• Journal of computational fluids engineering
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• v.17 no.3
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• pp.53-58
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• 2012

Steady flow simulations through a high pressure turbine guide vanes were carried out. The main objective of the present work is to study the performance of turbulence models on the steady flow prediction from aerodynamic and aerothermal points of view. Three turbulence models were compared, namely SST, k-${\omega}$ and ${\omega}$-Reynolds stress models. The laminar results were also compared. The comparison was done with emphasis on the isentropic Mach number and heat transfer coefficient along the blade, and total pressure loss in the wake region. The calculated isentropic Mach number showed reasonable agreement with experimental data along the blade surface for all three turbulent models. For the total pressure loss in the wake region, ${\omega}$-Reynolds stress model showed the best agreement with the experimental data. However, unless using an appropriate transition model, the heat transfer coefficients of all three turbulent models showed poor agreement with experimental data.

• Journal of computational fluids engineering
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• v.17 no.3
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• pp.11-17
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• 2012

In this study, aerodynamic analyses have been conducted for 4-Bladed Vertical-Axis Wind Turbine (VAWT) configuration and the results are compared with experimental data. Reynolds-averaged Navier-Stokes equation with LES turbulence model is solved for unsteady flow problems. In addition, the computation results by standard k-${\omega}$ and SST k-${\omega}$ turbulence models are also presented and compared. An experiment model of 4-Bladed VAWT model has been designed and constructed herein. Experimental tests for aerodynamic performance of the present VAWT model are practically conducted using the vehicle mounted testing system. Comparison results between the experiment and the computational fluid dynamics (CFD) analyses are presented in order to show the accuracy of CFD analyses using the different turbulent models.

• Journal of Power System Engineering
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• v.15 no.2
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• pp.31-36
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• 2011

The flow characteristics on the periodically arranged semi-circular ribs in a rectangular channel for turbulent flow have been investigated numerically. The aspect ratio of the rectangular channel was AR=5, the rib height to hydraulic diameter ratio was 0.07 and rib height to channel height ratio was e/H=0.117. The v2-f turbulence model and SST k-${\omega}$ turbulence model were used to find the flow characteristics of near the wall which are suited for realistic phenomena. The numerical analysis results show turbulent flow characteristics and pressure drop at the near the wall as observed experimentally. The results predict that turbulent kinetic energy(k) is closely relative to the diffusion of recirculation flow, and v2-f turbulence model simulation results have a good agreement with experimental.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.6
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• pp.61-68
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• 2002

Combustion characteristics of dual transverse injection of hydrogen in supersonic air flows were studied using computational methods. Three-dimensional Navier-Stokes with a non-equilibrium chemical reaction model and the k-$\omega$ SST turbulence model were used. A parametric study was conducted with the variation of the distance between two injectors. Combustion characteristics of dual injection are very different from those of single injection. The combustion characteristics of two injection flows are very different from each other, and the ignition and combustion characteristics of the rear injection flow are strongly influenced by those of the front injection flow. The increase of the distance between two injectors up to a specific distance results in the increase of burning rate. However, the increase of the distance over the specific distance gives no increase of burning rate but makes more losses of stagnation pressure. From the results it can be stated that there exists a distance between two injectors for optimum combustion characteristics.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.6
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• pp.53-60
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• 2002

Based on the analyses of the single transverse injection in supersonic flow fields, the mixing characteristics of dual transverse injection of hydrogen in supersonic air flow are studied with computational methods. Three-dimensional Navier -Stokes and the k-$\omega$ SST turbulence model were used. A parametric study is conducted with the variation of the distance between two injectors. The flow patterns and the mixing characteristics of two injection flows are very different from each other, and the flow patterns and the mixing characteristics of the rear injection flow are strongly influenced by those of the first injection flow. The increase of the distance between two injectors up to a specific distance results in the increase of mixing rate and penetration of fuel. However, the increase of the distance over the specific distance results in the decrease of mixing rate and penetration of fuel. From the results it can be stated that there exists a distance between two injectors for optimum mixing characteristics.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.383-387
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• 2017

A three dimensional numerical analysis has been conducted to analyze the effects of a pipe angle, connecting a combustion chamber and a pintle nozzle, and pintle position on pintle nozzle performance. The compressibility correction of $k-{\omega}$ SST turbulent model was implemented to precisely predict the characteristics of complex flow structures inside a supersonic pintle nozzle. Due to an 3-D asymmetric pintle nozzle configuration, complex helical flow streamlines and large flow separations were observed, which resulting in significant nozzle performance losses. As the angle of connection-tube decreases, the coefficient of performance increases and Since the flow structures are evidently changed to the pintle stroke position, the performance characteristics was analyzed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2000.11a
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• pp.20-20
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• 2000

2개의 경사 충격파와 하나의 수직 충격파로 초음속 유동을 압축하는 초음속 공기 흡입구의 수치적 연구를 수행하였다. 지배방정식으로는 Navier-Stokes방정식을 사용하였고 난류모델로는 SST 모델을 사용하였다. 지배방정식의 점성항 계산에는 중심차분법을 사용하였고 대류항 계산에는 풍상차분법인 Roe의 FDS기법을 MUSCL기법과 결합하여 이용하였다. 유한 체적법을 이용하여 차분된 방정식은 LU분할 기법을 이용한 완전 내재적 방법으로 2차 정확도 시간 적분으로 비정상 과정의 연구를 수행하였다. 흡입구 배압을 정해주어야 하는 어려움을 해결하기 위해 흡입구 후면에 노즐을 달고 노즐의 면적을 조절하여 배압이 형성되도록 하였다.(중략)

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.1
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• pp.72-78
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• 2008

In this study, advanced (fluid-structure interaction (FSI)) analysis system has been developed in order to predict turbine cascade performance with blade deformation effect due to aerodynamic loads. Intereference effects due to the relative movement of the rotor cascade with respect to the stator cascade are also considered. Reynolds-averaged Navier-Stokes equations with one equation Spalart-Allmaras and two-equation k-ω SST turbulence models are solved to accurately predict fluid dynamic loads considering flow separation effects. A fully implicit time marching scheme based on the (coupled Newmark time-integration method) with high artificial damping is efficiently used to compute the complex fluid-structure interaction problem. Predicted aerodynamic performance considering structural deformation effect of the blade shows somewhat different results compared to the case of rigid blade model. Cascade performance evaluations for different elastic axis positions are importantly presented and its aeroelastic effects are investigated.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.6
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• pp.18-28
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• 2016

Numerical analysis was conducted as a preliminary study for evaluating the dual bell nozzle. For future parametric studies, a dual bell nozzle was designed, and thereafter inlet condition, turbulence model, and the number of optimum grids were determined. Dual bell nozzle was designed based on the KSLV-II first stage nozzle. Inlet condition was determined to frozen flow model of non-reacting eight species by comparing with the design values. SST $k-{\omega}$ model turned out to be suitable as turbulence model. About 150 thousand of the grids were selected after grid sensitivity tests. Based on the results determined in this study, we plan to investigate performance gain of the KSLV-II by adopting a proposed dual bell nozzle.

• 한국전산유체공학회:학술대회논문집
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• 2001.10a
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• pp.51-57
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• 2001

The eddy viscosity turbulence models were applied to predict the flows through a cascade, and the prediction performances of turbulence models were assessed by comparing with the experimental results for a controlled diffusion(CD) compressor blade. The original $\kappa-\omega$ turbulence model and $\kappa-\omega$ shear stress transport(SST) turbulence model were used as two-equation turbulence model which were enhanced for a low Reynolds number flow and the Baldwin-Lomax turbulence model was used as algebraic turbulence model. Farve averaged Wavier-Stokes equations in a two-dimensional, curvilinear coordinate system were solved by an implicit, cell-centered finite-volume computer code. The turbulence quantities are obtained by lagging when the men flow equations have been updated. The numerical analysis was made to the flows of CD compressor blade in a cascade at three different incidence angles (40. 43.4. 46 degrees). We found the reversion in the prediction performance of original $\kappa-\omega$ turbulence model and $\kappa-\omega$ SST turbulence model when the incidence angie increased. And the algebraic Baldwin-Lomax turbulence model showed inferiority to two-equation turbulence models.