• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
• /
• v.5 no.1
• /
• pp.22-28
• /
• 2002

A New concept for the LNG-FPSO ship, with moonpool and bilge step in bottom, is proposed. This concept is investigated with regard to motion reduction and sloshing phenomena of the cargo and operation tanks. The principal dimensions of the ship are $L\timesb B\times D\times t(design)=270.0\times51.0\times32.32\times13.7(m)$, with a total cargo capacity of 161KT; a 98% loading condition is considered for this study. The moonpools and rectangular step at the bilge have been designed for the purpose of decreasing the motion within the tank. For the motion analysis, linearized three-dimensional diffraction theory, with the simplified boundary condition was used. The six-degree of freedom coupled motion responses were calculated for the LNG-FPSO ship. Viscous effects on the roll motion responses of a vessel were taken into account in this calculation program, using an empirical formula suggested by Himeno(1981). The case study for the moonpool size has been conducted using theoretical estimation and the experimental method. For the optimization of the moonpool size and effect of the bilge step, 9 cases of its size, both with and without bilge step, were involved in the study. no motion responses, especially roll motion, for the designed LNG-FPSO ships are much lower than those of other drill ships and shuttle tankers. The limit criterions are satisfied. To check the cargo tank and operation tank sizes, we performed a sloshing analysis in the irregular waves which focuses on the pressure distribution on the tank wall and the time history of pressure and free surface for No.2 and 5 tanks of LNG-FPSO with chamfers. Finally, optimum tank sire was estimated.

• Journal of Ocean Engineering and Technology
• /
• v.26 no.6
• /
• pp.53-58
• /
• 2012

An experimental study on the hydrodynamic performance of a backward bent duct buoy (BBDB) was performed in a 2D wave tank. The BBDB is one of the promising oscillating water column (OWC) types of floating wave energy converters. Two different corner-shaped BBDBs (sharp-corner and round-corner) were used to measure the maximum chamber surface elevations and body motions for various incident wave conditions, and their hydrodynamic characteristics were compared. In order to investigate the effect of the pneumatic pressure inside the chamber, the heave and pitch angle interacted with elevations were compared for both open chamber and partially open chamber BBDBs. From the comparison study, the deviation in the chamber surface elevations between the two shapes of BBDBs was found to be significant near the resonance period, which may be explained by viscous energy loss. It was also found that the pneumatic pressure noticeably affected the chamber surface elevation and body motions.

• Journal of the Korean Chemical Society
• /
• v.40 no.12
• /
• pp.748-755
• /
• 1996

The effects of temperature on the conformational properties of poly(ethylene oxide) (PEO) in aqueous and aqueous urea solutions are reported. The values of intrinsic viscosity and Huggins coefficients for the PEO dissolved in water and urea/water mixtures (urea concentration 0.2, 1, and 2 M) were obtained using a viscometry method and discussed with respect to the change of water structure. At low temperatures (below 22 $^{\circ}C)$, the PEO-water interaction is favorable and the chain can be extended, whereas at higher temperatures (above 24 $^{\circ}C)$, it is less favorable and the chain can be contracted by a hydrophobic hydration, i.e., the PEO-water interaction becomes to be unfavorable with the increase in temperature. As the urea is added to the system, the PEO chain can be more extended and huged by the perturbation of the structured water originating from the unfavorable PEO-water interaction. The effect of temperature on the intrinsic viscosity values shows an Arrhenius behavior. The activation energies of the viscous flow were obtained and discussed.

• Journal of IKEEE
• /
• v.21 no.1
• /
• pp.24-29
• /
• 2017

In this paper, we have developed the nano carbon tile and chip which is based on a reducing process of oxidation and the viscous fluid control, after hardening to the stylene monomer and methylol acrylamide monomer using an acrylic emulsion junction material. Then we can obtain the sphere form structure of diagonal 1~3 mm, they have mixture the acrylic emulsion junction material(45%) and the coconut carbon powder(55%) of size 300~500 mesh for 25~30 min. Finally, if we have dry for the formated carbon including 30~90 minute at $90{\sim}300^{\circ}C$, then be obtained for pure carbon formation of 95%. In order to identify the safety of the friendly circumstance carbon formation, we have tested the far-infrared ratio, energy analysis, gas density and anti-disease germs experiment.

• Tribology and Lubricants
• /
• v.30 no.6
• /
• pp.337-342
• /
• 2014

The reduction of drag torque is an important research issue in terms of improving transmission efficiency. Drag torque in a wet clutch occurs because of the viscous drag generated by the transmission fluid in a narrow gap (clearance) between the friction plate and a separate plate. The objective of this paper is to observe the effects of the friction plate area and the clearance on the drag torque using finite element simulation. The two-phase flow of air and oil fluid is considered and modeled for the simulation. The simulation analysis reveals that as the rotational speed increases, the drag torque generally increases to a critical point and then decreases sharply at a high speed regime. The clearance between the two plates plays an important role in controlling drag torque peak. An increase in the clearance causes a decrease in shear stress; thus, the drag torque also decreases according to Newton's law of viscosity. An observation of the effect of the area of contact between transmission fluid and friction plate shows that the drag torque increases with the contact area. The flow vectors inside the flow channel present clear evidence that the velocity of the fluid flows is faster with a larger friction plate, that is, in the case of a larger contact area. Therefore, the optimum size of the friction plate should be determined carefully, considering both the clutch performance and drag reduction. It is expected that the results from this study can be very useful as a database for clutch design and to predict the drag torque for the initial design with respect to various clutch parameters.

• Journal of the Society of Naval Architects of Korea
• /
• v.58 no.1
• /
• pp.1-9
• /
• 2021

In the present study, the model-scale Propeller Open Water (POW) tests for the propeller of 176K bulk carrier and 8600TEU container ship were conducted through Computational Fluid Dynamics (CFD) simulation. In order to solve the incompressible viscous flow field, the Reynolds-averaged Navier-Stokes (RaNS) equations were employed as the governing equations. The γ-Reθ(gamma-Re-theta) transition model combined with the SST k-ωturbulence model was introduced to describe the laminar-turbulence transition considering the low Reynolds number of model-scale. Firstly, the flow simulation developing over a flat plate was performed to verify the transition modeling, in which the wall shear stresses were compared with experiments and other numerical results. Then, to investigate the effect of the model, the CFD simulation for the POW test was performed and the simulated propeller performance was validated through comparison with the experiment conducted at Korea Research Institute of Ships & Ocean Engineering (KRISO).

• Smart Structures and Systems
• /
• v.23 no.6
• /
• pp.627-639
• /
• 2019

Passive control may not provide enough damping for a stay cable since the control devices are often restricted to a low location level. In order to enhance control performance of conventional passive dampers, a new type of damper integrated with a rotary electromagnetic damper providing variable damping force and a flywheel serving as an inertial mass, called the rotary electromagnetic inertial mass damper (REIMD), is presented for suppressing the cable vibrations in this paper. The mechanical model of the REIMD is theoretically derived according to generation mechanisms of the damping force and the inertial force, and further validated by performance tests. General dynamic characteristics of an idealized taut cable with a REIMD installed close to the cable end are theoretically investigated, and parametric analysis are then conducted to investigate the effects of inertial mass and damping coefficient on vibration control performance. Finally, vibration control tests on a scaled cable model with a REIMD are performed to further verify mitigation performance through the first two modal additional damping ratios of the cable. Both the theoretical and experimental results show that control performance of the cable with the REIMD are much better than those of conventional passive viscous dampers, which mainly attributes to the increment of the damper displacement due to the inertial mass induced negative stiffness effects of the REIMD. Moreover, it is concluded that both inertial mass and damping coefficient of an optimum REIMD will decrease with the increase of the mode order of the cable, and oversize inertial mass may lead to negative effect on the control performance.

• Food Engineering Progress
• /
• v.21 no.2
• /
• pp.126-131
• /
• 2017

Millimeter waves are electromagnetic waves with frequencies of 30-300 GHz (wavelength 1-10 mm), and millimeter wave stimulation affects microorganism growth. The present study stimulated Bacillus subtilis with 60 and 70 GHz millimeter waves during cheonggukjang fermentation and characterized the effects on cheonggukjang quality. Cheonggukjang treated with millimeter wave irradiation showed no significant difference in total bacterial count but generated only 5.52-5.92% viscous substance. Irradiation with 60 GHz millimeter waves yielded bright and intense color values relative to 70 GHz millimeter waves. Examination of the amylase activity and reducing sugar content of finished cheonggukjang revealed that irradiation at 70 GHz inhibited amylase activity in cheonggukjang. Furthermore, irradiation at 70 GHz increased protease activity, whereas irradiation at 60 GHz inhibited the activity. Moreover, the amino acid content changed with millimeter wave irradiation.

• Journal of Industrial and Engineering Chemistry
• /
• v.67
• /
• pp.148-155
• /
• 2018

To get a better understanding of the effect of physicochemical properties and microstructure on $SO_2$ absorption behavior of DESs with different molar ratios of EmimCl and EG (from 2:1 to 1:2), densities (${\rho}$), viscosities (${\eta}$), speeds of sound (u), refractive indices ($n_D$), and thermal decomposition temperatures ($T_d$) of EmimCl-EG DESs were measured and used to obtain the other derived properties, such as thermal expansion coefficient (${\alpha}_p$) and activation energy for viscous flow ($E_{\eta}$). Moreover, FT-IR spectra and in situ variable-temperature NMR spectroscopy were employed to study the microstructures of DESs. Based on physicochemical and spectroscopic properties, the influence of the concentrations of EmimCl on the interactions in DESs was explored to be associated with their $SO_2$ absorption behavior. The results show that the interactions between $Emim^+$ and $Cl^-$ of EmimCl is gradually weakening with increasing the concentration of EG in DESs by forming of hydrogen bond interaction of $O-H{\cdots}Cl^-$, resulting in a decrease of ${\rho}$, ${\eta}$, u, $n_D$, and $T_d$ of DESs, and hindering the charge-transfer interaction of $SO_2$ with $Cl^-$ and deceasing $SO_2$ capture capacity. Moreover, the $SO_2$ absorption capacity of DESs is proportional to their ${\rho}$ and $E_{\eta}$, respectively.

• Composites Research
• /
• v.33 no.6
• /
• pp.329-335
• /
• 2020

In this study, the thermo-rheological behaivors of petroleum pitches with different softening points were studied, and a B-stage phenolic resins/petroleum pitches blends were prepared by adding petroleum pitches to the phenolic resins. As a result, the petroleum pitch with different softening points decreased the fluidity of the petroleum pitch as the Quinoline insoluble (QI) content increased and showed the viscous properties of the solid. In addition, the effect of adding petroleum pitches having different softening points on the thermo-rheological properties of phenolic resins was investigated. When petroleum pitch with a high softening point was added, the fluidity of the phenolic resin was reduced, and the hardening behavior was fast. It was possible to control the curing rate and curing behavior of the phenolic resin by adding petroleum pitches of different softening points. Among them, the phenolic resin mixture to which P-Pitch 2 was added has a higher fluidity than other blends under the same curing temperature condition.