터빈 블레이드 주위 유동 해석을 위한 자동 정렬 격자 생성

김세진,유동현 한국전산유체공학회 2022 한국전산유체공학회지 Vol.27 No.2

A computational grid is a crucial component in computational fluid dynamics, that greatly affects the accuracy and the cost of a numerical analysis. However, generating a grid with high quality is challenging and time-consuming, for turbomachinery blades with various shapes and configurations. In addition, the user-dependency in grid generation deteriorates the reliability of the analysis. We develop an algorithm that can automatically generate a structured grid for simulations of flow over a turbomachinery blade. Using an elliptic grid generation method, a high-quality O-type grid with high grid orthogonality on the wall is generated. Users only need to specify basic grid specifications such as grid number and resolution. The efficacy of the developed algorithm is evaluated for various two-dimensional and three-dimensional blades.

선박 거주구역 화재시뮬레이션을 위한 격자크기와 생성방법에 관한 연구

김별,황광일 해양환경안전학회 2017 海洋環境安全學會誌 Vol.23 No.7

For fires in ship accommodation areas, if it is possible to predict the pattern in which fire will spread and suggest proper countermeasures according to a situation using a fire simulation tool, fire damage may be reduced. However, fire simulations have a practical limit: a significant amount of time is required to analyze the results due to the size of the computational domain and the number of grids. Therefore, in this study, applicable grid size for fire simulations to predict fire patterns in ship accommodation areas was analyzed, and a generation method was conducted to predict fire behavior in real time. As a result, a value within 0.25[m] was judged appropriate as an applicable grid size for ship accommodation areas. Also, in comparison with studies using a single mesh generation method, the visibility value was similar, within 4.3%, as was the temperature value, within 8.3%, when a multi mesh generation method was used, showing a decline of 80% in analysis time. Therefore, it was confirmed that composing a grid using multi mesh was effective for reducing analysis time. 선박 거주구역에 화재발생 시 화재시뮬레이션 도구를 이용하여 화재확산형상을 실시간으로 예측하고 상황에 따른 적절한 대응방안을 제시할 수 있다면 화재사고로 인한 인명피해를 최소화시킬 수 있을 것으로 예상된다. 그러나 오늘날 화재시뮬레이션은 해석대상공간의 크기와 그리드 개수에 따라 해석을 하는데 있어, 매우 장시간을 필요로 하는 현실적 한계가 있다. 이에 이 연구에서는 화재시뮬레이션 시간단축을 목적으로 선박 거주구역 화재시뮬레이션에 적용할 수 있는 격자크기와 생성방법에 대한 연구를 수행하였다. 연구결과 선박 거주구역에 적용되는 격자크기는 0.25[m] 이내의 값을 사용하는 것이 가장 효율적인 것으로 판단되었다. 또한 single mesh 격자생성방법으로 수행했을 경우와 비교하여, multi mesh 격자생성방법으로 시뮬레이션을 수행하였을 때 가시거리 값은 4.3%, 온도 값은 8.3% 이내에서 유사하고 해석시간은 약 80% 감소하였기 때문에, multi mesh 방법으로 격자를 생성하는 것이 해석시간을 단축하는데 있어 매우 효과적임을 확인하였다.

CAD 형상 데이터를 이용한 비정렬 표면 격자계의 자동 생성 기법

이봉주(B.J. Lee),김병수(B.S. Kim) 한국전산유체공학회 2007 한국전산유체공학회지 Vol.12 No.4

Computational Fluid Dynamics (CFD) approach is now playing an important role in the engineering process in these days. Generating proper grid system in time for the region of interest is prerequisite for the efficient numerical calculation of flow physics using CFD approach. Grid generation is, however, usually considered as a major obstacle for a routine and successful application of numerical approaches in the engineering process. CFD approach based on the unstructured grid system is gaining popularity due to its simplicity and efficiency for generating grid system compared to the structured grid approaches, especially for complex geometries. In this paper an automated triangular surface grid generation using CAD(Computer Aided Design) surface data is proposed. According to the present method, the CAD surface data imported in the STL(Stereo-lithography) format is processed to identify feature edges defining the topology and geometry of the surface shape first. When the feature edges are identified, node points along the edges are distributed. The initial fronts which connect those feature edge nodes are constructed and then they are advanced along the CAD surface data inward until the surface is fully covered by triangular surface grid cells using Advancing Front Method. It is found that this approach can be implemented in an automated way successfully saving man-hours and reducing human-errors in generating triangular surface grid system.

중첩 격자계의 효율적 Hole Finding 기법

김병수(B.S. Kim),고성호(S.H. Ko) 한국전산유체공학회 2006 한국전산유체공학회지 Vol.11 No.2

In this paper an automated hole-finding method for overset grids is introduced which uses recursive octree-cell division. A graphic program which enables the user to do the hole-cutting with ease is also introduced. Using this program it is found that there is an optimum combination of the level of octree division and vector calculation for the efficient and fast hole finding.

포텐셜 해석자를 이용한 2차원 유동의 격자 생성 연구

이재훈(J. Lee),정경진(K. Jung) 한국전산유체공학회 2016 한국전산유체공학회지 Vol.21 No.1

One of the obstacles on the grid generation for complex geometries with multi-block structured grids is the domain decomposition. In this paper, the domain decomposition for two-dimensional flow is studied using the flow characteristics. The potential flow equation with the source distribution on the panel surface is solved to extract the information of the flow. The current approach is applied to a two-dimensional cylinder and Bi-NACA0012 problems. The generated grids are applied to generic flow solvers and reasonable results are obtained. It can be concluded that the current methods is useful in the domain decomposition for the multi-block structured grid.

자동요소망생성을 위한 격자구성기법 적용

이준성,박영재,장윤석,최재붕,김영진 한국정밀공학회 2005 한국정밀공학회 학술발표대회 논문집 Vol.2005 No.5월

교육용 특화 격자 생성 프로그램의 개발

류기명(G.M. Ryu),김병수(Byoungsoo Kim) 한국전산유체공학회 2014 한국전산유체공학회 학술대회논문집 Vol.2014 No.11

A grid generation program for specific problems is introduced. The program allows users to easily generate grid system for specific geometry such as an airfoil, cylinder, wedge, flat plate, and nozzle. Generating grid system for those problems can be proceeded with minimum user inputs such as geometry-defining parameters and grid-defining parameters. By using this program learning stage for preprocessing of CFD application can be efficiently shorten and novice students can learn and acquire experience by trying out grid generation and CFD solution by themselves.

효율적 표면격자 생성을 위한 표면 곡률 근사화 기법

김병수 한국전산유체공학회 2020 한국전산유체공학회지 Vol.25 No.2

In this paper the issue of recovering surface curvature from the geometry data imported in the triangulated STL format for effective surface grid generation is described. Mathematical description and procedure to achieve division of a triangular Bezier surface by using patch point idea is given. The key issue in expressing a sub-region of triangular Bezier surface is to find the Barycentric coordinates of patch points of the sub-region. Once the coordinates of those Patch points are found, then the control points which are needed to describe the triangular Bezier surface for the sub-region can be routinely obtained. It is demonstrated that the quality of surface description along a geometry imported in STL format can be improved by using the current method of approximate curvature-recovery, which will eventually improve the accuracy and effectiveness of surface grid generated along the surface imported in STL format.

문제 지향적 교육용 격자 생성 프로그램의 개발

류기명(G.M. Ryu),김병수(Byoungsoo Kim) 한국전산유체공학회 2015 한국전산유체공학회지 Vol.20 No.1

A grid generation program for specific problems is introduced. The program allows users to easily generate grid system for specific geometry such as an airfoil, cylinder, wedge, flat plate, and nozzle. Generating grid system for those problems can be proceeded with minimum user inputs such as geometry-defining parameters and grid-defining parameters. By using this program learning stage for preprocessing of CFD application can be efficiently shorten and novice students can learn and acquire experience by trying out grid generation and CFD solution by themselves.

산업용 자율 주행 로봇에서의 격자 지도를 사용한 강화학습 기반 회피 경로 생성기 개발

양정연(Jeong-Yean Yang) 한국콘텐츠학회 2019 한국콘텐츠학회논문지 Vol.19 No.3

자율 주행은 이동 로봇의 핵심적 기술로써, 측정된 센서 정보를 토대로 불확실한 위치 정보를 이용한 지도 작성 및 수정 기능과, 불확실한 지도 및 센서 정보를 이용한 로봇의 위치 인식 기능으로 구성된다. 자율주행은 이러한 주행 위치의 불확실성에 기반한 확률론적 방법론과 함께 주행 시 장애물의 감지 및 회피 경로의 생성, 반복적 주행 패턴에 따른 경로 관리 기능이 필수적 요소이다. 거리 기반의 스캐너를 통해 관측된 센서 입력은, 지도 구성에 사용된 벽과 같은 정적 물체와 주행 시의 사람처럼 움직이는 동적 물체와의 구별이 필요하기 떄문에 장애물 감지에 어려움이 있다. 본 논문에서는, 이러한 자율 주행 환경에서 기존의 정적, 동적 개체의 판별 방식과 비교하여, 장애물 회피를 위한 저해상도 격자 공간의 생성 및 강화학습을 이용한 경로 생성을 다루고자 한다. 최종적으로 실험을 통해 제안된 방법론의 실효성을 검증하고자 한다. Autonomous locomotion has two essential functionalities: mapping builds and updates maps by uncertain position information and measured sensor inputs, and localization is to find the positional information with the inaccurate map and the sensor information. In addition, obstacle detection, avoidance, and path designs are necessarily required for autonomous locomotion by combining the probabilistic methods based on uncertain locations. The sensory inputs, which are measured by a metric-based scanner, have difficulties of distinguishing moving obstacles like humans from static objects like walls in given environments. This paper proposes the low resolution grid map combined with reinforcement learning, which is compared with the conventional recognition method for detecting static and moving objects to generate obstacle avoiding path. Finally, the proposed method is verified with experimental results.