• 제목/요약/키워드: Arbitrary Shapes

검색결과 150건 처리시간 0.023초

Supersonic Plug Nozzle Design and Comparison to the Minimum Length Nozzle Configuration

  • Zebbiche, Toufik;Youbi, ZineEddine
    • International Journal of Aeronautical and Space Sciences
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    • 제7권1호
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    • pp.27-42
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    • 2006
  • A method to design the contour and conception of a plug nozzle of arbitrary shape, but specified exit flow conditions is presented. Severals shapes can be obtained for exit Mach number by changing the specific heats ratio. The characteristics of the nozzle in terms of length, weight and pressure force exerted on the wall are compared to the Minimum Length Nozzle and found to be better. Our field of study is limited to the supersonic mode to not to have the dissociation of the molecules. The design method is based on the use of the Prandtl Meyer function of a perfect gas. The flow is not axial at the throat, which may be advantageous for many propulsion applications. The performance benefits of the plug nozzle compared to the Minimum Length Nozzle are also presented.

수평 및 수직방향 지진력을 받는 단층 래티스 돔의 좌굴 거동 특성에 관한 연구 (A Study on the Buckling Characteristics of Single Layer Latticed Domes under Horizontal and Vertical Earthquake Motions)

  • 한상을;유용주;이상주;이경수
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 1998년도 가을 학술발표회 논문집
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    • pp.489-496
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    • 1998
  • The single layer latticed domes have various behaviors with each geometrical shape and scale, and they are affected by vertical component as well as horizontal component of the dynamic load. And they represent ye different earthquake responses under each ground acceleration compared with another structural systems. Generally, all of the members of latticed domes undergo three dimensional deflections if they are subjected to arbitrary one dimensional horizontal load under earthquake motions. And their response characteristics are very different to their shapes, rise/span ratios, and damping mechanisms. In this study, the earthquake response behavior is verified according to the factor of each shape, rise/span ratio, and damping ratio of latticed domes, which undergo horizontal and vertical earthquake motions by numerical approaches.

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비대칭 변단면 보의 고유진동수 (Natural Frequencies of Nonsymmetrically Tapered Beams)

  • 백봉인;안성기;김순철;이수곤
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 1999년도 가을 학술발표회 논문집
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    • pp.267-274
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    • 1999
  • An understanding of the natural frequencies of a beam is virtually a prerequisite to the understanding of its response in forced vibration due to shock, ground acceleration or moving loads. Contrary to the frequencies of the prismatic bars with arbitrary boundary conditions, those of a tapered bar are hard to determine when one employs convevtional neutral equilibrium or energy method. In this paper, finite element method is adopted to determine the fundamental frequencies of the non-symmetrically tapered bars. The bars assume the shapes of straight lines along the axis. The parameters considered in this study are sectional parameter, m,n and taper parameter, $\alpha$ For the structural engineer's convenience, the results by finite element method are expressed by simple algebraic equations, by which first mode frequencies are easily estimated. And they agree fairy well with those by F.E.M in most cases.

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밀집형 열교환기에 사용하는 평판핀 성능에 관한 수치적 연구 (Numerical investigation of plate fin performance for a compact heat exchanger)

  • 유재욱;송태호
    • 설비공학논문집
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    • 제11권3호
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    • pp.292-300
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    • 1999
  • Fin conduction not only enhances heat transfer to the ambient air but also increases tube-to-tube conduction. The latter is known to deteriorate the heat exchanger performance. Heat conduction between neighboring tubes thorough the fin is numerically investigated for accurate performance analysis of plate finned-tube heat exchangers. Governing equations for arbitrary plate fin are solved and the temperature distribution is obtained using the principle of superposition. Analysis is made using finite element method by changing the shapes of fin, the arrangements of tubes and the fin parameter mD. It is found that tube-to-tube conduction is significant when mD is small or the distance between neighboring tubes is small.

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TLM법을 이용한 프레넬 존 플레이트 렌즈 산란특성 해석 (Scattering characteristic analysis of Fresnel zone plate lens using TLM)

  • 김태용
    • 한국시뮬레이션학회:학술대회논문집
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    • 한국시뮬레이션학회 2003년도 춘계학술대회논문집
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    • pp.15-18
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    • 2003
  • 전자파 산란해석 방법으로서 유한요소법, 경계요소법 및 모멘트법 등은 임의 구조를 한 산란체의 산란현상을 다룰 수 있다. 그러나 이러한 해석방법들은 정상 파동문제를 다루는데 편중되어 있어 시간영역에서의 비정상 파동문제를 해석하기 위해서는 여러 가지 제약이 따른다. 본 논문에서는 본질적으로 시간영역 해석방법인 TLM(Transmission Line Matrix)법을 이용하여 프레넬 렌즈의 산란특성을 해석하고 키르호프의 근사식과 PO(Physical Optics)법과 비교 검토하여 그 유효성을 검증한다.

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면적가중 평균법과 그래프 해법에 의한 형태계수의 해석 (A solution method of view factor by the area weighted average and graphical methods)

  • 유승호;손장열
    • 설비공학논문집
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    • 제11권6호
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    • pp.709-715
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    • 1999
  • To optimize a heating and cooling system, we need an exact solution lot radiant heat transfer in any form of room or building. This paper describes the solution method of view factor by the area weighted average and graphical method to calculate the radiant heat exchange or daylighting level in any form of room or building. This study shows that the area weighted average and graphical methods have many points of merits(calculation speed, correctness and calculation capability in an arbitrary form of room shapes etc.) compared with existing methods

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궤도형상 데이터를 이용한 베어링 파라미터 규명 (Identification of parameter for Bearing Using Orbit Data)

  • 이경백;정찬범;김영배
    • 한국정밀공학회지
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    • 제20권3호
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    • pp.112-119
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    • 2003
  • This paper presents the identification of rotor dynamic parameters. The solution of the system equation can be obtained using least square method. The sensitivity analysis is performed to extract optimized solution, which is considered to be insensitive to inherent measurement errors. The cosine and sine term of orbit shapes can be obtain ed through the by experiment of the orbit analysis at a different speed after doing orbit analysis at an arbitrary selected speed. This values measured time domain are used to search the stiffness and damping coefficients of rotor bearing.

Flow Characteristics in Spin-Up of a Three-Layer Fluid

  • Sviridov Evgeny;Hyun Jae Min
    • Journal of Mechanical Science and Technology
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    • 제20권2호
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    • pp.271-277
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    • 2006
  • A numerical study is made of the spin-up from rest of a three-layer fluid in a closed, vertically-mounted cylinder. The densities in the upper layer $\rho_1$, middle layer $\rho_2$ and lower layer $\rho_3\;are\;\rho_3\;>\;\rho_2\;>\;\rho_1$, and the kinematic viscosities are left arbitrary. The representative system Ekman number is small. Numerical solutions are obtained to the time-dependent axisymmetric Navier-Stokes equations, and the treatment of the interfaces is modeled by use of the Height of Liquid method. Complete three-component velocity fields, together with the evolution of the interface deformations, are depicted. At small times, when the kinematic viscosity in the upper layer is smaller than in the middle layer, the top interface rises (sinks) in the central axis (peripheral) region. When the kinematic viscosity in the lower layer is smaller than in the middle layer, the bottom interface rises (sinks) in the periphery (axis) region. Detailed shapes of interfaces are illustrated for several cases of exemplary viscosity ratios.

급수 함수를 이용한 임의 형상 고정단 평판의 자유 진동 해석 (Free Vibration Analysis of Clamped Plates with Arbitrary Shapes Using Series Functions)

  • 강상욱
    • 한국소음진동공학회논문집
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    • 제17권6호
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    • pp.531-538
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    • 2007
  • A new method for free nitration analysis using series functions is proposed to obtain the eigenvalues of arbitrarily shaped, polygonal plates with clamped edges. Since a general solution used in the method satisfies the equation of motion for the transverse vibration of a plate, the method offers very accurate eigenvalues, compared to FEM or BEM results. In addition, the method can minimize the amount of numerical calculation because it has the advantage of not needing to divide the plate of interest. 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 (NASTRAN) or another analytical method.

Hydrodynamic Forces for Heaving Cylinders on Water of Finite Depth

  • J.H.,Hwang;K.P.,Rhee;Hisaaki,Maeda;Sumihiro,Eguchi
    • 대한조선학회지
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    • 제13권3호
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    • pp.1-9
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    • 1976
  • A numerical method for solving the boundary-value problem related to potential flows with a free surface and an experimental work are introduced in this paper. The forced heaving motion of cylinders with arbitrary shapes in water of finite depth are Considered here. The Fredholm integral equation of the first kind is employed in determining strengths of singularities distributed on the body surface. And the results obtained by the present method for the case of a heaving circular cylinder on water of finite depth agree well with existing results of earlier investigators.

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