• Journal of the Korean Society of Visualization
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• v.6 no.2
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• pp.28-32
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• 2008

Contrary to the flow rate in fully filled pipe flows, the flow rate in partially filled pipe flows is significantly influenced by the variation of water level, channel slop, and so on. The major difference in these two flows results from the existence of a free surface. To make it clear, in the present study, a similarity of the velocity profile in a partially filled circular pipe has been investigated according to the water level. A particle image velocimetry (PIV) technique was applied to measure the three-dimensional velocity profiles. As a result, there is found a similarity of the velocity profile near the central region. However, near the side wall, the similarity is broken due to the interaction between the wall and the free surface.

• 한국가시화정보학회:학술대회논문집
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• 2006.12a
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• pp.73-77
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• 2006

Flow rate measurement is one of the difficult problems in the industrial applications. Especially, flow rate in a partially filled pipeline is affected by many parameters such as water level, channel slop, etc. In the present study, prior to the development of a flowmeter, the flow characteristics has been investigated by particle image velocimetry (PIV) measurements. Three-dimensional velocity distributions were obtained from sectional measurements of velocity profiles according to the water level. As a result, it is found that there is no similarity in the velocity profile when the lateral position is changed. In addition, the maximum velocity does not always occur on the free surface. It depends on the water level. In the aspect of flow rate measurement, the previous calculus based upon point measurement techniques is proved to be inaccurate because of the lack of whole flow information.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.5
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• pp.725-734
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• 2010

This study conducted hydraulic testing to assess the stability of two types of pyramid-shaped artificial reefs (ARs) constructed to promote the growth of shellfish and seaweed. Previous theoretical and hydraulic experimental studies have clearly demonstrated Froude similitude. The results of this study revealed that some dimensionless design parameters affected the stability of both types of artificial reefs under various wave and current field conditions (e.g., surf similarity parameters, water particle velocity, wave pressure). In the fixed bed condition, the dimensionless water particle velocity based on the surf similarity parameter was large (about 0.4), and in the moveable bed condition, the relative water depth based on the dimensionless wave pressure was low (about 0.11). In addition, horizontal wave pressure and uplift pressure varied by relative water depth, demonstrating the tendency for wave pressure to decrease linearly with increased relative depth. These findings indicate that the development of more stable design technology forartificial reefs should be based on long-term data and additional study of sliding due to wave action. The findings also highlight the importance of hydraulic experiments in solving problems that have emerged in the design and construction of artificial reefs.

• Journal of Korean Society of Water and Wastewater
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• v.11 no.1
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• pp.81-87
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• 1997

Coagulation is very important process in water works. The subsequent processes are directly affected by this process. Many factors such as turbidity, alkalinity, pH, hardness, total organic carbon(TOC), velocity gradient and flocculation time effect on coagulation process. Among these factors, specially TOC is being concerned target substance to be removed due to trihalomenthanes(THMs) precursor and alkalinity is being one of the major parameter for removing TOC. We have researched the consumption of coagulant with TOC alkalinity concentration of water and removal efficiency of residual TOC and turbidity with alkalinity. Furthermore we have investigated particle size distributions with velocity gradient and alkalinity. The consumption of coagulant was proportionally increased to TOC and alkalinity concentration and the removal of TOC in Nakdong river water was very difficult more than 150 mg/l in alkalinity but large morecular weight organic such as humic acid could be removed easily. Coagulation of low alkalinity water was more rapidly occured than of high alkalinity water by analyzing the particle size distributions. High alkalinity water needed higher mixing energy for a good coagulation within limited flocculation time.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1998.10a
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• pp.211-221
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• 1998

A digital image processing technique which is able to get the velocity vector distribution of a surface of the spilled oil in the ocean without contacting the flow itself. This technique is based upon the PIV(Particle Imaging Velocimetry) technique and its system mainly consists of a high sensitive camera, a CCD camera, an image grabber, and a host computer in which an image processing algorithm is adopted for velocity vector acquisition. For the acquisition of the advective velocity vector of floating matters on the ocean, a new multi-frame tracking algorithm is proposed, and for the acquisition of the diffusion velocity vector distribution of the spilt oil onto the water surface, a high sensitive gray-level cross-correlation algorithm is proposed.

• Journal of Korean Port Research
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• v.12 no.2
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• pp.291-302
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• 1998

A digital image processing technique which is able to be used for getting the velocity vector distribution of a surface of the spilt oil in the ocean without contacting the flow itself. This technique is based upon the PIV(Particle Imaging Velocimetry) technique and its system mainly consists of a high sensitive camera, a CCD camera, an image grabber, and a host computer in which an image processing algorithm is adopted for velocity vector acquisition. For the acquisition of the advective velocity vector of floating matters on the ocean, a new multi-frame tracking algorithm is proposed, and for the acquisition of the diffusion velocity vector distribution of the spilt oil onto the water surface, a high sensitive gray-level cross-correlation algorithm is proposed.

• Journal of Ocean Engineering and Technology
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• v.14 no.4
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• pp.9-16
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• 2000

This paper deals with the numerical and experimental study on the characteristics of the flow around a sunken vessel. Numerical simulation of the two dimensional steady flow on the midship section are carried out by the CFD code which is developed by using finite volume method and which includes the standard $textsc{k}$-$\varepsilon$ model with standard wall function. A experimental study is also carried out for the 1/100 scale model in circulating water channel. A velocity fields around the ship are measuremed by using particle image velocimetry technique. And the fluid forces acting on the ship hull by uniform current are measured by two axis load cell. The computed and measured velocity fields on the midship section are compared with each other in the view point of velocity dstribution and reattachement length, which shows good agreement in quality. The drag force on the vessel also showed the same tendency in both computational and experimental results. However, the quantitative disagreements are shown due to the three dimensional effect of the experiment. The result are used to determine the functional efficiency and stability of the vessel as a artificial reef.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.1
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• pp.108-117
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• 2011

Old train carriages have been used to create artificial reefs (AR) as part of programs to enhance ocean fisheries and recreational resources. This study conducted hydraulic modeling experiments to estimate the structural stability of a train carriage AR. By applying fixed- and movable-bed conditions and Froude similitude, theoretical and hydraulic experiments revealed major design forces(e.g., water waves and currents). The results of this study showed that some dimensionless design parameters (e.g., surf similarity parameters, water particle velocity, scouring, and deposition) also affect the stability of an AR under various wave and current field conditions. In the fixed-bed condition, movement of the AR occurred when dimensionless water particle velocity based on the surf similarity parameter was larger than about 0.32. In the moveable-bed condition, the settlement depth (field values) of the AR ranged from 6 to 30 cm. The results indicated that characteristics of the sediment/bed condition and the direction of external forces acting on an AR should be considered when selecting AR sites.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.465-470
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• 2006

An experimental investigation is carried out to study 2-phase vertically upward hydraulic transport of solid particles by water and non-Newtonian fluids in a slim hole concentric annulus with rotation of the inner cylinder. Rheology of particulate suspensions in viscoelastic fluids is of importance in many applications such as particle removal from surfaces, transport of proppants in fractured reservoir and cleaning of drilling holes, etc. In this study a clear acrylic pipe was used in order to observe the movement of solid particles. Annular fluid velocities varied from 0.2 m/s to 3.0 m/s. Pressure drops and average flow rate and particle rising velocity are measured. For both water and 0.2% CMC solutions, the higher the concentration of the solid particles is, the larger the pressure gradients become.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.2
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• pp.136-142
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• 2015

The shell and tube heat exchanger is an essential part of a power plant for recovering transfer heat between the feed water of a boiler and the wasted heat. The baffles are also an important element inside the heat exchanger. Internal materials influence the flow pattern in the bed. The influence of baffles in the velocity profiles was observed using a three-dimensional PIV (Particle Image Velocimetry) around baffles in a horizontal circular tube. The velocity of the particles was measured before the baffle and between them in the test tube. Results show that the velocity vectors near the front baffle flow along the vertical wall, and then concentrate on the upper opening of the front baffle. The velocity profiles circulate in the front and rear baffle. These profiles are related to the Reynolds number (Re) or the flow intensity. Velocity profiles at lower Re number showed complicated mixing to obtain the velocities and concentrate on the lower opening of the rear baffle as front wall. Numerical simulations were performed to investigate the effects of the baffle and obtain the velocity profiles between the two baffles. In this study, a commercial CFD package, Fluent 6.3.21 with the turbulent flow modeling, k-${\epsilon}$ are adopted. The path line and local axial velocities are calculated between two baffles using this program.