Parallel Numerical Simulations Research Articles

Parallel numerical simulation of the 2D acoustic wave equation

Parallel numerical simulation of the 2D acoustic wave equation

Large scale massively parallel numerical simulation for blast effects on structures

An efficient large-scale parallel computing program for blast effects on structures is developed based on software platform mode, which adopts component-based three-layer software architecture to achieve disciplinary hierarchy. The parallel layer encapsulates high-performance data structures and shields large-scale parallel computing technology, enabling efficient mesh adaptivity. The common numerical algorithm layer encapsulates fluid, structural, and coupling algorithm processes providing standardized interfaces for extending numerical schemes. The physical model layer provides extension interfaces for state equations, source terms, initial boundary values, etc, to facilitate quick customization of large-scale parallel software for blast effects on structures. Typical examples verify the correctness, effectiveness and high precision of the proposed program in fluid-structure coupling problems. The parallel efficiency of 300,000 processor cores with hundreds of millions of grids reach 60.84% for the shock wave transmission. Finally, the dynamic behavior of multi-storey buildings under blast waves is simulated to reveal the damage model of the overall collapse. These results show that the software has a broad application prospect in the field of explosion. The results suggest that the software holds significant potential for application in the field of explosion, particularly in intricate and large-scale scenarios.

Development and deployment of data-driven turbulence model for three-dimensional complex configurations

Abstract In recent years, the synergy between artificial intelligence and turbulence big data has given rise to a new data-driven paradigm in turbulence research. Data-driven turbulence modeling has emerged as one of the forefront directions in fluid mechanics. Most existing studies focus on feature construction, selection, and the development of modeling frameworks, often overlooking the practical deployment and application of trained models. This paper examines the entire process from model construction to real-world deployment, using data-driven turbulence modeling for high Reynolds number flows over complex three-dimensional configurations as a case study. Key stages include data generation, input-output feature construction, model training, model compilation and optimization, deployment, and validation. We successfully implemented the entire workflow in a heterogeneous supercomputing environment and, through mixed programming techniques, integrated the resulting turbulence model into the Platform for Hybrid Engineering Simulation of Flows (PHengLEI) open-source software framework. This allowed for mixed-precision simulations, with the main equations solved in double precision and the turbulence model in half precision. The new computational framework was validated through large-scale parallel numerical simulations on grids with tens of millions of elements for three-dimensional complex configurations. The results highlight the efficiency of our model deployment, with overall computational efficiency improving by 13.35% and the turbulence model’s solution speed increasing by approximately 3.9 times. The accuracy of the computations was also confirmed, with the average relative error in the lift and drag coefficients calculated by the data-driven turbulence model within 3%. Across various computing nodes, the relative error in the computed aerodynamic coefficients remained within 1%, demonstrating the framework’s scalability. Notably, our contributions have been incorporated as a case study in the latest PHengLEI open-source project5 5 https://forge.osredm.com/PHengLEI/PHengLEI-TestCases/tree/master/Y02_ThreeD_M6_Unstruct_Branch_Ascend. .

Axial compression behaviour of square concrete-filled stainless-clad bimetallic steel tubular stub columns

Concrete-filled stainless-clad bimetallic steel tube (CFSCBST) members combines the advantages of excellent corrosion-resistance and good economy compared with conventional concrete-filled steel tube (CFST) members, which has great prospects in engineering application. This paper presents a comprehensive experimental and numerical investigation into the axial compression behaviour of CFSCBST stub columns with square sections. A total of eight specimens was conducted on CFSCBST specimens, incorporating varying width-to-thickness ratios, clad ratios and steel strengths, The experimental investigation provided a detailed report on failure modes, load versus displacement and strain response. The experimental results were utilized in a parallel numerical simulation to validate the finite element (FE) model. Subsequently, an extended parametric analysis was conducted to investigate the influence of the strength of the concrete, the substrate steel grade, the clad ratio, and the width-to-thickness ratio were carried out. The data obtained from tests and numerical studies were used to evaluate the applicability of existing design codes AISC/ANSI 360-22, EN 1994–1-1, GB 50936–2014 and DBJ/T 13-51-2020 for predicting the compressive capacity of square CFSCBST stub columns. Overall, a modified design method was proposed, adapted from DBJ/T 13-51-2020, was proposed for CFSCBST stub columns, demonstrating enhanced accuracy in predictions.

Measurement and Simulation of the Propagation of Impulsive Acoustic Emission Sources in Pipes

Abstract: Acoustic Emission (AE) testing is a non-destructive evaluation technique that has gained significant attention in pipeline monitoring. Pencil-lead breaks (PLBs) are commonly used in reproducing and characterising sensors used in AE applications and have emerged as a valuable tool for calibration processes. This technique involves breaking a pencil lead by pressing it on the surface of the test structure and applying a bending moment at a given angle on a surface. The applied force produces a local deformation on the test surface, which is released when the lead breaks. The fracture in these PLBs is assumed to be a step unload; however, this is not the case. In this work, a series of PLB source experiments complemented with parallel numerical simulations were carried out to investigate the actual unload rate by correlating the relationship between AE speed, frequency, and power from PLBs. This was achieved by varying the simulation unload rates recorded over a duration of 2 s on a steel pipe and comparing to the experiment. Analysis of the investigated results from the experimental and numerical models suggests that although the AE line structure of a PLB can be reproduced by simulation for short times only (1 µs), the actual unload rate for PLBs is in the region of 10–8 s. It is concluded that FEA has the potential to help in the recovery of the temporal structure from real AE structures. The establishment of this model will provide a theoretical basis for future studies on the monitoring of non-impulsive AE sources such as impact on pipelines using finite element analysis.

Research on the Noise Suppression of The TEM Signal by Neural Network

The Groud-source Airborne Time-domain Electromagnetic(GATEM) system is susceptible to interference during flight, including motion noise (caused by factors such as wind direction, cable vibrations, and sensor attitude), power frequency noise, and atmospheric noise. To obtain field data, and enhance the precision of abnormal target identification, it is necessary to suppress noise to the field data. In this paper, a neural network approach is employed to reconstruct the GATEM signals. This includes the establishment of a sample sets, parallel numerical simulation method of GATEM responses based on the OpenMP, deployment and execution of parallel computing programs on cloud computing platforms, and neural networks implementation for noise suppression in noisy GATEM signals. When the signal-to-noise ratio is above 30dB, the error between the denoised signal and the original signal is very small, with an average relative error not exceeding 1%. This method can effectively improve the accuracy of interpretation and imaging of GATEM signals, opening up new research directions in noise suppression for electromagnetic signals.

Stability analysis of a deep and large open pit based on fine geological modeling and large-scale parallel computing: a case study of Fushun West Open-pit Mine

Accurate input of geological elements is essential for evaluating or predicting natural hazards such as subsidence, landslides, and earthquakes. This paper proposes an approach to carry out an open pit’s overall and whole-process mechanical analysis with complex geological conditions, using precise modeling and large-scale parallel calculation techniques. Taking the Fushun West Open-pit Mine (the largest open-pit coal mine in Asia) as an example, through the elaborate multi-method geological investigation, the interfaces of interbedded shales and mudstones, the unloading zones, and the small structures were identified, a detailed 3D geological model was built and finely meshed in full-size with 100 million degrees of freedom, large-scale parallel numerical simulation was then performed, the results agree well with the InSAR monitoring data and in situ observations. Besides, the simulation can replicate the landslides in recent years. Through the simulation, it is possible to locate the potential landslide area, and targeted backfilling schemes for stability treatment were put forward and further simulated. The results indicate that the proposed approach can more effectively and reliably evaluate the Fushun West Open-pit Mine’s overall slope stability and closure plan.

Detailed Performance Studies on a Small Electric-Powered Contra-Rotating Ducted Fan Engine

Electrical propulsion has been identified as one of the key fields of future research within the aerospace sector. This paper aims to contribute to the ongoing development of small electric-powered ducted fan engines with a thrust in the range of a few hundred newtons. A special emphasis is placed on introducing contra-rotating fans to such engines. Recently, such an innovative contra-rotating engine has been developed and put into operation on a novel test bench. This study intends to take a closer look at the performance of the engine at design speed ratio by means of experimental and numerical investigations. Global performance parameters are analyzed to validate parallel numerical simulations. Results indicate that both experiment and simulation are in good agreement. Moreover, detailed flow studies of the spanwise distribution of relevant parameters are conducted, and results are discussed. From these results, the stall behavior of the stage is identified. Finally, a comprehensive performance map is established with the help of a number of numerical simulations, which reveal a good off-design performance behavior of the engine.

Black-box statistical prediction of lossy compression ratios for scientific data

Lossy compressors are increasingly adopted in scientific research, tackling volumes of data from experiments or parallel numerical simulations and facilitating data storage and movement. In contrast with the notion of entropy in lossless compression, no theoretical or data-based quantification of lossy compressibility exists for scientific data. Users rely on trial and error to assess lossy compression performance. As a strong data-driven effort toward quantifying lossy compressibility of scientific datasets, we provide a statistical framework to predict compression ratios of lossy compressors. Our method is a two-step framework where (i) compressor-agnostic predictors are computed and (ii) statistical prediction models relying on these predictors are trained on observed compression ratios. Proposed predictors exploit spatial correlations and notions of entropy and lossyness via the quantized entropy. We study 8+ compressors on 6 scientific datasets and achieve a median percentage prediction error less than 12%, which is substantially smaller than that of other methods while achieving at least a 8.8× speedup for searching for a specific compression ratio and 7.8× speedup for determining the best compressor out of a collection.

JUSMAR-MANS: a platform software for compressible multimedium flow large-scale numerical simulation on JASMIN framework

A new platform software named JUSMAR-MANS based on JASMIN was developed for the massively parallel numerical simulation on compressible multimedia multiphase flow under complex conditions. Different from the traditional “chimney” program research and development (r&d) pattern, the MANS who adopted the “platform” r&d pattern provides a way by which the users can rapidly and conveniently customize personalized high-credibility program of multimedium without considering in numerical discrete and parallel computing. MANS has the following advantages: 1) Decoupling of disciplines: In architecture design, physical modeling, numerical discreting, parallel computing are separated from each other and concept shielding so that the high barriers of program r&d caused by interdisciplinary are broken down. 2) Expandability: enables to easily extend new physical models and numerical schemes based on single point/element interfaces. 3) Rapid customization: enable to quickly assemble personalized program based on various models and algorithms libraries integrated by MANS. Based on MANS, it only takes serial code within a few days to obtain a well-posed large - scale multimedium simulation, which greatly reduce the complexity of software r&d for compressible multimedium flow.

Massively parallel numerical simulation of 3D shock wave propagation based on JASMIN framework

An efficient massively parallel computing program for shock wave propagation named Shock3d is developed for shock wave damage mechanism in complex scenes. With the finite volume method, the program is built upon JASMIN (J parallel Adaptive Structured Mesh applications INfrastructure) and employs a component-based hierarchical organization structure. Using the patch-based core algorithm, Shock3d enables high parallel efficiency and strong parallel scalability with a parallel domain decomposition method and an image domain-based communication mode. It not only considers gravity, real gas effects, and boundaries in complex scenes, but also supports dynamic load balancing (DLB) and three-dimensional structured meshes and allows the parallel solution of hundreds of millions of mesh problems. Typical examples were used to verify the validity, parallelism, and high-resolution simulation results of the program developed. In the scalability test, where the propagation of shock waves through hundreds of millions of mesh elements was simulated on 300,000 CPU cores, the program delivered parallel efficiency of 60.84%.

Simulated climate effect of the Three Gorges Reservoir after its completion:Within surface and local scope instead of regional

针对以往三峡水库气候效应数值模拟研究中,水库参数化方案简约及模拟时段未涉及成库以来高水位运行阶段等不足,在中尺度气象模式中,通过扩宽水体面积和抬升水位高度的方式对三峡水库引起的陆面参数变化进行描述,进而采用敏感性数值试验及统计分析等手段,评估了三峡水库成库以来高温干旱(2013年)和低温洪涝(2020年)年景下,关键气象要素对水库运行的响应特征。结果表明:两种典型年景下水库运行均会造成近地层气温降低(0.98~1.27℃)、相对湿度增加(3.9%~5.5%)和风速增大(0.43~0.68 m/s),同时响应强度的日变化导致近地层气温和相对湿度的日较差减小、平均风速的日较差增大;尽管上述变量的变化幅度与该地区气候的自然变率相当,但水库运行对气温和相对湿度的影响范围基本限制于水库周边约2 km,垂直方向则大多低于200 m,对风速的影响范围可扩展至水库周边约12 km,垂直方向延伸至200 m左右,且响应强度均随水平距离和垂直高度的增加而显著减小。尽管数值试验放大了三峡水库的气候效应,但作为典型的河道型水库,三峡水库成库以来的不同气候年景下,水库运行产生的气候效应基本限制在近地层、局地范围内,未对区域气候产生明显影响。;In view of the shortcomings of the previous numerical simulation research on the climate effect of the Three Gorges Reservoir (TGR), such as the simplicity of the reservoir parameterization and the fact that the simulation period did not involve the reservoir impoundment period, the changes of land surface parameters induced by the TGR were numerically described by increasing the river width and raising the water level in the mesoscale meteorological model. The variation characteristics of meteorological elements after completion of the TGR were analyzed based on two parallel numerical simulations, control run (no TGR) and sensitive run (TGR), during the drought year with high temperature (2013) and the flood year with low temperature (2020). The results show that the operation of TGR under these two typical years both reduce the surface temperature (0.98-1.27℃), increase the relative humidity (3.9%-5.5%) and the wind speed (0.43-0.68 m/s), the diurnal range of near-surface temperature/relative humidity decreases and the diurnal range of wind speed increases with the diurnal variation of the response; Although the aforementioned responses are equivalent to the natural climate variability, the variations of temperature and relative humidity are basically limited to about 2 km around the reservoir, most of which are lower than 200 m in the vertical direction, and the variation of wind speed change extend to about 12 km near the reservoir with up to 200 m in the vertical direction. All of these responses decrease significantly with the increase of horizontal distance and vertical height. Therefore, although the climate effect of the TGR is amplified in our simulation experiment, as a typical river-type reservoir, the climate effect induced by the operation of TGR is basically limited to the surface and local area, and has no obvious influence on the regional climate.

Parallel numerical simulation of weakly range-dependent ocean acoustic waveguides by adiabatic modes based on a spectral method

With the increasing demand for underwater detection, interest in the acoustic field of range-dependent ocean waveguides is also growing. For weakly range-dependent ocean waveguides, adiabatic modes represent a compromise between accuracy and computational cost and occupy an important place in the simulation of numerical sound fields. However, either existing adiabatic-mode programs consider too few layers of media or the root-finder tends to miss roots. In addition, none of the programs can solve the acoustic field excited by a line sound source located anywhere in the plane. In this paper, we first derive an expression for the acoustic field excited by a line source by adiabatic modes and then introduce a high-precision spectral method to solve the local eigenmodes. For the lower boundary condition of the acoustic half-space, we use the eigenvalue transformation technique to transform the transcendental algebra system formed by spectral discretization into a generalized eigenvalue problem. Several representative numerical experiments are designed to verify the accuracy of the algorithm. After analyzing the parallelism, the multiprocess and multithread hybrid strategy is adopted to further accelerate the algorithm in parallel, and parallel numerical simulation is carried out on the Tianhe–2 multicore supercomputer; favorable acceleration is achieved.

Accelerated Parallel Numerical Simulation of Large-Scale Nuclear Reactor Thermal Hydraulic Models by Renumbering Methods

Numerical simulation of thermal hydraulics of nuclear reactors is widely concerned, but large-scale fluid simulation is still prohibited due to the complexity of components and huge computational effort. Some applications of open source CFD programs still have a large gap in terms of comprehensiveness of physical models, computational accuracy and computational efficiency compared with commercial CFD programs. Therefore, it is necessary to improve the computational performance of in-house CFD software (YHACT, the parallel analysis code of thermohydraulices) to obtain the processing capability of large-scale mesh data and better parallel efficiency. In this paper, we will form a unified framework of meshing and mesh renumbering for solving fluid dynamics problems with unstructured meshes. Meanwhile, the effective Greedy, RCM (reverse Cuthill-Mckee), and CQ (cell quotient) grid renumbering algorithms are integrated into YHACT software. An important judgment metric, named median point average distance (MDMP), is applied as the discriminant of sparse matrix quality to select the renumbering methods with better effect for different physical models. Finally, a parallel test of the turbulence model with 39.5 million grid volumes is performed using a pressurized water reactor engineering case component with 3*3 rod bundles. The computational results before and after renumbering are also compared to verify the robustness of the program. Experiments show that the CFD framework integrated in this paper can correctly perform simulations of the thermal engineering hydraulics of large nuclear reactors. The parallel size of the program reaches a maximum of 3072 processes. The renumbering acceleration effect reaches its maximum at a parallel scale of 1536 processes, 56.72%. It provides a basis for our future implementation of open-source CFD software that supports efficient large-scale parallel simulations.

Parallel computing of building fire using a domain decomposition method based on load balancing

Parallel computing can provide a practical way in performing building fire simulation which often contains an immense amount of grids. Four dimensionless indices were presented for the evaluation of the load balance. According to the four indices, an empirical load description function was established based on the orthogonal experimental method. A domain decomposition method based on load balancing (DDMBLB) was then proposed. A preprocessing tool based on the DDMBLB method was developed, which can decompose the domain automatically with load balancing. Parallel numerical simulations based on the DDMBLB method were performed on an express logistics center fire. The comparison of DDMBLB method and the commonly-used Recursive Coordinate Dichotomy (RCB) method was done to analyze the computing time, speedup ratio and parallel efficiency. The DDMBLB method can significantly reduce the fire simulation time compared to the RCB method. It has a better domain decomposition effect than the RCB method with a greater speedup ration and a higher parallel efficiency.

Probabilistic summarization via importance-driven sampling for large-scale patch-based scientific data visualization

Probabilistic summarization is the process of creating compact statistical representations of the original data. It is used for data reduction, and to facilitate efficient post-hoc visualization for large-scale patch-based data generated in parallel numerical simulation. To ensure high reconstruction accuracy, existing methods typically merge and repartition data patches stored across multiple processor cores, which introduces time-consuming processing. Therefore, this paper proposes a novel probabilistic summarization method for large-scale patch-based scientific data. It considers neighborhood statistical properties by importance-driven sampling guided by the information entropy, thus eliminating the requirement of patch merging and repartitioning. In addition, the reconstruction value of a given spatial location is estimated by coupling the statistical representations of each data patch and the sampling results, thereby maintaining high reconstruction accuracy. We demonstrate the effectiveness of our method using five datasets, with a maximum grid size of one billion. The experimental results show that the method presented in this paper reduced the amount of data by about one order of magnitude. Compared with the current state-of-the-art methods, our method had higher reconstruction accuracy and lower computational cost.

Parallel Numerical Simulation of Complex Unsteady Multi-Component Three-Dimensional Flow Field of Nonequilibrium Chemical Reaction

Parallel Numerical Simulation of Complex Unsteady Multi-Component Three-Dimensional Flow Field of Nonequilibrium Chemical Reaction

Experimental and numerical investigation on the ballistic resistance of ZK61m magnesium alloy plates struck by blunt and ogival projectiles

• Ballistic tests on 5 mm thick Zk61m magnesium alloy plates struck by blunt and ogival rigid projectiles were conducted. • Introduced the Lode angle into the JC plasticity model to characterize the stress flow behaviour of the Zk61m magnesium alloy. • The value of incorporating the Lode parameter into the plasticity model and fracture criterion in the ballistic resistance of the magnesium alloy was reflected. • A unique failure pattern was discovered when an ogival projectile was used to impact the target. In the field of ballistics, Johnson-Cook (JC) plasticity and fracture models have provided a good theoretical basis for the prediction of ballistic performance by capturing the essence of ductile metal fracture. Nevertheless, the JC model cannot accurately reproduce the fracture behaviour of some metals. Many Lode parameter-dependent fracture criteria have effectively improved this deficiency, indicating that the fracture loci of these metals are Lode-dependent, even though the flow stress behaviour is stress state dependent, which cannot be well characterized by the JC plasticity model. In this paper, a series of mechanical tests and parallel numerical simulations of ZK61m magnesium alloy were conducted. The results showed that the flow stress behaviour and fracture loci of the alloy were obviously Lode dependent. Therefore, it seems insufficient to evaluate only the necessity of incorporating Lode parameter into a fracture criterion in predicting ballistic performance of ZK61m magnesium alloy, and more investigations on the influence of Lode parameter on the plasticity behaviour of the material should be carried out. In the present work, ballistic tests were conducted on 5 mm thick ZK61m magnesium alloy plates using blunt and ogival nose shaped projectiles with a nominal diameter of 12.68 mm. The targets failed by shear plugging when impacted by blunt-nosed projectiles, but caused a unique failure pattern under the impact of ogival-nosed projectiles. Lode-dependent plasticity model and fracture criterion were adopted. Better prediction accuracy was observed when Lode parameter is considered in both the plasticity model and fracture criterion simultaneously.

Impact of the fracture contact area on macro-dispersion in single rough fractures

In the scientific literature, the study of the impact of the fracture contact area on macro-dispersion in single rough fractures is still an open question. In this work, we study numerically the combined effects of the fracture roughness and the fracture contact area on the non-Fickian transport in single rough fractures. In particular, we quantify the contribution of the fracture contact area on macro-dispersion. These objectives are achieved by estimating the macro-dispersion coefficient from Monte Carlo parallel numerical simulations in pure advection and advection–diffusion cases. When the fractional void S O is equal to 1 (i.e., for σ lnb <0.25), the Monte Carlo simulations show that macro-dispersion results of two contributions, dispersion caused by the heterogeneity of fracture apertures that induces a channelization of flow paths and molecular diffusion, as shown by the analytical solution proposed by Gelhar in 1993. When the fraction void S O is different from 1 (i.e., for σ lnb >0.25), a third mechanism plays in macro-dispersion. The presence of contacts or obstacles causes a disruption of flow paths. This mechanism is identical to that induced by the fracture roughness with a lower amplitude. Its amplitude is the function of the fractional void S O .

Numerical and Experimental Investigation on the Free-surface Flow and Total Resistance of the DTMB Surface Combatant

Starting with the initial design stage, the ship resistance constitutes one of the most important hydrodynamic aspects. In order to generate and optimize the body lines plan, the ship resistance performance must be considered. In this case, both numerical and experimental methods must be applied to obtain the minimum ship resistance controlled by the speed domain. In the last years, numerical studies based on the Computational Fluid Dynamic (CFD) were implemented in the initial ship design stage in order to analyse the free-surface flow and to predict the ship resistance. The numerical optimization process of the hull forms must be validated by means of the experimental model tests in the specific towing tanks. The constant evolution of the numerical and experimental methodologies can be noted. As a consequence, the accuracy level of the ship resistance prediction is increased; though, difficult numerical problems can occur in case of the unconventional hull forms. Taking into account this aspect, a complex numerical and experimental investigation of the ship resistance problem and free-surface topology was performed in the case of the DTMB surface combatant. A parallel numerical simulation was carried out by using the viscous flow solver ISIS–CFD of the software FINETM/Marine provided by NUMECA. The solver is based on the finite volume method to build the spatial discretization of the transport equation to resolve the Reynolds-Averaged Navier Stokes (RANS) equation. Closure to turbulence is achieved by making use of the k-ω SST model, while the free-surface is captured through an air-water interface based on the Volume of Fluid (VOF) method. For the validation purpose, the tank conditions are reintroduced in the numerical model to account for any banking effect, especially for the high speed cases. Experimental model tests were performed in accordance with the ITTC standard procedures, while the extrapolation process to the full-scale was obtained by using an in-house code, based on the ITTC 57 method. The experimental results are compared through with some internationally recognized towing tank experiments that have been performed for a similar ship model, showing a good agreement. Also, the numerical results are validated against the experimental data and showed to be within a satisfactory congruence.