Computation of Lyapunov Characteristic Exponents Using Parallel Computing

The article’s subject is to study and describe the processes in the hydrodynamic coupling during its operation. The hydrodynamic coupling is a type of hydrodynamic transmission that provides a flexible connection between the input and output shafts, in contrast to the mechanical coupling. Currently, the fluid couplings are widely used and the theoretical description of their operation has been given long before. However, in Russia these units are not produced, the theoretical model is very simple while the experimental data are scattered and non-systematized. So the problem is relevant and requires consideration. The research objective is to complement the existing theoretical model for better describing the fluid coupling operation as well as to compare the results, based on its using, with the numerical simulation results. The main part of the article contains these sections. The mathematical model shows: the equations used for theoretical description of the fluid coupling operation, the basic hydrodynamic equations converted to solve the problem in a stationary setting, and the applied turbulence model (k-ω). The author backslides from the standard jet theory in which the calculation is performed at an average trickle in order to take into consideration the non-uniformity of the velocity distribution in the fluid coupling. The article also raised the issue on the applicability of the stationary formulation of the problem for the numerical simulation. The study revealed that the solutions obtained under stationary and non-stationary calculations practically match. The verification was conducted by three points of characteristic of the hydraulic coupling. The article gives the fluid coupling dimensions, represents an image of its threedimensional model and of the computational grid. It also shows some figures to illustrate the processes in a fluid coupling obtained by its numerical modeling. During the study it was found out that the proposed theoretical model allows us to have higher precision and higher quality in representation of fluid coupling characteristics; the article shows the appropriate graphs. Then a disadvantage is a lack of experimental work. Concerning this issue, the author refers to the publications in which the verification of the results of numerical simulation and experimental results has been conducted showing that their coinciding is quite accurate.

In the tide of artificial intelligence evolution, the demand for data computing has exploded, and the von Neumann architecture computer with separate memory and computing units require cumbersome data interaction, which leads to serious degradation in performance and efficiency. Biologically inspired neuromorphic engineering performs digital/analog computations in memory, with massive parallelism and high energy efficiency, making it a promising candidate to get out of the woods. Memristive device‐based artificial synapses and neurons are building blocks to form hardware neural networks for computing acceleration. In addition, it enables the implementation of integrated bionic perception and motion systems to mimic the human peripheral nervous system for information sensing and processing. Herein, the biological basis and inspiration are described first, and the memristive synapses and circuit‐emulation neurons used for neuromorphic engineering are addressed and evaluated as well as the mechanisms. The computational acceleration and bionic perception motion integration of neuromorphic systems are discussed. Finally, the challenges and opportunities for neuromorphic engineering to accelerate computation and enrich biomimetic perception motion functions are prospected, and it is hoped that light is shed on future advances.

In a coal mine in the northern region of Shaanxi Province, China, a facing-mining excavating roadway exists, which is intended to be retained for subsequent working face safety services. This paper investigates the deformation and damage characteristics of the surrounding rock in different stages using FLAC 3D numerical simulation, taking the facing-mining excavating roadway of this coal mine as the research context. At 20 m ahead of the working face, a discontinuous plastic zone appears in the surrounding rock of the roadway, a phenomenon attributed to the varying hardness of the lithologyand termed 'plastic zone jumping.' The numerical simulation results have been were verified using drill hole peeping. Real-time monitoring of the roadway's stability is conducted on-site, showing that the roadway is significantly affected by mining at the 50 m point ahead of the working face. Based on the numerical simulation and on-site monitoring results, the support strength was increased at 50 m from the working face along the roadway, and a new support scheme was adopted. In the lagging section of the roadway, where mining pressure is strongly evident, differentiated reinforcement using anchor rods, anchor ropes, and W steel belts has been employed, resulting in a satisfactory on-site effect.

A steam jet mill (SJM), which employs industrial waste heat steam as a gas source, is a widely utilized apparatus for the pulverization of fly ash. To achieve elevated single-machine grinding capacity, efficiency improvement research based on structural optimization should be conducted. In this study, numerical simulations and industrial experiments are carried out on SJMs equipped with three and six nozzles (hereinafter referred to as N3 and N6, respectively) to study the influence of nozzle quantity on the flow field and grinding efficiency. The numerical simulation results indicate that, under the N3 structure, particles can achieve a higher impact velocity in the comminution area and improve the kinetic energy of a single impact. In the conveying area, the airflow diffusion is better, resulting in an upward flow field that is more uniform. The classification area shows an increase in the uniformity of the flow field and a significant reduction in the local vortex structure, which is beneficial for accurate particle classification. In the interim, industrial experiments demonstrate that the N3 structure can markedly enhance the processing capacity and energy efficiency of the system. The smaller the feed particle size, the more pronounced the efficiency improvement.

Reliable ventilation is the cornerstone of safe production in coal mines, and accurate monitoring of ventilation parameters is the fundamental guarantee of ventilation technology decision‐making. To improve the accuracy of airflow velocity monitoring in coal mine roadways, theoretical analysis, numerical simulation, and field tests were utilized to study the distribution law of airflow velocity in typical roadway sections. First, the calculation model of position of mean airflow velocity line in rectangular and semicircular arch roadway is established based on Boussinesq theory and Pelant turbulence theory. Then, to verify the correctness of the theoretical model, 25 groups of numerical simulation tests were conducted by using COMSOL‐Multiphysics 3.5a software. The errors between theoretical analysis and numerical simulation are all less than 4%. In addition, the numerical results also show that the contour line of airflow velocity in roadway section is consistent with the shape of roadway section, and the isoline of airflow velocity is basically parallel to the roadway wall. In addition, the closer to the roadway wall, the denser the airflow velocity isoline, indicating that the airflow velocity gradient near the wall is larger. And the thickness of the boundary layer decreases with the increase of airflow inlet velocity. Finally, field tests have been conducted in Chongqing Research Institute and Sima Coal Mine to further verify the correctness of the calculation model and numerical simulation results. The measured distribution law of airflow velocity is consistent with the numerical simulation. And the errors between theoretical analysis and field tests are all less than 4%.

Tundishes are refractory vessels that are used to control the flow of molten steel, promote the removal of inclusions, and increase the homogeneity of temperature and composition during continuous casting processes by optimizing their geometric shape. The flow of molten steel in tundishes is a high-temperature process, and the optimization of the tundish structure is carried out by numerical and physical simulations. In numerical simulations, the viscosity of molten steel is generally set to a constant value; however, in industrial scenarios, the molten steel viscosity is variable with temperature. In the present work, the effects of molten steel viscosity varying with temperature on fluid flow, inclusion motion, and temperature distribution in a tundish were investigated by numerical simulations based on the modification of the top heat flux of the tundish, and the results were further verified by an industrial experiment. The removal rate of inclusions obtained from the industrial experiment was 40.40%. In numerical simulations, the inclusion removal rates were 50.85% and 40.67% when the fluid viscosity was constant and variable, respectively. Hence, when the molten steel viscosity was variable, the numerical simulation result was closer to the experimental one. The industrial experiment revealed that the temperature difference between the edge flow and the middle flow on the tundish liquid surface was 0 K. In numerical simulations, when the top heat fluxes of the tundish were 15 000 and 100 W/m2, the temperature differences on the tundish liquid surface were 5.95 and 0.16 K, respectively.

The dynamics of fluid flow at the interface between elastic solids with rough surfaces depends sensitively on the area of real contact, in particular close to the percolation threshold, where an irregular network of narrow flow channels prevails. In this paper, numerical simulation and experimental results for the contact between elastic solids with isotropic and anisotropic surface roughness are compared with the predictions of a theory based on the Persson contact mechanics theory and the Bruggeman effective medium theory. The theory predictions are in good agreement with the experimental and numerical simulation results and the (small) deviation can be understood as a finite-size effect. The fluid squeeze-out at the interface between elastic solids with randomly rough surfaces is studied. We present results for such high contact pressures that the area of real contact percolates, giving rise to sealed-off domains with pressurized fluid at the interface. The theoretical predictions are compared to experimental data for a simple model system (a rubber block squeezed against a flat glass plate), and for prefilled syringes, where the rubber plunger stopper is lubricated by a high-viscosity silicon oil to ensure functionality of the delivery device. For the latter system we compare the breakloose (or static) friction, as a function of the time of stationary contact, to the theory prediction.

The roof water disaster of the coal seam in the western mining area has become a great threat to mine safety production. In order to study the failure evolution characteristics of mining disturbed rock, FLAC3D numerical simulation software was used to study the mining-induced rock “three zones” height of 2410 fully mechanized caving face in the Yuhua Coal Mine. The dynamic changes of stress evolution, fracture distribution, and displacement of strata in the mining field after mining are obtained by simulation analysis. The height of the bending subsidence zone is 446.4 m, the height of the fracture zone is 153.6, and the height of the caving zone is 22 m. Through the comparative analysis of the empirical formula and the numerical simulation results and the field measured “three zones” height values after mining in the mining area, the numerical simulation results are more consistent with the measured values, which indicates that the numerical simulation method of mining rock “three zones” can be used as an effective means for the study of mining rock “three zones” in the working face, and provides the necessary technical support for the safe and efficient mining of fully mechanized caving face in coal mines.

Objective: In this article we proposed a modeling method by building an assembled model to simulate the orthopedic process of minimally invasive surgery for pectus excavatum and got the clinical verification, which aims to provide some references for clinic diagnoses, treatment, and surgery planning.Methods: The anterior chest model of a 15-year-old patient was built based on his CT images; and his finite element model and the Nuss bar were created. Coupling of nodal displacement was used to connect bones with cartilages of the anterior chest. Turning the Nuss bar over is completed by rotating displacement of it. By comparing the numerical simulation outcomes with clinical surgery results, the numerical simulation results were verifiedResults: The orthopedic process of minimally invasive surgery of pectus excavatum was simulated by model construction and numerical analysis. The stress, displacement fields and distribution of the contact pressure between the Nuss bar and costal cartilages were analyzed. The relationship between correcting force and displacement was obtained. Compared with the of clinical results, the numerical simulation results were close to that of the actual clinical surgery in displacement field, and the final contact position of the Nuss bar and the costal cartilages.Conclusion: Compared with the rigid model, the assembled simulation model is in more conformity with the actual clinical practice. The larger curvature results in the maximum equivalent stress, which is the main reason for clinical pain. Soft tissues and muscles should be taken into account in the numerical simulation process.

Friction drilling is a chipless hole‐making process that utilizes a rotating conical drilling tool to penetrate and create a hole and bushing without generating chip. This process is still not widely used even though it has many significant advantages. There are unanswered questions in finite element models to analyze the stress, temperature and large deformation of the workpiece and to predict the drilled hole and formation of bushing. With modern computing technologies the numerical simulation has proven to be an effective tool for this issue. In the present study, a three‐dimensional finite element model (FEM) has been developed to simulate the stress, plastic strain and temperature distribution in friction drilling of aluminum alloy. The friction drilling process was experimentally conducted using a drilling tool without flutes. The numerical results indicated that high stress occurs at the tool contact surface and adjacent region in the primary penetration. It was confirmed that the distribution of stress and temperature demonstrate the phenomenon of friction heat and softens the work‐material in friction drilling. The numerical simulated results have proven that the developed finite element model is effective to predict stress evolutions and thermal histories in friction drilling of non‐ferrous material.

Numerical simulation and parametric analysis of multi-anchor walls using the finite element method

The paper presents the damage results of thick steel plates subjected to local blast loading using experimental and numerical approaches. Three steel plates with a thickness of 17 mm under the local contact explosion of trinitrotoluene (TNT) explosives were tested, and the damaged parts of the steel plates were scanned using a scanning electron microscope (SEM). ANSYS LS-DYNA software was used to simulate the damage results of the steel plate. By analyzing and comparing the experimental results with the numerical simulation results, the influence law of the TNT acting on the steel plate, the damage mode of the steel plate, the reliability verification of the numerical simulation, and the criterion for judging the damage mode of the steel plate were obtained. Results show that the damage mode of the steel plate changes with the changes in the explosive charge. The diameter of the crater on the surface of the steel plate is mainly related to the diameter of the contact surface between the explosive and the steel plate. The fracture mode of the steel plate in the process of generating cracks is a quasi-cleavage fracture, and the process of generating craters and perforations in the steel plate is a ductile fracture. The damage mode of the steel plates can be divided into three types. The numerical simulation results have minor errors and high reliability, and numerical simulation can be used as an auxiliary tool for experiments. A new criterion is proposed to predict the damage mode of the steel plates under contact explosion.

Water flooding is a well-known secondary mechanism for improving oil recovery. Conventional approach to evaluate the performance of a water flooding process (e.g. breakthrough and post breakthrough behavior) is to establish a reliable geological reservoir model, upscale it, and then perform flow simulations. To evaluate the uncertainty in the breakthrough time or post breakthrough behavior, this procedure has to be repeated for many realizations of the geological model, which takes many hours of CPU time. Moreover, during the early stage of reservoir life, when data is scare, breakthrough and post breakthrough time behavior prediction are usually based on analogues or rules of thumb. Alternative statistical approach is to use percolation theory to predict breakthrough and post breakthrough bahavior. The main contribution is to evaluate the applicability of the existing scaling laws of the breakthrough time by the numerical flow simulation results using the Burgan formation dataset of Norouz offshore oilfield in the south of Iran. Moreover, we extend the scaling to the post breakthrough behavior. There is good agreement between the predictions from the percolation based expressions and the numerical simulation results. Moreover, the prediction from the scaling law took a fraction of a second of CPU times (as it only needs some algebraic calculations) compared with many hours required for the conventional numerical simulations.

Bending degradation of thin-walled box beams made of aluminum omega profile and GFRP panel connected by mechanical fasteners

A new three-dimensional chaotic system with fan-shaped Poincare maps is proposed. Based on merely six terms, the system is easy to implement. Its dynamic behaviors, such as equilibrium points, Poincare maps, power spectra, Lyapunov exponent spectra, bifurcation diagrams and forming mechanism, are analyzed theoretically and numerically. Results of theoretical analyses and numerical simulations indicate that the proposed system possesses complex chaotic attractors. Its equilibrium points are unstable, and the system can keep chaotic when its parameters vary in a wide domain. Furthermore, circuit simulations of the system are discussed. The results of numerical simulations and circuit simulations coincide very well. By virtue of its complex dynamic behaviors and wide-range parameters, the system can be adopted in some application fields where wide-range parameters and complex behaviors are usually preferred, such as secure communication, data encryption, information hiding.