Search Results (25,096)

Wind has a significant effect on pool fire behavior, which is relevant to many fire conditions, such as wildfires, building fires, and oil transportation fires. Although fire behavior and morphology changes have received considerable attention and been widely researched, there are few works concerning the flow and flam dynamics of pool fire. A large eddy simulation model is adopted to investigate the flow and flame dynamics of a rectangular pool fire considering the combined effects of wind and slope. The results show that, with a wind speed of 0.5 m/s, a flame develops immediately downstream of the fire source and sustains two flanks of plume. Further downstream, the plume starts to rise due to buoyant force. Temperature, velocity, and vorticity distributions show significantly different shapes at different streamwise locations. Near the fire source, the flame is confined to a small region around the fire source. The air circulation downstream shows a cylindrical spiring pattern. When the wind speed increases, the temperature and velocity become more parallel to the surface and their maximum values increase. On the contrary, the temperature fluctuations and turbulent kinetic energy decrease with the wind speed, and they are more frequent near the flame tails. Full article

Hydrocarbon fields that contain non-associated gas, such as gas condensate, are highly valuable in terms of production. They yield significant amounts of condensate alongside the gas, but their unique behavior presents challenges. These reservoirs experience constant changes in composition and phases during production, which can lead to condensate blockage near wells. This blockage forms condensate bridges that hinder flow and potentially decrease gas production. To address these challenges, engineers rely on numerical simulation as a crucial tool to determine the most effective project management strategy for producing these reservoirs. In particular, relative permeability curves are used in these simulations to represent the physical phenomenon of interest. However, the representativeness of these curves in industry laboratory tests has limitations. To obtain more accurate inputs, simulations at the pore network level are performed. These simulations incorporate models that consider alterations in interfacial tension and flow velocity throughout the reservoir. The validation process involves reproducing a pore network flow simulation as close as possible to a commercial finite difference simulation. A scale-up methodology is then proposed, utilizing an optimization process to ensure fidelity to the original relative permeability curve at a microporous scale. This curve is obtained by simulating the condensation process in the reservoir phenomenologically, using a model that captures the dependence on velocity. To evaluate the effectiveness of the proposed methodology, three relative permeability curves are compared based on field-scale productivities and the evolution of condensate saturation near the wells. The results demonstrate that the methodology accurately captures the influence of condensation on well productivity compared to the relative permeability curve generated from laboratory tests, which assumes greater condensate mobility. This highlights the importance of incorporating more realistic inputs into numerical simulations to improve decision-making in project management strategies for reservoir development. Full article

Purpose: To assess the impact of a four-week training program combining TOGU (a functional training system and equipment) Balanza and Dynair^® Ballkissen equipment on core strength, balance ability, and golf swing performance in golf athletes. Methods: The TOGU group participated in TOGU training three times weekly and regular golf skill training over four weeks. The control group only participated in regular golf skill training. The functional movement screening (FMS) assessment system modified the Clinical Test of Sensory Interaction on Balance (mCTSIB), and Unilateral Stance Tests (USTs) were used to assess neuromuscular control. Data are expressed as mean ± standard deviation (SD) and utilized the independent samples t-test and the paired t-test for statistical analysis. Results: (1) Following the four-week training, there was significant improvement of the TOGU group in the total score of FMS, notably in squats and in-line lunges (p < 0.05). (2) Significant reductions in COG sway velocity were observed: Foam-EO (−30.9%, p < 0.01) Firm-EC (−35.18%, p < 0.05) and Foam-EC (−36.78%, p < 0.005). UST also improved: L-EO (−34.39%, p < 0.005), L-EC (−29.92%, p < 0.005), R-EO (−48.67%, p < 0.01), and R-EC (−39.38%, p = 0.0857). (3) Club head speed (CHS) tests indicated significant enhancement (p < 0.01), improved ball speed (p < 0.005), driving distance (p < 0.0553), and hitting efficiency (p < 0.01). The control group showed no significant changes in all tests after four weeks of regular golf skill training. Conclusions: A TOGU-based golf core training program can significantly improve a golfers’ neuromuscular control, core stability, and coordination, and enhance their swing performance. Full article

Monitoring the stability of tailings storage facilities (TSFs) is extremely important due to the catastrophic consequences of instability, which pose a threat to both the environment and human life. For this reason, numerous laboratory and field tests are carried out around dams. An extensive database is collected as part of monitoring and field research. The in-depth analysis of available data can help monitor stability and predict disaster hazards. One of the important factors is displacement, including surface displacements—recorded by benchmarks as well as underground displacements—recorded by inclinometers. In this work, methods were developed to help assess the stability of the TSF in terms of surface and underground displacement based on the simulated data from geodetic benchmarks. The context of spatial correlation was investigated using hot spot analysis, which shows areas of greater risk, indicating the places of correlation of large and small displacements. The analysis of displacements versus time allowed us to indicate the growing exponential trend, thanks to which it is possible to forecast the trend of future displacements, as well as their velocity and acceleration, with the coefficient of determination of the trend matching reaching even 0.97. Additionally, the use of a geographically weighted regression model was proposed to predict the risk of shear relative to surface displacements. Full article

In order to meet current and future efforts to reduce fuel consumption and gas emissions, an increasing number of ships are being retrofitted with one of the wind-assisted propulsion solutions. In this paper, the effects of retrofitted wind-assisted propulsion on the efficiency of the propeller are investigated. The installed ship propeller is usually designed to operate under specific conditions; once the thrust force from the sails is added, the operating point of the propeller changes. Taking into consideration the reduced efficiency of the propeller, which is no longer operating in its optimal regime, the actual wind-assisted propulsion contribution can be calculated. The wind-assisted contribution is calculated with a velocity prediction program as a reduction in conventional propulsion power output by maintaining the vessel’s designed speed. From the calculated variations in sail thrust force, dependent on the wind speed, the propeller efficiency is analyzed for different operating states. The propulsion efficiency of the propeller was analyzed with a performance characteristics calculation tool that has been developed and presented in this paper. From the meteorological data obtained from Copernicus Marine Services and available ship documentation, a case study was conducted for a selected route. Full article

Motion is vital for life. Currently, the clinical assessment of motion abnormalities is largely qualitative. We previously developed methods to quantitatively assess motion using visual detection systems (around-body) and stretchable electronic sensors (on-body). Here we compare the efficacy of these methods across predefined motions, hypothesizing that the around-body system detects motion with similar accuracy as on-body sensors. Six human volunteers performed six defined motions covering three excursion lengths, small, medium, and large, which were analyzed via both around-body visual marker detection (MoCa version 1.0) and on-body stretchable electronic sensors (BioStamp version 1.0). Data from each system was compared as to the extent of trackability and comparative efficacy between systems. Both systems successfully detected motions, allowing quantitative analysis. Angular displacement between systems had the highest agreement efficiency for the bicep curl and body lean motion, with 73.24% and 65.35%, respectively. The finger pinch motion had an agreement efficiency of 36.71% and chest abduction/adduction had 45.55%. Shoulder abduction/adduction and shoulder flexion/extension motions had the lowest agreement efficiencies with 24.49% and 26.28%, respectively. MoCa was comparable to BioStamp in terms of angular displacement, though velocity and linear speed output could benefit from additional processing. Our findings demonstrate comparable efficacy for non-contact motion detection to that of on-body sensor detection, and offers insight as to the best system selection for specific clinical uses based on the use-case of the desired motion being analyzed. Full article

This study was based on a target spectrum (GB183062015) and synthesized different characteristic periods, pulse ground motions, and non-pulse ground motions utilizing EQsignal v1.2.1 software. It also investigated the dynamic behaviors of bridge piers in seismic motions with varying characteristic periods, pulse and non-pulse effects, and the influence of 0 m and 10 m water depths. The findings indicated that the peak acceleration and stress behaviors vary significantly under different characteristic periods of ground motion. The maximum error in peak acceleration behavior of a bridge pier under ground motions of varying characteristic periods is 19.25%, while the maximum error in peak stress response is 11.35%. The acceleration and stress behaviors of a bridge pier under pulse ground motion action are more considerable than those under non-pulse seismic motion action. When the characteristic period is 0.40 s, the maximum error in peak acceleration of the bridge pier structure under pulse seismic motion and non-pulse seismic motion action is 86.08%, with the maximum error of the peak stress reaches 80.68%. The existence of water serves to minimize the natural frequency of the bridge pier. The pulse effects result in a maximum error of 40.49% for the peak acceleration and a maximum discrepancy of 323.08% for the peak stress of the bridge pier. The hydrodynamic effects result in a maximum error of 33.51% for the acceleration peak and 12.90% for the stress peak of the bridge pier. The effect of the pulse symptoms on the dynamic behavior of the bridge pier is considerably more pronounced than that of the hydrodynamic effects, with an intricate and complex influencing mechanism. In bridge flood protection and seismic design and optimization, it is essential to consider the impact of pulse seismic motion with varying characteristic periods. Full article

The RELAP5 code is a computational tool designed for transient simulations of light water reactor coolant systems under hypothesized accident conditions. The original wall drag partition model in the RELAP5 code has a problem in that the bubble velocity is predicted to be faster than the water velocity in the fully developed flow in a constant-area channel. The wall drag partition model, based on the wetted perimeter concept, proves insufficient for accurately modeling bubbly flows. In this study, the wall drag partition model was modified to account for the physical motion of fluid particles. After that, the modified RELAP5 code was applied to predict the SBLOCA of a full-scale nuclear power plant. Considering the SBLOCA scenario, the behavior change in the loop seal clearing phenomenon was clearly shown in the analysis by the model change. Upon the termination of natural circulation, the loop seals were cleared, allowing the steam trapped within the system to discharge through the break. The modified model was confirmed to have an impact at this time. It mainly affected the timing and shape of the loop seal clearing and delayed the overall progress of the accident. It was observed that the flow rate of the bubbly phase decreased as the modified model accounted for wall friction during dispersed flow in the horizontal section, impacting the two-phase flow behavior at the conclusion of the natural circulation phase. Full article

This article presents a vibration signal analysis method to diagnose helicopter turboshaft engine defects such as bearing imbalance and wear. The scientific novelty of the article lies in the development of a comprehensive approach to diagnosing helicopter turboshaft engine defects based on the vibration signals amplitude and frequency characteristics integral analysis combined with a neural network for probabilistic defect detection. Unlike existing methods, the proposed approach uses the energy criterion for the vibration characteristics. It averages the assessment of unique signal processing algorithms, which ensures reliable defect classification under flight vibration conditions. The method is based on representing vibration signals as a sum of harmonic oscillations supplemented by noise components, which helps to identify deviations from typical values. The developed method includes a state function in which the amplitudes and frequency characteristics from nominal parameters estimate deviations. When the critical threshold is exceeded, the function signals possible malfunctions. A multilayer neural network is used to classify defect types, providing high classification accuracy (from 0.985 to 0.994). Computer experiments on the developed seminaturalistic modeling stand confirm that the method can detect increased vibration levels, which is the potential failure indicator. Comparative analysis shows the proposed method’s accuracy and noise resistance superiority, emphasizing the importance of introducing modern technologies to improve aircraft operation reliability and safety. Full article

The impact of ore-rock blocks on the shaft wall of a vertical ore pass is a crucial cause of shaft wall damage and failure. Based on the structure and parameters of the ore pass in a case mine, the first collision’s position of the ore-rock block with respect to the ore pass wall and the angle between the impacting direction of the ore-rock block and the horizontal plane before and after the collision are investigated via a kinematic analysis. The normal and tangential analysis models of ore rock impacting the shaft wall are established and analyzed based on contact mechanics. The results show that: (1) based on the kinematic analysis of ore rock moving in the ore pass and on the colliding condition of the ore-rock block the first time that it collides with the ore pass wall, the coordinates and angles of the collision are proposed; (2) the impacting process of ore rock is categorized into elastic compression, elastic–plastic compression, and rebound of the shaft wall material. The relationship between the normal impact force and the penetrating depth is determined, and the slipping distance of the ore-rock block along the shaft wall and the lost volume of the shaft material are established. (3) The wall material’s normal, tangential, and total restitution coefficient is acquired. (4) The total lost volume during the collision is obtained through the analysis and solution of the model. (5) Based on the characteristics and parameters of the ore pass in the case mine, the influence of the impact velocity and angle of the ore-rock block on the restitution coefficient, maximum normal intrusion depth, maximum tangential displacement, and volume loss of the shaft wall are analyzed by using relevant formulas. Full article

In order to improve the accuracy and efficiency of flow pattern recognition and to solve the problem of the real-time monitoring of flow patterns, which is difficult to achieve with traditional visual recognition methods, this study introduced a flow pattern recognition method based on a convolutional neural network (CNN), which can recognize the flow pattern under different pressure and flow conditions. Firstly, the complex gas–liquid distribution and its velocity field in the annulus were investigated using a computational fluid dynamics (CFDs) simulation, and the gas–liquid distribution and velocity vectors in the annulus were obtained to clarify the complexity of the flow patterns in the annulus. Subsequently, a sequence model containing three convolutional layers and two fully connected layers was developed, which employed a CNN architecture, and the model was compiled using the Adam optimizer and the sparse classification cross entropy as a loss function. A total of 450 images of different flow patterns were utilized for training, and the trained model recognized slug and annular flows with probabilities of 0.93 and 0.99, respectively, confirming the high accuracy of the model in recognizing annulus flow patterns, and providing an effective method for flow pattern recognition. Full article

A wind erosion instrument is a core instrument for collecting sand particles in wind and sand flows and studying the laws of wind and sand movement. To study the influence of the internal structure of the wind erosion instrument on its sand collection efficiency, a built-in louver separation device was designed. Based on CFD and Fluent 2022 software, numerical analysis was conducted using an RNG k-ε model, and the discrete phase model (DPM) method was used to calculate the sand collection efficiency. The flow field analysis of the new wind–sand separator was carried out. The influence of blade inclination angle, blade thickness, and blade number on sand collection efficiency was studied using single-factor and response surface analysis methods. The optimal parameter combination was obtained as blade inclination angle of 30°, blade thickness of 1.25 mm, and blade number of 10. A simulation model was established based on the optimal combination parameters, and the performance of the wind erosion instrument before and after the addition of the louver separation device was compared. The simulation results show that adding a louver separation device can increase static pressure, alleviate short-circuit flow and back-mixing phenomena, and stabilize the flow field; increasing tangential velocity leads to an increase in particle centrifugal force; reduce axial velocity, prolong particle stagnation time, and minimize particle escape. The particle trajectory pattern is mostly a continuous spiral path, which is conducive to capturing particles and improving sand collection efficiency. Compared with the original structure, for particles with diameters ranging from 0.001–0.05 mm, 0.005–0.01 mm, 0.01–0.05 mm, 0.05–0.1 mm, and 0.1–0.5 mm, the addition of a louver separation device increased the sand collection efficiency by 32.74%, 22.55%, 33.17%, 11.45%, and 0.13%, respectively. When the wind speed is 13.8 m/s and the diameter range is 0.001–0.5 mm, the average sand collection efficiency obtained from simulation tests and wind tunnel tests is 86.18% and 84.32%, respectively, with an error of 2.2%. The simulation results are reliable. The research results show that adding a louver separation device can improve the sand collection efficiency of the wind erosion instrument, and has better overall performance compared to the original wind–sand separator. This study provides a basis for further research on the structure of wind erosion gauges and the environmental protection of farmland. Strengthening land management can effectively protect soil resources, reduce wind erosion, ensure the stability of the ecosystem, and lay the foundation for promoting the sustainable use of land. Full article

The current paper focuses on the assessment of radial mesh influence on the description of the transient event obtained by an axisymmetric model. The objective is to reduce computational effort while accurately calculating hydraulic transients in smooth–turbulent pressurized pipes. The analyzed pipe system has a reservoir–pipe–valve configuration with an inner diameter of 0.02 m and a total length of 14.96 m, with the initial discharge being equal to 120 × 10⁻³ L/s (Re = 7638). An extensive study is carried out with 80 geometric sequence meshes by varying the total number of cylinders, the geometric common ratio, and the pipe axial discretization. The benefit of increasing the geometric common ratio is highlighted. A detailed comparison between two meshes is presented, in which the best mesh (i.e., the one with the lowest computational effort) has a three-fold higher value of the geometric common ratio. The two meshes show small differences for the instantaneous valve closure, limited to a time interval immediately after the arrival of the pressure surge and only during the first pressure wave. The dynamic characterization of the transient phenomenon demonstrates the in-depth consistency between the model results and the hydraulic transients’ phenomenon in terms of the piezometric head, the wall shear stress, and the mean velocity time-history, in comparison to the results obtained with the shear stress, lateral velocity, and axial velocity profiles. Full article

The purpose of this study was to investigate the effect of instructions that prioritize either speed or accuracy in experienced senior football players when taking penalty kicks at five different targets in a goal. Sixteen male experienced senior football players performed in total 80 penalty kicks with instructions that prioritized either precision or speed at five different targets in the goal. Ball velocity and hit accuracy were evaluated between the two instructions and the five targets. The main findings showed that aiming for velocity resulted in higher ball velocity and lower kicking accuracy than aiming for accuracy. However, kicking accuracy was only lower when kicking to the bottom corner targets. Furthermore, when shooting high at the middle, the percentage of balls on target was higher when aiming for speed rather than accuracy. Based upon the findings of the study, it is suggested that a player should try to kick as fast as possible and aim for the middle of the goal, as ball velocity is faster than when aiming for accuracy and hit percentage in the goal is also at its highest, thereby increasing the chances of outdoing the goalkeeper, who most often goes for one of the sides. Full article

The introduction of connected autonomous vehicles may bring opportunities and challenges to traditional traffic control instruments, like ramp metering. This paper starts by constructing the fundamental diagram for mixed-autonomy traffic based on the car-following behaviors of both connected autonomous vehicles and human-driven vehicles. Then, analyses are performed on the main factors that influence the critical velocity, critical density, and road capacity under mixed-autonomy traffic. Two methods named COE-HERO and TRLCRM are developed to support the implementations of coordinated ramp metering for freeways with mixed-autonomy traffic. The COE-HERO method enhances the HERO method by incorporating a critical occupancy estimation module. Both COE-HERO and TRLCRM consider dynamic traffic flow parameters of mixed-autonomy traffic. The TRLCRM method is a reinforcement learning-based approach with a two-stage training framework, enabling it to adapt to varying mixed-autonomy demand scenarios. Extensive microscopic simulations show that the learning-based TRLCRM method can effectively alleviate bottleneck congestion and is robust to deal with various traffic scenarios. The COE-HERO method performs better than the HERO method, indicating the necessity of critical occupancy estimation in the implementations of coordinated ramp metering. Full article