• Journal of the Korean Society of Propulsion Engineers
• /
• v.21 no.3
• /
• pp.61-67
• /
• 2017

In this study, Burning Area Analysis Program (BAAP) was developed by using VOF method to estimate the burning area of 3D shaped grain. The parametric study of mesh size, burning rate and time interval for numerical calculation was conducted. The result of BAAP is compared with the one from commercial 3D modeling software. Also the internal ballistic analysis was performed using the result of BAAP. In order to estimate the burning area and internal pressure with time, Chemical Equilibrium Analysis (CEA) was conducted with a composition of reduced smoke propellant. As a result, the web-averaged pressure was 5.34 MPa which is similar to the published research result.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.14 no.2
• /
• pp.171-181
• /
• 2002

Among various numerical methods of wave transformations including wave breaking by structure, models using VOF(Volume Of Fluid) method to trace free surface are getting into the spotlight recently. In order to analyze wave transformations and velocity of the wave fields due to the permeable submerged breakwater(PSB), This study applied VOF method to the two-dimensional wave channel installed line-source to generate waves and added dissipation zone to offer a non-reflective boundary. Hydraulic experiments was performed to obtain the application of two-dimensional numerical wave channel. The results of numerical experiments using the two-dimensional wave channel agree well with the experimental data. It was shown that vortices are formed behind the PSB, and in case of the 2-rowed PSB they also are occurred in between PSBs, strongly non-linear waves are developed on the crown of the PSB, and the direction of velocities in porous media is determined by the shape of free surface.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.26 no.5
• /
• pp.35-43
• /
• 2022

Precise modeling and analysis of closed bomb test(CBT) combustion using solid propellants was performed. The fluid structure interaction(FSI) method was implemented to analyze the gas and solid phases at the same time. The Eulerian analysis method was applied for the gas phase and grain combustion, and the Lagrangian analysis method was implemented for the grain movement. The interaction between the solid phase grains and the combustion gas was fully coupled through the source term. The volume of fluid(VOF) method was used to simulate the burning distance of the grain and the movement of the combustion surface. The force acting on the grain was comprised of the pressure and gravity acting on the grain burning surface, and the grain burning rate and grain movement speed were considered in the velocity term of the VOF. The combustion analysis was performed for both one and three grains, and fairly compared with the experiments. The acoustic field during grain combustion due to pressure fluctuations was also analyzed.

• Journal of Korea Water Resources Association
• /
• v.37 no.11
• /
• pp.949-958
• /
• 2004

A combined experimental and numerical effort is presented for investigation of reflection of irregular waves due to rectangular submerged breakwaters. In the numerical model, the Reynolds equations are solved by a finite difference method and k-$\varepsilon$ model is employed for the turbulence analysis. To track the free surface displacement, the volume of fluid method is employed. Numerical predictions of transmission and reflection coefficients are verified by comparing to laboratory measurements. Very reasonable agreements are observed. The reflection coefficients become stronger in proportion to numbers of submerged breakwaters.

• Journal of computational fluids engineering
• /
• v.20 no.4
• /
• pp.1-6
• /
• 2015

Centrifugal pumps consume considerable amount of energy in various industrial applications. Therefore, improvement of the efficiency of these machines has become a major challenge. Cavitation is a phenomenon which decreases the pump efficiency and even causes structural demage. Hence, the goal of this paper is to investigate the cavitation problem in the single-stage and double-stage centrifugal pumps. The Volume of Fraction (VOF) method has been used for the numerical simulations together with Rayliegh-Plesset model for the gas-liquid two-phase flow inside the pump. In order to capture the turbulent phenomena, the standard k-${\varepsilon}$ turbulence model has been adopted, and the simulations have been done as unsteady cases. In addition, the motion of the rotating parts has been simulated using Multi Reference Frame(MRF) method. The results are presented and compared in terms of hydraulic head and NPSH for both the single-stage and double-stage pumps. The H-Q curves show the effects of cavitation on decreasing the pumps performances.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2007.05a
• /
• pp.2094-2097
• /
• 2007

본 연구에서는 사석경사제의 전면부에 불투과성 수중방파제를 설치하여, 불규칙파의 반사에 대한 수치모의와 수리모형실험을 수행하였다. 수치해석 모형에는 Reynolds Averaged Navier-stokes (RANS) 방정식을 지배방정식으로 사용하였고, 난류해석을 위하여 $\kappa-\varepsilon$ 방정식을 사용하였다. 자유수면변위의 정확한 예측을 위하여 VOF 기법을 적용하였다. 수리모형실험은 한양대학교 수리실험실의 조파수로에서 수행되었다. 본 연구에서는 입사파랑으로 불규칙파를 조파하였으며, Bretsch neider-Mistuyasu 스펙트럼을 목표스펙트럼으로 하여 재현하였다. 반사율의 산정에서 입사파와 반사파를 분리하기 위하여 수치모형실험에서는 3점법을 사용하였고, 수리모형실험에서는 2점법을 사용하였다. 수치모의를 통하여 예측된 반사율과 수리모형실험에서 관측한 결과는 서로 잘 일치하였다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2012.05a
• /
• pp.181-184
• /
• 2012

기존에 제시된 Lin 과 Liu (1999)의 VOF 기법을 이용한 내부 조파 방법을 레블셋 기법에 적용하였다. 기하학적으로 유리한 유한요소법을 이용하여, Navier-Stokes 방정식의 공간차분에는 Characteristic Galerkin 기법을, 시간차분에는 Fractional Four-Step 기법을 적용하였다. 그림에 보인 바와 같이 중심(x=0)에서 전파하는 경우, 외부조파에 의한 영역내 재반사 문제가 해결되어 선형파를 의도한 바대로 잘 조파할 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.12
• /
• pp.1570-1579
• /
• 2000

Finite element analysis of fluid flow with moving free surface has been carried out in two and tree dimensions. The new VOF-based numerical algorithm that has been proposed by the present authors was applied to several 2-D and 3-D free surface flow problems. The proposed free surface tracking scheme is based on two numerical tools that have been newly introduced by the present authots; the orientation vector to represent the free surface orientation in each cell and the baby-cell to determine the fluid volume flux at each cell boundary. The proposed numerical algorithm has been applied to 2-D and 3-D cavity filling and sloshing problems, which demonstrated versatility and effectiveness of the new free surface tracking scheme as well as the overall solution procedure. The proposed numerical algorithm resolved successfully the interacting free surface with each other. The simulated results demonstrated the applicability of proposed numerical algorithm to the practical problems of large free surface motion. Also, it has been demonstrated that the proposed free surface tracking scheme can be easily implemented in any irregular non-uniform grid systems and can be extended to the 3-D free surface flow problem without additional efforts.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.12
• /
• pp.1555-1569
• /
• 2000

Numerical simulation of fluid flow with moving free surface has been carried out. For the free surface flow, a VOF(Volume of Fluid)-based algorithm utilizing a fixed grid system has been investigated. In order to reduce numerical smearing at the free surface represented on a fixed grid system, a new free surface tracking algorithm based on the donor-acceptor scheme has been presented. Novel features of the proposed algorithm are characterized as two numerical tools; the orientation vector to represent the free surface orientation in each cell and the baby-cell to determine the fluid volume flux at each cell boundary. The proposed algorithm can be easily implemented in any irregular non-uniform grid systems that are usual in finite element method (FEM). Moreover, the proposed algorithm can be extended and applied to the 3-D free surface flow problem without additional efforts. For computation of unsteady incompressible flow, a finite element approximation based on the explicit fractional step method has been adopted. In addition, the SUPG(streamline upwind/Petrov-Galerkin) method has been implemented to deal with convection dominated flows. Combination of the proposed free surface tracking scheme and explicit fractional step formulation resulted in an efficient solution algorithm. Validity of the present solution algorithm was demonstrated from its application to the broken dam and the solitary wave propagation problems.

• Proceedings of the Korea Contents Association Conference
• /
• 2012.05a
• /
• pp.143-144
• /
• 2012

전통적인 VOF 기법을 이용한 내부 조파 방법을 레블셋 기법에 적용하였다. 기하학적으로 유리한 유한요소법을 이용하여, Navier-Stokes 방정식의 공간차분에는 Characteristic Galerkin 기법을, 시간차분에는 Fractional Four-step 기법을 적용하였다. 중심(x=0)에서 전파하는 경우, 외부조파에 의한 영역내 재반사 문제가 해결되어 선형파를 의도한 바대로 잘 조파할 수 있었다.