• 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.

• Bulletin of the Society of Naval Architects of Korea
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• v.8 no.2
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• pp.45-52
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• 1971

The object of this study is to determine theoretical ship form which minimises wave making resistance under given conditions and developes theoretical ship form planing. By employing the streamline tracing method 1967's Korean Standard Ship Form of 10,000 G.T. linear has been reformed and tested at towing tank of Inha Institute of Technology. The design process and the reformed ship forms had been reported already in reference[4]. In this paper, resistance performance is experimentally observed with three models(original, theoretical, and reformed form) of 2m long in the towing tank, and total resistance of theoretical and reformed ship forms are decreased by 24.9% and 19.7% and wave making resistance by 66.4% and 47.7% compare to original ship form respectively.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.7
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• pp.621-627
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• 2008

Aerodynamic data measured in a wind tunnel has inevitable errors due to the presence of the wind tunnel walls. These unwanted interference effects must be corrected for the wall interference free aerodynamic data. Streamline curvature effects are caused by straightening of streamlines due to wind tunnel walls. Classical Glauert's correction method that is a standard method for fixed wing aircraft is not suitable for rotary wing aircraft. In this paper, Heyson's correction method of which wake model is compatible with rotors is used to correct the rotor shaft angle as well as the dynamic pressure. The results of Heyson's method are compared with Glauert's correction method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.6
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• pp.9-15
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• 2004

In this study the development of the two dimensional flowfield around an impulsively translated circular cylinder is numerically simulated using the diffusion vortex method. A detailed streamline pattern of fore wake and main wake of Re=1200, 9500 flowfields are investigated. The results of streamline pattern, the size of main wake and the axial velocities along the rear symmetry axis of the circular cylinder show good agreement with the reported experimental results. The long term wake delvelopment for Re=1200 flowfield was calculated up to ${\tau}=50$. The vortex shedding frequency shows the similar value as that of reported.

• The KSFM Journal of Fluid Machinery
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• v.3 no.3 s.8
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• pp.31-40
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• 2000

A computer program is developed for the prediction of the aerodynamic performance and the noise characteristics in the basic design step of axial flow fan. The flow field and the performance of fan are analyzed by using the streamline curvature computing scheme with total pressure loss and flow deviation models. Fan noise is assumed to be generated due to the pressure fluctuations induced by wake vortices of fan blades and to radiate via dipole distribution. The vortex-induced fluctuating pressure on blade surface is calculated by combining thin airfoil theory and the predicted flow field data. The predicted performances, sound pressure level and noise directivity patterns of fan by the present method are favorably compared with the test data of actual fan. Furthermore, the present method is shown to be very useful in optimizing design variables of fan with high efficiency and low noise level.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.3
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• pp.290-298
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• 2005

A study of design and analysis for the POD type waterjet is conducted. The analysis and design of waterjet system are more difficult than that of conventional propulsor because waterjet is complicatedly composed of many parts which are impeller, stator, inlet, nozzle, etc. The streamline method is traditionally used in the design of pump whose characteristics are similar to those of waterjet. This streamline method, however, has some limitation in analysis of a viscous flow as well as the interaction of inlet part of hull. In the present study, the developed CFD program is applied to the analysis of POD type waterjet. The developed program is first validated by comparing the existed experimental results. The designed waterjet system is also analyzed by the developed CFD program and analyzed results show that the performance of the present POD type waterjet is above the requirement.

• Journal of the korean Society of Automotive Engineers
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• v.10 no.2
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• pp.61-69
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• 1988

The finite-difference three-dimensional boundary layer procedure of Chang and Patel is modified and applied to solve the boundary layer development on the automobile surface. The inviscid pressure distribution needed to solve the boundary layer equations is obtained by using a low order panel method. The plane of symmetry boundary layer exhibits the strong streamline divergence up to the midbody and convergence thereafter. The streamline divergence in front of the windshield helps the boundary layer to overcome the sever adverse pressure gradient and avoid the separation. The relaxation of the pressure right after the top of the wind-shield, on the other hand, makes the overly thinned boundary layer to readjust and prompts the streamlines to converge into the symmetry plane before the external streamlines do. The three-dimensional characteristics are less apparent after the midbody and the boundary layer is similar to that of the two-dimensional flow. The results of the off-plane-of-symmetry boundary layer are also presented.

• 한국연소학회:학술대회논문집
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• 2004.06a
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• pp.7-14
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• 2004

The lift-off characteristics of the triple flame have been studied experimentally with various mean velocities and concentration gradients using a multi-slot burner, which can control the concentration gradient and the mean velocity independently, Lift-off height, axial maximum velocity, flame temperature, and some other characteristics were examined for methane and propane flame, It was found that minimum values of the lift-off heights exist at a certain concentration gradient for constant mean velocity, and this result implies that the propagation velocity has a maximum value at this condition, OH radical distribution was measured with LIF method and velocity variation along streamline was measured with PlV system. In addition maximum temperature along streamline was measured with CARS system. The intensity of the diffusion flame affects on the propagation velocity of triple flame in the region of very weak concentration gradient.

• The KSFM Journal of Fluid Machinery
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• v.6 no.2 s.19
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• pp.41-46
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• 2003

The hydraulic design optimization and performance analysis of mixed-flow pumps for waterjet marine vehicle propulsion has been carried out using mean streamline analysis and three-dimensional computational fluid dynamics (CFD) code. In the present study, the conceptual design optimization has been formulated with a non-linear objective function to minimize the fluid dynamic losses, and then the commercial CFD code was incorporated to allow for detailed flow dynamic phenomena in the pump system. Newly designed mixed-flow model pump has been tested in the laboratory. Predicted performance curves by the CFD code agree very well with experimental data for a newly designed mixed-flow pump over the normal operating conditions. The design and prediction method presented herein can be used efficiently as a unified hydraulic design process of mired-flow pumps for waterjet marine vehicle propulsion.

• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.110-115
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• 2000

The mean streamline analysis using the empirical loss correlations has been developed for performance prediction of industrial mixed-flow fan impellers in the present study. New simple, but effective, models for the additional Euler input work characteristic and an internal recirculation loss due to internal flow reversal under the low flowrate conditions are proposed in this paper. Comparison of overall performance predictions with six sets of test data of mixed-flow fans is accomplished to demonstrate the accuracy of the proposed models. Predicted performance curves by the present set of loss models agree fairly well with experimental data for a variety of mixed-flow fan impellers over the entire operating conditions. The prediction method presented herein can be used efficiently in the conceptual design phase of mixed-flow fan impellers.