Search Results (588)

This study investigates the acoustic and aerodynamic performance of cylindrical silencers incorporating uniform and sequential mixed-perforation liners under grazing-flow conditions. Five uniform perforated panels with hole diameters ranging from 0.4 to 5 mm and four mixed configurations (0.4/1, 0.6/1, 0.8/1, and 1/5 mm) were analysed. The mixed silencers consisted of two consecutive 450 mm sections. Acoustic performance was experimentally evaluated in the 100–10,000 Hz frequency range at flow velocities of 4, 8, and 12 m/s, including insertion loss, flow-generated noise, and pressure loss. The experimental analysis was complemented by the Maa impedance model and the flow-dependent Rao–Munjal model. Impedance contrast ratios were additionally introduced to characterise differences between consecutive sections of the mixed liners. Maximum insertion-loss values of 35.5–41.0 dB were observed around 2000 Hz. Neither theoretical model exhibited a corresponding characteristic feature around 2000–2500 Hz, indicating that the attenuation maximum cannot be attributed to perforation impedance alone. The results demonstrate that perforation geometry primarily controls local resistive and reactive behaviour, whereas maximum attenuation results from the combined acoustic response of the perforated liner, porous backing, silencer geometry, and wave-propagation conditions. Sequential perforation therefore provides an additional design parameter for tailoring silencer performance without increasing its overall dimensions. Full article

The uncertain propagation direction of rotating detonation in hollow combustors limits the predictability of liquid hypergolic propulsion systems. In this study, the effect of circumferentially non-uniform injection on the propagation direction of monomethylhydrazine/nitrogen tetroxide (MMH/NTO) rotating detonation is numerically investigated. Different injection-intensity distributions are established by varying the local mass flow rate and injection velocity while maintaining the total propellant mass flow rate and overall oxidizer-to-fuel ratio. The results show that configurations with shorter injector groups exhibit inconsistent propagation directions, whereas the ${\mathrm{S}}_4$–${\mathrm{M}}_4$–${\mathrm{L}}_4$ configuration at a non-uniformity amplitude of 0.4 shows a clear directional preference consistent with the injection arrangement. At $\delta =0.6$, opposite-direction propagation was observed in limited simulations, indicating a non-monotonic directional response under the investigated conditions. Reversing the injection arrangement after stable rotating detonation is established does not reverse the propagation direction. Transient pressure fields further reveal competition between oppositely propagating circumferential pressure waves during detonation establishment. These results indicate that circumferentially non-uniform injection mainly influences propagation-direction selection during the establishment stage. Full article

To reduce the operational cost and risk of conventional downhole testing, this study presents an integrated well-test interpretation workflow that uses wellhead shut-in pressure data to characterize formation flow conditions in real time. Fluid mass- and heat-transfer equations are established for the wellbore, and a heat-conduction equation is established for the formation. Flash calculations are used to capture condensate phase changes inside the wellbore, while wave propagation and seepage mechanics are integrated into the formation flow model. This yields a coupled wellbore–formation flow system, and a corresponding numerical solution method is proposed according to the mathematical characteristics of the governing equations. Using this model, an interpretation method for wellhead-pressure testing in fracture-vuggy condensate-gas wells is established to determine critical reservoir parameters, including permeability, skin factor, cave location, and cave volume. The results show that converting measured wellhead pressure to bottomhole pressure after shut-in introduces an error during the initial shut-in period; this error gradually decreases with increasing shut-in time. Validation against a field well shows that the overall relative pressure error is less than 2%. Interpreted wellbore storage and near-wellbore cave volume exhibit errors within 5%, while formation permeability, distant cave volume, and cave location are essentially unaffected. The skin-factor difference is 0.55 (dimensionless; relative difference 20.1%), which should be interpreted with caution because skin factor is strongly controlled by early-time data. The model is adaptable to various wellbore types in fracture-vuggy condensate-gas reservoirs. Compared with traditional downhole testing, the proposed method substantially reduces operational hazards and expenses while providing accurate results, offering a low-risk, low-cost, and efficient technical solution for optimizing deep gas-field development. Full article

This paper is a fundamental study that theoretically estimates the acoustic properties of a simplified structural model of a sound-absorbing foam material, which is porous. This study adopts a simplified foam-structure model consisting of continuous spherical pores arranged as a simple cubic lattice. This model is termed a negative simple cubic lattice, and fundamental research was conducted to estimate its acoustic properties theoretically. An experiment was performed by 3D-printing samples and measuring the normal-incidence sound absorption coefficient using a two-microphone impedance measurement tube. In this theoretical analysis, the void region, which consists of the negative simple cubic lattice, was elementally divided perpendicular to the direction of sound incidence and modeled as a gap enclosed by two parallel planes. The calculated characteristic impedance and propagation constant were substituted into a transfer matrix for sound pressure and volume velocity based on the 1D wave equation, and the normal-incidence sound absorption coefficient was derived using the transfer matrix method. Furthermore, the theoretical values that consider Helmholtz resonance and tortuosity closely follow the trend of the experimental values. In addition, theoretical values were derived from mathematical models whose dimensions were approximated to those of an actual sound-absorbing foam material. Full article

Blast-induced ground vibration is traditionally predicted using empirical scaled-distance equations or numerical simulations driven by simplified analytical loading functions. Although dynamic finite element modeling has significantly advanced the understanding of stress-wave propagation, existing approaches remain unable to reproduce the complete seismic response of actual production blasting because the true blast source is generally unknown and is therefore replaced by simplified pressure–time functions. Consequently, a field-calibrated physics-informed Digital Twin framework for production blasting remains insufficiently established. This study presents a PI-DDT framework for production blasting based on field-derived seismic source reconstruction. The proposed methodology consists of two complementary innovations. First, the three-component near-field pilot-blast record was analyzed through deconvolution-based inverse wave propagation, and the transverse, longitudinal, and vertical components were independently deconvolved to reconstruct three orthogonal equivalent single-hole seismic source histories at the pilot blast hole. Second, the three reconstructed source histories were incorporated into the PLAXIS 3D dynamic finite element model through component-specific dynamic multiplier functions together with the actual production-blast geometry, blast-hole coordinates, electronic initiation sequence, site-specific rock-mass properties, and attenuation characteristics to establish a field-calibrated PI-DDT framework for a full-scale production blast. The proposed framework was applied to a full-scale production blast comprising 83 blast holes in an operating open-pit mine. Model performance was evaluated through a multi-domain performance assessment including PPV, amplitude-envelope development, frequency-spectrum agreement, and cumulative-energy evolution. The simulated responses showed practically meaningful agreement with field measurements across multiple monitoring locations, with a median component PPV error of 11.8%, a mean three-dimensional resultant PPV error of 14.2%, a mean resultant spectral similarity of 84.0%, and a mean three-dimensional cumulative-energy MAE of 4.7%. Unlike conventional blasting simulations that rely on simplified analytical loading functions, the proposed methodology reconstructs a field-derived equivalent seismic source signature and integrates it directly into a physics-based numerical model. The principal scientific contribution of the study lies in the field-calibrated integration of equivalent seismic source reconstruction, actual production-blast geometry and initiation timing, three-dimensional dynamic FEM, and multi-domain model-performance evaluation within a unified physics-informed framework. The developed framework provides a physics-based computational foundation for blast-design evaluation, vibration-control planning, digital mining applications, and future AI-assisted blast-design optimization and adaptive vibration-control workflows. Full article

To address the relatively high near-wellbore fracture-initiation resistance and the tendency of hydraulic fractures to propagate along a dominant path under conventional perforation-based hydraulic fracturing, three large-scale hydraulic-fracturing experiments were conducted using a 10,000-ton ultra-large true-triaxial hydraulic-fracturing physical simulation system to investigate the effects of different controllable shock-wave–perforation operation schemes on shale fracture initiation and propagation. Natural shale outcrop blocks from the Jimsar shale oil reservoir, each measuring 2.0 m × 2.0 m × 1.0 m, were used. Three operation schemes were investigated: conventional perforation–hydraulic fracturing, shock wave–perforation–hydraulic fracturing, and perforation–shock wave–hydraulic fracturing. Post-fracturing fracture observations, three-dimensional fracture reconstruction, and wellhead-pressure responses were jointly analyzed to characterize fracture initiation and propagation under the different operation schemes. The results showed that, under conventional perforation–hydraulic fracturing, fracture propagation was dominated by a principal fracture, with only limited secondary fractures, and the wellhead breakdown pressure reached 21.2 MPa. After breakdown, the pressure remained at a relatively high level and exhibited sustained fluctuations, indicating large and continuously varying fracture-propagation resistance. When one 100 kJ shock was applied before perforation, several large-scale dominant fracture surfaces developed, and the breakdown pressure decreased to 6.6 MPa, representing a reduction of 68.9% relative to the conventional case. The post-breakdown pressure gradually stabilized, indicating reduced variation in fracture-propagation resistance. When two successive 100 kJ shocks were applied after perforation, fractures propagated in multiple directions with more pronounced bending, deflection, and branching. The breakdown pressure further decreased to 4.6 MPa, 78.3% lower than that of the conventional case. Fractures continued to propagate under relatively low pressure, followed by a late-stage pressure increase. The dynamic disturbance induced by controllable shock waves altered the near-wellbore stress distribution and rock-failure conditions, reduced hydraulic-fracture initiation resistance, and modified subsequent fracture-propagation paths. These results reveal the coupled mechanism of near-wellbore stress redistribution and dynamic fracture propagation induced by controllable shock-wave–perforation operations, and provide experimental support for fracture-initiation control and optimization of integrated stimulation parameters in the Jimsar shale oil reservoir. Full article

Field observations indicate that gouge-filled faults can be weakened under dynamic stressing and further trigger earthquakes. Previous studies have qualitatively attributed such fault weakening to elevated pore pressure within fault gouges induced by seismic deformation, which reduces fault shear strength and frictional resistance. However, direct experimental evidence and systematic quantitative analyses clarifying the hydromechanical controls on the dynamic weakening process remain scarce. Here, artificial filled fractures were prepared by sandwiching granular infills with varied water content between two cylindrical aluminum bars to constitute an aluminum split Hopkinson pressure bar (SHPB) system. Benefiting from the rock-like wave impedance of aluminum bars, this setup can better reproduce real in situ dynamic loading conditions. Using this system, we investigated the hydromechanical response of filled fractures under dynamic stressing and clarified the underlying fault weakening mechanism. The experimental results indicate that the filled fractures undergo significant compression under dynamic loading and exhibit limited rebound deformation during unloading, presenting a distinctive trapped-unloading behavior and obvious stiffness enhancement relative to the loading stage. Variations in the water content of fracture infills substantially alter the stiffness, viscosity, and stress relaxation properties of the filled fractures, thereby regulating stress wave propagation and dynamic deformation characteristics. It is inferred that higher water content significantly hinders the dissipation of excess pore water pressure, reduces the effective confining stress, and ultimately intensifies the hydromechanical weakening of filled fractures. These quantitative findings provide novel experimental insights into the hydromechanical weakening mechanism of natural gouge-filled faults under dynamic stressing. Full article

The present study investigates the flow-acoustic interactions within the slat and flap coves of a 30P30N high-lift configuration. Velocity fluctuations in the slat cove exhibit a dominant tonal feature at a Strouhal number based on the slat chord $\left(c_s\right)$, $S{t}_s=f{c}_s/U_{\infty }=1.75$ ($f\approx$ 1500 Hz), corresponding to the second acoustic mode predicted by the feedback model. Strong coherence between wall-pressure sensors in the slat cove and shear layer velocity fluctuations confirms this coupling. The same tonal signature appears in the flap cove wall-pressure spectra, with high coherence between slat and flap surface-pressure signals, indicating propagation of acoustic waves from the slat to the flap. However, no tonal content is observed in the flap cove velocity spectra, suggesting that while acoustic waves propagate between coves, they do not excite shear-layer unsteadiness within the flap cove. Full article

This study addresses the challenges of slow attenuation and significant hazards associated with explosive shock waves confined within conventional underground tunnel walls. A novel serrated passive shock-attenuating tunnel design is proposed, grounded in the principle of viscous dissipation within the boundary layer. The investigation encompasses both experimental analyses and numerical simulations. The study found that shock waves in smooth tunnels primarily propagate as one-dimensional plane waves, resulting in concentrated energy and gradual attenuation. Conversely, the serrated tunnel geometry generated a continuous reflection, scattered and vortex formation due to abrupt geometric discontinuities, led to distortion and fragmentation of the shock front and the emergence of a three-dimensional discrete pressure field. Through turbulent dissipation mechanisms, energy is rapidly transformed into small-scale vortices, effectively reducing wave velocity and markedly diminishing the forward peak pressure. Under conditions of high-equivalent explosions, the serrated structure demonstrates enhanced efficacy in energy dissipation and peak pressure attenuation, significantly curtailed the effective propagation distance of high-pressure shock waves. Optimization of the serration spacing identified 30 cm as the optimal interval, minimizing stress peaks both centrally and at the tunnel entrance, thereby maximizing wave attenuation. Comparative analysis between simulation and experimental was resulted that corroborates the wave-attenuation performance of the serrated design, offering a critical foundation for the development of blast-resistant underground structures. Full article

Storm-surge residuals represent one of the most destructive marine-coastal hazards, and reliable short-term surge residual prediction is critical for coastal disaster preparedness. Conventional empirical forecasting approaches suffer from limited cross-regional generalization, while high-fidelity physics-based hydrodynamic models such as ADCIRC-SWAN can reproduce complete storm-surge physical processes but demand substantial computational resources. In this study, a three-layer back-propagation neural network (BPNN) for storm-surge residual forecasting is constructed, which is driven by output datasets from the validated ADCIRC-SWAN coupled hydrodynamic model. Wind speed, significant wave height, sea-surface atmospheric pressure, and the simulated current-time storm-surge residual are selected as input predictors. Simulation-derived samples are pre-processed via data cleaning and Min-Max normalization, and two different dataset partitioning strategies (random mesh-point-based partition and time-sequential partition) are implemented for comparative experiments. After hyperparameter sensitivity tests, the optimal network configuration with 30 hidden-layer neurons is determined. Model predictive performance is quantitatively evaluated via multi-station time-series comparison and universal statistical metrics including R, NSE, and RMSE. The results show that the BPNN achieves satisfactory performance under random mesh-point-oriented partitioning, yet obvious performance degradation occurs under time-sequential temporal extrapolation, with prominent underestimation of surge peaks. On the basis of BPNN-predicted spatial surge residual fields, storm-surge intensity grading is carried out following the Chinese national standard GB/T 39418-2020. Statistical comparisons between the full computational domain and the Pearl River Estuary sub-region reveal strong spatial aggregation of high-intensity storm-surge grids within the estuary driven by funnel-shaped topographic amplification. This work demonstrates the feasibility of using a BPNN as a surrogate emulator for hydrodynamic outputs under a given typhoon condition; however, limitations in temporal extrapolation performance still need to be addressed before this approach can be practically used in operational early-warning applications. Full article

Hydraulic transients induced by rapid changes in operating conditions represent a major challenge in the design and safe operation of offshore Firewater systems. During emergency events, such as fire pump start-up or rapid valve operations, pressure waves may propagate throughout the distribution network, generating water hammer effects capable of compromising the integrity and reliability of critical safety equipment. This study investigates the transient hydraulic response of an offshore Firewater ring-main system installed on a Floating Production Storage and Offloading (FPSO) unit using a detailed numerical model developed in PIPENET Transient. Three representative emergency operating scenarios were analysed, including fire pump start-up, deluge valve closure, and monitor valve closure. For each scenario, the hydraulic response of the original system configuration was compared with a modified pressure-protection arrangement involving relocation of the check valve immediately downstream of the fire-pump discharge flange and reduction of the pressure safety valve (PSV) set pressure from 17.5 barg to 16.5 barg. The simulations enabled the identification of critical pressure locations, evaluation of transient pressure propagation, and assessment of the effectiveness of the proposed mitigation strategy. The results demonstrate that the modified pressure-protection arrangement reduces the governing system-level pressure peaks and attenuates transient pressure oscillations under the investigated operating conditions. The proposed engineering methodology provides practical support for the design verification and optimization of offshore Firewater systems and contributes to improving the operational safety and reliability of safety-critical piping networks. Full article

This study examines how pipe bends affect the explosion behavior of premixed air–light hydrocarbon mixtures. We aim to provide a basis for safer pipeline design and explosion risk reduction in industrial systems that include bends. We used a combined experimental and computational approach: high-fidelity explosion experiments together with large eddy simulation (LES). First, we conducted baseline tests in a straight pipe with premixed gases at different equivalence ratios to find the ratio that gives the highest peak explosion pressure. We then systematically varied the double-elbow configuration, testing seven complementary angle pairs: 30°/150°, 45°/135°, 60°/120°, 90°/90°, 120°/60°, 135°/45°, and 150°/30°. By tracking flame morphology, maximum overpressure, overpressure rise rate, and flame speed, we identified how bend geometry couples with explosion dynamics. The results show that bend angle strongly influences wall-induced compression, but the effect on peak overpressure is non-monotonic due to competing mechanisms: pressure wave reflection reinforces the flame at symmetric angles, while flow dissipation weakens it in highly asymmetric configurations. Peak overpressure reaches its highest value at the symmetric 90–90° arrangement, exceeding the straight-pipe baseline by 66%. However, the largest flame surface area and fastest propagation occur in configurations with large angle differences. The maximum pressure rise rate, by contrast, increases steadily with bend angle. Flame speed increases substantially in elbow configurations, driven by stronger turbulent mixing from flow separation and vortex shedding. The 150–30° and 90–90° configurations produce the highest speeds (~100 m/s), whereas the 30–150° arrangement yields a smaller enhancement due to weak initial turbulence. Downstream of the bend, flame morphology distorts significantly: both wrinkling intensity and total flame surface area grow with bend angle, which increases the reaction rate and overall explosion intensity. These findings offer quantitative guidance for optimizing explosion prevention, positioning ignition sources, and assessing risk in bent industrial piping. Full article

The dipole antenna is one of the oldest and most widely used devices in electromagnetic engineering, yet the behavior of its near-field during emission remains only partially captured by classical models. In the source-free region surrounding the arms, the vacuum Maxwell–Heaviside equations provide an insufficient number of configurations to describe the transient through which a bound signal becomes a freely propagating wave. We revisit the model equations, introducing an extended formulation in which an auxiliary velocity field complements the electromagnetic fields. Similarly to plasma physics, the outgoing signal is treated as an electromagnetic fluid carrying a charge density. As the far field is concerned, the resulting system admits an exact family of spherical free-wave solutions that follow the rules of geometrical optics. The near-to-far field transition also acquires a concrete dynamical description, thanks to the introduction of the pseudocharge, which is a charge-like density identified with the divergence of the electric field. In addition, a pressure-like potential, vanishing in the far field, tracks the conversion between bound and radiating energy. The approach is illustrated on a standard dipole antenna through direct numerical simulation of the full coupled system. The results suggest a unified analytical and computational pathway for antenna modeling, with natural extensions to more complex geometries and other radiating devices. Full article

Continuous-wave mud pulse telemetry offers high spectral efficiency and transmission rates, making it an important technology for high-speed information transmission under complex well conditions. However, surface-received signals are highly susceptible to periodic pressure pulsations generated by mud pumps, which degrade phase extraction and symbol decision performance. Dual-pressure-sensor delayed differential processing can exploit the correlated propagation characteristics of pump noise between two measurement locations to suppress its correlated components; however, its performance depends on accurately matching the propagation delay and amplitude compensation coefficient. To specifically address the dynamic variation in the pump noise propagation relationship between two measurement locations under actual operating conditions, a joint delay–amplitude compensation method is developed, in which pump noise suppression is formulated as the joint estimation of the signal propagation delay and amplitude compensation coefficient. Built upon LMS-based time delay estimation, the proposed method employs an enhanced time-varying step-size LMS time delay estimation algorithm (HTVSS-LMSTDE) to improve dynamic retracking capability following changes in propagation delay. A sliding-window weighted least-squares method (SWLS) is further introduced to estimate the amplitude compensation coefficient and correct differential mismatch caused by variations in the amplitude transfer ratio. With non-pump interference modeled as additive white Gaussian noise independent of the telemetry signal and pump noise, simulation results demonstrate that, when the propagation delay and amplitude transfer ratio vary simultaneously, the proposed method yields delay estimates and amplitude compensation coefficients close to their theoretically optimal values. Field wellbore tests further verify that the proposed method effectively attenuates low-frequency pump noise interference in continuous-wave mud pulse telemetry signals while preserving the BPSK-modulated information. Full article

Efficient blasting design is increasingly regarded not only as a geomechanical problem but also as a managerial challenge related to energy use, fragmentation quality, downstream comminution costs, and environmental performance. This study develops a shock-adiabat-based analytical model for predicting the radius of the crushing zone around borehole explosive charges and demonstrates its applicability as a decision support tool for energy- and cost-oriented blasting management. The model integrates shock wave propagation parameters, particle velocity behind the shock front, and the physical and mechanical properties of limestone, sandstone, and granite. The calculated crushing zone radiation was compared with a previously developed analytical model based on borehole pressure and validated using finite element simulations in SolidWorks Simulation. The discrepancy between the proposed shock adiabat model and the reference analytical solution did not exceed 6%, while the difference between analytical estimates and numerical simulations remained below 5%. The results show that borehole diameter, compressive strength, and explosive–rock interface pressure significantly affect the crushing zone radius and, consequently, the volume of rock effectively fragmented during blasting. A scenario-based assessment further indicates that improved prediction and management of the crushing zone may reduce downstream crushing and grinding energy demand by approximately 10–20%, generating potential cost savings and indirect CO₂ emission reductions. The proposed method therefore supports the management of blasting energy efficiency, fragmentation quality, operational costs, and sustainability performance in mineral extraction systems. Full article