• Title/Summary/Keyword: Added Mass Effect

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Numerical Simulation of Aerodynamic Characteristics of a Supersonic Projectile (초음속 발사체의 공력 특성에 관한 수치해석)

  • Lim Chae-Min;Lee Jeong-Min;Kim Heuy-Dong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2005.11a
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    • pp.86-89
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    • 2005
  • A computational work has been performed to investigate the aerodynamics of a projectile which is launched from the two-stage light gas gun. A moving coordinate method for a multi-domain technique is employed to simulate unsteady projectile flows with a moving boundary. The effect of a virtual mass is added to the axisymmetric unsteady Euler equation system. The computed results reasonably capture the major flow characteristics which we generated in launching the projectile supersonically, such as the interaction between the shock wave and the blast wave, the interaction between the vortical flow and the barrel shock, and the steady under-expanded jet. The present computational results properly predict the velocity, acceleration, and drag histories of the projectile.

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Effect of Pluronic F-68 and Oxygen Vectors on Cell Growth of Angelica gigas Nakai in Fed-batch Culture

  • Jeon, Su-Hwan;Lee, Sang-Yun;Jo, Ji-Suk;Min, Byeong-Hyeok;Kim, Dong-Il
    • 한국생물공학회:학술대회논문집
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    • 2000.11a
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    • pp.159-162
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    • 2000
  • It has been commonly known that cell growth is inhibited by the lack of dissolved oxygen and mass transfer inhibition of nutrients at stationary phase in fed-batch culture. In this study, Pluronic F-68 and oxygen vectors were added in Angelica gigas Nakai suspension culture in order to enhance cell growth in fed-batch culture. It was observed that the addition of 6%(w/v) Pluronic F-68 promoted cell growth up to 6.1% compared to control and that the use of 4%(v/v) n-hexadecane markedly enhanced cell growth up to 11.4%.

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The Effect of Color Reproduction Properties at TFT-LCD using High Color Reproduction CCFL

  • Han, Jeong-Min;Ok, Chul-Ho;Seo, Dae-Shik
    • Transactions on Electrical and Electronic Materials
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    • v.8 no.5
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    • pp.215-217
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    • 2007
  • Recently, color reproduction properties have attracted lots of attention with mass production of LCD especially corresponding to TV application and achievement of color reproduction properties such as CRT have been considered one of technical goals for high quality display. However, revision of the color reproduction properties only with CF(color filter) have fundamental limitations and resultant decrease in the transmittance of panel causes demand on high brightness of BL(Back Light). In this paper, we present such a method in which by optimization of original light spectrum from the BL source will improves the color reproduction properties corresponding to them of the CRT. When the intensity of RED and Green-Blue from ramp is revised densely, the characteristics different from CCFL(Cold Cathode Fluorescent Lamp) used before become added so that about 11 % of the color reproduction properties is improved compare to the existing LCD panel.

Heat Transfer Enhancement with Surfactants in Horizontal Bundle Tubes on Absorber (계면활성제를 이용한 수평관군 흡수기의 전열촉진)

  • Seol, Won-Sil;Kwon, Oh-Kyung;Moon, Choon-Geun;Yoon, Jung-In
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.8
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    • pp.1097-1103
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    • 2000
  • This research was concerned with the enhancement of heat transfer by surfactant added to the aqueous solution of LiBr. Different horizontal tubes were tested with and without an additive of normal octyl alcohol. The test tubes were a bare tube, floral tube and hydrophilic tube. The additive mass concentration was about 0.05${\sim}$5.5%. The heat transfer coefficient was measured as a function of solution flow rate for the range of 0.01${\sim}$0.034 kg/ms. The experimental results were compared with cases without surfactant. The enhancement of heat transfer by Marangoni convection effect generated by the addition of the surfactant is observed in each test tube. The increase of heat transfer coefficient by surfactant addition is about 35${\sim}$90% for bare tube, 40${\sim}$70% for the floral tube, 30${\sim}$50% for the hydrophilic tube and was higher for the cases with smaller a little solution flow rates.

Removal of Cu and Fe Impurities on Silicon Wafers from Cleaning Solutions (세정액에 따른 실리콘 웨이퍼의 Cu 및 Fe 불순물 제거)

  • Kim, In-Jung;Bae, So-Ik
    • Korean Journal of Materials Research
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    • v.16 no.2
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    • pp.80-84
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    • 2006
  • The removal efficiency of Cu and Fe contaminants on the silicon wafer surface was examined to investigate the effect of cleaning solutions on the behavior of metallic impurities. Silicon wafers were intentionally contaminated with Cu and Fe solutions by spin coating and cleaned in different types of cleaning solutions based on $NH_4OH/H_2O_2/H_2O\;(SC1),\;H_2O_2/HCl/H_2O$ (SC2), and/or HCl/$H_2O$ (m-SC2) mixtures. The concentration of metallic contaminants on the silicon wafer surface before and after cleaning was analyzed by vapor phase decomposition/inductively coupled plasma-mass spectrometry (VPD/ICP-MS). Cu ions were effectively removed both in alkali (SC1) and in acid (SC2) based solutions. When $H_2O_2$ was not added to SC2 solution like m-SC2, the removal efficiency of Cu impurities was decreased drastically. The efficiency of Cu ions in SC1 was not changed by increasing cleaning temperature. Fe ions were soluble only in acid solution like SC2 or m-SC2 solution. The removal efficiencies of Fe ions in acid solutions were enhanced by increasing cleaning temperature. It is found that the behavior of metallic contaminants as Cu and Fe from silicon surfaces in cleaning solutions could be explained in terms of Pourbaix diagram.

Effect of Vitamin C, Germanium Oxide and Selenium Treatment on the during Cultivation of Sprouts (비타민 C와 산화 게르마늄 및 셀레늄이 새싹에 미치는 영향)

  • Cha, Bae-Cheon;Kim, Myung-Dong;Ryu, Hye-Sook
    • The Korean Journal of Food And Nutrition
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    • v.24 no.2
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    • pp.226-232
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    • 2011
  • In this study, for development of functional sprouts, we have investigated the change of antioxidant activity and quantity of vitamin C, germanium and selenium according to the addition of vitamin C, germanium oxide and selenium oxide on the during cultivation of various sprouts. We were cultivated the sprouts using water solution added vitamin C, germanium oxide and selenium oxide on the system of cultivation instrument. Analysis of quantity of vitamin C on control group and treatment group were conducted by HPLC. Quantity of germanium and selenium were analyzed by ICP-MS(Inductively Coupled Plasma-Mass Spectrometer), and antioxidant activities were checked by DPPH method. As a result, quantity of vitamin C, germanium and selenium on the treatment groups have increased tendency compared to the control group. And antioxidant activity of treatment groups showed increasing tendency compared to the control group.

On the Nonlinear Hydrodynamic Forces due to Large Amplitude Forced Oscillations (대진폭강제동요시(大振幅强制動搖時)의 비선형유체력(非線型流體力)에 관한 연구(硏究))

  • J.H.,Hwang;Y.J.,Kim;S.Y.,Kim
    • Bulletin of the Society of Naval Architects of Korea
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    • v.23 no.2
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    • pp.1-13
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    • 1986
  • The nonlinear hydrodynamic forces acting on a two-dimensional circular cylinder, oscillating with large amplitude in the free surface, are calculated by using the Semi-Lagrangian Time-Step-ping Method used by O.M. Faltinsen. In present calculation the position and the potential value of free surface are calculated using the exact kinematic and dynamic free surface boundary condition. At each time step an integral equation is solved to obtain the value of potential and normal velocity along the boundaries, consisting of both the body surface and the free surface. Some effort was devoted to the elimination of instability arising in the range of high frequency. Numerical simulations were performed up to the 3rd or 4th period which seems to be enough for the transient effect to die out. Each harmonic component and time-mean force are obtained by the Fourier transform of forces in time domain. The results are compared with others' experimental and theoretical results. Particularly, the calculation shows the tendency that the acceleration-phase 1st-harmonic component(added mass) increases as the motion amplitude increases and a reverse tendency in the velocity-phase 1st-harmonic component(damping coefficient). The Yamashita's experimental result also shows the same tendency. In general, the present result show relatively good agreement with the Yamashita's experimental result except for the time-mean force.

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Effect of Surface Roughness on Cutting Conditions in CNC lathe C-Axis Milling Arc Cutting (CNC선반 C축 밀링 원호가공에서 절삭조건이 표면 거칠기에 미치는 영향)

  • Shin, Kuk-Sik
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.13 no.4
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    • pp.99-105
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    • 2014
  • The domestic airline industry undertakes the production of finished products by assembling existing self-described components via a design process which involves assembly and production steps, after which many of the finished products are exported. However, high reliability and stability must be guaranteed, because customers require high-precision components at the time of manufacturing. In the aircraft parts industry, the mass production of high-value-added parts is limited. Therefore, a small production scale depending on the part is used, as many types of conventional CNC lathe machines with X-axis and Z-axis as well as Z-axis and C-axis CNC milling are used. The parts also rely on high-pressure air to increase production. The most important factors are good stability during processing, as high-precision parts are required, as noted above. It was found that as the C-axis rotation speed increased, the diameter of the cutting tool decreased with a decrease in the surface roughness, while the workpiece rotation speed increased with an increase in the surface roughness.

Manufacture of Activated Carbon based on Solid Residue after Lignin Pyrolysis (리그닌 열분해 잔류고형물을 원료로 한 활성탄의 제조)

  • Lee, Jong-Jib;Yoon, Sung-Wook;Lee, Byung-Hak
    • Journal of Korean Society of Environmental Engineers
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    • v.22 no.1
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    • pp.133-139
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    • 2000
  • In this study, activated carbon was prepared from solid residue after lignin pyrolysis by using zinc chloride as an activation agent. The steam activation method was adopted to manufacture activated carbon from solid residue after lignin pyrolysis. The effect of process operation variables such as activation temperature, activation time and mass of activation agent added to char on the pore structure and specific surface area of the activated carbon was investigated. Activated carbon with high surface area and well-developed pore structure could be prepared, when solid residue after lignin pyrolysis was mixed with zinc chloride of 300 wt% and then the mixture was activated for 1 hour at $1000^{\circ}C$ in a stream of nitrogen.

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Numerical Study on NO Emission with Flue Gas Dilution in Air and Fuel Sides

  • Cho Eun-Seong;Chung Suk Ho
    • Journal of Mechanical Science and Technology
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    • v.19 no.6
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    • pp.1358-1365
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    • 2005
  • Flue gas recirculation (FGR) is widely adopted to control NO emission in combustion systems. Recirculated flue gas decreases flame temperature and reaction rate, resulting in the decrease in thermal NO production. Recently, it has been demonstrated that the recirculated flue gas in fuel stream, that is, the fuel induced recirculation (FIR), could enhance much improved reduction in NO per unit mass of recirculated gas, as compared to conventional FGR in air. In the present study, the effect of dilution methods in air and fuel sides on NO reduction has been investigated numerically by using $N_2$ and $CO_2$ as diluent gases to simulate flue gases. Counterflow diffusion flames were studied in conjunction with the laminar flamelet model of turbulent flames. Results showed that $CO_2$ dilution was more effective in NO reduction because of large temperature drop due to the larger specific heat of $CO_2$ compared to $N_2$. Fuel dilution was more effective in reducing NO emission than air dilution when the same recirculation ratio of dilution gas was used by the increase in the nozzle exit velocity, thereby the stretch rate, with dilution gas added to fuel side.