• Journal of the Korean Society of Mechanical Technology
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• v.20 no.6
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• pp.924-928
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• 2018

The objective of this study is to solve a problem that is occurred during the spline machining of tubular shaft yoke in both side IMS module. In order to simulate the problem, the movement direction of upper die was set as standard case and error case. The material of tubular shaft yoke was set to S20C as refer to the analysis library. The movement directions of upper die were separated with standard case and error case. The error case was set to simulate the problem in the spline machining of tubular shaft yoke. In order to solve the problem, the outer radius of upper die were modelled from 9.40mm to 9.44mm. The simulation results were analyzed and compared in terms of effective stress, metal flow line and folding phenomena characteristics. In case of the outer radius of upper die was 9.42mm, it was observed a relatively uniform effective stress distribution and had a straight metal flow line.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.2
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• pp.101-106
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• 2011

In this study, the velocity distribution according to upper side coner shape of underwater construction with rectangular cylinder was measured with PIV method and the wake flow characteristics was considered. According to the coner shape, the flow pattern of wake flow was also differed greatly and the step-shaped coner of cut-off ratio B/H=0.06 was similar in the slope shape in result.

• 한국전산유체공학회:학술대회논문집
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• 2006.10a
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• pp.142-146
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• 2006

The behavior of a hemisphere-cylinder flight vehicle at high angles of attack and side slip angles have been studied. $0^{\circ}{\sim}35^{\circ}$ angles of attack and $0^{\circ}{\sim}5^{\circ}$ side slip angles were selected as fright conditions at Mach No. 0.3. Flow changes from low angles of attack to high angles of attack were compared and analyzed. We changed from low to high angles of attack with small side slip angles. We compared normal, side and axial force coefficients among various test cases.

• Journal of Biomedical Engineering Research
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• v.13 no.4
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• pp.339-352
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• 1992

A numerical simulation of the steady and pulsatile flow across the end-to-side anastomosis was performed In order to understand the role of flow dynamics in the preferential bevel opment of distal anastomotic intimal hyperplasla. The finite element technique was employed to solve two-dimensional unsteady pulsatile flow in that region. The results of the steady flow revealed that low shear stresses occur at the proximally occluded host artery and at the recirculation region in the Inner wall just distal to the toe region of the anastomosis. The nor- mal;zed wall shear rate was increased, as was the recirculation zone size in the host artery of the by-pass graft anastomosis, with increased anastomotic junction angle. In order to min imize the size of the low wall shear region which might result in the intimal hyperplasia in the by-pass graft anastomosis, a smaller anastomotic junction angle is recommended. The pulsatile flow simulation revealed flow that regions of low and ascillating mali shear do exist near the anastomosis as In the steady simulation. The shift of stagnation point depends on the pulsation of the flow. As the flow was accelerated at systole, the stagnation point moved downstream, disappered at early diastole and reappeared during late diastole. Low shear stress was also found along both walls of the occluded proximal artery. However, the diastolic flow behavior is quite different from the steady results. The vortex near the occluded artery moved downstream and inwardly during late systole, and disappeared during diastole. Recirculations proximal to the toe and heel regions were significant during diastole. Shear stress oscillation was found along the opposite wall. The results of the present study revealed that tow shear occurs at the proximally occluded host artery aud the recirculation region in the inner wall Just dlstal to the toe region of the anastomosis. The present study suggested that the regions of fluctuated wall shear stress wit flow separation is correlated with the preferential developing regions of anastomosis neointial fibrous hyperplasia.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.1
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• pp.26-33
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• 2001

Thrust vector control system is control device which is mounted exit of the nozzle to generate pitch, yaw and roll directional force by deflecting flow direction of the supersonic jet from the nozzle. By obtaining control force, jetvane which is exposed in jet flow is working thermal and aerodynamic load. Axial thrust loss and side thrust is affected by shock patterns and interactions between jetvanes according to jetvane geometry and turning angle. In this study, we designed 6 types of jetvane to evaluate pitch, yaw and roll characteristics of ietvane in supersonic flow, and perform the cold flow test in range of turning angles of jetvanes between $0^{\cire}$ and $25^{\cire}$ by $5^{\cire}$ respectively. Also, calculation is going side by side to analyse flow interaction. Results show that there is no interactions between jetvanes upto turning angle 20$^{\circ}$, chord and lead length ratio is very important parameter to aerodynamic performance and maximum thrust loss is appeard to 17% of axial thrust in roll directional control.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.3
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• pp.106-114
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• 2003

The pressure ripple in the delivery port is caused by flow ripple, which is induced by variation of pumping chamber volume. The other reason is the reverse flow from the outlet volume produced by pressure difference between pumping chamber and outlet volume, when the pumping chamber is connected with the outlet volume. In this study, a mathematical model is presented for analyzing discharge pressure ripple, which includes vane detachment, cam ring movement , and fluid inertia effects in V-groove in the side plate. From the analysis and experiment, it was found that V-groove on the side plate, coefficient of spring supporting the cam ring, and average discharge pressure are the main factors of discharge pressure ripple in variable displacement vane pump. The theoretical results, provided in this study, were well agreed with experimental results. The analytical model to estimate the magnitude of pressure ripple in this study is expected to be used f3r the optimal design of the variable displacement vane pump.

• 한국전산유체공학회:학술대회논문집
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• 2007.10a
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• pp.171-176
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• 2007

Supersonic viscous flow over a 5 degree half angle cone studied computationally with three-dimensional Navier-Stokes equations. Steady asymmetric solutions of 5-deg half angle cone show that the asymmetric flow separation is caused by convective instability. The angle of attack, Reynolds number, and Mach number affected the side force variation that is caused by asymmetric vortical flow.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.6 s.261
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• pp.566-573
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• 2007

Flows around two oscillating cylinders in side-by-side arrangement at Re=185 are simulated using an immersed boundary method. The cylinders oscillate vertically in opposite directions in uniform cross-flow. We describe flow patterns, drag and lift forces by varying distance between two cylinders $(1.4{\leq}g{\leq}2.2,\;1.0{\leq}g{\leq}1.8)$ and oscillating frequency ratios $(f_e/f_o=0.8,\;f_e/f_o=1.0\;and\;f_e/f_o =1.2)$. Wake patterns, drag and lift coefficients are affected by both of frequency ratio and gap between two cylinders. Near wakes of each case are classified with the definition of previous studies.

• 한국전산유체공학회:학술대회논문집
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• 1999.11a
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• pp.17-22
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• 1999

Convergence characteristics and efficiency of three implicit approximate factorization schemes(ADI, DDADI and MAF) are examined using 2-Dimensional compressible upwind Navier-Stokes code. Second-order CSCM(Conservative Supra Characteristic Method) upwind flux difference splitting method with Fromm scheme is used for the right-hand side residual evaluation, while generally first-order upwind differencing is used for the implicit operator on the left-hand side. Convergence studies are performed using an example of the flow past a NACA0012 airfoil at steady transonic flow condition, i. e. Mach number 0.8 at $1.25^{\circ}$ angle of attack. The results were compared with other computational results in order to validate the current numerical analysis. The results from the implicit AF algorithms were compared well in low surface with the other computational results; however, not well in upper surface. It might be due to lack of the grid around the shock position. Because the algorithm minimizes the errors of the approximate decomposition, the improved convergence rate with MAF were observed.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.33-38
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• 2008

Numerical investigation of asymmetric vortices at high angles of attack subsonic flow is performed using three-dimensional Navier-Stokes equations. A small bump has been carefully selected and attached near the nose of an ogive cylinder to simulate symmetric vortices. Selected bump shape does develop asymmetric vortices and is verified using Lamont's experimental results. By changing the angle of attack, Reynolds numbers, and Mach numbers, the characteristics of asymmetric vortices are observed. The angle of attack which contributes significantly to the generation of asymmetric vortices are over 30 degrees. By increasing Mach number and Reynolds number asymmetric vortices, hence the side forces show decreasing trend..