (23.9 [W] vs. 5.2 [W] at Re = 15,000), a 2.8-fold higher thermal conversion efficiency (8.1% vs. 2.9%), and a 4.8-fold higher performance index (7.8 [-] vs. 1.6 [-] at Re = 3000), all at $T_{\mathrm{in}}$ = 650 K. A performance index analysis reveals that lower Reynolds numbers and higher inlet temperatures maximize the net power benefit, delineating the operational envelope in which the iTED produces more electrical power than is needed for fluid pumping. These findings demonstrate that device-level restructuring—specifically, the elimination of interfacial thermal resistance via integrated pin-fin heat exchangers—can yield performance improvements comparable to or exceeding those achievable through material advances alone. Full article

Heart valve prostheses play a key role in regulating the normal cardiac function for patients with valvular diseases, yet even slight alterations in their flow dynamics can result in serious physiological consequences. This paper provides an overview of in vitro studies using Particle Image Velocimetry (PIV) to investigate the hemodynamics of heart valve prostheses. We first trace the historical evolution of prosthetic valve designs and highlight key milestones in their development. Key experimental considerations for PIV apparatus design are summarized. Subsequently, we review major in vitro PIV studies that have enhanced understanding of prosthetic valve hemodynamics, including flow patterns, turbulence characteristics, and flow–structure interactions. Finally, we outline current challenges and propose future research recommendations, highlighting the potential of integrating advanced PIV methods with high-fidelity imaging for improved assessment of prosthetic valve performances. Overall, the study of heart valve prostheses remains inherently complex due to the multiscale nature of hemodynamic phenomena. Recent advances in experimental fluid mechanics, particularly PIV, have significantly enhanced the ability to visualize and quantify the hemodynamics of prosthetic valves, providing valuable insights for optimizing design and improving the durability of next-generation valve prostheses. Full article

Navío Quebrado Lagoon is a shallow coastal waterbody connected to the Caribbean Sea through an inlet, and it lies within Colombia’s protected-area system, specifically, the Los Flamencos Flora and Fauna Sanctuary. In this work we set up the Environmental Fluid Dynamics Code Plus (EFDC+) model to examine salinity behavior across 2024, combining field measurements with hydrological, meteorological, and tidal datasets obtained from national monitoring agencies. Model calibration used RMSE, the Nash–Sutcliffe efficiency (NSE), and R², and the fit was consistent for both water levels and salinity. To isolate the role of lagoon–sea connectivity, we compared a reference run (real inlet dynamics) against three scenarios: (E1) the inlet kept permanently open, (E2) the inlet kept permanently closed, and (E3) a second inlet kept permanently open while the original inlet maintained its observed opening/closure behavior. Model results show that under the reference condition, salinity presented strong spatial and seasonal changes, with 164 consecutive days of critical hypersalinity events, with an annual range of 0 to 200 ppt. Scenarios E1 and E3 produced more favorable conditions by keeping lagoon salinity within 0–66.9 ppt and 0–44.5 ppt, respectively. In contrast, E2 substantially altered hydrologic conditions and significantly reduced lagoon water volume and salinity variability. Full article

Biological fish possess the intrinsic ability to dynamically modulate body stiffness to adapt to varying fluid environments, thereby optimizing propulsive efficiency, swimming speed, and maneuverability. In contrast, this capability remains a significant challenge for most existing robotic fish, which typically rely on fixed-stiffness configurations. This article presents a comprehensive review of variable stiffness structures and their applications in biomimetic robotic fish. The associated technologies are systematically classified into four categories: smart material-driven, bio-inspired, fluid-driven, and hybrid-driven mechanisms. A comparative analysis of state-of-the-art prototypes is conducted, evaluating critical performance metrics including physical dimensions, maximum swimming speed, minimum turning radius, maximum turning rate, and Strouhal number. Furthermore, the specific advantages and technical limitations of each variable stiffness category are critically assessed. Finally, existing challenges in current research are identified, and prospective directions are proposed. The review demonstrates that variable stiffness technology offers significant potential to advance the hydrodynamic performance of robotic fish and facilitate their deployment in practical engineering applications. Full article

A novel shallow oil chamber hybrid journal bearing with adjustable oil chamber depth was designed based on piezoelectric ceramics, inspired by conventional shallow oil chamber bearing structures. The computational fluid dynamics method is used to analyze the bearing characteristics of shallow oil chamber bearings, including the volume flow, the seal oil pressure, load capacity and stiffness. An experimental platform equipped with signal acquisition device and piezoelectric ceramic control device was developed. The eddy current sensors collected the displacement signal at the shaft end. The required voltage was calculated by the displacement signal. The piezoelectric ceramics elongated or shortened, causing a displacement of the same magnitude in the depth of the oil chamber, thereby controlling the radial displacement of the shaft. The adjustment effect of this bearing was verified by experiment for no-load and 500 N load at 200–1000 rpm, with a baseline initial oil chamber depth of 20 and an oil supply pressure of 2 MPa. The results showed that compared with the case without adjustment, the accuracy in Y direction has increased from 8.9 μm to 1.9 μm (max. 78.4%) after adjustment. Under the above load conditions, the displacement can be controlled below 2 μm, indicating a significant improvement in shaft vibration resistance. Full article