• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.10a
• /
• pp.562-562
• /
• 2014

Assessment of aerodynamic noise is becoming increasingly important for automotive manufacturers. Flow passing a vehicle may indeed lead to high interior noise level and affect cabin comfort. Interior noise results from various mechanisms including aerodynamic fluctuations of the disturbed flow around the side mirror or pillar, hydrodynamic and acoustic loading of the car panels and windows, vibration of these panels and acoustic radiation inside the vehicle. Objective of the present study is to capture these important mechanisms in a simulation model and demonstrate the ability of the combined simulation tools Fluent / Virtual.Lab to provide accurate aerodynamic and interior noise prediction results. Previous study focused on the noise generated by the turbulence around the A-pillar structure of the HSM (Hyundai simplified model). The present study also includes the effect of the side-mirror and rain-gutter structures. Complete modeling process is presented including details on the unsteady CFD simulation and the vibro-acoustic model with absorption materials. Guidelines and best practices for building the simulation model are also discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2011.04a
• /
• pp.308-314
• /
• 2011

The research which sees, the parameters inputs and acoustic measurement result in simulation error most on a large scale concreteness of 3D models which affect number of effective surface. Therefore DATA of above the comparison which will listen, analyzed and investigated.

• Proceedings of the Acoustical Society of Korea Conference
• /
• 1998.06c
• /
• pp.473-476
• /
• 1998

본 연구에서는 GAT(Geometry Acoustic Theory)를 이용한 표적신호 합성모델의 이론적 배경을 제시하고, 수치모델의 결과를 음향수조에서 축소표적 실험자료 결과와 비교한다. GAT에 의한 표적신호 합성모델은 3차원 해양환경에서 음원과 표적에 의한 음장을 적절히 묘사할 뿐만 아니라 표적 형상에 의한 효과를 정밀하게 계산함으로써 고 정밀도의 표적신호 합성을 가능하게 한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.05a
• /
• pp.843-846
• /
• 2004

Cavity tone is generated due to the feedback between flow and acoustic wave. It is recognized that the period is determined by the time required for the flow convection in one direction, the time required for the acoustic propagation in the other direction and the time for phase shift depending on the flows and mode. Most of the phenomena have been investigated by experiments and a simple but fundamental theory. But the cause of the phase shift and the correctness of the theory have not been clearly explained so far. In this paper, the phenomena are calculated numerically to obtain detail information of flow and acoustic wave to explain the mechanism including the phase. High order high resolution scheme of optimized high order compact is used to resolve the small acoustic quantities and large flow quantities at the same time. The data are reduced using cross correlation function in space and time and cross spectral density function which has phase information. Abrupt change in pressure near corner in cavity is observed and is relate to phase variation. The time required for the feedback between the flow and acoustic wave is calculated after the numerical simulation f3r various modes. The periods based on the time calculated using the above method and direct observation from the acoustic waves generated and propagated in the numerical simulation are compared. It is found that no phase shift is required if we examine the time required carefully. Rossiter's formula for the cavity tone used for quick estimation needs to be modified far some modes.

• Proceeding of Spring/Autumn Annual Conference of KHA
• /
• 2004.11a
• /
• pp.349-354
• /
• 2004

In accordance with recent culture-advancement and national improvement in conscious level, the desire for cultural life is on increasing, so that it is also increasing tendency toward the planning and construction of large performance hall for the local residents, conducted by the provincial self-governing body. For the sake of a satisfiable acoustic efficiency at the said large performance hall, although it is designed and constructed with application of various methods of simulation from the planning stage, there could be appeared an error of the said simulation and defect occurred in the construction, and due to such reason, a situation unable to fulfill a satisfiable Acoustic efficiency to be generated thereat after opening of the hall. Accordingly, it is able to judge on the part which necessitates for betterment, also the region where acoustically weak, through measurement and evaluation on the acoustic efficiency in the completed performance all, and by its correction as well as supplement thereon based on the afore-mentioned, a performance hall equipped with the supreme acoustic condition could be established.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.132-136
• /
• 2007

In case of indoor gymnastics training floor, in view of its characteristics, since it is simultaneously required the related smooth communication between the coach and the player, also the acoustic performance regarding to the Clearness of Music, besides the sport activity, the consideration about the acoustic character has entered the stage as an indispensable element. On such viewpoint, on the object of the recently built dome-typed gymnastics training floor, after making the optimized acoustic design with the remodeling through acoustic simulation, by means of measurement and valuation on human's psychological(sensual) degree utilizing Auralization that enables to experience the virtual sound field at the stage of design, this thesis has attempted to survey of the acoustic satisfaction degree and its reaction about the gymnastics training floor. As the result of investigation about the research on the space of object, it could be known that the valuation regarding to the acoustic performance of 'After-Improvement' was distinctly more refined than that of 'Before-Improvement'. It is now considering that such result of the study can be utilized as the useful data which enables to improve the retrenchment effect of the construction cost as well as the acoustic capability, by means of the prediction control on the acoustic problem from the stage of design, for the occasion when the similar indoor sport gymnasium is planning to build for the near future.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1996.04a
• /
• pp.41-46
• /
• 1996

The engine intake system noise has been recognized as a problem for many years. Acoustic design of intake system has traditionally been a trial and error process. This has resulted in the development of computer simulation program for a acoustic analysis and acoustic modeling. In this study, we developed the program based on the transfer matrix method which analyze and predict the performance of a intake noise. The program was verified by experiments on a real intake system. By using of the simulation program, we analyzed acoustic characteristics and, made proposals of improvement to reduce the intake noise and was verified by the SYSNOISE software.

• The KSFM Journal of Fluid Machinery
• /
• v.13 no.3
• /
• pp.5-11
• /
• 2010

As a basic study of the aero-acoustic noise, Large eddy simulations were carried out for a fixed circular cylinder at Renolds number (Re=$9.0\times10^4$) using commercial CFD code, FLUENT. The subgrid-scale turbulent viscosity was modeled by Smagorinsky-Lilly model adapted to structured meshes. The results of analysis showed that time-averaged value, $\bar{C}_D$ is approximately 1.47 which is considerably adjacent with the experimentally measured value of 1.32 in comparison to the values performed by previous researchers. It is observed that there are the very small acoustic pressure fluctuation with the same frequency of the Karman vortex street.

• Journal of Mechanical Science and Technology
• /
• v.18 no.10
• /
• pp.1738-1746
• /
• 2004

When there are low signal to noise relationships or low coherences between measured pressure and a reference sensor, a pressure field measured and estimated by NAH (Nearfield Acoustic Holography) becomes noisy on the hologram and source planes. This paper proposes a method to obtain the high coherent de-noised pressure signals from low coherent noisy ones by combining a wavelet algorithm with NAH. The proposed method obtains the de-noised field from acoustic fields on a noise source plane reconstructed through backward propagation of NAH. Thus this method does not need high coherent pressure signals on the hologram surface while the conventional nearfield acoustic holography requires high-coherent signals. The proposed method was verified by numerical simulation using noisy signals, composed of original signals and imposed noises distributed on the hologram surface.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.248-252
• /
• 2007

As Waterpower Generation generates electricity using the difference of altitude of water, also let the turbine revolves through water pipe, at this time the revolving turbine causes exceedingly huge noise. Accordingly, not only those workers in the hydraulic turbine dynamo room are suffering the difficulties in mutual communication, but also those workers in the adjacent office are enduring the obstruction to the business due to the noise. Therefore, this Study has analyzed the reduction effect on the noise of hydraulic turbine dynamo room utilizing computer simulation, through the preceding research with the optimized model for architectural acoustic factor of the hydraulic turbine dynamo room. It is considered that such research result could be applied as the useful material for improvement of acoustic performance and noise-reduction effect at other similar hydraulic turbine dynamo room in the future.