• International Journal of Fluid Machinery and Systems
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• 제6권2호
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• pp.87-93
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• 2013

In order to study the effect of the fluid-structure interaction (FSI) on the simulation results, the external characteristics and internal flow features of a diffuser pump were analyzed with a two-way flow solid coupling method. And the static and dynamic structure analysis of the blade was also caculated with the FEA method. The steady flow field is based on Reynolds Averaged N-S equations with standard $k-{\varepsilon}$ turbulent model, the unsteady flow field is based on the large eddy simulation, and the structure response is based on elastic transient structural dynamic equation. The results showed that the effect of FSI on the head prediction based on CFD really exists. At the same radius, the van mises stress on the nodes closed shroud and hub was larger than other nodes. A large deformation region existed near inlet side at the middle of blades. The strength of impeller satisfied the strength requirement with static stress analysis based on the fourth strength theory. The dynamic stress varied periodically with the impeller rotating. It was also found that the fundamental frequency of the dynamic stress is the rotating frequency and its harmonic frequency. The frequency of maximum stress amplitude at node 1626 was 7 times of the rotating frequency. The frequency of maximum stress amplitude at node 2328 was 14 times of the rotating frequency. No matter strength failure or fatigue failure, the root of blades near shroud is the key region to analyse.

• 한국유체기계학회 논문집
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• 제17권1호
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• pp.47-53
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• 2014

This paper aims to present the design and performance evaluation of a counter-rotating tidal turbine using CFD and to compare its performance with single rotor. The device scale is 10kW and the rotating part consists of two rotors which rotate in opposite direction. Compared with conventional single rotor, the counter-rotating system shows higher power efficiency at high stream velocity but lower efficiency at low stream velocity. The added counter-rotated rotor together helps improve the energy absorption capacity but has influence on the upstream rotor that reduces its performance. In terms of power capture, the designed counter-rotating tidal turbine is more advantageous in high speed tidal condition.

• 한국가시화정보학회지
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• 제2권2호
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• pp.38-44
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• 2004

Theoretical and numerical studies are given to the sink flows within a rotating circular tank driven by the fluid withdrawal from a bottom circular hole. It was found that, when the upper free surface was set with no-slip boundary conditions, the Ekman boundary-layer develops not only above the bottom surface but under the top surface. The sink fluid is coming from the two Ekman layers, and the mass transfer from the bulk, inviscid region is dependent on the rotational speed. It is also remarkable to see that all the fluid gathered along the axis flows in a form of rapidly rotating fluid column haying almost the same diameter as the bottom hole.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.121-126
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• 2007

In this paper the vibration system is consisted of a rotating cantilever pipe conveying fluid and a tip mass. The equation of motion is derived applying a modeling method that employs hybrid deformation variables. 'TI1e influences of the rotating angular velocity, mass ratio and the velocity of fluid flow on the stability of a cantilever pipe are studied by the numerical method. The effect of tip mass on the stability of a rotating cantilever pipe are also studied. The influences of a tip mass, the velocity of fluid the angular velocity of a cantilever pipe and the coupling of these factors on the stability of a cantilever pipe are analytically clarified.

• 태양에너지
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• 제11권1호
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• pp.78-86
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• 1991

내부에 삼각형 핀을 갖는 회전형 히트파이프의 작동유체로 물-에탈올 2성분 유체를 사용하였을때 Nusselt의 막응축이론을 기초로 하여 핀 및 그루브의 전열특성을 유한요소법에 의한 수치해석을 하였으며 또한 실험을 행하여 비교하였다. 히트파이프의 회전수가 증가할수록, 내부 증기압이 높을수록 전열량은 완만하게 증가하지만 에탄올 농도가 커 질수록 전열량은 감소하였다. 그리고 순수 에탄올만을 작동유체로 하는 경우는 증류수만을 작동유체로 하는 경우의 전열량의 $0.75{\sim}0.85$정도로 나타났다. 또한 에탄올 농도가 0. 2전후에서 전열효과 및 작동온도 범위 등이 가장 유리하게 나타났다.

• 한국유체기계학회 논문집
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• 제2권2호
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• pp.5-12
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• 1999

This study presents the measured unsteady flctuation of impeller discharge flow for a centrifugal compressor in an unstable operating region. The characteristics of the blade-to-blade flow at rotating stall onset were investigated by measuring unsteady velocity fluctuations at several different diffuser axial distances using a hot wire anemometer. The flow characteristics in terms of the radial and tangential velocity components and the flow angle distribution at the impeller exit were analyzed using phase-locked ensemble averaging techniques. As a result, increase or decrease of the radial velocity component during the rotating stall is dominated by that of the suction side. The radial velocity distributions show the opposite trends in the regions where the radial velocity during rotating stall onset increases and decreases.

• International Journal of Fluid Machinery and Systems
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• 제10권1호
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• pp.9-18
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• 2017

Numerical simulation is carried out for flow characteristics in a plenum fan and the influence of the diameter ratio of the rotating vaneless diffuser on the performance of plenum fan is analyzed. The diameter ratio of the rotating vaneless diffuser employed is from 1.03 to 1.3. The research results show that the rotating vaneless diffuser is able to enhance the performance of plenum fan. It is found that there is significant improvement in static pressure and efficiency at the diameter ratio of 1.05 at high flow coefficients, while the optimal diameter ratio is 1.2 at rated and low flow coefficient.

• 설비공학논문집
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• 제7권1호
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• pp.13-19
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• 1995

An experimental investigation has been made for flow in a circular cylinder with a rotating bottom disk. Flow system considered in this paper is a characteristic model of interior flows of an electric washing machine. Flows in a tub of an electric washing machine are driven by a rotating bottom disk called a pulsator. The simple and characteristic model was composed of a circular cylinder with impulsively rotating endwall disk and a viscous fluid in it. Rotational motion of the pulsator is periodic and alternative in rotation direction. The flow field in the interior region is governed by a horizontal boundary layer forms on the impulsively rotating disk. Experimental approach was accomplished by adopting an image processing technique for velocity measurements. Comprehensive details of the flow structure are presented. Also a meridional circulation is obtained by tracking image particles suspended in the fluid. Flow structure and data are successfully procured for this complex rotating flow field.

• Korea-Australia Rheology Journal
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• 제21권1호
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• pp.27-37
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• 2009

In this work, we numerically investigate the effect of viscoelasticity on 2D laminar vortex dynamics in flows past a single rotating cylinder for rotational rates $0{\leq}{\alpha}{\leq}5$ (the rotational rate ex is defined by the ratio of the circumferential rotating velocity to free stream velocity) at Re=100, in which the vortex shedding has been predicted to occur in literature for Newtonian fluids. The objective of the present research is to develop a promising technique to fully suppress the vortex shedding past a bluff body by rotating a cylinder and controlling fluid elasticity. The predicted vortex dynamics with the present method is consistent with the previous works for Newtonian flows past a rotating cylinder. We also verified our method by comparing our data with the literature in the case of viscoelastic flow past a non-rotating cylinder. For $0{\leq}{\alpha}{\leq}1.8$, the frequency of vortex shedding slightly decreases but the fluctuation of drag and lift coefficient significantly decreases with increasing fluid elasticity. We observe that the vortex shedding of viscoelastic flow disappears at lower ${\alpha}$ than the Newtonian case. At ${\alpha}$=5, the relationship between the frequency of vortex shedding and Weissenberg number (Wi) is predicted to be non-monotonic and have a minimum around Wi=0.25. The vortex shedding finally disappears over critical Wi number. The present results suggest that the vortex shedding in the flow around a rotating cylinder can be more effectively suppressed for viscoelastic fluids than Newtonian fluids.

• International Journal of Aerospace System Engineering
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• 제8권1호
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• pp.1-13
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• 2021

Contra-rotating fan is comprised of two rotors which are rotating in the opposite direction. The fan stages are named rotor-1 and rotor-2. Benefits from the use of contra rotation are in terms of better efficiency and improved thrust to weight ratio. Failure of contra-rotating fan stage blade in-service results in safety risks, repair costs, and revenue losses. This paper focuses on the vibration analysis and one way fluid-structure interaction of high aspect ratio, low speed contrarotating fan rotors. Modal analysis and modal pre-stress analysis of contra-rotating fan rotors were carried out to calculate the natural frequencies, One way fluid-structure interaction (FSI) was carried out where the computational analysis of the blades was performed using ANSYS CFX. The boundary conditions for CFD analysis were considered from the actual experimental velocity flow field at the inlet and pressure outlet. Based on the results obtained from the CFD analysis, the structural analysis such as deformation and Von-Misses stresses was carried out by using the finite element method (FEM) with ANSYS. The results provide necessary guidelines for the safe running of the contra-rotating fan. The analysis also will be helpful to understand the change of flow behavior due to a rotor deformation.