• Journal of the Society of Naval Architects of Korea
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• v.36 no.4
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• pp.21-27
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• 1999

A low order panel method based on the perturbation potential is applied for prediction of performance of blown-flap rudders. In order to improve the solution behavior at the large angle of attacks, the geometry of the trailing wake sheet is computed by aligning freely with the local flow. The effect of the wake sheet roll-up is also included with use of a high order panel method. The flow in the gap between the main component and the flap of the rudder is modeled as Couette flow. The effects of the gap and the flow jet are included in application of a kinematic and a dynamic boundary condition on the inlet and the outlet of the gap as well as on the flap and the wake. The results with the present method are compared with existing experimental data. The method is shown to be capable of determining accurately the flow characteristics even for large flap angles.

• Journal of Ocean Engineering and Technology
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• v.4 no.1
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• pp.49-54
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• 1990

This study describes the application of a two dimensional depth integrated numerical model. The explict scheme of finite difference method had been applied to the model of circulation. The nonlinear terms showed a slight difference for the variations of water elevation when calculated grid was small. They were also found to be minor when calculated grid size was increased. For verification of the numerical model, numerical results were compared with predicted values and field data. In the model, the effect of nonlinear advective terms proved not to be significant.

• 한국전산유체공학회:학술대회논문집
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• 2000.05a
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• pp.91-98
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• 2000

The three-dimensional unsteady compressible Full Navier-Stokes equation solver with sliding multi-block method has been applied to analyze three dimensional characteristics of the flow field and compression wave around the high speed train which Is entering into a tunnel. The numerical scheme of AF + ADI was used to efficiently solve Navier-Stokes equations in the curvilinear coordinate system. The vortex formation around the nose region was found and the generation of compression wave due to the blockage effects was observed ahead of the train in the form of plane wave. The three dimensional characteristics of the flow field compared to the analytic results were discussed in detail. The variation of pressure of tunnel wall surface and velocity profile of the train are identified as the train enters into a tunnel. The changes in aerodynamic forces and streamlines of each specific sections are also discussed and presented.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.135-139
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• 2005

An unstructured overset mesh method has been developed for the simulation of unsteady viscous flow fields around multiple bodies in relative motion. For this purpose, a robust and fast search technique is proposed for both triangle and high-aspect quadrilateral cell elements. The interpolation boundary is defined for data communication between grid systems and an interpolation method is suggested for viscous and inviscid cell elements. This method has been applied to calculate the flow fields around 2-D airfoil including relative motion. Validation were made by comparing the predicted results with those of experiments or other researcher's numerical results. It was demonstrated that the present method is efficient and robust for the prediction of unsteady time-accurate flow fields involving multiple bodies in relative motion.

• Journal of computational fluids engineering
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• v.6 no.3
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• pp.19-26
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• 2001

An Eulerian-Lagrangian method, so called immersed boundary method, is used for analysing viscous flow around arbitrary bodies, where governing equations are discretized on a regular grid by using a finite volume method. To improve the accuracy of flow near body boundaries, a second-order accurate interpolation scheme is used and a level-set based grid deformation method is presented to construct the adaptive grids around body boundaries. The present scheme is used to simulate steady flow around a semicircular cylinder mounted on the bottom of flow domain and calculated results are validated by results of a body fitted grid method. Finally, present method is applied to a complex flow around multi body and the usefulness is checked by investigating calculated results.

• Journal of computational fluids engineering
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• v.14 no.3
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• pp.33-48
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• 2009

In the present study, a fast grid deformation technique has been incorporated into the unsteady compressible and incompressible viscous flow solvers on unstructured hybrid meshes. An algebraic method based on the basis decomposition of normal edge vector was used for the deformation of viscous elements, and a ball-vertex spring analogy was adopted for inviscid elements among several spring analogy methods due to its robustness. The present method was validated by comparing the results obtained from the grid deformation and the rigid motion of entire grids. Fish swimming motion of an NACA0012 airfoil and flapping wing motion of a generic fighter were also simulated to demonstrate the robustness of the present grid deformation technique.

• Journal of computational fluids engineering
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• v.18 no.3
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• pp.79-86
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• 2013

Preconditioned compressible Navier-Stokes equations are solved for almost incompressible flows. Unstructured meshes are utilized for spatial discretization of complex flow domain. Effectiveness of the current preconditioning algorithm, with respect to various Reynolds numbers and Mach numbers, is demonstrated by the solution of canonical problems for incompressible flows, e.g. driven cavity flows.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.2
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• pp.336-347
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• 1992

The three dimensional inviscid transonic cascade flow was investigated numerically, incorporation a four stage Runge-Kutta integration method proposed by Jameson. Time marching to the steady state was accelerated by using optimum time step and enthalpy damping. In describing the boundary conditions at inlet and outlet, Riemann invariants are considered. By adding a second and a fourth order artificial viscocities, the numerical instability due to the propagation of undamped disturbance or the rapid change of state near the shock has been prevented. The numerical results for are bump cascade, cambered two dimensional turbine cascade and three dimensional stator cascade agreed reasonably well with previous results. It has been known that the accuracy of the solution depended a lot on the modeling of the leading or trailing edge.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.12
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• pp.3991-4002
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• 1996

Thermally fully developed and thermally developing laminar flows of a Bingham plastic in a circular pipe have been studied analytically. For thermally fully developed flow, the Nusselt numbers and temperature profiles are presented in terms of the yield stress and Peclet number, proposing a correlation formula between the Nusselt number and the Peclet number. The solution to the Graetz problem has been obtained by using the method of separation of variables, where the resulting eigenvalue problem is solved approximately by using the method of weighted residuals. The effects of the yield stress, Peclet and Brinkman numbers on the Nusselt number are discussed.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.777-782
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• 2000

The flow fields in the volute casing of a small-size turbo-compressor at different flowrate (design point ${\pm}20%$) are studied by numerical analysis. The governing equations for three-dimensional steady viscous flow are solved using SIMPLE algorithm with commercial code of STAR-CD. Numerical results show that the three-dimensional flow pattern inside the volute casing of a small-size turbo-compressor is strongly influenced by secondary flows that are typically created by the curvature or the casing passages. The flow pattern in the casing also affects the performance of the turbo-compressor. In order to elucidate the loss mechanism through the volute, we prepared the secondary flow, velocity magnitude, and static pressure distribution at the four cross-sectional planes of the casing.