Search Results (31)

Top Submerged Lance (TSL) technology is widely used in non-ferrous smelting, yet in-situ bath dynamics remain challenging to quantify because the process operates in a closed, high-temperature, highly turbulent and optically inaccessible environment. The absence of direct diagnostics limits the ability to relate operating conditions to bubble dynamics, gas penetration and bath agitation and constrains validation of multiphase CFD models under realistic conditions. This study introduces a multimodal sensing framework that combines spectral acoustic analysis with lance-mounted inertial motion sensing to characterize dynamic bath behavior across cold-model, laboratory-scale and pilot-scale systems. Water-glycerin experiments establish repeatable acoustic signatures of individual bubble-collapse events, with dominant emission bands in the 300–900 Hz range and higher-frequency components extending into the kilohertz domain. High-temperature laboratory trials using fayalitic slag reproduce these frequency regions while exhibiting depth-dependent attenuation and clear spectral separation between submerged and non-submerged lance operation. Power Spectral Density (PSD) and cumulative spectral power analyses resolve the influence of gas flow rate and lance submersion depth on acoustic spectral power distribution, while inertial measurements capture corresponding increases in vertical lance acceleration associated with back-pressure fluctuations. Pilot-scale trials at 120 Nm³/h air and 13 L/h diesel confirm that shallow lance submersion substantially increases measured acoustic spectral power below 3 kHz, whereas deeper penetration enhances periodic vertical acceleration response measured by the inertial sensor. The combined acoustic-inertial methodology provides a physically interpretable and cross-scale framework for assessing bubble collapse activity, plume interaction and bath agitation under high-temperature TSL conditions. The approach enables frequency-based diagnostics that can be systematically compared with CFD predictions of plume oscillation and collapse-related dynamics. Once baseline frequency ranges are established for a given slag system, the method can support process monitoring and may provide indirect indicators related to changes in surface agitation or foaming tendency, enabling structured data-driven analysis. The framework thus provides a practical bridge between cold-model experiments, high-temperature measurements, multiphase modeling and industrial TSL operation. Full article

As an efficient solid–liquid separation device, the hydrocyclone is widely applied in various industrial fields such as coal preparation and oil impurity removal, and its classification performance directly determines the efficiency of industrial separation operations., As the core separation zone of the hydrocyclone, the cone segment, its structure and the number of cone angles directly affect the flow field distribution characteristics and particle classification performance of the hydrocyclone. To reveal the regulation mechanism of the combined cone angles on the classification performance of hydrocyclones, numerical analysis and experimental verification methods were adopted to investigate the internal flow field and classification performance of hydrocyclones under different cone angle combinations. The evolution laws of velocity field, pressure field, turbulence characteristics, and particle classification effect under different configurations were systematically explored. The results show that the basic characteristics of the core flow field of the hydrocyclone do not change essentially with the increase in the number of cone segments, but the amplitude, distribution, and stability of flow field parameters are significantly regulated. The three-cone configuration achieves the optimal flow field synergy effect: the amplitude of the high turbulence intensity zone is lower and concentrated near the central axis; the zero-velocity envelope surface is stably maintained at approximately 8 mm in the core separation zone; and the full axial fluctuation of the air core is gentle, which effectively inhibits random particle diffusion and flow pattern mixing. In terms of separation performance, the three-cone configuration exhibits the highest classification efficiency in the core range of sub-coarse particles (10~30 μm), with the cut size (approximately 17.5 μm) in a reasonable range, the steepness index reaching a peak value (approximately 0.55), and the pressure drop (approximately 1.8 × 10⁵ Pa) and split ratio (2.8%) achieving synergistic optimization, balancing separation accuracy and energy consumption control. The single-cone configuration causes flow field disturbance due to the one-time contraction of the flow channel, while the four-cone configuration falls into the dilemma of “high pressure drop–marginal performance gain”, and neither achieves optimal performance. The regulation law of the number of cone segments revealed in this study provides a scientific basis for the structural optimization and engineering application of multi-cone hydrocyclones, and is of great significance for improving the particle classification efficiency in fields such as wastewater treatment and mineral processing. Full article

The growing demand for renewable energy in space-constrained environments highlights the need for compact, high-efficiency wind energy systems. Conventional bare wind turbine (BWT) arrays suffer from severe wake interactions and performance degradation when operated in tandem or closely spaced configurations. To address these limitations, this study investigates the aerodynamic performance and near-wake dynamics of a novel multi-ducted wind turbine (MDWT) system that integrates passive flow-control technique (PFCT) into an innovative fixed-duct design. The objective is to evaluate how tandem ducted arrangements with this integrated mechanism influence wake recovery, vortex dynamics, and power generation compared with multi-bare wind turbine (MBWT) system. A numerical approach is employed using the Unsteady Reynolds-Averaged Navier–Stokes (URANS) formulation with the k–ω SST turbulence model, validated against experimental data. The analysis focuses on two identical, fixed-orientation ducts arranged in tandem without lateral offset, tested under three spacing configurations. The results reveal that the ducted system accelerates the near-wake flow and displaces velocity-deficit regions downward due to the passive flow-control sheets, producing stronger inflow fluctuations and enhanced turbulence mixing. These effects improve wake recovery and mitigate energy losses behind the first turbine. Quantitatively, the MDWT array achieves total power outputs 1.99, 1.90, and 1.81 times greater than those of the MBWT array for Configurations No. 1, No. 2, and No. 3, respectively. In particular, the second duct in Configuration No. 1 demonstrates a 3.46-fold increase in power coefficient compared with its bare counterpart. These substantial gains arise because the upstream duct–PFCT assembly generates a favorable pressure gradient that entrains ambient air into the wake, while coherent tip vortices and redirected shear flows enhance mixing and channel high-momentum fluid toward the downstream rotor plane. The consistent performance across spacings further confirms that duct-induced flow acceleration and organized vortex structures dominate over natural wake recovery effects, maintaining efficient energy transfer between turbines. The study concludes that closely spaced MDWT systems provide a compact and modular solution for maximizing energy extraction in constrained environments. Full article

Although accurate quantification of forest soil CO₂ emissions is critical for improving global carbon cycle models, traditional chamber and gradient methods often underestimate fluxes under windy conditions. Based on long-term field observations in a subtropical maple forest, we quantified the interaction between canopy-level winds and soil pore air pressure fluctuations in regulating vertical CO₂ profiles. The results demonstrate that canopy winds, rather than subcanopy airflow, dominate deep soil CO₂ dynamics, with stronger explanatory power for concentration variability. The observed “wind-pumping effect” operates through soil pressure fluctuations rather than direct wind speed, thereby enhancing advective CO₂ transport. Soil pore air pressure accounted for 33%–48% of CO₂ variation, far exceeding the influence of near-surface winds. These findings highlight that, even in dense forests with negligible understory airflow, canopy turbulence significantly alters soil–atmosphere carbon exchange. We conclude that integrating soil pore air pressure into flux calculation models is essential for reducing underestimation bias and improving the accuracy of forest carbon cycle assessments. Full article

This paper studies the exact and approximate relations between fluctuations in thermodynamic variables (pressure, density and temperature) that are imposed by the dilute-gas ($\mathcal{Z}=1$) equation-of-state ($\mathrm{EoS}$), which is a satisfactory approximation of air thermodynamics for a wide range of pressures and temperatures. It focuses on triple- and higher-order correlations, extending previous studies that concentrated on second-order moments, with emphasis on the mathematical relations, which are generally valid independently of the particular flow configuration. Exact equations are developed both involving only single-variable moments and relating the correlations between variables. These contain nonlinear terms generated by the density-temperature fluctuation product in the fluctuating $\mathrm{EoS}$. The importance of the nonlinear terms in the 6 exact equations between the 10 third-order moments is assessed using $\mathrm{DNS}$ (direct numerical simulation) data for compressible turbulent plane channel ($\mathrm{TPC}$) flows and analyzed using general statistical inequalities involving third-order and fourth-order moments. The corresponding linearized system between third-order moments is studied to determine approximate relations and 4-tuples of linearly independent moments. These mathematical tools are then used to analyze $\mathrm{TPC}$ flow $\mathrm{DNS}$ data on the triple correlations between the thermodynamic variables. Full article

Mean flow velocities and the corresponding turbulence fluctuation velocities were measured within the suction port of a standard twin-screw compressor using LDV and PIV optical techniques. Time-resolved velocity measurements were carried out over a time window of 1° at a rotor speed of 1000 rpm, a pressure ratio of 1, and an air temperature of 55 °C. Detailed LDV measurements revealed a very stable and slow inflow, with almost no influence from rotor movements except near the rotors, where a more complex flow formed in the suction port. The axial velocity near the rotors exhibited wavy profiles, while the horizontal velocity showed a rotational flow motion around the centre of the port. The turbulence results showed uniform distributions and were independent of the rotors’ motion, even near the rotors. PIV measurements confirmed that there is no rotor movement influence on the inflow structure and revealed complex flow structures, with a crossflow dominated by a main flow stream and two counter-rotating vortices in the X-Y plane; in the Y-Z plane, the presence of a strong horizonal stream was observed away from the suction port, which turned downward vertically near the entrance of the port. The corresponding turbulence results in both planes showed uniform distributions independent of rotor motions that were similar in all directions. Full article

Aiming at the nonlinear, nonstationary, and multiscale fluctuation characteristics of wind speed series, this study proposes a wind speed-forecasting framework that integrates multi-resolution turbulence intensity features and a Transformer-based hybrid neural network. Firstly, based on multi-resolution turbulence intensity and stationary wavelet transform (SWT), the original wind speed series is decomposed into eight pairs of mean wind speeds and turbulence intensities at different time scales, which are then modeled and predicted in parallel using eight independent LSTM sub-models. Unlike traditional methods treating meteorological variables such as air pressure, temperature, and wind direction as static input features, WaveNet, LSTM, and TCN neural networks are innovatively adopted here to independently model and forecast these meteorological series, thoroughly capturing their dynamic influences on wind speed. Finally, a Transformer-based self-attention mechanism dynamically integrates multiple outputs from the four sub-models to generate final wind speed predictions. Experimental results averaged over three datasets demonstrate superior accuracy and robustness, with MAE, RMSE, MAPE, and $R^2$ values around 0.65, 0.87, 23.24%, and 0.92, respectively, for a 6 h forecast horizon. Moreover, the proposed framework consistently outperforms all baselines across four categories of comparative experiments, showing strong potential for practical applications in wind power dispatching. Full article

A methane-air premixed gas explosion is one of the most destructive disasters in the process of coal mining, and the dynamic coupling between the shock wave triggered by the explosion and the surrounding rock of the roadway can lead to the destabilization of the surrounding rock structure, the destruction of equipment, and casualties. The aim of this study is to systematically reveal the propagation characteristics of the blast wave, the spatial and temporal evolution of the wall load, and the damage mechanism of the surrounding rock by establishing a two-way fluid-solid coupling numerical model. Based on the Ansys Fluent fluid solver and Transient Structure module, a framework for the co-simulation of the fluid and solid domains has been constructed by adopting the standard $k-\epsilon$ turbulence model, finite-rate/eddy-dissipation (FR/ED) reaction model, and nonlinear finite-element theory, and by introducing a dynamic damage threshold criterion based on the Drucker–Prager and Mohr–Coulomb criteria. It is shown that methane concentration significantly affects the kinetic behavior of explosive shock wave propagation. Under chemical equivalence ratio conditions (9.5% methane), an ideal Chapman–Jouguet blast wave structure was formed, exhibiting the highest energy release efficiency. In contrast, lean ignition (7%) and rich ignition (12%) conditions resulted in lower efficiencies due to incomplete combustion or complex combustion patterns. In addition, the pressure time-history evolution of the tunnel enclosure wall after ignition triggering exhibits significant nonlinear dynamics, which can be divided into three phases: the initiation and turbulence development phase, the quasi-steady propagation phase, and the expansion and dissipation phase. Further analysis reveals that the closed end produces significant stress aggregation due to the interference of multiple reflected waves, while the open end increases the stress fluctuation due to turbulence effects. The spatial and temporal evolution of the strain field also follows a three-stage dynamic pattern: an initial strain-induced stage, a strain accumulation propagation stage, and a residual strain stabilization stage and the displacement is characterized by an initial phase of concentration followed by gradual expansion. This study not only deepens the understanding of methane-air premixed gas explosion and its interaction with the roadway’s surrounding rock, but also provides an important scientific basis and technical support for coal mine safety production. Full article

This study investigates the numerical modeling of a high-velocity circular free-water jet impinging into a plunge pool, focusing on the simulation and validation of mean and fluctuating dynamic pressures on the pool floor. Numerical simulations were performed using two different computation methods, two-phase volume-of-fluid and Euler–Euler, under conditions replicating experimental data obtained at a jet velocity of 7.4 m/s and plunge pool depth of 0.8 m. The models, based respectively on the Volume of Fluid (VoF) and Euler–Euler methods, were evaluated for accuracy in replicating experimentally measured pressures and air concentration values. The Euler–Euler solver, coupled with the k-Omega SST turbulence model, demonstrated mesh independence for mean dynamic pressures with a mesh resolution of 24 cells across the jet diameter. In contrast, two-phase volume-of-fluid exhibited mesh dependency, particularly near the jet stagnation point and pressure values higher than the experimental ones. While the Euler–Euler accurately captured mean pressures and air concentration in close agreement with experimental data, its Reynolds-Averaged Navier–Stokes (RANS) formulation limited its ability to simulate pressure fluctuations directly. To approximate these fluctuations, turbulent kinetic energy values were used to derive empirical estimates, yielding results consistent with experimental measurements. This study demonstrates the efficacy of the Euler–Euler method with the k-Omega SST model in accurately capturing key dynamic pressures and air entrainment in plunge pools while highlighting opportunities for future work on pressure fluctuation modeling across a broader range of jet conditions. Full article

This study investigated the effects of downstream channel obstacles and the lateral transition distance to the dam on dam-break wave evolution as a wave–structure interaction problem. Numerical simulations were conducted using three-dimensional Navier–Stokes equations and solved using the finite volume method. The model accurately predicted interactions between dam-break waves and downstream structures. The numerical results showed that turbulence intensity increased where the cross-section significantly changed in the downstream channel. Accordingly, transcritical flow and lateral transitions were developed around the dam site. Additionally, reducing the distance of the obstacle to the dam resulted in a significant decrease in wave height and kinetic energy. The transient flow velocity direction changed around the structures, and pressure fluctuations were pronounced. Moreover, the entrainment of air bubbles and the vortex shedding were observed due to the interaction of the wave and downstream structures. The peak discharge in the downstream channel was reduced by increasing the distance of obstacles to the dam. The model successfully captured the flow disturbance, wave reflectance from the sidewalls, and formation of hydraulic jumps. The validation of the model with experimental data in the literature showed that the model performed well in predicting the wave dynamic characteristics around the downstream structures. Full article

High gravity (high-g) combustion can significantly increase flame propagation speed, thereby potentially shortening the axial length of aero-engines and increasing their thrust-to-weight ratio. In this study, we utilized the large eddy simulation model to investigate the combustion characteristics and flame morphology evolution of premixed propane–air flames in a channel with a backward-facing step. The study reveals that both the increase in centrifugal force and flow velocity can enhance pressure fluctuations during combustion and increase the turbulence intensity. The presence of centrifugal force promotes the occurrence of Rayleigh–Taylor instability (RTI) between hot and cold fluids. The combined effects of RTI and Kelvin–Helmholtz instability (KHI) enhance the disturbance between hot and cold fluids, shorten the fuel combustion time, and intensify the dissipation of large-scale vortices. The increase in fluid flow velocity can raise the flame front’s hydrodynamic stretch rate, thereby enhancing the turbulence level during combustion to a certain extent and increasing the fuel consumption rate. When a strong centrifugal force is applied, the global flame propagation speed can be more than doubled. Within a certain range, the increase in high-g field strength can enhance the intensity of RTI and accelerate the transition of RTI to the nonlinear stage. Full article

Aiming at establishing the transient flow characteristics of gas–liquid two-phase flow in high-undulation water pipelines, based on the bubble distribution law measured using physical tests, the bubble distribution law function was input into the hump-pipe fluid domain model, and CFD numerical simulation was carried out for different flow rates and different air contents. The CLSVOF two-phase flow model and the RNG k-ε turbulence model were used to analyze the flow pattern evolution and pressure pulsation propagation in the process of gas–liquid two-phase flow through a hump pipe. The results show that the bubble size has a lognormal distribution, the equivalent diameter is between 3 mm and 10 mm, and the evolution of the flow pattern in the hump pipe is complex and violent. In the horizontal pipe section, there are three main flow patterns: bubble flow, wavy flow and segment plug flow. In the vertical pipe, there are two main flow patterns, slug flow and churning flow, and the flow pattern is affected by the flow rate and the air content rate. When air bubbles or air pockets in the pipeline flow through a certain area, this leads to a steep increase and decrease in the pressure pulsation amplitude in the region, and the pressure fluctuation is extremely frequent. Compared with the water flow rate, the air content is the main factor affecting the relative pressure pulsation amplitude under the condition of a 0.15-air content operating mode, which is generally approximately two to six times that of the 0-air content operating mode. The results of the research should facilitate the prediction of stagnant gas pipeline system bursts and water hammer protection, providing a theoretical basis and calculation parameters. Full article

Hydropower plant vibrations due to pressure fluctuations and their troubleshooting methods are some of the most challenging issues in power plant operation and maintenance. This paper targets these fluctuations in a prototype turbine in two geometries: the initially approved design and the as-built design. Due to topographic conditions downstream, these geometries slightly differ in the draft tube height; the potential effect of such a slight geometrical change on the applicability of troubleshooting techniques is investigated. Therefore, the water flow was simulated using the CFD scheme at three operating points based on the SST k–ω turbulence model, while the injection of water/air was examined to decrease the pressure fluctuations in the draft tube, and the outputs were compared with no-injection simulations. The results show that a slight change in draft tube geometry causes the pressure fluctuations to increase 1.2 to 2.8 times after 4 s injecting at different operating points. The modification in the location of the air injection also could not reduce the increase in pressure fluctuations and caused a 3.6-fold increase in pressure fluctuations. Therefore, the results show that despite water/air injection being a common technique in the hydropower industry to reduce pressure fluctuations, it is effective only in the initially approved design geometry. At the same time, it has a reverse effect on the as-built geometry and increases the pressure fluctuations. This research highlights the importance of binding the construction phase with the design and troubleshooting stages and how slight changes in construction can affect operational issues. Full article

The results of in-flight experiments to determine the structure of the sound field in the cabin and pressure fluctuation fields on the surface of the fuselage of the RRJ-95NEW-100 prototype aircraft are presented here. Wall pressure fluctuation spectrums are obtained for three zones of measuring windows (forward, center, and rear fuselage) in cruising flight mode. The effect of the jet on the pressure fluctuation levels in the tail fuselage is considered. For an aircraft without an interior, the contribution of the main sources to the total intensity calculated through A-weighted overall sound pressure levels is determined. It has been determined that the main noise sources in the cabin of the RRJ-95NEW-100 prototype aircraft in cruising flight mode are pressure fluctuation fields on the fuselage surface (turbulent boundary layer noise) and the air conditioning system. The ratio between the sources varies along the length of the cabin. Full article

In experiments, flame surface density (FSD), defined as flame area per volume, is usually approximated by its two-dimensional (2D) value, as flame length per area. However, this approximation may underestimate the flame wrinkle due to the presence of a fluctuating component outside the measurement plane. Obtaining a three-dimensional (3D) flame surface density (FSD) from experiments is challenging, but it can be estimated from low-dimensional measurements under certain assumptions. Models used to estimate 3D FSD can be significantly affected by ambient pressure, as high pressure can cause a substantial decrease in small flame front scales. In this study, a ${\mathrm{CH}}_4$/air premixed turbulent flame is stabilized on a Bunsen burner and measured using the OH-PLIF technique at pressures up to 1.0 MPa. The flame front is extracted with an in-house auto adaptive threshold binarization code. Different models estimating 3D FSD with the corresponding assumptions are summarized from the definition of FSD. The reliability of the assumptions under different pressures is investigated and analyzed. The models are compared through analyzing the assumptions, and are tested in terms of global fuel consumption. The pressure’s effect on the reliability of the models could provide an essential improvement in the context of modeling turbulent combustion. Full article