• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.3
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• pp.269-276
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• 2012

An air core is generated during draining through an axisymmetrically placed circular orifice after rotating a cylindrical tank filled with a liquid. If an air core is generated, the draining flow rate decreases and the draining time increases. In this study, the process of the formation of the air core and internal flow characteristics in a cylindrical tank are studied by numerical methods. Several methods are used in the analysis, and the results are compared with experimental results to obtain the appropriate scheme. Axial, radial, and swirl velocity profiles on a variety of heights are shown graphically, and the internal flow structure is analyzed from the velocity profiles, the vector plot, and the stream function distribution.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.896-902
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• 2018

This study examined the flow and noise inside a sirocco fan for ventilation as a commercial program. To confirm only the location and power of the noise source, flow analysis was performed with steady state flow analysis. Through flow analysis, the flow was observed in the sirocco fan and the velocity vector. The pressure distribution inside was observed with contours. From the results of steady analysis, the position and size of the noise source could be seen using the 'Curle surface acoustic power' and 'Proudman acoustic power'. The Curle surface acoustic power can be used to observe the noise from the surface. The Proudman acoustic power can be used to detect noise generated in the flow region because the position and size of the noise source generated inside the sirocco fan can be seen only in the steady state. Therefore it is necessary to further analyze the unsteady state to check the frequency of the noise generated. This study provides basic data for improving the performance of the Sirocco fan and reducing the noise.

• The KSFM Journal of Fluid Machinery
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• v.7 no.1 s.22
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• pp.36-44
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• 2004

Three-dimensional vortical flow and separated flow topology near the casing wall in an axial flow fan having two different tip clearances have been investigated by a Reynolds-averaged Navier-Stokes (RANS) flow simulation. The simulation shows that the tip leakage vortex formed close to the leading edge of the blade tip on suction side grows in the streamwise direction. On the casing wall, a separation line is formed upstream of the leakage vortex center due to the interference between the leakage vortex and main flow. The reverse flow is observed between the separation line and the attachment line generated downstream of the trailing edge, and increased with enlarging tip clearance. The patterns of a leakage velocity vector including a leakage flow rate are also analyzed according to two tip clearances. It is noted that the understanding of the distribution of a limiting streamline on the casing wall is very important to grasp the characteristics of the vortical flow in the axial flow fan.

• Journal of Power System Engineering
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• v.4 no.4
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• pp.32-40
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• 2000

A study on the fluid flow with ultrasonic forcing was carried out to get the enhancement of turbulence by laying emphasis on the ultrasonic incidence angles and reflectors. A large water tank was made of the transparent acrylic plates and city water of $25^{\circ}C$ was used as working fluid. 7 angles ($30^{\circ},\;45^{\circ},\;60^{\circ},\;90^{\circ},\;120^{\circ},\;135^{\circ},\;150^{\circ}$) as the ultrasonic incidence angle and 4 materials (wood, acryl, glass, iron) as the reflector were selected arid experiments for the above were made. The velocity vector distribution, kinetic energy and turbulence intensity of the turbulence flow fields enhanced by ultrasonic forcing were measured, compared and discussed by using the PIV measurement which was possible to measure the velocities of simultaneous multipoints. In results, it was cleared that the incidence angle of ultrasonic and material of reflector influenced the enhancement of turbulence.

• Wind and Structures
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• v.22 no.6
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• pp.663-684
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• 2016

Conical vortices generated at the corner regions of large-span flat roofs have been investigated by using the Particle Image Velocimetry (PIV) technique. Mean and instantaneous vector fields for velocity, vorticity, and streamlines were measured at three visual planes and for two different flow angles of $15^{\circ}$. The results indicated that conical vortices occur when the wind is not perpendicular to the front edge. The location of the leading edge corresponding to the negative peak vorticity and maximum turbulent kinetic energy was found at the center of the conical vortex. The wind pressure reaches the maximum near the leading edge roof corner, and a triangle of severe suctions zone appears downstream. The mean pressure in uniform flow is greater than that under turbulent flow condition, while a significant increase in the fluctuating wind pressure occurs in turbulent streams. From its emergence to stability, the shape of the vortex cross-section is nearly elliptical, with increasing area. The angle that forms between the vortex axis and the leading edge is much smaller in turbulent streams. The detailed flow structures and characteristics obtained through FLUENT simulation are in agreement with the experimental results. The three dimensional (3-D) structure of the conical vortices is clearly observed from the comprehensive arrangement of several visual planes, and the inner link was established between the vortex evolution process, vortex core position and pressure distribution.

• Membrane Journal
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• v.29 no.5
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• pp.284-291
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• 2019

In this study, for the improvement of flow pattern with the CDI module that had the larger electrodes, it was designed with the rectangular type which is gradually wider from the inlet. Based on this, both the flow pattern of feed solution and dead zone were observed and the internal pressure, streaming line and velocity vector distribution were analyzed through the computational flow dynamics and compared with the experimental results. For all flow rates of 10, 20, 30 mL/min, there were no dead zones and the flow patterns were maintained constant. Therefore, it may be possible that the larger electrodes are applied to the CDI process.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.6
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• pp.1041-1048
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• 2023

Wind LiDAR and Wind Profiler are devices that produce continuous vertical distribution of wind vector in high-resolution data, and their use has recently been increasing. Although the observation and data processing methods of the two devices are similar, differences in wind detection accuracy may occur depending on weather and operation settings. introduce the characteristics of the two instruments and wind calculation methods, and apply the latest instrument verification standards to evaluate their accuracy by comparing them with the wind observed with a radiosonde. Accordingly, a new direction for performance verification following the introduction of equipment and additional necessary complements are presented.

• Wind and Structures
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• v.38 no.2
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• pp.109-118
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• 2024

A solar concentrator is a reflective surface in the shape of a parabola that collects solar rays in a focal area. This concentrator follows the path of the sun during the day with the help of a tracking system. One of the most important issues in the design and construction of these reflectors is the force exerted by the wind. This force can sometimes disrupt the stability of the concentrator and overturn the entire system. One of the ways to estimate the force is to use the numerical solution of the air flow in three dimensions around the dish. Ansys Fluent simulation software has been used for modeling several angles of attack between 0 and 180 with respect to the horizon. From the comparison of the velocity vector lines on the dish at angles of 90 to - 90 degrees, it was found that the flow lines are more concentrated inside the dish and there is a tendency for the flow to escape around in the radial direction, which indicates the presence of more pressure distribution inside the dish. It was observed that the pressure on the concave surface was higher than the convex one. Then, the effect of adding a hole with various diameter of 200, 300, 400, 500, and 600 mm on the dish was investigated. By increasing the diameter up to the optimized size of 400 mm, a decrease in the maximum pressure value in the pressure distribution was shown inside the dish. This pressure drop decreased the drag coefficient. The effect of the hole on the dish was also investigated for the 30-degree angled dish, and it was found that the results of the 90-degree case should be considered as the basis of the design.

• Food Science and Preservation
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• v.17 no.1
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• pp.16-22
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• 2010

To maintain the storage quality of agricultural products, temperature uniformity during cold storage, which is affected by fan flow rate and product arrangement, is important. We simulated and validated a CFD (Computational Fluid Dynamics) model that can predict both airflow and temperature distribution in a cold storage environment. Computations were based on a commercial code (FLUENT 6.2) and two turbulence models. The standard k-$\varepsilon$ model and the Reynolds stress model (RSM) were chosen to improve the accuracy of CFD prediction. To obtain comparative data, the temperature distribution and velocity vector profiles were measured in a full-scale cold storage facility and in a 1/5 scale model. The agricultural products domain in cold storage was modeled as porous for economical computation. The RSM prediction showed good agreement with experimental data. In addition, temperature distribution was simulated in the cold storage rooms to estimate the uniformity of temperature distribution using the validated model.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.7
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• pp.581-588
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• 2014

The inlet/outlet flow in the tube-side of the shell and tube heat exchanger was experimentally measured to investigate the effect of the porous baffle on uniform flow distribution. A 1/3rd scale-downed model of a heat exchanger was used and particle image velocimetry was applied for measuring the instantaneous velocity vector fields. The absolute errors in the flow rate were calculated and compared for the tube-side with and without the porous baffle, by varying the flow rate from 60 to 90 LPM. The results revealed that the porous baffle can improve flow uniformity and reduce the absolute error in the flow rate of the model with the baffle by about 74%, compared to that without the baffle. This result can be used for improving the performance and design of the shell and tube heat exchanger.