Search Results (446)

A review of the development of grid technologies and corresponding numerical approaches based on the lattice Boltzmann method (LBM) is performed in the present study. The history of the algorithmic development and practical applications is presented and followed by a short introduction of the basic theory of LBM, especially the classic lattice Bhatnagar–Gross–Krook LBGK D2Q9 model. In reality, all the different grid technologies reported aim to solve one but very important problem, the local grid refinement, which largely influences the stability, efficiency, accuracy, and flexibility of the conventional LBM. The improvement of these numerical properties after employing various grid technologies is analyzed. Several grid technologies, such as body-fitted grid, multigrid, non-uniform rectangular grid, quadtree Cartesian square grid, unstructured grid and meshless discrete points, as well as the corresponding numerical approaches are compared and discussed. Full article

Flapping foils, inspired by the wing motions of birds and the swimming mechanisms of aquatic animals, offer a promising alternative to traditional turbines for extracting renewable energy from ambient flows found in nature. This study employs an immersed boundary-lattice Boltzmann method (IB-LBM) to numerically investigate the energy extraction performance of multiple flapping foils at a Reynolds number of 1100. Two staggered foils are systematically studied to identify the optimum spatial arrangements needed to achieve high energy-harvesting performance. The results show that the wake of the fore-foil mainly contributes to the negative performance of the hind-foil due to the loss of streamwise flow velocity, and the interaction between the two foils can enhance the energy-harvesting performance of the system, but cannot fully alleviate the effects of flow velocity loss. Therefore, the staggered arrangements, which help the hind-foil shed the wake, are essential to improve the energy-harvesting performance of the hind-foil. Comparable performance for the hind-foil is achieved at a horizontal gap of $2.5c$ and vertical gap of $2.5c$ with c being the chord length of the foil. The scaled-up systems, including three-, five-, and seven-foil configurations, are examined with gaps of $2.5c$ (horizontal) and $2.5c$ (vertical), and the results show that such ‘V’-shaped arrangements of these foils can achieve high energy-harvesting performance, with an enhancement up to $10.7\%$ when seven foils are used, by utilizing the high mean streamwise velocity at the boundary of the leader’s wake, confirming the versatility of the optimum staggered arrangements for flapping-foil arrays. Full article

Background: Handgrip strength asymmetry is a critical yet underexplored basketball component. While the digit ratio (2D:4D) is linked to strength, its interplay with age, body composition, and biomechanics is unclear. This study aimed to quantify these independent and interactive effects on asymmetry in female basketball players. Methods: Maximum handgrip strength was measured bilaterally in three arm postures in 26 adolescent and adult players. Linear Mixed Model with a random intercept tested the effects. Results: Omnibus tests revealed no statistically significant main effects or interactions for age group, lean body mass (LBM), or 2D:4D ratio. However, a planned contrast showed that asymmetry was significantly lower in an overhead arm posture compared to an extended arm posture (p = 0.035). A simulation-based power analysis determined the study was significantly underpowered (11.5%) to detect small-to-medium interaction effects. Conclusions: While biomechanical position subtly modulates strength asymmetry, the influence of age, lean mass, and digit ratio may be negligible or require substantially larger samples to detect. Individual differences, which accounted for 57% of the variance, appear to be the dominant drivers of handgrip asymmetry in this athletic cohort, highlighting the complexity of strength imbalances and the critical need for adequately powered research in this domain. Full article

This study proposes a MPL (microporous layer)–GDL (gas diffusion layer) microstructure reconstruction method based on a novel random reconstruction algorithm. Then the Shan–Chen multi-component and multi-phase lattice Boltzmann method (SC-LBM) is used to systematically describe the influence of different contact angle distributions on the drainage characteristics of the GDL of proton exchange membrane fuel cells (PEMFCs). Meanwhile, the breakthrough time of liquid water, steady-state time, and liquid water saturation are compared. The results show that with the increase in contact angle, the time for the first droplet breakthrough and the steady-state time are significantly shortened, and the saturation of liquid water gradually decreases at the steady state, indicating that increasing hydrophobicity can effectively improve the drainage capacity of the GDL. Several double-gradient and three-gradient contact angle distribution schemes are studied, and it is found that the gradient structure with increasing contact angles along the direction of water flow will lead to prolonged steady-state time and elevated water saturation, which is not conducive to drainage. This study analyzes the drainage process under different wettability gradients considering aspects such as the droplet morphology evolution, flow path, and water distribution mechanism, clarifying the key role of gradient design in GDL water management. This work also provides a theoretical basis and design guidelines for wettability optimization in the GDL of PEMFCs. Full article

The Kuroshio Current’s flow velocity imposes exacting requirements on underwater vehicle propulsive systems. Ecological preservation necessitates low-noise propeller designs to mitigate operational disturbances. As technological evolution advances toward greater intelligence and system integration, intelligent unmanned systems are positioning themselves as a critical frontier in marine innovation. In recent years, the global research community has increased its efforts towards the development of high-maneuverability underwater vehicles. However, propeller design optimization ignores the key balance between acoustic performance and hydrodynamic efficiency, as well as the appropriate speed threshold for blade rotation. In order to solve this problem, the propeller design of the NACA 65A010 airfoil is optimized by using OpenProp v3.3.4 and XFlow 2022 software, aiming at innovating the propulsion system of shallow water agile submersibles. The study presents an integrated design framework combining lattice Boltzmann method (LBM) simulations synergized with fully Lagrangian-LES modeling, implementing rotational speed thresholds to detect cavitation inception, followed by advanced acoustic propagation analysis. Through rigorous comparative assessment of hydrodynamic metrics, we establish an optimization protocol for propeller selection tailored to littoral zone operational demands. Studies have shown that increasing the number of propeller blades can reduce the single-blade load and delay cavitation, but too many blades will aggravate the complexity of the flow field, resulting in reduced efficiency and noise rebound. It is concluded that the propeller with five blades, a diameter of 234 mm, and a speed of 500 RPM exhibits the best performance. Under these conditions, the water efficiency is 69.01%, and the noise is the lowest, which basically realizes the balance between hydrodynamic efficiency and acoustic performance. This paradigm-shifting research carries substantial implications for next-generation marine vehicles, particularly in optimizing operational stealth and energy efficiency through intelligent propulsion architecture. Full article

A combination of lattice Boltzmann method (LBM)-based computations and Lagrangian particle tracking simulations is presented to study the dispersion and clustering of inertial particles in a forced homogeneous and isotropic turbulent flow and to analyze the relative importance of the various forces acting on particles. The particle dynamics are investigated across a wide range of particle-to-fluid density ratios (from 0.01 to 1000) and Stokes numbers (from 1.4 × 10⁻⁶ to 55.4), at a Taylor microscale Reynolds number of 33.6. Particle clustering is quantified using Voronoï tessellations. Results confirm that clustering intensity is maximized at Stokes numbers around unity, where particles preferentially accumulate in low-vorticity regions. Particle dynamics within the turbulent flow considered here vary fundamentally with density and size, even among tracer-like particles. Low-density and neutrally buoyant particles mimic tracers via either velocity matching or acceleration balance, while dense particles follow inertia-dominated dynamics. Full article

Cadmium (Cd) accumulation by benthic organisms poses a significant threat to aquatic environmental safety. Both vegetation and water velocity in rivers could influence this process, yet their coupled interaction mechanisms remain unclear. This study used laboratory flume experiments to simulate four scenarios: static water (C0), pure water velocity (C+H), vegetation-water velocity (V+H), and coexistence of vegetation-water velocity-Corbicula fluminea (C. fluminea) (C+V+H). The dynamics of Cd release from sediment to overlying water and its bioaccumulation within C. fluminea were investigated. A mathematical model coupling Cd release, diffusion, and C. fluminea bioaccumulation was developed based on the lattice Boltzmann method (LBM). The results showed that compared to the non-vegetation group (C+H), the presence of vegetation (V+H, C+V+H) initially reduced sediment resuspension and Cd release. However, the turbulence induced by vegetation significantly increased the Cd diffusion coefficient and equilibrium concentration in the water. Consequently, Cd accumulation in C. fluminea within the vegetation-water velocity group (C+V+H) was significantly higher than in the pure water velocity group (C+H). The established LBM model exhibited good simulation accuracy (for overlying water Cd concentration: R² = 0.8201–0.942; for C. fluminea Cd concentration: R² = 0.7604–0.8191) and successfully reproduced the processes of Cd release and bioaccumulation under varying vegetation-water velocity conditions. This study elucidates the mechanism by which vegetation promotes Cd accumulation in C. fluminea by altering water velocity structure and diffusion characteristics, providing crucial theoretical parameters for multi-media migration and transformation models of heavy metals in complex water velocity environments and for early warning systems concerning Cd accumulation risks in riverine organisms. Full article

Background: Pre-season training is pivotal for optimizing athletic performance in collegiate basketball, yet the effectiveness of such programs in improving body composition (BC) under NCAA-mandated hourly restrictions remains underexplored. The aim of this study was to evaluate the impact of a four-week, NCAA Division II-compliant strength and conditioning (SC) program on BC in women’s basketball. Methods: Sixteen student athletes (20.6 ± 1.8 y; 173.9 ± 6.5 cm; 76.2 ± 20.2 kg) completed an eight-hour-per-week micro-cycle incorporating functional conditioning, Olympic-lift-centric resistance, and on-court skill development. Lean body mass (LBM) and body-fat percentage (BF%) were assessed using multi-frequency bioelectrical impedance on Day 1 and Day 28. Linear mixed-effects models were used to evaluate the fixed effect of Time (Pre, Post), including random intercepts for each athlete and covariate adjustment for age and height (α = 0.05). Results The LBM significantly increased by 1.49 kg (β = +1.49 ± 0.23 kg, t = 6.52, p < 0.001; 95% CI [1.02, 1.96]; R² semi-partial = 0.55), while BF% decreased by 1.27 percentage points (β = −1.27 ± 0.58%, t = −2.20, p = 0.044; 95% CI [−2.45, −0.08]; R² = 0.24). Height positively predicted LBM (β = +1.02 kg/cm, p < 0.001), whereas age showed no association (p > 0.64). Conclusions: A time-constrained, NCAA-compliant SC program meaningfully enhances lean mass and moderately reduces adiposity in collegiate women’s basketball athletes. These findings advocate for structured, high-intensity, mixed-modality training to maximize physiological readiness within existing regulatory frameworks. Future research should validate these results in larger cohorts and integrate performance metrics to further elucidate functional outcomes. Full article

A properly functioning capillary microcirculation is essential for sufficient oxygen and nutrient delivery to the central nervous system. The physical mechanisms governing the transport of red blood cells (RBCs) inside the narrow and irregularly shaped capillary lumen are complex, but understanding them is essential for identifying the root causes of neurological disorders like cerebral ischemia, Alzheimer’s disease, and other neurodegenerative conditions such as concussion and cognitive dysfunction in systemic inflammatory conditions. In this work, we conducted numerical simulations of three-dimensional capillary models, which were acquired ex vivo from a mouse retina, to characterize RBC transport. We show how the spatiotemporal velocity of the RBCs deviates in realistic capillaries and equivalent cylindrical tubes, as well as how this profile is affected by hematocrit and red cell distribution width (RDW). Our results show a previously unprecedented level of RBC velocity fluctuations in capillaries that depends on the geometric features of different confinement regions and a capillary circularity index $\left(I_{cc}\right)$ that represents luminal irregularity. This velocity fluctuation is aggravated by high hematocrit conditions, without any further effect on RDW. These results can provide a better understanding of the underlying mechanisms of pathologically high capillary transit time heterogeneity that results in microcirculatory dysfunction. Full article

Although the lattice Boltzmann method (LBM) is relatively straightforward, it demands a well-crafted framework to handle the complex partial differential equations involved in multiphase flow simulations. For the first time to our knowledge, this work proposes a novel LBM framework to solve Eulerian–Eulerian multiphase flow equations without any finite difference correction, including very-large-density ratios and also a realistic relation for the drag coefficient. The proposed methodology and all reported LBM formulas can be applied to any dimension. This opens a promising venue for simulating multiphase flows in large High Performance Computing (HPC) facilities and on novel parallel hardware. This LBM framework consists of six coupled LBM schemes—running on the same lattice—ensuring an efficient implementation in large codes with minimum effort. The preliminary numeral results agree in an excellent way with the reference numerical solution obtained by a traditional finite difference solver. Full article

The enduring manufacturing goals are increasingly shifting toward ultra-precision manufacturing and micro-nano fabrication, driven by the demand for sophisticated products. Unconventional machining processes such as electrochemical jet machining (ECJM), electrical discharge machining (EDM), electrochemical machining (ECM), abrasive water jet machining (AWJM), and laser beam machining (LBM) have been widely adopted as feasible alternatives to traditional methods, enabling the production of high-quality engineering components with specific characteristics. ECJM, a non-contact machining technology, employs electrodes on the nozzle and workpiece to establish an electrical circuit via the jet. As a prominent special machining technology, ECJM has demonstrated significant advantages, such as rapid, non-thermal, and stress-free machining capabilities, in past research. This review is dedicated to outline the research progress of ECJM, focusing on its fundamental concepts, material processing capabilities, technological advancements, and its variants (e.g., ultrasonic-, laser-, abrasive-, and magnetism-assisted ECJM) along with their applications. Special attention is given to the application of ECJM in the semiconductor and biomedical fields, where the demand for ultra-precision components is most pronounced. Furthermore, this review explores recent innovations in process optimization, significantly boosting machining efficiency and quality. This review not only provides a snapshot of the current status of ECJM technology, but also discusses the current challenges and possible future improvements of the technology. Full article

Fluids that exhibit self-rewetting properties, such as aqueous long-chain alcohol solutions, display a unique quadratic relationship between surface tension and temperature and are marked by a positive gradient. This characteristic leads to distinctive patterns of thermocapillary convection and associated interfacial dynamics, setting self-rewetting fluids apart from normal fluids (NFs). The potential to improve heat transfer using self-rewetting fluids (SRFs) is garnering interest for use in various technologies, including low-gravity conditions and microfluidic systems. Our research aims to shed light on the contrasting behaviors of SRFs in comparison to NFs regarding interfacial transport phenomena. This study focuses on the thermocapillary convection in SRF layers with a deformable interface enclosed inside a closed container modeled as a square cavity, which is subject to nonuniform heating, represented using a Gaussian profile for the heat flux variation on one of its sides, in the absence of gravity. To achieve this, we have enhanced a central-moment-based lattice Boltzmann method (LBM) utilizing three distribution functions for tracking interfaces, computing two-fluid motions with temperature-dependent surface tension and energy transport, respectively. Through numerical simulations, the impacts of several characteristic parameters, including the viscosity and thermal conductivity ratios, as well as the surface tension–temperature sensitivity parameters, on the distribution and magnitude of the thermocapillary-driven motion are examined. In contrast to that in NFs, the counter-rotating pair of vortices generated in the SRF layers, due to the surface tension gradient at the interface, is found to be directed toward the SRF layers’ hotter zones. Significant interfacial deformations are observed, especially when there are contrasts in the viscosities of the SRF layers. The thermocapillary convection is found to be enhanced if the bottom SRF layer has a higher thermal conductivity or viscosity than that of the top layer or when distributed, rather than localized, heating is applied. Furthermore, the higher the magnitude of the effect of the dimensionless quadratic surface tension sensitivity coefficient on the temperature, or of the effect of the imposed heat flux, the greater the peak interfacial velocity current generated due to the Marangoni stresses. In addition, an examination of the Nusselt number profiles reveals significant redistribution of the heat transfer rates in the SRF layers due to concomitant nonlinear thermocapillary effects. Full article

Porous media have great application prospects, such as transpiration cooling for the aerospace industry. The main challenge for the prediction of gas permeability includes the geometrical complexity and high Knudsen number of gas flow at the nano-scale to micro-scale, leading to failure of the conventional Darcy’s law. To address these issues, the Quartet Structure Generation Set (QSGS) method is improved to construct anisotropic and heterogeneous three-dimensional porous media, and the lattice Boltzmann method (LBM) with the multiple relaxation time (MRT) collision operator is adopted. Using MRT-LBM, the pressure boundary conditions at the inlet and outlet are firstly dealt with using the moment-based boundary conditions, demonstrating good agreement with the analytical solutions in two benchmark tests of three-dimensional Poiseuille flow and flow through a body-centered cubic array of spheres. Combined with the Bosanquet-type effective viscosity model and Maxwellian diffuse reflection boundary condition, the gas flow at high Knudsen (Kn) numbers in three-dimensional porous media is simulated to study the relationship between pore-scale anisotropy, heterogeneity and Kn, and permeability and micro-scale slip effects in porous media. The slip factor is positively correlated with the anisotropic factor, which means that the high Kn effect is stronger in anisotropic structures. There is no obvious correlation between the slip factor and heterogeneity factor. Full article

Understanding tortuosity is essential for accurately modeling fluid flow in complex porous media, particularly in the sub-surface reservoir rock; therefore, tortuosity estimation was evaluated using three approaches: Streamline streamline simulations via the Lattice Boltzmann Method (LBM), geometric pathfinding using Dijkstra’s algorithm, and empirical modeling based on pore-structure parameters. The analysis encompassed 1963 micro-Computed Tomography (micro-CT) images of Brazilian pre-salt carbonate and sandstone samples, with the effective porosity extracted from LBM velocity fields, isolating flow-contributing pores, establishing streamline tortuosity as the reference standard. Sandstones exhibited relatively narrow tortuosity ranges (Dijkstra: 1.29–1.75; Streamline: 1.18–2.61; Empirical: 1.18–4.42), whereas carbonates display greater heterogeneity (Dijkstra: 1.00–3.18; Streamline: 1.00–3.68; Empirical: 1.59–4.93). Model performance assessed using the corrected Akaike Information Criterion (AICc) revealed that the best agreement with the data was achieved by the semi-empirical model incorporating coordination number and minimum throat length (AICc = −113.11), followed by the Dijkstra-based geometrical approach (−99.74) and the empirical porosity-based model (202.23). There was a nonlinear inverse correlation between tortuosity and effective porosity across lithologies. This comprehensive comparison underscores the importance of incorporating multiple pore-scale parameters for robust tortuosity prediction, improving the understanding of flow behavior in heterogeneous reservoir rocks. Full article

Exercise training in extreme temperatures concurrent with hypohydration status may potentiate the development of acute kidney injury (AKI) in young, healthy persons. Background/Objectives: It is unknown how repeated training bouts in ambient higher temperatures and humidity may influence measures of AKI. The purpose of this study was to investigate hydration status and renal biomarkers related to AKI in NCAA Division I female soccer athletes during preseason conditioning. Methods: A convenience sample of n = 21 athletes were recruited (mean ± SEM; age: 19.3 ± 0.25 y; height: 169.6 ± 1.36 cm; mass: 68.43 ± 2.46 kg; lean body mass: 45.91 ± 1.13 kg; fat mass: 22.51 ± 1.69 kg; body fat %: 32.22 ± 1.32%). The average temperature was 27.43 ± 0.19 °C, and the humidity was 71.69 ± 1.82%. Body composition, anthropometric, workload, and 14 urine samples were collected throughout the preseason training period for urine specific gravity (USG), creatinine (uCr), cystatin C (uCyst-C), and neutrophil gelatinase-associated lipocalin (uNGAL) analyses. Results: Our investigation showed that, when compared to baseline (D0), the athletes maintained a USG-average euhydrated status (1.019 ± 0.001) and were euhydrated prior to each exhibition game (D5-Pre: p = 0.03; 1.011 ± 0.001; D10-Pre: p = 0.0009; 1.009 ± 0.001); uCr was elevated on D8 (p = 0.001; 6.29 ± 0.44 mg·dL⁻¹·LBM⁻¹) and D10-Post (p = 0.02; 6.61 ± 0.44 mg·dL⁻¹·LBM⁻¹); uCyst-C was elevated on D6 through D10 (p = 0.001; ~0.42 ± 0.01 mg·dL⁻¹); no differences were found in uNGAL concentration. The highest distance (m) displaced was found during exhibition games (D5: p = <0.0001; ~8.6 km and D10: p = <0.0001; ~9.6 km). During the preseason conditioning, the athletes maintained a euhydrated status (~1.019) via USG, an increase in uCr that averaged within a normal range (208 mg·dL⁻¹), and an increase in uCyst-C to near AKI threshold levels (0.42 mg·L⁻¹) for several practice sessions, followed by an adaptive decline. No differences were found in uNGAL, which may be explained by athlete variation, chosen time sample collection, and variation in training and hydration status. Conclusions: The athletes maintained a euhydrated status, and this may help explain why urinary markers did not change or meet the reference threshold for AKI. Full article