Simulation of rock deformation and mechanical characteristics using clump parallel-bond models

To properly simulate hard rock with a high ratio of the uniaxial compressive strength to tensile strength（UCS/TS） and realistic strength-failure envelope,the rock deformation and mechanical characteristics were discussed in detail when the particle simulation method with the clump parallel-bond model（CPBM） was used to conduct a series of numerical experiments at the specimen scale.Meanwhile,the effects of the loading procedure and crack density on the mechanical behavior of a specimen,which was modeled by the particle simulation method with the CPBM,were investigated.The related numerical results have demonstrated that：1） The uniaxial compressive strength（UCS）,tensile strength（TS） and elastic modulus are overestimated when the conventional loading procedure is used in the particle simulation method with the CPBM; 2） The elastic modulus,strength and UCS/TS decrease,while Poisson ratio increases with the increase of the crack density in the particle simulation method with the CPBM; 3） The particle simulation method with the CPBM can be used to reproduce a high value of UCS/TS（10）,as well as a high friction angle and reasonable cohesion strength; 4） As the confining pressure increases,both the peak strength of the simulated specimen and the number of microscopic cracks increase,but the ratio of tensile cracks number to shear cracks number decreases in the particle simulation method with the CPBM; 5） Compared with the conventional parallel-bond model,the CPBM can be used to reproduce more accurate results for simulating the rock deformation and mechanical characteristics.     

Numerical simulation of the parabolic shell surface under blast wave loading

Deformation of parabolic shell surface under explosion shock waves is a complex dynamic problem. Because of reflection and interference of blast wave, it’s hard to analytically delineate the dynamic responds of radar parabolic shell surface on blast wave. To gain the characteristics of thin shell deformation under impulsive loading of blast wave, numerical simulation methods for blast load on the shell structure was studied and analyzed. Euler-Lagrange numerical simulation was implemented by AUTODYN code to simulate the problem. Through analysis on deflection feature of radial position under different explosive mass and detonation height, an equation was founded by fitting the deflection results from numerical simulation results of shockwave loading. Experiments were arranged to confirm the validity of the formula. The results gained by simulation are consistent with experiments, and the formula can be used to delineate the deflection of aluminum alloy parabolic shell under blast loading.     

Vertical dynamic response characteristics of single pile in non-homogeneous soil layers

A computational method and a mechanical model for evaluating the vertical dynamic harmonic response characteristics of a single pile embedded in non-homogeneous soil layers and subjected to harmonic loadings were established based on a certain assumption and the improved dynamic model of beam-on-Winkler foundation by using the principle of soil dynamics and structure dynamics. Both non-homogeneity of soil strata and softening effect of soil layer around the pile during vibration were simultaneously taken into account in the proposed computational model. It is shown through the comparative study on a numerical example that the numerical results of dynamic response of the single pile computed by the proposed method are relatively rational and can well agree with the numerical results computed from the well-known software of finite element method. Finally the parametric studies were conducted for a varied range of main parameters to discuss the effects of relevant factors on dynamic responses of the single pile embedded in non-homogeneous layered soils excited by harmonic loading with different frequencies.     

Application of particle trajectory model in 1D planar ejection

A simple one-dimensional planar model for ejection was set up based on experiments.And numerical simulation was performed on this model with particle trajectory model method.An Eulerian finite volume method was conducted to resolve gas field.And Lagrangian method was imposed to track each particle.The interaction between gas and particles was responded as source terms in governing equations which were induced by forces.The effects of total spraying mass,particle size and other factors on the mixture of particles and gas were investigated.The spatial distributions of particle mass and velocity at different time were presented.The result shows that the numerical results are qualitatively consistent to those of experiments.     

Numerical Simulation of Semi-solid Mould Filling Using SOLA-VOF Technique

A software code based on SOLA-VOF algorithm is developed for numerical simulation of mold filling of semi-solid metals.The semi-solid mould filling processes of A356 and AZ91D are studied based on the Power-Law viscosity model and constant viscosity model,respectively.Test molds with different thicknesses and shapes were chosen to validate the software code.The simulated mould filling sequence shows a good agreement with the experimental results.The viscosity distribution is also calculated and plotted with a post-processor.The results show that the software code can offer an effective understanding for semi-solid mold filling processes.     

Different human-simulated characteristics of the driver models in the forward simulation of hybrid electric vehicles

Based on the control theories of PID, fuzzy logic and expert PID, the driver models are built and applied in the forward simulation for hybrid electric vehicles (HEV). The impact to the vehicle speed tracking and the fuel economy is compared among the different driver models. The different human-simulated characteristics of the driver models are emphatically analyzed. The analysis results indicate that the driver models based on PID, simple fuzzy logic and expert PID are corresponding to the handling characteristics of different drives. The driver models of different human-simulated characteristics bring the handling divergence of drivers with different driving level and habit to the HEV forward simulation, and that is significant to the all-around verification and validation of the control strategy for HEV. System simulation results of different driver models validate the impact of driver models to the dynamic and fuel economy performance of HEV.     

Numerical simulation of the parabolic shellsurface under blast wave loading

Deformation of parabolic shell surface under explosion shock waves is a complex dynamicproblem. Because of reflection and interference of blast wave,it’s hard to analytically delineate thedynamic responds of radar parabolic shell surface on blast wave. To gain the characteristics of thinshell deformation under impulsive loading of blast wave,numerical simulation methods for blast loadon the shell structure was studied and analyzed. Euler-Lagrange numerical simulation was implemented by AUTODYN code to simulate the problem. Through analysis on deflection feature of radial position under different explosive mass and detonation height,an equation was founded by fitting thedeflection results from numerical simulation results of shockwave loading. Experiments were arranged to confirm the validity of the formula. The results gained by simulation are consistent withexperiments,and the formula can be used to delineate the deflection of aluminum alloy parabolicshell under blast loading.     

Dynamic characteristic analysis of whole machine tools based on Kriging model

In order to study the variation of machine tools＇ dynamic characteristics in the manufacturing space, a Kriging approximate model is proposed. Finite element method （FEM） is employed on the platform of ANSYS to establish finite element （FE） model with the dynamic characteristic of combined interface for a milling machine, which is newly designed for producing aero engine blades by a certain enterprise group in China. The stiffness and damping of combined interfaces are adjusted by using adaptive simulated annealing algorithm with the optimizing software of iSIGHT in the process of FE model update according to experimental modal analysis （EMA） results. The Kriging approximate model is established according to the finite element analysis results utilizing orthogonal design samples by taking into account of the range of configuration parameters. On the basis of the Kriging approximate model, the response surfaces between key response parameter and configuration parameters are obtained. The results indicate that configuration parameters have great effects on dynamic characteristics of machine tools, and the Kriging approximate model is an effective and rapid method for estimating dynamic characteristics of machine tools in the manufacturing space.     

Fast and Stable Surface Feature Simulation for Particle-Based Fluids

In order to efficiently and realistically capture microscopic features of fluid surface, a fast and stable surface feature simulation approach for particle-based fluids is presented in this paper. This method employs a steady tension and adhesion model to construct surface features with the consideration of the adsorption effect of fluid to solid. Molecular cohesion and surface area minimization are appended for surface tension, and adhesion is added to better show the microscopic characteristics of fluid surface. Besides, the model is integrated to an implicit incompressible smoothed particle hydrodynamics (SPH) method to improve the efficiency and stability of simulation. The experimental results demonstrate that the method can better simulates surface features in a variety of scenarios stably and efficiently.     

Mathematical modeling of fluid flow, heat transfer and inclusion transport in a four strand tundish

Mathematical simulation was used for trouble-shooting and optimization. By the mathematical simulation, fluid flow and beat transfer of molten-steel in a four-strand tundish of a billet caster under different conditions （bare tundish and tundish with flow control device） were analyzed, The results showed that （1） the tundish with flow control device （FCD） has an important effect on the fluid pattern and temperature distribution; （2） the unsteady, solving method was used to model the inclusion motions at different time perthds, and it showed that the FCD is advantageous to separate the nonmetallic inclusions. According to the simulation results, the main problem existing in the industry preduction was found, and some helpful rneasurements were executed. Consequently, the large nonmetallic inclusions were separated, and the content of total oxygen was reduced. The qualily of steel was greatly improved.     

Simplified Modeling and Mathematical Analysis in Cardiac Electric Field Propagation for Human and Animals

The different characteristics of cardiac electric field (CEF) radiation in humans and other animals are presented in this paper. Physical modeling and mathematical analysis are developed to comprehensively unveil the properties of CEF, based on typical heartbeat waveforms. Our numerical simulation results demonstrate that the frequency bandwidths and the cycle durations of CEF are different for healthy humans versus humans on the verge of death and for humans versus other animals. The results indicate that the present study may extensively contribute towards recognizing human beings or other animal targets quickly and accurately with CEF in dangerous situations or in other applications.     

Numerical simulation of icing effect and ice accretion on three-dimensional configurations

It is common for an aircraft to encounter icing weather conditions, which would be dangerous to the flight. Thus, there is a need to study the detail of icing effect and the process of ice accretion on the aircraft. In this paper, considering three different icing models according to weather conditions, i.e., sharp-angled ice, blunt-nosed ice and double horn ice, the Reynolds-averaged N-S equations and the S-A turbulence model are used to analyze the flow field for an iced wing/body configuration with a multi-block strategy and structured grid technique. The numerical result is compared with the experimental data. A flow solver is developed based on the Euler equations to investigate the ice accretion process. The droplets are tracked by using the Lagrangian method. In addition, a revised Messinger model is proposed to simulate the ice accretion. This numerical simulation is conducted for the ice accretion on an M6 wing and a wing/body/tail configuration. The presented results preliminarily show that the numerical methods are feasible and effective.     

Designing the cooling system of a hybrid electric vehicle with multi-heat source

In order to reduce the power consumption and meet the cooling demand of every heat source component,three kinds of multi-heat source cooling system schemes were designed base on the characteristic of power split hybrid electric vehicle( HEV). Using the numerical simulation method,the power system heat transfer model was built. By comparing the performance of three different schemes through the Simulink simulation,the best cooling system scheme was found. Base on characteristics of these cooling system structures,the reasonableness of the simulation results were analyzed and verified. The results showed that the cooling system designation based on the numerical simulation could describe the cooling system performance accurately. This method could simplify the design process,improve design efficiency and provide a new way for designing a multi-heat source vehicle cooling system.     

Simulation of hard–soft material interaction under impact loading employing the material point method

Understanding the mechanisms of hard–soft material interaction under impact loading is important not only in the defense industry but also in daily life.However,traditional mesh-based spatial discretization methods that are time consuming owing to the need for frequent re-meshing,such as the finite element method and finite difference method,can hardly handle large deformation involving failure evolution in a multi-phase interaction environment.The objective of this research is to develop a quasi-meshless particle method based on the material point method for the model-based simulation of the hard–soft material interaction response.To demonstrate the proposed procedure,scenarios of a hard–soft material impact test are considered,where a force is applied to layers of materials and a hard bar with an initial velocity impacts a target with layers of different materials.The stress wave propagation and resulting failure evolution are simulated and compared with available data.Future research tasks are then discussed on the basis of the preliminary results.     

Numerical analysis of bump foil bearings without nominal radial clearance

Bump foil bearings without nominal radial clearance were analyzed. An air film thickness model and a bearing theoretical analytical model were developed accounting for air compressibility and foil deformation. To analyze hydrodynamic characteristics of bump foil bearings with different operating eccentricities, the air film thickness equation and Reynolds equation were coupled through pressure and solved by Newton-Raphson Method （NRM） and Finite Difference Method （FDM）. The characteristics of an bump foil bearing model were discussed including load carrying capacity, film thickness and pressure distributions. The results of simulation show that bump foil bearing without nominal radial clearance can provide better stability and greater load capaci- ty. This numerical analytical method also reveals a good convergence in numerical calculation.     

Buffeting numerical simulation coupled with aerodynamics and structure based on MDDES

Unsteady effect of seriously separated flow is the main factor of modern aircraft buffeting. So accurate simulation of this complex flow becomes the basis associated with the research of aircraft buffeting. This paper constructs an unsteady numerical simulation method for separation flow based on modified delayed detached eddy simulation (MDDES) method by considering both modern computer resources and the credibility of simulating separation flow. The proposed method is also verified through the simulation of the separated flow by a typical fighter at high angle of attack. And then a robust and efficient technology for deforming mesh is established using radial basis function (RBF) and infinite interpolation method. Moreover, the platform for numerical simulation of buffeting is set up in combination with the structural dynamics equations in the modal space, by which the research of vertical tail buffeting caused by edge vortex is carried out on a fighter at large angle of attack. Through spectrum analysis of time-domain response of pressure pulsation on the location of vortex rupture, the results show that the pulsation frequency of vortex structure with different scales covers the inherent modal frequency of vertical tail structure. Compared to the Reynolds-averaged Navier-Stokes equations, the MDDES method can distinguish the more detailed and higher frequency small-scale vortex structure. Unlike flutter, displacement acceleration response of each mode in buffeting is dominated by its own mode. There exists strong coupling between the first bending mode and first torsion mode, and it leads to acceleration and large inertia impact of structure, which is the main factor causing structural fatigue. In sum, the obtained results verify the validity of the numerical means and the corresponding methods in the paper.     

Numerical investigation of water-entry of flatted-bottom seafloor mining tool in ocean waves

A numerical wave load model based on two-phase （water-air） Reynolds-Averaged Navier Stokes （RANS） type equations is used to evaluate hydrodynamic forces exerted on flatted-bottom seafloor mining tool during its entering ocean waves of deploying process. The discretization of the RANS equations is achieved by a finite volume approach （FV）. The volume of fluid method （VOF） is employed to track the complicated free surface. A numerical wave tank is built to generate the ocean waves which are suitable for deploying seafloor mining tool. A typical deploying condition is employed to reflect the process of flatted-bottom body impacting with waves, and the pressure distribution of bottom is also presented. Four different lowering velocities are applied to obtain the time histories of maximum pressure of bottom, and it can be concluded that the pressure coefficient decreases with water velocity increasing, which is similar with ordinary water entry case. The numerical results clearly demonstrate the characteristics of flatted-bottom body entering ocean waves.     

Scattering wave field around a cavity with circular cross-section embedded in saturated soil using boundary element method

Based on Biot＇s theory and considering the properties of a cavity, the boundary integral equations for the numerical simulation of wave scattering around a cavity with a circular cross-section embedded in saturated soil are obtained using integral transform methods. The Cauchy type singularity of the boundary integral equation is discussed. The effectiveness of the properties of soil mass and incident field on the dynamic stress concentration and pore pressure concentration around a cavity is analyzed. Our results are in good agreement with the existing solution. The numerical results of this work show that the dynamic stress concentration and pore pressure concentration are influenced by the degree of fluid-solid coupling as well as the pore compressibility and water permeability of saturated soil. With increased degree of fluid-solid coupling, the dynamic stress concentration improves from 1.87 to 3.42 and the scattering becomes more significant. With decreased index of soil mass compressibility, the dynamic stress concentration increases and its maximum reaches 3.67. The dynamic stress concentration increases from 1.64 to 3.49 and pore pressure concentration improves from 0.18 to 0.46 with decreased water permeability of saturated soil.     

Effect of pumping chamber on performance of non-overload centrifugal pump

In order to specify the characteristics of un-overloaded centrifugal pumps, the IH100-65-200 pump was chosen as the model pump. Different calculation models for centrifugal pumps were established under different pumping chamber sectional parameters. In the numerical simulation of the centrifugal pumps flow field, the shaft power, head, efficiency, and the changes of the internal flow field under different sectional areas and sectional shapes were studied with the RNG k-ε turbulence model, and the influence of the pumping chamber section characteristics of the non-overloaded centrifugal pumps were analyzed. The results show that sectional areas have a significant impact on the non-overload characteristics of centrifugal pumps. The shaft power and head of centrifugal pump are increasing with a lager sectional area, by which the gradient of head curves decreases. The efficiency is improved under a large flow rate condition, but the head and the efficiency are reduced at a small flow rate. It is also observed that the sectional shapes have less influence on the shaft power, the hydraulic performance and flow field characteristics of a centrifugal pump.     

Modeling and finite element analysis of rod and wire steel rolling process

Two thermomechanical coupled elastic-plastic finite element （FE） models were developed for predicting the 12-pass continuous rolling process of GCrl 5 rod and wire steel. The distances between stands in the proposed models were set according to the actual values, and the billets were shortened in the models to reduce the calculation time. To keep the continuity of simulation, a technique was developed to transfer temperature data between the meshes of different models in terms of nodal parameters by interpolation functions. The different process variables related to the rolling process, such as temperature, total equivalent plastic strain, equivalent plastic strain rate, and contact friction force, were analyzed. Also, the proposed models were applied to analyze the reason for the occurrence of an excessive spread in width. Meanwhile, it was also utilized to assess the influence of the roll diameter change on the simulated results such as temperature and rolling force. The simulated results of temperature are found to agree well with the measured results.