• Journal of Navigation and Port Research
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• v.39 no.3
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• pp.173-178
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• 2015

In these days, the world has been increasing the development of various underwater vehicles such as ROVs (Remotely operated underwater vehicles) and AUVs (Autonomous underwater vehicles). And the importance of submarine's maneuverability is especially being emphasized. Therefore, accurate values of the derivatives in equations of motion are required to control motion of the submarines. The aims of the present study are to experimentally derive Hydrodynamic derivatives derived by the vertical planar motion mechanism (VPMM) model test, and to estimate vertical dynamic stability was estimated by using the linear hydrodynamic derivatives, the hydrodynamic derivatives of the submarine, which have a high propriety, were provided by using the fourier analysis of measured forces and moments. Furthermore it is confirmed that the experimental derivatives shows well agreement with the theoretical estimations, and the dynamic stability of the submarine was estimated as a good state, which implies that the value is greater than zero.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1335-1336
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• 2013

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.766-771
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• 1992

The hydrodynamic coefficients estimation problem is important to develop an underwater vehicle and design a controller for it. In this paper, an identification theory, the Extended Kalman Filter, is applied to this parameter estimation problem. In the case that a process noise is not used, all of the parameters are almost exactly converged to the true values respectively. When a process noise is used, all of the parameters are converged to the true values, too, although some parameter estimates are slightly biased. The comparisons of the two trajectories between those generated by the true parameters and those by the estimated parameters show that the parameter estimation problem is well-solved.

• Journal of the Korean Society for Marine Environment & Energy
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• v.4 no.3
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• pp.28-39
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• 2001

The eco-hydrodynamic model was used to simulation water quality of Kwangyang Bay according to the environmental variation for appropriate water quality management. The mean concentration of COD was 3.3㎎/L, this exceeded the third class of water quality criteria. Waste water discharging loads showed approximately 90% of total pollutant loads. For satisfaction to below 10㎍/L of Chl. a and 2㎎/L of COD, above 35% reduction of present pollutant loads of point sources are needed.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.1-11
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• 2003

The service reliability of power plants strongly depends on the excellent performance and integrity of hydrodynamic bearings. Consequently, the bearings must be properly designed so as to control vibration amplitudes of rotor due to mass unbalance in passing critical speeds and also suppress self-excited vibrations of rotor even over maximum rated speeds. Furthermore, the bearings must be designed so as to maintain required tribological performance even under severe operating conditions. However, various tribological troubles have been experienced in power plants in Japan. The actual troubles are analysed, focusing on not only direct mechanical causes but also specific bearing designs that surfaced the troubles. Furthermore human factors that decided such designs are also studied. The powerful database of troubles and analyses will contribute greatly to designing advanced power plants with enhanced service reliability in the future. To this end, trouble information should be disclosed, shared and transferred limitlessly. Cooperation of users of power plants is essential to making more advanced design specifications, because no one has easier access to operating and trouble information of power plants than users.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.5
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• pp.114-120
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• 2000

Friction forces of piston rings for a typical SI engine were independently measured while excluding the effects of cylinder pressure, oil starvation and piston secondary motion using a floating liner system. Friction patterns, represented by the measured friction forces, were classified into five frictional modes with regard to the combination of predominant lubrication regimes(boundary, mixed and hydrodynamic lubrication) and stroke regions(mid-stroke and dead centers). The modes were identified on the Stribeck diagram of the dimensionless bearing parameter and friction coefficients which were evaluated at the mid-stroke and at the dead centers. And the frictional modes were estimated to the full operation range. The compression rings behave in the mode where hydrodynamic lubrication is dominant at the mid-stroke and mixed lubrication is dominant at the dead centers under steady operating conditions. However, the oil control ring behave in the mode where mixed lubrication is dominant throughout the entire stroke.

• Proceedings of KOSOMES biannual meeting
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• 2001.10a
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• pp.137-144
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• 2001

A Plankton ecosystem model was developed to investigate effects of hydrodynamic processes including advection and diffusion on size-structured phytoplankton dynamics in the mesohaline zone of the York River estuarine system, Virginia, USA. The model included 12 state variables representing the distribution of carbon and nutrients in the surface mixed layer. Groupings of autotrophs and heterotrophs were based on cell site and ecological hierarchy Forcing functions included incident radiation, temperature, wind stress, mean How and tide which includes advective transport and turbulent mixing. The ecosystem model was developed in FORTRAN using differential equations that were solved using the 4th order Runge-Kutta technique. The model showed that microphytoplankton blooms during winter-spring resulted from a combination of vertical advection and diffusion of phytoplankton cells rather than in-situ production in the lower York River estuary.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.9 no.2
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• pp.57-62
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• 1997

Based on the facts that significant parts of the harbor response spectrum usually reside in the vicinity of the Helmholtz mode in the eastern part of Korea. economically feasible redemption measures of seiches for malfunctioned harbors already in service is proposed by extending the wisdom of perforated breakwaters and adjusting the width of entrance channel as a control tool. It turns out that as the entrance channel is getting narrower, the harbor system is getting slender due to the increase of added hydrodynamic length so that harbor response can be effectively diminished and separated from the incident wave spectrum where considerable amount of wave energy is located at the lower frequency range.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.488-491
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• 2004

Numerical analysis of the three dimensional turbulent flow field in a complex valve shape is carried out to confirm the flow field whether the designed valve shape is good or not. The simulation of the incompressible flow in a constant flowrate control valve is performed by using the commercial code, FLUENT/UNS 6.0. The results of flow field show the designed valve has some problems, therefore these will be good data for new valve design.

• Journal of Korean Society on Water Environment
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• v.23 no.5
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• pp.581-590
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• 2007

A float-type weir has been proposed for the control of algal blooms in some of eutrophic reservoirs recently. It is known as a costly and ecologically sound method, but there is little understanding about the sustainability of this low-cost technology for reservoirs that are located in monsoon climate areas where large flood events during the summer cause high water surface fluctuations. The objective of this study was to assess the effectiveness of a skimmer weir aimed at controlling algal blooms in the lacustrine zone and near the drinking water withdrawal structures of Daecheong Reservoir under various hydrodynamic flow conditions. The effect of weir on the control of algal blooms was simulated using a laterally averaged two-dimensional hydrodynamic and eutrophication model that can accommodate vertical displacement of the weir following the water surface fluctuations. Numerical simulations were performed for two different hydrological conditions, 2001 and 2004 for representing drought year and normal year, respectively. The results showed that the weir is very effective method to control algal blooms in the reservoir by curtailing the transport of phosphorus and algae from contaminated inflow to the downstream lacustrine epilimnion during the draught year. However, large flood events occurred in 2004 transported nutrients and algae built upstream of the weir into the downstream euphotic zone by strong entrainments.