• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.9 s.114
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• pp.937-948
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• 2006

In this study, a fluid/structure coupled analysis system for simulating complex flow-induced vibration (FIV) phenomenon of cascades has been developed. The flow is modeled using Euler and Wavier-Stokes equations with different turbulent models. The fluid domains are modeled using the unstructured grid system with dynamic deformations due to the motion of structural boundary. The Spalart-Allmaras (S-A) and the SST ${\kappa}-{\omega}$ turbulent models are used to predict the transonic turbulent flows. A fully implicit time marching scheme based on the Newmark direct integration method is used in order to solve the coupled governing equations for viscous flow-induced vibration phenomena. For the purpose of validation for the developed FIV analysis system, comparison results for computational analyses of steady and unsteady aerodynamics and flutter analyses are presented in the transonic flow region. In addition, flow-induced vibration analyses for the isolated cascade and multi-blades cascade models have been conducted to show the physical fluid-structure interaction effects in the time domain.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.793-802
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• 2006

In this study, a fluid/structure coupled analysis system for simulating complex flow-induced vibration (FIV) phenomenon of cascades has been developed. The flow is modeled using Euler and Wavier-Stokes equations with different turbulent models. The fluid domains are modeled using the unstructured grid system with dynamic deformations due to the motion of structural boundary. The Spalart-Allmaras (S-A) and the SST ${\kappa}-{\omega}$ turbulent models are used to predict the transonic turbulent flows. A fully implicit time marching scheme based on the Newmark direct integration method is used in order to solve the coupled governing equations for viscous flow-induced vibration phenomena. For the purpose of validation for the developed FIV analysis system, comparison results for computational analyses of steady and unsteady aerodynamics and flutter analyses are presented in the transonic flow region. In addition, flow-induced vibration analyses for the isolated cascade and multi-blades cascade models have been conducted to show the physical fluid-structure interaction effects in the time domain.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.281-286
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• 2007

Needs of fuel's performance evaluation for the dual-cooled fuel pellet (annular shape) necessitate the irradiation test in the test reactor. Irradiation test rig for the HARARO reactor, which is a special-purposed equipment used for material, irradiation and creep test, must satisfy the operational requirement on the hydraulic characteristics and structural integrity. In this paper, pressure drop and flow-induced vibration test for the newly developed non-instrumented test rig were carried out using FIVPET as a out-pile evaluation test. The test results show that the new test rig satisfy the HANARO operational requirement with sufficient margin. The spectral response characteristics of the flow-induced vibration of the test rid were also discussed.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.1
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• pp.82-93
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• 2008

The flowfield behind two cylinders and flow-induced noise generated from the cylinders in various arrangement are numerically investigated based on the finite difference lattice Boltzmann model with 21 velocity bits. which is introduced a flexible specific heat ${\gamma}$ to simulate diatomic gases like air. In an isolated cylinder with two type of mesh. some flow parameters such as Strouhal number $S_t$ and acoustic pressure ${\Delta}p$ simulated from the solution are given and quantitatively compared with those provided the previous works. The effects of the center-to-center pitch ratio $L_{cc}/d=2.0$ in staggered circular cylinders as shown in Fig. 1 and angles of incidence ${\alpha}=30^{\circ}(T_{cc}/d=0.5)$, $45^{\circ}(T_{cc}/d =0.707)$ and $60^{\circ}\;(T_{cc}/d=0.866)$, respectively, are studied. Our analysis focuses on the small-scale instabilities of vortex shedding, which occurs in staggered arrangement. With the results of drag $C_d$ and lift $C_l$ coefficients and vorticity contours. the mechanisms of the interference phenomenon and its interaction with the two-dimensional vortical structures are present in the flowfields under $Re\;{\le}\;200$. The results show that we successively capture very small pressure fluctuations, with the same frequency of vortex shedding, much smaller than the whole pressure fluctuation around pairs of circular cylinders. The upstream cylinder behaves like an isolated single cylinder, while the downstream one experiences wake-induced flutter. It is expected that, therefore, the relative position of the downstream cylinder has significant effects on the flow-induce noise, hydrodynamic force and vortex shedding characteristics of the cylinders.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.250-253
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• 2006

The in-pile Section (IPS) is subjected to flow-induced vibration(FIV) due to the flow of the primary coolant and then the structural integrity. The in-pile Section (IPS) of 3-pin Fuel Test Loop(FTL) shall be installed in the vortical hole call IR1 of HANARO reactor core. In order to verify the velocity and displacement both the inside region of IPS at the annular region of IPS, the vibration was measured by varing the flow rate on both regions. The displacements of fuel assembly in the in-pile Section (IPS) were found to be lower than the values of allowable design criteria.

• The KSFM Journal of Fluid Machinery
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• v.3 no.3 s.8
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• pp.31-40
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• 2000

A computer program is developed for the prediction of the aerodynamic performance and the noise characteristics in the basic design step of axial flow fan. The flow field and the performance of fan are analyzed by using the streamline curvature computing scheme with total pressure loss and flow deviation models. Fan noise is assumed to be generated due to the pressure fluctuations induced by wake vortices of fan blades and to radiate via dipole distribution. The vortex-induced fluctuating pressure on blade surface is calculated by combining thin airfoil theory and the predicted flow field data. The predicted performances, sound pressure level and noise directivity patterns of fan by the present method are favorably compared with the test data of actual fan. Furthermore, the present method is shown to be very useful in optimizing design variables of fan with high efficiency and low noise level.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.11
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• pp.4129-4136
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• 2010

This paper addresses how to reduce or redesign uncomfortable sound from small refrigerator by modifying some structures in mechanical components or operating conditions. After performing vibration analysis on each component and then sound analysis are carried out. From stepped designed experiments, we could acquire some important results that structure and flow induced vibration assumed to be a major cause to noise level and frequencies. Modifying some mechanical structure and operating conditions, uncomfortable starting noise and beating sound are suppressed. Machinery room located in refrigerator's backside is investigated for vibration and noise suppression, and some ideas for more improvement are suggested.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.502-507
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• 2000

This paper presents the numerical prediction of airflow-induced sound in DVD drives. Computational fluid dynamics (CFD) is first conducted to evaluate flow field characteristics due to the high-speed disk rotation, and to support the acoustic analysis. The acoustic analogy based on Ffowcs Williams-Hawkings (FW-H) equation is adopted to predict aeroacoustic noise patterns. The integral solution for quadrupole volume source is included to identify the turbulence noise generated inside the DVD tray. Near-field noise is strongly affected by the flow field characteristic, which is caused by the complex shape of the tray. For a mid-field, the quadrupole noise play as a counterpart of thickness noise or loading noise, resulting in a different pattern compared with those in the near field.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.2166-2168
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• 2001

Reactor Noise is defined as the fluctuations of measured instrumentation signals during full-power operation of reactor which have informations on reactor system dynamics such as neutron kinetics. The Reactor internal structures which consist of many complex components are subjected to flow-induced vibration due to high temperature and pressure in reactor coolant system. The above flow-induced vibration causes degradation of structural integrity of the reactor and may result in loosing mechanical binding component which might impact other equipment and component or cause flow blockage. It is important to analyze reactor noise signal for the early detection of potential problem or failure in order to diagnosis reactor integrity in the point of view of safety and plant economics. Detailed design of hardware diagnostic system reactor internal structures using neutron noise(RIDS).

• Advances in aircraft and spacecraft science
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• v.3 no.3
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• pp.259-269
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• 2016

In this work results from an underwater experiment on flow-induced noise in the interior of a towed body generated from a surrounding turbulent boundary layer are presented. The measurements were performed with a towed body under open sea conditions at towing depths below 100 m and towing speeds ranging from 2.4 m/s to 6.2 m/s (4 kn to 12 kn). Focus is given in the experiments to the relation between (outer) wall pressure fluctuations and the (inner) hydroacoustic near-field on the reverse side of a flat plate. The plate configuration consists of a sandwich structure with an (thick) outer polyurethane layer supported by an inner thin layer from fibre-reinforced plastics. Parameters of the turbulent boundary layer are estimated in order to analyse scaling relations of wall-pressure fluctuations, interior hydroacoustic noise, and the reduction of pressure fluctuations through the plate.