회전하는 하나의 내부 원통에서 서로 다른 반경비가 Taylor-Couette 유동에 미치는 영향

승삼선(Samsun Seung),김상일(Sangil Kim) 대한기계학회 2018 大韓機械學會論文集B Vol.42 No.12

회전하는 하나의 내부 원통이 서로 다른 반경비를 갖는 경우에 Taylor vortex형성에 미치는 영향에 대해 수치해석을 수행하였다. 서로 다른 반경비는 내부 원통 중앙을 기준으로 동일한 폭에 깊이를 달리한 것으로 먼저 반경비가 0.83인 매끈한 내부 원통에 대한 수치계산 결과를 기존의 실험결과와 비교하여, 타당성을 검토하였다. 그런 다음, 내부 원통 중앙에 동일한 홈의 폭에 깊이를 각각 3, 6, 9, 12 mm 달리한 내부 원통에 회전수 25, 100 rpm인 경우의 수치계산 결과와 비교하였다. 그 결과, Taylor vortex는 층류인 경우 내부 원통 양끝에서 생성되기 시작하지만 홈이 있는 경우에는 홈 모서리에서도 이루어짐을 확인하였다. 홈의 깊이와 내부 원통의 회전수에 따라 쌍으로 이루어진 Taylor vortex셀의 폭이 달라졌으며, 회전수가 큰 경우에는 작은 경우보다 Taylor vortex 셀의 폭이 넓어져 개수가 감소하였다. 또한 각각의 Taylor vortex 쌍의 vortex 중심은 이웃하고 있는 vortex 쌍 사이의 vortex 중심보다 더 가깝게 자리하고 있음을 확인하였다. The Taylor-Couette flow in a rotating inner cylinder with different radius ratios has been studied numerically to show the effects of Taylor vortices formation, where different radius ratios refer to the varied depths having the same width based on the center of the inner cylinder. The numerical calculations results are compared with those of the straight inner cylinder. In order to examine the feasibility of the numerical calculations, the numerical results are compared with existing experimental results for a straight inner cylinder. Then, we compare the numerical results in the case of inner cylinders with different radius ratios. Initially, laminar Taylor vortices form at the end walls and corners of the groove. Results show that the widths of pairs of Taylor vortex cells are varied according to the depth and rotational speed of the inner cylinder. In the case involving a higher rotational speed of inner cylinder widths, and the number of pairs of Taylor vortex cells are wide and decreasing than low rotational speed of it. In addition, the vortex centers of each Taylor vortex pair are closer together than the vortex centers between neighboring vortex pairs.

임펠러–디퓨저 반경비가 천음속 원심압축기 성능에 미치는 영향

이병주(Byung Ju Lee),김민기(Min-Gi Kim),정진택(Jin Taek Chung) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11

내부회전실린더를 가진 동심환형관에서 반경비의 영향에 관한 수치해석적 연구

배강열(Kang-Youl Bae),김형범(Hyoung-Bum Kim),이상혁(Sang-Hyuk Lee) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-

This paper represents the numerical analysis on effects of radius ratio in a concentric annulus with a rotating inner cylinder. The numerical model consisted of two cylinder which inner cylinder is rotating and outer cylinder is fix, and the axial direction is used the cyclic condition because of the length for axial direction is assumed infinite. The diameter of inner cylinder is assumed 86.8mm, the numerical parameters are angular velocity and radius ratio. Also, the whole walls of numerical model have no-slip and the working fluid is used water at 20℃. The numerical analysis is assumed the transient state to observe the flow variations by time and the 3-D cylindrical coordinate system. The calculation grid adopted a non-constant grid for dense arrangement near the wall side of cylinder, the standard k-ω high Reynolds number model to consider the effect of turbulence flow and wall, the fully implicit method for time term and the quick scheme for momentum equation. The numerical method is compared with the experimental results by Wereley and Lueptow, and the results are very good agreement. As the results, TVF isn't appeared when Re is small because of the initial flow instability is disappear by effect of the centrifugal force and viscosity. The vortex size is from 0.8 to 1.1 for TVF at various η, and the traveling distance for wavy vortex have the critical traveling distance for each case.

반경비 및 각속도의 변화에 따른 Taylor 유동에 관한 연구

배강열(K. Y. Bae),김형범(H. B. Kim),정희택(H. T. Chung) 한국전산유체공학회 2007 한국전산유체공학회 학술대회논문집 Vol.2007 No.-

This paper represents the numerical study on Taylor flow according to the radius ratio and the angular velocity for flow between tow cylinder. The numerical model is consisted of two cylinder which inner cylinder is rotating and outer cylinder is fix, and the axial direction is used the cyclic condition because of the length for axial direction is assumed infinite. The diameter of inner cylinder is assumed 86.8 mm, the numerical parameters are angular velocity and radius ratio. The numerical method is compared with the experimental results by Wereley, and the results are very good agreement. The critical Taylor number is calculated by theoretical and numerical analysis, and the results is showed the difference about 土10 %. As Re/Rec is increased, Taylor vortex is changed to wary vortex, and then the wave number for azimuthal direction is increased. Azimuthal wave according to the radius ratio is showed high amplitude and low frequence in case of small radius ratio, and is showed low amplitude and high frequence in case of large radius ratio.

실린더 내부 유동에서 반경비 및 각속도의 변화에 따른 임계수에 관한 수치해석

배강열(Kang-Youl Bae),김형범(Hyoung-Bum Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11

This paper represents the numerical analysis on critical Taylor number according to the variation of radius ratio and angular velocity on flow in cylinder. The numerical model consisted of two cylinder which inner cylinder is rotating and outer cylinder is fix, and the axial direction is used the cyclic condition because of the length for axial direction is assumed infinite. The diameter of inner cylinder is assumed 86.8mm, the numerical parameters are angular velocity and radius ratio. The numerical method is compared with the experimental results by Wereley, and the results are very good agreement. As the results, the vortex size is from 0.8 to 1.1 for TVF at various  , and the traveling distance for wavy vortex have the critical traveling distance for each case. Also, the critical Taylor number is calculated by theoretical and numerical analysis, and the results is showed the difference about ±2~3%.

돌출형 거칠기벽이 있는 동심환형관의 유동에 대한 마찰계수

안수환,Ahn, Soo Whan 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.5

The combined effects of radius ratio and roughness pitch ratio on the turbulent fluid flow characteristics of the fully developed flow in the annullar tubes with rib-roughened core walls were determined for Reynolds number ranging from 12,000 to 66,000. To understand the underlying physical phenomena responsible for friction factor enhancement, measurements of velocity profiles and zero shear stress and maximum velocity positions were combined to propose the friction factor correlation. Friction factors were found to be a function of the roughness pitch ratio and radius ratio.

Slim hole 환형관내에서 굴착유체의 유동특성에 관한 연구

서병택,장영근 한국기계기술학회 2007 한국기계기술학회지 Vol.9 No.3

The paper concerns an experimental and numerical study of fully developed laminar flow of a Newtonian, water and non-Newtonian fluids, 0.2% aqueous of sodium carboxymethyl cellulose(CMC) solution in concentric and eccentric annuli with combined bulk axial flow and inner cylinder rotation. Pressure losses and skin friction coefficients have been measured when the inner cylinder rotates at the speed of 0~300 rpm. The influences of rotation, radius ratio and working fluid on the annular flow field are investigated.

평판에서 타원공의 형상에 따른 피로도지수 해석

송준혁,노홍길,강희용,양성모 한국공작기계학회 2003 한국공작기계학회 춘계학술대회논문집 Vol.2003 No.-

A FQI(fatigue quality index) analysis using the concept of SF(severity factor) is performed to various shape of elliptical hole. FQI is fatigue quality index to estimate the dynamic SF from static SF by finite element analysis. Since the SF is affected by the location of cutout in plate and radius ratio, static SF is analyzed with finite element method and forms the equation of FQI for predicting a dynamic SF. To examine the validity, dynamic SF is measured by photoelastics and thermalelastics for an epoxy resin plate with various elliptical holes under dynamic load.

환형관내 굴착유체의 편심회전유동에 관한 수치해석적 연구

서병택,장영근,김덕주 한국기계기술학회 2011 한국기계기술학회지 Vol.13 No.4

The paper concerns numerical study of fully developed laminar flow of a Newtonian water and non-Newtonian fluids, 0.2% aqueous of sodium carboxymethyl cellulose(CMC) solution in eccentric annuli with combined bulk axial flow and inner cylinder rotation. Pressure losses and skin friction coefficients have been measured when the inner cylinder rotates at the speed of 0~200 rpm. A numerical analysis considered mainly the effects of annular eccentricity and inner cylinder rotation. The present analysis has demonstrated the importance of the drill pipe rotation and eccentricity. In eccentricity of 0.7 of a Newtonian water, the flow field is recirculation dominated and unexpected behavior is observed. it generates a strong rotation directed layer, that two opposing effects act to create two local peaks of the axial velocity. The influences of rotation, radius ratio and working fluid on the annular flow field are investigated.

고온의 강관 냉각용 삼중 열교환기에 대한 열해석

고봉환,박승호,신동신 대한설비공학회 1999 설비공학 논문집 Vol.11 No.5

The objective of present study is to analyze a hot steel-tube cooling system as a kind of concentric triple-passage heat exchanger, whose inner tube is moving with a constant speed. Velocities and temperatures of an antioxidant gas flowing between inner and outer tubes are calculated theoretically for both laminar and turbulent flow regimes and used to give Nusselt numbers and friction factors with respect to various radius ratios and velocity ratios. In addition, it is shown that heat transfer coefficients based on ratios of average heat fluxes from inner and outer tubes might result in great errors for the temperature distributions of the flows, since the local heat transfer coefficients are dependent on the local heat flux ratios.