• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.49-58
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• 1998

On the stability of the Timoshenko cantilever column subjected of a compressive follower force, the influences of the moment of inertia of the tip mass at the free end and the characteristics of a translational spring at the free end of the column are studied. The equations of motion and boundary conditions of system are estabilished by using the d'Alembert virtual work of principle. On the evaluation of stability of the column, the effect of the shear deformation and rotatory inertia is considered in calculation. The moment of inertia of the tip mass at the free end of the column is changed by adjusting the distance c, from the free end of the column to the tip mass center. The free end of the column is supported elastically by a translational spring. For the maintenance of the good stability of the column, it is also proved that the constant of the translational spring at the free end must be very large for the case without a tip mass while it must be small for the case with a tip mass. Therefore, it is found that the shape of the tip mass and the characteristic of the spring at the free end are very effective elements for the stability of the column when the columns subjected to a compressive follower force are designed.

• International Journal of Fluid Machinery and Systems
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• v.2 no.4
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• pp.431-438
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• 2009

A Large Eddy Simulation (LES) of the flow in an inducer is carried out under flow rate oscillations. The present study focuses on the dynamic response of the backflow and the unsteady pressure performance to the flow rate fluctuations under non-cavitation conditions. The amplitude of angular momentum fluctuation evaluated by LES is larger than that evaluated by RANS. However, the phase delay of backflow is nearly the same as RANS calculation. The pressure performance curve exhibits a closed curve caused by the inertia effect associated with the flow rate fluctuations. Compared with simplified one dimensional evaluation of the inertia component, the component obtained by LES is smaller. The negative slope of averaged performance curve becomes larger under unsteady conditions. From the conservations of angular momentum and energy, an expression useful for the evaluation of unsteady pressure rise was obtained. The examination of each term of this expression show that the apparent decrease of inertia effects is caused by the response delay of Euler's head and that the increase of negative slope is caused by the delay of inertial term associated with the delay of backflow response. These results are qualitatively confirmed by experiments.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.9
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• pp.813-821
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• 2000

In this paper, we developed modeling of tension and speed dynamics for a two-drum winder in a three span continuous web transport system which had not been previously. Dynamic modeling of the time-varying nonlinear system was derived by considering the effect of the radii and mass moment of inertia in the unwinder and the two-drum winder through winding up the web. After linearizing it, we designed with a variable-gain a PID controller for tension control and a PI controller for speed. Simulation is carried out with the variation of radii and moment of inertia at high speed for the proposed tension control system with the two-drum winder and the variavle-gain a PID controller. Results show good performance of tension control during the speed change speed at a start-up and stop.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.6
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• pp.418-426
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• 2009

The effect of an inertia moment of a pump flywheel on the thermal-hydraulic behaviors of the KALIMER-600(Korea Advanced LIquid MEtal Reactor) reactor pool during an early-phase of a loss of normal heat sink accident was investigated. The thermal-hydraulic analyses for a steady and a transient state were made by using the COMMIX-1AR/P code. In the present analysis a quarter of the reactor geometry was modeled in a cylindrical coordinate system, which includes a quarter of a reactor core and a UIS, a half of a DHX and a pump and a full IHX. In order to evaluate the effects of an inertia moment of the pump flywheel, a coastdown flow whose flow halving time amounts to 3.69 seconds was supplied to a natural circulation flow in the reactor vessel. Thermal-hydraulic behaviors in the reactor vessel were compared to those without the flywheel equipment. The numerical results showed a good agreement with the design values in a steady state. It was found that the inertia moment contributes to an increase in the circulation flow rate during the first 40 seconds, however to a decrease of it there after. It was also found that the flow stagnant region induced by a core exit overcooling decelerated the flow rate. The appearance of the first-peak temperature was delayed by the flow coastdown during the initial stages after a reactor trip.

• Geomechanics and Engineering
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• v.7 no.3
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• pp.263-277
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• 2014

In the conventional design of retaining structures in a seismic zone, seismic inertia forces are commonly assumed to act upwards and towards the wall facing to cause a maximum active thrust or act upwards and towards the backfill to cause a minimum passive resistance. However, under certain circumstances this design approach might underestimate the dynamic active thrust or overestimate the dynamic passive resistance acting on a rigid retaining structure. In this study, a new analytical method for dynamic active and passive forces in c-${\phi}$ soils with an infinite slope was proposed based on the Rankine earth pressure theory and the Mohr-Coulomb yield criterion, to investigate the influence of seismic inertia force directions on the total active and passive forces. Four combinations of seismic acceleration with both vertical (upwards or downwards) and horizontal (towards the wall or backfill) directions, were considered. A series of dimensionless dynamic active and passive force charts were developed to evaluate the key influence factors, such as backfill inclination ${\beta}$, dimensionless cohesion $c/{\gamma}H$, friction angle ${\phi}$, horizontal and vertical seismic coefficients, $k _h$ and $k_v$. A comparative study shows that a combination of downward and towards-the-wall seismic inertia forces causes a maximum active thrust while a combination of upward and towards-the-wall seismic inertia forces causes a minimum passive resistance. This finding is recommended for use in the design of retaining structures in a seismic zone.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.8
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• pp.649-656
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• 2016

Thick composite disks are utilized in the fast-rotating machines such as turbine disks, flywheels, and so on. The effects of rotating speed on the dynamic characteristics of thick composite disks are deeply studied in this paper. The dynamic governing equations of a rotating composite disk including transverse shear and rotary inertia are derived and then formulated into the finite element equation. Isotropic, circumferentially reinforced disk, and radially reinforced disk are selected for the numerical analysis. The inclusion of the transverse shear and rotary inertia into the governing equation of the rotating disks makes the natural frequency reduced as well as the critical speed. The present results show that the rotation of a thick disk may not reduce the effect of transverse shear and rotary inertia depending on anisotropy, thickness ratio and mode, unlike the results reported in other studies.

• Tunnel and Underground Space
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• v.19 no.4
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• pp.348-354
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• 2009

Slug test is a common characterization method that estimates aquifer hydraulic conductivity rapidly and economically. To characterize the hydraulic property near the borehole YS-4 in the Korea Atomic Energy Research Institute (KAERI) site, slug tests were performed, and oscillatory hydraulic responses were observed. We analyzed the observations with the modified Hvorslev and Bouwer&Rice methods considering the casing inertia, and then the results were compared with those from the general Hvorslev and Bouwer&Rice methods. The estimated hydraulic conductivities from the modified methods are ranged from $4.85{\times}10^{-6}$ to $5.44{\times}10^{-6}$ m/sec, but those from the general ones are ranged from $3.10{\times}10^{-6}$ to $3.63{\times}10^{-5}$ m/s, which shows that the oscillatory responses should be analyzed with consideration of the flowing water inertia effect.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.11
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• pp.881-887
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• 2014

This paper presents numerical study on flow and heat transfer characteristics in micro-gap plate heat exchanger. In particular, we investigate the effect of flow inertia on the flow distribution from single main channel to multiple parallel micro-gaps. The flow regime of the main channel is varied from laminar regime (Reynolds number of 100) to turbulent regime (Reynolds number of 10000) by changing the flow rate, and non-uniformity of the flow distribution and temperature field is evaluated quantitatively based on the standard deviation. The flow distribution is found to be significantly affected by not only the header design but also the flow rate of the main channel. It is also observed that the non-uniformity of the temperature field has its maximum at the intermediate flow regime.

• Proceedings of the Korean Society of Rheology Conference
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• 2001.09a
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• pp.158.4-158
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• 2001

• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.385-388
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• 1996

A time delay controller with state feedback is proposed for azimuth motion control of the frictionless positioning device which is subject to the variations of inertia in the presence of measurement noise. The time delay controller, which is combined with a low-pass filter to attenuate the effect of measurement noise, ensures the asymptotic stability of the closed loop system. It is found that the low-pass filter tends to increase the robustness in the design of time delay controller as well as the gain and phase margins of the closed loop system. Numerical and experimental results support that the proposed controller guarantees a good tracking performance irrespective of the variation of inertia and the presence of measurement noise.