• Journal of Ocean Engineering and Technology
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• v.24 no.4
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• pp.47-52
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• 2010

In this paper, the shapes of windsurfing boards are proposed for the promotion of their public utilization. Initially, we investigated the principal dimensions of 1,500 windsurfing boards that were produced in the last six years to categorize the characteristics of the boards. Then, model tests were performed in a circulating water channel to determine the resistance characteristics and the flow phenomena, including the wetness of the decks. After analyzing the principal dimensions and the results of the tests of existing windsurfing boards, we proposed four public board shapes that resulted from changing the shapes of the nose and rail and protecting the deck of free-ride boards from wetness. Finally, we predicted the performance of the four proposed windsurfing boards.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.363-366
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• 2006

Various kinds of ships(Cargo ship, Passenger ship, Training ship, Special ship etc.) are operated to transport cargo or passengers at sea in the world. Most of the important auxiliary machinery which is installed are fluid machinery in those ships. A large percentage of fluid machinery is pumps which are classified turbo and non-turbo type. While much previous research has focused on pumps for shore use, very little is known about ship's pump. In order to develop an understanding of ship's pump, we introduce common pumps used in every ship and special pumps based on ship's type. This exploratory study lays the groundwork for further investigation of ship's pumps

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.401-402
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• 2006

The turbulent flow around a sphere was investigated using two experimental techniques: smoke-wire flow visualization in wind tunnel at Re=5300, 11000 and PIV measurements in a circulating water channel. The smoke-wire visualization shows flow separation points near an azimuthal angle of $90^{\circ}$, recirculating flow, transition from laminar to turbulent shear layer, evolving vortex roll-up and fully turbulent eddies in the sphere wake. The mean velocity field measured using a PIV technique in x-y center plane demonstrates the detailed near-wake structure such as nearly symmetric recirculation region, two toroidal vortices, laminar separation, transition and turbulent eddies. The PIV measurements of turbulent wake in y-z planes show that a recirculating vortex pair dominates the near-wake region.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.5
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• pp.677-683
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• 2008

The electric propulsion system us closely related with the economical efficiency of ship operation. Fuel efficiency is mainly decided by propulsion system such as diesel engine, propulsion motor and steam turbine. The hybrid propulsion system for fishing boat consists of diesel engine and battery as propulsion power source. This paper is to design battery capacity according to power consumption with ship operation condition, and to test the power consumption of model ship in the circulating water channel. As a result. it can be known that the optimum ship operation condition affects the fuel efficiency.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.481-484
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• 2007

Efficiency of geothermal heat exchanger operation has close relation with temperature variation of the aquifer where the exchanger is installed. In the case of long-term operation, temperature distribution of the aquifer would be similar to that of water circulating in the exchanger, which causes the decrease of heat exchange rate. Therefore, the operation period of the heat exchanger should be controlled so that the temperature distribution of the aquifer is recovered. We developed a model to determine the operation period to acquire the optimal efficiency under the given aquifer condition. With this suggested method, when we use closed-loop heat exchanger, the operation efficiency of the geothermal heat exchanger is expected to be maximized by determining the optimal operation period.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 1999.04b
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• pp.381-385
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• 1999

To investigate the influence of the design and operating parameters of the headbox on hydrodynamics, a pilot headbox system and pressure monitoring apparatus were constructed. The pilot headbox system consisted of a circulating water reservoir, centrifugal pump, distributor, step diffusor and slice. The distributor was designed to function as a pressure attenuator. Flow rate to the headbox and MD and CD velocity profiles in the slice zone were monitored using an ultrasonic flowmeter and Pitot tubes, respectively. As the distance from the step diffusor increased, evener CD velocity profile was observed. Wall effect increased with the increase of the velocity. Flow stability in the headbox was evaluated by injecting a dye at the outlet of the distributor. Application of theoretical analysis based on CFD in designing headboxes is briefly discussed.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.312-315
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• 2008

The flow structure behind circular and elliptical type rings embedded in a cross-flow was investigated experimentally using two-frame particle image velocimetry (PIV). The experiments were performed in a circulating water channel with a test section of 0.35m height ${\times}$ 0.3m width ${\times}$ 1.1m length. PIV measurements were carried out with varying the Reynolds number in the range of 4.5 ${\times}$ $10^2$ - 4.5 ${\times}$ $10^3$. In the present study, turbulent flow structures in the stream-wise direction and span-wise direction were investigated. The mean velocity field distribution was obtained by statistical-averaging instantaneous velocity fields. The spatial distributions of turbulent statistics such as turbulent intensities and turbulent kinetic energy were also investigated.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.185-188
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• 2008

In this study, we experimentally investigated that the optimization of pulsating jet to reduce the separated flow region behind the vertical fence. The vertical fence was submerged in the turbulent boundary layer in the circulating water channel and we applied phase averaged PIV method to measure the instantaneous velocity fields around the fence. One cycle of pulsating jet is divided into 20 phases and grabbed total 200 instantaneous velocity fields at each phase. The experiments were performed by varying the frequency, maximum jet velocity and the shape of pulsating jet wave. Pulsating jet was precisely made by piston-type pump controlled by the computer. The obtained results were compared with normal fence flow. From this study, we found there is the specific frequency which is effective in reducing the reattachment region.

• Journal of the Korean Institute of Navigation
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• v.18 no.3
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• pp.11-18
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• 1994

In the present trends at which vessels would be supersizedly designed for adapting special cargoes in order for effective controls of logistics in marine transportation, it brings poor manoeuvrability of ships and makes environmental or economical loss seriously due to accidents of a large scale at sea. International Maritime Organization adopted manoeuvring standards and also recommended manoeuvring booklets for ship operators recently. We attempted to find variation of hydrodynamic derivatives when a bare hull was fitted with propeller and rudder, or propeller only by captive model test in the circulating water channel. On comparing experimental results with theoretical values derived from equations, almost same tenden-cies were found at hull-propeller-rudder and hull-propeller situations. Interactions with rudder displayed well at large drift angles.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.5
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• pp.573-580
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• 2002

Animation and time-resolved analysis of the wake characteristics of 2-D bluff body flows were examinated by applying the multi-vision PIV to square cylinders(three angles of attack: $0^{circ}, 30^{circ} and 45^{\circ}$) and circular cylinders(three rotating speeds: 0rpm, 76rpm, 153rpm) submerged within a circulating water channel $(Re=10^4)$, The macroscopic shedding patterns and their dominant frequencies were discussed in terms of instantaneous velocity, vorticity and turbulent quantities such as turbulent intensity, turbulent kinetic energy and three Reynolds stresses. Particularly the time-averaged distribution of turbulent intensity 'islands' where their peak magnitudes were focused always small regions behind the bodies without noticeable spatial migration were particularly discovered in all cases. And the dominant frequencies of the turbulent quantities in the wake regions were two times larger than those of the velocity and vorticity.