• Title/Summary/Keyword: Non-local boundary condition

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Recommendation for the modelling of Donnell shell: The relationship between non-local parameter and frequency

  • Mohamed A. Khadimallah;Muzamal Hussain;Elimam Ali;Sehar Asghar;Abdelouhed Tounsi
    • Computers and Concrete
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    • 제32권2호
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    • pp.165-172
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    • 2023
  • The vibration analysis of armchair, zigzag and chiral double-walled carbon nanotubes has been developed by inserting the nonlocal theory of elasticity into thin shell theory. First Donnell shell theory is employed while exercising wave propagation approach. Scale effects are realized by using different values of nonlocal parameters under certain boundary conditions. The natural frequencies have been investigated and displayed for various non-local parameters. It is noticed that on increasing nonlocal parameter, the frequency curve tends to decrease. The frequency estimates of clamped-free boundary condition are less than those of clamped-clamped and simply supported computations. The frequency comparisons are presented for armchair, zigzag and chiral nanotubes. The software MATLAB is used to extract the frequencies of double walled carbon nanotubes.

포물선 지배 방정식과 비국소적 경계조건의 근사 차수 불일치에 의한 해석적 오차 (Analytic Error Caused by the Inconsistency of the Approximation Order between the Non Local Boundary Condition and the Parabolic Governing Equation)

  • 이근화;성우제
    • 한국음향학회지
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    • 제25권5호
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    • pp.229-238
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    • 2006
  • 본 논문에서는 수치 영역의 포물선 지배 방정식의 근사 차수와 수치 영역 경계의 비국소적 경계 조건의 근사 차수가 서로 다를 때 음파 해에 미치는 영향을 해석적으로 보였다. 우선 평면파 분석법을 이용해 비국소적 경계 조건을 반 무한 매질 영역으로 변환했다. 그리고 실제 수치 영역과 반 무한 매질 영역의 경계에서 해석적 반사 오차를 유도했다. 지배 방정식과 비국소적 경계 조건의 해석적 오차가 간단한 대수 식으로 표현 가능한 경우에 대해서는 대수적인 오차식을 유도하고 그 경향을 고찰했다. 지배 방정식이 일반적인 고차 포물선 방정식일 때는 대수적인 오차 식은 보다 복잡하게 표현되며 수치적 방법을 이용해 그 특성을 고찰했다. 최종적으로 지배 방정식의 차수에 따른 비국소적 경계 조건의 정밀도를 유도하고 해석적 반사 오차의 전반적인 특성에 대해 논의했다. 본 연구의 핵심 공헌은 포물선 방정식과 비국소적 경계 조건의 근사 차수가 다를 때 해석적 오차 추정 방법과 사용한계를 제시했다는데 있다.

꼭지점에서의 응력 집중 현상을 고려한 자유단 경계조건을 가진 임의 다각형 형상 평판의 자유 진동 해석 (Free Vibration Analysis of Arbitrarily Shaped Polygonal Plates with Free Edges by Considering the Phenomenon of Stress Concentration at Corners)

  • 강상욱
    • 한국소음진동공학회논문집
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    • 제17권3호
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    • pp.220-225
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    • 2007
  • Free vibration analysis using the method of NDIF (non-dimensional dynamic influence function), which was developed by the author, is extended to arbitrarily shaped polygonal plates with free edges. Local Cartesian coordinate systems are employed to apply the free boundary condition to nodes distributed along the edges of the plate of interest. Furthermore, a new way for applying the free boundary condition to nodes located at corners of the plate is for the first time introduced by considering the phenomenon of stress concentration at the corners. Two case studies show that the proposed method is valid and accurate when the eigenvalues by the proposed method are compared to those by FEM(ANSYS).

The Perfectly Matched Layer applied to the Split-Step Pade PE Solver in an Ocean Waveguide

  • Lee, Keun-Hwa;Seong, Woo-Jae
    • The Journal of the Acoustical Society of Korea
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    • 제25권3E호
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    • pp.131-136
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    • 2006
  • The PML developed for the radio wave propagation is a powerful numerical domain truncation technique. We perform an analytic study on the reflection from the PML inserted in the ocean bottom. In the ocean bottom, we show the PML to have the improved performance but simultaneously the degeneration below the critical angle of the fast ocean bottom. The degeneration of the PML can be simply relaxed by stretching the thickness of the PML or putting the attenuation coefficient to the ocean bottom. As a better solution, we propose the improved truncation technique based on the PML and the non-local boundary condition. Finally, we apply the PML to the acoustic wave propagation using split-step Pade PE solver. For the problems of the ocean waveguide, the numerical efficiency of the PML is examined and the usefulness of the PML is confirmed.

EXISTENCE OF INFINITELY MANY SOLUTIONS FOR A CLASS OF NONLOCAL PROBLEMS WITH DIRICHLET BOUNDARY CONDITION

  • Chaharlang, Moloud Makvand;Razani, Abdolrahman
    • 대한수학회논문집
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    • 제34권1호
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    • pp.155-167
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    • 2019
  • In this article we are concerned with some non-local problems of Kirchhoff type with Dirichlet boundary condition in Orlicz-Sobolev spaces. A result of the existence of infinitely many solutions is established using variational methods and Ricceri's critical points principle modified by Bonanno.

원관 주위의 대류 열전달에서 경계조건에 대한 원주방향 열전도의 영향 (Effect of Circumferential Wall Heat Conduction on Boundary Conditions for Convection Heat Transfer from a Circular Tube in Cross Flow)

  • 이상봉;이억수;김시영
    • 한국해양공학회지
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    • 제15권2호
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    • pp.39-45
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    • 2001
  • With uniform heat generation from the inner surface of the cylindrical heater placed in a cross flow boundary condition, heat flow that is conducted along the wall of the heater creates a non-isothermal surface temperature and non-uniform heat flux distribution. In the present investigation, the effects of circumferential wall heat conduction on convection heat transfer is investigated for the case of forced convection around horizontal circular tube in cross flow of air. The wall conduction number which can be deduced from the governing energy equation should be used to express the effect of circumferential wall heat conduction. It is demonstrated that the circumferential wall heat conduction influences local Nusselt numbers of one-dimensional and two-dimensional solutions.

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NUMERICAL METHOD FOR A SYSTEM OF CAPUTO FRACTIONAL DIFFERENTIAL EQUATIONS WITH NON-LOCAL BOUNDARY CONDITIONS

  • S. Joe Christin Mary;Ayyadurai Tamilselvan
    • 대한수학회논문집
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    • 제38권1호
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    • pp.281-298
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    • 2023
  • A class of systems of Caputo fractional differential equations with integral boundary conditions is considered. A numerical method based on a finite difference scheme on a uniform mesh is proposed. Supremum norm is used to derive an error estimate which is of order κ − 1, 1 < κ < 2. Numerical examples are given which validate our theoretical results.

PTC형 집열기의 원관형 흡수기에서의 복합열전달 (Conjugate Heat Transfer for Circular Absorber in Parabolic Trough Concentrator)

  • 정종만;서태범;강용혁
    • 태양에너지
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    • 제20권1호
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    • pp.81-89
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    • 2000
  • In the present study, the characteristics of conductive and convective heat transfer occurred in a circular absorber of PTC (parabolic trough concentrator) for medium temperature solar energy utility were numerically investigated. A circular tube was considered as an absorber and the shape of PTC modeled in this study was based on the system that was installed in Korea Institute of Energy Research. Not only convection inside the tube but also conduction through the wall of the tube were analyzed, simultaneously. Circumferentially non-uniform heat flux that was simulated from the non-uniform solar disc model proposed by Jose was applied as thermal boundary condition on the tube surface. And, hydrodynamically fully developed laminar velocity profile was used as the inlet boundary condition and it was assumed that the working fluid was water. And, local heat fluxes at the interface of the tube and the working fluid were calculated for different wall thickness and thermal conductivity of the tube at various Reynolds number. Based on the results, the effects of thermal conduction of the tube on the local heat transfer were investigated.

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FDS 기법과 HCIB법을 이용한 3차원 내면파 수치 모사 (NUMERICAL SIMULATION OF THREE-DIMENSIONAL INTERNAL WAVES USING THE FDS SCHEME ON THE HCIB METHOD)

  • 신상묵
    • 한국전산유체공학회지
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    • 제17권1호
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    • pp.8-15
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    • 2012
  • A code developed using the flux-difference splitting scheme on the hybrid Cartesian/immersed boundary method is applied to simulate three-dimensional internal waves. The material interface is regarded as a moving contact discontinuity and is captured on the basis of mass conservation without any additional treatment across the interface. Inviscid fluxes are estimated using the flux-difference splitting scheme for incompressible fluids of different density. The hybrid Cartesian/immersed boundary method is used to enforce the boundary condition for a moving three-dimensional body. Immersed boundary nodes are identified within an instantaneous fluid domain on the basis of edges crossing a boundary. The dependent variables are reconstructed at the immersed boundary nodes along local normal lines to provide the boundary condition for a discretized flow problem. The internal waves are simulated, which are generated by an pitching ellipsoid near an material interface. The effects of density ratio and location of the ellipsoid on internal waves are compared.

난류 모수화 방법에 따른 대기경계층 수치모의 특성에 관한 연구 (Numerical Study on Characteristics of Turbulence Scheme in Planetary Boundary Layer)

  • 전원배;이화운;이순환
    • 한국환경과학회지
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    • 제19권2호
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    • pp.137-148
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    • 2010
  • This paper investigates the characteristics of turbulence schemes. Turbulence closures are fundamental for modeling the atmospheric diffusion, transport and dispersion in the boundary layer. In particular, in non-homogeneous conditions, a proper description of turbulent transport in planetary boundary layer is fundamental aspect. This study is based on the Regional Atmospheric Modeling System (RAMS) and combines four different turbulence schemes to assess if the different schemes have a impact on simulation results of vertical profiles. Two of these schemes are Isotropc Deformation scheme (I.Def) and Anisotropic deformation scheme (A.Def) that are simple local scheme based on Smagorinsky scheme. The other two are Mellor-Yamada scheme (MY2.5) and Deardorff TKE scheme (D.TKE) that are more complex non-local schemes that include a prognostic equation for turbulence kinetic energy. The simulated potential temperature, wind speed and mixing ratio are compared against radiosonde observations from the study region. MY2.5 shows consistently reasonable vertical profile and closet to observation. D.TKE shows good results under relatively strong synoptic condition especially, mixing ratio simulation. Validation results show that all schemes consistently underestimated wind speed and mixing ratio but, potential temperature was somewhat overestimated.