• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 춘계 학술대회논문집
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• pp.153-158
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• 2007

Since the introduction of Nanoimprint in the mid-1990s, Nanoimprint lithography, a low-cost, non-convential method, has been the dominant lithography technology that guarantees high-throughput patterning of nanostructures. Based on the mechanical embossing mechanism, Nanoimprint lithography creates the nanopatterns on the polymer material cast on the substrate. In essence, the process needs nanofabrication equipment for printing with the adequate control of temperature, pressure and control of parallels of the stamp and substrate. This article introduce the possibility and reality of the thermal control on the hot plate using a CFD code. Numerical computation has been conducted for assessing the feasibility of a hot plate($120{\times}120\;mm2$). PID control is adopted to ensure high temperature uniformity in several zones. Parallel experiments have also been performed for verifying thermal performance. Not only show the results the optimum number of thermocouples related to controllers but also suggest that the thermal simulation using a CFD code would be an alternative method to design and develop the thermal control equipment in the financial aspect.

• 대한기계학회논문집B
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• 제40권9호
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• pp.597-604
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• 2016

본 연구에서는 GPU를 이용한 비압축성 유동장의 병렬연산을 위하여, P2P1 유한요소를 이용한 분리 알고리즘 내의 행렬 해법인 이중공액구배법(Bi-Conjugate Gradient)의 CUDA 기반 알고리즘을 개발하였다. 개발된 알고리즘을 이용해 비대칭 협착관 유동을 해석하고, 단일 CPU와의 계산시간을 비교하여 GPU 병렬 연산의 성능 향상을 측정하였다. 또한, 비대칭 협착관 유동 문제와 다른 행렬 패턴을 가지는 유체구조 상호작용 문제에 대하여 이중공액구배법 내의 희소 행렬과 벡터의 곱에 대한 GPU의 병렬성능을 확인하였다. 개발된 코드는 희소 행렬의 1개의 행과 벡터의 내적을 병렬 연산하는 커널(Kernel)로 구성되며, 최적화는 병렬 감소 연산(Parallel Reduction), 메모리 코얼레싱(Coalescing) 효과를 이용하여 구현하였다. 또한, 커널 생성 시 워프(Warp)의 크기에 따른 성능 차이를 확인하였다. 표준예제들에 대한 GPU 병렬연산속도는 CPU 대비 약 7배 이상 향상됨을 확인하였다.

• 한국전산유체공학회지
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• 제17권2호
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• pp.78-84
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• 2012

Numerical calculations were performed to investigate the influence in aerodynamic characteristics of a rotor system by surrounding structures and the ground effect for the rotor blade on a whirl tower is also investigated. Three dimensional Navier-Stokes simulations were carried out by using unstructured overset mesh technique and parallel computation. The calculated hover performance showed good agreement with the experimental result and showed that the structures around the whirl tower did not affect the aerodynamic characteristics of the blade. The ground effect was studied by comparing with the numerical result for the out of ground condition and the result of an analytic model.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 추계 학술대회논문집
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• pp.236-242
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• 2007

A theoretical and numerical investigation is performed on the flow in a micronozzle for precision-controlled seal dispenser. The working fluid is a highly viscous epoxy used as sealant in producing LCD panels, which contains a number of tiny solid spacers. Flow analysis is conducted in order to achieve the optimal design oj internal geometry of a nozzle. A simplified design analysis methodology is proposed for predicting the flow in the nozzle based on the assumption that the Reynolds number is much less than O(1). The parallel numerical computations are performed by using a CFD package FLUENT. Comparison discloses that the theoretical model gives a good prediction on the distribution of pressure and wall shear stress in the nozzle. However, the theoretical model has a difficulty in predicting the maximum wall shear stress as found in a limited region near edge by numerical computation. The theoretical and numerical simulations provide the good guideline for designing a dispensing micronozzle.

• 한국전산유체공학회지
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• 제12권4호
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• pp.54-60
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• 2007

A theoretical and numerical investigation is performed on the flow in a micronozzle for precision-controlled sealant dispenser. The working fluid is a highly viscous epoxy used as sealant in producing LCD panels, which contains a number of tiny solid spacers. Flow analysis is conducted in order to achieve the optimal design of internal geometry of a nozzle. A simplified design analysis methodology is proposed for predicting the flow in the nozzle based on the assumption that the Reynolds number is much less than O(1). The parallel numerical computations are performed by using a CFD package FLUENT. Comparison discloses that the theoretical model gives a good prediction on the distribution of pressure and wall shear stress in the nozzle. However, the theoretical model has a difficulty in predicting the maximum wall shear stress as found in a limited region near edge by numerical computation. The theoretical and numerical simulations provide the good guideline for designing a dispensing micronozzle.

• 대한기계학회논문집B
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• 제41권2호
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• pp.117-124
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• 2017

본 연구에서는 Coloring 기법을 적용한 Gauss-Seidel 해법의 연산 성능을 분석하기 위해 2차원과 3차원 전도 열전달 문제를 다양한 격자 크기에서 해석하였다. 지배방정식의 이산화는 유한차분법과 유한요소법을 사용하였다. CPU의 경우에는 상대적으로 작은 격자계에서 연산 성능이 좋으며, 계산에 사용되는 메모리의 크기가 캐시메모리보다 크게 되면 연산 성능이 급격히 떨어진다. 반면에, GPU는 메모리 지연시간 숨김 특성으로 인하여 격자의 수가 충분히 많을 때 연산 성능이 좋다. GPU에 기반한 Colored Gauss-Seidel 해법은 단일 CPU를 이용한 연산에 비해서 각각 최대 7배의 속도 향상을 보인다. 또한, GPU 기반에서 Colored Gauss-Seidel 해법은 Jacobi 보다 약 2배 빠름을 확인하였다.