• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2004.04a
• /
• pp.111-118
• /
• 2004

For the precise analysis of high velocity impact problem though FEM with element erosive method, the adequate mesh size and critical equivalent plastic strain(EQPS) is chosen prior to the simulation. In this research, it is strongly required from a standpoint that critical EQPS is used to decide whether perforation occurs or not. The optimization of dual armor plate consisting of 4340 steel and 2024 aluminium against a die steel sphere with high-velocity has been suggested using Lagrangian explicit time-integration code, NET2D. The response surface method based on the design of experiment is utilized for the size optimization. The optimized thickness of each layer, in which perforation does not occur, the strength of multi-layer is maximized and total weight is minimized, is obtained at a constant velocity of a pellet with a designated total thickness.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.19 no.2
• /
• pp.19-25
• /
• 1982

Several formulae have been proposed to estimate the viscous resistance of ships by wake surveys. Both the total head and the velocity should be measured. The integration of he total head loss shows over estimations of the resistance by about 10%. Therefore measurements of the velocity are required, which need much more works. A simple method is suggested in this paper to take accout of the velocity-defect from the measured total head. It gives reasonable estimations of the viscous resistance within the experimental accuracy. Experimental data of a low-drag body of revolution in the wind-tunnel and Series 60 model, CB=0.6 in the tank are used to verify the suggested formula.

• Journal of Advanced Research in Ocean Engineering
• /
• v.3 no.3
• /
• pp.102-111
• /
• 2017

This study considered the effects on the seabed of a harbor and quay wall from ship maneuvers in relation to the thruster jet flow and initial velocity. This study also included the engine capacity, RPM, and diameter and pitch of a ship's thruster for a required speed. The impact of a scour hole on the environment of a quay wall was investigated. Based on these results, a risk based analysis was conducted to evaluate different strategies and their consequences. There has been an increase in the loads on the bottom of a harbor during ship maneuvering. This increase is caused by the propeller loads of mooring and unmooring vessels. This indicates a greater number of arrivals and departures of vessels with larger drafts, larger thruster diameters, and larger available thruster power capacities. Another important cause could be an increase in the maneuverability of vessels from the use of bow thrusters. The increasing loads, which cause a higher jet flow above the bottom, can lead to undesirable scour holes.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.05a
• /
• pp.148-151
• /
• 2004

The hardening of concrete after setting is accompanied with nonlinear temperature distribution caused by development of hydration heat of cement. Especially at early ages, this nonlinear distribution has a large influence on the tensile cracking. As a result, in order to predict the exact temperature distribution in concrete structures it is required to examine thermal properties of concrete. In this study, the coefficient of air convection for concrete mix of nuclear power plant, which presents thermal transfer between surface of concrete and air, was experimentally investigated with variables such as velocity of wind and types of form. The coefficient of air convection obtained from experiment increases with velocity of wind, and its dependance on wind velocity is varied with types of form. This tendency is due to a combined heat transfer system of conduction through form and convection to air. The coefficient of air convection for concrete mix of nuclear power plant obtained from this study was well agreed with the existing models.

• Proceedings of the KIEE Conference
• /
• 1987.07b
• /
• pp.1383-1386
• /
• 1987

This paper concerns, the method for velocity of dynamic Image on two dimensional sequence Image which can be obtained from two sample lines on the street. The velocity of a single moving object Is measured by the number of total frame which Is required when an automobile passes over the second sample line through the first sample line. The measured results show that the velocity error Is less than 5% comparing with the value measured by X-band speed gun.

• Structural Engineering and Mechanics
• /
• v.60 no.5
• /
• pp.829-849
• /
• 2016

In this paper, experimental as well as numerical analysis of Glass Fiber Reinforced Polymer (GFRP) laminated composite has been presented under ballistic impact with varying projectile nose shapes (conical, ogival and spherical) and incidence velocities. The experimental impact tests on GFRP composite plate reinforced with woven glass fiber ($0^{\circ}/90^{\circ}$)s are performed by using pneumatic gun. A three dimensional finite element model is developed in AUTODYN hydro code to validate the experimental results and to study the ballistic perforation characteristic of the target with different parametric variations. The influence of projectile nose shapes, plate thickness and incidence velocity on the variation of residual velocity, ballistic limit, contact force-time histories, energy absorption, damage pattern and damage area in the composite target have been studied. The material characterization of GFRP composite is carried out as required for the progressive damage analysis of composite. The numerical results from the present FE model in terms of residual velocity, absorbed energy, damage pattern and damage area are having close agreement with the results from the experimental impact tests.

• 한국전산유체공학회:학술대회논문집
• /
• 2011.05a
• /
• pp.596-600
• /
• 2011

In this numerical analysis, the distortion of flow measurement by inlet velocity profile of orifice flowmeter was investigated. To validate the numerical method, the convergence was monitored and the grid dependency was also checked. realizable k-e model was selected and y+ was about 50 in this calculation. the results shows that the pressure at the pressure tab near pipe wall was changed by inclined inlet velocity profile and it leads to distorted a measurement values of flow through the orifice plate from -3.8% to 9%. Therefore, the fully developed inlet flow was required for accurate flow measurement by orifice flowmeter. If not, the orifice plate installed at wrong location should be re-installed or additional actions should be taken.

• Proceedings of the KIPE Conference
• /
• 1998.07a
• /
• pp.245-248
• /
• 1998

This paper proposes a sensorless velocity estimator using the reduced-order state equation of induction motor based on Kalman Filter. The electrical transients in the stator voltage equations of induction motor are neglected in the reduced-order model. The advantage of using the reduced-order model is to reduce the required number of numerical integrations for filtering the rotor speed. As changing the operating points and the parameters of the induction motor in simulation studies, the behavior of the sensorless velocity estimator as predicted by the reduced-order state equation of induction machine is compared with the behavior predicted by the complete state equation of induction machine.

• Tribology and Lubricants
• /
• v.24 no.6
• /
• pp.343-348
• /
• 2008

In this paper, a CFD (Computational fluid dynamics) code, FLUENT is adopted to investigate accurate flow characteristics for a slipper bearing which is used swash plate type hydraulic axial piston pump. Static pressure and velocity distributions, and velocity vectors are plotted for different film thickness and slipper rotational velocity. In recess region, there exists a doughnut shaped vortex ring. The static pressure distributions are non-uniform and the flow fields are highly asymmetrical under bearing rotation. Therefore the numerical method adopted in this paper can be use in design of hydrostatic components and further studies are required.

• Journal of the korean Society of Automotive Engineers
• /
• v.10 no.5
• /
• pp.54-60
• /
• 1988

This study is a theoretical analysis and experimental effect of oxygen concentration, exhaust velocity and trap inlet temperature on particulate ignition temperature with installation of ceramic filter trap in diesel engine. So the following results are obtained. 1, Based on the fundamental experiments of the regeneration process, the analytical model was developed and the results from the analytical model agreed with the experiments, then the validity of the model was proved. 2, The ignition temperature for accumulated particulate was proportional to the exhaust velocity and it was known that the optimum exhaust velocity was about 15m/sec. 3, The ignition temperature for accumulated particulate was inversely proportional to the oxygen concentration and the trap inlet temperature, and a minimum oxygen concentration of 5% was required to sustain regeneration. 4, This experimental filter trap(EX-66) is found about 30% of smoke reduction efficiency in comparison with existing muffler.