• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.586-590
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• 2006

This paper presents a new vibration control device by which the mass and damping of a structure is increased equivalently. The vibration control system, named toggle-rotational inertia-viscous damper, can be utilized effectively in applications of small structural drift. Numerical analysis shows that because the relative drift of a structure can be effectively amplified by the toggle system, the device has a great performance in the vibration control without the increase of the damper capacity and size. It is also observed that vibration control effects is caused by the increase of equivalent mass and damping due to the rotational inertia and damping of the device.

• 한국전산유체공학회:학술대회논문집
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• 2004.03a
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• pp.42-48
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• 2004

Numerical simulation of viscous compressible flow in turbomachinery cascade involves many problems due to the complex geometry of blade but also flow phenomena. In the present study, numerical investigations have been performed to examine the three-dimensional flow characteristics inside the transonic linear turbine cascades using a commercial code, FLUENT. Multi-block H-type grids are applied to the high-turning turbine rotor blades and comparisons with the experimental data and the numerical results have been done. In addition, the effects of turbulence models on the prediction of the endwall flows are analyzed in the sense of the flow compressibility.

• The Journal of the Acoustical Society of Korea
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• v.18 no.5
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• pp.28-34
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• 1999

The effects of the viscosity of an adjacent viscous fluid on the characteristics of the elastic waves have been studied theoretically and experimentally. Expressions for the wave speed and attenuation of the elastic waves of transverse motion, such as the torsional wave propagating in a circular cylinder and the Love wave in a layered half-space solid, have been obtained as functions of the viscosity and mass density of the fluid by exact and asymptotic analyses. The theoretical results have been compared with experimental observations, and it has been demonstrated that a device described herein can be used as a sensor for measuring the viscosity of a fluid with a known mass density.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.118-120
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• 2003

The behavior of viscous fingerings caused by an external force is investigated by using a two­phase lattice Boltzmann method. The effects of the modified capillary number, the viscosity contrast, and the modified Darcy-Rayleigh number on the instability of interfaces are found. The calculated wave numbers are in good agreement with the theoretical ones in the range of wave numbers smaller than 10, but the calculated ones tend to become smaller than the theoretical ones in higher wave numbers.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.1 s.232
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• pp.80-86
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• 2005

This study presents numerical solutions of the two-dimensional Navier-Stokes equations for supersonic unsteady flow in a convergent-divergent nozzle with heat addition. The TVD scheme in generalized coordinates is employed in order to calculate the moving shock waves caused by thermal choking. We discuss on transient characteristics, start and unstart phenomena, fluctuations of specific thrust caused by thermal choking and viscous effects. We prove that the control of separation of boundary layer is the most important key problem to prevent the thermal choking.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.7_spc
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• pp.503-508
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• 2016

In this study, effectiveness of seismic retrofitting methods using passive damping devices was investigated through numerical analyses of short-period structures under earthquakes which have short-duration and high-frequency impulse characteristics similar to Geyongju earthquakes. Displacement spectra of elastic systems and ductility demand of inelastic systems were evaluated by increasing viscous or friction damping. The damping devices could reduce responses of the structures with shorter structural period than 0.2s. The earthquakes similar to impulse load did not induce the responses of the structures with longer period than 0.4s, and the effects of the damping devices which generates damping forces proportional to structural responses became insignificant.

• Journal of Ship and Ocean Technology
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• v.7 no.3
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• pp.13-33
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• 2003

This paper presents a numerical study on tip vortex cavitation inception predictions based on non-spherical bubble dynamics including splitting and jet noise emission. A brief summary of the numerical method and its validation against a laboratory experiment are presented. The behavior of bubble nuclei is studied in a tip vortex flow field at two Reynolds numbers, provided by a viscous flow solver. The bubble behavior is simulated by an axisymmetric potential flow solver with the effect of surrounding viscous flow taken into account using one way coupling. The effects of bubble nucleus size and Reynolds number are studied. An effort to model the bubble splitting at lower cavitation numbers is also described.

• Advances in nano research
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• v.7 no.6
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• pp.391-403
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• 2019

In this article the frequency response analysis of curved magneto-electro-viscoelastic functionally graded (CMEV-FG) nanobeams resting on viscoelastic foundation has been carried out. To this end, the study incorporates the Euler-Bernoulli beam model in association with Eringen's nonlocal theory to incorporate the size effects. The viscoelastic foundation in the current investigation is assumed to be the combination of Winkler-Pasternak layer and viscous layer of infinite parallel dashpots. The equations of motion are derived with the aid of Hamilton's principle and the solution to vibration problem of CMEV-FG nanobeams are obtained analytically. The material gradation is considered to follow Power-law rule. This study thoroughly investigates the influence of prominent parameters such as linear, shear and viscous layers of foundation, structural damping coefficient, opening angle, magneto-electrical field, nonlocal parameter, power-law exponent and slenderness ratio on the frequencies of FG nanobeams.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.17 no.4
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• pp.489-498
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• 1988

An analysis has been given for the effect of viscous dissipation on the thermal instability of plane Couette flow between two parallel plates maintained at different constant temperatures. Under the assumption that the principle of the exchange of stabilities holds, stationary disturbance quantities in the form of longitudinal vortices are considered. The magnitudes of disturbance quantities are then represented as fast convergent power series so that the eigenvalue problem for determining the onset conditions of the thermal instability may be reduced to a simplified problem of finding the roots of a $4{\times}4$ determinant. It is shown that as the magnitude of the visucous dissipation increases the flow becomes more susceptible to instabilities, which is in very good agreement with previous results obtained in some related researches.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.23 no.3
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• pp.157-178
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• 2019

The present correspondence is conveyed on to consider the fascinating and novel characteristics of radiative hydromagnetic convective flow of a chemically reacting fluid over an exponentially accelerated inclined porous plate. Exact solutions for the fluid velocity, temperature and species concentration, under Boussinesq approximation, are obtained in closed form by the two term perturbation technique. The interesting parts of thermal dispersing outcomes are accounted in this correspondence. Graphical evaluation is appeared to depict the trademark direct of introduced parameters on non dimensional velocity, temperature and concentration profiles. Also, the numerical assortment for skin friction coefficient, Nusselt number and Sherwood number is examined through tables. The certification of current examination is confirmed by making an examination with past revelations available in composing, which sets a benchmark for utilization of computational approach.