Doyub Kim

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A Practical Simulation of Dispersed Bubble Flow by doyub (8) 2010/05/06
Stretching and Wiggling Liquids by doyub (2) 2009/09/08
A Semi-Lagrangian CIP Fluid Solver without Dimensional Splitting by doyub 2008/01/25
Derivative Particles for Simulating Detailed Movements of Fluids by doyub 2007/03/09



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A Practical Simulation of Dispersed Bubble Flow


A Practical Simulation of Dispersed Bubble Flow

Doyub Kim, Oh-young Song, and Hyeong-Seok Ko

Seoul National University
Sejong University
 

ACM Transactions on Graphics (Proc. SIGGRAPH 2010), to appear.

In this paper, we propose a simple and efficient framework for simulating dispersed bubble flow. Instead of modeling the complex hydrodynamics of numerous small bubbles explicitly, our method approximates the average motion of these bubbles using a continuum multiphase solver. Then, the subgrid interactions among bubbles are computed using our new stochastic solver. Using the proposed scheme, we can efficiently simulate complex scenes with millions of bubbles.



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Stretching and Wiggling Liquids


Stretching and Wiggling Liquids

Doyub Kim, Oh-young Song, and Hyeong-Seok Ko

Seoul National University
Sejong University
 

ACM Transactions on Graphics (Proc. SIGGRAPH Asia 2009) Vol. 28, No. 5, 120.

This paper presents a novel framework for simulating the stretching and wiggling of liquids. We demonstrate that complex phase-interface dynamics can be effectively simulated by introducing the Eulerian vortex sheet method, which focuses on the vorticity at the interface (rather than the whole domain). We extend this model to provide user control for the production of visual effects. Then, the generated fluid flow creates complex surface details, such as thin and wiggling fluid sheets. To capture such high-frequency features efficiently, this work employs a denser grid for surface tracking in addition to the (coarser) simulation grid. In this context, the paper proposes a filter, called the liquid-biased filter, which is able to downsample the surface in the high-resolution grid into the coarse grid without unrealistic volume loss resulting from aliasing error. The proposed method, which runs on a single PC, realistically reproduces complex fluid scenes.



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A Semi-Lagrangian CIP Fluid Solver without Dimensional Splitting


A Semi-Lagrangian CIP Fluid Solver without Dimensional Splitting

Doyub Kim, Oh-young Song, and Hyeong-Seok Ko

Seoul National University
Sejong University
 

Computer Graphics Forum (Proc. Eurographics), April 2008 (Vol. 27, No. 2) pp. 467-475.

In this paper, we propose a new constrained interpolation profile (CIP) method that is stable and accurate but requires less amount of computation compared to existing CIP-based solvers. CIP is a high-order fluid advection solver that can reproduce rich details of fluids. It has third-order accuracy but its computation is performed over a compact stencil. These advantageous features of CIP are, however, diluted by the following two shortcomings: (1) CIP contains a defect in the utilization of the grid data, which makes the method suitable only for simulations with a tight CFL restriction; and (2) CIP does not guarantee unconditional stability. There have been several attempts to fix these problems in CIP, but they have been only partially successful. The solutions that fixed both problems ended up introducing other undesirable features, namely increased computation time and/or reduced accuracy. This paper proposes a novel modification of the original CIP method that fixes all of the above problems without increasing the computational load or reducing the accuracy. Both quantitative and visual experiments were performed to test the performance of the new CIP in comparison to existing fluid solvers. The results show that the proposed method brings significant improvements in both accuracy and speed.





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Derivative Particles for Simulating Detailed Movements of Fluids


Derivative Particles for Simulating Detailed Movements of Fluids

Oh-young Song Doyub Kim, and Hyeong-Seok Ko

Sejong University
Seoul National University
 

IEEE Transactions on Visualization and Computer Graphics, July/August 2007 (Vol. 13, No. 4) pp. 711-719.

We present a new fluid simulation technique that significantly reduces the non-physical dissipation of velocity. The proposed method is based on an apt use of particles and derivative information. We note that a major source of numerical dissipation in the conventional Navier--Stokes equations solver lies in the advection step. Hence, starting with the conventional grid-based simulator, when the details of fluid movements need to be simulated, we replace the advection part with a particle simulator. When swapping between the grid-based and particle-based simulators, the physical quantities such as the level set and velocity must be converted. For this purpose, we develop a novel dissipation-suppressing conversion procedure that utilizes the derivative information stored in the particles as well as in the grid points. For the fluid regions where such details are not needed, the advection is simulated using an octree-based constrained interpolation profile (CIP) solver, which we develop in this work. Through several experiments, we show that the proposed technique can reproduce the detailed movements of high-Reynolds-number fluids, such as droplets/bubbles, thin water sheets, and whirlpools. The increased accuracy in the advection, which forms the basis of the proposed technique, can also be used to produce better results in larger scale fluid simulations.





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