Practical Simulation Method Research Articles

Numerical simulation study of fracture propagation by internal plugging hydraulic fracturing

Internal temporary plugging fracturing technology improves the stimulated volume by forming a more complex fracture network, significantly enhancing the reservoir stimulation effect and effectively developing unconventional oil and gas resources. However, the current understanding of the fracture propagation mechanism on internal temporary plugging fracturing is still unclear, making it difficult to determine the main controlling factors that affect the shape of the fractures. In addition, the lack of practical numerical simulation methods for temporary plugging fracturing makes it challenging to provide guidance for field scheme design. Utilizing the finite element cohesive zone method, which incorporates globally embedded cohesive elements, this study constructs a comprehensive numerical model to investigate the propagation behavior of temporarily plugging fracturing fractures. The model delves into the impact of various geological and construction parameters on the opening conditions of branch fractures during the temporary plugging fracturing process, as well as the propagation patterns of fractures within naturally fractured reservoirs. The research findings indicate that the construction factors have the following impacts: When the pumping rate and viscosity of the fracturing fluid are comparatively high, the resulting fluid pressure within the fracture escalates, resulting in the creation of numerous branch fractures within the naturally fractured reservoir. This, in turn, augments the fracture’s complexity. However, these two factors have little influence on the maximum deflection distance of the deflected fracture. As for the geological factors, an increase in the horizontal stress difference will decrease the maximum deflection distance of the deflected fracture, reducing the number of natural fractures intersected and shortening the length of the deflected fracture. Conversely, an increase in the approach angle will increase the maximum deflection distance of the deflected fracture, thereby expanding the affected area. Additionally, the influence of Young’s modulus and Poisson’s ratio on fracture propagation is very slight. A decrease in the tensile strength of natural fractures leads to more natural fractures being intersected during the process, resulting in increasing the length of the fracture and an improvement in the complexity of the fracture grid.

A hydrodynamic approach to reproduce multiple spinning vortices in horizontally rotating three-dimensional liquid helium-4

This paper reports a three-dimensional (3D) simulation of a rotating liquid helium-4, using a two-fluid model with spin-angular momentum conservation. Our model was derived from the particle approximation of an inviscid fluid with residual viscosity. Despite the fully classical mechanical picture, the resulting system equations were consistent with those of the conventional two-fluid model. We consider bulk liquid helium-4 to be an inviscid fluid, assuming that the viscous fluid component remains at finite temperatures. As the temperature decreased, the amount of the viscous fluid component decreased, ultimately becoming a fully inviscid fluid at absolute zero. Weak compressibility is assumed to express the volume change because some helium atoms do not render fluid owing to Bose–Einstein condensations or change states because of local thermal excitation. One can solve the governing equations for an incompressible fluid using explicit smoothed-particle hydrodynamics, simultaneously reproducing density fluctuations and describing the fluid in a many-particle system. We assume the following fluid–particle duality: a hydrodynamic interfacial tension between the inviscid and viscous components or a local interaction force between two types of fluid particles. The former can be induced in the horizontal direction when non-negligible non-uniformity of the particles occurs during forced two-dimensional rotation, and the latter is non-negligible when the former is negligible. We performed a large-scale simulation of 3D liquid helium forced to rotate horizontally using 32 graphics processing units. Compared with the low-resolution calculation using 2.4 × 106 particles, the high-resolution calculation using 19.6 × 106 particles showed spinning vortices close to those of the theoretical solution. We obtained a promising venue to establish a practical simulation method for bulk liquid helium-4.

An alternative approach for determining the effective atomic number of some compounds: Monte Carlo study

Researchers have been searching for different methods to determine the effective atomic number of materials for many years. Therefore, there are many methods in the literature to determine the effective atomic number theoretically or experimentally. While theoretical methods neglect some parameters, such as the momentum transfer parameter, photon energy, or scattering angle, experimental methods have incommodious processes. The main goal of this study is to provide a practical simulation method that is both as realistic as experimental results and as easy as theoretical methods. The method considers all these parameters compared to other theoretical methods and transfers them to the virtual environment. In this study, Rayleigh and Compton scattering peaks of 60 pure elements (in the range 20< Z <80) were determined. Rayleigh and Compton peak ratios were correlated with their atomic numbers. The proposed method is available for any energy or scattering angle. Six different compounds (WC, W65Cu35, SnAg, Fe54Co17Ni29, Pd94Cr6, Cu60Zn40) were selected from different atomic number regions (such as low, medium, and high regions). It is important to note that any material (compound or mixture) could be selected. Validation of the method has been performed via different methods commonly used in the literature. It is observed that the results of this method are in good agreement with other methods in the literature. We are expecting that the proposed method will provide great convenience and guidance to researchers in this area.

Validation of maneuvering simulations for a KCS at different forward speeds using the 4-DOF MMG method

Ships with a high center of gravity and at relatively fast speed, such as container vessels, may experience significant heel during turning at a rudder angle of 35°. Accurate prediction of the maneuvering motion of such ships requires consideration of roll motion in addition to surge, sway, and yaw motions. This study applies the 4-Degrees of Freedom (4-DOF) Maneuvering Modeling Group (MMG) method, developed by one of the authors, as a practical simulation method that includes the roll-coupling effect, to predict the maneuvering of a Kriso Container Ship (KCS). To validate the accuracy of the maneuvering simulations, the results are compared with those obtained from free-running model tests for turning and zig-zag maneuvers. Furthermore, to capture the effect of speed on maneuvering, the free-running tests are conducted by varying the approach speed of the ship model. The test results reveal that the advance in turning and the overshoot angle in zig-zag maneuvers increase with speed, while the tactical diameter decreases. The simulation results obtained using the 4-DOF MMG method are consistent with the free-running test results with practical accuracy. Therefore, the 4-DOF MMG method proves useful in predicting the maneuvering of ships, such as container ships, at fast speeds.

A Hybrid Volume-Surface Integral Equation Method for Rapid Electromagnetic Simulations in MRI.

We developed a hybrid volume surface integral equation (VSIE) method based on domain decomposition to perform fast and accurate magnetic resonance imaging (MRI) simulations that include both remote and local conductive elements. We separated the conductive surfaces present in MRI setups into two domains and optimized electromagnetic (EM) modeling for each case. Specifically, interactions between the body and EM waves originating from local radiofrequency (RF) coils were modeled with the precorrected fast Fourier transform, whereas the interactions with remote conductive surfaces (RF shield, scanner bore) were modeled with a novel cross tensor train-based algorithm. We compared the hybrid-VSIE with other VSIE methods for realistic MRI simulation setups. The hybrid-VSIE was the only practical method for simulation using 1 mm voxel isotropic resolution (VIR). For 2 mm VIR, our method could be solved at least 23 times faster and required 760 times lower memory than traditional VSIE methods. The hybrid-VSIE demonstrated a marked improvement in terms of convergence times of the numerical EM simulation compared to traditional approaches in multiple realistic MRI scenarios. The efficiency of the novel hybrid-VSIE method could enable rapid simulations of complex and comprehensive MRI setups.

Safety Length Simulation of Natural Gas Pipeline Subjected to Transverse Landslide

The safety of natural gas pipeline is often severely threatened by the transverse landslide. At home and abroad, it is the first time to study the safe length of the pipeline when affected by landslide, and take the safe length of the pipeline as an engineering practical index. Therefore, it is of great significance to study the influence of transverse landslide affecting the safety of natural gas pipeline when a certain length of pipeline is thrusted, and to establish practical index and simulation method for prediction and prevention of the landslide hazards to gas pipeline. Based on the current research results, this study could be divided into three steps: First of all, with the help of ANSYS finite element software, the model of transverse landslide acting on the gas pipeline can be set up, then the length value of gas pipeline safely withstanding transverse landslide can be calculated; Secondly, using the strength reduction method, which is commonly used in the research of landslide stability, can establish three-dimensional model of the landslide and pipes in the ABAQUS finite element software, next, under the same landslide pushed length, the calculation results will be obtained; Finally, to draw reliable conclusions, all calculated results of the former two methods will be linked to synthetically and comparatively analyze, then the length value of common X80 gas pipeline safely bearing transverse landslide can be got. All results can provide some references for engineering and design.

Robust Method for Reservoir Simulation History Matching Using Bayesian Inversion and Long-Short-Term Memory Network-Based Proxy

Summary History matching is a critical process used for calibrating simulation models and assessing subsurface uncertainties. This common technique aims to align the reservoir models with the observed data. However, achieving this goal is often challenging due to the nonuniqueness of the solution, underlying subsurface uncertainties, and usually the high computational cost of simulations. The traditional approach is often based on trial and error, which is exhaustive and labor-intensive. Some analytical and numerical proxies combined with Monte Carlo simulations are used to reduce the computational time. However, these approaches suffer from low accuracy and may not fully capture subsurface uncertainties. This study proposes a new robust method using Bayesian Markov chain Monte Carlo (MCMC) to perform assisted history matching under uncertainties. We propose a novel three-step workflow that includes (1) multiresolution low-fidelity models to guarantee high-quality matching; (2) long-short-term memory (LSTM) network as a low-fidelity model to reproduce continuous time response based on the simulation model, combined with Bayesian optimization to obtain the optimum low-fidelity model; and (3) Bayesian MCMC runs to obtain the Bayesian inversion of the uncertainty parameters. We perform sensitivity analysis on the LSTM’s architecture, hyperparameters, training set, number of chains, and chain length to obtain the optimum setup for Bayesian-LSTM history matching. We also compare the performance of predicting the recovery factor (RF) using different surrogate methods, including polynomial chaos expansions (PCE), kriging, and support vector machines for regression (SVR). We demonstrate the proposed method using a water flooding problem for the upper Tarbert formation of the 10th SPE comparative model. This study case represents a highly heterogeneous nearshore environment. Results showed that the Bayesian-optimized LSTM has successfully captured the physics in the high-fidelity model. The Bayesian-LSTM MCMC produces an accurate prediction with narrow ranges of uncertainties. The posterior prediction through the high-fidelity model ensures the robustness and accuracy of the workflow. This approach provides an efficient and practical history-matching method for reservoir simulation and subsurface flow modeling with significant uncertainties.

Error correction algorithms in non-null aspheric testing next generation sequencing data

Non-null tests are more versatile than null tests and could give fast, generic tests with sufficient performance. The non-null testing methods are able to measure aspheric surfaces with substantial deviations from a reference sphere. The ray will return along a different path and interfere with a separate reference ray in a non-null arrangement. The retrace error occurs because of the significant disparity between the aspheric and the reference. To correct retracing errors and replicate aspheric fabrication imperfections, complex systems modelling and simulations are required. We propose a ray-tracing-based technique for simulating the non-null interferometer that estimates the optical path differences by tracking lasers across the reference and testing paths. An error correction method is used by ray trace analysis to correct the retracing errors in non-null tests of aspheric surfaces. Experiments were conducted to demonstrate the effectiveness of this strategy. The result of the study shows that the proposed system successfully and effectively rectifies the retracing error compared to other practical findings and computer simulation methods. It is more versatile, faster, and provides adequate aspheric assessment performance.

Experimental and numerical study of water sprayed turbulent combustion: Proposal of a neural network modeling for five-dimensional flamelet approach

Owing to the increasing worldwide demand for natural gas, the development of a large submerged combustion vaporizer is required. Its burner is equipped with a water spray nozzle to reduce nitrogen oxides, and a practical simulation method is required for the optimal design. The non-adiabatic flamelet approach can predict the combustion emissions and is useful for reducing simulation costs. However, as the number of control variables increases, the database requires larger memory and cannot be dealt with by general computers. In this study, an artificial neural network (ANN) model based on a five-dimensional flamelet database, which includes the effects of heat loss and vapor concentration by sprayed water evaporation, is developed. Furthermore, large eddy simulations (LESs) for turbulent combustion fields with and without water spray are conducted employing flamelet generated manifold (FGM) approach with this ANN model, and the validity is investigated. For comparison, a lab-scale burner equipped with a water spray nozzle is manufactured, and combustion experiments with and without water spray are conducted. The results show that CO, NO, temperature, and reaction rate of progress variable predicted by the present ANN model are in good agreement with those of a five-dimensional flamelet database. In the condition without water spray, the flame behavior predicted by the LES employing the FGM/ANN approach is in good agreement with that employing the conventional FGM approach, while indicating much lower memory, although there appeared some quantitative discrepancies in the temperature against the experiment probably partially because of the insufficiency of the FGM approach for the present complex flame structure. In the condition with water spray, the LES employing the FGM/ANN approach is able to capture the effect of the water spray on the flame behavior in the experiment, such that the water spray decreases the temperature, which causes the decrease in NO but increase in CO.

Field-Circuit Co-Simulation Method for Electrostatic Discharge Investigation in Electronic Products

Electrostatic discharge (ESD) plays an important role in the hard or soft failure of electronic products due to its high voltage, strong electric field, instantaneous high current, and a wide spectrum electromagnetic radiation. A field-circuit co-simulation method combining circuit elements and full-wave 3D model is applied to investigate ESD effects on a system including ESD generator, electronic device and IC chips on PCB, which can obtain both the electromagnetic field and the voltage/current information. The signal transmitting can be monitored under ESD-event when different discharge voltage polarity and protective enclosures are applied. Moreover, transient voltage suppressors can be appended to the field-circuit co-simulation model and their effects to ESD protection are investigated. The research on the field-circuit co-simulation of electronic products puts forward a more practical simulation method for electrostatic discharge.

Practical simulation method for determination of effective atomic number from Rayleigh to Compton scattering ratio by MCNP

Monte Carlo simulation of the Rayleigh/Compton scattering method for effective atomic number determination with MCNP (version 6.2) was proposed. As known, effective atomic numbers can be used for evaluating shielding behavior, in non-destructive analysis and medical imaging, especially for binary compounds with high precision. Various methods for the determination of effective atomic number are present in the literature, and they depend on different mathematical manipulations. For the first time, a simulation method was developed for the determination of effective atomic numbers of some compounds. Rayleigh to Compton scattering intensity ratios (R/C) of seven different pure elements (from Indium to Gadolinium) were determined with simulations. A straight line equation is fitted using R/C scattering intensity ratios of these seven elements. R/C values of five different compounds were also simulated. Thus, effective atomic numbers of these compounds were determined using the equation. The results of the simulation were compared with available experimental and theoretical results. The studied simulation method showed acceptable agreement with ZXCOM calculation results and acceptable results with the experimental study. This method is suitable to be used for almost every material type and quite insensitive to experimental details, such as material phase, thickness, etc. The simulation results are really encouraging and can be used to guide various experiments.

Application of Gauss principle of least constraint in multibody systems with redundant constraints

Redundancy in the constrained mechanical systems often occurs in complex multibody mechanic systems in the existence of excessive constraints and singular positions due to system motion. In this work, Gauss principle of least constraint (GPLC) is applied to solve the dynamic motion of system with redundant constraints without changing the physics of system. Furthermore, the particle swarm optimization method is used to handle the minimization optimization problem. Eventually, the effectiveness of GPLC is validated through the dynamic modelling and simulation of two numerical examples (a planar four-bar mechanism and a spatial parallelogram mechanism). The simulation results are analyzed and compared with those obtained from Udwaia-Phohomsiri formulation and augmented Lagrangian formulation, in terms of constraint violation, computational efficiency and variation of the mechanical energy. From the viewpoint of computational efficiency and accuracy, GPLC can be regarded as a practical real-time simulation method for multibody systems with redundant constraints.

Notice of Removal: Practical Simulation Method on Multimode-No-Core-Multimode Fiber Structure Based on the Mode Expansion

In this paper, a simplified simulation method for multimode-no-core-multimode (MNM) fiber structures is developed and demonstrated. The method is based on the mode expansion in the vectorial form, taking account of a complete set of guided modes. The simulated results are in good agreement with the experimental results. Also, it is shown that mode distribution of an input multimode fiber (MMF) is an influence on multimode interference(MMI) in the MNM fiber structure and can be controlled by using a single mode fiber(SMF) segment coupled to it. The proposed method provides an effective way for the designs of multimode-interference(MMI)-based fiber devices, which particularly contain a lot of modes.

Traffic-Aware Multiple Association in Ultradense Networks: A State-Based Potential Game

In the fifth-generation (5G) mobile communication system, base stations become denser, and user equipment becomes more powerful. Multiple-association technique promises diversity gains for 5G. However, existing multiple-association schemes are centralized, which have high signal overhead and depend on the reference signal receiving power, and cannot adapt to the fluctuating traffic of users. Therefore, it calls for a new distributed multiple-association scheme. We model the multiple-association problem as a state-based potential game (SPG). With the aid of SPG, the association policy that we designed could drive the ultradense networks to evolve toward the global optimization in the flow level performance. Finally, the performance of our proposed traffic-aware multiple association (TAMA) algorithm is investigated through a practical and discrete simulation method.

The Effect of ADRC on Vehicle Braking Performance

The active disturbance rejection control (ADRC) was proposed as a control strategy for anti-lock braking system (ABS) to improve the braking performance. A real-time simulation model was developed after analyzing the brake force during vehicle braking and the ADRC principle. This experimental real-time simulation platform was developed based on xPC Target. This ABS study was conducted on a dry concrete pavement, and the braking performance indices were analyzed under the ADRC and the bang–bang control. The results suggest that the braking performance is more superior with ADRC than the bang–bang control because the braking time and braking distance were reduced. The xPC Target is a less-costly and practical method for real-time simulation.

Physically based constitutive modeling of concrete fatigue and practical numerical method for cyclic loading simulation

Fatigue failure is usually modelled by estimating fatigue lifetime with corresponding S-N curve and fatigue damage accumulation law such as Miner's law. This approach can neither track the stress redistribution induced by fatigue damage nor explain the mechanism of fatigue damage evolution properly. In this paper, a constitutive model for concrete fatigue is developed within the framework of continuum damage mechanics, where fatigue damage can capture the gradual degradation of mechanical performance in concrete. The conventional phenomenologically modelled fatigue damage evolution is built with an explanation on its physical mechanism. Then, in order to increase computational efficiency instead of taking cycle-by-cycle approach to track fatigue damage evolution in FEM simulation, an accelerating numerical scheme based on two temporal scales homogenization is employed to make computational cost acceptable. The simulation results are compared with fatigue experimental results to validate the proposed constitutive model and accelerating numerical scheme.

Practical maneuvering simulation method of ships considering the roll-coupling effect

In this study, a practical maneuvering simulation method is presented considering the roll-coupling effect by extending an ordinal simulation model (3D-MMG model) proposed by Yasukawa and Yoshimura (J Mar Sci Technol 20:37–52, 2015), and adding the motion equation of roll. The roll moment acting on the hull is estimated by multiplying the hull lateral force with the vertical acting point. With respect to the surge force, lateral force, and yaw moment, the derivative expression model is employed. Subsequently, hydrodynamic derivatives with the exception of the roll-related terms are obtained by a captive model test based on the 3D-MMG model. The roll-related derivatives and the vertical acting point of the hull lateral force are estimated by simple formulae constructed based on the experimental data of four ship models. To validate the proposed simulation method, turning simulations are conducted for a pure car carrier model with variations in the metacentric height $${\overline{\mathrm{GM}}}$$ and are compared with free-running model test results. The simulation method exhibits sufficient accuracy with respect to its practical use and is useful to conventionally predict turning motions by considering the roll-coupling effect.

Investigating the relationship between physical characteristics of watersheds and nonlinearity of daily streamflow processes

Using time series models is one of the practical methods for simulation and prediction of hydrological data. But often, without examining linear or nonlinear system, common linear time-series models are used. And it is expected that streamflow nonlinearity is heavily influenced by physiographic characteristics of the watershed. In this study, using BDS test, nonlinearity of daily streamflow was examined, then its relationship with the watershed slope and area of hydrometric stations was examined. ADF test was used to test stationarity of data time series. The results of ADF test revealed that with the elimination of non-stationarity factors, streams' flow series become stationary. Also, BDS test results showed that flow was nonlinear. In examining the relationship between streamflow nonlinearity and watershed area, the results revealed that despite R2 = 0.91, nonlinearity of flow was in the significant relationship with the third power area. Regarding the relationship between streamflow nonlinearity and watershed slope, no significant relationship was found. It should be noted that the relationship between these two parameters and the intensity of nonlinearity is the novelty of this article.

Investigating the relationship between physical characteristics of watersheds and nonlinearity of daily streamflow processes

Using time series models is one of the practical methods for simulation and prediction of hydrological data. But often, without examining linear or nonlinear system, common linear time-series models are used. And it is expected that streamflow nonlinearity is heavily influenced by physiographic characteristics of the watershed. In this study, using BDS test, nonlinearity of daily streamflow was examined, then its relationship with the watershed slope and area of hydrometric stations was examined. ADF test was used to test stationarity of data time series. The results of ADF test revealed that with the elimination of non-stationarity factors, streams' flow series become stationary. Also, BDS test results showed that flow was nonlinear. In examining the relationship between streamflow nonlinearity and watershed area, the results revealed that despite R2 = 0.91, nonlinearity of flow was in the significant relationship with the third power area. Regarding the relationship between streamflow nonlinearity and watershed slope, no significant relationship was found. It should be noted that the relationship between these two parameters and the intensity of nonlinearity is the novelty of this article.

Practical Simulation Method of Digital Relay at C Source Code Level Based on PSCAD/EMTDC

C source codes can be embedded into custom simulation models in PSCAD. Choosing this interface technology can realize closed-loop simulation at source code level for digital relays. The paper improves both calling interface and data interface, which are two keys of interface technology. The calling interface is implemented by calling a FORTRAN function in the script of custom modules. It makes debugging C source codes much simpler. The data interface is implemented directly by the input and output ports of custom modules, which avoids the use of complex public arrays. The proposed method is especially suitable for the transition stage from principle study to device development. An actual distance relay module written in C language is taken for an instance. The test case shows that the method can be used to verify C source codes in an actual relay flexibly and simply. Developers can validate the source codes independent of a physical device, which will enhance the efficiency greatly.