Numerical Simulation Results Research Articles

Effect of warhead shape on the high‐velocity impact of short carbon fiber reinforced PEEK composite

AbstractTo investigate the mechanical response and failure mechanism of short carbon fiber reinforced polyether‐ether‐ketone (SCFR‐PEEK) composite under high‐velocity impact of foreign bodies of different shapes, high‐velocity impact experiments and numerical simulations of SCFR‐PEEK composite were carried out with blunt projectile, hemispherical projectile, and ovoid projectile in the velocity range of 33.6 ~ 163.8 m/s. The results show that the ballistic limit of the ovoid projectile is the highest and the hemispherical projectile is the lowest in the range of impact velocities studied. The impact resistance of the ovoid projectile is better than that of the blunt projectile. The hemispherical projectile has the weakest impact resistance at lower velocities, and it is rather better than that of the blunt projectile and ovoid projectile at higher velocities. The damage morphology and change trend of the target plate under the impacts of different warheads are different. In addition, the use of Extended Drucker‐Prager models can accurately describe the mechanical behavior of SCFR‐PEEK under high‐velocity impact. The results of experiments and numerical simulations corroborate with each other, revealing the influence laws of the shape of the warhead and the impact velocity on the impact resistance and failure mechanism of the SCFR‐PEEK target plate.Highlights T700 short carbon fiber‐reinforced PEEK thermoplastic composite was used. SCFR‐PEEK shows the best resistance to ovoid projectile impact. Cracking and spalling of SCFR‐PEEK consume the impact energy. The form of damage in SCFR‐PEEK affects the amount of energy absorption.

Analysis of Temporal and Spatial Characteristics and Influencing Factors of Construction Deformation of Super-Large Deep Foundation Pit in Thick Sand Stratum

To the aim of this paper is to study the structural and environmental deformation characteristics caused by the excavation of a very large deep foundation pit in the sandy soil area of Beijing. This paper is based on numerical simulation and field monitoring results and these results are compared with the deformation data of a soft soil foundation pit in the Shanghai area. The results show that the influence of the environment surrounding the super-large deep foundation pit project studied in this paper is obviously too great. With the progress of construction, the deformation rate and deformation amount of the column at the side of the foundation pit are obviously higher than that of the column in the middle area. Due to the “hysteresis” of stress transfer in the sand, the settlement of the roof of the north wall is delayed and the deformation range is smaller than that of the south wall. Compared with the conventional foundation pit, the influence area of the surrounding surface is larger, reaching 4 He (He is the depth of the foundation pit). Δvmax (the maximum surface settlement) is between 0.2~2.3% He, and the relationship between δvmax = 1.43% Vwm. Through orthogonal experiments and numerical simulation, it is concluded that the deformation of foundation pit structure and its surrounding environment is more sensitive to excavation unloading, precipitation amplitude, and column spacing. It is also concluded that the strong, medium, and weak influence areas of the bottom uplift after foundation pit construction are (0~0.07) × L, (0.07~0.14) × L, and (0.14~0.5) × L, respectively (L is the width of foundation pit). When the embedment ratio is between 1.8~2.4, the displacement mode of the parapet structure is T mode; when the embedment ratio is between 2.4~3.4, the displacement mode of the parapet structure is RB mode.

Analysis of Piecewise-Linear Hopfield Neural Network Model Based on a Novel Fractional-Order Memristor and Its Application to Image Encryption

This paper introduces a novel three-neuron memristive synaptic coupling Piecewise-Linear Hopfield Neural Network (PWL-HNN) and extends it to fractional order. This study delves into studying the dynamical behaviors of the fractional-order memristive PWL-HNN using bifurcation diagrams, largest Lyapunov exponential spectra, Poincaré cross-sections, attraction basins, and two-parameter bifurcation diagram, and exploring variations in PWL activation function parameters, memristive coupling strengths, and initial conditions. Subsequently, an equivalent circuit model of the fractional-order memristive PWL-HNN on the Cadence/PSpice platform is developed, verifying its dynamic behavior through circuit simulation experiments. Additionally, a digital circuit of the fractional-order memristive HNN model is implemented on the LabVIEW platform, with NI PXIe equipment utilized for hardware circuit realization. The experimental results align closely with numerical and circuit simulation results, affirming the theoretical analysis’s accuracy. Lastly, this paper investigates the generation of a pseudo-random sequence using fractional-order memristive HNN and explores an image encryption algorithm in conjunction with the DNA algorithm, assessing the encryption algorithm’s reliability through security analysis.

Risk Identification Method and Application of Roof Water Inrush Under Multi-Working Face Mining

Adjacent, multi-working face mining can expand the range of disturbed overburden, increasing the risk of triggering roof water inrush, which threatens the safe operation of coal mines. In this paper, we propose a risk identification method for roof water inrush under multi-working face mining conditions based on the theory of Key Strata and Full Mining Disturbance. Firstly, the key strata of the overburden are determined based on lithological and structural data from exploration boreholes. A formula is then derived to calculate the critical dimension (L) of the working face that could induce a fracture in the key stratum. The relationship between L and the combined width of the preceding and adjacent working faces is analyzed to assess whether the key stratum is fractured and how it affects the preceding working face. Finally, the height of the water-conducting fracture zone is predicted. The impact of repeated disturbances from multi-working face mining is evaluated to determine whether the height of the water-conducting fracture zone in the preceding working face increases, thereby enabling risk identification for roof water inrush under multi-working face mining conditions. Taking the multi-working faces of the Banji Coal Mine in Anhui Province as a case study, the predicted height of the water-conducting fracture zone is 60 m, with no risk of delayed roof water inrush in the preceding working face. Both numerical simulation results and field measurements of the development height of the water-conducting fracture zone confirm the effectiveness of this method. It is capable of accurately predicting the development height of the water-conducting fracture zone under multi-working face mining conditions and identifying the associated risk of roof water inrush, thus providing a valuable reference for ensuring safe mining operations in multi-working face mining conditions.

Numerical Study on Compound Heat Transfer Enhancement by New Inserts of Lubricating Oil in Tubes

In this study, we propose a novel device, the coaxial cross double-twisted tape and vortex generator (CV), to significantly enhance the heat transfer performance of high-viscosity lubricating oil. Based on numerical simulation results, we thoroughly analyze the thermal–hydraulic behavior of the lubricating oil within the enhanced pipe. We explore four distinct geometrical configurations of the CV. Among them, a particular variant, the CVCP, achieves the most remarkable enhancement in heat transfer performance. To further understand the heat transfer characteristics of CVCPs, we examine the effects of twist ratios (y = 2.0, 3.0, 4.0, and ∞) and angles (α = 0°, 30°, and 60°). The results reveal that, across a wide Reynolds number range (40 ≤ Re ≤ 840), the heat transfer performance of CVCP is closely related to the twist ratio and angle. Notably, the performance evaluation criterion (PEC) of a tube with CVCP inserted is 1.14–1.54 times higher than that of conventional twisted tapes. Overall, these findings provide valuable insights into optimizing heat transfer in high-viscosity fluids and serve as a meaningful reference for future research and engineering applications aimed at enhancing lubricating oil heat transfer within tubes.

Effect of High Temperature on the Mechanical Performance of Additively Manufactured CoCrNi Medium-Entropy Alloy Octet-Truss Lattice Materials

In this study, the effect of high temperature on the mechanical performance of CoCrNi medium-entropy alloy octet-truss lattice material fabricated via laser powder bed fusion (LPBF) is investigated by compressive test and numerical simulation method. The results reveal that the strength and energy absorption performance of CoCrNi octet-truss lattice material with a hollow truss are higher than those of ones with a solid truss; however, they diminish by 30% and 50%, respectively, as temperature rises from 25 °C to 600 °C. As the temperature rises, the potential barrier for dislocation slip decreases, making it easier for dislocations to move at high temperatures and thus reducing the strength. CoCrNi octet-truss lattice materials present the failure mechanism of progressive collapse at varied temperatures. Meanwhile, the mechanical performance of the experimental testing agreed well with numerical simulation results. The numerical results show that the strength and energy absorption properties of the CoCrNi lattice materials increase as the relative density, however, decreases with increasing temperature. Additionally, CoCrNi octet-truss lattice materials maintain exceptional energy absorption performance at varied temperatures.

The architecture of sponge choanocyte chambers is well adapted to mechanical pumping functions

Sponges, the basalmost members of the animal kingdom, exhibit a range of complex architectures in which microfluidic channels connect multitudes of spherical chambers lined with choanocytes, flagellated filter-feeding cells. Choanocyte chambers can possess scores or even hundreds of such cells, which drive complex flows entering through porous walls and exiting into the sponge channels. One of the mysteries of the choanocyte chamber is its spherical shape, as it seems inappropriate for inducing directional transport since many choanocyte flagella beat in opposition to such a flow. Here, we combine direct imaging of choanocyte chambers in living sponges with computational studies of many-flagella models to understand the connection between chamber architecture and directional flow. We find that those flagella that beat against the flow play a key role in raising the pressure inside the choanocyte chamber, with the result that the flow rate and mechanical pumping efficiency reach a maximum at a small outlet opening angle. Comparison between experimental observations and the results of numerical simulations reveal that the chamber diameter, flagellar wave number, and the outlet opening angle of the freshwater sponge Ephydatia muelleri, as well as several other species, are related in a manner that maximizes the mechanical pumping functions. These results indicate the subtle balances at play during morphogenesis of choanocyte chambers, and give insights into the physiology and body design of sponges.

Comprehensive Analysis of Ballasted Track Sleeper Dynamics for High-Speed Trains: A Three-Dimensional Flexible Track Model

This paper investigates the response of a ballasted track sleeper support under varying high-speed train loads with an emphasis on the integration of flexible track–train interaction methods. To achieve this, a 3D rigid high-speed train model coupled with a flexible ballast track is developed. A multibody China Railway High-Speed 3 (CRH3) train-type SIMPACK model consisting of six coupled vehicles with a 35-degree-of-freedom multibody subsystem is established. The track rail and sleeper are modeled using Ansys Parametric Design Language (APDL) software as flexible components and then exported to the multibody SIMPACK model. Additionally, the paper analyzes the influences of track irregularities on the vibration characteristics of the sleeper. The model is successfully validated against field-measured simulation data reported in the literature. The results of numerical simulations demonstrate that the dynamic vibrational response of the sleeper is significantly influenced by the presence of uneven irregularities and increasing train speeds. Moreover, it has been found that the response of the sleeper in the vertical direction is more sensitive in the middle section of the flexible track.

Optimal subsampling for double generalized linear models with heterogeneous massive data

. With the development of information technology, massive data under heterogeneous characteristics are generated in the economic, financial, and other fields. Traditional statistical models and existing statistical methods are often inadequate for handling dispersion modeling problems with heterogeneous massive data. In this article, the optimal subsampling of double generalized linear models is studied in heterogeneous massive data environments. Under certain conditions, the optimal subsampling probabilities of the double generalized linear models with heterogeneous data are derived based on the A-optimality criterion and L-optimality criterion, respectively. Furthermore, a two-step algorithm based on uniform sampling is developed, and the asymptotic properties of the subsample estimator from this algorithm are discussed. The results of numerical simulations and a real example show that the algorithm can improve estimation accuracy and decrease computational costs to some extent.

Identifying All Internal Forces in Existing Reinforced Concrete Components Using the Stress Release Method.

The internal force state in concrete components is a crucial factor in evaluating the safety performance of existing buildings, bridges, and other concrete structures, while theoretical and numerical analysis of an ideal model may not accurately capture the actual internal forces within concrete components. This study introduces the basic principles of stress release technology for identifying internal forces in existing reinforced concrete components and provides a detailed derivation of normal and shear strains of component sections under each internal force component. It demonstrates that the internal forces of reinforced concrete sections can be accurately identified by testing the strain on the midpoint of three surface sides. A finite element model is established to investigate the relationship between groove depth and groove side length when normal or shear stress is released to zero, as well as the impact of reinforcement ratio on the stress release level. Experimental research is conducted using the grooving method to identify internal forces in reinforced concrete components under different external loads. The test results exhibit strong agreement with numerical simulation results. Additionally, the identification errors for axial forces and bending moments are within 10%, underscoring the feasibility of measuring internal forces in existing reinforced concrete components through the stress release method.

Static and Dynamic Time Filtering Techniques for Hybrid RANS-Large Eddy Simulation of Non-Stationary Turbulent Flows

Abstract Unsteady turbulent wall bounded flows can include complex flow physics such as temporally varying mean pressure gradients, intermittent regions of high turbulence intensity, and interaction of different scales of motion. As a representative example, pulsating channel flow presents significant challenges for newly developed and existing turbulence models in computational fluid dynamics (CFD) simulations. The present study investigates the performance of the dynamic hybrid Reynolds-averaged Navier-Stokes-large eddy simulation RANS-LES (DHRL) modeling framework for nonstationary turbulent flows using two variants of an exponential temporal filter for calculating statistics of the resolved turbulent flow. The first adopts a static filter size (static exponential time filtering-SETF) based on the characteristic time scale of imposed mean flow unsteadiness. The second uses a dynamic filter size (dynamic exponential time filtering-DETF) to vary the filter size based on local statistics of the resolved turbulent flow. Both of the time-filtered variants and the baseline (stationary) form of DHRL are compared against an industry-standard RANS model, monotonically integrated large eddy simulation (MILES), and a conventional hybrid RANS-LES (HRL) models. Model performance is evaluated based on comparison with previously documented direct numerical simulation (DNS) and LES results. Simulations are performed for a fully developed flow in a channel with time-periodic driving pressure gradient. Results highlight the relative merits of each model type and indicate that the use of a time-filtering technique improves the accuracy of the DHRL model for nonstationary flow, and that a dynamic filter offers clear advantages over a static filter.

Detecting droplets and bubbles in oil–gas–water three-phase medium via ultrasonic A-scan signal-assisted B-mode imaging method

Abstract Accurately detecting the parameters of bubbles and droplets in the oil-gas-water three-phase medium is essential to critical decision-making about industrial production. An ultrasonic A-scan signal-assisted B-mode imaging (AS-assisted-BI) method that combines a B-mode imaging (BI) method and an A-scan signal (AS) method is developed to simultaneously visualize the oil-gas-water three-phase medium, distinguish the gas bubble and oil droplet, and measure the parameters about their sizes and locations. The applicability of the plane wave imaging (PWI) method for visualizing the oil-gas-water three-phase medium with less computational cost was confirmed. Then, the influence of the bubble and droplet characteristics, such as acoustic impedance difference, size, and location, upon the ultrasonic propagation mechanism are studied to understand the B-mode image and A-scan signal as the design basis of the BI and AS method. The BI method locates the least key points from the B-mode image based on the PWI method compared with the conventional industrial B-mode image method. The AS method automatically locates the key point from the A-scan signal rather than manually marking it in the previous study. Two options for the AS-assisted-BI method, suitable for different detection requirements and applications, have been designed. The numerical simulation and experimental results demonstrated that the proposed method received excellent precision, robustness, and efficiency for detecting the acoustic impedance difference between the bubble and droplet, the longitudinal location of the bubble front surface, and the droplet’s size and center location.

Pressings shape evaluation by modern contactless methods

As part of the Industry 4.0 concept, companies are adopting new processes that utilize contactless methods to assess the shapes of pressings. Evaluating the pressings is essential due to the springback phenomena that occur after plastic deformation, which is more pronounced when high-strength steels are used in car bodies. Although photogrammetric methods based on 2D images have been used in the industry for over a decade, 3D optical scanning methods are preferred because they offer increased precision. This article evaluated cylindrical pressings made of dual-phase steel DP800 with a thickness of 1.6 mm—specifically flat-bottomed and hemispherical-bottomed cups. The shape of the pressings was determined using optical scanning with the GOM Scan 1 device alongside a photogrammetric system called ARGUS. The surfaces obtained from both methods were then compared to assess the accuracy of the scanned surface against the real surface acquired through photogrammetry. The scanned surfaces of the pressings were also used to compare the results of numerical simulations conducted in PamStamp software. In these simulations, the material was modelled using two sets of constitutive laws: the Hill48 yield law combined with the Hollomon hardening law as the first set and the Vegter Lite yield law combined with the Krupkowski hardening law as the second set. Real cups with a diameter of 50 mm were created using a deep-drawing process on the Erichsen 145-60 testing machine, starting with a blank diameter of 90 mm and lubricated with plastic foil to preserve the electrochemically etched grid. A comparison between the scanned surfaces and the real surfaces obtained through photogrammetry showed a strong correlation, validating 3D scanning as an effective method for evaluating pressing shapes. Furthermore, comparing the scanned surfaces with the results of the numerical simulations demonstrated similar findings for both sets of constitutive laws used to model the dual-phase steel in the experiments.

Analysis and image encryption of memristive chaotic system with coexistence bubble

Abstract In recent years, the phenomenon of multistability has attracted wide attention. In this paper, a memristive chaotic system with extreme multistability is constructed by using a memristor. The dynamic behavior of the system is analyzed by Poincar mapping, a time series diagram, and a bifurcation diagram. The results show that the new system has several significant characteristics. First, the new system has a constant Lyapunov exponent and transient chaos and one complete Feigenbaum tree. Second, the system has the phenomenon of bifurcation map shifts that depend on the initial conditions. In addition, we find periodic bursting oscillations, chaotic bursting oscillations, and the transition of chaotic bursting oscillations to periodic bursting oscillations. In particular, when the system parameters take different discrete values, the system generates a bubble phenomenon that varies with the initial conditions, and this “bubble” can be shifted with the initial values,this has rarely been seen in the previous literature. The implementation by field-programmable gate array(FPGA) and analog circuit simulation show close alignment with the MATLAB numerical simulation results, validating the system's realizability. Additionally, the image encryption algorithm integrating DNA-based encoding and chaotic systems further demonstrates its practical applicability.

Reservoir Architecture of Turbidite Lobes and Remaining Oil Distribution: A Study on the B Formation for Z Oilfield of the Illizi Basin, Algeria

The turbidite lobe is a significant reservoir type formed by gravity flow. Analyzing the architecture of this reservoir holds great importance for deep-water oil and gas development. The main producing zone in Z Oilfield develops a set of turbidite lobes. After more than 60 years of development, the well spacing has become dense, providing favorable conditions for detailed research on reservoir architecture of this kind. Based on seismic data, core data, and logging data, combined with the results of reservoir numerical simulation, this paper studies the reservoir architecture of turbidite lobes, displays the distribution of remaining oil in the turbidite lobes, and proposes development policies suitable for turbidite lobe reservoirs. The results show that the turbidite lobes can be classified into four sedimentary microfacies: lobe off-axis, lobe fringe, interlobe facies, and feeder channel facies. The study area is mainly characterized by multiple sets of lobes. There are feeder channels running through the south to the north. Due to the imperfect well pattern, the remaining oil is concentrated near the lobe fringe facies and the gas–oil contact. It is recommended to tap the potential of the turbidite lobes by adopting the “production at the off-axis lobes facies and injection at the lobe fringe facies (POIF)”. The study on the reservoir architecture and remaining oil of turbidite lobes has crucial guiding significance for the efficient development of Z Oilfield and can also provide some reference for developing deep-water oilfields with similar sedimentary backgrounds.

DYNAMIC MODELING AND ANALYSIS OF TUMOR ANGIOGENESIS AND ANTI-ANGIOGENESIS TREATMENT

Angiogenesis plays an important role in the development of tumor since it allows for the delivery of oxygen and nutrients. Understanding the dynamics of angiogenesis is essential for accurately characterizing tumor growth during the vascular phase and for developing models that optimize therapeutic strategies. In order to provide beneficial information and theoretical models for clinical research of tumor therapy strategies, a new mathematical model is established to describe the interaction between vascular epithelial cells and tumor cells. Through the stability analysis of the equilibria, the results show that in the absence of therapeutic intervention, the number of tumor cells will naturally stabilize at a positive value. Further, the anti-angiogenesis treatment term is added to the model to investigate the effects of anti-vascular therapy. The results indicate that anti-angiogenic therapy alone cannot completely eliminate a tumor, but can observably reduce the number of the tumor. Finally, numerical simulations are carried out to investigate the therapeutic effect of anti-vascular therapy combined with traditional treatment. The numerical simulation results show that the anti-angiogenesis therapy is a good adjunct to traditional therapy, which is beneficial to the design of better tumor treatment program.

An ultra-high sensitivity methane gas sensor based on the vernier effect with cryptophane- a film deposited in the photonic crystal fiber

Abstract Methane gas, due to its high flammability, is convenient for people’s daily lives, but its flammability poses safety hazards. Methane tends to explode when mixed with air. Therefore, it is particularly important to be able to effectively detect methane gas concentrations. A new methane gas sensor is presented in this paper. It is extremely sensitive to the reaction of methane gas. It consists of two fiber Sagnac interferometer (SI) loops, which utilize the vernier effect. The two fiber SI loops remain parallel. The optical fiber structure of the effective sensing in the sensing SI loop and the effective sensing in the reference SI loop are the same. Both of them adopt the polarization-maintaining photonic crystal fiber (PM-PCF) designed in this paper. However, the sensing SI loop uses a two-step filling technique to block small air holes and an immersion technique to deposit methane gas sensitive film on large air holes in PM-PCF. The sensing capability of the methane gas sensor was evaluated utilizing the finite element method (FEM). The numerical simulation results show that under the condition of the concentration of methane gas in the environment is 0-3.5%, the average sensitivity of two parallel Sagnac loops is 260.86 nm/%. Compared with other fiber optic methane gas sensors, the sensitivity of the sensor designed by this scheme is significantly improved, which provides a valuable reference and direction for the development of new methods and the design of ultra-sensitive methane gas sensors.

Experimental Study on Sand Removal by a Downhole In Situ Spiral-Swirl Natural Gas Hydrate Coupling Separator

In natural gas hydrate exploitation, the large amount of sand production directly or indirectly leads to the low efficiency of hydrate exploitation and even the termination of exploitation. A spiral-cyclone coupling separator was used to achieve the separation of mud and sand. In this study, based on the actual size of the spiral-cyclone separator for natural gas hydrate, an experimental prototype of the spiral-cyclone separator suitable for indoor experiments was processed, and an indoor experimental system was built. A pressure loss experiment on the hydrate separation device was carried out, and the results proved the correctness of the numerical simulation model of the spiral-swirl separator and the calculation results. The influence of the inlet flow rate of the separator on the separation effect was studied. It was found that with an increase in the flow rate, the mud/sand separation area began to move up, and the mud/sand settlement area at the bottom appeared to have different degrees of mud/sand accumulation. The indoor experimental results and numerical simulation results show that the separation efficiency increases with the flow rate increase in the range of 5–25 m3/h. This study can provide theoretical guidance for the indoor experimental verification of downhole in situ separators.

Flexural Performance of an Innovative Girder-to-Pier Joint for Composite Bridges with Integral Piers: Full-Scale Test.

To reduce the maintenance requirements during the service life of highway bridges and enhance the cracking resistance of concrete slabs in the hogging moment zone of continuous composite girders, this paper proposes an innovative girder-to-pier joint for composite bridges with integral piers. Compared to the existing ones, this new joint has structural differences. The middle part of the embedded web is hollowed out to facilitate the construction, and the upper and bottom flanges of the steel girder within this joint are widened. Moreover, cast-in-place ultra-high-performance concrete (UHPC) is applied instead of normal concrete (NC) only on the top surface of the pier. A full-scale test was carried out for this new joint to evaluate the load-displacement relationship, load-strain relationship, crack initiation, and crack propagation. Compared with the numerical simulation results of the reference engineering, the test results demonstrated that the proposed joint exhibited excellent flexural performance and cracking resistance. This paper also proposes a calculation method for the elastic flexural capacity of the girder-to-pier joint incorporating the tensile strength of UHPC, and the calculated result was in good agreement with the experimental result.

Magnetohydrodynamic effects on liquid metal flows in an open channel for fusion plasma facing components with a transverse magnetic field

Abstract Laminar magnetohydrodynamics film flows in an open channel of arbitrary electrical conductivity under the influence of a transverse magnetic field are investigated. The effects of the magnetic field, channel conductivity, and channel width on current and velocity distributions are discussed. The present research establishes quantitative scaling law for the magnetic field's impact on the film thickness, utilizing Fourier eigenfunction series and comprehensive physical modeling. The scaling law is validated through direct numerical simulation results and experimental data, which accounts for factors that influence the film thickness, including the Reynolds number (volume flow rate), channel inclined angle, and magnetic field strength. Additionally, the physical mechanism governing the three-dimensional evolution of magnetohydrodynamics films is explored, which finds that a strong magnetic field introduces a Lorentz separation eddy and destabilizes the initially stable, flat film. The present investigations will contribute to the design of flowing liquid metal plasma facing components in tokamak fusion reactors.