Search Results (140)

To address the issue of coating accumulation model failure in unstable environments, this paper proposes a dynamic control method based on visual differential feedback. An image difference model is constructed through online image data modeling and real-time reference image feedback, enabling real-time correction of the coating accumulation model. Firstly, by combining the Arrhenius equation and the Hagen–Poiseuille equation, it is demonstrated that pressure regulation and temperature changes are equivalent under dataset establishment conditions, thereby reducing data collection costs. Secondly, online paint mist image acquisition and processing technology enables real-time modeling, overcoming the limitations of traditional offline methods. This approach reduces modeling time to less than 4 min, enhancing real-time parameter adjustability. Thirdly, an image difference model employing a CNN + MLP structure, combined with feature fusion and optimization strategies, achieved high prediction accuracy: R² > 0.999, RMSE < 0.79 kPa, and σ_e < 0.74 kPa on the test set for paint A; and R² > 0.997, RMSE < 0.67 kPa, and σ_e < 0.66 kPa on the test set for aviation paint B. The results show that the model can achieve good dynamic regulation for both types of typical aviation paint used in the experiment: high-viscosity polyurethane enamel (paint A, viscosity 22 s at 25 °C) and epoxy polyamide primer (paint B, viscosity 18 s at 25 °C). In summary, the image difference model can achieve dynamic regulation of the coating accumulation model in unstable environments, ensuring the stability of the coating accumulation model. This technology can be widely applied in industrial spraying scenarios with high requirements for coating uniformity and stability, especially in occasions with significant fluctuations in environmental parameters or complex process conditions, and has important engineering application value. Full article

Since the beginning of the 21st century, the supercritical carbon dioxide (sCO₂) Brayton cycle has emerged as a hot topic of research in the energy field. Among its key components, the sCO₂ compressor has received significant attention. In particular, axial-flow sCO₂ compressors are increasingly being investigated as power systems advance toward high power scaling. This paper reviews global research progress in this field. As for performance characteristics, currently, sCO₂ axial-flow compressors are mostly designed with large mass flow rates (>100 kg/s), near-critical inlet conditions, multistage configurations with relatively low stage pressure ratios (1.1–1.2), and high isentropic efficiencies (87–93%). As for internal flow characteristics, although similarity laws remain applicable to sCO₂ turbomachinery, the flow dynamics are strongly influenced by abrupt variations in thermophysical properties (e.g., viscosities, sound speeds, and isentropic exponents). High Reynolds numbers reduce frictional losses and enhance flow stability against separation but increase sensitivity to wall roughness. The locally reduced sound speed may induce shock waves and choke, while drastic variation in the isentropic exponent makes the multistage matching difficult and disperses normalized performance curves. Additionally, the quantitative impact of a near-critical phase change remains insufficiently understood. As for the experimental investigation, so far, it has been publicly shown that only the University of Notre Dame has conducted an axial-flow compressor experimental test, for the first stage of a 10 MW sCO₂ multistage axial-flow compressor. Although the measured efficiency is higher than that of all known sCO₂ centrifugal compressors, the inlet conditions evidently deviate from the critical point, limiting the applicability of the results to sCO₂ power cycles. As for design and optimization, conventional design methodologies for axial-flow compressors require adaptations to incorporate real-gas property correction models, re-evaluations of maximum diffusion (e.g., the DF parameter) for sCO₂ applications, and the intensification of structural constraints due to the high pressure and density of sCO₂. In conclusion, further research should focus on two aspects. The first is to carry out more fundamental cascade experiments and numerical simulations to reveal the complex mechanisms for the near-critical, transonic, and two-phase flow within the sCO₂ axial-flow compressor. The second is to develop loss models and design a space suitable for sCO₂ multistage axial-flow compressors, thus improving the design tools for high-efficiency and wide-margin sCO₂ axial-flow compressors. Full article

A functional measure encompasses quantum corrections and is explored in the fluid/gravity correspondence. Corrections to the response and transport coefficients in the second-order dissipative relativistic hydrodynamics are proposed, including those to the pressure, relaxation time, and shear relaxation time. Their dependence on the quark–gluon plasma (QGP) temperature sets a temperature dependence on the running parameter encoding the one-loop quantum gravity correction, driven by a functional measure. The experimental range of the bulk-viscosity-to-entropy-density ratio of the QGP, obtained by five different analyses (JETSCAPE Bayesian model, Duke, Jyväskylä–Helsinki–Munich, MIT–Utrecht–Genève, and Shanghai) corroborates the existence of the functional measure. Our results suggest that high-temperature plasmas could be used to experimentally test quantum gravity. Full article

Field observations revealed that a mooring buoy rapidly drifts in a reciprocating motion along an arcuate path between two extreme positions. When the anchor point is considered the origin and viewed from an aerial perspective, this movement resembles a pendulum. The implications of this motion for data acquisition efficiency prompted our inquiry into this phenomenon. The comparative analysis of the model’s different movements under wave-only, current-only, and wave–current conditions demonstrates that currents are the source inducing this pendulum-like motion. To investigate the mechanism of this current-driven motion, the flow field around the buoy was visualized through numerical simulations. Specifically, the CFD results aligned with the field data and confirmed that periodic vortex shedding induces oscillatory forces, which dominate the rapid reciprocating movement. The findings emphasize the significant impact of fluid viscosity and the resulting vortex effects on the motion characteristics of buoys. They can provide a foundation for addressing more applied problems of data error-correcting and trajectory predictions. Full article

The purpose of this paper is to obtain a partial clustering model of viscosity including the influence of clusters. This paper also establishes a quantitative correlation between the dynamic viscosity of alloys and temperature of liquidus in isotherms. The research methods are a theoretical substantiation of possibility of the isolated use of the Boltzmann distribution (energy spectrum) for the kinetic energy of the chaotic (thermal) motion and particle collisions as applied to a condensed state of matter. In this paper, the author’s concept of chaotic particles is applied to substantiate the existence of an energy class of particles present in the liquid in the form of clusters. The novelty of the paper is that it obtains a quantitative physical and mathematical model of temperature dependences of the dynamic viscosity based on destruction of clusters as the temperature increases. The mathematical model is compared with viscosity data from the state diagram, starting from the liquidus barrier. This approach was developed first and allows constructing viscosity isotherms based on the thermochemical initial data with extrapolation to the region of ultra-high temperatures. The proposed new model is verified in an example of a Cu-Sn alloy. The high correlation coefficient indicates the correctness of the derived equations and possibility of predicting the distribution of the viscosity of the alloy at high temperatures based on its state diagram. But the main fundamental novelty of the work is the discovery of the relationship between the activation energy of viscous flow and the barrier of randomization, which is present in the partial clustering model. The application of the new partial clustering viscosity model can be utilized across various fields involving fluid dynamics. In our study, the practical implementation of this novel partial clustering viscosity model will ensure the effective execution of metallurgical processes designed using these values at extremely high temperatures, determine optimal operating conditions, and provide more substantiated requirements for metal and alloy production technologies. Full article

Large curvature, high pre-swirl large high-speed centrifugal fans are the preferred choice for industrial gas quenching furnaces, as they need to operate under non-uniform inlet conditions for extended periods. The resulting inlet distortion disrupts the symmetric flow of the gas, leading to reduced fan stability and phenomena such as flow separation and rotational stall. This issue has become a key research focus in the field of large centrifugal fan applications. This paper introduces an eddy viscosity correction method, and compares it with experimental results from U-shaped pipe curved flow. The corrected SST k-ω model shows a maximum error of only 4.7%. Simulation results show that the fan inlet generates a positive pre-swirl inflow with a relative distortion intensity of 3.83°. The flow characteristics within the impeller passage are significantly affected by the swirl angle distribution. At the maximum swirl angle, the leakage flow at the blade tip develops into a stall vortex that spans the entire passage, with an average blockage coefficient of 0.29. At the minimum swirl angle, the downstream leakage flow at the blade tip is suppressed on the suction side by the main flow, leading to a reduced vortex structure within the passage and an average blockage coefficient of 0.21. To address the design challenges of large high-speed centrifugal fans under inlet distortion, a blade design method based on secondary flow suppression is proposed. Eleven impeller flow surfaces are selected as control parameters, and the centrifugal impeller blade profile is redesigned. Numerical simulations and experimental results of the gas quenching furnace’s flow and temperature fields indicate that the modified impeller significantly reduces the blade tip leakage flow strength, with the average blockage coefficient decreasing to 0.07 and 0.04, respectively. The standard deviation of the average flow velocity at the test section is reduced by 42.78% compared to the original, and the temperature fluctuation at the workpiece surface is reduced by 53.09%. Both the flow and temperature field uniformity are significantly improved. Full article

A variable-order time-fractional Kelvin peridynamics model is proposed, where the variable order is utilized to reflect the changes of viscosity in viscoelastic materials to effectively capture the damage and deformation of rock steady creep. The corresponding constitutive model is established by coupling a spring and an Abel dashpot. Through the Caputo definition of fractional-order derivatives, finite increment formulations for the constitutive model are derived to facilitate numerical implementation by an explicit time integration scheme. We accordingly introduce a model parameter evaluation method for practical applications. To verify the validity and correctness of the model, constant-order time-fractional peridynamics is used to compare with the proposed model via a sandstone compress creep numerical test, and the results show that the latter can simulate nonlinear creep behavior more efficiently. Additionally, the numerical simulation of practical engineering is conducted. Compared with constant-order time-fractional peridynamics, the proposed model can improve the simulation accuracy by 16.7% with fewer model parameters. Full article

This paper aims to investigate the flow characteristics of the primary side fluid in a casing once-through steam generator (COTSG) under vertical conditions, providing theoretical support for its design in nuclear power plants. The study employs the three-dimensional CFD software STAR-CCM+, utilizing the Reynolds stress transport turbulent model for numerical simulations, and presents a method for determining the fully developed section of the heat transfer channel based on dimensionless velocity overlap analysis (entrance length L^∗ = 80 D_e). Through analysis, the frictional resistance characteristic curve of the spiral channel with coiled wire is divided into three regions: laminar region, transition region, and turbulent region. Over a Reynolds number range of 1000–30,000 and heat transfer powers of 1–30 kW, an expression between the frictional resistance coefficient and the Reynolds number for the spiral channel with coiled wire is established, achieving a prediction error within ±10% through a kinematic viscosity correction factor (c_t) accounting for heat transfer effects. This paper conducts a detailed study of the fully developed fluid in the spiral channel with coiled wire, revealing significant axial variations in the frictional resistance coefficient and identifying distinct velocity distribution patterns in different flow regimes (maximum velocity in central sub-channels for laminar/transition regions vs. boundary sub-channels for turbulent regions). The critical Reynolds number for laminar-to-turbulent transition increases with higher heat transfer powers, demonstrating the stabilizing effect of enhanced cooling on flow regimes. These findings provide quantitative criteria for optimizing heat exchanger design under vertical operating conditions with varying thermal loads. Full article

We describe a quantum teleportation protocol for exchanging data between a mobile robot and its control station. Because of the high cost of quantum network systems, we use MATLAB software to simulate the teleportation of data. Our simulation models the dynamic motion of a car-like mobile robot (CLMR), considering its mass and inertia and the environmental viscosity. Our remote control method accurately reproduces a mathematical model of the CLMR’s real-world motion. The CLMR’s trajectory is represented by differential equations, with the velocity calculated using the Jacobian matrix. The velocity inputs are teleported from the control station to the CLMR, enabling it to move. Nevertheless, physical constraints cause the deviation of the robot’s trajectory from the predicted trajectory. To correct this deviation, the CLMR’s current position is teleported to the control station. Before implementing this protocol, we calculate the quantum teleportation circuit, and we use quantum gates in matrix form to simulate the data teleportation process. The protocol’s accuracy is assessed by comparing the original data and teleported data, and a good match is obtained. This study demonstrates the feasibility of quantum teleportation for remotely controlling real-time robotic systems over long distances and in environments that interfere with classical wireless communication. Full article

This article presents the results of a study on the rheological and lubricating properties of selected alcohol fuels. Methanol, ethanol, and 2-propanol are investigated, for which density, kinematic, and dynamic viscosity are determined at selected temperatures in the range of 15–60 °C. In addition, the water content of the studied fuels is determined. Based on the measurements, the coefficient of temperature change for density and the relative percentage decrease in kinematic viscosity with increasing temperature are calculated. Subsequently, regression models are built to describe the value of density and viscosity of the tested liquid alcohol fuels as a function of temperature. Next, the fuels under study are subjected to the evaluation of antiwear properties using a high-frequency reciprocating rig (HFRR). For each fuel, the corrected wear scar size WS_1.4, which is a measure of lubricity, the average coefficient of friction, and the relative percentage decrease in oil FILM thickness during the conduct of the HFRR test under standardized conditions, are determined. The measurements are carried out at a standardized temperature of 25 °C in accordance with standardized methods for a time equal to 75 min. Due to the low lubricity of the tested fuels, additional tests are performed at a reduced time equal to 30 min. In this case, all fuels show a similar WS_1.4 value, which ranges from 384 μm for methanol through 422 μm for 2-propanol to 426 μm for ethanol. The wear marks on the samples after the execution of the test are used to draw additional qualitative conclusions about the lubricating properties of the tested alcohols. The results obtained are summarized, and possibilities for their use in further research are provided. Full article

The Split-Hopkinson pressure bar (SHPB) test is a commonly accepted experiment to investigate the material behavior under high strain rates. Due to the low impedance of soft materials, here, the test has to be performed with plastic bars instead of metal bars. Such plastic bars have a certain viscosity and require a correction of the measured signals to account for the attenuation and dispersion of the transmitted waves. This paper presents a signal correction method based on a spectral decomposition of the strain-wave signals using Fast Fourier Transform and additional applied strain gauges in the experimental setup. The concept can be used to adapt the pulses and to concurrently validate the measurement method, which supports the evaluation of the experiment. Our investigation is carried out with a Split-Hopkinson pressure bar setup of PMMA bars and silicon-like specimens produced by the 3D printing process of digital light processing. Full article

This review summarizes the most important measurement techniques for determination of the volumetric liquid-phase mass transfer coefficient k_La. In addition, the main empirical correlations (with their applicability ranges) for k_La estimation are presented. It is clearly underlined that in tall bubble columns, a system of two differential equations (involving the gas and liquid axial dispersion coefficients) should be solved in order to obtain the accurate k_La value. The semi-empirical correlations for k_La prediction based on the correction of the penetration theory are also summarized. The need for a correction of the penetration theory is explained. The different definitions of the gas–liquid contact time, including the one based on the local isotropic turbulence theory, are presented. Finally, the various chemical methods for the determination of the gas–liquid interfacial area are summarized. Additionally, the main correlation for the prediction of the interfacial area is reported. The effects of pressure, temperature, and viscosity on the interfacial area and k_La are discussed. Full article

Understanding flow dynamics around hydraulic structures is essential for optimizing water management systems and predicting flow behavior in real-world applications. In this study, we simulate a 3D flow control system featuring a sluice gate and a weir, commonly used in hydraulic engineering. The focus is on accurately incorporating modified dynamic boundary conditions (mDBCs) and viscosity treatment to improve the simulation of complex, turbulent flows. We assess the performance of the Smoothed Particle Hydrodynamics (SPH) method in handling these challenging conditions. Especially when the boundary conditions and applicability to industry are two of the SPH method’s grand challenges. Simulations were conducted on a Graphics Processing Unit (GPU) using the DualSPHysics code. The results were compared to theoretical predictions and experimental data found in the literature. Key hydraulic characteristics, including 3D flow effects, hydraulic jump formation, and turbulent behavior, are examined. The combination of mDBCs with the Laminar plus sub-particle scale turbulence model achieved the correct simulation results. The findings demonstrate agreement between simulations, theoretical predictions, and experimental results. This work provides a reliable framework for analyzing turbulent flows in hydraulic structures and can be used as reference data or a prototype for larger-scale simulations in both research and engineering design, particularly in contexts requiring robust and precise flow control and/or environmental management. Full article

Recently, the liquid composite molding technique (LCM) has been used for producing fiber-reinforced polymer composites, since it allows the molding of complex parts, presenting good surface finishing and control of the mechanical properties of the product at the end of the process. Studies in this area have been focused on resin transfer molding (RTM), specifically on the resin rectilinear infiltration through the porous preform inserted in the closed cavity neglecting the sorption effect of the polymeric fluid by the reinforcement. Thus, the objective of this work is to predict resin radial flow in porous media (fibrous preform), including the effect of resin sorption by fibers considering a one-dimensional approach. For correct prediction of the flow behavior inside the porous media, an advanced modeling approach composed of the mass conservation equation and Darcy’s law is used, and the solution of the coupled equation is obtained. Transient results of the flow front location, velocity and pressure within the mold during the resin infiltration are shown, the effects of different parameters for resin (viscosity), reinforcement (sorption term, permeability and porosity) and process (injection pressure and injection radius) are analyzed, and an in-depth discussion is performed. Full article

In this paper, a reliable model of the viscosity in liquids in the dual model of liquids (DML) framework is developed. The analytical expression arrived at exhibits the correct T–dependence Arrhenius-like exponential decreasing trend, which is typical of Newtonian simple fluids. The model is supported by the successful comparison with both the experimental values of the viscosity of water, and with those related to the mechano-thermal effect in liquids under low-frequency shear, discovered a few years ago, for which the first-ever theoretical interpretation is given by the DML. Moreover, the approach is even supported by the results of numerical models recently developed, that have shown that dual liquid models, such as the DML, provides very good agreement with experimental data. The expression of viscosity contains terms belonging to both the subsystems constituting the liquid, and shows an explicit dependence upon the sound velocity and the collective vibratory degrees of freedom (DoF) excited at a given temperature. At the same time, the terms involved depend upon the Boltzmann and Planck constants. Finally, the physical model is coherent with the Onsager postulate of microscopic time reversibility as well as with time’s arrow for macroscopic dissipative mechanisms. Full article