• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.4
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• pp.1-9
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• 2022

In the current study, in order to understand the dynamic response characteristics of the system according to the external acoustic forcing, a numerical approach was developed by adding an sign-sweep forcing function to the existing network model. Through this model, the sensitivity of frequency and pressure amplitude changes according to system parameters such as the physical dimensions and boundary conditions of the target combustor was analyzed in a wide frequency range. Analysis results of dynamic response characteristics of the target combustor are shown that the frequency regime with high dynamic pressure response was similar to the instability frequency range measured in the same combustor, and in particular, the response of the system depends greatly on the location of the acoustic forcing source term.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.5
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• pp.1-11
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• 2001

The purpose of this study is to develop the main program and pre/post processor for the geometric and plastic non-linear analysis of steel jacket structures subjected to wave and earthquake loadings. In this paper, steel jackets are modelled using geometric non-linear space frames and wave loadings re evaluated based on Morrison equation using the linear Airy theory and the fifth Stokes theory. Random wave is generated using JONSWAP spectrum. For earthquake analysis, dynamic analysis is performed using artificial earthquake time history. Also the plastic hinge method is presented for limit analysis of steel jacket. In the companion paper, the pre/post processor is developed and the numerical examples are presented for linear and non-linear dynamic analysis of steel jackets.

• Korean Chemical Engineering Research
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• v.47 no.3
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• pp.327-331
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• 2009

A thermally coupled distillation system is constructed using two columns used in a conventional two column system, and its operability is examined by investigating the dynamic behavior. For the control of three product specifications, the step response test is performed and a $3{\times}3$ control structure using flow rates of overhead and side products and vapor boilup is suggested. The performance of the proposed control system indicates that the specification control of bottom product is the most difficult but the operation of the proposed system is available.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.2
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• pp.1-9
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• 1985

Two methods for the dynamic analysis of fixed offshore structures subjected to random waves are studied. They are the frequency domain method using the equivalent linearization of the nonlinear drag force, and the time domain method utilizing the Monte Carlo simulation technique for time series of random wave particle velocities and accelerations. Example analyses are carried out for two structures with different structural characteristics and for various wave conditions. A comparison has been made between the results obtained by two methods.

• Journal of the Korean Society for Advanced Composite Structures
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• v.3 no.3
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• pp.38-46
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• 2012

The method based on various mathematical characteristic equations for identifying tensile forces in the cable structure system are used as response data to reflect the properties of the dynamic sensitivity. The vibration tests have been conducted with respect to levels of applied weight for the sagged cable. In this study, a set of natural frequencies are extracted from the measured dynamic data. Next, existing characteristic equation methods based these extracted natural frequencies are applied to identify tensil forces of the sagged cable system. Through several verification procedures, the proposed methods could be applied to a sagged cable system when the initial material data are insufficiency.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.17 no.3
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• pp.138-148
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• 2005

Dynamic response of floating structures such as floating body and floating bridges subject to wave load is to be calculated in frequency domain. Added mass coefficient, damping coefficient and wave exciting force are obtained numerically from frequency domain formulation of linear potential theory and boundary element method for a floating body which is partially submerged into water and subjected to wave force. Next, the equation of motion for the dynamic behavior of a floating structure which is supported by the floating bodies and modeled with finite elements is written in frequency domain. hker a hemisphere is analyzed and compared with the published references as examples of floating bodies, the hydrodynamic coefficients for a pontoon type floating body which supports a floating bridge are determined. The dynamic response of the floating bridge subject to design wave load can be solved using the coefficients obtained for the pontoons and the results are plotted in the frequency domain. It can be seen from the example analysis that although the peak frequency of the incoming wave spectrum is near the natural frequency of the bridge, the response of the bridge is not amplified due to the effect that the peak frequency of wave exciting force is away from the natural frequency of the bridge.

• Proceeding of KASS Symposium
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• 2008.05a
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• pp.139-144
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• 2008

Experimental studies using tuned liquid damper(TLD) and multiple tuned liquid damper(MTLD), which are passive control devices consisting of a rigid tank filed with liquid, are used to suppress vibration of structures. This TLD and MTLD are attributable to several potential advantage -low costs, easy; easy to install in existing structures: effective even for small amplitude vibrations. For this, we conducted shaking table experiments for two natural frequencies (0.44Hz, 0.55Hz) according to the excitation amplitude(1mm, 3mm, 5mm, 10mm, 20mm) So, the majority of studies suggested optimized natural frequence and excitation amplitude for control devices.(TLD and MTLD type : circle, rectangular) As the analysis result, we verified vibration reduction effects of a MTLD by analyzing the performance experiment of TLD and MTLD

• Journal of the Society of Naval Architects of Korea
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• v.47 no.2
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• pp.242-247
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• 2010

To consider effects of essential parameters of water impact pressure on dynamic structural responses of bow bottom structures, a parametric study for a ship bottom panel is carried out. The idealized pressure time history models were assumed by triangular and rectangular shapes in time domain. The main loading parameters are duration time and peak pressure value maintaining the same impulse value. The structural models for local bottom stiffened panels of a container ship are analysed. The natural frequency analysis and transient dynamic response analysis are performed using MSC/NASTRAN. Added mass effects of contacting water are considered and the pressure distributions are assumed to be uniform in the whole water contacting surface. The effects of loading parameters on the structural responses, especially maximum displacements, are considered. Besides the peak pressure value, effects of duration time correlated with natural frequencies are thought to be the important parameters.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.1
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• pp.116-125
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• 1995

Higher order nonlinear transfer functions are applied to model the nonlinear responses obtained Inn dynamic analysis of single degree of freedom systems (SDOF) subjected to wave and current loadings. The structural systems are subjected to single harmonic, two wave combination and irregular wave loading. Three different sources of nonlinearities are examined for each of the wave loading condition and it is shown that the nonlinear response appear at the resonance frequencies of the SDOF even when virtually no wave energy exists at those resonance frequencies. Higher order nonlinear transfer functions based on Volterra series representation are used to model the nonlinear responses mainly f3r the flexible systems and clearly shows the degrees of nonlinearity either as quadratic or cubic.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.5
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• pp.87-94
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• 2014

It becomes critical to understand an energy coupling mechanism between flow perturbations and combustion heat release rate fluctuations for the understanding of high-frequency combustion instabilities occurring in high-performance combustion/propulsion systems. A significant amount of experimental researches have been carried out to understand flame dynamic characteristics by use of flame transfer functions with artificial flow disturbances. Among them, there exist substantial studies on flame response by the excitation of inlet flow. Recently, experimental studies simulating transversal modes excited in actual combustion systems are under way.