• Journal of ILASS-Korea
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• v.23 no.2
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• pp.49-57
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• 2018

Numerical study under single-injection on bi-swirl coaxial injectors with different recess lengths was performed using ANSYS Fluent. The bi-swirl coaxial injectors which consisted of inner closed-type and outer open-type swirl injectors, had three different recess lengths. By changing mass flow rates, numerical simulation was repeated using the Reynolds stress BSL turbulent model. The numerical results such as discharge coefficient and spray angle were compared with previous experimental data and were found to be approximately matched well with them, irrespective of recess length. Quantitative data which was hard to be measured from experiments, were successfully obtained through the present numerical study.

• The KSFM Journal of Fluid Machinery
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• v.9 no.4 s.37
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• pp.36-42
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• 2006

In the present work, characteristics of the flow in the cage of a steam turbine bypass control valve for thermal power plant are investigated. Experimental measurement for wall static pressure has been carried out to validate numerical solutions. And, the flowfield is analyzed by solving steady three-dimensional Reynolds-averaged Navier-Stokes equations. Shear stress transport (SST) model is used as turbulence closure. The effects of the flow area between stages of the cage on the pressure drop are also found.

• The KSFM Journal of Fluid Machinery
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• v.13 no.1
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• pp.17-22
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• 2010

In this paper, numerical study on a mixed-flow pump for irrigation and drainage has been performed based on three-dimensional viscous flow analysis. Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model are discretized by finite volume approximations and solved by the commercial CFD code ANSYS CFX-11.0. A structured grid system is constructed in the computational domain, which has O-type grids near the blade surfaces and H/J-type grids in other regions. The numerical results were validated with experimental data for the heads and efficiencies at different flow coefficients. The efficiency at the design flow coefficient is evaluated with the variation of two geometric variables related to area of discharge and length of the vane in the diffuser. The results show that efficiency of the mixed-flow pump at the design flow coefficient is improved by the modifications of the geometry.

• Proceedings of the KIEE Conference
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• 1998.11b
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• pp.713-716
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• 1998

To examine the influence of unsteady wake on the flow and heat transfer characteristics, an experiment has been conducted in a four-vane linear cascade. Flow and heat transfer measurements are made for the inlet Reynolds number of 66000(based on chord length and free-stream velocity). Turbulent intensity and stress were measured using hot wire anemometer, and to measure the convective heat transfer coefficients on the blade surfaces liquid crystal/gold film Intrex technique was used. The disturbance by the unsteady wake is characterized by the unresolved unsteadiness. The unsteady wake enhances the turbulent motion of flow in the cascade passage. It also promotes the boundary layer development and transition. The results show that heat transfer coefficients on the suction surface increase with increasing unresolved unsteadiness.

• Journal of computational fluids engineering
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• v.12 no.4
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• pp.85-89
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• 2007

In the present work, flow analysis has been performed for side channel type double stage ring blower by solving three-dimensional Reynolds-averaged Navier-Stokes equation. Shear stress transport model is used as turbulent closure. The commercial CFD code CFX 11.0 is used for the calculations. Each of two stage is calculated separately and the second stage inlet flow is same as the first stage outlet flow so that consecutive calculation is possible. Velocity and pressure fields have been analyzed at the mid-plane between blades. The numerical results are validated with experimental data for head coefficients at different flow coefficients.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.2
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• pp.216-225
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• 1999

Four turbulent $k-{varepsilon}$models(i.e standard model modified models with streamline curvature modification and/or preferential dissipation modification) are applied in order to analyze the tur-bulent flow of wall-attaching offset jet. The upwind numerical scheme was adopted in the present analyses. The streamline curvature modification results in slightly better prediction while the preferential dissipation modification does not. The obtained analytic results will be used as refer-ences for further study regarding Reynolds stress model. In addition this paper introduced a method of increasing nozzle outlet velocity gradually for numercal convergence. Even though the method was simple it was efficient in view of convergent speed CPU running time computer memory storage programming etc.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2440-2443
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• 2008

This paper presents a three dimensional shape optimization procedure for a low-speed axial flow fan blade with a weighted average surrogate model. Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model are discretized by finite volume approximations. Six variables from airfoil profile and lean are selected as design variables. 3D RANS solver is used to evaluate the objective functions of total pressure efficiency. Surrogate approximation models for optimization have been employed to find the optimal design of fan blade. A search algorithm is used to find the optimal design in the design space from the constructed surrogate models for the objective function. The total pressure efficiency is increased by 0.31% with the weighted average surrogate model.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2729-2732
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• 2008

Cylindrical film-cooling hole is formulated numerically and optimized to enhance film-cooling effectiveness. The Kriging method is used an optimization technique with Reynolds-averaged Navier-Stokes analysis of fluid and heat transfer with shear stress transport model. The hole length-to-diameter ratio and injection angle are chosen as design variables and spatially averaged film-cooling effectiveness is considered as objective function which is to be maximized. Twelve training points obtained by Latin Hypercube Sampling for two design variables. Optimum shape shows the film-cooling effectiveness increased.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.12
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• pp.954-962
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• 2008

This study presents a numerical procedure to optimize the shape of cylindrical cooling hole to enhance film-cooling effectiveness. The RBNN method is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer with shear stress transport turbulent model. The hole length-to-diameter ratio and injection angle are chosen as design variables and film-cooling effectiveness is considered as objective function which is to be maximized. Twelve training points are obtained by Latin Hypercube Sampling for two design variables. In the sensitivity analysis, it is found that the objective function is more sensitive to the injection angle of hole than the hole length-to diameter ratio. Optimum shape gives considerable increase in film-cooling effectiveness.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.704-708
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• 2017

A spray characteristics is carried out in a numerical simulation of swirl coaxial injector. The water and nitrogen are the oxidizer and fuel is used in cold flow condition. The simulation is carried out in 3d model with varying recess length. Reynolds stress turbulence and volume of fluid model were chosen to perform the simulation. The spray characteristics have been investigated as well as the influence of the inlet swirl strength of the internal flow. Effect of recess length is studied for the axial and radial velocity decreased with a reduced length of inner injector due to the decline vortex intensity.