• Transactions of the Korean hydrogen and new energy society
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• v.34 no.3
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• pp.274-282
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• 2023

This study conducted direct numerical simulations of the natural convection phenomena of gaseous hydrogen in a physical storage container containing four circular cylinders. Rayleigh numbers (Ra) in the range of 10⁴≤Ra≤10⁶ and a Prandtl number (Pr)=0.69 (gaseous hydrogen) were considered. The main parameter is a horizontal distance of four circular cylinders and the values of ε_h=0.1, 0.2, 0.3, 0.4, and 0.5 are considered. The flow and thermal structures and corresponding heat transfer characteristics are investigated with respect to the transition of the flow regime. The time- and surface-averaged Nusselt number on the cylinder surface and the wall of physical storage container increased by about 57% and 69% according to the Ra and ε_h, respectively. Thus, the horizontal distance has an influence on the heat transfer characteristics on natural convection of gaseous hydrogen.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.1
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• pp.55-63
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• 1997

A numerical investigation has been made for flows in an axisymmetric circular cylinder with an impulsively rotating cone located at the bottom of the container. The axisymmetric container is completely filled with a viscous fluid. Major parameter for the present research is only the vertex angle of the cone, otherwise Reynolds number and aspect ratio of the vessel are fixed. Main interest concerns on the vortex breakdown of meridional circulation by impulsive rotation of the cone with respect to the longitudinal axis of the cylinder. Numerical method has been used to integrate momentum and continuity equations on a generalized body-fitted grid system. The pattern of vortex breakdown is quite different from that in a right circular cylinder with flat endwall disks. The flow visualization photograph of the preceeding work by Escudier is compared with the present numerical results and the two results are in good agreements. Also flow data are plotted to gain a deep understanding for the present phenomena of the vortex breakdown. The conclusions of this work are clearly explained by the classical theory of the vortex flows in a finite geometry.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.98-99
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• 2003

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.6
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• pp.652-658
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• 2004

In this paper, we report the numerical and experimental solutions of the axi-symmetric flows in the axial plane driven by an impingement of fluid from the bottom wall of a circular cylinder. We managed to visualize successfully the flow pattern shown on the vertical plane through the container axis. The numerical results are shown to compare well with the experimental results for the case of infinity Rossby number. The satisfactory agreement between the two results was possible when in the numerics the free surface was treated as a solid wall so that a no-slip condition was applied on the surface. The numerical solutions reveal that inertial oscillation plays an important role at small Rossby numbers, or at a larger background rotation.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.640-645
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• 2003

In this paper, we report the numerical and experimental solutions of the vortical flows driven by an impingement of fluid from the bottom wall of a circular cylinder. We managed to visualize successfully the flow pattern shown on the vertical plane through the container axis. The numerical results are shown to compare well with the experimental results for the case of infinity Rossby number. The satisfactory agreement between the two results was possible when in the numerics the free surface was treated as a solid wall so that a no-slip condition was applied on the surface. The numerical solutions reveal that inertial oscillation plays an important role at small Rossby numbers, or at a large background rotation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.9
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• pp.439-453
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• 2001

This study deals with the free vibration of two identical circular plates coupled with a bounded fluid. An analytical method based on the finite Fourier-Bessel series expansion and Rayleigh-Ritz method is suggested. In the theory, it is assumed that the ideal fluid in a rigid cylindrical container and the two plates are clamped along the plate edges. The proposed method is verified by the finite element analysis using commercial program with a good accuracy. Two transverse vibration modes, namely in-phase and out-of-phase, are observed alternately in the fluid-coupled system when the number of nodal circles increases for the fixed nodal diameter. The effect of gap between the plates on the fluid-coupled natural frequencies sis also investigated.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1265-1272
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• 2011

We performed numerical simulations of the recirculation flow of an electrolyte fluid in a circular container driven by an AC electromagnetic force for solving continuity and momentum equations. We also conducted an experiment to obtain flow data, which were in good agreement with the numerical simulation results. Furthermore, we performed a parametric study on both numerical and experimental aspects and found that the fluid velocity increases with an increase in the electrolyte concentration and magnetic intensity and with a decrease in the fluid depth and AC frequency.

• Journal of Biosystems Engineering
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• v.30 no.4 s.111
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• pp.229-234
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• 2005

Kinetic friction coefficient, bulk density, dynamic and static angle of repose, and terminal velocity of rice husk at the moisture range 7 to $23\%$ w.b. were determined. It could lead to better design and operation of the processing machinery and handling facilities. Friction coefficient was determined from the horizontal traction force measured by pulling the container holding a mass of rice husk on various plate materials. Dynamic angle of repose was calculated from the photos of bulk samples piled by gravity flow on a circular platform. Static angle of repose was determined by measuring the side angle of the bulk material which was left in a cylindrical container after natural discharge of the bulk sample through a circular hole in the bottom plate. Kinetic friction coefficients of rice husk were in the range of $0.254\~0.410,\;0.205\~0.520,\;0.229\~0.400,\;and 0.133\~0.420$ on PVC, mild steel, galvanized steel, and stainless steel, respectively. Bulk density, dynamic and static angle of repose, and terminal velocity were in the range of $91.7\~98.3$ $kg/m^3$, $40.2\~47.6^{\circ},\;52.8\~83.7^{\circ},$ and $1.36\~1.73$ m/s, respectively. These physical properties of rice husk increased linearly as the moisture content increased.

• Journal of Biosystems Engineering
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• v.23 no.6
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• pp.583-590
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• 1998

This study was performed to determine the kinetic friction coefficient bulk density, dynamic and static angle of repose, and terminal velocity of the chopped rice straw in the moisture range of 8~23%, which could be used for better design and operation of the processing machinery and handling facilities. Friction coefficient was determined from the horizontal traction force measured by pulling the container holding the mass of rice straw on the various plate materials. Bulk density was measured with an apparatus consisting of a filling funnel and a receiving vessel. Dynamic angle of repose was calculated from the photos of bulk samples piled by gravity flow on a circular platform. Static angle of repose was determined by measuring the side angle of the bulk material which was left in the cylindrical container after natural discharge of the bulk sample through a circular hole in the bottom plate. Kinetic friction coefficients of rice straw on the PVC, mild steel, stainless steel, and galvanized steel were in the range of 0.303~0.434, 0.222~0.439, 0.204~0.448, and 0.206~0.407, respectively. and indicated linear increase with moisture content. The effects of moisture change on the friction coefficients were in the order of PVC, mild steel, galvanized steel, and stainless steel. Bulk density, dynamic and static angle of repose, and terminal velocity were in the range of 56.8~60.3 kg/m$^3$, 41.4~45.9$^{\circ}$, 94.4~100.8$^{\circ}$, and 1.07~4.48 m/s, respectively, and were increased linearly with the moisture content.

• Korean Journal of Heritage: History & Science
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• v.43 no.3
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• pp.208-241
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• 2010

This study was conducted to examine the chronology of Taesil Seokham(Taesil Stone Boxes) stored in Taesil of the Joseon Palace and classify the styles to discuss how these boxes have developed. By doing so, this study defined the archaeological styles of taesil seokhams in the chronological order. Although taesil seokhams are placed when taesil are first created, they do not have any texts engraved on them and it is difficult to gain information only from examining taesil seokham. However, Taejiseok(memorial stones buried in Taesil) and Agibi(gravestones buried in Taesil) were created along with taesil. These resources were examined and compared with literature records to find when each taesil seokhams was created. The critical elements to consider for the chronological arrangement were both the cover and container of the boxes and the transition of their style could be classified into four major stages. In detail, the Joseon Dynasty's taesil seokhams initially inherited the style of the Goryeo Dynasty to be formed into rectangular boxes. Through the transition of the mid and late 15th Century, the semi-circular cover with cylindrical container became the popular style in the late 15th Century. In the late 16th Century, the style of the previous period was further developed to add some decorative elements, such as projecting ornaments, but the ornaments were added for functional purposes rather than artistic purposes. However, the style went back to the semi-circular cover with cylindrical container in the early 17th Century. From the mid 17th Century, various styles appeared with ornaments only on the cover, cone-shaped cover with no ornament, or mortar-like container. However, a new style of cone-shaped cover with ornament emerged between the early and mid 18th Century and continued to stay until the mid 18th Century. In the mid 18th Century, the cover remained unchanged, but the container became a keyhole-shaped space with one side forming a "ㄷ" shape. However, in the late 18th Century, the most typical style of the semi-circular cover with cylindrical container reappeared to show that this is the most universal style. Last, in the mid 19th Century, the cover changed from semi-circular to rectangular with flat top. After this, the taesil seokhams began to disappear. In terms of style, it can be classified into four stages. In the early Joseon Dynasty, the taesil seokhams were underdeveloped and inherited the style of the Goryeo Dynasty (Stage I; 1401~mid-15C), but Joseon's unique style began to develop from the late 15th Century (Stage II; 1477~1641). After that, partial ornaments were added for adornment (Stage III; 1660~1754), but the typical style reappeared in the late 18th Century to finally degrade in the late Joseon Dynasty of the mid 19th Century (Stage IV; 1790~1874). This arrangement of style and chronology would greatly help archaeologists anticipate the time and owner of taesil seokhams even if only taesil seokhams are discovered without any records. * Tae(胎) : Placenta and umbilical cord * Taesil(胎室) : A facility(chamber) of burying Tae(胎) in rite when royal descendants are born.