• Journal of computational fluids engineering
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• v.3 no.1
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• pp.11-21
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• 1998

A vorticity-based method for the numerical solution of the two-dimensional incompressible Navier-Stokes equations is presented. The governing equations for vorticity, velocity and pressure variables are expressed in an integro-differential form. The global coupling between the vorticity and the pressure boundary conditions is fully considered in an iterative procedure when numerical schemes are employed. The finite volume method of the second order TVD scheme is implemented to integrate the vorticity transport equation with the dynamic vorticity boundary condition. The velocity field is obtained by using the Biot-Savart integral. The Green's scalar identity is used to solve the total pressure in an integral approach similar to the surface panel methods which have been well established for potential flow analysis. The present formulation is validated by comparison with data from the literature for the two-dimensional cavity flow driven by shear in a square cavity. We take two types of the cavity now: (ⅰ) driven by non-uniform shear on top lid and body forces for which the exact solution exists, and (ⅱ) driven only by uniform shear (of the classical type).

• 한국전산유체공학회:학술대회논문집
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• 1995.10a
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• pp.55-63
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• 1995

The flow field around a high-speed train including cross-wind effects has been simulated. This study solves 3-D unsteady incompressible Navier-Stokes equations in the inertial frame using the iterative time marching scheme. The governing equations are differenced with 1st-order accurate backward difference scheme for the time derivatives, 3th-order accurate QUICK scheme for the convective terms and 2nd-order accurate central difference scheme for the viscous terms. The Marker-and-Cell concept was applied to efficiently solve continuity equation, which is differenced with 2nd-order accurate central difference scheme. The 4th-order artificial damping is added to the continuity equation for numerical stability. A C-H type of elliptic grid system is generated around a high-speed train including ground. The Baldwin-Lomax turbulent model was implemented to simulate the turbulent flows. To validate the present procedure, the flow around a high speed train at constant yaw angle of $45^{\circ}\;and\;90^{\circ}$ has been simulated. The simulation shows 3-D vortex generation in the lee corner. The flow separation is also observed around the rear of the train. It has concluded that the results of present study properly agree with physical flow phenomena.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3209-3214
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• 2007

This study numerically investigates the unsteady flow and acoustic characteristics of a flapping wing using a hydrodynamic/acoustic splitting method. The Reynolds number based on the maximum translation velocity of the wing is Re=8800 and Mach number is M=0.0485. The flow around the flapping wing is predicted by solving the two-dimensional incompressible Navier-Stokes equations (INS) and the acoustic field is calculated by the linearized perturbed compressible equations (LPCE), both solved in moving coordinates. Numerical results show that the hovering sound is largely generated by wing translation (transverse and tangential), which have different dipole sources with different mechanisms. As a distinctive feature of the flapping sound, it is also shown that the dominant frequency varies around the wing.

• Journal of computational fluids engineering
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• v.15 no.2
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• pp.35-40
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• 2010

In the present work, LES with new variational multiscale method is conducted on the fully developed channel flow with Reynolds number, 180 based on the friction velocity and the channel half width. Incompressible Navier-Stokes equations are integrated using finite element method with the basis function of NURBS. To solve space-time equations, Newton's method with two stage predictor multicorrector algorithm is employed. The code is parallelized using MPI. The computational domain is a rectangular box of size $2{\pi}{\times}2{\times}4/3{\pi}$ in the streamwise, wall normal and spanwise direction. Mean velocity profiles and velocity fluctuations are compared with the data of DNS. The results agree well with those of DNS and other traditional LES.

• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.56-59
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• 2009

In the present work, LES with new variational multiscale method is conducted on the fully developed channel flow with Reynolds number is 180 based on the friction velocity and the channel half width. Incompressible Navier-Stokes equations are integrated using finite element method with the basis function of NURBS. To solve space-time equations, Newton's method with two stage predictor multicorretor algorithm is employed. The code is parallelized using MPI. The computational domain is a rectangular box of size $2{\pi}{\times}2{\times}4/3{\pi}$ in the streamwise, wall normal and spanwise direction. Mean velocity profiles and velocity fluctuations are compared with the data of DNS. The results agree well with those of DNS and other traditional LES.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.165-169
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• 2009

The effect of the Dirichlet boundary condition for the redistance equation of level set method on the solutionof sloshing problem is investigated by adopting four Dirichlet boundary conditions. For the solution of the incompressible Navier-Stokes equations, P1P1 four-step fractional finite element method is employed and a least-square finite element method is used for the solutions of the two hyperbolic type equations of level set method; advection and redistance equation. ALE (Arbitrary Lagrangian Eulerian) method is used to deal with a moving computational domain. It has been shown that the free surface motion in a sloshing tank is strongly dependent on the type of the Dirichlet boundary condition and the results of broken dam and sloshing problems using various Dirichlet boundary conditions are discussed and compared with the existing experimental results.

• The KSFM Journal of Fluid Machinery
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• v.6 no.1 s.18
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• pp.44-50
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• 2003

Flow through a turbine flow meter is simulated by solving the incompressible Navier-Stokes equations. The solution method is based on the pseudo-compressibility approach and uses an implicit-upwind differencing scheme together with the Gauss-Seidel line relaxation method. The equations are solved steadily in rotating reference frames, and the centrifugal force and the Coriolis force are added to the equation of motion. The standard $k-{\epsilon}$model is employed to evaluate turbulent viscosity. Computational results yield quantitative as well as qualitative information on the design of turbine flow meters by showing the distributions of pressure and velocity around the turbine blades.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.195-199
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• 2005

Wave breaking phenomenon near the fore body of a ship is numerically simulated. The ship advance with uniform velocity in calm water. For the simulation, incompressible Navier-Stokes equations and continuity equation are adopted as governing equations. The simulation is carried out in staggered variable mesh system with finite difference method. Marker and Cell(MAC) method and Marker-Density method are employed to track the free surface. Body boundary conditions are satisfied with the adoption of porosity method and no-slip condition on the hull surface. The ship model has a wedge type fore-body, and the computational domain is an appropriate region around the fore-body. The computation results are compared with some experimental results. Also the difference of the free surface tracking methods are discussed.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.251-255
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• 2008

Flow field around helicopter involves incompressible flow near the blade root and compressible flow at the blade tip. A problem occurs for low Mach number flow due to the stiffness of the governing equations. Time-derivative preconditioning techniques have been incorporated to reduce the stiffness that occurs at low speed region. The preconditioned form of the compressible Navier-Stokes and Euler equations is used. Computations are performed for the Caradonna-Tung's hovering and non-lifting forward flight case. Computational results are in good agreement with the experimental data.

• 한국전산유체공학회:학술대회논문집
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• 2008.10a
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• pp.251-255
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• 2008

Flow field around helicopter involves incompressible flow near the blade root and compressible flow at the blade tip. A problem occurs for low Mach number flow due to the stiffness of the governing equations. Time-derivative preconditioning techniques have been incorporated to reduce the stiffness that occurs at low speed region. The preconditioned form of the compressible Navier-Stokes and Euler equations is used. Computations are performed for the Caradonna-Tung's hovering and non-lifting forward flight case. Computational results are in good agreement with the experimental data.