• Proceedings of the KSME Conference
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• 2001.06e
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• pp.392-397
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• 2001

A numerical study is performed to investigate the interaction between subsonic axial turbine blade boundary layer and periodically oncoming rotor induced wakes. An implicit scheme for solving the compressible Navier-Stokes equation is developed, which adopts a 4th-order compact difference for spatial discretiztion, a 2nd order Crank-Nicolson scheme for temporal discretization and the dynamic eddy viscosity model as the subgrid scale model. The efficiency and the accuracy of the proposed method are verified by applying to some benchmark problems such as laminar cylinder flow, laminar airfoil cascade flow and a transitional flat plate boundary layer flow. Computational results show good agreements with previous experimental and numerical results. Finally, flow through a stator cascade is simulated at $Re = 7.5{\times}10^5$ without free-stream turbulence intensity. The velocity fields and skin friction coefficients in the transitional region show similar trends with previous boundary layer natural transition.

• Journal of Advanced Marine Engineering and Technology
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• v.10 no.4
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• pp.50-56
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• 1986

This report deals with a study on the boundary layer characteristics of TP620 hydrofoil in the steady state by using two dimensional boundary layer theory. On the basis of complex velocity and laminar and turbulent boundary layer theory, the author attempts to know some tendency by evaluating the performance characteristic values of TP620 hydrofoil working in a uniform flow. In deriving characteristic values, he calculates numerically velocity, momentum thickness, skin friction coefficient, shape factor, and displacement thickness on the TP620 hydrofoil working at each attack angle in a uniform flow. Applying this present numerical calculation using Thwaites' and Head's method, the results of boundary layer on the hydrofoil are shown to be influenced by surface velocity and attack angle.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.6
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• pp.779-792
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• 1997

Flow characteristics are numerically investigated when a packet of waves consisting of a Tollmien-Schlichting wave and a pair of Squire waves evolves in a flat-plate laminar boundary layer using a large eddy simulation with a dynamic subgrid-scale model. Characteristics of early stage transitional boundary layer flow such as the .LAMBDA. vortex, variation of the skin friction and backscatter are predicted. Smagorinsky constants and the eddy viscosity obtained from the dynamic subgrid-scale model significantly change as the flow evolves. Far Field noise radiated from the transitional boundary layer shows the dipole and quadrupole characteristics owing to the wall shear stress and the Reynolds stresses, respectively.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.3 s.18
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• pp.165-173
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• 2004

Matching inviscid and boundary layer methods are developed for analysis of hypersonic flow with thick boundary layer. The new equations match all the boundary layer properties with a variation in the inviscid solution near the edge, except for the normal velocity. Computational comparison are peformed for incompressible and compressible flows over a flat plate. Results from the present method are compared with Wavier-Stokes solutions. The present results are in good agreement with Wavier-Stokes solutions. They show that the new technique can provide improved predictions of heating rates and skin friction predictions for preliminary design of vehicles where shear layers and entropy layer swallowing are importantfor for preliminary design.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.5
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• pp.635-644
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• 1986

A Compuressible turbulent boundary layer effect of the high temperature, accelerating gas flow through the De-Laval nozzle on combustion chamber pressure is numerically investigated. For this purpose, the coupled momentum integral equation and energy integral equation are solved by the Bartz method, and 1/7 power law for both the turbulent boundary layer velocity distribution and temperature distribution is assumed. As far as the boundary layer thicknesses are concerned, we can obtain reasonable solutions even if relatively simple approximations to the skin friction coefficient and stanton number have been used. The effects of nozzle wall cooling and/or mass flow rate on the boundary layer thicknesses and the combustion chamber pressure are studied. Specifically, negative displacement thickness is appeared as the ratio of the nozzle wall temperature to the stagnation temperature of the free stream decreases, and, consequently, it makes the combustion chamber pressure low.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.397-400
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• 2006

In this study, we experimentally investigate the possibility of skin-friction drag reduction by series of transverse cavities in a turbulent boundary layer flow. The effects of cavity depth (d), cavity length (l) and cavity spacing (s) on the skin friction drag are examined in the range of $Re_{\theta}\;=\;4030\;{\sim}\;7360$, $d/{\theta}_0\;=\;0.13\;{\sim}1.03$, l/d = 1 ~ 4 and s/d = 5 ~ 20. We perform experiments for twenty different cavity geometries and directly measure total drag force using in-house force measurement system. In most cases, the skin friction drag is increased. At several cases, however, small drag reduction is obtained. The variation of the skin ftiction drag is more sensitive to the cavity length than to the cavity depth or cavity spacing, and drag is reduced at $s/l\;{\geq}\;10$ and $l/{\theta}_0\;{\leq}\;0.26$ irrespective of the cavity depth. At $l/\bar{\theta}_0\;=\;0.13$ and s/l = 10, maximum 2% drag reduction is achieved. When the skin friction drag is reduced, there is little interaction between the flows inside and outside cavity, and the flow changed by the cavity is rapidly recovered at the following crest. A stable vortex is formed inside a cavity in the case of drag reduction. This vortex generates negative skin friction drag at the cavity bottom wall. Although there is form drag due to the cavity itself, total drag is reduced due to the negative skin friction drag.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.23 no.3
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• pp.92-96
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• 1997

Nowadays, ceramides have been found to be an important component in the outermost layer of the skin - the stratum corneum. It is undersrood that ceramides play an important role in structure and maintenance of the interellular lipid lamella structure in the SC layer. Thus, many efforts have been made by the cosmetics and pharmaceutical industries to get human skin-identical ceramides or pseudoceramides which show similar performance with natural ceramides. The purpose of our study was to systhesize new pseudoceramides via an effective and economical systhetic pathway and to show their performance of skin restoratio. Four kinds of the new pseudoceramides were synthesized by the reaction of alcoholic amine and alkyl ketene dimer. First of all, PC-4 and PC-5 were synthesized by the reaction of 3-amino-1,2-propanidiol and serinol with alkyl ketene dimer respectively. After that, PC-4R and PC-5R were produced by changign kitone group at $\beta$-position to amide bond of above synthesized PC-4 and PC-5 into hydroxyl group using NaBH4 respectively. Their expected structures were conformed by the NMR, IR spectra, and elemental analysis. A study to show the restoration effectiveness was performed in which human skin was pretreated with high concentration of SDS surfactant solution. Using 0.5% solution of above synthesized pseudoceramides, there was the significantly faster restoration of the damaged than that of placebe itself treatment.

• Journal of Korean Medicine Rehabilitation
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• v.24 no.3
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• pp.111-119
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• 2014

Objectives This study aims to analyze a thermal distribution in biological living tissue during warm needling therapy by using a finite element method. The analysis provides an understanding of warm needling's efficacy and safety. Methods A model which consisted of four-layered tissue and stainless steel needle was adopted to analyze the thermal distribution in living tissue with a bioheat transfer analysis. The governing equation for the analysis was a Pennes' bioheat equation. A heat source characteristic of warm needling therapy was obtained by previous experimental measurements. The first analysis of the time-dependent temperature distribution was conducted through points on a boundary between the needle and the tissue. The second analysis was conducted to visualize the horizontal temperature distribution. Results When heat source's peak temperatures was above $500^{\circ}C$ and temperature rising rates were relatively slow, the peak temperature at skin surface exceeded a threshold of pain and tissue damage ($45^{\circ}C$), whereas when the peak temperature was around $400^{\circ}C$, the peak temperature at the skin surface was within a safe limit. In addition, the conduction of combustion energy from the moxa was limited to the skin layer around the needle. Conclusions The results suggest that the skin layer around the needle can be heated effectively by warm needling therapy, but it appears to have little effect at the deeper tissue. These findings enhance our understanding of the efficacy and the safety of the warm needling therapy.

• Journal of Sensor Science and Technology
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• v.26 no.2
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• pp.141-147
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• 2017

A pressure sensor in pulse measurement system is a core component for precisely measuring the pulse waveform of radial artery. A pulse sensor signal that measures the pulse wave in contact with the skin is affected by the temperature difference between the ambient temperature and skin surface. In this study, we found experimentally that the signal changes of the pressure sensors and a temperature sensor were caused by the temperature of the wrist surface while the pressure sensor was contacted on the skin surface for measuring pulse wave. To observe the signal change of the pulse sensor caused by temperature increase on sensor surface, Peltier device that can be kept at a set temperature was used. As the temperature of Peltier device was kept at $35^{\circ}C$ (the maximum wrist temperature), the device was put on the pulse sensor surface. The temperature and pressure signals were obtained simultaneously from a temperature sensor and six pressure sensors embedded in the pulse sensor. As a result of signal analysis, the sensor pressure was decreased during temperature increase of pulse sensor surface. In addition, the signal difference ratio of pressure and temperature sensors with respect to thickness of cover layer in pulse sensor was increased exponentially. Therefore, the signal of pressure sensor was modified by the compensation equation derived by the temperature sensor signal. We suggested that the thickness of cover layer in pulse sensor should be designed considering the skin surface temperature.

• Journal of Pharmaceutical Investigation
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• v.35 no.4
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• pp.273-278
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• 2005

Nicotine transdermal therapeutic systems $(TTS_S)$ have been regarded as an effective mean to aid smoking cessation. However, most of nicotine $TTS_S$ in the market have some problems such as unpleasant side effects and skin irritation due to the excess amount of the drug permeated and the properties of the additives employed. In order to solve these problems, new nicotine $TTS_S$ were formulated using biocompatible additives. The optimized formula of the drug layer consisted of nicotine, propylene glycol and poloxamer 188 at the ratio of 1.2: 17.0: 2.0. The drug layer had the sickness of $1,250\;{\mu}m$, the pH of 8.12. The skin permeation rate of nicotine from optimized nicotine patch (NP) was $21.5\;{\mu}g/cm^2/h$. Transdermal administration of nicotine patch has been carried out for the determination of pharmacokinetic parameters in rats. Steady-state plasma concentration of nicotine following transdermal application of NP (area of patch = $15\;cm^2$) on the dorsal skin of rats was 143.2 ng/ml and AUC for 24 hrs was 3,022 ng h/ml. In case of $EXODUS^{\circledR}$ and Nicotinell $TTS^{\circledR}$, the steady-state plasma concentration of nicotine and ACU for 24 hrs were 428.9 ng/ml, $9,121\;ng{\cdot}hr/ml$ and 155.3 ng/ml, $3,152\;ng{\cdot}h/ml$, respectively. NP showed the experimental plasma nicotine concentration profile was very similar to the simulated one and had an appropriate skin permeation rate and a steady-state concentration of nicotine, which can show therapeutic blood levels of the drug for 24 hrs without severe side effects.