• Title/Summary/Keyword: discrete-element

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UNCONDITIONALLY STABLE GAUGE-UZAWA FINITE ELEMENT METHODS FOR THE DARCY-BRINKMAN EQUATIONS DRIVEN BY TEMPERATURE AND SALT CONCENTRATION

  • Yangwei Liao;Demin Liu
    • Bulletin of the Korean Mathematical Society
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    • v.61 no.1
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    • pp.93-115
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    • 2024

  • In this paper, the Gauge-Uzawa methods for the Darcy-Brinkman equations driven by temperature and salt concentration (DBTC) are proposed. The first order backward difference formula is adopted to approximate the time derivative term, and the linear term is treated implicitly, the nonlinear terms are treated semi-implicit. In each time step, the coupling elliptic problems of velocity, temperature and salt concentration are solved, and then the pressure is solved. The unconditional stability and error estimations of the first order semi-discrete scheme are derived, at the same time, the unconditional stability of the first order fully discrete scheme is obtained. Some numerical experiments verify the theoretical prediction and show the effectiveness of the proposed methods.

  • https://doi.org/10.4134/BKMS.b230051 인용 PDF

The evaluation of applicability of spectral element method for the dynamic analysis of the spatial structures (대공간 구조 시스템의 동적 해석을 위한 스펙트럴 요소법의 적용성 평가)

  • Han, Sang-Eul;Lee, Sang-Ju;Cho, Jun-Yeong
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2007.04a
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    • pp.789-794
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    • 2007

  • Recently, the necessity of efficient and exact method to analyze structures is increasing with the importance of the seismic analysis. But the finite element method used in many field do not give the exact solution unless the length of the element is very short enough to represent the deformation of the element. Because the amount of computer calculation increase with the increasing of the number of degree of freedoms, the finite element method for the exact dynamic analysis of structures would not be efficient. To solve these problems, spectral clement method combined spectral method using the principle of wave mechanics and finite element method for the analysis of discrete models is applied to evaluate the behavior of the spatial structures. As a result of analysis. it becomes clear that the spectral element method is faster and more exact than the finite clement method.

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Design Methodology of Automotive Wheel Bearing Unit with Discrete Design Variables (이산 설계변수를 포함하고 있는 자동차용 휠 베어링 유닛의 설계방법)

  • 윤기찬;최동훈
    • Transactions of the Korean Society of Automotive Engineers
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    • v.9 no.1
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    • pp.122-130
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    • 2001

  • In order to improve the efficiency of the design process and the quality of the resulting design, this study proposes a design method for determining design variables of an automotive wheel-bearing unit of double-row angular-contact ball bearing type by using a genetic algorithm. The desired performance of the wheel-bearing unit is to maximize system life while satisfying geometrical and operational constraints without enlarging mounting spae. The use of gradient-based optimization methods for the design of the unit is restricted because this design problem is characterized by the presence of discrete design variables such as the number of balls and standard ball diameter. Therefore, the design problem of rolling element bearings is a constrained discrete optimization problem. A genetic algorithm using real coding and dynamic mutation rate is used to efficiently find the optimum discrete design values. To effectively deal with the design constraints, a ranking method is suggested for constructing a fitness function in the genetic algorithm. A computer program is developed and applied to the design of a real wheel-bearing unit model to evaluate the proposed design method. Optimum design results demonstrate the effectiveness of the design method suggested in this study by showing that the system life of an optimally designed wheel-bearing unit is enhanced in comparison with that of the current design without any constraint violations.

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Design Optimization of Deep Groove Ball Bearing with Discrete Variables for High-Load Capacity (이산 설계변수를 포함하고 있는 깊은 홈 볼 베어링의 고부하용량 설계)

  • Yun, Gi-Chan;Jo, Yeong-Seok;Choe, Dong-Hun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.8 s.179
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    • pp.1940-1948
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    • 2000

  • A design method for maximizing fatigue life of the deep groove ball bearing without enlarging mounting space is proposed by using a genetic algorithm. The use of gradient-based optimization methods for the design of the bearing is restricted because this design problem is characterized by the presence of discrete design variables such as the number of balls and standard ball diameter. Therefore, the design problem of rolling element bearings is a constrained discrete optimization problem. A genetic algorithm using real coding is used to efficiently find the optimum discrete design values. To effectively deal with the design constraints, a ranking method is suggested for constructing a fitness function in the genetic algorithm. Constrains for manufacturing are applied in optimization scheme. Results obtained for several 63 series deep groove ball bearings demonstrated the effectiveness of the proposed design methodology by showing that the average basic dynamic capacities of optimally designed bearings increased about 9-34% compared with the standard ones.

  • https://doi.org/10.22634/KSME-A.2000.24.8.1940 인용 PDF

Multi-Level Optimization for Steel Frames using Discrete Variables (이산형 변수를 이용한 뼈대구조물의 다단계 최적설계)

  • 조효남;민대홍;박준용
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.15 no.3
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    • pp.453-462
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    • 2002

  • Discrete-sizing or standardized steel profiles are used in steel design and construction practice. However, most of numerical optimization methods follow additional step(round-up discrete-sizing routine) to use the standardized steel section profiles, and accordingly the optimality of the resulting design nay be doubtful. Thus, in this paper, an efficient multi-level optimization algorithm is proposed to improve the shortcoming of the conventional optimization methods using the round-up discrete-sizing routine. Also, multi-level optimization technique with a decomposition method that separates both system-level and element-level is incorporated in the algorithm to enhance the performance of the proposed algorithms. The proposed algorithm is expected to achieve considerable improvement on both the efficiency of the numerical process and the accuracy of the global optimum.

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