• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.4
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• pp.513-528
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• 2013

A floating Oscillating Water Column (OWC) wave energy converter, a Backward Bent Duct Buoy (BBDB), was simulated using a state-of-the-art, two-dimensional, fully-nonlinear Numerical Wave Tank (NWT) technique. The hydrodynamic performance of the floating OWC device was evaluated in the time domain. The acceleration potential method, with a full-updated kernel matrix calculation associated with a mode decomposition scheme, was implemented to obtain accurate estimates of the hydrodynamic force and displacement of a freely floating BBDB. The developed NWT was based on the potential theory and the boundary element method with constant panels on the boundaries. The mixed Eulerian-Lagrangian (MEL) approach was employed to capture the nonlinear free surfaces inside the chamber that interacted with a pneumatic pressure, induced by the time-varying airflow velocity at the air duct. A special viscous damping was applied to the chamber free surface to represent the viscous energy loss due to the BBDB's shape and motions. The viscous damping coefficient was properly selected using a comparison of the experimental data. The calculated surface elevation, inside and outside the chamber, with a tuned viscous damping correlated reasonably well with the experimental data for various incident wave conditions. The conservation of the total wave energy in the computational domain was confirmed over the entire range of wave frequencies.

• Korean Journal of Head & Neck Oncology
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• v.18 no.1
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• pp.80-83
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• 2002

Thyroglossal duct cyst is a congenital anomaly generally appearing as an asymptomatic midline neck mass. Generally, the duct cyst is benign, but 1 percent of cases may be malignant. These present the same histologic types as thyroid carcinomas. The most common pathologic type is papillary carcinoma. Regional lymph node metastasis of papillary carcinomas in thyroglossal cyst occurs in 7.7 percent of cases. Prognosis of papillary carcinoma is excellent. The treatment has been quite variable, but the most common initial treatment is Sistrunk's operation. Adequate excision of cyst and its tract including the mid-portion of the hyoid bone is the treatment of choice. We experienced two cases of papillary carcinoma arising in thyroglossal duct cyst between 1986 and 2002.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.766-771
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• 2001

An experimental study was undertaken to investigate the effect of coriolis force for the turbulent flow at low Reynolds numbers in a rotating straight square duct. The study was carried out using a hot-wire anemometer. The flow Reynolds number based on the hydraulic diameter ranged from 4,000 to 18,000 and Rotation number ranged from 0 to 0.196. At Re=9000, developing turbulent flow was calculated for mean velocity and Reynolds stress. Pressure coefficient and energy dissipation spectrum were also calculated.

• Clinical and Experimental Pediatrics
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• v.56 no.10
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• pp.451-455
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• 2013

Sialolithiasis is caused by the obstruction of a salivary gland or its excretory duct by the formation of calcareous concretions or sialoliths; this results in salivary ectasia and provokes subsequent dilation of the salivary gland. Sialolithiasis is relatively common, accounting for 30% of salivary diseases; however, it is rarely observed in childhood. This case report describes a 2-year-old male patient who complained of a painful swelling over the right cheek, and presented with palpable stones and pus discharge from the orifice of the right Stensen's duct. Computerized tomography of the neck confirmed the diagnosis, and the patient received intravenous empiric antibiotics combined with intraoral sialolithotomy. We also provide a review of the spectrum of concepts regarding the pathogenesis, diagnosis, and treatment of sialolithiasis.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.639-642
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• 2002

A tubular centrifugal fin is designed by using various methods of analysis and design. A preliminary design method based on empirical optimum curves for centrifugal fin is used to determine the geometric parameters for tubular centrifugal fan. And, Quasi-3D streamline curvature duct-flow analysis is used to provide the primary position of streamlines and spanwise distribution of flow angle f3r generation of blade geometry based on S1 surface. Three-dimensional CFD solution then is obtained to optimize the blade design. Constriction of flow path in the region of impeller, backward swept blade, and central cone, which are introduced to improve the design, successfully remove or suppress the vortices downstream of the impeller.

• Journal of KSNVE
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• v.8 no.1
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• pp.122-131
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• 1998

Internal and external acoustic fields of the engine inlet are calculated by using a finite element method. The far fields non reflecting boundary condition is enforced by using a wave envelope element, which is a kind of infinite element. The geometry is assumed an axisymetric duct. Sources of the fan are modeled by the Tyler and Sofrin's theory. Effects of uniformly moving medium are considered. A pulsating sphere and an oscillating piston problem are calculated to verify the external problems, and compared with exact solutions. When the wave envelope element is applied at the far boundary, the calculated finite element solutions show good agreements with the exact solutions. The engine inlet is solved with the combined internal and external grid. The cut-off phenomena on engine inlet duct are observed.

• Journal of ILASS-Korea
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• v.11 no.1
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• pp.30-38
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• 2006

High temperature furnaces such as power plant and incinerator contribute considerable part of NOx generation and face urgent demand of De-NOx system. Reducing agent is injected into the flue gas flow to activate do-NOx system. Almost SCR system adopt vaporized ammonia injection system. Vaporizer, dilution system and additional space are needed to gasify and inject ammonia. Liquid spray injection system can simplify and economize post-treatment system of flue gas. In this study, mixing caused by gas or liquid injection of reducing agent into flue gas duct was investigated experimentally. Carbonated water was used as tracer and simulated agent and mixing of liquid spray in a duct flow was studied. To achieve that, the angle of attack of static mixer is simulated and $CO_2$ concentration is measured.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.8
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• pp.954-960
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• 2007

The purpose of this paper is to obtain design method of air-distribution system. Air-distribution system is composed of blower, duct, diffusers and measuring equipment. The air-flow rate from each diffuser is not equal. The air-flow rate is calculated with the combined equations which are Bernoulli's equation, continuity equation and minor loss equations. Inlet condition and outlet condition are adapted in each duct system. Then square difference between function of maximum air-flow rate and minimum air-flow rate is used as an object function. Area of diffuser and velocity are established as constraints. To minimize the object function, the optimization method is used. After optimization the design variables are selected under satisfaction of constraints. The air-distribution system is calculated again with the result of optimized design variable. It is shown that the air-distribution system has the equal air-flow rate from diffusers.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.373-377
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• 2005

The Performance of in-line duct fan depends on the design parameters of impeller and guide vane. such as sweep back angle of impeller, the number of blades, outlet blade angle, guide vane angle etc. In this experimental study total four kinds of impellers having different sweep back angles, $90^{\circ},\;72.5^{\circ},\;55^{\circ},\;37.5^{\circ}$ with 8 guide vanes, different the number of blades, 6ea, 8ea, 10ea, 12ea, different kinds of outlet blade angles, $30^{\circ},\;45^{\circ}.\;60^{\circ}$ and different kinds of guide vane angles, $15^{\circ},\;30^{\circ},\;45^{\circ}$ were selected and their performance measured to investigate the effects of them. The results were non-dimensionalized to compare their performance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1010-1015
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• 2002

Over the last few decades, noise has played a major role in the development of aircraft engines. The dominant noise is generated by the wake interactions of fan and downstream stator. Engine inlet and exhaust ducts are being fitted with liner materials that aid in damping fan related noise. In this paper, the radiation of duct internal noise from duct open ends with liners is studies via numerical methods. The linearized Euler's equations in generalized curvilinear coordinates are solved by the DRP scheme. The far field sound pressure levels are computed by the Kirchhoff integration method. Through comparison of sound directivity from bell-mouth duct with and without liners, it is shown that radiation from engine inlet is affected by liner effects or a soft wall boundary condition.