• Proceedings of the KSME Conference
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• 2002.08a
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• pp.181-184
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• 2002

CFD calculations are carried out to investigate the turbulent flow characteristics inside the duct of marine waterjet propulsors. The Reynolds-averaged Wavier-Stokes equations are solved using a finite-volume method. Standard $k-{\varepsilon}$ model and realizable $k-{\varepsilon}$ model are evaluated with an existing experimental data. Multi-block grid topology is adopted to describe the details of complex duct geometry. The present numerical methods are applied to the preliminary duct design of new waterjet propulsor system. Four different influx conditions are simulated to find out pressure and velocity distribution inside the intake duct. Attention is also paid upon the possible flow separation inside the waterjet duct. It is found that CFD tools can be used for the initial evaluation of inflow condition into the impeller of waterjet propulsor system.

• Journal of the Korean Society of Safety
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• v.17 no.4
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• pp.61-65
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• 2002

Nonpremixed counterflow flames at low strain rates, $ag=12s^{-1}$ and $12s^{-1}$, were numerically simulated to investigate the effects of the duct thickness on the flame structure in normal gravity. For small values of the duct thickness, the positions of the flame and stagnation point were highly sensitive to the duct thickness. When the duct thickness was greater than 6mm, however, the effects of the duct thickness on the flame structure were negligible. The computed temperature along the duct centerline agreed well with measurements.

• International Journal of Aeronautical and Space Sciences
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• v.1 no.1
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• pp.36-47
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• 2000

Three-dimensional compressible turbulent flow fields within the passage of a diffusing S-duct have been simulated by solving the Navier-Stokes equations with SIMPLE scheme. The average inlet Mach number is 0.6 and the Reynolds number based on the inlet diameter is $1.76{\times}10^6$ The extended $k-{\varepsilon}$ turbulence model is applied to modeling the Reynolds stresses. Computed results of the flow in a circular diffusing S-duct provide an understanding of the flow structure within a typical engine inlet system. These are compared with experimental wall static-pressure, total-pressure fields, and secondary velocity profiles. Additionally, boundary layer thickness, skin friction values, and streamlines in the symmetric plane are presented. The computed results depict the interaction between the low energy flow by the flow separation and the high energy flow by the reversed duct curvature. The computed results obtained using the extended $k-{\varepsilon}$ turbulence model.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.157-159
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• 2008

An numerical investigation of the flow characteristics inside a diffusing S-duct inlet with and without vortex generators(VGs) was conducted. The primary discussion herein focuses on development of secondary flow in the S-duct with and without VGs, pressure recovery and distortion at the exit are also discussed. Full three-dimensional Navier-Stokes equations are solved using finite volume method and $k-\varepsilon$ turbulence model is employed. In order to validate the credibility of the numerical methods, predicted results of surface pressure are compared with flight test for the S-duct inlet without VGs, and it shows fairly good agreement. The result shows that VGs alter the flow characteristics in the S-duct and are effective in reducing distortion and ineffective in improving pressure recovery.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.375-380
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• 2006

Embedded Duct Ventilation System in Ondol is embedded supply duct in Ondol. This system allows heat up outside air to inside temperature with out using heat exchanger and electric heating coiling in winter season. In this research, we measured temperature of inside and surface of Ondol, supply duct, and supply air temperature incorporate embedded duct ventilation system in Ondol in model house($110m^2$) & one room($23m^2$)

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.4
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• pp.530-541
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• 1998

Heat transfer augmentation in a rib-roughened duct is affected by the rib configurations, such as rib height, angle of attack, shape, rib to rib pitch, and aspect ratio of a duct. These have been the main subjects in studying the average heat transfer and the friction loss of the fully developed flow. Investigating distributions of local heat transfer coefficients and flow patterns in a duct with the rib turbulators is necessary to find the characteristics of heat transfer augmentation and to decide the optimal configurations of ribs. In the present study the numerical analyses and the mass transfer experiments are performed to understand the flow through a rib roughened duct and the heat transfer characteristics with various angles of attack of ribs. A pair of counter-rotating secondary flow in a duct has a main effect on the lateral distributions of local mass transfer coefficients. Downwash of the rotating secondary flow, reattachment of main flow between ribs and the vortices near ribs and wall enhanced the mass transfer locally up to 8 times of that in case of the duct without ribs.

• Journal of Trauma and Injury
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• v.30 no.4
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• pp.231-234
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• 2017

Extrahepatic bile duct injury is commonly associated with hepatic, duodenal, or pancreatic injuries, and isolated extrahepatic bile duct injury is rare. We report a patient who presented with an isolated extrahepatic bile duct injury after blunt trauma. A 50-year-old man was referred to our hospital after having suffered a fall down injury. His laboratory findings showed hyperbiliribinemia with elevated aspartate aminotransferase and alanine aminotransferase level. Initial abdominal computed tomography (CT) showed a mild degree of hemoperitoneum without evidence of abdominal solid organ injury. On the 3rd day of hospitalization, the patient complained of dyspnea and severe abdominal discomfort. Follow-up abdominal CT showed no significant interval change. Owing to the patient's condition, Emergency laparotomy revealed a large amount of bile-containing fluid collection and about 1 cm in size laceration on the left lateral side of the common hepatic duct. Primary repair of the injured bile duct with T-tube insertion was performed On postoperative day (POD) 30, endoscopic retrograde cholangiopancreatography showed minimal bile leakage and endoscopic sphincteroplasty and endoscopic retrograde biliary drainage were performed. On POD 61, the T-tube was removed and the patient was discharged.

• Advances in pediatric surgery
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• v.2 no.2
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• pp.143-147
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• 1996

Spontaneous perforation of the bile duct in children is a very rare disorder. We experienced a 6 year-old girl with spontaneous perforation of the right hepatic duct. The patient was initially misdiagnosed as hepatitis because of elevation of liver enzyme and then as appendicitis because of fluid collection in the pelvic cavity demonstrated by ultrasonogram. A laparoscopic exploration was done and no abnormal findings were detected except bile-stained ascites. Peritoneal drainage was performed and the patients seemed to improve clinically. Abdominal pain, distention and high fever developed after removal of the drains. DISIDA scan showed a possible of bile leak into the peritoneal cavity. ERCP demonstrated free spill of dye from the right hepatic duct. At laparotomy, the leak was seen in the anterior wall of the right hepatic duct 2cm above the junction of the cystic duct and common hepatic duct. The perforation was linear in shape and 0.8cm in size. The patient underwent cholecystectomy, primary closure of the perforation and T-tube choedochostomy. We could not identify the cause of the perforation; however, the T-tube cholangiography taken on the 42nd postoperative day showed a little more dilatation of the proximal common bile duct compared with the cholangiography taken on the 14th day. Long-term follow-up of the patient will be necessary because of the possibility for further change of the duct.

• Journal of the Korean Society of Visualization
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• v.14 no.2
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• pp.12-17
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• 2016

In this work, we investigate the flow velocity controllability of a diffuser-type multiple hydrofoil duct by experimental and numerical flow visualization approaches. The flow velocity controllability is analyzed by changing the angle of the hydrofoil near the outlet, which is the diffuser, while the incoming flow velocity is 0.6 m/s in the experiment. When the diffuser angle is changed from 0 to 7.5 degree, the maximum velocity inside the duct is varied from 1.35 m/s to 1.52 m/s. Also, it is shown from the numerical analysis that the maximum velocity is varied from 1.09 m/s to 1.17 m/s in the same condition. Thus, the aspect of the acceleration in the duct due to the increase of the diffuser angle is similar between the both approaches. Therefore, the multiple hydrofoil duct can be used to control the flow speed inside the duct for continuously extracting power close to a rated capacity.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.2
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• pp.109-117
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• 2015

Aircraft needs an inlet duct to supply the airflow to engine face. A fighter aircraft that requires low radar observability has to hide the engine face in the fuselage to reduce the Radar Cross Section(RCS). Therefore, the flow path of the inlet duct is changed into S-shape. The performance of the aircraft engine is known to be influenced by the shape and the centerline curvature of the S-Duct. In this study, CFD analysis of the RAE M 2129 S-Duct has been performed to investigate the influence of aspect ratio of inlet geometry. The performance of the S-Duct is evaluated in terms of the distortion coefficient. To simulate the flow under adverse pressure gradient better, $k-{\omega}SST$ turbulence model is employed. The computational results are validated with the ARA experimental data. The secondary flow and the flow separation are observed for all computational cases, while the semi-circular geometry has been found to produce the best results.