• 제목/요약/키워드: tip vortex

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프로펠러팬에서의 Tip Vortex 거동 (Behavior of Tip Vortex in a Propeller Fan)

  • 김성협;고천아인;정상아홍
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2004년도 추계학술대회
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    • pp.1377-1382
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    • 2004
  • Flow fields in a half ducted propeller fan have been investigated by three-dimensional Reynolds-averaged Navier-Stokes (RANS) simulations and a vortex core identification technique. The simulation at the design operating condition shows that the tip vortex onset point is located at 30 percent tip chord of the suction surface on the blade tip. There is no interaction between the tip vortex and the adjacent blade, so that the tip vortex smoothly convects to the rotor exit. However, the high vorticity in the tip vortex causes the wake and the tip leakage flow to be twined around the tip vortex and to interact with the pressure surface of the adjacent blade. This flow behavior corresponds well with experimental results by Laser Doppler Velocimetry. On the contrary, the simulation at the low-flowrate operating condition shows that the tip vortex onset point is located at the 60 percent tip chord of the suction surface. In contrast to the design operating condition, the tip vortex grows almost tangential direction, and impinges directly on the pressure surface of the adjacent blade.

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전향 축류형 홴에서의 익단 누설 유동 구조 (Structure of Tip Leakage Flow in a Forward-Swept Axial-Flow Fan)

  • 이공희;명환주;백제현
    • 대한기계학회논문집B
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    • 제27권7호
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    • pp.883-892
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    • 2003
  • The experiment using three-dimensional laser Dopperr velocimetery (LDV) measurements and the computation using the Reynolds stress model of the commercial code, FLUENT, were conducted to give a clear understanding on the structure of tip leakage flow in a forward-swept axial-flow fan operating at the maximum efficiency condition. The tip leakage vortex was generated near the position of the minimum wall static pressure, which was located at approximately 12% chord downstream from the leading edge of blade suction side, and developed along the centerline of the pressure trough within the blade passages. A reverse flow between the blade tip region and the casing, induced by tip leakage vortex, acted as a blockage on the through-flow. As a result, high momentum flux was observed below the tip leakage vortex. As the tip leakage vortex proceeded to the aft part of the blade passage, the strength of tip leakage vortex decreased due to the strong interaction with the through-flow and casing boundary layer, and the diffusion of tip leakage vortex caused by high turbulence. In comparison with LDV measurement data, the computed results predicted the complex viscous flow patterns inside the tip region, including the locus of tip leakage vortex center, in a reliable level.

풍력 발전기 블레이드에 걸친 3차원 유동장 해석 및 팁 형상 설계 (3-DIMENSIONAL FLOW FIELD ANALYSIS AND TIP SHAPE DESIGN IN A WIND TURBINE BLADE)

  • 정재호;유철;이정상;김기현;최재웅
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2011년 춘계학술대회논문집
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    • pp.243-248
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    • 2011
  • The 3-dimensional flow field has been investigated by numerical analysis in a 2.5MW wind turbine blade. Complicated and separated flaw phenomena in the wind turbine blade were captured by the Reynolds-averaged Navier-Stokes(RANS) steady flaw simulation using general-purpose code, CFX and the mechanism of vortex structure behavior is elucidated. The vortical flow field in a wind turbine rotor is dominated by the tip vortex and hub separation vortex. The tip vortex starts to be formed near the blade tip leading edge. As the tip vortex develops in the tangential direction, interacting with boundary layer from the blade tip trailing edge. The hub separation vortex is generated near the blade hub leading edge and develops nearly in the span-wise direction. Furthermore, 3-dimensional blade tip shape has been designed for increasing shrift power and reducing thrust force on the wind turbine blade. It is expected that the behavior of the tip vortex and hub separation vortex plays a major role in aerodynamic and aeroacoustic characteristics.

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축류 회전차 익말단 틈새유동에 대한 수치해석(II) - 틈새변화 및 영각변화에 따른 누설와류의 변화 - (Numerical Analysis on the Blade Tip Clearance Flow in the Axial Rotor (II) - Variation of Leakage Vortex with Tip Clearance and Attack Angle -)

  • 노수혁;조강래
    • 대한기계학회논문집B
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    • 제23권9호
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    • pp.1106-1112
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    • 1999
  • Substantial losses behind axial flow rotor are generated by the wake, various vortices in the hub region and the tip leakage vortex in the tip region. Particularly, the leakage vortex formed near blade tip is one of the main causes of the reduction of performance, generation of noise and aerodynamic vibration in downstream. In this study, the three-dimensional flow fields in an axial flow rotor were calculated with varying tip clearance under various flow rates, and the numerical results were compared with experimental ones. The numerical technique was based on SIMPLE algorithm using standard $k-{\varepsilon}$ model(WFM) and Launder & Sharma's Low Reynolds Number $k-{\varepsilon}$ model(LRN). Through calculations, the effects of tip clearance and attack angle on the 3-dimensional flow fileds behind a rotor and leakage flow/vortex were investigated. The presence of tip leakage vortex, loci of vortex center and its behavior behind the rotor for various tip clearances and attack angles was described well by calculation.

추진기 날개 끝 형상변화에 따른 보오텍스 유동에 대한 수치해석 (Numerical Analysis of a Tip Vortex Flow for Propeller Tip Shapes)

  • 박선호;서정화;김동환;이신형;김기섭
    • 대한조선학회논문집
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    • 제48권6호
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    • pp.501-508
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    • 2011
  • In order to control the tip vortex cavitation occurring around the tip of a rotating propeller blade, researches on the propeller cavitation and blade tip vortex flows have been increased. In this paper, the propeller tip vortex flow for a blunt and sharp tips was studied using an unsteady Reynolds-averaged Navier-Stokes equations solver based on a cell-centered finite volume method. In numerical open water test, torques, thrusts, pressure distributions and vortex flows were compared for various rotating speeds. To consider a hull wake, the nominal wake was specified in inlet boundary condition. Pressure distributions and vortex flows with the hull wake were investigated for various propeller rotating angles. From the results, it was confirmed that the blunt tip propeller delayed the tip vortex flow.

소산이 고려된 보오텍스 모델과 버블 이론을 이용한 수중익 날개 끝 보오텍스 캐비테이션 거동 및 소음의 수치적 해석 (Numerical Analysis of Tip Vortex Cavitation Behavior and Noise on Hydrofoil using Dissipation Vortex Model and Bubble Theory)

  • 박광근;설한신;이수갑
    • 대한조선학회논문집
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    • 제43권2호
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    • pp.177-185
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    • 2006
  • Cavitation is the dominant noise source of the marine vehicle. Of the various types of cavitation , tip vortex cavitation is the first appearance type of marine propeller cavitation and it generates high frequency noise. In this study, tip vortex cavitation behavior and noise are numerically investigated. A numerical scheme using Eulerian flow field computation and Lagrangian particle trace approach is applied to simulate the tip vortex cavitation on the hydrofoil. Vortex flow field is simulated by combined Moore and Saffman's vortex core radius equation and Sculley vortex model. Tip vortex cavitation behavior is analyzed by coupled Rayleigh-Plesset equation and trajectory equation. The cavitation nuclei are distributed and released in the vortex flow result. Vortex cavitation trajectories and radius variations are computed according to nuclei initial size. Noise is analyzed using time dependent cavitation bubble position and radius data. This study may lay the foundation for future work on vortex cavitation study and it will provide a basis for proper underwater propeller noise control strategies.

Numerical Study on Flow Characteristics at Blade Passage and Tip Clearance in a Linear Cascade of High Performance Turbine Blade

  • Myong, Hyon-Kook;Yang, Seung-Yong
    • Journal of Mechanical Science and Technology
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    • 제17권4호
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    • pp.606-616
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    • 2003
  • A numerical analysis has been conducted in order to simulate the characteristics of complex flow through linear cascades of high performance turbine blade with/without tip clearance by using a pressure-correction based, generalized 3D incompressible Wavier-Stokes CFD code. The development and generation of horseshoe vortex, passage vortex, leakage vortex, tip vortex within tip clearance, etc. are clearly identified through the present simulation which uses the RNG k-$\varepsilon$ turbulent model with wall function method and a second-order linear upwind scheme for convective terms. The present simulation results are consistent with the generally known tendency that occurs in the blade passage and tip clearance. A 3D model for secondary and leakage flows through turbine cascades with/without tip clearance is also suggested from the present simulation results, including the effects of tip clearance height.

Evolution of Tip Vortices Generated by Two Bladed Rotor in Hover at Early Wake Ages

  • Park, Byung-Ho;Han, Yong-Oun
    • International Journal of Aeronautical and Space Sciences
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    • 제10권2호
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    • pp.106-116
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    • 2009
  • In order to investigate change of vortex structures and its evolving proceses, two dimensional LDV system was used for measurement of velocity vectors of tip vortex, and PIV system was also used for visualizations of tip vortex array for two bladed rotor, respectively. Experiments provided vortex locations, tangential and axial velocity components of tip vortex at six wake ages of 9.5, 10.5, 60.5, 99.5, 129.5, 169.5 and corresponded six wake ages shifted with 180 degrees per each. It was resulted that tip vortices generated by the first blade satisfy Landgrebe's model for their vortex locations even after they were accelerated by the second blade in downstream. Tangential velocity components of tip vortices follow Vatistas' n=2 model on both inside and outside regions of rotor slipstream without loss of vortex circulation. Axial velocity profiles revealed that there were small but significant perturbations just outside the primary vortex core which implies the second blade affects the wake substantially. It was also found that tip paths of each blade were not willing to be coincided intrinsically.

유동가시화를 통한 타원형날개주위 유동연구 (Study on the Flow Around an Elliptic Wing Using Flow Visualization Technique)

  • 현범수;김문찬
    • 대한조선학회논문집
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    • 제30권1호
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    • pp.94-103
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    • 1993
  • NACA0020 단면을 갖는 타원형 날개끝에서 발생되어 전개되는 Tip Vortex를 연구하기 위하여 날개표면과 후류에서의 유동특성을 조사하였다. 날개표면 유동은 Tufts법과 캐비테이션 관찰로 분석되었으며 날개표면 압력계측으로 유동가시화 결과를 보완하였다. 연구결과 강력한 스팬방향 압력구배가 Tip Vortex 생성에 결정적 영향을 줌과 아울러 날개 양쪽면에서의 유동이 공히 보오텍스의 생성에 기여함을 알 수 있었다. 한편, 자세한 Tip Vortex의 구조를 보기위하여 캐비테이션 관찰, Laser Sheet 기법에 의한 보오텍스 단면가시화 및 유속계측이 실시되었는데 보오텍스의 형상과 강도는 날개의 받음각에 지배되어 나타났다. 날개끝 유동의 전반적인 특성은 비점성유동 가정하에서 사용되는 보오텍스 모델링을 보완할 목적으로 분석되었다.

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Blade Loading에 의한 팁와류의 특성 (Characteristics of Tip Vortex by Blade Loading)

  • 윤용상;송성진
    • 유체기계공업학회:학술대회논문집
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    • 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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    • pp.273-278
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    • 2002
  • The characteristics of tip vortex within a blade tip region were examined experimentally in various flow coefficients by the way of changing tip clearance and blade stagger angle in an axial Low Speed Research Compressor(LSRC). The objective was to identify the unsteady pressure distribution in the blade passage by ensemble average technique acquired from high-frequency response pressure transducers and the tip vortex by root mean square value(RMS value). Data were reduced statistically using phase-lock technique for detailed pressure distributions.

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