• Title/Summary/Keyword: 난류해석기법

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Computational Investigation of Pintle Nozzle Flow (핀틀 노즐 유동장의 수치해석적 연구)

  • Kim, Joung-Keun;Lee, Ji-Hyung;Chang, Hong-Been
    • Journal of the Korean Society of Propulsion Engineers
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    • v.13 no.2
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    • pp.35-41
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    • 2009
  • Both the nozzle expansion ratio and the chamber pressure are simultaneously and continuously changed according to pintle movement, resulting in a different internal flow structure and flow separation characteristics. In this paper, the pintle position effect on nozzle flow structure and separation phenomena is analyzed by experimental-aided Computational Fluid Dynamic(CFD). Among the turbulent models for RANS(Reynold Averaged Navier Stokes) in Fluent, Spalart-Allmaras model is better agreement with the nozzle wall pressure distribution attained by cold-flow test than other models. And even if a conical nozzle is used, there is a shock structure similar to cap-shock pattern mainly occurred in contoured or shaped optimized nozzle because of internal shock generated from pintle tip flow separation.

A Study on Performance Improvement of Multi-stage Pump Applying CFD Analysis Technique (CFD해석기법을 적용한 다단펌프 성능향상에 관한 연구)

  • Kim, Sang-Yu;Kim, Jae-Yeol;GAO, JIACHEN
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.21 no.3
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    • pp.70-76
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    • 2022
  • Recently, the demand for ultra-precision processing has increased owing to the increase in the demand for high-performance ultra-precision optical parts in the fields of information technology (IT), bio, healthcare, aerospace, and future automobiles. In this study, a performance improvement of a multi-stage pump was achieved by improving the pump casing structure rather than using the existing performance improvement method. To verify the performance improvement, the CFD analysis reliability of the existing pump, Pump A, was verified using the FLUENT app in the analysis software ANSYS, and the pump casing was improved through the verified CFD analysis of Pump B. Therefore, we want to analyze the performance improvement.

The Study on Stability Channel Technology by Using Groyne in Alluvial Stream - Riverside Protection Techniques by Using Groyne - (충적하천에서 수제에 의한 안정하도 확보기술에 관한 연구 - 수제에 의한 하안보호 기법 -)

  • Park, Hyo-Gil;Jung, Sung-Soon;Kim, Chul-Moon;Ahn, Won-Sik;Jee, Hong-Kee
    • Journal of Wetlands Research
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    • v.13 no.1
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    • pp.79-94
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    • 2011
  • As demonstrated in study for non-submerged groynes, the flow field is predominantly two-dimensional, with mainly horizontal eddies. The eddies shed form the tips of the groynes and migrate in the flow direction. These eddies have horizontal dimensions in the order of tens of meters and time-scales in the order of minutes. In the standard flow simulations, these motions are usually not resolved, due to a too coarse grid, too large time steps and, more importantly, the use of inadequate turbulence modelling. using for example a k-${\varepsilon}$ model, it is necessary to introduce substantial modifications. Therefore simulation resolved in this study, were carried out using the DELFT-3D-MOR programme, which is part of the DELFT3D software package of WL/Delft Hydraulics and In this study, apply a two-dimensional depth-averaged model, taking an horizontal large eddy simulation(HLES). The bed morphology computed when using HLES, as well as the associated time-scale, is similar to what has been obseved in a field case. When using a mean-flow model with-out HELS, the bed morphology is less realistic and the morphological time-scale is much larger. This slow development is the result of neglecting(or averaging). the strong velocity fluctuations associated with the time-varying eddy formation.

Broadband Noise Prediction of the Ice-maker Centrifugal Fan in a Refrigerator Using Hybrid CAA Method and FRPM Technique (복합 CAA 방법과 FRPM 기법을 이용한 냉장고 얼음제조용 원심팬의 광대역 소음 예측)

  • Heo, Seung;Kim, Dae-Hwan;Cheong, Cheol-Ung
    • The Journal of the Acoustical Society of Korea
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    • v.31 no.6
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    • pp.391-398
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    • 2012
  • In this paper, prediction of centrifugal fan was conducted through combination the hybrid CAA method which was used to predict the fan noise with the FRPM technique which was used to generate the broadband noise source. Firstly, flow field surround the centrifugal fan was computed using the RANS equations and noise source region was deducted from the computed flow field. Then the FRPM technique was applied to the source region for generation of turbulence which satisfies the stochastic features. The noise source of the centrifugal fan was modeled by applying the acoustic analogy to the synthesized flow field from the computed and generated flow fields. Finally, the broadband noise of the centrifugal fan was predicted through combination the modeled noise source with the linear propagation which was realized using the boundary element method. It was confirmed that the proposed technique is efficient to predict the tonal and broadband noises of centrifugal fan through comparison with the measured data.

Design Optimization of A Multi-Blade Centrifugal Fan with Navier-Stokes Analysis and Response Surface Method (삼차원 Navier-Stokes 해석과 반응면기법을 이용한 원심다익송풍기의 최적설계)

  • Seo, Seoung-Jin;Kim, Kwang-Yong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.10
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    • pp.1457-1463
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    • 2003
  • In this paper, the response surface method using three-dimensional Navier-Stokes analysis to optimize the shape of a multi-blade centrifugal fan, is described. For numerical analysis, Reynolds-averaged Navier-Stokes equations with standard k - c turbulence model are transformed into non-orthogonal curvilinear coordinate system, and are discretized with finite volume approximations. Due to the large number of blades in this centrifugal fan, the flow inside of the fan is regarded as steady flow by introducing the impeller force models for economic calculations. Linear Upwind Differencing Scheme(LUDS) is used to approximate the convection terms in the governing equations. SIMPLEC algorithm is used as a velocity-pressure correction procedure. Design variables, location of cur off, radius of cut off, expansion angle of scroll and width of impeller were selected to optimize the shapes of scroll and blades. Data points for response evaluations were selected by D-optimal design, and linear programming method was used for the optimization on the response surface. As a main result of the optimization, the efficiency was successfully improved. It was found that the optimization process provides reliable design of this kind of fans with reasonable computing time.

Numerical analysis of Flow Characteristic Around an Automobile with Variation of Slant Angle of Rear End (후미경사각 변화에 따른 자동차주위 유동특성 해석)

  • 정영래;강동민;박원규
    • Transactions of the Korean Society of Automotive Engineers
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    • v.9 no.1
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    • pp.75-83
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    • 2001
  • In this paper, numerical analysis is used to find the effects of inclination of rear end on flow characteristic around an automobile. The reference slant angle of rear end is 28.6$^{\circ}$, the slant angle of rear end is decreased to 24$^{\circ}$, 26.6$^{\circ}$ and also increased to 31.6$^{\circ}$, 36.4$^{\circ}$. The 3-D incompressible Navier-Stockes equations are solved by the iterative time marching scheme. The computed surface pressure coefficients were compared with experimental results and a good agreement has been achieved. The A- and C-pillar vortex and other flow phenomena around the ground vehicle are evidently shown. The variation of aerodynamic coefficients of drag, lift with respect to inclination angle of rear end are systematically studied. The flow characteristic on the automobile surface with respect to change of inclination of rear end have been also studied.

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Dynamic Numerical Modeling for LOx Swirl Injector at Supercritical Conditions (초임계 상태에서의 LOx 스월 인젝터에 대한 동적 수치 모델링)

  • Kim, Kuk-Jin;Heo, Jun-Young;Kim, Jong-Chan;Sung, Hong-Gye
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2009.11a
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    • pp.42-46
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    • 2009
  • For understanding of high performance liquid rocket engine operating at high pressure, dynamic characteristics of liquid oxygen in a swirl injector operating at supercritical conditions has been numerically investigated. Turbulent numerical model is based on large eddy simulation and contains full conservation laws including Soave modification of Redlich-Kwong equation of state and Chung's model. Preconditioning method is applied to get an effective convergence rate. Numerical analysis results are compared with the one that ideal equation of state applied to. Differences of thermodynamic properties and mixing dynamics are investigated at liquid phase area inside injector and combustion chamber.

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Shape Design of Heat Transfer Surfaces with Angled Ribs Using Numerical Optimization Techniques (경사진 사각리브가 부착된 열전달면의 수치최적화기법을 이용한 형상설계)

  • Kim, Hong-Min;Kim, Kwang-Yong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.9
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    • pp.1051-1057
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    • 2004
  • A numerical optimization procedure for the shape of three-dimensional channel with angled ribs mounted on one of the walls to enhance turbulent heat transfer is presented. The response surface method is used as an optimization technique with Reynolds-averaged Wavier-Stokes analyses of flow and heat transfer. SST turbulence model is used as a turbulence closure. Computational results for local heat transfer rate show reasonable agreements with experimental data. The pitch-to-height ratio of the rib and rib height-to-channel height ratio are set to be 9.0 and 0.1, respectively, and width-to-rib height ratio and attack angle of the rib are chosen as design variables. The objective function is defined as a linear combination of heat-transfer and friction-loss related terms with weighting factor. Full-factorial experimental design method is used to determine the data points. Optimum shapes of the channel have been obtained in the range from 0.0 to 0.1 of weighting factor.

A Stochastic Control for Nonlinear Systems under Random Disturbance Based on a Fluid Motion (유체운동에 의한 불규칙 가진을 받는 비선형계의 확률제어)

  • Oh, Soo-Young;Kim, Yong-Kwan;Cho, Lae-Kyoung;Choi, Young-Seob;Heo, Hoon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.05a
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    • pp.892-896
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    • 2001
  • Investigation is performed on the stability of nonlinear system under turbulent fluid motion modelled as white noise random process, which is a preliminary result in the course of research on the characteristic and nonlinear control of the stochastic system. Adopted physical model is beam-type structure with tip-mass and main base mass. The governing equation is derived via F-P-K approach in stochastic sense. By means of Gaussian Closure method infinite dynamic moment equations due to system nonlinearity is closed to finite one. At the best of authors' knowledge, it is the first trial to design nonlinear controller by using of sliding mode technique in stochastic domain and control performance and effect in stochastic domain is studied.

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Numerical Study for Design of Center-body Diffuser (Center-body 디퓨져 형상설계를 위한 수치적연구)

  • Kim, Jong Rok;Kim, Jae-Soo
    • Journal of the Korean Society of Propulsion Engineers
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    • v.18 no.3
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    • pp.34-39
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    • 2014
  • A study is analyzed on the design factor of center-body diffuser and performed on conceptual design of center-body diffuser with computational fluid dynamic. The flow field of center-body diffuser is calculated using axisymmetric two-dimensional Navier-Stokes equation with $k-{\epsilon}$ turbulencemodel. The center-body diffuser is compared with second throat exhaust diffuser in terms of starting pressure, the degree of vacuum pressure and the design factors. The counter flow jet on cone-tip of the center-body is applied for thermal protection system in the center-body diffuser.