• Title/Summary/Keyword: buoyancy method

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INCOMPRESSIBLE FLOW COMPUTATIONS BY HERMITE CUBIC, QUARTIC AND QUINTIC STREAM FUNCTIONS (Hermite 3차, 4차 및 5차 유동함수에 의한 비압축성 유동계산)

  • Kim, J.W.
    • 한국전산유체공학회:학술대회논문집
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    • 2009.11a
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    • pp.49-55
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    • 2009
  • This paper evaluates performances of a recently developed divergence-free finite element method based on Hermite interpolated stream functions. Velocity bases are derived from Hermite interpolated stream functions to form divergence-free basis functions. These velocity basis functions constitute a solenoidal function space, and the simple gradient of the Hermite functions constitute an irrotational function space. The incompressible Navier-Stokes equation is orthogonally decomposed into a solenoidal and an irrotational parts, and the decoupled Navier-Stokes equations are projected onto their corresponding spaces to form proper variational formulations. To access accuracy and convergence of the present algorithm, three test problems are selected. They are lid-driven cavity flow, flow over a backward-facing step and buoyancy-driven flow within a square enclosure. Hermite interpolation functions from cubic to quintic are chosen to run the test problems. Numerical results are shown. In all cases it has shown that the present method has performed well in accuracies and convergences. Moreover, the present method does not require an upwinding or a stabilized term.

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Behavior Analysis of a Tension Leg Platform in Current and Waves (조류와 파랑 중의 인장계류식 해양구조물의 거동해석)

  • Lee, S.C.;Park, C.H.;Bae, S.Y.;Goo, J.S.
    • Journal of Power System Engineering
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    • v.15 no.1
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    • pp.64-71
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    • 2011
  • The Tension Leg Platform(TLP) is restrained from oscillating vertically by tethers(or tendons), which are vertical anchor lines tensioned by the platform buoyancy larger than the platform weight. Thus a TLP is a compliant structure which allows lateral movements of surge, sway, and yaw but restrains heave, pitch, roll. In this paper, the motions of a TLP in current and waves were investigated. Hydrodynamic forces and wave exciting forces acting on the TLP were evaluated using the three dimensional source distribution method. The motion responses and tension variations of the TLP were analyzed in the case of including current or not including one in regular waves and effects of current on the TLP were investigated.

A Preliminary Study on the In-line Concentration Measurement of Absorbent Solution (흡수용액의 In-line 농도측정을 위한 기초연구)

  • 민병혁;황덕용;정시영;구기갑
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.2
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    • pp.152-158
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    • 2003
  • Titration method is one of the widely used methods for the concentration measurement of absorbent ammonia/water. However, this method is inconvenient because the solution should be extracted for the measurement. Moreover, significant error can be introduced by the evaporation of ammonia during the sampling and measuring procedure. In this study a reliable in-line concentration measurement method was proposed. To prove the validity of the concept, a measuring apparatus was designed, built, and tested with water. It is found that the location of flow inlet and exit is important in the measurement accuracy. The flow inlet and exit located in the middle of the test cell showed the best result. By the error analysis, it is expected that the ammonia concentration can be measured within the error of $\pm$0.18% assuming the error of 0.1 K in temperature measurement and 0.1 g in weight measurement.

Ship Frame Ring Analysis by a Matrix Method (매트릭스법(法)에 의한 선체근골환(船體筋骨環) 해석(解析))

  • S.J.,Yim
    • Bulletin of the Society of Naval Architects of Korea
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    • v.10 no.1
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    • pp.21-26
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    • 1973
  • A simple matrix method to analyze the ship's transverse frame ring is proposed. In this approach, the frame ring is treated as a plane frame of uniform slender members. The loadings on the frame consist of buoyancy loads, deck loads and cargo loads. The hatch coaming are considered to deflect under the loads. Because of symmetry, only the half of the frame is analyzed. The method is to obtain the forces and moments on each member. The deformation of the frame can be determined from the nodal displacements. For a sample calculation, a frame ring of a 10,000 ton class cargo liner is analyzed on the IBM 1130 computer. The numerical results obtained are proved to be resonable.

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Nonlinear Motion for an Elliptic Cylinder under Free Surface (자유표면 아래의 타원형 실린더에 대한 비선형 운동)

  • 이호영;임춘규
    • Journal of the Society of Naval Architects of Korea
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    • v.41 no.4
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    • pp.38-44
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    • 2004
  • The motion response analysis of a submerged elliptic cylinder in waves is presented and the elliptic cylinder is a simplification of the section of submarine in this paper. The method is based on boundary integral method and two-dimensional 3 degree motions are calculated in regular harmonic waves. The fully nonlinear free surface boundary condition is assumed in an numerical domain and this solution is matched along an assumed boundary as a linear solution composed of transient Green function, The large amplitude motions of an elliptic cylinder are directly simulated and effects of wave frequency, wave amplitude and the distance from buoyancy center to gravity center are discussed.

An Evaluation of a Direct Numerical Simulation for Counterflow Diffusion Flames (대향류 확산화염에 대한 직접수치모사의 검증)

  • 박외철
    • Journal of the Korean Society of Safety
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    • v.16 no.4
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    • pp.74-81
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    • 2001
  • A direct numerical simulation (DNS) was applied to nonpremixed counter-flow diffusion flames between oxidizer and fuel ducts. The objective of this study is to evaluate the numerical method for simulation of axisymmetric counterflow diffusion flames. Effects of computational domain size and grid size were scrutinized, and then the method was applied to air-methane diffusion flames. The results at zero gravity conditions were in good agreement with those obtained by the one-dimension flame code OPPDIF. It was confirmed thai the numerical method is applicable to the diffusion flames at the normal gravity conditions since the results clearly showed the effects of buoyancy and velocity ratio.

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Characteristics of an Entrainment into the Turbulent Buoyant Jet in a Cross Flow (직교류에서 난류제트로 유입되는 유량에 관한 고찰)

  • Kim, Hyung Min;Kim, Eunpil
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.23 no.3
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    • pp.342-351
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    • 1999
  • A jet injected normally into a cross flow has been found to have the cross section of a horseshoe shape. It occurs by a twin vortex motion in the region downstream of the jet injection. Such a flow is inherently and highly three-dimensional and numerical calculations should play an important role. The three-dimensional momentum equations with buoyancy effect and energy equation are solved to obtain the velocity distributions, center-line trajectories, cross sectional shape and entrainment. The density difference is sufficiently small, so that the Boussinesq approximation is considered to be valid. The SIMPLE algorithm is applied in a staggered grid system of a calculational domain for the numerical method.

Free Vibrations of Ocean Cables under Currents (조류력을 받는 해양케이블의 자유진동해석)

  • 김문영;김남일;윤종윤
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.11 no.4
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    • pp.231-237
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    • 1999
  • A geometric non-linear finite element formulation of spatial ocean cable under currents is presented using multiple noded curved cable elements. Tangent stiffness and mass matrices for the isoparametric cable ele¬ment are derived and the initial equilibrium state of ocean cable subjected to self-weights, buoyancy, and current as well as support motions is determined using the load incremental method. Free vibration analysis of ocean cables is performed based on the initial equilibrium configuration. Numerical examples are presented and discussed in order to demonstrate the feasibility of the present finite element method and investigate dynamic characteristics of ocean cables.

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Independence of SCI patients after HALLIWICK hydrotherapy method - A Case report - (수중치료후 척수손상 환자의 독립 - 증례 보고 -)

  • Kim, Chi-Hyok;Kim, Yong-Kwon
    • Journal of Korean Physical Therapy Science
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    • v.6 no.4
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    • pp.241-249
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    • 1999
  • One of the major purpose of rehabilitation program is for the individual to achieve independence. That means independence from family members, independence from friends, and independence from rehabilitation team. An independent attitude is essential for autonomous functioning. Unless a disabled person is motivated to function independently, he will never do so. 3) Hydrotherapy, HALLIWICK method was applied to SCI patient. Especially, metacentric effect, density, buoyancy and breathing control are very very important theory.

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Evaluation of Navigational Safety Using the Integrated Seakeeping Performance Index under Loading Conditions of a Ship (선박의 적화 상태별 종합내항성능지표에 의한 항해 안전성 평가)

  • 김순갑;김정만;공길영
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.4 no.2
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    • pp.43-52
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    • 1998
  • Generally, the navigational safety of a ship under various loading conditions is evaluated by a loading manual. However, the loading manual handles only statical factors such as weight and buoyancy of ship without including any wave conditions. Practically ship's safety is much concerned with the occurrences on the rough sea as propeller racing, rolling, deck wetness, vertical acceleration, lateral acceleration, slamming and so on. The purpose of this paper is to present a synthetic and practical evaluation method of navigational safety using the integrated seakeeping performance index(ISPI) under loading conditions of ship in seaways. The method is calculated by means of the ISPI by measuring only vertical acceleration. Judgement of dangerousness is carried out for four lading conditions : homogeneous full loaded, half loaded, heavy ballast loaded, and normal ballast loaded conditions. In developing the practical evaluation system of navigational safety, it is useful to solve the difficulties in measuring factors by sensors. And by applying the evaluation diagrames, navigators are able to avoid dangerousness by keeping away of the danger encountering angle of wave direction which the diagram shows.

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