• Title/Summary/Keyword: Viscosity Equation

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Pipeline Transport of Dredged Soils (준설토의 관로유송)

  • 유동훈;김성오;선우중호
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.8 no.1
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    • pp.114-122
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    • 1996
  • Pipeline transport of dredged soils has been widely used for reclamation. In this case the fluid mixed with soils, so called slurries, has very much different characteristics from pure fluids. As the slurry fluid has a peculiar mode in the viscosity, a proper equation of friction factor has to be used which is pertinent to the characteristics of slurry flow for the estimation of pipeline transport of dredged soils. The slurry fluid has the characteristics of Newtonian fluid or non-Newtonian fluid largely depending on the size of particles. In the present study, new forms of pipe friction factor equations have been suggested for both conditions, and using these forms explicit equations have been developed for the computation of relevant pipe diameter and discharge as well as pumping power.

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Friction Characteristics of the Tip Seal in a Scroll Compressor (스크롤 컴프레서 팁실의 마찰특성)

  • Jeong, Bong Soo
    • Tribology and Lubricants
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    • v.30 no.6
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    • pp.370-377
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    • 2014
  • The basic elements in a rotary-type scroll compressor are two identical spiral scrolls containing refrigerant gas. The pressure variations in the compression pockets of a scroll compressor change the forces acting on the orbiting scroll, and these forces affect the dynamic behavior of the compression mechanism parts. To achieve high efficiency, using a self-sealing mechanism as a tip seal mechanism is very effective. Tip seals, which are placed on top of the scroll wraps, accomplish thrust sealing. This study calculates the friction force between the tip seal and the side plate of a scroll compressor using the numerical model considered in the Reynolds equation. The calculated friction force is verified by an experiment using a pin-on-disk apparatus. A hydraulic servo valve that controls the pressure of the oil hydraulic cylinder applies the normal load for the test, and a DC servo motor controls the sliding velocity of the disk. The friction force and normal load are measured by the force sensors attached to the supporting parts. The results show that the theoretical and experimental results are similar and that the friction is influenced by the viscosity of the oil and the sliding velocity of the scroll.

Numerical Study for Kerosene/LOx Supercritical Mixing Characteristics of Swirl Injector (동축와류형 분사기의 케로신/액체산소 초임계 혼합특성 수치적 연구)

  • Heo, Jun-Young;Kim, Kuk-Jin;Sung, Hong-Gye;Choi, Hwan-Seok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.04a
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    • pp.103-108
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    • 2011
  • The turbulent mixing of a kerosene/liquid oxygen coaxial swirl injector under supercritical pressures have been numerically investigated. Kerosene surrogate models are proposed for the kerosene thermodynamic properties. Turbulent numerical model is based on LES(Large Eddy Simulation) with real-fluid transport and thermodynamics over the entire pressure range; Soave modification of Redlich-Kwong equation of state, Chung's model for viscosity/conductivity, and Fuller's theorem for diffusivity to take account Takahashi's compressible effect. The effect of operating pressure on thermodynamic properties and mixing dynamics inside an injector and a combustion chamber are investigated. Power spectral densities of pressure fluctuations in the injector under various chamber pressure are analyzed.

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Research for a factor affecting creep force at Wheel/Rail contact surface of Roller Rig (모의주행성능시험기의 차륜/레일 접촉부 CREEP FORCE에 미치는 영향 인자에 대한 연구)

  • Jeon, Seung-Woo;Koo, Dong-Hoe;Kim, Jae-Chul;Hwang, Seok-Youl
    • Proceedings of the KSR Conference
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    • 2008.11b
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    • pp.606-612
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    • 2008
  • Creep force is one of the only appeared at conventional train which used to be driven by metallic wheel and rail contact. Due to the elastic deformation of wheel/rail contact patch by the weights of wheel and all the components related to it, creep force generates and becomes to the decision factor of critical speed of bogie(or railway vehicle) which is the criteria of avoiding vehicle to be unstable. There are many kind of factors which affect generation of creep force at a wheel/rail contact surface such as viscosity of contact patch, velocity, wheel and rail geometric profile, mechanical properties of wheel and rail. This paper concentrates on a wheelset simple 2 DOF Equation of Motion being exerted. From the simple numerical analysis using linear solution about getting creep force some factors could find roughly. Among the factors geometric parameter could be the one of most important for this study. In the future we'll prolong the range of study to find out method of measuring creep force easily.

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Analytical Techniques for Measurement of Crosslink Densities of Rubber Vulcanizates

  • Son, Chae Eun;Choi, Sung-Seen
    • Elastomers and Composites
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    • v.54 no.3
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    • pp.209-219
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    • 2019
  • It is important to analyze crosslink densities of rubber articles because the physical properties are dependent on the crosslink densities. In this paper, analytical techniques for the measurement of crosslink densities of rubber vulcanizates are described. The most widely used method to measure the crosslink density is a swelling method combined with the Flory-Rehner equation. Application of the interaction parameter (${\chi}$) of rubber and swelling solvent is critical because the crosslink density is absolutely dependent on the ${\chi}$ value. Methods for obtaining ${\chi}$ employ not only solubility parameters of the polymer and swelling solvent but also inverse gas chromatography (IGC). The solubilities of rubbers can be obtained using micro differential scanning calorimetry (${\mu}DSC$), intrinsic viscosity measurement, and UV-visible spectroscopy. Nuclear magnetic resonance (NMR) spectroscopy has been also used for the measurement of the crosslink density using the $T_2$ relaxation time, which is determined by spin-spin relaxation in solid-state NMR. For sulfur-cured rubber vulcanizates, crosslink densities according to the crosslink types of mono-, di-, and polysulfides are measured by treating the rubber samples with a chemical probe composed of thiol and amine compounds. Measurement methods of physical crosslinking by filler, crystallization, and ionic bonding have also been introduced.

Motion Reduction of Rectangular Pontoon Using Sloshing Liquid Damper (슬로싱 액체 댐퍼를 이용한 사각형 폰툰의 운동 저감)

  • Cho, Il-Hyoung
    • Journal of Ocean Engineering and Technology
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    • v.33 no.2
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    • pp.106-115
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    • 2019
  • The interaction between a sloshing liquid damper (SLD) tank and a rectangular pontoon was investigated under the assumption of the linear potential theory. The eigenfunction expansion method was used not only for the sloshing problem in the SLD tank but also for analyzing the motion responses of a rectangular pontoon in waves. If the frictional damping due to the viscosity of the SLD tank was ignored, the effect of the SLD appeared to be an added mass in the coupled equation of motion. The installation of the SLD tank had a greater effect on the roll motion response than the sway and heave motion of the pontoon. One resonance peak for rolling motion showed up in the case of a frozen liquid in the SLD tank. However, if liquid motion in the SLD tank was allowed, two peaks appeared around the first natural frequency of the fluid in the SLD tank. In particular, the peak value located in the low-frequency region had a relatively large value, and the peak frequency located in the high-frequency region moved into the high-frequency region as the depth of the liquid in the tank increased.

Numerical and experimental study on the scale effect of internal solitary wave loads on spar platforms

  • Wang, Xu;Zhou, Ji-Fu
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.12 no.1
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    • pp.569-577
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    • 2020
  • Based on laboratory experiments and numerical simulations, the scale effect of Internal Solitary Wave (ISW) loads on spar platforms is investigated. First, the waveforms, loads, and torques on the spar model at a laboratory obtained by the experiments and simulations agree well with each other. Then, a prototype spar platform is simulated numerically to elucidate the scale effect. The scale effect for the horizontal forces is significant owing to the viscosity effect, whereas it is insignificant and can be neglected for the vertical forces. From the similarity point of view, the Froude number was the same for the scaled model and its prototype, while the Reynolds number increased significantly. The results show that the Morison equation with the same set of drag and inertia coefficients is not applicable to estimate the ISW loads for both the prototype and laboratory scale model. The coefficients should be modified to account for the scale effect. In conclusion, the dimensionless vertical forces on experimental models can be applied to the prototype, but the dimensionless horizontal forces of the experimental model are larger than those of the prototype, which will lead to overestimation of the horizontal force of the prototype if direct conversion is implemented.

Elastic Deformation Induced Preload Change in Tilting Pad Journal Bearing (탄성변형으로 인한 틸팅패드 저널베어링의 예압 변화)

  • Donghyun Lee;Junho Suh
    • Tribology and Lubricants
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    • v.39 no.3
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    • pp.102-110
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    • 2023
  • This study aims to quantify the variation in the performance of a tilting pad journal bearing (TPJB) owing to the elastic deformation of its pad. To this end, we first defined a parameter, "elastic preload", and predicted the changes in the performance of the TPJB, as a function of the preload amount. We used the iso-viscosity Reynolds equation, which ignores the temperature rise due to viscous shear in thin films, and the resultant thermal deformation of the bearing structure. We employed a three-dimensional finite element model to predict the elastic deformation of the bearing pad, and a transient analysis, to converge to a static equilibrium condition of the flexible pads and journal. Conducting a modal coordinate transformation helped us avoid heavy computational issues arising from a mesh refinement in the three-dimensional finite element pad model. Moreover, we adopted the Hertzian contact model to predict the elastic deformation at the pivot location. With the aforementioned overall strategy, we predicted the performance changes owing to the elastic deformation of the pad under varying load conditions. From the results, we observed an increase in the preload due to the pad elastic deformation.

A Study on the Estimation of Discharge in Unsteady Condition by Using the Entropy Concept (엔트로피 개념에 의한 부정류 유량 산정에 관한 연구)

  • Choo, Tai Ho;Chae, Soo Kwon
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.13 no.12
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    • pp.6159-6166
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    • 2012
  • A discharge measurement is difficult in flood season which is especially important in the water resources field and the continuous discharge measurement for all rivers is impossible on the present system. So, the stage-discharge curve has been used for a long time to produce discharge data of rivers. However, there has been problems from a reliability angle due to the fact that this method uses only stage-discharge relationship, although the stage-discharge curve has the convenience. Therefore, a new mean velocity equation was derived by using Chiu's 2D velocity formula of the entropy concept in this paper. The derived equation reflected hydraulic characteristics such as the depth, gravity acceleration, hydraulic radius, energy slope, kinematic coefficient of viscosity, etc. and estimated also a maximum velocity. In addition, this method verified the relationship between a mean and maximum velocity and estimates an equilibrium state ${\phi}(M)$ well presenting properties of a river cross section as the results. The mean velocity was estimated by using the equilibrium state ${\phi}(M)$, and then the discharge was estimated. To prove this equation to be accurate, the comparison between the measured and estimated discharge is conducted by using the measured laboratory data in the unsteady condition flow showing loop state and the results are consistent. If this study is constantly carried out by using various laboratory and river data, this method will be widely utilized in water resources field.

Quality Stability of a Softened, Sea Tangle Paste by Various Hydrocolloids during Storage (Hydrocolloid를 첨가한 연화 다시마 Paste의 품질 안정성)

  • Song Jae-Chul;Park Hyun-Jeong
    • The Korean Journal of Food And Nutrition
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    • v.17 no.3
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    • pp.246-253
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    • 2004
  • This study was carried out to examine softening stability, exponent of Avrami equation, color change, sensory characteristcs during storage when hydrocolloid was added to the sea tangle paste treated with acetic acid and heat treatment. Rate constant of solidification showed the least value of 0.05 in Avrami equation. In addition hardness of the softened sea tangle paste was not changed after two days of storage in case of carrageenan. Rate of hardness in the softened sea tangle paste formulated with carrageenan exhibited the lowest value of 0.28 kg/mm/day. Heat melting spreadability of the softened sea tangle paste showed the highest value in case of carrageenan and its fluid behavior was rheopectic. Viscosity change in the sea tangle paste formulated with carrageenan was the least during storage and its significant difference at the level of p < 0.05 was exhibited. Change of L, a and b value of softened sea tangle formulated with carrageenan during storage was significantly different at level of p<0.05. Color preference, odor, cohesiveness, softerness, process compatibility and overall acceptance of softened sea tangle were revealed to be in best when carrageenan was added. When hydrocolloid was added to the softened sea tangle paste, it showed the positive result in quality and storage stability of softened sea tangle paste. It was extremely effective on softening stability when carrageenan was added to the softened sea tangle paste.