Penetration Angle Research Articles

High-fidelity modelling of unburnt coal flow in an industry-scale blast furnace using a hybrid CFD-DEM method

Solid fuels, such as coal or biochar, can be injected into a blast furnace for low-carbon ironmaking. However, unburnt coal or biochar powders may accumulate in the coke bed, potentially reducing bed permeability and compromising furnace stability. Current CFD-DEM methods struggle to simulate systems with significant size differences between coke particles and coal or biochar powders, where the diameter ratio dck/dcl is 100–200 times. In this work, a novel multi-resolution hybrid CFD-DEM model is developed to simulate gas-unburnt powders-coke particles flow dynamics within and around the raceway with high fidelity. The model’s accuracy is validated by comparing the simulated evolution of the raceway cavity shape with experimental results. Subsequently, the hybrid model is used to simulate unburnt powder flow through the raceway and the adjacent coke bed (dck/dcl = 100), comparing its performance with conventional smoothed CFD-DEM models. The effects of gas inlet velocity and powder wettability are also analysed. Results show that the hybrid CFD-DEM model effectively simulates detailed pore fluid flow in the coke bed, which the smoothed model fails to capture, demonstrating the hybrid model’s superiority. Increasing gas inlet velocity enlarges the raceway cavity, intensifies high-speed pore flows, and accelerates powder transport into the coke bed. Additionally, higher cohesion energy density (kCED) reduces powder penetration, aligns the peak holdup position and penetration angle, and decreases permeability at key probe positions. This work provides an effective and efficient numerical tool to help understand and optimise the injection operation in blast furnaces.

A novel mechanical-laser collaborative intra-row weeding prototype: structural design and optimization, weeding knife simulation and laser weeding experiment.

The competition between intra-row weeds and cultivated vegetables for nutrients is a major contributor for crop yield reduction. Compared with manual weeding, intelligent robots can improve the efficiency of weeding operations. This study proposed a novel mechanical-laser collaborative intra-row weeding device structure. A slider-crank mechanism size optimization algorithm was proposed, and the correctness of the algorithm was verified by ADMAS software. Finally, the crank and link lengths were determined to be 87 mm and 135 mm, respectively. The resistance of triangular weeding knives with different penetration angles and edge angles in the soil was simulated and analyzed using EDEM software. The simulation results show that the triangular weeding knife with a soil penetration angle of 0 ° and an edge angle of 30 ° encountered the least resistance. In addition, weed control experiments with different powers and lasers were conducted using 200 W NIR and 200 W blue lasers. The experimental results show that the time it took for a 50 W blue laser and a 100 W NIR laser to remove small weeds was approximately between 0.3 and 0.4 s, and the time it took for a 50 W blue laser to remove larger weeds was approximately between 0.5 and 0.6 s. The time it took for 75 W and 50 W NIR lasers to remove weeds was more than 1 s. Based on the above research results, a prototype of a mechanical-laser collaborative intra-row weeding device was successfully built. This study provides a new idea for the field of intelligent weeding. The simulation and experimental results can provide a reference for the research and development of mechanical weeding and laser weeding equipment.

DEM simulation of subsoiling in tropical sugarcane fields: Effects of opposing subsoiler design and model parameters

During the subsoiling operation of clayey soil in sugarcane fields in tropical areas, there are key limitations such as high resistance caused by high adhesion and unsatisfactory subsoiling effects of machines and tools. To address these issues, this study first explored the machine's structural characteristics using a mechanism analysis method to identify key optimization parameters. Then, simulation tests were conducted based on the root-soil complex model. Single factor analysis was conducted to evaluate the effects of backsweep angle, plow spacing, and penetration angle on tillage resistance and soil disturbance, determining their optimal ranges. Finally, a multi-factor orthogonal rotation combination experiment was designed using Box-Behnken theory to optimize the subsoiler's structural parameters. The regression analysis results show that the optimized model significantly improves the reliability of simulation results. Field verification test results show that under the conditions of a sweep angle of 50°, a plow spacing of 60 cm, and a soil penetration angle of 45°, the average tillage resistance of subsoiling operations is significantly reduced to 76.2 kN, and the amount of soil disturbance is reduced to 1780cm². The optimization reduced tillage resistance and soil disturbance by 34.42% and 30.50% respectively, significantly improving the subsoiling performance. To our knowledge, this is the first work applying discrete element methods to subsoiling operations in red clay soils in sugarcane growing areas. The proposed machine structure has higher efficiency and better performance, providing an effective reference for the design and application of sugarcane field subsoiling machinery.

Accuracy of Boltless Frame-Based Stereo-Electroencephalography Electrode Implantation.

Boltless implantation of stereo-electroencephalography electrode is a useful alternative especially when anchor bolt is not available such as in country with limited resources or is less appropriate such as placement in patients with thin skull or at the occiput area, despite some drawbacks including potential dislodgement. While the accuracy of implantation using anchor bolt is well-studied, data on boltless implantation remain scarce. This study aimed to reveal the accuracy, permissible error for actual placement of electrodes within the grey matter, and delayed electrode dislodgement in boltless implantation. A total of 120 electrodes were implanted in 15 patients using a Leksell Stereotactic G Frame with each electrode fixed on the scalp using sutures. Target point error was defined as the Euclidean distance between the planned target and the electrode tip on immediate postimplantation computed tomography. Similarly, delayed dislodgement was defined as the Euclidean distance between the electrode tips on immediate postimplantation computed tomography and delayed MRI. The factors affecting accuracy were evaluated using multiple linear regression. The permissible error was defined as the largest target point error that allows the maximum number of planned gray matter electrode contacts to be actually placed within the gray matter as intended. The median (IQR) target point error was 2.6 (1.7-3.5) mm, and the permissible error was 3.2 mm. The delayed dislodgement, with a median (IQR) of 2.2 (1.4-3.3) mm, was dependent on temporal muscle penetration (P = 5.0 × 10-4), scalp thickness (P < 5.1 × 10-3), and insertion angle (P = 3.4 × 10-3). Boltless implantation of stereo-electroencephalography electrode offers an accuracy comparable to those using anchor bolt. During the planning of boltless implantation, target points should be placed within 3.2 mm from the gray-white matter junction and a possible delayed dislodgement of 2.2 mm should be considered.

Fracture characteristics and energy dissipation law of shale under water-based impact loads

Shale fracture and energy dissipation are the basis of reservoir fracturing effect evaluation. The damage and fracture mechanism of shale under dynamic impact load is the key scientific concern of reservoir fracturing. To study the law of fracture, fracture propagation and energy dissipation of shale under dynamic impact, dynamic tests of water-based impact load under different impact velocities were carried out using impact rock breaking test platform based on air cannon. Topological and fractal theory, Weibull distribution model, space vector geometry method and Griffith fracture mechanics theory were used to systematically study the effects of impact velocity on fracture development and expansion, fragment mass and size distribution, damage degree of abutment residual and energy dissipation transformation. Scanning electron microscopy (SEM) was used to observe the micromorphology of the impact fracture surface. The results demonstrated that an increase in impact velocity led to the formation of a network fracture featuring main fractures, cavity fissure, bedding fractures, and crushing zones, thereby enhancing the fracture’s capability to penetrate bedding. The apparent fracture network connectivity, topology structure and fractal dimension were positively correlated with impact velocity. The residual height of the shale decreased, resulting in an escalation of the damage degree from mild (0.43) to severe (0.75), while the average penetration angle decreases from 81.00° to 63.52°. The area of new surface experiences rapid initial growth followed by a more gradual increase, with dissipative energy showing a more pronounced increase compared to crushing energy. The micro-fracture mode underwent an evolution from brittleness to toughness and a transition from low energy consumption to high energy consumption. The propagation, reflection, and superposition of stress waves within the rock mass gave rise to a complex stress zone, ultimately causing the rock mass to break. These findings lay the groundwork for developing a stress-damage-energy-failure combined model for shale subjected to dynamic impact loads, thereby enhancing the development of intricate networks in shale reservoir and improving the effective extraction of shale gas.

Advancing Fuel Spray Characterization: A Machine Learning Approach for Directly Injected Gasoline Fuel Sprays

Compression ignition engines when operated on gasoline fuels cause significant reduction in NOx and particulate emissions. In such advanced combustion strategy, the fuel-oxidiser mixing process, intensified by the prolonged ignition delays of gasoline fuels, directly affects the stability and efficiency of combustion. Thus, optimising fuel spray characteristics leads to optimisation of injector design, engine performance and subsequent decrease in emissions. Since spray development is a complex process that involves wide range of length and time scales, computationally expensive modelling techniques can be replaced with machine learning (ML) models. These ML models are employed to predict spray characteristics utilizing datasets generated from comprehensive spray studies. In this work, a dataset of about 5400 instances taken from non-evaporating gasoline fuel spray imaging experiments under Gasoline Compression Injection (GCI) engine conditions is used to train various ML models with data split of 70 % and 30 % for training and testing, respectively, with five-folds cross-validation performed within the training. The fuel injection pressure (60 – 150 MPa), chamber pressure (0.1 – 2 MPa), nozzle diameter, nozzle hole conicity and injection duration are used as input features to the models for predicting the spray tip penetration and spray angle. The performance of four ML models was evaluated and compared under default and tuned hyperparameters against experimental data and available physics-based correlations in the literature. The models include random forest, extreme gradient boosting, multilayer perceptron, and elastic-net. The results show that the hyperparameter-tuned extreme gradient boosting model performs best in predicting the spray parameters. The overall model performance was evaluated using the coefficient of determination (R2), mean absolute error (MAE), and root mean squared error (RMSE), resulting in values of 0.884, 0.651, and 1.571, respectively. This study presents compelling evidence demonstrating the effectiveness of ML as a powerful tool for isolating non-linear behaviors from physical processes. By effectively decoupling these behaviors, ML enhances the accuracy of predicting spray characteristics while significantly reducing computational costs. The application of ML in fuel injector design has the potential to revolutionize engine performance and contribute to substantial reductions in emissions.

Characterizing and visualizing the direct injection of hydrogen into high-pressure argon and nitrogen environments

Using argon as the working fluid in an internal combustion engine holds the potential of substantially enhancing thermal efficiency because of its high specific heat ratio. Burning hydrogen, not with air but with pure oxygen, in a closed-loop argon power cycle would lead to an emission-free exhaust composition, effectively containing only water and argon, which can be separated by condensation. One of the current challenges is the high-pressure direct injection of both fuel and oxidizer, which directly controls the combustion process. To support the development of such an injection strategy, high-pressure injections of hydrogen into pressurized argon and nitrogen are investigated using high-speed Schlieren and pressure transducers in a non-heated constant-volume chamber at varying conditions. In this work it is shown that hydrogen mass flow increases linearly with injection pressure and that it is unaffected by chamber pressure as expected based on choked flow theory, while jet penetration and cone angle are determined by the pressure ratio between the fuel line and the ambient. A correlation is presented between jet penetration and pressure ratio for argon or nitrogen environments at room temperature.

Experimental study of the noise suppression of supersonic impinging jets with chevrons

Supersonic impinging jets may cause many adverse ground effects, including surface erosion, nonuniform surface heat transfer, lift loss, and acoustic loading. In this study, chevron nozzles are used to suppress the noise generation of supersonic impinging jets originated from a circular convergent nozzle with the jet Mach number of 1.2. An array of microphones is used to measure the far-field acoustic fields, and a schlieren system is employed to measure the near-field flow structures. Three impinging distances are considered to examine the differences between the impinging jets and the free jet, and to assess the effect of impinging distance on the noise characteristics. Two chevron nozzles with different penetration angles are designed to investigate the potentials of chevron nozzles in controlling the supersonic-impinging-jet noise. Results show that the chevron nozzles do not alter the directivity of overall sound pressure levels, but significantly reduce the amplitude at all emission angles. The discrete tones in the impinging jets are dramatically mitigated or eliminated, and the levels of broadband noise are also significantly reduced over a wide range of frequency band, regardless of the impingement distance. The influences of chevrons on the near-field flow structures are checked with the root-mean-square values and proper orthogonal decomposition of schlieren images, which provide more evidence on the noise suppression mechanism with chevrons.

On the impact of using nanoparticles type additives on the altering of diesel fuel jet characteristics

Even though diesel-powered passenger cars and light-duty vehicles may not be sold in the European Union by 2035, possibly in most other countries will be. Truck diesel engines will remain in use after 2035 because electric trucks are not a viable alternative for goods transportation. This involves continuing research and development on diesel engines to reduce their pollutant emissions. Alternative (renewable) fuels with combustion improvers can diminish emissions at the source. Nanoparticle-based additives can enhance the efficiency and emissions of diesel engines through their intense catalytic activity and by improving the fuel injection process. However, their effect on the injection process has not been well tested and published in the dedicated literature. The use of nanoparticles mixed in small fractions with original diesel fuel influences the physicochemical properties of the fuel as well as the formation of fuel jets inside the combustion chamber. This research focuses on the opportunity of using different diesel fuel blends mixed with combustion improver additives such as MWCNT and CeO2 nanoparticles. In this sense, a simulation investigation was conducted using the AVL BOOST Hydsim software. The physicochemical properties of fuels were used to assess the macroscopic characteristics of the fuel spray, such as penetration, spray cone angle, and Sauter mean diameter. When increasing the nanoparticle dosage, the penetration and spray cone angle values are decreasing, while the Sauter mean diameter values are increasing. This tendency is present for both nanoparticle types considered.

The Impact of Heli-FX EndoAnchor Application on Endograft Material: An Experimental Study

The Impact of Heli-FX EndoAnchor Application on Endograft Material: An Experimental Study

Optimization Design and Experiment of High-Speed Drag-Reducing Trencher Based on Conservation Tillage

In the realm of high-speed precision broadcasting, the existing seeder opener proves inadequate for the speed of the seeding operation. We focus on the duckbill opener and employ the quadratic regression orthogonal rotation combination test design method to optimize the structural parameters of the opener. Throughout the experiment, the primary performance metrics encompassed the opener’s working resistance and the side dumping distance. The selected experimental factors comprised the penetration angle, the angle of soil entry gap, the shovel body width, and the shovel length. The optimal arrangement of structural parameters has been determined: a penetration angle, a soil entry gap angle, a shovel body width of 21 mm, and a shovel length of 142 mm. These parameters contribute to increased velocity, reduced operational resistance, and minimal soil disturbance. Under this combination, the relative deviations between the recorded measurements and the theoretical outcomes for working resistance and the side dumping distance stand at 4.24% and 1.06%, respectively; these confirm the credibility of the optimization results. We performed adaptability testing and conducted a comparative analysis under various operational conditions to assess the innovative opener’s ability to reduce force, minimize soil disruption, and maintain depth stability. The findings are as follows: At a depth of 5 cm and velocities ranging from 6 km/h to 8 km/h, an average working resistance reduction of 19.73%, a 5.64% decrease in the side dumping distance, and an average depth stability of 89.5% were observed. When operated at a speed of 7 km/h with a depth ranging from 3 cm to 5 cm, an average reduction of 19.66% in operational resistance, a 2.59% decrease in the side dumping distance, and an average depth stability of 91.1% were recorded. These results illustrate the innovative opener’s capacity to significantly reduce working resistance and side dumping distance while satisfying the depth stability requisites.

Free fall penetration test the undrained shear strength of submarine sediments

To perform in-situ testing of deep-sea sediment undrained shear strength, a novel free-fall penetrometer has been developed. This penetrometer is released from above the seabed and penetrates the sediments under gravity, resulting in intense interaction with the sediment. The study conducted free fall penetration tests in the Xisha area of the South China Sea, yielding the following achievements: (I) the establishment of a free-fall penetration governing equation, influenced by penetration attitude, along with the development of a model for undrained shear strength, revealed that at a 5° penetration angle, the sediment support force exceeded 100 N, and the undrained shear strength is approximately 40 kPa. (II) the relationship between dynamic penetration resistance coefficient and penetration velocity was inverted by the data from in situ test and laboratory. An error analysis revealed that inclined penetration and unreasonable penetration resistance coefficient can lead to errors exceeding 40 % in the test results.

Pressure-based large-eddy simulation of under-expanded hydrogen jets for engine applications

An assessment of Large-Eddy Simulations (LES) of non-reactive under-expanded hydrogen jets by using a pressure-based algorithm is presented. Such jets feature strong compressible discontinuities often considered to be best dealt with by a density-based solver. The crucial contribution of this work is to evaluate the suitability of the pressure-based solver to correctly describe the flow field of gaseous hydrogen jets for engine applications, despite the presence of shock waves in the under-expanded near-orifice region. Inherently, the paper aims at providing guidance on the corresponding numerical aspects to simulate these flows. Hydrogen jets in an argon atmosphere at three different injection pressures are simulated and the results are compared to experiments in literature. Jet tip penetration and cone angle are the main investigated parameters. A good match is found, confirming the solidity of the proposed model. Different LES sub-grid scale models and discretisation schemes are then investigated in order to find the best approach in terms of accuracy and required computational cost. In particular, it is found that the WALE model coupled with a 4th-order cubic scheme for the convective terms yields the most suitable configuration.

Breaking behavior and stress distribution of T12A hard steel core penetrating ceramic/aluminum alloy lightweight composite armor

The armor-piercing incendiary (API) round inflicts significant damage to light armor. This article conducts penetration experiments on lightweight ceramic composite armor using 12.7 mm API rounds. The Rosin-Rammer distribution model is used to analyze the macroscopic fragmentation characteristics of the core, and the SEM is used to analyze the fracture surface of the bullet core after fragmentation at the microscopic level. Numerical simulations are also used to verify and expand the material parameters. The experimental results show that as the penetration velocity increases, the average feature size of the core decreases, indicating an increase in the degree of fragmentation of the core. The fragments generated by the fragmentation can be almost completely restored. The main fracture form is the brittle crushing fracture of the head of the projectile, while the tail and body of the projectile are basically intact, and the fracture surface is mainly a 45° shear fracture and radial platform-like tensile fracture.At the microscopic level, SEM images show that the material fracture mainly occurs in the form of radial cleavage shear fracture and river patterned tensile-shear fracture. The numerical simulation results show that as the penetration velocity increases, the energy dissipation of the core continuously increases. The main energy dissipation process of the core during penetration occurs during the contact with the ceramic cone, accounting for 66.48 % of the total energy loss, while the mass of the core remains almost unchanged during the interaction with the aluminum alloy.In addition, the experiment is verifiedusing different working conditions at different angles, confirming that the "unequal tearing" of the aluminum alloy backing plate is caused by the inclination of the penetration angle. It was also found that the penetration efficiency and destructive capability of the API round are significantly reduced when there is an angled penetration.

The influence of penetration angle on anti-penetration performance and reverse penetration ricochet phenomenon of UHMWPE laminates

Penetration angle refers to the angle between the normal of laminates and the projectile trajectory. In actual battlefield conditions, projectiles may hit Ultra-High Molecular Weight Polyethylene fiber (referred to as UHMWPE) laminates from various angles, resulting in ricochet phenomena and secondary injuries. Currently, research on bullets hitting penetrating laminates at a perpendicular angle is relatively well-developed, while research on the penetration of laminates by bullets at other angles is limited. Therefore, this study combined experiments and numerical calculations to investigate the penetration of 7.62 mm steel core projectiles at different angles on UHMWPE laminates. The study found that UHMWPE laminates enhanced bullet resistance through yawing and bending the penetrating projectiles at different angles. The influence of penetration angle on the impact area of the projectile-facing surface, the height of the bulge on the backside, and the penetration depth, as well as the trajectory and morphology of the projectile, were mastered in this study. Notably, a penetration angle of 50° was the limit condition for projectile to produce reverse penetration ricochet phenomenon of projectiles in UHMWPE laminates with a thickness of 30 mm. These research findings provide a theoretical basis and technical support for the bulletproof design of UHMWPE laminates.

单沟双行播种开沟器设计与试验分析

In order to improve the opener of the seeder and its lightweight structure, a new type of opener is designed. The overall structure and working principle of a single-ditch double-row opener are analyzed, and the structural parameters of machete cutting soil and the soil guide board are designed and optimized. Using the penetration angle of machete cutting soil and the included angle of the soil guide board as test factors, field experiments were conducted. As the test indexes, the working resistance, the sowing coefficient of variation, and the depth coefficient of variation were used to analyze the effect of the opener. The results showed that in terms of working resistance, the penetration angle of the machete cutting edge and the included angle of the soil guide board were extremely significant, and the included angle was greater than the penetration angle regarding the influence degree. In terms of the sowing coefficient of variation, the penetration angle was significant, and the included angle was extremely significant. Regarding the depth coefficient of variation, the penetration angle was extremely significant, and the included angle of the guide soil board was significant. Based on the optimization analysis by using the Design Expert 8.0.6, it is found that the performance of the opener is optimal when the penetration angle and the included angle are 50.03° and 42.36°, respectively. The working resistance, the sowing coefficient of variation, and the depth coefficient of variation are 61.47N, 6.49% and 4.22%, respectively. After verification, the results are basically consistent, and the seeding and trenching performance meets the agronomic requirements. This study can provide a basis and technical reference for the design and development of the ditching technology and opener.

Theoretical analysis of the spray characteristics of ternary blends of diesel, biodiesel, and long-chain alcohols inside a combustion chamber

The diesel and alcohol blends are potential alternatives to biogenic fuels to reduce biodiesel consumption, which might help reduce toxic emissions. Due to the high-quality requirements for engines, the fuel fundaments in the fluid properties and its impact on the macroscopic spray characteristics. Herein, a study proposed the experimental determination of density, viscosity, and surface tension for ternary mixtures of diesel (D) + biodiesel (B) + 1-hexanol (H) and + 1-octanol (O) at 298.15 K. These properties comply with the limits established by the EN 14214 and ASTM D975 standards. Thus, to extend the impact of these results, a theoretical analysis via CFD is carried out in ANSYS FLUENT ® by considering a macroscopic and isothermal system, which involved the independence tests of meshing and turbulence modeling. The numerical results evaluated the spray tip penetration, spray angle, spray morphology, eddy turbulence, and relation of spray volume and surface spray area at the injection pressure of 90 MPa using the Large Eddy Simulation (LES) model. The behavior of the spray tip penetration and spray angle agree with experimental values reported in the literature for diesel fuel. This condition validates our simulations for biodiesel and ternary blends. Therefore, the use of alcohols and biodiesel as new additives to diesel improves the macroscopic spray characteristics, and some ternary mixtures showed similar behavior to conventional diesel: spray tip penetration (70D5B25O, 70D25B5H, and 70D25B5O) and spray angle (70D25B5H, 70D15B15H, 80D5B15O, and 80D15B5). The mixture of 70D25B5H agrees with both spray characteristics; therefore, this mixture could be considered an alternative fuel to conventional diesel. Hence, this analysis presents the essential elements to visualize the macroscopic spray characteristics and the fluid properties. This knowledge serves as a foundation for elucidating the intricate dynamics of spray during combustion processes and the development of complementary studies aimed at optimizing engine performance.

Design and Evaluation of a Puncture Control Method for the Deflection of Ultrafine Needles due to Interfacial Passage-Proposal of Puncture Control Strategy for Increasing.

With the demand for sophisticated techniques to easily prevent the deflection of needles, robotic CT (computed tomography)-guided puncture with an ultrafine needle is being investigated. Quantification of deflection is essential for accurate puncture with ultrafine needles. Research on the quantification of deflection caused by tissue reaction forces to which the beveled surface of the needle tip is in progress, and this method has been applied for deflection reduction and needle steering within the tissue. However, when the needle tip passes through a tissue boundary, the needle deflects regardless of the direction of the beveled surface. Although several methods have been proposed to reduce the deflection caused by the boundary surface, no curve puncture method has been constructed using the deflection. This work aimed to construct a refraction model that can back-calculate the curved path from the body surface to the target. Assumptions of the refraction model were made based on the results of ex vivo examination, and the model was validated through in vivo examination. A refraction model in which the refraction angle is linearly proportional to the needle penetration angle relative to the boundary was hypothesized. Validation test revealed that the correlation coefficient exceeded 0.9, which was similar to that of the model and suggested the biological adaptability of the proposed model. A curve puncture method using this refraction model will be developed in the future.

Experimental study of underwater plasma arc penetration parameters for oil wellheads

Dismantling abandoned oil wellheads is a central aspect of the decommissioning of production facilities. A wellhead consists of multiple layers of conductive oil casing nested with nonconductive cement rings. Plasma-arc cutting is expected to be used in abandoned wellhead demolition owing to its high processing efficiency for conductive materials. Currently, no reports are available on the operating parameters of plasma-arc cutting in oil wellhead dismantling. This study experimentally investigated the penetration parameters of an underwater plasma arc in abandoned wellheads. The stand-off distance, penetration angle, nozzle diameter, plasma arc current, and gas flow rate were considered as the main factors affecting the penetration effect. A composite workpiece consisting of 10 mm thick mild steel and 30 mm thick cement blocks was used to simulate a small segment of an oil wellhead. The penetration depth, removal volume, penetration specific energy, and nozzle loss were used as comprehensive evaluation indicators for optimizing the penetration parameters. Based on the results, the experimental phenomena during penetration were explained and recommended values of the underwater plasma arc processing parameters were provided. This study may advance the development of plasma arc cutting for the demolition of abandoned wellheads.

Transformation of the Spatial Spectrum of Scattered Radio Waves in the Conductive Equatorial Ionosphere

The oblique radio wave incidence on a turbulent equatorial conductive collision plasma layer is considered. The “Compensation Effect” has been discovered by us. A complex refractive index of the equatorial terrestrial ionosphere has been derived for the first time. Second-order statistical moments of the spatial power spectrum (SPS) of scattered radio waves are obtained for the first time using the WKB method, taking into account the asymmetry of the problem: the inclined incidence of the wave on a plasma boundary and the asymmetry of the magneto-ionic parameters. It was established for the first time that a certain direction exists along which the inclined incidence radio wave on a plasma layer and the anisotropy parameters of a magnetoplasma compensate each other. This result will have great practical application in communication. In this case, the SPS of scattered radio waves neither widens nor is its maximum displaced. The behavior of this spectrum versus distance propagated by radio waves in the conductive equatorial ionosphere is analyzed numerically for different penetration angles and anisotropy factors of asymmetric anisotropy electron density irregularities. It was shown that the anisotropy factor of elongated plasmonic structures has a substantial influence on the “Compensation Effect” of scattered ordinary and extraordinary waves penetrating in the conductive collision ionospheric plasma the slab. Numerical calculations are carried out for the anisotropic Gaussian correlation function applying IRI experimental data.