• Title, Summary, Keyword: Rotating Flow

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Steady and Unsteady Rotating Flows between Concentric Cylinders (동심원 환내의 정상.비정상 회전 유동)

  • 심우건
    • Journal of KSNVE
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    • v.7 no.4
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    • pp.613-620
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    • 1997
  • Steady and unsteady flows between rotating cylinders are of interest on lubrication, convective heat transfer and flow-induced vibration in large rotating machinery. Steady rotating flow is generated by rotating cylinder with constant velocity while the unsteady rotating flow by oscillating cylinder with homogeneoysly oscillating velocity. An analytical method is developed based on the simple radial coordinate transformation for the steady and unsteady rotating flows in concentric annulus. The governing equations are simplified from Navier-Stokes equatins. Considering the skin friction based on the radial variation of circumferential flow velocity, the torques acting on the fixed and the rotating cylinder are evaluated in terms of added-inertia and added-damping torque coefficients. The coefficients are found to be influenced by the oscillatory Reynolds number and the radius ratio of two cylinders; however, the effect of the oscillatory Reynolds number on the coefficients is minor in case of relatively low radius ratio.

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Flow Characteristics in a Cavity Due to a Single Rotating Disk and Co-Rotating Disks (구속된 단일 회전원판과 동시 회전원판 내부의 유동 특성)

  • Won, Chung Ho;Ryu, Goo Young;Cho, Hyung Hee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.23 no.9
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    • pp.1192-1200
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    • 1999
  • The present study investigates flow characteristics in a cavity with one rotating disk and co-rotating disks for application to HDD. The experiments are conducted for rotating Reynolds numbers of $5.5{\times}104$ to $1.10{\times}105$ and for gap ratios of 0.059 to 0.175 in a single rotating and 0.047 to 0.094 in co-rotating disk. Time-resolved velocity components and turbulence intensity on the rotating disks are obtained by using LDA measurements. Detailed Knowledge of the flow characteristics is essential to analyze flow vibration and heat transfer and to design head-arm assembly and hub height in HDD. The results indicate that the velocity field in HDD is changed largely by the rotating Reynolds numbers and hub height of the disk.

Numerical Analysis of Stall Propagation in Linear Cascade (선형 익렬에서의 실속 전파에 관한 수치적 해석)

  • Seo, Young-Seok;Baek, Je-Hyun
    • Proceedings of the KSME Conference
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    • pp.416-421
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    • 2000
  • The performance of gas turbine engines is affected by instabilities, like as rotating stall and/or surge. Rotating Stall is a transient intermediate stage between normal flow and complete flow breakdown leading to engine surge. Rotating Stall is associated with large amplitude nonaxisymmetric flow variations rotating around the compressor annulus. This paper presents the evolutions of stall propagation in a compressor cascade by numerical analysis. The flow phenomena due to stall cells and propagation speed are examined using 2 dimensional Navier - Stokes equations.

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Experimental Study on the Aerodynamic Characteristics of a Counter-Rotating Axial Flow Fan (엇회전식 축류 펜의 공력 특성에 관한 실험적 연구)

  • Choe, Jin-Yong;Jo, Lee-Sang;Jo, Jin-Su;Won, Yu-Pil
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.2
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    • pp.201-210
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    • 2002
  • Experiments were done for performance and flow characteristics of a counter-rotating axial flow fan. Performance curves of a counter-rotating axial flow fan were obtained and compared by varying the blade pitch angles. The fan characteristic curves were obtained following the Korean Standard Testing Methods for Turbo Fans and Blowers (KS B 6311). The fan flow characteristics were measured using a five-hole probe and a slanted hot-wire. The velocity profiles between the hub and tip of the fans were measured and analyzed at the peak efficiency point. The peak efficiency of the counter-rotating axial flow fan was improved about 15% respectively, compared with the single rotating axial fan. The single rotating axial flow fan showed relatively law efficiency due to the swirl velocities behind rotor exit which produced pressure losses. The counter-rotating axial flow fan showed that the swirl velocity generated by the front rotor was eliminated by the rear rotor and the associated dynamic pressure is recovered in the from of the static pressure rise.

Experimental Study on the Unsteady Flow Characteristics of the Counter-Rotating Axial Flow Fan (엇회전식 축류팬의 비정상 유동특성에 관한 실험적 연구)

  • Cho, Lee-Sang;Choi, Hyun-Min;Kang, Jeong-Seek;Cho, Jin-Soo
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.305-310
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    • 2007
  • For the understanding of the complex flow characteristics in the counter-rotating axial flow fan, it is necessary to investigate the three-dimensional unsteady flow fields in the counter-rotating axial flow fan. This information is also essential for the prediction of the aerodynamic and acoustical characteristics of the counter-rotating axial flow fan. Experimental study on the three-dimensional unsteady flow in the counter-rotating axial flow fan is carried out at the design point(operating condition). Three-dimensional unsteady flow fields in the counter rotating axial flow fan are measured at the cross-sectional planes of the upstream and downstream of each rotor using the $45^{\circ}$ inclined hot-wire. Three-dimensional unsteady flow fields in the counter-rotating axial flow such as the wake, the tip vortex and the tip leakage flow are shown the form of the velocity vectors and the velocity contours.

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Similarity analysis of a forced uniform flow impinging on a rotating disk in a vapor deposition process (증착공정에서의 회전원판 정체점유동에 대한 상사해석)

  • Song, Chang-Geol;Hwang, Jeong-Ho
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.3
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    • pp.371-379
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    • 1997
  • A theoretical study for a forced uniform flow impinging on a rotating disk, typically involved in Chemical Vapor Deposition(CVD) and Vapor-phase Axial Deposition(VAD) processes, has been carried out. A set of exact solutions for flow and temperature fields are developed by employing a similarity variable obtained from force balance on a control volume near the disk. The solutions depend on the rotating speed of the disk, .omega., and the forced flow speed toward the disk, a. For constant forced flow speed, the overall boundary layer thickness decreases when the rotating speed increases. Approximately 5%, 15%, and 30% decreases of the thickness are obtained for .omega./a = 2, 5, and 10, respectively, compared to the case of .omega./a = 0 (axisymmetric stagnation point flow). For constant rotating disk speed the boundary layer thickness immediately decreases as the forced flow speed increases, compared to the case of .omega./a .rarw. .inf. (induced flow near a rotating disk). Effects of .omega. and a on heat transfer coefficient are studied and explained with the boundary layer characteristics.

Numerical Simulation toy Flow Disturbance Between 3.5' Co-rotating Disks Unobstructed in Shroud (장애물이 없는 3.5' 동시회전 디스크의 유동교란에 관한 수치적 연구)

  • Kong Dae-Wee;Joo Won-Gu
    • 정보저장시스템학회:학술대회논문집
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    • pp.242-245
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    • 2005
  • The rotating flow in the space between co-rotating disks is of considerable importance in information storage systems. Hard disk drivers(HDD) in computer are used extensively as data storage capacity. The trend in the computer industry to produce smaller disk drives rotating at higher speed requires an improved understanding of fluid motion in the space between disks. In this study, we have tried LES model for inner-disk flowfield to investigate the flow disturbance and the flow structure driven by co-rotating disks. The boundary pattern between inner region and outer region obtained lobe-shape structure clearly and its number has been validated on experimental data by our previous study. We obtain the spectra of velocity and pressure components with several frequencies. We revealed there are two kinds of disturbances, one is global wave propagation and another is local wave propagation on Ekman boundary layer.

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Numerical analyses on the Aerodynamic Characteristics of a Counter-rotating Axial Flow Fan (고성능 엇회전식 축류팬의 공력특성에 대한 전산해석)

  • Cho, Leesang;Cho, Jinsoo
    • Journal of Institute of Convergence Technology
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    • v.5 no.1
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    • pp.37-40
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    • 2015
  • Numerical analyses on the aerodynamic characteristics of a counter rotating axial flow fan is carried out using the frequency domain panel method. Front rotor and rear rotor blades of a counter rotating axial fan are designed by using the simplified meridional flow analysis method with the radial equilibrium equation and the free vortex design condition, according to design requirements. Performance characteristics of a counter rotating axial flow fan are estimated for the variation of design parameters such as the hub to tip ratio, the taper ratio and the solidity. Pressure losses were higher at leading edge and hub region of rotor blades. Characteristic curve of the counter rotating fan was overpredicted without consideration of viscous effect.

Experimental Study on the Three Dimensional Unsteady Flow in a Counter-Rotating Axial Flow Fan (엇회전식 축류팬의 3차원 비정상 유동에 관한 실험적 연구)

  • Park, Hyun-Soo;Cho, Lee-Sang;Cho, Jin-Soo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.9
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    • pp.1005-1014
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    • 2004
  • Experiments were done for the three dimensional unsteady flow in a counter-rotating axial flow fan under peak efficiency operating condition. Flow fields in a counter rotating axial flow fan were measured at cross-sectional planes of the upstream and downstream of each rotor. Cross sectional flow patterns were investigated through the acquired data by the 45$^{\circ}$ inclined hot-wire. Flow characteristics such as tip vortex, secondary flow and tip leakage flow were confirmed through axial, radial and tangential velocity vector plot. It has been found that the radial and tangential velocity components disappeared, while the axial velocity component highly increased as soon as the tip vortex was generated. It has been observed that secondary flow and turbulence intensity which were increased by the front rotor were dissipated passing through the rear rotor. As the result the energy loss of the counter rotating axial flow fan decreased at the downstream of rear rotor. Also, it has been verified that tip vortex pattern of the rear rotor was dampened because the tip vortex generated by front rotor was mixed with that of the rear rotor.

Ion Slip Effect on the Flow Due to a Rotating Disk with Heat Transfer

  • Attia Hazem Ali
    • Journal of Mechanical Science and Technology
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    • v.20 no.12
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    • pp.2197-2202
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    • 2006
  • The steady hydromagnetic flow due to a rotating disk is studied with heat transfer considering the ion slip. The governing equations are solved numerically using finite differences. The results show that the inclusion of the ion slip has important effects on the velocity distribution as well as the heat transfer.