• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.112-115
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• 2009

In this paper, flow simulation algorithms for utilizing unstructured hybrid meshes are introduced. First, various types of meshes are introduced. Advantages and disadvantages of each type of meshes are discussed. Unstructured hybrid mesh approach, that is best suited for high speed viscous flow simulation, is presented. Lastly, various types of flow simulations using unstructured hybrid meshes are introduced.

• 한국전산유체공학회지
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• 제11권4호
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• pp.75-80
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• 2006

Navier-Stokes simulation of the flow in a micro viscous pump is carried out. The micro viscous pump consists of a rotating circular rotor placed in a two dimensional channel. All simulation is carried out by using a finite volume approach, at the Reynolds number of 0.5, to study the performance of the micro viscous pump. Length of channel of the pump is varied to simulate the effects of the pumping load. Numerical solutions show that the net flow of the pump is realized by two counter rotating vortices formed on both sides of the rotor. The volume flow rate of the pump is decreased as length of the channel is increased, while the static pressure difference across the rotor is increased. The static pressure difference across the rotor is observed to be inversely proportional to the volume flow rate as inertia effects are negligibly small. The efficiency of the pump is found to reach a maximum when two counter rotating vortices on both sides of the rotor becomes to merge forming an outer enveloping vortex.

• 한국전산유체공학회지
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• 제11권2호
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• pp.1-7
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• 2006

An unstructured overset mesh method has been developed for the simulation of unsteady viscous flow fields around multiple bodies in relative motion. For this purpose, a robust and fast search technique is proposed for both triangle and high-aspect ratio quadrilateral cell elements. The interpolation boundary is defined for data communication between grid systems and an interpolation method is suggested for viscous and inviscid cell elements. This method has been applied to calculate the flow fields around 2-D airfoils involving relative motion. Validations were made by comparing the predicted results with those of experiments or other numerical results. It was demonstrated that the present method is efficient and robust for the prediction of unsteady time-accurate flow fields involving multiple bodies in relative motion.

• 한국가시화정보학회지
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• 제18권3호
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• pp.109-115
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• 2020

Five layers in mean flow are proposed by using the direct numerical simulation data of turbulent pipe flow up to Reτ = 3008. Viscous sublayer, buffer layer, mesolayer, log layer and core region are investigated. In the buffer layer, the viscous force is counterbalanced by the turbulent inertia from the streamwise mean momentum balance, and a log law occurs here. The overlap layer is composed of the mesolayer and the log layer. Above the buffer layer, the non-negligible viscous force causes the power law, and this region is the mesolayer, where it is the lower part of the overlap layer. At the upper part of the overlap layer, where the viscous force itself becomes naturally negligible, the log layer will appear due to that the acceleration force of the large-scale motions increases as the Reynolds number increases. In the core region, the velocity-defect form is satisfied with the power-law scaling.

• 한국전산유체공학회지
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• 제13권3호
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• pp.35-43
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• 2008

A methodology for the simulation of compressible high Reynolds number flow over rigid and moving bodies on a structured Cartesian grid is described in this paper. The approach is based on a modified version of the Brinkman Penalization method. To avoid oscillations in the vicinity of the body and to simulate shcok-containing flows, a Weighted Essentially Non-Oscillatory scheme is used to discretize the spatial flux derivatives. For high Reynolds number viscous flow, two turbulence models of the two-equation Menter's SST URANS model and a two-equation Detached Eddy Simulation are implemented. Some simple flow examples are given to assess the accuracy of the technique. Finally, a moving grid capability is demonstrated.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 추계 학술대회논문집
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• pp.200-208
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• 2007

A methodology for the simulation of compressible high Reynolds number flow over rigid and moving bodies on a structured Cartesian grid is described in this paper. The approach is based on a modified version of the Brinkman Penalization method. To avoid oscillations in the vicinity of the body and to simulate shcok-containing flows, a Weighted Essentially Non-Oscillatory scheme is used to discretize the spatial flux derivatives. For high Reynolds number viscous flow, two turbulence models of the two-equation Menter's SST URANS model and a two-equation Detached Eddy Simulation are implemented. Some simple flow examples are given to assess the accuracy of the technique. Finally, a moving grid capability is demonstrated.

• 한국전산유체공학회지
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• 제16권1호
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• pp.90-95
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• 2011

The Navier-Stokes equations are solved to study the flow characteristics of a micro viscous pump. The viscous micropump is consisted of a stationary disk with a spiral shaped channel and a rotating disk. A simple geometrical model for the tip clearance is proposed and validated by comparing computed flow rate with corresponding experimental data. Present numerical solutions show satisfactory agreement with the corresponding experimental data. The tip clearance effect is found to become significant as the rotational speed increases. As the pressure load increases, a reversed flow region is seen to form near the stationary disk. The height of the channel is shown to be optimized in terms of the flow rate for a given rotational speed and pressure load. The optimal height of the channel becomes small as the rotational speed decreases or the pressure load increases. The flow rate of the pump is found to be in proportion to the width of channel.

• 한국컴퓨터그래픽스학회논문지
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• 제26권5호
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• pp.1-13
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• 2020

본 논문에서는 흐르는 물에 의해 빙결 시뮬레이션 되어 방향성이 있는 얼음 형태를 안정적으로 모델링 할 수 있는 새로운 방법을 제시한다. 제안하는 얼음 모델링 프레임워크는 빙결 시뮬레이션에서 중요한 얼음의 성장 방향에 점성이 있는 유체의 흐름을 고려한다. 물 시뮬레이션 해법은 암시적 비압축성 유체 시뮬레이션에 새로운 점성 기법을 적용한 방법을 이용하고, 얼음의 방향과 글레이즈(Glaze) 효과는 제안하는 비등방성한 빙결 해법을 이용한다. 물 입자가 얼음 입자로 상태변화하는 조건은 습도와 물의 흐름에 따른 새로운 에너지 함수에 따라 계산된다. 습도는 오브젝트 표면의 가상 수막(Virtual water film)으로 근사되며, 유체의 흐름은 얼음의 성장 방향을 가이드하기 위해 우리의 비등방성한 빙결 해법에 통합된다. 결과적으로 점성이 있는 물의 흐름 방향에 따라 글레이즈와 방향성 있는 빙결 시뮬레이션 결과를 안정적으로 보여준다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.212-216
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• 2002

평행한 벽 내부의 흐르는 규제 속에 원형실린더를 놓고 운동장 해석을 수행하였다. 비압축성 Navier- Stokes 방정식을 풀었고 3차 풍상미분의 수치해법을 이용하였다. 채널 내부에서 실린더의 위치를 이동하면서 벽면의 효과 전단력, 와류의 현장을 규명하였다. 수치처리는 Marker & Cell 기법에 의한 유한차분법을 사용하였다. 본 연구를 통하여 실린더와 벽 경계 사이에서의 생성된 와가 박리 전단에 영향을 미치는 것을 알 수 있었다.

• 한국해양공학회지
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• 제18권2호
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• pp.1-9
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• 2004

As the first step to investigate the nonlinear interactions between turbulence and marine structures inside a viscous NWT, a LES technique was applied to solve the turbulent channel flow for =150. The employed turbulence models included 4 types: the Smagorinsky model, the Dynamic SGS model, the Structure Function model, and the Generalized Normal Stress model. The simulated data in time-series for the LESs were averaged in both time and space, and statistical analyses were performed. The results of the LESs were compared with those of a DNS, developed in the present study and two spectral methods by Yoon et al.(2003) and Kim et a1.(1987). Based on this research, the accuracy of LESs has been found to be still related to the number of grids for fine grid size).