• Journal of Advanced Marine Engineering and Technology
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• v.38 no.2
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• pp.140-146
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• 2014

Stenosis is the drastic reduction in the cross-sectional area of blood vessel caused by accumulations of cholesterol. It affects the blood flow property and structure from the fluid dynamic point of view. To understand the flow phenomenon more clearly, a particle image velocimetry method is used and the fluid dynamic characteristics in a circular channel containing stenosis structure is investigated experimentally in this study. Different stenotic-structured models made of acrylic material are subjected to a pulsatile flow generated by an in-house designed pulsatile pump. The inner diameter of the tube inlet is 20 mm and the length of reduced area for stenosis ranges between 35mm and 40mm. It is circulated continuously through a circular channel by the pump system. Pressure is measured at four different sections during systolic and diastolic phase changes. The phase-averaged velocity field distribution shows a recirculation regime after the stenotic structure. The effects of the stenotic obstructions are found to be more severe when the aspect ratio is varied.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.12
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• pp.1683-1691
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• 2000

In this study, it is numerically revealed that the secondary flow due to the Coriolls force in a straight duct rotating about an axis perpendicular to that of the duct is analogous to that caused by the centrifugal force in a stationary curved duct. Dimensionless parameters $K_{LR}=Re/\sqrt{Ro}$ and Rossby number in a rotating straight duct were used as a set corresponding to Dean number and curvature ratio in a stationary curved duct. When the value of Rossby number and curvature ratio is large, it is shown that the flow field satisfies the `asymptotic invariance property`, that is, there are strong quantitative similarities between the two flows such as friction factors, flow patterns, and maximum axial velocity magnitudes for the same values of $K_{LR}$ and Dean number.

• Journal of Korea Water Resources Association
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• v.42 no.12
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• pp.1079-1089
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• 2009

The objective of this study is to develop the accurate, robust and high resolution two-dimensional numerical model that solves the computationally difficult hydraulic problems, including the wave front propagation over dry bed and abrupt change in bathymetry. The developed model in this study solves the conservative form of the two-dimensional shallow water equations using an unsplit finite volume scheme and HLLC approximate Riemann solvers to compute the interface fluxes. Bed-slope term is discretized by the divergence theorem in the framework of FVM for application of unsplit scheme. Accurate and stable SGM, in conjunction with the MUSCL which is second-order-accurate both in space and time, is adopted to balance with fluxes and source terms. The exact C-property is shown to be satisfied for balancing the fluxes and the source terms. Since the spurious oscillations in second-order schemes are inherent, an efficient slope limiting technique is used to supply TVD property. The accuracy, conservation property and application of developed model are verified by comparing numerical solution with analytical solution and experimental data through the simulations of one-dimensional dam break flow without bed slope, steady transcritical flow over a hump and two-dimensional dam break flow with a constriction.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.9
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• pp.1172-1177
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• 1999

Comparisons of measured turbulence properties in the unburned gas region of turbulent premixed flame stabilized by pilot flame, in cases of combusting and non-combusting flow conditions, are presented. Methane-air premixed jet at fuel equivalence ratio of 0.6 and 1.0 and Reynolds number of 7,000 was diagnosed using two-color laser velocimeter to obtain turbulence statistics. Same set of measurements was repeated at 21 locations within the unburned gas region of both combusting and non-combusting conditions. Velocity data were analyzed to evaluate the spatial distribution of turbulence properties including Reynolds stress, probability densities, joint probability densities and auto correlations. Contrary to assumptions of current theoretical models, significant influence of flame was observed in every property that was studied in the present investigation. The effective viscosity increased ten-fold when flame was on from cold flow values. The effect of mixing on joint probability as well as in turbulence intensity was suppressed by the flame. The measurements suggest that common assumptions of premixed flame model may result in sizable error in prediction of flame length and temperature distribution in near-field.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.38 no.2 s.115
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• pp.43-51
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• 2006

Starch is widely used as an adhesive material in the paper and corrugated board industry. The adhesion problem of corrugated board is categorized by two main parts called zipper board and white glue line. The object of this research is to investigate the factors affecting the adhesion problem by the gelatinization of various starch solutions and dynamic penetration properties measurements of various commercial base paper and handsheets. Flow property of starch solution is affected by sodium hydroxide addition and reaction level. Absorption property of commercial base papers and handsheets is affected by sizing and stock composition. Optimum bonding between top/bottom liners and corrugated medium is accomplished by acceptable flow viscosity of mixed starch solution and proper adsorption characteristic of base paper.

• Preventive Nutrition and Food Science
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• v.22 no.1
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• pp.56-61
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• 2017

Rheological properties of waxy barley flour (WBF) dispersions mixed with various gums (carboxyl methyl celluleose, guar gum, gum arabic, konjac gum, locust bean gum, tara gum, and xanthan gum) at different gum concentrations were examined in steady and dynamic shear. WBF-gum mixture samples showed a clear trend of shear-thinning behavior and had a non-Newtonian nature with yield stress. Rheological tests indicated that the flow and dynamic rheological parameter (apparent viscosity, consistency index, yield stress, storage modulus, and loss modulus) values of WBF dispersions mixed with gums, except for gum arabic, were significantly higher than those of WBF with no gum, and also increased with an increase in gum concentration. In particular, konjac gum at 0.6% among other gums showed the highest rheological parameter values. Tan ${\delta}$ values of WBF-xanthan gum mixtures were lower than those of other gums, showing that there is a more pronounced synergistic effect on the elastic properties of WBF in the presence of xanthan gum. Such synergistic effect was hypothesized by considering thermodynamic compatibility between xanthan gum and WBF. These rheological results suggest that in the WBF-gum mixture systems, the addition of gums modified the flow and viscoelastic properties of WBF, and that these modifications were dependent on the type of gum and gum concentration.

• Journal of Korean Elementary Science Education
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• v.23 no.2
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• pp.152-158
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• 2004

The purpose of this study was to find the difficulties and problems in the carbon dioxide production experiment and to suggest the device for the improvement. Many students have misconception for the smell of carbon dioxide. I found that the smell of carbon dioxide of producting through the experiment didn't concern with the quantity of calcium carbonate. I certificated that the smell of carbon dioxide was related with the concentration of hydrochloric acid. I built two trap applicaing suction in the gas production device to exclude fully the smell of carbon dioxide. So the smell of carbon dioxide was not present by passing the two trap. To find the ideal experimental conditions I perform the experiment step by step. As the result enough carbon dioxide to use for the property experiment was collected under the condition that is 60 mL of 3 molarity hydrochloric acid and 30 g calcium carbonate. I certificated to mesuring flowing quantity of carbon dioxide using the flow meter of carbon dioxide. In the improvement experiment of the property of carbon dioxide, I proposed the experiment device regarding as spreading of the gas and children's interest. To improve the problem of gas production experiment, I proposed the gas certification device using a thread.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.45 no.6
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• pp.44-54
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• 2013

Replacing OMG (old magazine) to ONP (old newspaper) by raising optical property through $CaCO_3$ in-situ precipitation method in white duplex board presents cost reduction and possible drying energy saving. The strength property impairment by the presence of $CaCO_3$ could be supplemented by the fiber furnish treatment or strength polymer addition. In $CaCO_3$ in-situ precipitation of ONP, it was found from morphological study using FlowCAM, an image analyzer, that most of calcium carbonate were formed on the fines, and made the size of the fines larger. For the case of forming calcium carbonate only on the fractionated fines, the size of the fines were the biggest, and there were more clean surface areas available for bonding for the fractionated long fibers when fractionated fibers and fines were regrouped to make paper.

• Journal of the Korea Convergence Society
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• v.12 no.1
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• pp.171-176
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• 2021

The flow analysis by each configuration of automotive muffler in this study was carried out. And it aims at finding the design model that can increase the flow property best. It is shown that model B has the lowest maximum pressure and model C has the largest. Compared with the best flow rate according to the shape of the automotive muffler, model A had the comparatively smooth flow stream at the entrance and exit. However, model B has the largest flow rate in the muffler but the least flow rate in the exit, making it look less efficient. By the flow analysis result according to the muffler configuration, it is thought to design the muffler effectively by looking for the model with more smooth flow. The result of this study can be used to investigate the flow according to the configuration of small car muffler without actual test. It also seems to be helpful in the aesthetic convergent design of small car muffler.

• Transactions of Materials Processing
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• v.29 no.5
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• pp.257-264
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• 2020

This paper is concerned with the influence of the plastic property of the rivet on the numerical prediction of the Self-Piercing Rivet (SPR) Joining. In order to predict the plastic property of the rivet, a ring compression specimen was directly fabricated from the rivet used for the mechanical joining of dissimilar materials, and the FE analysis together with the ring compression test was iteratively carried out by changing the plastic property of the rivet. For reliable FE analysis, a friction coefficient was estimated based on a friction calibration curve, measuring the reductions in inner diameter and height of the ring specimen after the compression test. From each simulation result, the force-displacement curves were then compared from each other so as to obtain the rivet plastic property that shows good agreement with the experimental result. The SPR joining between GA590 1.0t and Al5052 2.0t was conducted, and the numerical prediction was performed with the use of the plastic property evaluated based on the inverse analysis and the one referred from Mori et al. [11]. Comparison of the experiment and the numerical predictions in terms of the interlock and bottom thickness revealed that the reliable evaluation of the plastic property of the rivet is necessary for the trustworthy numerical prediction of the SPR joining.