Search Results (1,007)

The present study examines the regulatory effects of laser heating parameters (power, position, and spot radius) on hydrothermal wave instability, heat and mass transfer, and interfacial deformation in bilayer thermocapillary systems under normal gravity. It provides theoretical support for the efficient utilization of energy and the optimization of industrial thermal systems, meeting the demands of sustainable development. The results show that increasing laser power induces asymmetric flow bifurcation nears the laser heating point, enhancing hydrothermal waves in the left region while suppressing them in the right region, with oscillation periods decreasing monotonically and amplitudes showing non-monotonic variation. Laser heating position alters convection intensity distribution, in which the convection in the hot zone is weakened as the laser point nears the cold end, while the convection in the cold zone is strengthened as the laser point nears the hot end. Reducing spot radius significantly decreases temperature gradients near the interfacial heat source, while attenuating horizontal velocity amplitude and increasing oscillation period, effectively suppressing oscillatory thermocapillary convection. This study demonstrates that precise control of laser heating parameters can effectively suppress thermocapillary instability and optimize heat transfer without introducing additional mechanical disturbances. It provides a theoretical basis for efficient, low-energy, non-contact thermal flow control technologies. Full article

Supercritical heat transfer in regenerative cooling channels is strongly influenced by thermophysical property variations near the pseudo-critical temperature, yet their direct implications for cooling performance have not been fully addressed. This study investigates how incorporating supercritical property considerations into surrogate fuel formulation affects heat transfer behavior in a regenerative cooling channel. RP-3 surrogate fuels were constructed using a genetic algorithm by matching both temperature-independent properties and temperature-dependent properties under supercritical conditions. Unlike previous approaches employing distillation curves as a secondary objective, the present formulation adopted supercritical density distribution and pseudo-critical temperature (T_pc) as optimization targets. The formulated surrogate fuels were evaluated in a regenerative cooling channel model surrounding a combustor, and their flow and heat transfer characteristics were compared with those of literature-based surrogate fuels. The results show that differences in T_pc and density variation trends significantly influence buoyancy-induced asymmetric flow structures and the onset of heat transfer deterioration. Surrogate fuels with lower T_pc exhibit earlier density reduction and earlier development of asymmetric flow, whereas fuels with higher T_pc demonstrate relatively mitigated wall temperature rise. The results of the present study suggest that surrogate fuel formulation based on supercritical thermophysical properties can have a significant influence on the predicted heat transfer behavior in regenerative cooling channels under the operating conditions considered. Full article

Dynamic umbilicals, as critical components connecting offshore platforms to subsea production systems, can effectively decouple platform motions through a lazy-wave configuration, thereby reducing top tension and fatigue damage. To address the engineering challenges of numerous configuration design variables and time-consuming dynamic analyses for dynamic umbilicals, an efficient design optimization framework based on surrogate modeling and multi-objective optimization is proposed. An integrated finite-element model of a lazy-wave dynamic umbilical–offshore platform system is developed in OrcaFlex, incorporating environmental loads, material properties, and geometric parameters. The arrangement parameters of clump weights and buoyancy modules are selected as design variables, and the dynamic responses and parameter sensitivities of multiple configurations are investigated. Using simulation data, surrogate models for predicting tension and curvature are constructed via random forest regression, achieving coefficients of determination (R²) of 0.9948 and 0.9121 on the test set, respectively. Based on the surrogate predictors, the Non-dominated Sorting Genetic Algorithm II (NSGA-II) is employed to solve a multi-objective optimization problem that minimizes the maximum tension and curvature, yielding a set of Pareto-optimal solutions. The proposed approach effectively improves the stability and reliability of the dynamic umbilical system under complex sea states. Full article

Push–pull exhaust systems are widely applied for controlling industry-processing fumes, and their performance is fundamentally governed by the coupling interaction among the air-curtain jet (“push”), the buoyant thermal plume generated by the heat source, and the converging flow induced by the exhaust hood (“pull”). However, the dynamic characteristics and design criteria of this coupled flow field under large temperature differences remain insufficiently explored. Here, a series of scaled experiments combined with numerical simulations is conducted to systematically investigate the coupling behavior of the air-curtain jet and the thermal plume, and two quantitative performance indicators, namely plume deflection height and flow rate along the plume deflection path, are proposed to evaluate flow control effectiveness and energy dissipation. An orthogonal experimental design is further employed to analyze the sensitivity of heat-source and air-curtain parameters with respect to these indicators. The results demonstrate that the air temperature reaches its maximum at approximately 0.8 m downstream of the air-curtain outlet, and that both the supply velocity and outlet width of the air curtain are dominant parameters exerting statistically significant influences on plume deflection height and flow rate along the path (p < 0.01). Furthermore, the Archimedes number effectively characterizes the competition between jet inertia and plume buoyancy in the coupled flow field, with its appropriate value preliminarily recommended to be controlled below 40. This study provides quantitative insights for the engineering design of push–pull exhaust systems operating under high thermal load conditions. Full article

Because dust-emission processes driven by local, small-scale winds (e.g., terrain-induced winds) are difficult to accurately capture with mesoscale or larger-scale predictive models, this study employed a CFD-Lagrangian particle-tracking approach to numerically simulate near-surface dust release and transport under different atmospheric stability conditions in the same local flow field. The novelty of this work was the integration of MOST-based stable/neutral/unstable inflow construction with Lagrangian particle tracking, enabling a consistent comparison of stability effects within one framework. This framework is useful for assessing local blowing-sand impacts on short-range receptors. A near-surface source term was specified for PM10-class mineral dust, and particles were emitted using a vertically exponential allocation. Simulations were conducted over a kilometer-scale flow domain containing an idealized cosine hill, and the low-level concentration patterns and dispersion-height variations in the resulting dust cloud were analyzed. Compared with neutral conditions, stable stratification produced higher near-surface concentrations and a lower dispersion height, whereas unstable stratification yielded lower near-surface concentrations and a higher dispersion height; as the $\left|L\right|$ increased, the unstable cases gradually approached the neutral state. The influence of reference wind speed exhibited clear stability dependence: under stable conditions, stronger winds intensified the buoyancy-related suppression of dust dispersion, while under unstable conditions, stronger winds inhibited the vertical spreading of the dust cloud. In addition, reduced air density representative of plateau environments resulted in lower dust-cloud concentrations and higher dispersion heights. These findings highlight the coupled effects of stratification and wind speed on near-field dust dispersion and provide a reference for assessing local dust emissions over complex terrain. Full article

Dissemination of unit of mass is one of the key processes in mass metrology and involves a large number of measurements to determine the mass of weights across a wide range (e.g., 1 mg–10 kg in the case of the Czech Metrology Institute, CMI). Evaluation of such measurements can be challenging, and to address this, the European Metrology Programme for Innovation and Research (EMPIR) project 19RPT02 “Improvements of the realisation of the mass scale” developed RealMass software solution (currently available in version 1.1) and a draft calibration procedure. However, standard procedures usually assume either identical densities of the weights or use the volume of the weights for buoyancy correction. In the latter case, if the volume is not known, the usual approach is to estimate it by dividing the nominal mass by the density. If the weights differ in either volume or density, these procedures lead to incorrect results. CMI developed a model and evaluation script to address these issues. The comparison data show that the developed model is consistent with the results obtained by RealMass software and other examples. The examples given in the text show how incorrect assumptions can lead to incorrect results and how they are evaluated by the approach presented in this paper. Full article

The short service life of oil fields and limited oil deposits in shallow waters requires a constant search for new oil fields in deeper waters. Compliant towers are one of the most suitable structures for water depths between 300 m and 600 m, where fixed structures are economically unfeasible. The principal characteristics of compliant towers include a minimal number of cross sections in their main structural elements throughout their height, combined with significant flexibility and buoyancy. Due to their flexibility and buoyancy, gravitational loads at the deck do not significantly impact the foundation. Moreover, compliant towers do not need advanced building systems, installation processes or special maintenance. Additionally, the large height of compliant towers reduces their natural frequencies, which prevents them from being within the frequency range of environmental forces capable of producing structural resonance. For this reason, efforts are made to design compliant towers to be as flexible as possible. Hence, this research is focused on examining a methodology for the structural analysis of compliant towers at ultimate and serviceability limit states for a water depth of 550 m in the Mexican waters of the Gulf of Mexico. Full article

Background/Objectives: This study systematically synthesized the evidence on the effectiveness of aquatic exercise (AE)-based interventions for improving sleep quality in patients with chronic diseases and identified key moderating factors. Methods: A meta-analysis of 11 randomized controlled trials sourced from Google Scholar, PubMed, Web of Science, Embase, Cochrane Library, and Scopus (published between 2016 and 2025) was conducted. Sleep quality was assessed using subjective tools (e.g., PSQI). Results: While AE-based interventions showed potential for enhancing nighttime sleep quality (standard mean difference = 0.825, p < 0.001), high statistical heterogeneity (I² = 93.41%) was observed. Given this variance, the analysis prioritized the clinical outcomes of specific patient populations over the pooled effect size. Preliminary evidence suggests significant improvements were confirmed in populations with post-COVID syndrome (p < 0.001), Parkinson’s disease (p = 0.002), and chronic back pain (p = 0.008). Conversely, no significant benefits were observed in fibromyalgia (p = 0.191), ankylosing spondylitis (p = 0.737), or type 2 diabetes (p = 0.836). Moderator analysis further indicated that the mode of AE might influence outcomes, with recreational aquatic therapy and deep-water running suggesting superior efficacy compared to resistance training. Conclusions: AE-based interventions were suggested as an effective intervention for improving sleep quality. The observed benefits likely stem from the synergistic effects of physical exercise and the unique physiological properties of the aquatic environment, such as buoyancy and hydrostatic pressure. However, the field relies heavily on subjective questionnaires and lacks physiological mechanism studies. These findings provide a preliminary evidence-based framework for clinicians to develop targeted AE-based interventions for chronic disease patients. Full article

The stability analysis for isothermal three-component gas mixtures, in which one of the components exhibits real properties in the considered pressure range, is performed. The system of Navier–Stokes and diffusion equations in the Boussinesq approximation is considered, taking into account analogs of buoyancy effects in a density-stratified medium. The presented solution is obtained by the small-perturbation method using the principle of diffusion independence, while maintaining the condition of neutrality of convective perturbations. Expressions for the boundary between the “diffusion–gravitational convection” regimes are obtained in terms of partial Rayleigh numbers that account for the compressibility factor of the mixing components. The stability cartograms show that on the stability maps, the position of the boundary of the regimes change depends on the variation in the compressibility factor with a pressure change. When the compressibility factor changes, the values of the critical Rayleigh numbers, which are the intersection points of the boundary of the regimes change and the coordinate axes, decrease. It is established that the behavior of the partial Rayleigh numbers on the plane (Ra₁, Ra₂) is nonlinear for isothermal ternary mixtures, which have the general form H₂ + N₂O–N₂ and He + CO₂–N₂, He + R12–Ar, at T = 298.0 K and elevated pressures. It is revealed that when taking into account the compressibility factor of the components, the partial Rayleigh numbers of the components decrease. Full article

While dissolution dominates the genesis of karst systems, physical erosion processes also play a significant role in their development. Lowering of the water table exposes caves to vadose conditions, reducing roof-supporting buoyancy and potentially leading to catastrophic conduit ceiling failure and cave collapse. The locations and extents of collapse areas are not always identifiable at the landscape surface. High-resolution topographic data derived from LiDAR were used to develop a digital elevation model (DEM) that isolates areas that may have sustained episodes of cave collapse and improves our understanding of past hydrogeological and geomorphological conditions of the system. Cave level delineation from LiDAR data was used to assign elevations to cave entrances. Spatial susceptibility to past collapse was evaluated using a weighted multi-criteria analysis that integrated terrain slope, proximity to mapped cave entrances, and distance to surface streams. Areas identified as having a high likelihood of collapse spatially coincide with cave level contacts and known karst windows and terraces, indicating that this replicated methodology is effective as an initial survey tool for identifying collapse-prone areas in karst landscapes. Full article

Numerical results are presented for a morphology fitted to a passive solar chimney attached to a room coupled with an earth-air heat exchanger. The effects of the variable thermophysical properties of air are included in the modelling. The considered operating mode is room cooling (summer ventilation) by means of an incoming airstream drawn from the soil at a temperature lower than that of the ambient. Buoyancy is assumed to be the only driving force acting on the fluid. A wide range of irradiance over the solar chimney walls, from 10 to 1000 W/m² (Rayleigh number based on the glazing wall from 1.77 × 10¹¹ to 1.77 × 10¹⁴), is analyzed. The impact of the incoming airstream temperature on the overall dynamic and thermal behavior of the system is studied. The induced mass-flow rate and average Nusselt number are presented as a function of relevant parameters for evaluating the passive device performance. The results reveal a strong influence of temperature and the position of the incoming cool airstream on room cooling. Some opposite effects on the relevant parameters are detected, but a sizeable increase in ventilation within the room for the middle and upper positions of the incoming duct is highlighted. Full article

Accurate identification of hydrodynamic parameters is essential for high-fidelity modeling and control of unmanned underwater vehicles (UUVs). Compared with towing tank experiments and computational fluid dynamics simulations, system identification based on free-running trial data offers a cost-effective and scalable alternative. However, in real ocean environments, unmodeled lumped disturbances—such as shear currents, stratification-induced buoyancy variations, and wave-induced drift forces—strongly couple with the vehicle’s intrinsic dynamics. Conventional least-squares estimators and physics-informed neural networks tend to absorb environmental effects into the physical parameters, leading to physically inconsistent estimates. To address this challenge, this paper proposes a physics-guided hybrid network (PG-HyNet) with input-domain structural decoupling. The architecture explicitly separates the intrinsic rigid-body dynamics from spatially varying environmental disturbances by assigning dynamics-related states to a physics-constrained branch and position-dependent variables to a residual disturbance branch. A staged training strategy is introduced to stabilize identification and suppress parameter drift during optimization. The framework is validated using high-fidelity simulations incorporating shear currents, density stratification, and wave drift effects, as well as real-world lake trial data. The results demonstrate that PG-HyNet significantly improves robustness against disturbance-induced parameter compensation, enabling physically consistent hydrodynamic parameter recovery while accurately capturing spatially varying environmental disturbance effects. Full article

The first application of theory of the rise of line thermals was to understand the rise of turbulent smoke plumes emitted from smoke stacks into a cross-wind. Initial solutions required numerical calculations. In this article analytical solutions are found, and these are used here to explore solutions for the rise of buoyant line wakes from submarine vehicles. Solutions cater for wakes in both neutral and stable environments, and for sources which have either negative or positive initial buoyancy. Account is also taken of sources with differing size and initial momentum. Practical examples of submarine thermal wake flows are given using neutral and typical stably stratified upper ocean conditions and a range of source conditions. A key result is that small-diameter submarine wakes with high temperatures produced in weakly stratified ocean waters will have a large height of rise, and may easily reach the surface. By contrast, large-source-diameter wakes, with temperatures close to ambient and emitted into strongly stratified oceans, will have very small heights of rise. Full article

This study presents and systematizes a high-reliability measurement and technological dataset suitable for prediction-based validation of the Spent Fuel Interim Storage Facility (SFISF) of the Paks Nuclear Power Plant. The primary objective of this dataset is not the validation of a general-purpose software tool, but to establish a reproducible experimental basis for the objective and quantitative validation of a three-dimensional, facility-scale heat transfer and buoyancy-driven flow model of the SFISF, developed using the finite difference method (FDM), in a passively cooled system where heat conduction, thermal radiation, and natural convection simultaneously occur. The applied measurement systems (SMAS, CTRS, and the in-house developed CFEPR), their spatial arrangement, accuracy characteristics, as well as data post-processing and the generation of model execution inputs are described in detail. Special emphasis is placed on the functional separation of the available data into initialization data, model execution data, and independent validation datasets, ensuring that model assessment does not rely on calibration or parameter fitting. Furthermore, the estimation of decay heat generated by the stored fuel assemblies is presented using both a standard correlation method (ANSI/ANS-5.1) and isotope inventory-based calculations, and the discrepancies between these approaches are treated as input uncertainties and sensitivity analysis factors. The spectral solar load is considered based on the ASTM G-173 reference spectrum, while during cloudy periods an effective irradiance estimation derived from on-site lux measurements is applied. The results indicate that the available measurement and technological information is sufficient for supporting reproducible, transparent, and quantitative validation studies of the three-dimensional numerical model of the SFISF, as well as for assessing the impact of dominant input uncertainties. Full article

Cyanobacterial blooms are intensifying globally under climate warming, eutrophication, and hydrological alteration, yet most mechanistic understanding derives from temperate lakes. Tropical and neotropical freshwaters operate under persistently warm conditions, weak seasonality, and hydrological variability that can sustain extended bloom windows and alter toxin production patterns spatiotemporally, requiring targeted synthesis. This review synthesizes recent experimental and field evidence, complemented by foundational frameworks, to evaluate cyanobacterial diversity, functional ecology, and cyanotoxin dynamics in tropical freshwater habitats. We highlight recurring trait syndromes, coordinated sets of physiological and functional traits, that recur across warm systems, including buoyancy regulation, diazotrophy, and thermal tolerance, which confer competitive advantages under warm, nutrient-rich conditions. These traits are prominent in dominant genera such as Microcystis, Raphidiopsis, and Planktothrix. We assess how temperature, nutrient stoichiometry, water residence time, and light interact to modulate bloom persistence and toxin production. We summarize appropriate monitoring and management approaches suited to warm, hydrologically dynamic basins. These including strategies addressing internal loading and integrated early-warning frameworks combining molecular tools and remote sensing. Substantial gaps persist in toxin quantification, biogeochemical fluxes, molecular surveillance, and coordinated risk assessment across the tropics. We argue that region-specific, integrative frameworks are urgently needed to improve early-warning capacity and mitigate cyanoHAB risks in tropical freshwater ecosystems. Full article