• 제목, 요약, 키워드: RANS equation

검색결과 112건 처리시간 0.039초

RANS 방정식의 운동량 원천항을 이용한 내부조파 (Internal Wave-Maker using Momentum Source Term of RANS Equation Model)

  • 최준우;고광오;윤성범
    • 한국해안·해양공학회논문집
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    • v.21 no.2
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    • pp.182-190
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    • 2009
  • Lin and Liu(1999)는 VOF기법을 도입한 RANS 방정식 모형을 이용하여 목표 파형을 조파할 수 있도록 연속방정식의 질량 원천항을 이용하는 내부조파기법을 제안하였다. 이로부터 외부조파에 의한 영역 내 재반사 문제가 해결되어 RANS 방정식 모형을 이용한 파랑수치실험이 수행되어 발표되어 왔다. 본 연구에서는 RANS 방정식 모형의 운동량 원천항을 이용한 내부조파기법을 사용하여 목표 파형을 조파할 수 있도록 하였다. FLUENT의 사용자 정의함수를 이용하여 두 조파방법에 대해 수치실험하고 비교하였다. 그리고 조파기법의 적용성을 살펴 보기 위해 Luth et al.(1994)의 수리실험을 수치모의하고 그 결과를 비교하였으며, 수심방향 변화를 보이는 수치 모의 결과들을 제시하고 고찰하였다.

채널난류유동에 대한 하이브리드 RANS/LES 방법 (Hybrid RANS/LES Method for Turbulent Channel Flow)

  • 명현국
    • 대한기계학회논문집B
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    • v.26 no.8
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    • pp.1088-1094
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    • 2002
  • A channel flow with a high Reynolds number but coarse grids is numerically studied to investigate the prediction possibility of its turbulence which is three-dimensional and time-dependent. In the present paper, a Reynolds-Averaged Navier-Stokes (RANS) model, a Large Eddy Simulation (LES) and a Navier-Stokes equation with no model are tested with a new approach of hybrid RANS/LES, which reduces to RANS model in the boundary layers and at separation, and to Smagorinsky-like LES downstream of separation, and then compared with each other. It is found that the simulations of hybrid RANS/LES method sustain turbulence like those of LES and with no model, and the results are stable and fairly accurate. This indicates strongly that gradual improvements could lead to a simple, stable, and accurate approach to predict turbulence phenomena of wall-bounded flow.

다공성 벽면(porous-wall)과 거칠기가 있는 벽면(rough-wall)에 관한 경계조건을 이용한 초음속 흐름의 수치모사 (NUMERICAL SIMULATIONS OF SUPERSONIC FLOWS USING POROUS AND ROUGH WALL BOUNDARY CONDITIONS)

  • 곽인근;유일용;이동훈;이승수
    • 한국전산유체공학회지
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    • v.14 no.4
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    • pp.23-30
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    • 2009
  • The existing code which solves two-dimensional RANS(Reynolds Averaged Navier-Stokes) equations and 2-equation turbulence model equations was modified to enable numerical simulation of various supersonic flows. For this, various boundary conditions have been implemented to the code. Bleed boundary condition was incorporated into the code for calculating wall mean flow quantities. Furthermore, boundary conditions for the turbulence quantities along rough surfaces as well as porous walls were applied to the code. The code was verified and validated by comparing the computational results against the experimental data for the supersonic flows over bleed region on a flat plate. Furthermore, numerical simulations for supersonic shock boundary layer interaction with a bleed region were performed and their results were compared with the existing computational results.

다공성 벽면(porous-wall)과 거칠기가 있는 벽면(rough-wall)에 과한 경계조건을 이용한 초음속 흐름의 수치모사 (NUMERICAL SIMULATION OF SUPERSONIC FLOW USING POROUS AND ROUGH WALL BOUNDARY CONDITIONS)

  • 곽인근;유일용;이승수
    • 한국전산유체공학회:학술대회논문집
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    • pp.104-111
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    • 2009
  • The existing code which solves two-dimensional RANS(Reynolds Averaged Navier-Stokes) equations and 2-equation turbulence model equations was modified to enable numerical simulation of various supersonic flows. For this, various boundary conditions have been implemented to the code. Bleed boundary condition was incorporated into the code for calculating wall mean flow quantities. Furthermore, the boundary conditions for the turbulence quantities along rough surfaces as well as porous walls were applied to the code. The code was verified and validated by comparing the computational results against the experimental data for the supersonic flows over bleed region on a flat plate. Using the newly modified code, numerical simulations were performed and compared with other computational results as well as the experimental data for the supersonic flows over an oblique shock with a bleed region.

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수치해를 이용한 선박의 점성저항 해석 (Visous resistance analysis of a ship using numerical solutions)

  • 곽영기
    • 한국해양공학회지
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    • v.11 no.2
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    • pp.100-106
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    • 1997
  • Viscous flow around an actual ship is calculated by an use of RANS(Reynolds-averaged Navier-Stokes) solver. Reynolds stress is modelled by using k-$\varepsilon$ turbulence model and the law of wall is applied near the body. Body fitted coordinates are introduced for the treatment of the complex boundary of the ship hull form. The transformed equations in the computational domain are numerically solved by an employment of FVM(Finite Volume Method). SIMPLE(Semi-Implcit Pressure Linked Equation) method is adopted in the calculation of pressure and the solution of the disssssssscretized equation is obtained by the line-by-line method with the use of TDMA(Tri-Diagonal Matrix Algorithme). The subject ship model of actual calculation is 4,410 TEU class container carrier. For 4 geosim models the calculated viscous resistancce values are compared with the model test results and analyzed on their componentss. The resistance performance of an actual ship is predicted very resonably, so this mothod may be utilized as a design tool of hull form.

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HSVA 두 탱커 선형에 대한 점성유동 계산 (Numerical Calculation of Viscous Flows for Two HSVA Tankers)

  • 곽영기
    • 한국해양공학회지
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    • v.13 no.2
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    • pp.138-146
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    • 1999
  • The viscous flow around a ship hull is calculated by the use of RANS(Reynolds-averaged Navier-Stokes) solver. Reynolds stresses are midelled by using the k-${epsilon}$ turbulence model and the law is applied near the body. Body fitted corrdinates are introduced for the treatment of the complex boundary of the ship hull form and the governing equations in the physical domain transformed into ones in the computational domain. The transformed equations are numerically solved by an employment of FVM(Finite Volume Method). SIMPLE(Semi-Implicit Pressure Linked Equation) method is adopted in the calculation of pressure and the solution of the sidcretized equation is obtained by the line-by-line method with the use of TDMA(Tri-Diagonal Matrix Algorithme). To assure the proprietty of this computing method, HSVA tanker and Dyne hull are calculated ar both model and ship scale Reynolds number. Their reaults of pressure distributions on fore and aft body, axial velocity contours and transverse velocity velocity vectors and viscous resistance coefficients are compared with other's experiments and calculations.

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Hybrid RANS/LES 방법을 이용한 이음속 공동 유동의 수치적 모사 (Hybrid RANS/LES Simulation of Subsonic Cavity Flow)

  • 장경식;박승오;최석기
    • 한국전산유체공학회지
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    • v.9 no.2
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    • pp.23-29
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    • 2004
  • A numerical simulation of an incompressible cavity flow is conducted using the hybrid turbulence model. The model adopted is a modified type of DES using k- ε two-equation model. Cavity geometry and flow condition are based on Cattafesta's experiment. Computational results are compared with the results of Cattafesta's experiment. The simulation successfully predicts the oscillatory features and the Strouhal number of the oscillation compares very favorably with that of the dominant mode of experimental data. Vorticity contours obtained from the simulation data are consistent with the smoke visualization of the Cattafesta's experiment. The coherent structures of cavity flow are also investigated using Q criterion.

초음속 흡입구 유동의 수치모사 (Numerical Simulation of Supersonic Inlet Flow)

  • 곽인근;유일용;이승수;정석영
    • 한국추진공학회:학술대회논문집
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    • pp.133-137
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    • 2009
  • Bleed 영역이 있는 흡입구 주위의 초음속 유동에 대한 수치 모사를 수행하였다. 이를 위하여 RANS(Reynolds Averaged Navier-Stokes) 방정식과 2-방정식 난류 모델 방정식을 기반으로 한 기존의 코드를 축대칭형으로 변환하고 bleed 경계 조건을 적용하였다. 본 논문에서는 개발한 코드를 검증하기 위해 범프(bump)와 경사충격파와 bleed 영역이 있는 평판 주위에서의 흐름에 대해 실험치 및 타 수치 해석 결과와 비교하였다. 개발한 코드를 이용하여 bleed 장치가 장착된 축대칭 초음속 흡입구 주변의 유동에 대한 수치 모사를 수행하였다.

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DES 기법을 이용한 270°곡덕트에서 발달하는 난류 유동의 수치해석 (Detached Eddy Simulation of a Developing Turbulent Flow in a 270° Curved Duct)

  • 서정식;신종근;최영돈;이주철
    • 대한기계학회논문집B
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    • v.32 no.6
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    • pp.471-478
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    • 2008
  • Detached Eddy Simulation (DES) is performed for developing turbulent flow of the $270^{\circ}$ curved duct at a Reynolds number of 56,690. The curvature ratio on the basis of a centric radius $R_c$ and a duct height H is 3.357. Turbulence models adopted are k-$\omega$ model for Reynolds Average Navier-Stokes (RANS) equation Simulation and Shear Stress Transport (SST) model for DES. DES is used as the hybrid computation technique combined with RANS-SST and Large Eddy Simulation (LES). Predicted results are compared with measured results including the distributions of Reynolds stresses and the flow characteristics on the symmetric plane of curved duct are presented. Judging from the comparison between the predicted and the measured results, the DES approach is applicable to calculate the developing turbulent flow in a $270^{\circ}$ curved duct.