• Title/Summary/Keyword: Microscopic Simulation

Search Result 204, Processing Time 0.034 seconds

Assessment of Pedestrian Comfort Levels Based on the Microscopic Features of Pedestrian Traffic Flow (보행교통류 시뮬레이션 모형을 활용한 보행편의성 지표의 개발 및 분석)

  • LEE, Joo-Yong
    • Journal of Korean Society of Transportation
    • /
    • v.34 no.6
    • /
    • pp.499-509
    • /
    • 2016
  • The pedestrian traffic flow has more complicated microscopic features than vehicular traffic flow. Without any designated lanes or any guidance, pedestrians naturally move and change their routes in two dimensional domain with ease. Thus the assessment of pedestrian comfort level should be considering the microscopic features of pedestrian flow. This study is aimed at developing pedestrian comfort criteria based upon pedestrian flow simulation model. This study suggests three criteria to determine pedestrian comfort level; the deviation of route, the acceleration of walk, and the number of collision. Each criterion, which can address the unique walking patterns of pedestrian flow, is represented as each different function with respect to traffic flow rate. The criteria can be the additional indicators to determine the level of service of pedestrian flow together with traffic flow rate and walking speed.

Conceptual Models for Evaluation of Urban Logistics Improvement (도시물류 개선 대안 평가를 위한 개념적 모형 정립)

  • 허윤수;남기찬;윤항묵
    • Journal of Korean Society of Transportation
    • /
    • v.19 no.5
    • /
    • pp.7-18
    • /
    • 2001
  • This study is concerned with theoretical aspects of urban logistics with the aim of revealing limitations of the literature, suggesting directions for further studies and developing a conceptual model for evaluating policy alternatives. Several limitations have been revealed and, based on these, the directions for further studies were suggested as more effort needs to be put on microscopic aspects of urban logistics ; and integrated conceptual evaluation models need to be developed. For the models it defined microscopic evaluation factors by the subject of urban logistics activities, and with these factors it established a conceptual model. Especially it introduced the simulation models developed recently to predict the route of freight vehicles and suggested how both microscopic and macroscopic aspects of urban logistics could be evaluated.

  • PDF

Discrete element numerical simulation of dynamic strength characteristics of expanded polystyrene particles in lightweight soil

  • Wei Zhou;Tian-shun Hou;Yan Yang;Yu-xin Niu;Ya-sheng Luo;Cheng Yang
    • Geomechanics and Engineering
    • /
    • v.34 no.5
    • /
    • pp.577-595
    • /
    • 2023
  • A dynamic triaxial discrete element numerical model of lightweight soil was established using the discrete element method to study the microscopic mechanism of expanded polystyrene (EPS) particles in the soil under cyclic loading. The microscopic parameters of the discrete element model of the lightweight soil were calibrated depending on the dynamic triaxial test hysteresis curves. Based on the calibration results, the effects of the EPS particles volume ratio and amplitude on the contact force, displacement field, and velocity field of the lightweight soil under different accumulated strains were studied. The results showed that the hysteresis curves of lightweight soil exhibit nonlinearity, hysteresis, and strain accumulation. The strain accumulated in remolded soil is mainly tensile strain, and that in lightweight soil is mainly compressive strain. As the volume ratio of EPS particles increased, the contact force first increased and then decreased, and the displacement and velocity of the particles increased accordingly. With an increase in amplitude, the dynamic stress of the particle system increased, and the accumulation rate of the dynamic strain of the samples also increased. At 5% compressive strain, the contact force of the particles changed significantly and the number of particles deflected in the direction of velocity also increased considerably. These results indicated that the cemented structure of the lightweight soil began to fail at a compressive strain of 5%. Thus, a compressive strain of 5% is more reasonable than the dynamic strength failure standard of lightweight soil.

Development of Multiscale Simulation Technique for Multiphase Fluid System (다상 유체 시스템의 다중 스케일 시뮬레이션 기법에 관한 연구)

  • Han, Min-Sub
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.34 no.6
    • /
    • pp.569-577
    • /
    • 2010
  • A multiscale particle simulation technique that can be applied to a multiphase fluid system has been developed. In the boundary region where the macroscopic- and microscopic-scale models overlap each other, three distinctive features are introduced in the simulation. First, a wall is set up between the gas and liquid phases to separate them and match the phases respectively to the macroscopic conditions stably. Secondly, the interfacial profile is obtained near the matching region and the wall translates and rotates to accommodate the change in the liquid-vapor interfacial position in the molecular model. The contact angle thus obtained can be sent to the macroscopic model. Finally, a state of mass and temperature in the region is maintained by inserting and deleting the particles. Good matching results are observed in the cases of the complete and partial wetting fluid systems.

HIP Diffusion Bonding of Two Types of Superalloys for Engine Blisk Applications (엔진 블리스크 제조를 위한 초내열합금 이종재의 HIP Diffusion Bonding)

  • 나영상;황형철;염종택;권영삼;박노광
    • Transactions of Materials Processing
    • /
    • v.12 no.1
    • /
    • pp.60-65
    • /
    • 2003
  • HIP diffusion bonding of Ni-based superalloys, cast Mar-M247 (MM247) and Udimet 720 (U720) powder, was experimentally and numerically studied. Subsolvus HIP treatment was optimized by investigating the variations of high temperature tensile properties of HIP-bonded specimens with powder size, HIP'ing time, etc. While the tensile strength at high temperatures showed no detectable changes, the tensile elongation and reduction in area were slightly increased as the powder size decreased from -140 mesh to -270 mesh. While as-HIP'ed U720 showed a high tensile strength comparable to that of lorded U720 alloy, the HIP diffusion-bonded specimen showed a strength lower than the forged U720 alloy and the cast MM247 alloy The increase of HIP'ing tune from 2 hours to 3 hours resulted in a rapid risc of tensile strength and elongation due to the disappearence of microvoids in the cast MM247. FEM simulation for HIP process was conducted by applying the McMeeking micromechanical model, which uses power-law creep model as constitutive equations. ABAQUS user subroutine CREEP with an implemented microscopic model was used for the simulation. Numerical simulation was shown to be essential for the near-net shape manufacturing as well as the HIP process optimization.

Light Scattering from Microscopic Structure and Its Role on Enhanced Haze Factor

  • Kang, Junyoung;Park, Hyeongsik;Yi, Junsin
    • Proceedings of the Korean Vacuum Society Conference
    • /
    • 2016.02a
    • /
    • pp.340-340
    • /
    • 2016
  • We have prepared alumina (Al2O3) doped zinc oxide (AZO) films by DC magnetron sputtering (MS) technique and obtained higher self surface texturing at a high target angle (f). We have characterized the films and applied it as a front electrode of a single junction amorphous silicon solar cell. At a lower f the deposited films show higher values of optical gap (Eg), charge carriers mobility & concentration, crystallite grain size and wider wavelength range of transmission. At higher target angle the sheet resistance, surface roughness, haze factor etc for the films increase. For f=72.5o the haze factor for diffused transmission becomes 6.46% at 540 nm wavelength. At f=72.5o the material shows a reduction in crystallinity and evolution of a hemispherical-type sub-micron surface textures. A Monte Carlo method (MCM) of simulation of the AZO film deposition shows that such an enhanced self-surface texturing of the films at higher f is possible.

  • PDF

Numerical Study on the Changes in Microscopic Meteorological Elements due to Land Use Variations in the Nakdong River Basin (낙동강 하천 토지이용 변화에 따른 미세규모 기상 요소의 변동에 관한 수치 연구)

  • Kim, Eun-Ji;Lee, Soon-Hwan
    • Journal of Environmental Science International
    • /
    • v.25 no.12
    • /
    • pp.1597-1611
    • /
    • 2016
  • A numerical assessment using mesoscale-CFD (computational fluid dynamics) coupled A2C (atmosphere to CFD) model was carried out to analyze the variation of microscopic air flow pattern due to the construction of the Chilgok barrage in the Nakdong River. Scenarios with air flow patterns were classified into pre- and post-construction. The increased width of the river due to the construction of the Chilgok barrage induced obvious changes in moisture and the thermal environment around the river. However, air temperature variation was restricted within an area along the windward side in the numerical assessment. The impact of barrage construction on air temperature tends to be stronger during the nighttime than the daytime. It also stronger during the winter than the summer. In the simulation, the convergence of mesoscale wind is more pronounced after barrage construction than before. This is caused by the change of heat flux pattern induced by the widening of the river. Although this work is a case study with restricted atmospheric stability conditions that has several limitations in the numerical simulations, the impacts of the land-use changes brought about by the construction of the barrage in the river acceptable.

Impact analysis of composite plate by multiscale modeling (멀티스케일 모델링에 의한 복합재료 평판의 충격해석)

  • Ji Kuk Hyun;Paik Seung Hoon;Kim Seung Jo
    • Proceedings of the Korean Society For Composite Materials Conference
    • /
    • 2004.04a
    • /
    • pp.67-70
    • /
    • 2004
  • An investigation was performed to study the impact damage of the laminated composite plates caused by a low- velocity foreign object with multi-scale modeling based on the concepts of Direct Numerical Simulation (DNS)[4]. In the micro-scale part, we discretize the composite plates through separate modeling of fiber and matrix for the local microscopic analysis. A micro-scalemodel was developed for predicting the initiation of the damage and the extent of the final damage as a function of material properties, laminate configuration and the impactor's mass, etc. Anda macro-scale model was developed for description of global dynamic behavior. The connection betweenmicroscopic and macroscopic is implemented by the tied interface constraints of LS-DYNA contact card. A transient dynamic finite element analysis was adopted for calculating the contact force history and the stresses and strains inside the composites during impact resulting from a point-nose impactor. The low-velocity impact events such as contact force, deformation, etc. are simulated in the macroscopic sense and the impact damages, fiber-breakage, matrix cracking and delamination etc. are examined in the microscopic sense.

  • PDF

Experimental and numerical study on pre-peak cyclic shear mechanism of artificial rock joints

  • Liu, Xinrong;Liu, Yongquan;Lu, Yuming;Kou, Miaomiao
    • Structural Engineering and Mechanics
    • /
    • v.74 no.3
    • /
    • pp.407-423
    • /
    • 2020
  • The pre-peak cyclic shear mechanism of two-order asperity degradation of rock joints in the direct shear tests with static constant normal loads (CNL) are investigated using experimental and numerical methods. The laboratory testing rock specimens contains the idealized and regular two-order triangular-shaped asperities, which represent the specific geometrical conditions of natural and irregular waviness and unevenness of rock joint surfaces, in the pre-peak cyclic shear tests. Three different shear failure patterns of two-order triangular-shaped rock joints can be found in the experiments at constant horizontal shear velocity and various static constant normal loads in the direct and pre-peak cyclic shear tests. The discrete element method is adopted to simulate the pre-peak shear failure behaviors of rock joints with two-order triangular-shaped asperities. The rock joint interfaces are simulated using a modified smooth joint model, where microscopic scale slip surfaces are applied at contacts between discrete particles in the upper and lower rock blocks. Comparing the discrete numerical results with the experimental results, the microscopic bond particle model parameters are calibrated. Effects of cyclic shear loading amplitude, static constant normal loads and initial waviness asperity angles on the pre-peak cyclic shear failure behaviors of triangular-shaped rock joints are also numerically investigated.

Microscopic damping mechanism of micro-porous metal films

  • Du, Guangyu;Tan, Zhen;Li, Zhuolong;Liu, Kun;Lin, Zeng;Ba, Yaoshuai;Ba, Dechun
    • Current Applied Physics
    • /
    • v.18 no.11
    • /
    • pp.1388-1392
    • /
    • 2018
  • Metal thin films are used widely to solve the vibration problem. However, damping mechanism is still not clear, which limits the further improvement of the damping properties for film and the development of multi-functional damping coating. In this paper, Damping microscopic mechanism of porous metal films was investigated at both macroscopically and microscopically mixed levels. Molecular dynamics simulation method was used to model and simulate the loading-unloading numerical experiment on the micro-pore and vacancy model to get the stress-strain curve and the microstructure diagram of different defects. And damping factor was calculated by the stress-strain curve. The results show that dislocations and new vacancies appear in the micro-pores when metal film is stretched. The energetic consumption from the motion of dislocation is the main reason for the damping properties of materials. Micro-mechanism of damping properties is discussed with the results of in-situ experiment.