• Proceedings of the KSME Conference
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• 2001.06d
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• pp.522-527
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• 2001

Comprehensive numerical computations are made of side-heated squire cavity which is exposed to zero mean g-jitter. Numerical solutions are acquires to the governing two-dimensional Navier-Stokes equations for a Boussinesq fluid. When the system is exposed to pure sinusoidal g-jitter inclined to the vertical axis, in spite of zero mean gravity there exist non zero net flow fields [8]. The resonance phenomenon are observed in moderate Rayleigh number. And, by comprehensive numerical work, unlike[5], it is found that they are related with the overshoot phenomenon of the sudden gravity up problem.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.402-406
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• 2000

In the Over-The-Range, the outlet size is limited by the industrial standards. Therefor to enlarge the volume of cavity, the installation height of ventilation fan is become small, the system resistance is higher than before. For that reason, the important design variables such as the diameter of a fan, the scroll expansion angle, etc. which play the significant role on flow rate and noise, are confined. In this study, we made an experiment of the diameter of fans relation to scroll expansion angle and investigated flow rate of the length of fans in enlarged cavity volume of OTR, and then we designed the new scroll to improve the flow rate and noise level. As a result, flow rate increased to 110% compared to current scroll and the blade passing frequency of a fan is disappeared by inclined cut-off shapes.

• Proceedings of the SAREK Conference
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• 2003.07a
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• pp.208-208
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• 2003

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.281-284
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• 2008

The flow of combustor in scramjet engine is supersonic speed. So residence time and mixing ratio are very important factors for efficient combustion. This study used open cavity on fuel/air mixing model and laser schlieren was carried out to investigate flow characteristics around a jet orifice and a cavity. A source of illumination has 10 ns endurance time so it can observe unsteady flow characteristics efficiently. Pressure was measured by varying momentum flux ratio. And the change of critical ignition point was observed to change of momentum flux ratio.

• Structural Engineering and Mechanics
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• v.49 no.4
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• pp.427-448
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• 2014

At present, the time of easy oil and gas is over. Now, the largest part of fossil fuels is concentrated in the deepest levels of tectonic structures and in the sea shelves. One of the most cumbersome operations of their extraction is the bore-hole drilling. In connection with austere tectonic and climate conditions, their drivage every so often is associated with great and diversified technological difficulties causing emergencies on frequent occasions. As a rule, they are linked with drill string accidents. A key role in prediction of these situations should play methods of theoretical modelling. For this reason, there is a growing need for development and implementation of new numerical methods for computer simulation of critical and post-critical behavior of drill strings (DSs). In this paper, the processes of non-linear deforming of a DS in cylindrical cavity of a deep bore-hole are considered. On the basis of the theory of curvilinear flexible rods, non-linear constitutive differential equations are deduced. The effects of the longitudinal non-uniform preloading, action of torque and interaction between the DS and the bore-hole surface are taken into account. Owing to the use of curvilinear coordinates in the constraining cylindrical surface and a specially chosen concomitant reference frame, it became possible to separate the desired variables and to reduce the total order of the equation system. To solve it, the method of continuation the solution by parameter and the transfer matrix technique are applied. As a result of the completed numerical analysis, the critical states of the DS loading in the cylindrical channels of inclined bore-holes are found. It is shown that the modes of the post-critical deforming of the DS are associated with its irregular spiral curving prevailing in the zone of bottom-hole-assembly. The possibility of invariant state generation during post-critical deforming is established, condition of its bifurcation is formulated. It is shown that infinite variety of loads can correspond to one geometrical configuration of the DS. They differ each from other by contact force functions.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.1
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• pp.24-31
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• 1998

Unsteady propeller blade forces arising from shaft inclination have been found to be an important contribution tn total blade forces. The position of the wake relative to a blade oscillates with the first blade frequency, thus giving rise to unsteady blade forces which is significant relative to the forces produced directly by flow inclination. In order to find a wake geometry due to shaft inclination, a non-axisymmetric wake model is developed and applied to a specific case, which has experimental values. Predicted cavity shapes and unsteady forces acting on the blades of an inclined shaft propeller are compared to those predicted by other numerical methods, as well as those measured in experiments.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.2
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• pp.132-140
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• 2010

The very erosive cavitation is simulated by an inclined propeller dynamometer in the medium-size cavitation tunnel of MOERI. The inclined shaft for propeller makes strong cavitaion, which occurs around the root of a propeller blade. The cavitation begins at the leading edge of the propeller and contracted toward the trailing edge through the reentrant jet action. The cavity focused on the region near the trailing edge collapsed over the blade surface. As the impact pressure by the cavitation collapsing is too strong, it can damage the blade surface in the form of pit. This cavitation impacts created by the collapsing process are similar to the full-scale ones and are different from those by other erosion test methods. The newly developed cavitation erosion test method can be applied to evaluate the materials such as metals, ceramics and coatings in terms of cavitation resistance.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.15 no.4
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• pp.388-395
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• 1986

Numerical solutions of two-dimensional, steady, and natural are investigated in a confined rectangular cavity with porous media. The saturated fluid is bounded by two isothermal vertical walls at different temperatures and two adiabatic horizontal walls. Governing equations are numerically solved by finite difference method with the up wind scheme. Distributions of streamline and temperature we. predicted for aspect ratios ranging from 0.1 to 1.0, Rayleigh numbers 50 to $10^4$, and tilt angles $0^{\circ}\;to\;60^{\circ}$. Representative plots of temperature and velocity field according to tilt angle are presented. The effects of aspect ratio, Rayleigh number, and tilt angle on local and average Nusselt numbers are obtained. The optimum conditions for maximum Nusselt number are also presented with tilt angles.

• Korean Journal of Veterinary Research
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• v.41 no.3
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• pp.447-451
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• 2001

A 6-week-old female cocker spaniel, with a history of abasia astasia, was referred to the Department of Laboratory Animal Medicine, Medical Research Center, Yonsei University College of Medicine on February 23, 2000. The ribs inclined downwards with a sharp slope on both lateral sides of the thorax. The animal was diagnosed as pectus excavatum. She showed no signs of dyspnea, dyschezia, or dysuria. There was no heart murmur or sign of neural disease. For rehabilitation treatment, she was given physical exercise therapy 2 to 3 times a day by bending and stretching each articulation of the hind limbs and pressing the costochondral junction in and upward with both hands placed on each lateral side. After a month of therapy, she was able to stand up and walk. The therapy continued and resulted in the slight reformation of a round thoracic wall. The flattened rib cartilages grew more round by palpation and the thoracic cavity distended. Rehabilitation therapy yielded good results, enabling the subject to walk and run normally, as the thoracic cavity was distended by the rounded rib junction.

• Archives of Plastic Surgery
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• v.35 no.3
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• pp.235-242
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• 2008

Purpose: Due to increasing interest in the treatment of spinal cord injuries, many histopathological studies have been conducted to prove that many neurotrophic factors including growth hormone are important for regeneration of the injured spinal cord. Growth hormone has to be given everyday, however, and this negatively affects compliance in clinical trials. Recently, the invention of sustained release growth hormone (SRGH) that can be given just once a week may both help the regeneration of injured spinal cord and, at the same time, be more compliant and convenient for clinical patients. Methods: In this study, thirty 7-week-old female Spraque-Dawley rats were subjected to a weight-driven impact spinal cord injury. They were divided into 3 groups and Group I and II were injected with SRGH once a week for 4 weeks; Group I were injected into the injured spinal cord area, while Group II were injected into the peritoneal cavity. Meanwhile, Group III were injected with normal saline solution. The functional outcome was evaluated using the Basso-Beattie-Bresnahan motor rating score and the inclined plane test was done 4 weeks after the first injection. Histopathological examination was performed at the same time and the amount of residual white matter was measured in all groups. Results: After 4 weeks, Groups I and II showed greater improvement than Group III(the control group) in the functional test. In the control group, invasion of atypical phagocytes, axonal degeneration, edema and cavity formation in the posterior site of spinal cord gray matter was observed in histopatholgical examination. The rate of residual white matter in Group III was less than in the other groups. Conclusion: Data showed significant functional and histopathological improvement in the groups treated with SRGH into the spinal and peritoneal cavity compared with the control group. SRGH is therefore beneficial because it helps with regeneration of the injured spinal cord and improves the compliance and convenience of patients.