Numerical Investigation Research Articles

Theoretical and numerical investigations of the floor failure characteristics affected by coal mining near complex fault structures

Water inrush from underlying aquifers under the synergistic action of complex faults and mining activities seriously threatens the mining of coal seams in North China. The failure characteristics of the coal seam floor under complex fault conditions are the keys to understanding the water inrush mechanism during mining. To investigate floor failure characteristics and water inrush mechanisms influenced by complex fault structures, theoretical analysis and numerical simulation were carried out. An improved theoretical model is first proposed, including complex fault structures such as horst, graben, and step fault structures. The calculation formula for waterproof coal pillars under complex fault conditions is established based on the improved theoretical model. The failure and displacement characteristics of the coal floor under complex faults are analyzed via numerical simulation. Compared with those under normal mining conditions, the theoretical and numerical simulation results reveal the following: (1) Under the horst structure, the floor failure characteristics show an increase in the compression failure area on both sides, and shear failure occurs on the large-dip fault side. The simulation results reveal that the failure width on the large-dip fault side increases by 25%, indicating a failure trend toward the large-dip fault side. The width of waterproof coal pillars needs to be increased by 20% to ensure mining safety. (2) Under the graben structure, the floor failure characteristics show an increase in the compression failure area on both sides, and shear failure occurs on the small-dip fault side. The simulation results reveal that the failure width on the small-dip fault side increases by 25%, indicating a failure trend toward the small-dip fault side. The width of waterproof coal pillars needs to be increased by 40% to ensure mining safety. (3) Under the step fault structure, the floor failure characteristics show compression failure on both sides, increasing the floor compression failure area on the large-dip fault side. The simulation results show that the failure width on the small-dip fault side increases by 15%, the large-dip fault side increases by 50%, and the floor failure depth increases by 20%. The width of waterproof coal pillars needs to be increased by 50% to ensure mining safety.

Experimental and numerical investigation of H-beam to recycled aggregate concrete column edge connections under cyclic loading

Experimental and numerical investigation of H-beam to recycled aggregate concrete column edge connections under cyclic loading

Numerical Study on the Retrofitting of Exterior RC Beam-column Joints with CFRP Composites Using the Grooving Method

Retrofitting seismically deficient beam-column joints (BCJs) in reinforced concrete (RC) structures is crucial to preventing collapse during high-intensity earthquakes. Fiber reinforced polymer (FRP) composites have proven effective for retrofitting these components, but debonding of the FRP from concrete surfaces remains a challenge. Recently, the grooving method (GM) has emerged as a promising solution to mitigate this issue, enhancing the bond between FRP and concrete. This paper presents a numerical investigation of BCJs retrofitted with FRP composites using the GM, focusing on various design parameters. The study utilized finite element models developed in ABAQUS, incorporating the concrete damage plasticity (CDP) model to simulate the nonlinear behavior of concrete. The interface between the concrete and FRP was modeled as a perfect bond, simulating the strong adhesion provided by the GM. The numerical results were validated against experimental data from two BCJ specimens, showing good agreement in terms of load-displacement behavior, peak loads, and failure modes. Key parameters studied include the beam longitudinal reinforcement ratio, column axial load ratio, and joint aspect ratio. The findings reveal that these parameters significantly affect the shear capacity of retrofitted joints, impacting the efficiency of the retrofitting.

Numerical Investigation of an NACA 13112 Morphing Airfoil.

This article presents a numerical study on the 2D aerodynamic characteristics of an airfoil with a morphed camber. The operational regime of the main rotor blade of the IAR 330 PUMA helicopter was encompassed in CFD simulations, performed over an angle of attack range of α=[-3°; 18°], and a Mach number of M=0.38. Various degrees of camber adjustment were smoothly implemented to the trailing-edge section of the NACA13112 airfoil, with a corresponding chord length of c=600 mm at the Reynolds number, Re=5.138×106, and the resulting changes in static lift and drag were calculated. The study examines the critical parameters that affect the configuration of the morphing airfoil, particularly the length of the trailing edge morphing. This analysis demonstrates that increasing the morphed camber near the trailing edge enhances lift capability and indicates that the maximum lift of the airfoil depends on the morphed chord length. The suggested approach demonstrates potential and can be implemented across various categories of aerodynamic structures, such as propeller blade sections, tails, or wings.

Impact of random geometric errors in an elliptical superconducting magnet with application to a compact heavy-ion synchrotron

A compact heavy-ion synchrotron is under development for next-generation cancer therapy. A superconducting magnet is designed with a main dipole field of 3.5 T and a field error less than 5 × 10−4 to maintain compactness. The coil is wound directly with monolithic Nb-Ti wire on a curved elliptical mandrel, comprising 22 laminated layers to achieve the desired magnetic field. Given the critical need for field quality, it is imperative to determine the tolerance of coil fabrication and to devise a method to eliminate field error during the design stage. This paper presents a numerical investigation of possible random geometric errors stemming from fabrication and assembly tolerances in a curved elliptical superconducting magnet. We first provide an analytical formulation derived in a complex plane to estimate the field error of a straight elliptical coil. We then conduct a Monte Carlo simulation to assess cases involving misalignment of individual wires and coil block sectors. Additionally, we compare simulation results with field measurements obtained from a short model magnet tested previously to predict potential random errors in manufacturing. Finally, we calculate the beam dynamic aperture to assess the effects of random geometric errors on beam loss using Monte Carlo simulation results. This method enables the prediction of tolerances for fabricating high-quality high-field magnets and aids in making design decisions concerning the utilization of active shim coils.

On bifurcation analysis and numerical investigation of alcohol consumption dynamics

On bifurcation analysis and numerical investigation of alcohol consumption dynamics

Steady and unsteady numerical investigation of mixed convective heat transfer enhancement in a channel with baffles attached to the heated wall

Steady and unsteady numerical investigation of mixed convective heat transfer enhancement in a channel with baffles attached to the heated wall

High-Precision Numerical Investigation of a VAWT Starting Process

For both conventional and renewable energy conversion processes, computational fluid dynamics (CFD) has been used to address more energy-related challenges in recent decades. Using CFD to investigate vertical-axis wind turbines has become more common in recent years. The main goals of this application have been to more accurately predict the turbine’s performance and to comprehend the complicated nature of the complex turbulent flow. The vertical-axis wind turbine (VAWT) simulation for energy-generating applications has several intricate components. One of them is the study of the chaotic flow that occurs during the first stages of the starting process, and which greatly influences overall effectiveness. In this article, the performance of the wind turbine was increased using a passive flow control approach. The numerical research was carried out using Large Eddy Simulation for four alternative tip speed ratios in both cases, the classic and the optimized case, equipped with a vortex trap on the extrados of the blades. The power and torque coefficient variations, as well as the velocity magnitude contours, show that the starting process may begin with a significant improvement in efficiency when flow control is used.

Numerical and experimental investigation of heat transfer of longitudinal fin with varying pitch length in flat plate solar air heater

Solar energy is a promising clean energy alternative, and consequently, the novel and innovative applications of solar energy in day-to-day life are expected to rise in the near future. The reason for limited applications of solar air heaters is their low thermal efficiency. This is due to inadequate heat transfer from the absorber plate to the air (working fluid). It has done various experiments with different pitch lengths and recorded the efficiencies corresponding to various pitch lengths. Numerical and Experimental Investigation of heat transfer of longitudinal fin with varying number of pitch length (1–5) in a flat plate solar air heater to improve the rate of heat transmission, thin and lengthy fins have been put underneath the absorber plate. The fin was intended to be square. The investigation included two different fluid masses at rates of 0.0252 and 0.10 kg/s with two distinct Reynolds numbers, 627.46 and 26585.55. The goal of the present study is to get an understanding of the effects of variations in air flow rate on the outlet temperature, heat transfer through the solar collector's thickness, and overall thermal efficiency. It has done a CFD simulation on Ansys to verify the experimental results with the simulation results.

Bouncing behaviour of a particle settling through a density transition layer

The present work focuses on a specific bouncing behaviour as a spherical particle settles through a density interface in the absence of a neutral buoyant position. This behaviour was initially discovered by Abaid et al. (Phys. Fluids, vol. 16, issue 5, 2004, pp. 1567–1580) in salinity-induced stratification. Both experimental and numerical investigations are conducted to understand this phenomenon. In our experiments, we employ particle image velocimetry (PIV) to measure the velocity distribution around the particle and to capture the transient wake structure. Our findings reveal that the bouncing process begins after the wake detaches from the particle. The PIV results indicate that an upward jet forms at the central axis behind the particle following wake detachment. By performing a force decomposition procedure, we quantify the contributions from the buoyancy of the wake ( $F_{sb}$ ) and the flow structure ( $F_{sj}$ ) to the enhanced drag. It is observed that $F_{sb}$ contributes primarily to the enhanced drag at the early stage, whereas $F_{sj}$ plays a critical role in reversing the particle's motion. Furthermore, our results indicate that the jet is a necessary condition for the occurrence of the bouncing motion. We also explore the minimum velocities (where negative values denote the occurrence of bouncing) of the particle, while varying the lower Reynolds number $Re_l$ , the Froude number $Fr$ , and the upper Reynolds number $Re_u$ , within the ranges $1 \leqslant Re_l\leqslant 125$ , $115 \leqslant Re_u\leqslant 356$ and $2 \leqslant Fr\leqslant 7$ . Our findings suggest that the bouncing behaviour is influenced primarily by $Re_l$ . Specifically, we observe that the bouncing motion occurs below a critical lower Reynolds number $Re^\ast _{l}=30$ in our experiments. In the numerical simulations, the highest value for this critical number is $Re^\ast _{l}=46.2$ , which is limited to the parametric ranges studied in this work.

Numerical investigation on the combustion characteristics and NOx emission of non-premixed H2/NH3/air in vase-shaped micro combustor

Hydrogen and ammonia, as currently popular zero carbon fuels, have received widespread attention. These two fuels have complementary advantages in combustion characteristics, cost, safety, etc. Based on the vase shaped micro combustor, a new structure proposed for application in micro thermophotovoltaic systems in our previous work. This article numerically investigated the combustion characteristics and NOx emission of non-premixed H2/NH3/Air in vase shaped micro combustor which proposed in our previous work. The variation patterns of flame temperature, wall temperature, flammability limit, and NOx emission with the blended ratio of NH3 and equivalence ratio were obtained. It was found that the flame cannot move and stabilize when the mixing ratio is 0.6. The rate of production (ROP) and sensitivity of NO and N2O were analyzed. Four precursors of NO, HNO, NH, N, N2 have been discovered. Under the conditions of this article, HNO is the key component affecting NO emissions. When the blending ratio is greater than 0.3, the lower reaction rate of HNO leaded to a decrease in NO. The elementary reaction R63: NH + NON2O + H is the key elementary reaction that affects NO consumption and N2O generation. The blending ratio of 0.4 and the equivalence ratio of 1.2 are the optimized operating conditions with the highest comprehensive performance.

Experimental and numerical investigations on the tensile response of pin-loaded carbon fibre reinforced polymer straps

Carbon fibre reinforced polymer (CFRP) pin-loaded looped straps are increasingly being used in a range of structural load-bearing applications, notably for bridge hanger cables in network arch rail and highway bridges. The static performance of such CFRP straps is investigated through experimental and numerical analyses. Finite element (FE) models based on both one-eighth and half pin-strap assembly geometries were modelled. The resulting strains, stresses, and applied loads were compared against experimental data obtained using Digital Image Correlation, Distributed Fibre Optic Sensing (DFOS), and Fibre Bragg Grating (FBG) Sensing. The FE models effectively captured local strain distributions around the vertex area, close to the pin ends of the straps, as well as in the mid-shaft region, and aligned reasonably with experimental observations. The half FE model accurately predicted the overall strain distribution when compared to DFOS data; however, higher strain magnitudes (by 0.45–10.2 %) and larger strain reductions were observed in some locations. Regarding failure loads, the FE models agreed well with Schürmann's analytical solution and the maximum stress criterion, exhibiting less than 2.5 % deviations from the experimental data. Furthermore, the predicted onset of strap failure (by delamination) in the half model agreed with experimental values, with a maximum variance of 9.2 %.

Comprehensive Assessment of the Impact of Green Roofs and Walls on Building Energy Performance: A Scientific Review

Sustainability and energy efficiency are now two pivotal goals that society aims towards. Green roofs and facades have gained significant attention in this direction for innovative, sustainable solutions for enhancing building energy performance. With a focus on sustainable urban development and energy-efficient building practices, this study delves into the intricate relationship between these green infrastructure elements and the overall energy dynamics of constructed environments. Furthermore, a range of case studies from diverse geographical locations are presented to provide valuable insights into their practical implications as emerging technologies that contribute to improved insulation, reduced heat transfer, regulating indoor temperatures, and mitigation of urban heat island effects, thus reducing the need for artificial heating and cooling and optimizing overall energy consumption. This comprehensive review serves as a dataset for understanding and highlighting all the research findings of the numerical and experimental investigations invested in the field of greenery systems to encourage their integration, which is crucial for combating climate change and pollution. Previous research is often focused on isolated, short-term, or single-climate analyses of consumption; therefore, by providing an inclusive description of their practical benefits in both temperate and extreme climates, the gap in previous articles is tackled.

Numerical and experimental investigation of the steam penetration in narrow channels during a dynamic steam sterilization cycle

The most challenging aspect of steam sterilization is the removal of all non-condensable gases (NCGs) from the autoclave. These gases prevent the effective killing of microorganisms, impairing the sterility of medical devices. Special cycles are performed to ensure the penetration of steam, even into the deepest passages. To better understand this process, numerical models were developed to determine the spatial distribution of steam within the chamber, including its penetration into narrow channels. These are the first models that can be used to accurately determine the flow within three-dimensional cavities during a dynamic sterilization cycle. To validate the model, an experiment was designed using direct tunable diode laser absorption spectroscopy at a wavelength of 1364 nm to measure the mole fraction of steam present at the end of an aluminum pipe at a temporal resolution of 1 s. This represents a pioneering application of this technique in the field of steam sterilization. This setup was designed for installation on any autoclave. Both simulation and experimental data exhibit good agreement over the entire pressure range (0.18–3.15 bar). The most interesting observation made during the study was the increase in the steam content at the end of the tube while a vacuum was generated. The numerical results show that the mole fraction of H2O increased from 0.53 to 0.63 over the course of a single vacuum phase. This phenomenon was attributed to a stronger diffusion effect combined with small pressure gradients during low pressures. This finding inspired the idea of taking the diffusion effect more into account when designing sterilization cycles in the future to make them more sustainable and effective. The presented methodologies and models represent an excellent basis for conducting more complex investigations in the future, such as those investigating the influence of condensation effects on steam penetration in cavities.

Flow state transition induced by emergence of orbiting satellite eddies in two-dimensional turbulent Rayleigh–Bénard convection

We report a numerical investigation of a previously noticed but less explored flow state transition in two-dimensional turbulent Rayleigh–Bénard convection. The simulations are performed in a square domain over a Rayleigh number range of $10^7 \leq Ra \leq 2 \times 10^{11}$ and a Prandtl number range of $0.25 \leq Pr \leq 20$ . The transition is characterized by the emergence of multiple satellite eddies with increasing $Ra$ , which orbit around and interact with the main vortex roll in the system. Consequently, the main roll is squeezed to a smaller size compared with the domain and wanders around in the bulk region irregularly and extensively. This is in sharp contrast to the flow state before the transition, which is featured by a domain-sized circulatory roll with its vortex centre ‘condensed’ near the domain's centre. Detailed velocity field analysis reveals that there exists an abrupt increase in the energy fluctuations of the Fourier modes during the transition. Based on this phase-transition-like signal, the critical condition for the transition is found to follow a scaling relation as $Ra_t \sim Pr^{1.41}$ where $Ra_t$ is the critical Rayleigh number for the transition. This scaling relation is quantitatively explained by a phenomenological model grounded on the bistability behaviour (i.e. spontaneous and stochastic switching between the two flow states) observed at the edge of the transition. The model can also account for the effects of aspect ratio on the transition reported in the literature (van der Poel et al., Phys. Fluids, vol. 24, 2012).

Effect of crossflow orientations in the impinging jet flow channel on flow and heat transfer enhancement under rotations

An experimental and numerical investigation was conducted to elucidate the flow and heat transfer characteristics of a row of impinging jets within a confined, rotating channel. The study focused on a jet Reynolds number (Rej) of 9,000, examining three distinct crossflow orientations: radially outward (ROCF), radially inward (RICF), and a combined radially outward and inward (ROICF) scheme. Jet-to-impingement surface distances (h/dj) of 2, 4, and 6 (where dj represents the jet orifice diameter) were considered, along with channel rotation speeds corresponding to Rotation numbers (Ro) from 0 to 0.0046. Heat transfer on the leading and trailing sides of the impinging jets was measured using a steady thermochromic liquid crystal (TLC) technique under constant heat flux conditions. Additionally, RANS simulations were employed to investigate the flow fields associated with the impinging jets. The results reveal that in both the ROCF and RICF schemes, heat transfer, characterized by the Nusselt number, decreases from upstream to downstream for each impinging jet. Increasing the rotation number (Ro) leads to enhanced heat transfer, with the trailing side exhibiting marginally higher values than the leading side. In the ROICF scheme, at h/dj = 2, a more uniform Nusselt number distribution is observed across all jet holes compared to the ROCF and RICF schemes, and this uniformity increases with higher Ro. However, for h/dj = 4 or 6, the heat transfer becomes non-uniform and can even deteriorate below the stationary case at high Ro numbers, attributed to the combined effects of Coriolis and centrifugal forces.

Kepler’s problem of a two-body system perturbed by a third body

One of the most important problems in basic physics and astronomy is studying the motion of planets, satellites, and other celestial bodies. The solution to the two-body problem enables astronomers to predict the orbits of the Moon, satellites, and spaceships around the Earth. The general analytic solution for the three-body problem stands unsolved except in some special cases. This reduces the problem to a two-body problem. In this work, the authors present a closed-form approach to the three-body problem theoretically and numerically based on particle–particle vector analysis. The theoretical approach, which is based on the real Moon–Sun–Earth problem information, illustrates the perturbation of the Moon in the Sun–Earth problem and shows an expected orbital motion with a perturbation in the Sun–Earth orbit due to the revolution of the Moon. The numerical investigation uses the same information to study the same problem and calculate the angular momentums of each pair of objects. The two solutions show good agreement with the well-known Earth-Moon and Sun–Earth momentums. The Moon–Sun orbit is close to an elliptic shape with angular momentum of about 3.27 × 1038 J.s. This approach is the key to future studies for n-body problem solutions.

Experimental and numerical investigations into torsional-flexural behaviours of railway composite sleepers and bearers

Abstract Fibre-reinforced foamed urethane (FFU) composite sleepers and bearers are safety-critical components installed in complex railway switches and crossings. Not only does they need to provide vertical track support, the composite sleepers and bearers must also endure longitudinal and lateral actions stemming from complex wheel and rail interactions. In reality, the railway bearers at crossing noses are susceptible to coupling torsional-flexural loading. The complex non-linear behaviours have never been investigated numerically nor experimentally. It is thus necessary to comprehend torsional-flexural behaviours of FFU composite sleepers and bearers through finite element and experimental approaches. 3D finite element modelling of FFU composite beams have been established to predict the non-linear coupling behaviours. Three specimens of FFU beams have been prepared for robust experiments under each load case. Our studies exhibit excellent agreement between numerical and experimental results. The ductile failure behaviours (post yield point) have been observed from the experiments. Considerable effects of load eccentricity on the flexure–torsion behaviours of the composite members can also be noted. In addition, the load-eccentricity curves have been identified to portray the non-linear behaviour of the railway components under coupling flexural and torsional loadings. The new insights considering their load–displacement relationships, modes of failure and damage, flexural and torsional interactions are the precursors for railway engineers to design and adopt FFU composite sleepers and bearers in practice where complex wheel/rail interface generally causes coupling torsional and vertical loading conditions.

Numerical investigation on the impact of aerodynamic braking plates positioned at streamlined sections on the slipstream and wake flow of the high-speed train based on train-fixed reference frame

This paper studies the aerodynamic characteristics of high-speed trains (HSTs) featuring aerodynamic braking plates installed on the streamlined sections, employing the improved delayed detached eddy simulation (IDDES) method at Re = 5.0 × 105. The precision of the numerical simulation methodology has been validated through reduced-scale wind tunnel experiments. A comparative analysis has been conducted on the characteristics of slipstream, wake flow, and upper flow between the original configuration (OC) and the braking configuration (BC) of the HSTs. The findings reveal that the application of braking plates promotes significant separation phenomena around the HSTs, enhancing the slipstream velocity distribution. In the BC, compared to the OC, the maximum value of the time-averaged slipstream velocity has increased by approximately 134.9% and 76.8% at the trackside and platform positions, respectively. Additionally, the TSI value of the slipstream velocity shows increases of around 100.4% and 210.4% at the trackside and platform positions, respectively. Meanwhile, the turbulence fluctuations within the wake region have been enhanced, with the formation of a longitudinal vortex alongside the railway subgrade, whose core nearly covers the TSI positions. Notably, obvious shifts occur within the upper flow field, which significantly strengthens both flow turbulence and slipstream velocity, potentially influencing components on the upper surface of HSTs, such as the pantograph. The deployment of braking plates contributes to a significant increase in overall vehicle pressure drag, thereby enhancing the train's aerodynamic drag. Relative to the OC, the aerodynamic drag of the HST has increased by approximately 235.4% in the BC.

Electrical performance of radial turbine driven by low temperature heat source: numerical investigation

High-performance Organic Rankine Cycle (ORC) systems are extensively utilized across various industrial sectors. In some applications, radial flow turbines are crucial for low-temperature heat sources. This study aims to enhance the energy and electrical efficiency of small radial turbines in Organic Rankine Cycle (ORC) ORC systems using n-pentane as the working fluid through numerical analysis. Micro-turbines are proposed to maximize performance for ORC applications. To assess the electrical, hydrodynamic and thermodynamic performance, 3D RANS simulations are conducted for five different mass flow rates with an inlet temperature of 450 K. The findings underscore the potential of radial turbines in ORC systems for utilizing low-temperature heat sources effectively. The results conducted on the entropy resulting from the irreversibility of heat transport and the irreversibility of friction. The following ranges contain the significant parameters for which this work has been completed: mass flow rates (0.1–0.5 kg.s-1), 450 k at the inflow.