• The KSFM Journal of Fluid Machinery
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• v.16 no.5
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• pp.5-10
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• 2013

The regenerative pump is a kind of turbomachine which is capable of developing high pressure rise at relatively lower flow rates compared to the centrifugal and axial pumps. Although the efficiency of regenerative pumps is much lower than other turbomachines, still they have been widely used in many industrial applications for working at low specific speeds. There are some theoretical models to analysis the pump performance, however, the effect of the blade angle on the pump performance has not been covered in any model to date. In the present study, experimental study on the regenerative pump performance according to the impeller blade angle and its shape has been carried out. The straight radial blades with forward, backward and chevron blades which have inclined angles of $15^{\circ}$, $30^{\circ}$ and $45^{\circ}$ were tested. The pump performance characteristics as the pressure head, efficiency were obtained depending on the flow rate for every impeller, and their results, expressed in appropriate non-dimensional coefficients, were compared and analysed in detail. From the experimental results, it was found that the pressure head and the efficiency depend strongly on the blade angles as well as the blade type. These experimental data has made it possible to better understand the effects of the blade angle on the pump performance, and widen the applicability of the current performance analysis and design models with including the effect of blade angles.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.4
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• pp.441-448
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• 2004

A numerical study was conducted to show the effect of aspect ratio on the analogy of the developing laminar flows between in orthogonally rotating straight duct and in a stationary curved duct of rectangular cross-section. In order. to clarify the similarity of two nows, dimensionless parameters (equation omitted) and Rossby Ro= $w_{m}$$\Omega$ $d_{h}$, in a rotating straight duct were used as a set corresponding to Dean number, (equation omitted), and curvature ratio, λ=R/ $d_{h}$, in a stationary curved duct. Four. different aspect ratios A=0.25, 0.5, 2 and 4 were considered. Under the condition that the magnitudes of Ro and λ were large enough to satisfy the 'asymptotic invariance property' and the aspect ratio was larger than 1, there were strong quantitative similarities between the two flows such as flow patterns, friction factors, and maximum axial velocity magnitudes fur the same values of $K_{LR}$ and $K_{LC}$ . On the other hand, as the aspect ratio decreased below 1 (A=0.25 and 0.5), the difference of the secondary flow intensity between these two flows was enhanced and therefore the analogy of two flows was not so evident as that of the larger aspect ratio (A=2 and 4). 4).nd 4).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.10
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• pp.631-638
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• 2017

An experimental study was conducted to investigate the effect of a rotor design on the performance characteristics of a slurry pump using the tornado principle. The slurry pump differs considerably in terms of construction as well as operating principle when compared to the conventional centrifugal pump. The design parameters of the cross-shaped rotor included the diameter, thickness and height. The total head, shaft and water powers, and pump efficiency as a function of flow rate were compared with the design parameter. It was found that as the rotor diameter and height increase, the efficiency increases, whereas, an increase in the rotor thickness decreases the efficiency. In the rotor design condition of this study, the specific area and efficiency of the maximum height rotor were, respectively, smaller and higher than those of maximum diameter rotor.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.327-330
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• 2006

This paper represents the numerical analysis on effects of radius ratio in a concentric annulus with a rotating inner cylinder. The numerical model consisted of two cylinder which inner cylinder is rotating and outer cylinder is fix, and the axial direction is used the cyclic condition because of the length for axial direction is assumed infinite. The diameter of inner cylinder is assumed 86.8mm, the numerical parameters are angular velocity and radius ratio. Also, the whole walls of numerical model have no-slip and the working fluid is used water at $20^{\circ}C$. The numerical analysis is assumed the transient state to observe the flow variations by time and the 3-D cylindrical coordinate system. The calculation grid adopted a non-constant grid for dense arrangement near the wall side of cylinder, the standard $k-{\omega}$ high Reynolds number model to consider the effect of turbulence flow and wall, the fully implicit method for time term and the quick scheme for momentum equation. The numerical method is compared with the experimental results by Wereley and Lueptow, and the results are very good agreement. As the results, TVF isn't appeared when Re is small because of the initial flow instability is disappear by effect of the centrifugal force and viscosity. The vortex size is from 0.8 to 1.1 for TVF at various $\eta$, and the traveling distance for wavy vortex have the critical traveling distance for each case.

• ALGAE
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• v.30 no.4
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• pp.313-323
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• 2015

Lipid peroxidation means the oxidative degradation of lipids. The process from the cell membrane lipids in an organism is generated by free radicals, and result in cell damage. Phlorotannins, well-known marine brown algal polyphenols, have been utilized in functional food supplements as well as in medicine supplements to serve a variety of purposes. In this study, we assessed the potential anti-lipid peroxidation activity of phlorofucofuroeckol-A (PFF-A), one of the phlorotannins, isolated from Ecklonia cava by centrifugal partition chromatography in 2,2-azobis (2-amidinopropane) dihydrochloride (AAPH)-stimulated Vero cells and zebrafish system. PFF-A showed the strongest scavenging activity against alkyl radicals of all other reactive oxygen species (ROS) and exhibited a strong protective effect against ROS and a significantly strong inhibited of malondialdehyde in AAPH-stimulated Vero cells. The apoptotic bodies and pro-apoptotic proteins Bax and caspase-3, which were induced by AAPH, were strongly inhibited by PFF-A in a dose-dependent manner and expression of Bcl-xL, an anti-apoptotic protein, was induced. In the AAPH-stimulated zebrafish model, additionally PFF-A significantly inhibited ROS and cell death, as well as exhibited a strong protective effect against lipid peroxidation. Therefore, these results suggest that PFF-A has excellent protective effects against ROS and lipid peroxidation induced by AAPH in both an in vitro Vero cell model and an in vivo zebrafish model.

• ALGAE
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• v.24 no.4
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• pp.257-265
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• 2009

Marine microalgae are a key diet component in finfish and shellfish aquaculture. Cryopreservation of the microalgae is suggested by many other studies as the best method for long-term storage. To test cryopreservation efficacy, 19 taxas of marine microalgal species were examined. In the first experiment we compared dimethylsulfoxide ($Me_2SO$) and glycerol, which are most widely used as cryoprotectant agents (CPAs). The cryopreservation comprised two freezing procedures. Firstly, the samples containing the CPAs were kept at $4^{\circ}C$ for 10 min before being plunged into liquid nitrogen ($-196^{\circ}C$). Secondly, samples containing CPAs were pre-cooled ($-1^{\circ}C$ $min^{-1}$ to $-80^{\circ}C$ before being plunged into liquid nitrogen. Most of the species were successfully cryopreserved using $Me_2SO$, whereas the Prasinophyceae (T. striata and T. suecica) were successfully cryopreserved using glycerol. In general, the cooling method had no influence on the survival of the microalgae except in the case of the Tetraselmis species. In the second experiment, the cultured solution was divided before cryopreservation into concentrated and non-concentrated groups to identify the effect of cell density during cryopreservation. After 12 months of storage, the samples were again divided into centrifugation and non-centrifugation groups to learn the effect of $Me_2SO$ on the culture. Viability and growth of the microalgae were not influenced by cell density or the centrifugal removal of the $Me_2SO$ after thawing.

• Transactions of the KSME C: Technology and Education
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• v.3 no.3
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• pp.183-191
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• 2015

In this study, the finite element analysis was carried out to investigate dynamic characteristics of the AGF(Active Gurney Flap) which is under development for reducing vibration and noise of the helicopter rotor system. The Gurney flap is a kind of small flat plate, mounted normal to the lower surface of the airfoil near to the trailing edge. An electric motor, L-shaped linkages and flap parts were integrated into a rotor bade, and 3~5/rev control was given to the AGF to reduce the vibration in the fixed frame. Thus, an explicit time integration method was adopted to investigate the dynamic response of the AGF with considering both centrifugal force due to the rotor rotation and active control input, and it can be seen that the vertical displacement of the AGF was satisfied to meet the design requirement.

• Journal of the Korean Geotechnical Society
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• v.20 no.4
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• pp.39-47
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• 2004

The SCP(sand compaction pile) method which is a vertical reinforcing technique for soft ground using a sand compaction pile has received increasing popularity in Korea. Currently, there are different methods to evaluate the bearing capacity of the reinforced ground by the SCP method. However, a method that can consider the effect of the replacement ratio on the bearing capacity is not yet available. This study investigated the effect of the replacement ratio on the bearing capacity of the reinforced ground by the SCP method. The study involved laboratory experiments which were conducted on a centrifuge facility. Test conditions included various ranges of replacement ratios (20, 30, and 40%), centrifuged consolidation, and loading. From the results of the study, a method which can evaluate the bearing capacity of the reinforced ground was proposed and verified using the weighted average of the replacement ratio.

• Biomaterials and Biomechanics in Bioengineering
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• v.1 no.2
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• pp.81-93
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• 2014

An in vitro cell study evaluating cell adhesion to hydroxyapatite (HA) coated prosthetic Ti-6Al-4V alloy via laser treatment is presented in comparison with uncoated alloy. Based on our previous in vitro biocompatibility study, which demonstrated higher cell attachment and proliferation with MC3T3-E1 preosteoblast cells, the present investigation aims to reveal the effect of laser coating Ti alloy with HA on the adhesion strength of bone-forming cells against centrifugal forces. Remaining cells on different substrates after centrifugation were visualized using fluorescent staining. Semi-quantifications on the numbers of cells were conducted based on fluorescent images, which demonstrated higher numbers of cells retained on HA laser treated substrates post centrifugation. The results indicate potential increase in the normalized maximum force required to displace cells from HA coated surfaces versus uncoated control surface. The possible mechanisms that govern the enhancing effect were discussed, including surface roughness, chemistry, wettability, and protein adsorption. The improvement in cell adhesion through laser treatment with a biomimetic coating could be useful in reducing tissue damage at the prosthetic to bone junction and minimizing the loosening of prosthetics over time.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.8
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• pp.887-892
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• 2014

In a conventional magnetic abrasive polishing process, the polishing abrasives are mixed with ferrous particles and slight cutting oil to form a cluster of abrasives. However, when a tool rotates at a high revolution speed, most of the polishing abrasives are scattered away from it due to the increase in centrifugal force. This phenomenon directly reduces the polishing efficiency. The use of a highly viscous matter such as silicone gel instead of cutting oil for mixing is one method to solve this problem and increase abrasive adhesion. Another method to avoid high abrasive scattering is the application of wet magnetic abrasive polishing (WMAP). In WMAP, abundant mineral oil is preliminarily applied to the workpiece surface. This study experimentally evaluated the effect of WMAP on abrasive adhesion. The relationship between the amount of working abrasives and polishing conditions was characterized. Despite the lower adhesion ratio of polishing abrasives, the surface roughness was found to be significantly improved as the result of WMAP.