• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2162-2167
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• 2003

It is well-known that high anisotropic characteristic of turbulent flow field is dominant inside tip leakage vortex. This anisotropic nature of turbulence invalidates the use of the conventional isotropic eddy viscosity turbulence model based on the Boussinesq assumption. In this study, to check whether an anisotropic turbulence model is superior to the isotropic ones or not, the results obtained from steady-state Reynolds averaged Navier-Stokes simulations based on the RNG ${\kappa}-{\varepsilon}$ and the Reynolds stress model in two test cases, such as a linear compressor cascade and a forward-swept axial-flow fan, are compared with experimental data. Through the comparative study of turbulence models, it is clearly shown that the Reynolds stress model, which can express the production term and body-force term induced by system rotation without any modeling, should be used to predict the complex tip leakage flow, including the locus of tip leakage vortex center, quantitatively.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.318-323
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• 2005

To evaluate the accurate performance of turbomachinery, it is important to measure the unsteady flow phenomena downstream of the rotor blade. This paper presents the development of the fast-response total pressure probe for the measurement of the total pressure field at the exit of rotor and the result of measurement in a 1-stage axial turbine. The fast-response total pressure probe was fabricated by installing a fast-response pressure sensor near the head of a Kiel probe. And it measured the phase-lock averaged total pressure downstream of an 1-stage axial turbine. The developed probe successfully measured the accurate total pressure distribution at rotor exit and made possible to evaluate the loss distribution and the accurate performance of turbomachinery.

• The KSFM Journal of Fluid Machinery
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• v.5 no.2 s.15
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• pp.7-14
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• 2002

The effect of tip clearance is important part for turbomachinery performance. Tip leakage flow due to tip clearance is mixed with passage vortex. Large amount of loss is generated at the mixing region and overall performance of turbomachinery is reduced. Numerical calculation of the 1st stage rotor of GE7FA gas turbine is carried out to investigate tip clearance effect on performance, pitchwise variations of velocity profiles, pressure distributions and loss coefficients. A commercial code, CFX-TascFlow is validated in this study.

• International Journal of Fluid Machinery and Systems
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• v.4 no.1
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• pp.161-171
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• 2011

The availability of a high quality open source CFD simulation platform like OpenFOAM offers new R&D opportunities by providing direct access to models and solver implementation details. Efforts have been made by Hydro-Qu$\'{e}$bec to adapt OpenFOAM to hydroturbines for the development of steady-state capabilities. This paper describes the developments that have been made to implement new turbomachinery related capabilities: multiple frames of reference solver, domain coupling interfaces (GGI, cyclicGGI and mixing plane) and specialized boundary conditions. Practical use of the new turbomachinery capabilities are demonstrated for the analysis of a 195-MW Francis turbine.

• 유체기계공업학회:학술대회논문집
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• 1999.12a
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• pp.141-146
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• 1999

The comming of high speed computers with large memory size in recent years has allowed the practical development of codes which solve the Reynolds-averaged NAvier-Stokes (RANS) equations in three dimensions. Such codes are already used by the large engine manufacturers for the advanced design of some engine components. Different computational fluid dynamics approaches and turbulence models exist, and it seems essential today to establish their degree of validity for application to typical configurations in turbomachinery. In 1993 the Turbomachinery Committee of the IGTI of ASME has issued an open invitation to predict the flow details of an isolated transonic fan rotor called as NASA ROTOR 37. This paper reports this test case.

• International Journal of Fluid Machinery and Systems
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• v.9 no.4
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• pp.362-369
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• 2016

The shock-free inflow criterion applied in the development of two-dimensional cascade for turbomachinery design. The developed cascade analysis with potential flow calculation through a panel method has been used to determine the shock-free inflow condition. The combination between cascade analysis and PSO (particle swarm optimization) algorithm provides an opportunity to develop a diagram of a two-dimensional parameter cascade at various airfoil shapes. Analytical equations have been derived from the diagram that will facilitate the turbomachinery designer in applying the shock-free inflow criterion on their developed cascade. This method has been used to develop the very low head axial hydraulic turbine and provides excellent results of numerical and actual prototype performances.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.2
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• pp.313-324
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• 1992

Two-dimensional Navier-Stokes code has been developed for analysis of turbomachinery blade rows and other internal flows. The Navier-Stokes equations are written in a Cartesian coordinate system, then mapped into a generalized body-fitted coordinate system. All direction of viscous terms are incorporated and turbulent effects are modeled using the Baldwin-Lomax algebraic model. Equation are discretized using finite difference method on the C-type grids and solved using implicit LU-ADI decomposition scheme. Calculations are made at a VKI turbine cascade flow in a transonic wind-tunnel and compared to experimental data. Present numerical scheme is shown to be in good agreement with the previous experimental results and simulates the two-dimensional viscous flow phenomena.

• Journal of Power System Engineering
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• v.2 no.1
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• pp.39-44
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• 1998

Computational grids used in the numerical simulation of multi staged turbomachinery flow fields are generated. A multiblock structure simplifies the creation of structured H-grids about complex turbomachinery geometries and facilitate the creation of a grid for multi-row topologies. The numerical algorithm adopts the combination of the algebraic and elliptic method to create the internal grids efficiently and quickly. The input module is made of the results of the preliminary design, i.e., flow-path, aerodynamic conditions along the spanwise direction, and the blade profile data. The final grids generated from each module of the system are used as the preprocessor for the performance prediction of the single row cascades and the flow simulation inside the multi staegd blade passage. Application to low pressure compressor of industrial gas turbine engines was demonstrated to be very reliable and practical in support of design activities.

• Journal of Mechanical Science and Technology
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• v.19 no.8
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• pp.1632-1648
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• 2005

The effects of Reynolds number on the non-nulling calibration of a typical cone-type five-hole probe have been investigated for the representative Reynolds numbers in turbomachinery. The pitch and yaw angles are changed from - 35 degrees to 35 degrees with an angle interval of 5 degrees at six probe Reynolds numbers in range between $6.60{\times}10^3\;and\;3.17{\times}10^4$. The result shows that not only each calibration coefficient itself but also its Reynolds number dependency is affected significantly by the pitch and yaw angles. The Reynolds-number effects on the pitch- and yaw-angle coefficients are noticeable when the absolute values of the pitch and yaw angles are smaller than 20 degrees. The static-pressure coefficient is sensitive to the Reynolds number nearly all over the pitch- and yaw-angle range. The Reynolds-number effect on the total-pressure coefficient is found remarkable when the absolute values of the pitch and yaw angles are larger than 20 degrees. Through a typical non-nulling reduction procedure, actual reduced values of the pitch and yaw angles, static and total pressures, and velocity magnitude at each Reynolds number are obtained by employing the calibration coefficients at the highest Reynolds number ($Re=3.17{\times}10^4$) as input reference calibration data. As a result, it is found that each reduced value has its own unique trend depending on the pitch and yaw angles. Its general tendency is related closely to the variation of the corresponding calibration coefficient with the Reynolds number. Among the reduced values, the reduced total pressure suffers the most considerable deviation from the measured one and its dependency upon the pitch and yaw angles is most noticeable. In this study, the root-mean-square data as well as the upper and lower bounds of the reduced values are reported as a function of the Reynolds number. These data would be very useful in the estimation of the Reynolds-number effects on the non-nulling calibration.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.12
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• pp.1655-1666
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• 2003

It is experimentally well-known that high anisotropies of the turbulent flow field are dominant inside the tip leakage vortex, which is attributable to a substantial proportion of the total loss and constitutes one of the dominant mechanisms of the noise generation. This anisotropic nature of turbulence invalidates the use of the conventional isotropic eddy viscosity turbulence models based on the Boussinesq assumption. In this study, to check whether an anisotropic turbulence model is superior to the isotropic ones or not, the results obtained from the steady-state Reynolds averaged Navier-Stokes simulations based on the RNG k-$\varepsilon$ model and the Reynolds stress model (RSM) are compared with experimental data for two test cases: a linear compressor cascade and a forward-swept axial-flow fan. Through this comparative study of turbulence models, it is clearly shown that the RSM, which can express the production term and body-force term induced by system rotation without introducing any modeling, should be used to predict quantitatively the complex tip leakage flow, especially in the rotating environment.