• Proceedings of the KSME Conference
• /
• 2001.06e
• /
• pp.142-147
• /
• 2001

Natural convection of a magnetic fluid is different from that of Newtonian fluids because magnetic body force exists in an addition to gravity and buoyancy. In this paper, natural convection of a magnetic fluids(W-40) in a cubic cavity is examined by numerical and experimental method. One side wall was kept at a constant temperature($25^{\circ}C$), and the opposite side wall was also held at a constant but lower temperature($20^{\circ}C$). Under above conditions, various magnitudes of the magnetic fields were applied up. GSMAC scheme is used for a numerical method, and the thermo-sensitive liquid crystal film(R20C5A) is utilized in order to visualize wall-temperature distributions as an experimental method. This study has resulted in the following fact that the natural convection of a magnetic fluids is controlled by the direction and intensity of the magnetic fields.

• Tribology and Lubricants
• /
• v.16 no.2
• /
• pp.75-83
• /
• 2000

The present paper proposes a new type of an electro-rheological squeeze film damper (ER SFD) of which the damping capacity can be controlled by the application of electric field. The new ER .SFD- is sealed with slotted rings having electrodes at the inside of the constant gap. The ER SFD can provent the problem of electric short which might be occurred in a previous ER SFD. Reynolds lubrication equation for a Newtonian fluid and the end leakage equation for ER fluids are numerically solved to get the pressure distributions and the damping coefficients of the ER SFD. The results show that the damping coefficients greatly increase with increasing the yield shear stress of ER fluid. In addition, the unbalance response analysis of a flexible rotor supported on the new ER SFD implies that the rotor system can be operated with the minimum of rotor amplitude and force transmissibility by controlling the yield shear stress of ER fluids properly.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.4
• /
• pp.495-503
• /
• 2000

The present numerical study investigates flow characteristics and heat transfer enhancement of the viscoelastic non-Newtonian fluid in a 2:1 rectangular duct. The combined effect of temperature-dependent viscosity, buoyancy and secondary flow caused by second normal stress difference are all considered. The Reiner-Rivlin model is used as a viscoelastic fluid model to simulate the secondary flow and temperature-dependent viscosity model is adopted. Three types of thermal boundary conditions involving different combinations of heated walls and adiabatic walls are considered in this study. Calculated Nusselt numbers are in good agreement with experimental results in both the thermal developing and thermally developed regions. The heat transfer enhancement can be explained by the combined viscoelasticity-driven secondary flow, buoyancy-induced secondary flow and temperature-dependent viscosity.

• Journal of ILASS-Korea
• /
• v.15 no.3
• /
• pp.109-114
• /
• 2010

The implementation of gelled propellants systems offers high performance, energy management of liquid propulsion, storability, and high density impulse of solid propulsion. The present study focused on the macroscopic spray characteristics of liquid sheets formed by triplet impinging jets of non-Newtonian liquids which are mixed by Carbopol 941 0.5%wt. The results are compared to experiments conducted on spray images which formed by triplet impinging jets concerning with airassist effect at center orifice. When gel propellants are injected by doublet impinging jets at low pressure and high pressure, closed rim pattern shape appeared by polymeric effect from molecular force and showed inactive atomization characteristics, because of extensional viscosity related by restriction of atomization process and breakup time delay of turbulence transition. As increasing mass flow rate of the air(increasing GAR), spray breakup level is also increased.

• Korea-Australia Rheology Journal
• /
• v.21 no.3
• /
• pp.175-183
• /
• 2009

This article describes the numerical investigation of blood flow in the stenosed artery bifurcation with acceleration of the human body. Using the commercial software FLUENT, three-dimensional analyses were performed for six simulation cases with different body accelerations and bifurcation angles. The blood flow was considered to be pulsation flow, and the blood was considered to be a non-Newtonian fluid based on the Carreau viscosity model. In order to consider periodic body acceleration, a modified, time-dependent, gravitational-force term was used in the momentum equation. As a result, flow variables, such as flow rate and wall shear stress, increase with body acceleration and decrease with bifurcation angle. High values of body acceleration generate back flow during the diastolic period, which increases flow fluctuation and the oscillatory shear index at the stenosis.

• Applied Chemistry for Engineering
• /
• v.30 no.4
• /
• pp.445-452
• /
• 2019

Shear thickening is an intriguing phenomenon in the fields of chemical engineering and rheology because it originates from complex situations with experimental and numerical measurements. This paper presents results from the numerical modeling of the particle-fluid dynamics of a two-dimensional mixture of colloidal particles immersed in a fluid. Our results reveal the characteristic particle behavior with an application of a shear force to the upper part of the fluid domain. By combining the lattice Boltzmann and discrete element methods with the calculation of the lubrication forces when particles approach or recede from each other, this study aims to reveal the behavior of the suspension, specifically shear thickening. The results show that the calculated suspension viscosity is in good agreement with the experimental results. Results describing the particle deviation, diffusivity, concentration, and contact numbers are also demonstrated.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.9
• /
• pp.405-413
• /
• 2020

The normal stress of cement paste measured under squeeze flow is divided into an elastic solid region at strains between 0.0003 and 0.003 and a strain-hardening region at strains of 0.003 and 0.8. A modeling equation at the strain-hardening region was proposed. First, from the viewpoint of fluid behavior, the power-law non-Newtonian fluid model, with a power-law consistency (m) of 700 and a power index (n) of 0.2, was applied. The results showed good agreement with the experimental results except for an elastic solid region. Second, from the viewpoint of ductile yielding solid behavior, the force balance model was applied, and the friction coefficient between the sensor part measuring the load and the surface of the cement paste was derived as a polynomial of the normal strain by applying the half-interval search method to the experimental data. The results showed good agreement with the experimental results only in the middle normal strain region at strains between 0.003 and 0.3. The rheological behavior of the cement paste under squeeze flow was more consistent with the experimental results from the viewpoint of power-law non-Newtonian fluid behavior than from the viewpoint of ductile yielding solid behavior in the strain-hardening region.

• Journal of Adhesion and Interface
• /
• v.14 no.4
• /
• pp.183-191
• /
• 2013

In order to elucidate the granular heaping phenomenon, the movement behaviors of 3 different types of granule (millet, sand and thin foil disc) have been investigated by applying the vertical or the rotational vibration to each of the 3 vessels, respectively containing one of the 3 types of granule. In case of vertical vibrations, all of them showed the heaping phenomenon like Gerner's simulation, and that in the order of the millet, sand and thin foil disc, regardlessly of weight. Especially, a heaping of disc granules was proven to be relatively delayed, and that with several small complex clutters. For rotational vibration, the central area of vessel turned out to rise up due to the repulsive force by vessel wall as well as the collision between elastic granules, right after the turning point of vibration. Even spiral pattern was made when the rotational vibration amplitude got higher. From these facts, one can see that the heaping be characterized by the inclusion of attractive granules as well as the vibrational type applied to granule vessel.

• Journal of English Language & Literature
• /
• v.57 no.6
• /
• pp.939-958
• /
• 2011

Ezra Pound has an idea of poetry as a field of energy in which words interact with each other with kinetic energy. The energy field which Pound creates in his poem is analogous to the theory of electromagnetism developed by Michael Faraday and James Maxwell, who look upon the space around magnets, electric charges and currents not as empty but as filled with energy and activity. Pound argues that "words are charged with force like electricity," demonstrating that words charged with their own images or energies of positive or negative valence interact one another. This idea is similar to Faraday's concept of "line of force" which he used to represent the disposition of electric and magnetic forces in space. Pound's concept of "image" as an "intellectual and emotional complex in an instant" is remarkably consonant with the confluence of electric and magnetic fields that are coupled to each other as they travel through space in the form of electromagnetic waves. The instant profusion of conception and perception, much like that of electric and magnetic fields, enables Pound to move beyond the sequential and linear hierarchy in time and space. Particularly, Maxwell's stunning discovery that the electromagnetic waves propagate in space at 'the speed of light' has allowed Pound a relativistic sense of escape from the limitations of Newtonian absolute time and space. Pound's poetry transcends any geographical space and sequential time by rendering and juxtaposing images simultaneously. Pound was fully aware of light and electricity fundamental to what he called his world "the electric world." Pound's experiments in Imagism and Vorticism can be considered an attempt to rediscover a place for poetry in the modern world of science and technology. Almost all the appliances that we think of today as modern were laid down in the closing decades of the 19th century and the first decades of the 20th century, in response to the availability of electromagnetic energy. This paper explores how Pound responded to the age of modern technology and science, examining his conception of "image" through his many analogies and similes drawn from electromagnetism. Pound's imagist poetics and poetry come to embody, not only the characteristics of the electric age in the early twentieth century, but the principles of electromagnetism the electric age is based upon.

• Journal of the Korean Magnetics Society
• /
• v.11 no.6
• /
• pp.245-249
• /
• 2001

Natural convection of a magnetic fluid is different from that of Newtonian fluids because magnetic body force exists in an addition to gravity and buoyancy. In this paper, natural convection of a magnetic fluids (W-40) in annular pipes was studied by experimentally. Inside wall was kept at a constant temperature (25 $^{\circ}C$), and outside wall was also held at a constant but lower temperature (20 $^{\circ}C$). The magnetic fields of various magnitude were applied up. This study has resulted in the following fact that the natural convection of a magnetic fluids was controlled by the direction and intensity of the magnetic fields.