• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.4
• /
• pp.336-343
• /
• 2009

Secondary flow losses can be as high as 30~50% of the total aerodynamic losses generated in the cascade of a turbine. Therefore, these are important part for improving a turbine efficiency. As well, many studies have been performed to decrease the secondary flow losses. The present study deals with the leading edge fences on a wing-body to decrease a horseshoe vortex, one of the factors to generate the secondary flow losses, and investigates the characteristics of the generated horseshoe vortex as the shape factors, such as the installed height, and length of the fence. The study was investigated using $FLUENT^{TM}$. Total pressure loss coefficient was improved about 4.0 % at the best case than the baseline.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.34 no.4
• /
• pp.1043-1052
• /
• 2014

This paper deals with in-plane free vibrations of the horseshoe circular arch. Simultaneous ordinary differential equations governing free vibration of the arch are derived with respect to the radial and tangential deformations. Particularly, differential equations are obtained under the arc length coordinate rather than the angular one in order to extend the horseshoe arch whose subtended angle is greater than ${\pi}$ radians. The differential equations are numerically solved for calculating the natural frequencies accompanying with the corresponding mode shapes. In parametric studies, effects of the rotatory inertia, slenderness ratio and circumferential arc length ratio on frequency parameters are extensively discussed.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.20 no.4
• /
• pp.1458-1471
• /
• 1996

The present study is concerned with the heat transfer enhancement associated with a symmetrical or asymmetrical horseshoe vortex in front of and around the circular cylinder centered between the side walls of a wind tunnel. The static pressure measurements and the flow visualization in front of and around cylinders have been performed to determine the existence of horseshoe vortex. The hue-capturing method using the thermochromatic liquid crystals with great spatial resolution was used to obtain the local information of the endwall heat transfer coefficients. In case of one cylinder, the convective heat transfer coefficients of the region where the horseshoe vortex exists are larger than those of any other region. In case of two cylinders with tandem arrangement, the heat transfer rate of gap spacing (d/D= 1.5) is higher than that of gap spacings (d/D=2.0 or 2.5).

• Journal of the Korean Society of Propulsion Engineers
• /
• v.13 no.2
• /
• pp.26-34
• /
• 2009

Secondary flow losses can be as high as 30~50% of the total aerodynamic losses for a turbo-machinery blade or stator row. These are important part for improving a turbine efficiency. Therefore, many studies have been performed to decrease the secondary flow losses. The present study deals with the chamfered leading-edge at a generic wing-body junction to decrease the horseshoe vortex, one of factors to generate the secondary flow losses, and investigates the vortex generation and the characteristics of the horseshoe vortex with the chamfered height, and depth of the chamfer by using $FLUENT^{TM}$. It was found that the total pressure loss for the best case can be decreased about 1.55% compare to the baseline case.

• Journal of Korean Ophthalmic Optics Society
• /
• v.18 no.2
• /
• pp.187-191
• /
• 2013

Purpose: This study was done to understand the visual system of bat by analyzing the distribution of middle/long (ML) opsin cone photoreceptors in the retina of the greater horseshoe bat. Methods: Experiments have been performed by standard immunocytochemical techniques on retina of the greater horseshoe bat Rhinolophus ferrumequinum. Results: The estimated numbers of ML cones were $27,336{\pm}2,130$ cells and the mean density of them was $7,854{\pm}268cells/mm^2$ among the four retinas. S opsin was appeared a little immunoreactivity in the outer segments of outer nuclear layer of cones. Conclusions: From the well organized spatial distributions of ML opsin and the immunoreactivity of S opsin in the retinas, the greater horseshoe bats have the functions not only reacting in the photopic vision but being able to distinguish the colors.

• Journal of Korean Ophthalmic Optics Society
• /
• v.19 no.3
• /
• pp.413-418
• /
• 2014

Purpose: The objective of this study was analyzing the distribution of the excitatory neurotransmitter glutamate receptor to investigate the function in the retina of the greater horseshoe bat. Methods: After retinal tissues of adult greater horseshoe bat were cut into $40{\mu}m$ vertical sections, standard immuno-cytochemical techniques was applied for analysis. Immunofluorescence images were obtained using the Bio-Rad MRC 1024 laser scanning confocal microscope. Results: AMPA (GluR1-4), Kainate (GluR5-7, KA1-2) and NMDA (1, 2A, 2B) mainly distributed in the inner plexiform layer and outer plexiform layer. KA1 receptors have existed not only plexiform layer but also ganglion cell layer. Conclusions: The greater horseshoe bat has same neuron and neurotransmitter to mammalian retina. These findings suggest that bat has a functional retina for visual analysis.

• Journal of computational fluids engineering
• /
• v.8 no.2
• /
• pp.49-56
• /
• 2003

Three-dimensional endwall flow within a linear cascade passage of high performance turbine blade is simulated with a 3-D Navier-Stokes CFD code (MOSA3D), which is based on body-fitted coordinate system, pressure-correction and finite volume method. The endwall flow characteristics, including the development and generation of horseshoe vortex, passage vortex, etc. are clearly simulated, consistent with the generally known tendency. The effects of both turbulence model and convective differencing scheme on the prediction performance of endwall flow are systematically analyzed in the present paper. The convective scheme is found to have stronger effect than the turbulence model on the prediction performance of endwall flow. The present simulation result also indicates that the suction leg of the horseshoe vortex continues on the suction side until it reaches the trailing edge.

• Journal of computational fluids engineering
• /
• v.8 no.3
• /
• pp.1-6
• /
• 2003

Three-dimensional endwall flow within a linear cascade passage of high performance turbine blade is simulated with a 3-D Wavier-Stokes CFD code (MOSA3D), which is based on body-fitted coordinate system, pressure-correction and finite volume method. the endwall flow characteristics, including the development and generation of horseshoe vortex, passage vortex, etc. are clearly simulated, consistent with the generally known tendency The effects of both turbulence model and convective differencing scheme on the Prediction performance of endwall flow are systematically analyzed in the present paper. The convective scheme is found to have stronger effect than the turbulence modei on the prediction performance of endwall flow. The present simulation result also indicates that the suction leg of the horseshoe vortex continues on the suction side until it reaches the trailing edge.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.23 no.11
• /
• pp.1418-1425
• /
• 1999

Flow over a protruding surface is investigated using numerical simulation. We consider flow between two parallel plates with a cube mounted on one side of the channel. As the flow approaches the cube, the adverse pressure gradient produces three-dimensional boundary-layer separation, resulting In the formation of horseshoe vortices. The objective of our study is to clarify both the steady and the unsteady characteristics of the vortex system. As the Reynolds number increases, the structure of the vortices near the cube becomes complex and the number of vortices increases. The distribution of skin friction on the cube-mounted wall reflects the effect of the horseshoe vortices. All these results are consistent with the experimental findings currently available.

• Journal of Chest Surgery
• /
• v.49 no.6
• /
• pp.475-477
• /
• 2016

Elevated carbohydrate antigen (CA) 19-9 can indicate malignancies of the gastrointestinal, pancreatic, and biliary tracts, and be found in a pulmonary sequestration. A 30-year-old man visited Seoul National University Bundang Hospital due to elevated CA 19-9 levels, representing pulmonary sequestration of the bilateral lower lobes, which were connected with each other. We performed left lower lobectomy and division of the systemic arteries. After operation, CA 19-9 levels decreased to normal range, even though a small amount of sequestrated lung remained in the right lower lobe. It is not uncommon that presence of pulmonary sequestration might elevate serum CA 19-9 levels; however, horseshoe type bilateral pulmonary sequestration is very rare.