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On the Thick Axisymmetric Boundary Layer and Wake Around the Body of Revolution (몰수분의 두꺼운 경계층 및 반류해석)

  • Gang, Sin-Hyeong;Hyeon, Beom-Su;Lee, Yeong-Gil
    • 한국기계연구소 소보
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    • s.9
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    • pp.141-151
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    • 1982
  • An iterative procedure for the calculation of the thick axisymmetric boundary layer and wake near the stern of a body of revolution is presented. Procedure consists of the potential flow calculation by a method of the integral equation of first kind and the calculation of boundary layer and wake by a differential me¬thod of the boundary layer theory. Additionally, higher order terms are included in the conventional momentum equations and continuity equation for the consider¬ation of the characteristics of axisymmetric flow different from the one of two dimentional flow and the thick boundary layer. These solutions are matched at the edge of boundary layer and wake. The results obtained by the present me¬thod are compared with the experimental data and it is found that the nominal wake distribution at the propeller plane of a axisymmetric body is in good agree¬ment with the experiment.

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An Analysis of BVI Unsteady Rotor Aerodynamics using Unsteady Panel and Time-Marching Free Wake (비정상 패널 및 시간전진 자유후류를 이용한 BVI 비정상 로터 공력 해석)

  • Wie, Seong-Yong;Lee, Duck-Joo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.37 no.4
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    • pp.329-335
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    • 2009
  • The unsteady panel and time-marching free wake are applied to the rotor aerodynamics and wake behaviour. Numerical results of panel and free wake are compared and validated with experimental data. Using these methods, unsteady rotor aerodynamics in BVI condition is analyzed and discussed in detail.

Improved version of LeMoS hybrid model for ambiguous grid densities

  • Shevchuk, I.;Kornev, N.
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.10 no.3
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    • pp.270-281
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    • 2018
  • Application of the LeMoS hybrid (LH) URANS/LES method for the wake parameters prediction is considered. The wake fraction coefficient is calculated for inland ship model M1926 under shallow water conditions and compared to results of PIV measurements. It was shown that due to lack of the resolved turbulence at the interface between LES and RANS zones the artificial grid induced separations can occur. In order to overcome this drawback, a shielding function is introduced into LH model. The new version of the model is compared to the original one, RANS $k-{\omega}$ SST and SST-IDDES models. It is demonstrated that the proposed modification is robust and capable of wake prediction with satisfactory accuracy.

An Experimental Study on the Heat Transfer Characteristics of Corrugated Impinging Jets (파형 충돌분류의 열전달 특성에 관한 실험적 연구)

  • Kim, Ye Yong;Kim, Kui Soon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.23 no.3
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    • pp.320-329
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    • 1999
  • An experimental study has been performed to investigate the heat transfer characteristics of impinging jets with corrugated nozzle and wake generation plate. Three different shapes of corrugated nozzle and five different shapes of wake generation plate were tested to improve the heat transfer characteristics of impinging jet. Heat transfer coefficients were obtained by using transient method based on the liquid crystal thermography. The effects of corrugated nozzle and wake generation plate on the heat transfer characteristics of impinging jets were discussed in detail. The results showed that both the corrugated nozzle and the wake generation plate improved the heat transfer characteristics of impinging jet. Especially, heat transfer coefficients around stagnation region of impinging jets were highly increased.

PIV Velocity Field Measurements of Flow around a Ship with Rotating Propeller (PIV를 이용한 선박 프로펠러 후류의 속도장 계측)

  • 이상준;백부근
    • Journal of the Society of Naval Architects of Korea
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    • v.40 no.5
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    • pp.17-25
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    • 2003
  • Velocity field behind a container ship model with a rotating propeller has been investigated using PIV (particle image velocimetry) system. Four hundred instantaneous velocity fields were measured at 4 different blade phases and ensemble-averaged to investigate the spatial evolution of vortical structure of near wake within one propeller diameter downstream. The phase-averaged mean velocity fields show the potential wake and the viscous wake formed due to the boundary layers developed on the blade surfaces. The interaction between bilge vortex developed along the hull surface and the tangential velocity component of incoming flow causes to have asymmetric flow structure in the transverse plane.

Turbulent Flow Field on Boundary Layer Flow Conditions in the Near-Wake of a Flat Plate (평판 근접 후류에서 경계층의 유동조건에 따른 난류유동장)

  • Kim, D.H.;Chang, J.W.
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.12 no.3
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    • pp.25-39
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    • 2004
  • An experimental study was quantitatively carried out in order to investigate the influence of flow conditions on a boundary layer in the near-wake of a flat plate. Tripping wires attached at various positions were selected to change flow conditions of a boundary layer in the vicinity of trailing edge. The flows such as laminar, transitional, and turbulent boundary layer at 0.98C from the leading edge are imposed to investigate the evolution of symmetric and asymmetric wake. Measurements were made at freestream velocity of 6.0m/s, and the corresponding Reynolds number is $2.8{\times}10^5$. An x-type hot-wire probe(55P61) was employed to measure at 8 stations in the near-wake region. Test results show that the near-wake of the flat plate for the case of a laminar and transitional boundary layer is sensitive to mean flow shear generated after separation but for the case of turbulent boundary layer is insensitive.

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Potential Based Prediction Methods of Aerodynamic and Wake Simulation of Wind Turbine Blade (포텐셜 유동을 기반으로 한 풍력 터빈 블레이드의 공력 해석 및 후류 예측 기법에 관한 연구)

  • Kirn, Ho-Geon;Shin, Hyung-Ki;Lee, Soo-Gab
    • 한국신재생에너지학회:학술대회논문집
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    • 2007.06a
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    • pp.414-419
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    • 2007
  • This paper describes the prediction of aerodynamic performance and wake of HAWT in normal and yawed flow operation using potential based methods. In order to analyze aerodynamic performance of wind turbine WINFAS program is used, which is based on VLM(Vortex Lattice Method) and CVC(Constant vorticity contour) Free wake model. Some problems of CVC vortex filament method are investigated arid to improve these problems vortex ring wake are introduced in behalf of CVC vortex filament. The prediction results using the vortex lattice wake are compared to experimental data.

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Study on Wake Roll-Up Behavior Behind Wings In Close Proximity to the Ground

  • Han, Cheol-Heui;Cho, Jin-Soo
    • International Journal of Aeronautical and Space Sciences
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    • v.3 no.2
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    • pp.76-81
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    • 2002
  • A numerical simulation of wake behavior behind three-dimensional wings in ground effect is done using an indirect boundary element method (Panel Method). An integral equation is obtained by applying Green's 2nd Identity on all surfaces of the flow domain. The AIC is constructed by imposing the no penetration condition on solid surfaces, and the Kutta at the wing's trailing edge. The ground effect is included using an image method. At each time step, a row of wake panels from wings' trailing edge are convected downstream following the force-free condition. The roll-up of wake vortices behind wings in close proximity is simulated.

Bubble Wake Measurement by Acoustic Bubble Spectrometer Generated by Planing Hull at Circulating Water Channel (회류수조에서의 ABS에 의한 활주선 후류 기포항적계측)

  • Shin, Myung-Soo;Moon, Il-Sung;Nah, Young-In;Park, Jong-Chun
    • Journal of the Korea Institute of Military Science and Technology
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    • v.14 no.1
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    • pp.55-61
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    • 2011
  • This paper presents bubble wake measurement results generated by the planing hull. The bubble was generated by SNAME TMB model(No. 4876) with hard chine at the CWC(Circulating Water Channel). ABS(Acoustic Bubble Spectrometer) was used to measure bubble wake measurement. The manufactured model is one meter in length and uniform velocity to generate the bubble at CWC is 3m/s, relatively higher speed than conventional hull form. Measurements were performed successfully and measured results show well the general characteristics of bubble wake generated by planing hull. Furthermore, experimental equations are proposed for the practical use.

Visualization of Turbulent Flow around a Sphere (구 주위 난류유동에 관한 가시화 연구)

  • Jang, Young-Il;Lee, Sang-Joon
    • 유체기계공업학회:학술대회논문집
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    • 2006.08a
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    • pp.401-402
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    • 2006
  • The turbulent flow around a sphere was investigated using two experimental techniques: smoke-wire flow visualization in wind tunnel at Re=5300, 11000 and PIV measurements in a circulating water channel. The smoke-wire visualization shows flow separation points near an azimuthal angle of $90^{\circ}$, recirculating flow, transition from laminar to turbulent shear layer, evolving vortex roll-up and fully turbulent eddies in the sphere wake. The mean velocity field measured using a PIV technique in x-y center plane demonstrates the detailed near-wake structure such as nearly symmetric recirculation region, two toroidal vortices, laminar separation, transition and turbulent eddies. The PIV measurements of turbulent wake in y-z planes show that a recirculating vortex pair dominates the near-wake region.

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