Simple Simulation Method Research Articles

Simplified inverse distance weighting-immersed boundary method for simulation of fluid-structure interaction

When simulating fluid-structure interaction (FSI) problems involving moving objects, the implicit inverse distance weighting-immersed boundary method (IDW-IBM) developed by Du et al. [1] has to construct a large square correlation matrix and solve its inversion at each time step. In this work, a simplified inverse distance weighting-immersed boundary method (SIDW-IBM) is proposed to eliminate the intrinsic limitations in the original implicit IDW-IBM. Through error analysis using Taylor series expansion, a second order approximation can be derived, which allows us to approximate the large square correlation matrix into a diagonal matrix; thereby, we proposed the SIDW-IBM based on this second order approximation to explicitly evaluate the velocity corrections, where the needs to assemble the large correlation matrix and inverse it are circumvented. Owing to the fact that the inverse distance weighting interpolation removes the limitations in the Dirac delta function, the proposed SIDW-IBM has been successfully implemented on the non-uniform meshes to further improve the computational efficiency. The proposed SIDW-IBM is integrated with the reconstructed lattice Boltzmann flux solver (RLBFS) [2] to simulate some classic incompressible viscous flows, including flow past an in-line oscillating cylinder, flow past a heaving airfoil, and flow past a three-dimensional flexible plate. The good agreement between the present results and reference data demonstrates the capability and feasibility of the SIDW-IBM for simulating FSI problems with moving boundaries and large deformations.

Ground-to-air aircraft infrared image deblurring based on imaging degradation simulation

The issue of infrared image deblurring has been a significant concern. However, in some specific scenes, the current mainstream deblurring algorithms based on optimization or deep learning fail to provide satisfactory results. Aiming to address the ineffectiveness of deep learning methods due to the low-cost datasets' unavailability for specific scenes, we innovatively propose a relatively simple full-chain imaging degradation simulation method using ground-to-air aircraft infrared imaging scene as an example, which considers the effects of blur and noise caused by the atmosphere, imaging system, target motion and detector. Through this method, we could generate abundant blur-clear image pairs by altering various parameters. To enhance the neural network’s generalization ability and the deblurring performance in the specific scenes, we employ a two-step approach: pretraining on the public GoPro dataset and subsequent finetuning on the simulation dataset. After testing on the simulation dataset and some real-world images, we have discovered the importance of selecting a pretraining dataset that closely matches the scene degradation mode. Additionally, regardless of whether the model is pre-trained on the UIRD or GoPro dataset, there are significant enhancements in the deblurring effect following finetuning with our constructed simulation dataset. In summary, compared to the traditional deconvolution methods and the methods trained on a general dataset, our approach not only exhibits superior deblurring capabilities but also effectively mitigates noise and prevents the occurrence of artifactual textures such as ringing artifact.

A novel simplified simulation method for the precooler based on the virtual source term: modeling, validation and application

Precooling technology is one of the promising approaches for expanding the flight envelope of conventional turbine engines and enhancing flight performance at high Mach numbers. Within this domain, a crucial challenge is to rapidly and accurately obtain the flow and heat transfer characteristics of the precooler. Currently, full-size simulation of the precooler is impractical, while simplified and fast simulation methods employed in previous research have exhibited certain deficiencies, including excessive simplification and unconvincing validation. In this study, a novel simplified simulation method for the annular precooler based on the virtual source term model was proposed. This method comprehensively considered the axial and radial non-uniformity of airflow caused by the coupling effect between the precooler and the inlet channel in the actual flow field. Subsequently, systematic validations of the reliability and superiority of this method were conducted, along with its application in the overall performance calculation of the precooled engine. The results demonstrate that the simplified method proposed in this paper showcases higher accuracy than the methods employed in previous research. Compared with the real model, the relative errors of the overall parameters are within ± 1 %, and the relative errors of the distortion indices for total temperature and total pressure are 5.1 % and −1.5 %, respectively. Meanwhile, the number of computational mesh cells is reduced by more than 95 %. Moreover, the first application of the simplified method in the overall performance calculation of the precooled engine reveals that the traditional low-dimensional model underestimates both the total pressure loss of the precooler and the fuel consumption for precooling, resulting in larger calculation deviations in the thrust and equivalence ratio, respectively. The values of thrust calculated with the high-dimensional virtual model show an average decrease of 2.01 % compared to those derived from the low-dimensional model. In addition, a higher Mach number results in lower effectiveness, higher air inlet temperature, and reduced resistance of the precooler to heat exchange imbalance caused by flow non-uniformity. These factors lead to an escalating relative deviation of the equivalence ratio between the two models, reaching 26.45 % at Mach 5.

Sensitivity analysis of turbine stage aerothermal characteristics and blade cooling performance considering combustor swirl and hot spot

This paper investigates the global sensitivity of high-pressure-turbine (HPT) first stage cascades aerothermal characteristics and blade cooling performance under the influence of combustor swirl and hot spot. The combustor outflow conditions impact on turbine working performance and robustness. This paper is focused on the influence of uncertain combustor swirling flow and hot spot, rather than deterministic working conditions. A simplified combustor outflow simulation method is firstly proposed, and the effects of combustor outflow are quantified by combining chaos polynomial expansion with Sobol’ decomposition method. The results show that different rotating directions of the swirl lead to restricted influences on the averaged aerothermal performance of the turbine stage, but significantly affects its robustness. The positive swirl increases the total pressure loss generated by the lower passage vortex of the stator cascade, and the high uncertainty region of the stator cascade total pressure loss profile is the combined products of the residual swirl and the interaction between the passage vortex and mainstream. The total pressure loss of the rotor cascade due to leakage vortex has low sensitivity to the hot spot and swirl strength, while the total pressure loss generated by the passage vortex is affected by hot spot temperature. Temperature distribution affected by the passage vortex is sensitive to swirl strength. Generally, uncertainty variance of stage aerothermal parameters with positive swirl is about 30% larger than that of the negative case, since the positive swirl has stronger interactions with the blades, leading to more significant uncertainty. However, the averaged heat transfer coefficients with positive swirl are 37% less sensitive, compared to the negative swirl case. The results give better understanding on the influence mechanisms of turbine inflow conditions, emphasize the meaning of investigating uncertain characteristics of the turbine cascades. Investigations of this article provide reference for robust turbine blade cooling design.

Modeling two-dimensional ice shape based on fractal interpolation

The ice accretion data obtained from ice wind tunnel tests reveal a multiscale structure and rough surface. In the follow-up aerodynamic evaluation of icing airfoils, simplified two-dimensional ice shapes are generally used as substitutes, but this simplification changes the aerodynamic effects of the original ice shape. Therefore, finding a simple and effective two-dimensional ice shape simulation method is urgent. Due to the self-similarity characteristics of ice shape surfaces, fractal interpolation is proposed for ice shape simulation. First, the geometric characteristics of the ice shapes are analyzed to determine interpolation points, and an iterative function system is constructed for interpolation simulation. Considering the influence of various characteristics of ice shapes on aerodynamics, interpolation parameters are limited to simulating more realistic ice shapes. High-order numerical simulation methods were utilized to numerically simulate and analyze the aerodynamic characteristics of icing airfoil while also verifying the feasibility of fractal interpolation for simulating ice shapes. The analysis revealed that this method could effectively simulate ice profiles of various feature scales with minimal ice shape data. These simulated shapes closely resemble real ice formations and maintain the original aerodynamic characteristics of the icing airfoil. This method can be used to improve the computational accuracy of ice accretion codes and provide improvement strategies for complex ice shape prediction; thus, this method has great application prospects in engineering.

Simulation of Flow and Pressure Loss in the Example of the Elbow

One of the most basic issues in fluid mechanics is the description of flow in closed flows; more precisely, the calculation of pressure drops and the description of the flow form. Therefore, in this paper, the numerical simulation of the flow through the elbow was presented. This case was used to comprehensively describe the most important phenomena that should be taken into account during closed flows. The elbow was chosen as one of the most frequently used fittings in practice. The simulation was made with ANSYS Fluent, with the use of the turbulent model k-ω, SIMPLE simulation method, and at Reynolds number . The minor and major pressure loss were presented and discussed in the paper. The minor loss coefficient at the high Reynolds number was equal to around 0.2, which is close to the value of 0.22 used in engineering calculations. The influence of the Reynolds number on the shift of the stream separation point in the elbow was described. The secondary flow in the elbow was observed and the vortex structure was discussed and shown with the use of the Q-criterion (Q iso surface for level 0.005). This analysis allowed us to better visualize and describe the complex flow structure observed in the investigated case.

Classical and quantum computing of shear viscosity for (2+1)D SU(2) gauge theory

We perform a nonperturbative calculation of the shear viscosity for (2+1)-dimensional SU(2) gauge theory by using the lattice Hamiltonian formulation. The retarded Green’s function of the stress-energy tensor is calculated from real time evolution via exact diagonalization of the lattice Hamiltonian with a local Hilbert space truncation, and the shear viscosity is obtained via the Kubo formula. When taking the continuum limit, we account for the renormalization group flow of the coupling but no additional operator renormalization. We find the ratio of the shear viscosity and the entropy density ηs is consistent with a well-known holographic result 14π at several temperatures on a 4×4 honeycomb lattice with the local electric representation truncated at jmax=12. We also find the ratio of the spectral function and frequency ρxy(ω)ω exhibits a peak structure when the frequency is small. Both the exact diagonalization method and simple matrix product state classical simulation method beyond jmax=12 on bigger lattices require exponentially growing resources. So we develop a quantum computing method to calculate the retarded Green’s function and analyze various systematics of the calculation including jmax truncation and finite size effects, Trotter errors and the thermal state preparation efficiency. Our thermal state preparation method still requires resources that grow exponentially with the lattice size, but with a very small prefactor at high temperature. We test our quantum circuit on both the Quantinuum emulator and the IBM simulator for a small lattice and obtain results consistent with the classical computing ones. Published by the American Physical Society 2024

Dynamic control of pre-stressed cable systems by using frictional sliding cables

Passive dynamic control with integrated dampers is an efficient strategy for the vibration of a cable-strut system. Except the rigid components, the flexible components are also a triable direction as the integrated damper, especially for the continuous cable systems. This paper proposes a novel dynamic control method for pre-stressed cable systems by using frictional sliding cables. Firstly, a simplified dynamic simulation method is introduced. The friction of sliding cables can be considered in the dynamic analysis of a continuous cable system. Secondly, two numerical examples with sliding cables including the types of Levy and Geiger are established. The results show that frictional sliding cables can reduce the structural dynamic response. Thirdly, a dynamic experiment of a Geiger-type cable dome with sliding ridge cables is carried out. The acceleration of the structure during vibration is recorded and compared with the results of the conventional configuration. The dome with sliding cables exhibits higher damping ratios, indicating superior vibration reduction capabilities. The frictional energy dissipation of this study can be taken as a dynamic control strategy for continuous cable structures during the design and analysis process.

Wind load resistance of prefabricated ALC-rock wool external wall panel system

Exterior wall enclosure systems in steel-frame residential buildings are prone to extensive cracking and detachment under wind loads. This study, through research and comparison of commonly used materials, identified the exterior wall panel system with the optimal comprehensive performance. To assess the wind load resistance of this system, 11 sets of tensile tests were conducted considering anchor bolt quantity and the bonding rate parameters between autoclaved lightweight concrete (ALC) panels and rock wool boards. The research investigated the failure modes, load-bearing capacity, and failure mechanisms of the external wall panel system under wind suction loads. Based on the experimental findings, a simplified finite element simulation method was proposed and subjected to parameter analysis. This analysis explored the impact of anchor bolt quantity and layout. The research indicates that under tensile loads, the external wall panel system primarily experiences interfacial damage between rock wool boards and coating mortars. Its load-bearing capacity consists of the net bonding force between rock wool boards and finishing layers, as well as the mechanical force between fiberglass mesh and anchors. The load bearing capacity can be enhanced by strengthening the overall integrity of the system and by expanding the contact area between the fiberglass mesh and the anchor plate, with specific structural measures such as increasing the number of anchor, the bond ratio, and the diameter of the anchor plate. The arrangement of anchors has a minor impact on the load-bearing capacity of the external wall panel system but significantly affects the deformation of rock wool boards. Based on experimental and finite element studies, a simplified calculation method for the tensile load-bearing capacity of external wall panels for engineering applications was further developed and proven to be accurate through comparison with experimental results.

Application of the fast 3D simplified simulation method for the large CAP1400 nuclear island evaporator based on the coupled source term method

As for the evaporator of the large CAP1400 nuclear power plant, it has a large volume with numerous tubes along with the complex flow heat transfer phenomenon. The traditional direct simulation method usually takes a lot of time and computing resources to obtain the flow heat transfer data. To solve the problem, a fast simulation method established on the porous medium source term was herein proposed. In this simplified simulation method, the complex evaporator model is replaced with the porous medium model, where the derived heat and momentum source terms are added into the governing equation to control the heat flows. Five kinds of simplified evaporator models with different numbers of pipes were set to be the research objects, the internal flows inside the evaporator were studied with the traditional direct simulation method and the newly proposed simplified simulation method. Via comparative analysis, it can be found that: 1) The newly proposed simplified simulation method accurately captures the distribution characteristics of pressure, temperature, and entropy production in the evaporator, serving as a viable alternative to traditional direct simulation methods. Specifically, the average simulation errors for inlet-outlet pressure difference and temperature difference are both less than 5 % and 7 %, respectively. 2) The newly proposed simplified simulation method can capture the mutual interference effects between the evaporator and the nuclear main pump. When the evaporator is connected in series with the main nuclear pump, the average head of the main pump increases by 0.34 m, while the efficiency decreases by an average of 0.34 %. The average simulation errors of the simplified simulation method are 0.06 m and 0.13 %, respectively. 3) The application of the simplified simulation method leads to a significant 85 % decrease in the average computational cost for evaporator calculations and a notable 36 % decrease for combined calculations of the evaporator and main pump. The study here is expected to provide technique support for the simulation and evaluation of the large nuclear island.

Study on radon release behaviors of the tubular flow-through radon source with natural radium-bearing materials

To obtain a radon source that is easy to access natural radium-bearing raw material and does not require the approval of relevant departments, the tubular flow-through radon source using radium-bearing ore as the radon-generating material was designed. Based on the theories of radon diffusion-convection migration in porous media, the simplified calculation formula and numerical calculation models of radon activity concentration at the outlet of the tubular flow-through radon source were established, and the radon release rules of the tubular flow-through radon source were studied using a combination of simplified calculation formulas, numerical simulations, and experiments, respectively. The results show that (1) the radon activity concentration at the outlet of the tubular flow-through radon source was dominated by mass (or the volume) of the natural radium-bearing raw material, free radon production rate, and gas flow rate. (2) When the range of radon activity concentration at the outlet is 260–1308 Bq m-3, the relative deviation of the three methods is less than 2.62%. (3) The simplified calculation formula and numerical simulation method proposed in this paper can provide a reference for the design and control of the radon activity concentration of a tubular flow-through radon source.

Analysis and optimization of brace system in scaffold

Scaffold consists of horizontal components, vertical components and lateral braces, while the lateral stiffness of structure is mainly provided by brace system. Brace system can be classified into three groups: concentric brace, eccentric brace and knee brace. Concentric brace enables to offer greater stiffness, for providing direct load transfer. Eccentric brace and knee brace belong to ductile system, maintaining stability by energy consumption braces. Eccentric brace dissipates energy by deforming and buckling, while knee brace disposes energy by form a plastic hinges. Concentric brace is a common way for enhancing lateral stiffness in scaffold. Current studies aimed to investigate detail parameter effects in one brace pattern, while few comparative studies were carried on multiple brace pattern. In this paper, a simplified simulation method was proposed. Throughout simulation analysis, some regulations of brace arrangement were summarized, which provides a guidance during the scaffolding design and optimization process.

A highly flexible and simple non-Markov MC simulation method

A highly flexible and simple non-Markov MC simulation method

A preoperative simulation of medial open-wedge high tibial osteotomy for predicting postoperative realignment.

Three-dimensional preoperative surgical simulation of the medial open-wedge high tibial osteotomy (OWHTO), simplified as the rigid rotation around the hinge axis, has been performed to predict postoperative realignment. However, the practicality of this highly simplified simulation method has not been verified. This study aimed to investigate the validity of realignment simulation simplified as a rotation around a hinge axis compared with a postoperative CT model. A three-dimensional surface model of the tibia and femur was created from preoperative computed tomography (CT) images (preoperative model) of three patients. The simulation of medial OWHTO created sixty computer simulation models in each patient simplified as the rigid rotation of the proximal part of the tibia relative to the distal part from 1° to 20° around three types of hinge axes. The simulation models were compared with the actual postoperative model created from postoperative CT images to assess the reality of the simulation model. The average surface distance between the two models was calculated as an index representing the similarity of the simulation model to the postoperative model. The minimum value of average surface distances between the simulation and postoperative CT models was almost 1mm in each patient. The rotation angles at which the minimum value of average surface distances was represented were almost identical to the actual correction angles. We found that the posterior tibial tilt and the axial rotation of the proximal tibia of the simulation model well represented those of the postoperative CT model, as well as the valgus correction. Therefore, the realignment simulation of medial OWHTO can generate realistic candidates for postoperative realignment that includes the actual postoperative realignment, suggesting the efficacy of the preoperative simulation method.

Use of a Residual Neural Network to Demonstrate Feasibility of Ship Detection Based on Synthetic Aperture Radar Raw Data

Synthetic Aperture Radar (SAR) is a well-established 2D imaging technique employed as a consolidated practice in several oil spill monitoring services. In this scenario, onboard detection undoubtedly represents an interesting solution to reduce the latency of these services, also enabling transmission to the ground segment of alert signals with a notable reduction in the required downlink bandwidth. However, the reduced computational capabilities available onboard require alternative approaches with respect to the standard processing flows. In this work, we propose a feasibility study of oil spill detection applied directly to raw data, which is a solution not sufficiently addressed in the literature that has the advantage of not requiring the execution of the focusing step. The study is concentrated only on the accuracy of detection, while computational cost analysis is not within the scope of this work. More specifically, we propose a complete framework based on the use of a Residual Neural Network (ResNet), including a simple and automatic simulation method for generating the training data set. The final tests with ERS real data demonstrate the feasibility of the proposed approach showing that the trained ResNet correctly detects ships with a Signal-to-Clutter Ratio (SCR) > 10.3 dB.

Research on simplified tire finite element modeling and simulation method

A simplified tire finite element model modeling and simulation method with high efficiency and accuracy is proposed to address the issues of poor efficiency and low accuracy in tire finite element simulation. Firstly, the detailed finite element model of the tire is established, and the viscoelastic material parameters are determined through theoretical analysis and simulation verification. Then, the Hyperelastic material parameters are obtained through cyclic Tensile testing, and finally, the static tire condition test verification is completed. Based on the established detailed finite element model of the tire, the influence of different rubber materials on the dynamic characteristics of the tire is studied. On this basis, simplified friction and structure models are proposed to complete the establishment of a simplified tire finite element model. The simulation results of lateral and longitudinal slip conditions are compared with experimental data by implanting a finite element friction model that considers slip velocity and contact pressure. Through simulation analysis, it was found that the tread compound has a significant impact on the dynamic characteristics of the tire, while other compounds have a relatively small impact. Simplifying the tire finite element model can significantly improve the efficiency of finite element simulation and reduce convergence issues. The comparison accuracy between the finite element model simulation results and experimental data is relatively high, with the average accuracy of longitudinal force, lateral force, and correction moment reaching 89%, 95%, and 81%, respectively. This verifies the correctness and effectiveness of the simplified tire finite element model modeling and simulation method. This method provides certain reference significance for improving the efficiency of tire finite element simulation and providing virtual matching between tires and the entire vehicle.

Full-scale experimental study on precast bridge column with grouted sleeve connections and large-diameter reinforcing bars

In this study, a full-scale bridge column with grouted sleeve (GS) connections and large-diameter (40 mm) reinforcing bars was investigated experimentally and numerically with comparison to a reference cast-in-place (CIP) column. Finite element models were established at the OpenSeesPy platform and validated against experimental results. Consequently, empirical equations are developed to predict effective rotational stiffness, post-yield stiffness ratio, ultimate moment, and ultimate rotation of joint sections. And the predicted parameters by empirical equations are compared with the calibrated parameters from the numerical analysis results. Finally, a simplified bilinear rotational spring was proposed to simulate strain penetration in GS and CIP columns. The availability of the simplified simulation method of strain penetration effects was confirmed with the numerical simulation results of full-scale tests. Results indicate that the failure mode, crack pattern, deformation, and resistance mechanism of the GS column are different from that of the CIP column. The first yield and maximum lateral load of the GS column are 6%, 5% larger than the CIP column, and the ultimate lateral displacement of the GS column is 96% of the CIP column. The numerical models generally matched well with the load–displacement curves and joint opening of tested columns. The simplified bilinear rotational spring with predicted parameters is effective in simulating strain penetration in GS and CIP columns.

Borehole Group Effect during Pile Foundation Construction in Soft Soil Areas

Existing projects indicate that a large number of pile boreholes formed via cement fly ash gravel (CFG) pile construction in soft soil could produce a borehole group effect in the absence of timely backfilling. The borehole group effect could cause ground settlement and threaten the safety of adjacent buildings, tunnels, and pipelines. However, the mechanism of the borehole group effect, causing serious deformation in surrounding soil, has seldom been studied, and there exists no simple simulation method to predict the borehole group effect. In this study, a case involving CFG pile boreholes in a soft soil area causing a significant settlement of surrounding buildings was introduced. Based on this case, a centrifuge test was designed to simulate the influence of a single borehole and multiple boreholes on the surrounding soft soil. The mechanism of the borehole group effect was investigated via centrifuge tests and the finite-element method. In the case of a single borehole, a horizontal circumferential stress arch and vertical stress transfer arch were formed in the soil, which effectively limited the shrinking deformation of the borehole wall. In the case of a large number of boreholes with a small spacing, the horizontal and vertical stress arches around the boreholes affected and weakened each other. As a result, the shrinking deformation of the borehole group was greater than that of the single borehole. In other words, the borehole group effect was found to cause serious deformation in the surrounding soil. To overcome the difficulty in the simulation of a large number of pile boreholes in engineering, the borehole-type conversion and multihole merging method was proposed. The simulation results indicated that the simplified method was reasonable.

Numerical investigation of structural optimization and defect suppression for high-performance perovskite solar cells via SCAPS-1D

This work proposes a simple simulation method for the optimization of n-i-p perovskite solar cell (PSCs) via SCAPS-1D and aims to achieve high-performance devices. Nowadays, the carrier recombination induced by heavy defects in bulk and interfaces is one of the main obstacles which restricts PSC efficiency and is also harmful to device stability. Here we modify the MAPbI3 device through a series of structural and basic optimizations, including the thickness of each layer, carrier diffusion length, interface recombination, doping concentration and overall series resistance. Through the modified simulation, a high-performance MAPbI3 device with suppressed recombination and optimized structure is realized, resulting in an encouraging power conversion efficiency of 20.09%, an enhanced V oc of 1.087 V, J sc of 22.56 mA cm−2 and an FF of 78.5%. These findings unveil the critical effect of defect suppression on PSCs and offer a simple method to achieve high-performance devices.

An algorithm to determine the most suitable location to construct new commercial harbours

In the planning of a new harbour, much attention should be given to minimising the transportation time and cost during the lifetime of the harbour. An algorithm is proposed for determining the most suitable location for constructing new commercial harbours and ports. To determine the most suitable location for new harbours locally, a simplified simulation method is prepared for computing the characteristics of sea waves. In the proposed global model, the distribution of population, the transportation cost, the capacities of existing harbours and the demands for export/import cargos are employed as the main factors. In this model, an index called the total transportation price index (TTPI) is introduced. TTPI is calculated and examined for any potential location where the new harbour or port might be constructed. The proposed model has been validated by applying it to a case study for the conditions of several big commercial harbours of Iran’s Persian Gulf coastline. The case study indicates that the position of the port of Imam Khomeini is the most technically suitable; and that the Chahbahar port has the worst location for serving the entire country and should be limited to serving locally the nearby provinces.