Dimensional Numerical Analysis Research Articles

Three dimensional modeling and numerical analysis of hydrogen effects on the thermomechanical response of Nickel–Titanium orthodontic applications

This paper deals with effects of the hydrogen presence on the thermo-mechanical behavior of NiTi shape memory alloys (SMAs), widely considered for manufacturing orthodontic archwires. A three dimensional phenomenological model is formulated, based on thermodynamics of irreversible processes. It takes into account the experimentally observed effects on the main physical mechanisms (martensitic transformation and reorientation of martensite). The assumption of an additive decomposition between a reversible lattice and a trapped hydrogen concentrations is adopted. The complete problem including chemical, thermal and mechanical balanced equations and their weak form are solved by the finite element method. A 3D hexahedral continuum finite element with five degrees of freedom per node (displacements, temperature and total hydrogen concentration) is developed. Its implementation is carried out in the Abaqus finite element software. Numerical results are presented and compared to experimental ones which show the significant effects of the hydrogen presence in NiTi SMA.

Slope topographic effects on the nonlinear seismic behavior of groups of similar buildings

AbstractThe occurrence of vibrational energy exchange between neighboring buildings via soil is a well‐known issue today as structure‐soil‐structure interaction (SSSI) problems. Furthermore, the seismic performance of buildings near the slopes considering seismic topography‐soil‐structure interaction (TSSI) is entirely different from their performance on the flat grounds considering seismic soil‐structure interaction (SSI). Therefore, this study evaluates the seismic response of three moments resistant frame steel buildings with 15, 10, and 5 stories using three dimensional numerical analysis as a new topography‐structure‐soil‐structure interaction (TSSSI) problem. This issue has not been investigated in previous studies to the best of the authors' knowledge. In each case of TSSSI, two, three, and four buildings with similar dynamic properties were simulated simultaneously. The effects of foundation's rocking, numbers of buildings, and the 2D and 3D arrangements of buildings were investigated, and the results of TSSSI cases were compared with the corresponding SSSI cases. The inelastic behavior for both building components and soil was considered in the simulations. Analyzes are performed based on seven earthquake records from which the average value was taken as final results. Results show that it is essential to consider the TSSSI effect, and it can completely change the seismic performance of buildings near the slopes. Although the effects of TSSI and SSSI on the seismic responses of the low‐rise similar structures are negligible relative to the SSI cases, the results show that the nonlinear TSSSI effects of adjacent buildings should be fully considered even for 5‐story low‐rise structures.

An Analytic Study of the Effect of a Vane on the Hydraulic Field around a Cylinder

The flow pattern around the cylinder body is a very serious problem and this problem may become more serious and sensitive, when we place a vane neighboring to the cylinder. The present paper deals with the vane impact on the flow pattern around the cylinder. To investigate this problem the ANSYS fluent software is employed in order to achieve the two dimensional numerical analysis. Here, Reynolds Average Navier Stokes model is adopted. The investigation comprises the following hydraulic variables, like eddy viscosity, turbulent intensity, turbulent kinetic energy, turbulent dissipation rate, flow velocity profile, static pressure and pressure coefficient. The constant flow velocity, cylinder diameter and vane dimension are adopted in this analysis, while the different certain distance between the vane and the cylinder is considered. The used vane has a rectangular shape. In this analysis, it is clear that the vane plays a sensitive vital role in the hydraulic behavior of the flow pattern around the cylinder. The study has taken up four distances between the vane and the cylinder, these distances is a function of the cylinder diameter, in addition to the direct touch that happens between the vane and the cylinder. The analysis also shows that when the cylinder has direct touch with the vane, the dramatic reduction will occur in hydraulic variables.

Overbank Floods of Lower Yellow River Based on Two - dimensional Numerical Simulation and Analysis

When the flow of the Yellow River is large, a large range of floodplains will be formed around the main channel, and the crisis will greatly improve safety. Analysis of the changes of flood peak shape, flood peak propagation speed and flood level at large flow rate plays an important role in the protection and flood prevention of the Yellow River levee. Based on the established two-dimensional mathematical model of Luokou to the Yellow River estuary, the data of peak flow, velocity and water level are obtained by simulation calculation. By drawing the flood peak evolution process map from Luokou to Yellow River estuary, the change of flood peak type and flood peak propagation speed are analyzed to provide technical support for flood defense.

Numerical Analysis of Geocell Reinforced Square Shallow Horizontal Plate Anchor

This paper presents the uplift behavior of horizontal square anchor in cohesionless soil reinforced with or without geocell in cohesionless soil using three dimensional analyses. The effects of embedded depth ( $$H$$ ), geocell width ( $$B_{g}$$ ), geocell height ( $$h$$ ), geocell pocket size ( $$a$$ ), distance from surface of plate anchor to bottom of geocell ( $$U$$ ), plate anchor width ( $$B$$ ), geocell material stiffness ( $$K$$ ), and relative density of cohesionless soil ( $$D_{r}$$ ) on the dimensionless breakout factor ( $$F_{q}$$ ) and uplift capacity of horizontal plate anchor ( $$Q_{ult}$$ ) were investigated numerically using PLAXIS 3D finite element software with Hardening Soil Model (HSM). The influence of these parameters on the dimensionless breakout factor was discussed and optimum design parameters ( $$B,\frac{{B_{g} }}{B},\frac{h}{B},\frac{a}{B},\frac{U}{B},K$$ ) were determined. Additionally, the results of three dimensional numerical analysis confirmed with those of laboratory indicate that the proposed model is able to capture the uplift load–displacement behavior of geocell reinforced square shallow horizontal plate anchor system in cohesionless soil.

Numerical analysis of two tube helical heat exchanger using various nano-fluids

The study conducts analysis of the impact of nano-fluids in improving heat transfer. These nano-fluids contain nanoparticles (Ag, TiO2, Al2O3, Cu, Fe, and Au) volume fraction ranging between 2% to 8%. Three dimensional numerical analysis has been carried on a double tube helical heat exchanger using ANSYS Fluent Software. Suitable 3-D equations are solved employing SIMPLE algorithm and discretized using Finite Volume Method. The results show that there will be an increase in heat transfer rate as the nanoparticle volume intensity increases. Further, from the present study it is clear that Au-H2O nano-fluid yields favourable results in comparison to other nano-fluids.

Deformation and Stability Analysis of Embankment over Stone Column-Strengthened Soft Ground

Compacted granular columns are commonly used to support embankments over soft soils. Using a reinforcement layer under the embankment causes the total stress to be further transferred to the column rather than soft soil, thus reducing total deformations of the subsoil. In this paper two dimensional (2D) numerical analysis was used to study the influence of stone columns and basal geosynthetic on deformations and stability of an embankment over soft deposit by means of Plaxis 2D finite element code. Unit cell to plane strain conversion approach was applied to transform columns into equivalent walls thus allowing to simulate a full embankment over a group of columns. Comprehensive parametric analysis was then performed to investigate the role of different critical parameters on embankment behavior. Results showed that the use of stone columns yielded the total deformations of the subsoil to significantly reduce, while its influence was less remarkable as a high stiffness geogrid was placed under the embankment. It was also found that the stone column length was the most influential parameter on the embankment total deformations, so that increasing columns length from 0.25Hs to 0.75Hs reduced the vertical and horizontal deformations by about two and five times, respectively. In addition, the use of a high stiffness basal geogrid caused the stability of the embankment to remarkably improve as the value of safety factor at the end of construction increased from 1.25 to about 1.9.

Three dimensional numerical analysis of heat transfer during spray quenching of 22MnB5 steel with a single nozzle

In this paper, a three dimensional Computational Fluid Dynamics Model (CFD) model was generated for spray cooling of straight parts by using a single point nozzle. The numerical simulations of spray quenching were performed to investigate the cooling rate of a 22MnB5 hot steel blank commonly used material in the automotive industry. Experiments are carried out to examine infrared thermograph of hot steel blank surfaces during spray cooling process by using infrared thermal camera. Time dependent situations of surface temperatures, surface heat fluxes and cooling areas are investigated numerically. The 3D model with some assumptions is presented to improve the solution of numeric simulation and to meet the most appropriate acceptable results for spray cooling process. The developed 3D model will be used to investigate the heat transfer analysis of hot stamped parts during hybrid quenching to optimize the process parameters. The comparison of the numerical and experimental results showed that the presented approach can be effectively used to evaluate heat transfer during spray quenching with a single nozzle. With this research, it was clearly seen that the estimated cooling rates and the temperatures were in good agreement with the experimental cooling temperature data. By using the numerical results and experimental data obtained in this study, multi-nozzle spray apparatus which will be used to obtain different cooling rates on the parts by changing spray parameters such as spray height, spray angle, mass flow rate, the distance between nozzles and part etc. was developed for hybrid quenching process.

Numerical Assessment of Squeezed Branch Pile in Silty Clay Soil

Squeezed Branch Pile is derived on the basis of caste in place concrete pile. It has one or more branches along the pile shaft at design depth. Squeezed branch piles are often used in high rise building, transmission tower and in other pile foundations where anticipated uplift or vertical load may cause failure. This pile is one of the excellent options of pile foundation for soft soil and silty soil. The behaviour of Squeezed Branch pile is difficult to explain using simple pile-soil theories or two dimensional numerical analyses because of complicated geometry of pile.In the present numerical analysis, a 3D pile-soil model of conventional circular pile and squeezed branch pile foundations are analysed using MIDAS GTS NX finite element software to find out effectiveness of squeezed branch pile over conventional pile. The aim is to study the performance of Squeezed Branch Pile foundation in silty clay with respect to various parameters such as types of loading, branch diameter, branch spacing and number of branches. Analysis shows that the squeezed branch pile has higher vertical, lateral and uplift load capacity as compared to conventional pile.

Effect of Impeller Parameters on the Flow inside the Centrifugal Blower using CFD

A numerical analysis is carried out to understand the flow characteristics for different impeller configurations of a single stage centrifugal blower. The volute design is based on constant velocity method. Four different impeller configurations are selected for the analysis. Impeller blade geometry is created with point by point method. Numerical simulation is carried out by CFD software GAMBIT 2.4.6 and FLUENT 6.3.26. GAMBIT work includes geometry definition and grid generation of computational domain. This process includes selection of grid types, grid refinements and defining correct boundary conditions. Processing work is carried out in FLUENT. The viscous Navier-Stokes equations are solved with control volume approach and the k-ε turbulence model. In this three dimensional numerical analysis is carried out with steady flow approach. The rotor and stator interaction is solved by mixing plane approach. Results of simulation are presented in terms of flow parameters, at impeller outlet and various angular positions inside the volute. Also, the contours of flow properties are presented at the outlet plane of fluid domain. Results suggest that for the same configurations of centrifugal blower, as we change geometrical parameter of impeller the flow inside the blower get affected.

Numerical simulation of unsteady galloping of two-dimensional iced transmission line with comparison to conventional quasi-steady analysis

Most of the previous works on numerical analysis of galloping of transmission lines are generally based on the quasi-steady theory. However, some wind tunnel tests of the rectangular section or hangers of suspension bridges have shown that the galloping phenomenon has a strong unsteady characteristic and the test results are quite different from the quasi-steady calculation results. Therefore, it is necessary to check the applicability of the quasi-static theory in galloping analysis of the ice-covered transmission line. Although some limited unsteady simulation researches have been conducted on the variation of parameters such as aerodynamic damping, aerodynamic coefficients with wind speed or wind attack angle, there is a need to investigate the numerical simulation of unsteady galloping of two-dimensional iced transmission line with comparison to wind tunnel test results. In this paper, it is proposed to conduct a two dimensional (2-D) unsteady numerical analysis of ice-covered transmission line galloping. First, wind tunnel tests of a typical crescent-shapes iced conductor are conducted firstly to check the subsequent quasi-steady and unsteady numerical analysis results. Then, a numerical simulation model consistent with the aeroelastic model in the wind tunnel test is established. The weak coupling methodology is used to consider the fluid-structure interaction in investigating a two-dimension numerical simulation of unsteady galloping of the iced conductor. First, the flow field is simulated to obtain the pressure and velocity distribution of the flow field. The fluid action on the iced conduct at the coupling interface is treated as an external load to the conductor. Then, the movement of the conduct is analyzed separately. The software ANSYS FLUENT is employed and redeveloped to numerically analyze the model responses based on fluid-structure interaction theory. The numerical simulation results of unsteady galloping of the iced conduct are compared with the measured responses of wind tunnel tests and the numerical results by the conventional quasi-steady theory, respectively.

Design and numerical analysis of an efficient H-Darrieus vertical-axis hydrokinetic turbine

Hydrokinetic turbines are one of the technological alternatives to generate and supply electricity for rural communities isolated from the national electrical grid with almost zero emission. The Darrieus turbine is one of the options that can be used as a hydrokinetic turbine due to its high power coefficient (Cp) and easy manufacture. In the present work, the design and hydrodynamic analysis of a Darrieus vertical-axis hydrokinetic turbine of 500 W was carried out. A free stream velocity of 1.5 m/s was used for the design of the blades. The diameter (D) and blade length (H) of the turbine were 1.5 m and 1.13 m, respectively. The blade profile used was NACA0025 with a chord length of 0.33 m and solidity () of 0.66. Two (2D) and three dimensional (3D) numerical analyses of the unsteady flow through the blades of the turbine were performed using ANSYS Fluent version 18.0, which is based on a Reynolds-Averaged Navier-Stokes (RANS) model. A transient 2D simulation was conducted for several tip speed ratios (TSR) using a k-ω Shear Stress Transport turbulence (SST) scheme. The optimal TSR was found to be around 1.75. Main hydrodynamic parameters, such as torque (T) and CP, were investigated. Additionally, 3 geometrical configurations of the turbine rotor were studied using a 3D numerical model in order to identify the best configuration with less Cp and T fluctuation. The maximum Cp average was 0.24 and the amplitude of Cp variation, near 0.24 for the turbine model with 3 blades of H equal to 1.13 m. On the other hand, for the turbine models with 6 and 9 blades of H equal to 0.565 m and 0.377 m, respectively, the maximum Cp averages were 0.51 and 0.55, respectively, and the amplitude of Cp variation, near 0.07 for the model with 6 blades and 0.17 for the model with 9 blades. This revealed that the hydrokinetic turbine with a geometrical configuration of 6 blades greatly improves the performance of the turbine due to this model has advantages compared to models with 3 and 9 blades, in terms of the reduction of their T curve fluctuation.

Three dimensional numerical analysis of hemodynamic of stenosed artery considering realistic outlet boundary conditions

Background and objectiveMortality rate increases globally among which one third is due to diseased blood vessels. Due to late diagnoses of the disease in vessels (severe stenoses), qualitative and rapid assessment becomes difficult. Earlier assessment of stenoses can lead to formulation of effective treatment protocol. It is often found that proliferation of secondary stenoses at downstream of a stenosed vessel depends on the degree of severity of primary stenoses. Numerical investigation of flow dynamics of blood in such condition helps in prediction of distributed field of secondarystenoses. This investigation also requires consideration of rigorous boundary conditions at inlet and outlet of defined flow domain. MethodsPatient-specific geometry of aortic arch with stenoses in descending aorta was considered for numerical estimation of biofluid dynamics. Boundary conditionsat inlet and outlet were extracted from time-resolved pulsed Doppler Ultrasound imaging at appropriate sections of the vessel. Womersley inlet flux was considered. Flow parameters like wall shear stress, oscillatory shear index, etc. were evaluated at upper and lower aortic arch of the vessel at different combinations of boundary conditions at inlet and four outlets respectively. ResultsEffect of outlet boundary conditions were acknowledged for the progression of secondary stenoses. Severity of primary stenoses was found influencing the progression of secondary stenoses. It was found that the outlets Left Subclavian Artery and Left Common Carotid Artery greatly influence the flow dynamic structure within the stenosed aortic arch. Simultaneously, lower wall of aortic-arch had shown more affinity for secondary stenoses progression. ConclusionAortic arch is a vital anatomical region of circulatory system which is vulnerable to progression of secondary stenoses in presence of primary stenoses in ascending or descending aorta. It also drives the author to speculate the influence of anurysm in descending aorta on this landmark of aortic arch.

Driving behavior of stepped and tapered offshore piles due to hammer blows

In this article, the drivability of stepped and tapered offshore piles with the same length and volume has been investigated under hammer blows. To justify the obtained results from field testing and numerical methods, this pile driving procedure has been analyzed and discussed with wave propagation mechanism. It will be shown that tapered pile can be confidently idealized as a number of prismatic segments connected rigidly to each other. This is an interesting finding that fully tapered or stepped piles have a better performance in pile driving and enable users to apply simple one dimensional numerical analysis for simulating pile drivability.

Three dimensional numerical analysis of inducer about suppression of cavitation instabilities by asymmetric slits on blades

Cavitation is the phenomenon in which liquid evaporates and vapor bubbles occur in the low pressure region such as a pressure of liquid is roughly less than saturated vapor pressure. The cavitation causes a bad in uence such as vibration, noise, and a decline in performance on the turbomachineries. Moreover, the unsteady cavitation brings the oscillations in the turbomachinery which is called cavitation instabilities. In our laboratory, the suppression technique of the cavitation instabilities by using asymmetric slits on each blade has been investigated as a simple method. From the numerical results, it was con rmed that the cavitation instabilities are completely suppressed by a certain arrangement of asymmetric slits. In this study, the three-dimensional numerical analysis of the inducer was conducted. Two inducers which have asymmetric slits were used for this calculation. Moreover, to consider the asymmetric slit for effectiveness of cavitation instabilities, transient analysis are conducted. Although arranging the asymmetric slit cannot completely suppress the phenomenon, the cavity volume becomes smaller than without slit in all blades. This indicates that arranging asymmetric slits has the possibility to weaken the amplitude of cavitation instabilities.

Analysis on the influence of double-line large diameter shield tunnel orthogonally underpassing tunneling on railway track group

In the process of urban traffic construction and reconstruction, the number of new tunnels crossing existing railways is increasing day by day.Based on the reconstruction project tunnel of Xiangyang Road in Weifang city underpassing Jiaoji Railway passenger dedicated line and Jiaoji Railway, the outer diameter of shield tunnel is 10.7 m, and the minimum cover soil thickness is 10.5 m, and the crossing length is 60 m. The three dimensional numerical simulation analysis was carried out to study the influence of the construction of the double-line parallel shield tunnel on the existing railway track group. The results show that the final settlement of the ground settlement of the railway subgrade centerline is “bimodal shape”; the maximum value of ground subsidence in the centerline of shield tunnel is -2.29mm, and the longitudinal influence range of shield construction is approximately 20 meters in front of the face to 40 meters in the rear. This study provides a reference for the implementation of similar double-line shield tunnel underpass railway engineering.

Analytical solution for tunnels not aligned with geostatic principal stress directions

It is well-known that rock masses may present marked stress anisotropy. However, most of the tunnel analyses (numerical and analytical) assume the tunnel axis aligned with one of the principal stress directions. When this is not the case, axial shear stresses appear, which then are neglected, as it is done in all analytical solutions available for tunnel analysis. Existing solutions may consider advanced nonlinear ground behavior (i.e. elastic-brittle-plastic with e.g. Hoek and Brown failure criteria), linear-elastic ground with transversely anisotropic properties, seismic loading, groundwater and support, etc., but all consider that the axis of the tunnel aligns with one of the principal far-field stresses. This is also what is generally assumed when conducting more sophisticated, three dimensional numerical analyses. In this paper, an analytical solution to calculate the stresses and displacements induced by far-field axial shear stresses is presented. Solutions for supported and unsupported tunnels are provided. The proposed analytical solution can be combined with the classical Kirsch and Einstein-Schwartz solutions to determine the complete stress and displacement fields around the tunnel. Further, the effects of stress anisotropy are discussed.

Experimental and Numerical Analyses of a Spark-Ignition Engine Firing with N-Butanol-Gasoline Blends at High Load Operation

In this paper, the potential of alcohol-gasoline blends as fuels for spark-ignition engines has been evaluated. The general purpose of the work is to verify the possibility of incrementing the bio-fuels penetration in the market of transportation fuels. As it is well known, bio-mass derived fuels, in fact, could significantly reduce the CO2 emissions of energy thermal systems.The behavior of a small, turbocharged spark-ignition engine, firing with gasoline-butanol blends, has been analyzed. Analyses have been carried out by means of both experimental tests and numerical simulations. In previous works, engine main performances have been illustrated and discussed. Here, experimental tests have been carried out in order to compare the engine knock resistance and the obtainable fuel conversion efficiency when the engine is fueled by pure gasoline or gasoline-butanol blends at high load operation. Furthermore, one dimensional numerical analyses have been utilized in order to compare the engine behavior, at different operating points, when it is firing with pure gasoline or pure butanol.In general, the obtained results seem to indicate that butanol (produced by bio-masses) is a viable alternative to fossil fuels in the way of CO2 emission reduction.

Two dimensional numerical modelling and analysis of a novel electromagnetic inductive valve

A novel type of electromagnetic inductive valve has been developed for the gas injector of the planar pulsed inductive plasma thruster. However, due to the complex operation process of the valve, the design work and the performance prediction can only be accomplished by experimentation. This paper explains a two dimensional model applied to predict the valve performance. The electromagnetic and mechanical aspects which dominate the valve operation process are treated as two weakly coupled problems. The equivalent circuit method is applied to analyze the electromagnetic problem where the valve is represented by a series of sub-conductors. The Lorentz force is calculated and introduced into the mechanical problem as an analytical load. Simulation and experimental validations are implemented in a prototype valve. Compared results from experiments convince that the present model can be used to predict the valve dynamic performances with satisfying accuracy. Moreover, the detailed insight with respect to the development of magnetic flux density, induced current, Lorentz force and velocity of the diaphragm is presented to better understand the valve operation process. The results indicate that the effective acceleration of the diaphragm occurs in the initial phase of valve opening. Only the diaphragm obtains enough kinetic energy during the first half cycle of the coil current, can the valve be fully opened.

Numerical Analysis on the Optimum Spacing of a Short and Large Diameter Soil Nailing System Under Railway Load

There are necessities of vertical excavation to reduce construction areas and make new spaces in urban area. In this study, 3 dimensional numerical analysis is conducted to assess the behaviour of the embankment with vertical excavation and a short and large diameter soil nailing reinforcement system. The spacing of soil nails are 1 m, 2 m, and 3 m, though the diameter is fixed as 40 cm. Lateral and vertical displacement at the top of wall, vertical displacement and axial stress are also obtained and analyzed. Consequently, lateral displacement at the top of wall increases sharply and tensile stress of soil nail excesses the allowable limit at the nail spacing of 3 m. Therefore, we concluded that the optimum spacing of a short and large diameter soil nailing system could be around 2m at the aspects of safety and cost efficiency for excavation and reinforcement of embankment. Keywords: Railway Embankment, Large Diameter Soil Nailing System, 3 Dimensional Numerical Analysis, Optimum Spacing