동적격자변형기법을 이용한 2차원 실린더의 와류유발진동에 대한 수치해석

이남훈,백지영,이승수 한국항공우주학회 2012 한국항공우주학회 학술발표회 논문집 Vol.2012 No.11

이 논문에서는 2차원 실린더의 와류유발진동에 따른 Lock-in 현상에 대해 수치해석을 수행하였다. 실린더의 운동을 모사하기 위해 변형격자와 고정격자를 이용하였다. 스프링 상사를 이용하여 격자를 변형하였다. 격자수 및 시간 간격 등을 조절해 얻은 수렴된 수치해가 비교 및 검증에 사용되었다. 또한, 유체-구조 결합 방법들의 효율성과 정확도를 비교 검토하였다. In this paper, numerical simulations are performed on the Lock-in phenomena of vortex induced vibration(VIV) of two dimensional cylinder. A deforming grid as well as a rigidly moving grid are used to simulate the movement of the cylinder. The grid deformation is accomplished by the linear spring analogy. Converged solutions, which obtained by controlling the grid size and non-dimensional time step, are used for comparison and validation of the analysis results. Moreover, the efficiency and accuracy of the coupling methods for fluid-structure interaction are examined.

동적격자변형기법을 이용한 2차원 실린더의 와류유발진동에 대한 수치해석

이남훈(Namhun Lee),백지영(Jiyoung Baek),이승수(Seungsoo Lee) 한국항공우주학회 2013 韓國航空宇宙學會誌 Vol.41 No.1

이 논문에서는 2 차원 실린더의 와류유발진동에 따른 Lock-in 현상에 대해 수치해석을 수행하였다. 실린더의 운동을 모사하기 위해 변형격자와 고정격자를 이용하였다. 스프링상사기법을 이용하여 격자를 변형하였다. 격자수 및 시간 간격 등을 조절해 얻은 수렴된 수치해가 비교 및 검증에 사용되었다. 또한, 유체-구조 결합 방법들의 효율성과 정확도를 비교 검토하였다. In this paper, numerical simulations are performed on the lock-in phenomena of vortex induced vibration(VIV) of a two dimensional cylinder. A deforming grid as well as a rigidly moving grid are used to simulate the movement of the cylinder. The grid deformation is accomplished by the linear spring analogy. Converged solutions, which are obtained by controling the grid size and the non-dimensional time step, are used for comparison and validation of the analysis results. Moreover, the efficiency and the accuracy of the coupling methods for fluid-structure interaction are examined.

시계의 메카트로닉스화와 관련 특허맵

김중,윤천한 한국특허학회 2008 특허학연구 : 한국특허학회지 Vol.10 No.3

지구의 공전과 자전은 지구에 전해지는 빛에너지의 변화를 초래하고 이는 밤과 낮의 주기적인 변화인 시간을 만들고 또한 온도 및 습도 등 기후의 변화도 초래한다. 시계는 이와 같은 주기적인 변화를 측정하고 또한 시간의 간격을 알리는 것이다. 빙하기 시대인 기원전 20,000년에 유럽에서 막대기를 이용하여 선을 그리거나 뼈에 구멍을 내어 시간을 측정하였다. 해시계는 18세기까지 낮의 시간을 측정하는 보편적인 장치이었으나 그 정밀성과 사용시간의 제한 등으로 인하여 물시계 등이 개발되었다. 1410년경 스프링의 발달로 기계적인 에너지를 이용하는 시계가 만들어졌다. 그 후 시계는 자동시계, 전자시계로 발전하였으며 시간의 표시방법도 아날로그 혹은 디지털 방법의 채용으로 다양하게 변화하였다. 현대의 시계는 단지 시간을 확인하는 기능뿐만 아니라 알람 등의 부가적인 기능을 갖춘 기능성 시계가 많이 이용되고 있으며 컴퓨터 등의 전자제품도 시계의 기능을 가지고 있다. 즉 시계의 동작을 위하여 동력원, 제어장치, 표시부 등의 메카트로닉스 기술을 응용하는 시계가 사용되고 있다. The revolution and rotation of the Earth in a gesture that is causing to create a time by period the changes of the day and night, such as temperature and humidity also will cause climate change. The watch measure the changes, such as a clock cycle, and will also notify you of the time interval. In ice age BC 20,000 years in Europe it is for taking the time to measure to use a stick to draw a line or in the hole the bone. Sundial is the universal device to measure time in days to the 18th century, because of the lack of precision and the limitations of usage of it, the water clock was developed. In around 1410 the mechanical clock was made to use mechanical energy of spring. Since then, the automatic watch, electronic clocks was developed. And the display of time was adopted method of a variety of analog or digital way. The modern clock is displaying only the time the clock, as well as the ability to check the alarm clock and a lot of functionality with additional features, such as computers and electronic products have the features of the clock. This means that watch has the behavior of power source, control devices, and display this is to be apply the technology of mechatronics. In this paper, and mechatronics technology and patents related to the relationships of the modern watch for presents.

DEVELOPMENT OF A THREE-DIMENSIONAL MULTI-BLOCK STRUCTURED GRID DEFORMATION CODE FOR COMPLEX CONFIGURATIONS

A.D. Hoang,Y.M. Lee(이영민),S.K. Jung(정성기),A.T. Nguyen,R.S. Myong(명노신) 한국전산유체공학회 2007 한국전산유체공학회지 Vol.12 No.4

In this study, a multi-block structured grid deformation code based on a hybrid of a transfinite interpolation algorithm and spring analogy was developed. The configuration was modeled by a Bezier surface. A combination of the spring analogy for block vertices and the transfinite interpolation for interior grid points helps to increase the robustness and makes it suitable for distributed computing. An elliptic smoothing operator was applied to the block faces with sub-faces in order to maintain the grid smoothness and skewness. The capability of this code was demonstrated on a range of simple and complex configurations including an airfoil and a wing-body configuration.

비정렬 혼합 격자계에서 신속 격자 변형 기법을 이용한 비정상 점성 유동 해석

이희동(H.D. Lee),정문승(M.S. Jung),권오준(O.J. Kwon) 한국전산유체공학회 2009 한국전산유체공학회지 Vol.14 No.3

In the present study, a fast grid deformation technique has been incorporated into the unsteady compressible and incompressible viscous flow solvers on unstructured hybrid meshes. An algebraic method based on the basis decomposition of normal edge vector was used for the deformation of viscous elements, and a ball-vertex spring analogy was adopted for in viscid elements among several spring analogy methods due to its robustness. The present method was validated by comparing the results obtained from the grid deformation and the rigid motion of entire grids. Fish swimming motion of an NACA0012 airfoil and flapping wing motion of a generic fighter were also simulated to demonstrate the robustness of the present grid deformation technique.

비정렬 혼합 격자계에서 격자 변형 기법을 이용한 비정상 점성 유동 수치 모사

이희동(H.D. Lee),정문승(M.S. Jung),권오준(O.J. Kwon) 한국전산유체공학회 2009 한국전산유체공학회 학술대회논문집 Vol.2009 No.4

In the present study, a grid deformation technique has been incorporated into the unsteady compressible and incompressible viscous flow solvers on unstructured hybrid meshes. An algebraic method based on the basis decomposition of normal edge vector was used for the deformation of viscous elements, and a ball-vertex spring analogy was adopted for in viscid elements among several spring analogy methods due to its robustness. The present method was validated by comparing the results obtained from the grid deformation and the rigid motion of entire grids. Fish swimming motion of an NACA0012 airfoil and flapping wing motion of a generic fighter were simulated to demonstrate the robustness of the present grid deformation technique.

비정렬 혼합 격자계에서 격자 변형 기법을 이용한 가변노즐 유동 해석

김재원(J.W. Kim),권오준(O.J. Kwon) 한국전산유체공학회 2013 한국전산유체공학회지 Vol.18 No.3

In the present study, unsteady flow simulations of a variable geometry nozzle were conducted using a two-dimensional flow solver based on hybrid unstructured meshes. The variable geometry nozzle is used to achieve efficient performances of aircraft engines at various operating conditions. To describe the motion of the variable geometry nozzle, an algebraic method based on the basis decomposition of normal edge vector was used for the deformation of viscous elements. A ball-vertex spring analogy was used for inviscid elements. The aerodynamic data were obtained for a range of nozzle pressure ratios, and the validations were made by comparing the present results with available experimental data. The unsteady nozzle flows were simulated with an oscillating diverging section and a converging-diverging section. It was found that the nozzle performances are influenced by the nozzle exit flow characteristics, mass flow rate, as well as unsteady effects. These unsteady effects are shown to behave differently depending on the frequency of the nozzle motion.

전산유체역학 기법을 이용한 물고기 유영에 관한 연구

김소희(S.H. Kim),정용수(Y.S. Jung),권오준(O.J. Kwon) 한국전산유체공학회 2014 한국전산유체공학회지 Vol.19 No.2

The aim of the present study is to investigate the flow interference between two adjacent undulating fish-like body, and its effect on the undulating propulsion. For this purpose, unsteady two dimensional incompressible flow calculations were conducted using an unstructured mesh flow solver, coupled with an overset mesh technique. To deal with mesh deformation due to fish locomotion, spring analogy is utilized. The fish body used in the simulation is constructed from the NACA0012 airfoil. The study indicates that the propulsion of undulating fish is proportional to frequency and wavelength of the midline oscillation when there is no adjacent fish. It also reveals that average thrust was increased when the vortex shedding from the tail was conserved well and pressure difference between upper and lower sides of the fish was magnified due to flow interference. From this study, which relative position and phase difference of locomotion between two fishes can generate maximum thrust was known among six different cases.

비정렬 혼합 격자계에서 격자 변형 기법을 이용한 가변노즐 유동 해석

김재원(J.W. Kim),권오준(O.J. Kwon) 한국전산유체공학회 2013 한국전산유체공학회 학술대회논문집 Vol.2013 No.5

In the present study, an unsteady flow simulations of a variable geometry nozzle were conducted using a two-dimensional flow solver based on hybrid unstructured meshes. The variable geometry nozzle are used to obtain the efficient performance of the aircraft engines at various operating conditions. To describe the motion of the variable geometry nozzle, an algebraic method based on the basis decomposition of normal edge vector was used for the deformation of viscous elements, and a ball-vertex spring analogy was used for inviscid elements. Aerodynamic data were obtained for a range of nozzle pressure ratios and the steady results were compared with available experimental data. The results show that the nozzle performances are influenced by geometry variations.

비정렬 다면체 격자계 기반 유동 해석 프로그램의 개발 및 진동하는 실린더 주변 유동에의 적용

이상혁(Sang Hyuk Lee),강성원(Seongwon Kang),허남건(Nahmkeon Hur) 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.5

In the present study, a CFD program based on a finite volume method was developed by using an unstructured polyhedral grid system for the accurate simulation with the complex geometry of computational domain. To simulate the transient flow induced by the moving solid object, the program used a fractional step method and a ALE (Algebric Lagrangian-Eulerian) method. The grid deformation for the moving of solid object were performed with a spring analogy based on the center coordinate of each computational grid. To verify the present program with these methodologies, the numerical results of the flow around the fixed and oscillating circular cylinder were compared with the previous numerical results.