• Journal of computational fluids engineering
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• v.10 no.3 s.30
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• pp.70-76
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• 2005

A two-layer incompressible time-accurate Euler solver is applied to analyze flow fields around a submerged body moving at a critical speed near a pycnocline. Discontinuities in the dependent variables across the material interface are captured without any dissipation or oscillation using the ghost fluid method on an unstructured grid. It is shown that the material interlace has significant effects on forces acting on a submerged body moving near a pycnocline regardless of the small difference in densities of two layers. Contrary to the shallow water waves, a submerged body can reach a critical speed at very low Froude number due to the small difference in the densities of the two layers.

• Journal of computational fluids engineering
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• v.12 no.4
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• pp.20-27
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• 2007

Two-dimensional stagnation flow toward a plane wall coated with magnetic fluid of uniform thickness is investigated. The flow field is represented as a similarity solution of the Navier-Stokes equation for this incompressible laminar flow. The resulting third order ordinary differential equation is solved numerically by using the shooting method and by determining two shooting parameters so as to satisfy the boundary and interface conditions. Features of the flow including streamline patterns are investigated for the varying values of density ratio, viscosity ratio, and Reynolds number. An adverse flow with double eddy pair in magnetic fluid region is found to emerge as the Reynolds number becomes higher than a threshold value. The results for the interface velocity, interface and wall shear stress, and boundary layer and displacement thickness are also presented.

• Communications of the Korean Mathematical Society
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• v.12 no.2
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• pp.479-490
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• 1997

We consider long nonlinear waves in the two-layer flow of an inviscid and incompressible fluid bounded above by a free surface and below by a rigid boundary. The flow is forced by a bump on the bottom. The derivation of the forced KdV equation fails when the density ratio h and the depth ratio $\rho$ yields a condition $1 + h\rho = (2-h)((1-h)^2 + 4\rho h)^{1/2}$. To overcome this difficulty we derive a forced modified KdV equation by a refined asymptotic method. Numerical solutions are given and hydraulic fall solution of a two layer fluid is expressed analytically in the case that derivation of the forced KdV (FKdV) equation fails.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.5
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• pp.755-761
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• 1987

Two-Dimensional incompressible laminar boundary layer with the reversed flow region is computed using the parially parabolized Navier-Stokes equations in primitive variables. The velocities and the pressure are explicity coupled in the difference equation and the resulting penta-diagonal matrix equations are solved by a streamwise marching technique. The test calculations for the trailing edge region of a finite flat plate and Howarth's linearly retarding flows demonstrate that the method is accurate, efficient and capable of predicting the reversed flow region.

• Journal of computational fluids engineering
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• v.2 no.1
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• pp.129-137
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• 1997

We consider long nonlinear waves in the two-layer flow of an inviscid and incompressible fluid bounded above by a free surface and below by a rigid boundary. The flow is forced by a bump on the bottom. The derivation of the forced KdV equation fails when the density ratio h and the depth ratio ρ yields a condition 1＋hρ=(2-h)((1-h)²＋4ρh)/sup 1/2/. To overcome this difficulty we derive a forced modified KdV equation by a refined asymptotic method. Numerical solutions are given and hydraulic fall solution of a two layer fluid is expressed analytically in the case that derivation of the forced KdV(FKdV) equaition fails.

• 한국전산유체공학회:학술대회논문집
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• 2007.10a
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• pp.39-44
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• 2007

A similarity solution of the Navier-Stokes equation for the axisymmetric stagnation flow near a plane wall coated with a magnetic fluid of uniform thickness is constructed. The shape functions representing the flow in two (magnetic and normal) fluid layer are determined from a third order boundary value problem, which is solved by the Runge-Kutta method with two shooting parameters. Features of the flow including streamline pattern and interface velocity are investigated for the varying values of density ratio, viscosity ratio, and Reynolds number. The results for the interface and wall shear stress, boundary layer and displacement thickness are also presented.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.9
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• pp.799-807
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• 2005

The flow characteristics and the heat transfer rate on a surface by the interaction of a pair of vortices are studied numerically. To analyze the common flow up produced by vortex generators in a rectangular channel flow, the pseudo-compressibility viscous method is introduced into the Reynolds-averaged Navier-Stokes equation for 3-dimensional unsteady, incompressible viscous flows. To predict turbulence characteristics, a two-layer $k-\varepsilon$ turbulence model is used on the flat plate 3-dimensional turbulence boundary The computational results predict accurately Reynolds stress, turbulent kinetic energy and flow field generated by the vortex generators. The numerical results, such as thermal boundary layers, skin friction characteristics and heat transfers, are also reasonably close to the experimental data.

• Journal of Mechanical Science and Technology
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• v.20 no.1
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• pp.147-157
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• 2006

This paper represents a numerical study of the flow field due to the interactions between a pair of vortices produced by vortex generators in a rectangular channel flow. In order to analyze longitudinal vortices induced by the vortex generators, the pseudo-compressibility method is introduced into the Reynolds-averaged Navier-Strokes equations of a 3-dimensional unsteady, incompressible viscous flow. A two-layer $k-{\epsilon}$ turbulence model is applied to a flat plate 3-dimensional turbulence boundary to predict the flow structure and turbulence characteristics of the vortices. The computational results predict accurately the vortex characteristics related to the flow field, the Reynolds shear stresses and turbulent kinetic energy. Also, in the prediction of skin friction characteristics the computational results are reasonably close to those of the experiment obtained from other researchers.

• Journal of Mechanical Science and Technology
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• v.14 no.4
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• pp.441-447
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• 2000

Direct numerical simulation has been used to study turbulent boundary layers with convex curvature. A direct numerical simulation program has been developed to solve incompressible Navier-Stokes equations in generalized coordinates with the finite volume method. We considered two boundary layer thicknesses. When the curvature effect is small, mean velocity statistics show little difference with those of a plane channel flow. Turbulent intensity decreases as curvature increases. Contours suggest that streamwise vorticities are strong where large pressure fluctuations exist.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.1
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• pp.31-40
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• 2000

This paper describes the numerical computations of the interaction between the streamwise vortex and a flat plate 3-D turbulent boundary layer. In the present study, the main interest is in the behavior of the streamwise vortices introduced in turbulent boundary layers. The flow behind a vortex generator is modeled by the information that is avilable from studies on the dalta winglet. An algorithm of the solution of the incompressible Navier-Stokes equations for three-dimensional turbulent flows, together with a two layer turbulent model to resolve the near-wall flow, is based on the method of artificial compressibility. The present results show boundary layer distortion due to vortices, such as strong spanwise flow divergence and boundary thinning, and have a good agreement with the experimental data.