• Transactions of Materials Processing
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• v.14 no.9 s.81
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• pp.764-771
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• 2005

This study is related with the development of CNC spinning machine and the axisymmetric conventional spinning such as drum type and conical type steel shells. The CNC spinning machine is constructed with heavy duty frame and the hydraulic servo system is applied in order to give the exactness of motion control. The experiment has been carried out considering feeding velocity, mandrel shape, and the corner radius of mandrel and forming rollers. As a result of experiment, the limiting spinning ratio and thickness strain distribution are obtained and it can be seen that the spinnability is dominant to the feeding velocity and corner radius of forming roller. This research can contribute to the development of axisymmetric mechanical part which is applicable to automotive and aerospace industry.

• Journal of Ocean Engineering and Technology
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• v.22 no.4
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• pp.1-7
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• 2008

The primary aim of the paper is to solve an unstable axisymmetric initial value problem of wave propagation when given initial data that is deteriorated by noise such as measurement error. To overcome the instability of the problem, Tikhonov's regularization, known as a non-iterative numerical regularization method, is introduced to solve the problem. The L-curvecriterion is introduced to find the optimal regularization parameter for the solution. It is confirmed that fairly stable solutions are realized and that they are accurate when compared to the exact solution.

• 한국전산유체공학회:학술대회논문집
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• 1998.11a
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• pp.71-77
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• 1998

In this study we calculated the flowfields around the axisymmetric bodies in the rarefied gas regime by using the DSMC. A flat-ended cylinder was selected as a representative axisymmetric body and the gas used for all calculations was nitrogen. With zero angle of attack, an increasingly rapid rise in density and the effect of shock waves near the flat-ended face were examined. And on the cylinder surface velocity slips and boundary layers could be observed in the results. Larsen-Borgnakke model was used for the energy redistribution in inelastic collisions. And by considering all internal energy modes, the distributions of translational, rotational and vibrational temperatures were plotted. The calculations were peformed for various Knudsen numbers, Especially the rotational temperatures calculated for a case were compared with the experimental results. And the simulation results show good agreements with the experimental ones.

• Journal of computational fluids engineering
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• v.2 no.2
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• pp.35-43
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• 1997

An efficient inverse method for 1.he supersonic/hypersonic axisymmetric body design is developed for the parabolized Navier-Stokes equations. The developed method is examined numerically for three extreme testcases in the supersonic(M/sub ∞/=3.0) and hypersonic(M/sub ∞/=6.28) speeds. The first one is a negative pressure distribution near a vacuum pressure and the second one is a positive pressure distribution over the whole region of the body. The last one is the case of abrupt change of pressure distribution to zero in the forward region of the body. These testcases show the robustness of the method. By introducing a regular-falsi method and by using a not-fully converged inverse solution, the convergence behavior was greatly improved.

• 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.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.452-457
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• 1993

For the calculation of transonic laminar relative flow fields on the axisymmetric H-S and B-B stream surfaces in turbomachinery, a finite volume method developed in Part (I) is extended. Energy equation is replaced for simplicity by the condition of constant rothalpy throughout the flow fields. For axisymmetric H-S flow the circumferential componets of absolute velocity are given in advance so that this component of momentum equations can be neglected. Some numerical results show good agreement with experimental data.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1410-1413
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• 2003

Drawing is a basic plastic deformation method and productive manufacturing process make wire. rod and variety section geometry bar. Study for the rod drawing process of rod was researched long littles. but non-axisymmetric drawing process is weak. So metal flow is very irregular in non-axisymmetric drawing process and difficult to define about material deformation generally. In this paper, to solve material deformation, use finite element method and then define suitable shape for rod to hexagonal drawing dies. And research corner filling rate and surface roughness for the high strength steel hexagonal bar produced defined dies.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.831-834
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• 2002

An analytic approach is attempted to predict the amplification of turbulence in compressible flows experiencing one-dimensional and axisymmetric bulk dilatation. The variations of vortex radius and vorticity are calculated, and then the amplification of turbulence is obtained from them by tracking three representative vortices. For a one-dimensionally compressed flow, the present analysis slightly underestimates the amplification of velocity fluctuations and turbulent kinetic energy, relative to that of rapid distortion theory in the solenoidal limit. For an axisymmetrically distorted flow, the amplification of velocity fluctuations and turbulent kinetic energy depend not only on the density ratio but also on the ratio of streamwise mean velocities, which represents streamwise vortex contraction/stretching. In all flows considered, the amplification of turbulence is dictated by the mean density ratio. In the axisymmetric flow, streamwise vortex stretching/contraction, however, alters the amplification slightly.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.5
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• pp.620-627
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• 2003

Radiative heat transfer in an axisymmetric enclosure with absorbing, emitting, and scattering medium is studied here by using the different methods such as MDOM, FVM, and FVM2 with emphasis on the treatment of angular derivative term, which appears in a curvilinear coordinates due to angular redistribution. After final discretization equation for FVM2 is introduced by using the step scheme and directional weights, present approach is validated by applying it to three different benchmarking problems with absorbing, emitting, and scattering medium.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.1009-1014
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• 2001

A numerical investigation on nonlinear oscillations of gas in an axisymmetric resonant tube is presented. When a tube is oscillated at a resonant frequency, acoustic variables such as density, velocity, and pressure undergo very large perturbation, often described as nonlinear oscillation. In order to analyze these phenomena, axisymmetric 2-D nonlinear governing equations have been derived and solved numerically. Numerical simulations were accomplished for cylindrical, conical, and 1/2 cosine-shape tubes, which have same volume and length. For conical and 1/2 cosine-shape tubes, very large variation of pressures can be induced without shock formation except the cylindrical tube. In addition, the results well agree to those of 1-D simple model analysis.