• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.282-287
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• 2004

Noise and vibrations in the pipe systems may be arisen from pumps. compressors, etc. The source mechanism is classified with the mechanical and hydraulic. Mechanical vibrations may be excited by the unbalance in rotating machinery. Hydraulic source may be generated in the turbulent flow. The vibro-acoustic behaviour of flexible, fluid-filled pipe system is a very complex and determined by two parameters: the frequency and the mass ratio of fluid and pipe wall. As the frequency increases, the mode number in the pipe increases. The mass ratio is close to one, the structure and the fluid are strongly coupled. In ease the diameter is very small to the length of pipe, the behaviour of pipe is same as a beam. The finite element formulation when the fluid and the structure are coupled is derived by using beam element. The Numerical results are compared with the package (Sysnoise) which is using the shell element.

• 동력기계공학회지
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• 제6권3호
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• pp.57-63
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• 2002

This paper describes the acoustic analysis of mid duty truck. The focus of the analysis is on structure borne engine noise with major contributions of 2nd order. It has been previously recognized that the noise contribution of each transfer path of structure borne noise can be varied with the charateristics of each mounts and vibro acoustic sensitivity of car body. The structure of car body will be split up into three major sub components, which are modeled separately, the engine, the frame and the cab. The acoustic performance is evaluated on three levels: engine to frame transfer, frame to cab transfer, and panel contribution from cab to driver. In order to perform these analyses, analytical models are created for the engine, frame, cab and acoustic cavity. The models are linked through a coupled fluid structure calculation, and through FRF Based Substructuring for the structural couplings. Based on the structural coupling calculations, a transfer path analysis is performed to identify the most important transfer paths. These paths are then the focussing points for applying modifications to the structure or the mount system. Finally, a number of modification are proposed and their effect is quantified.

• 한국음향학회지
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• 제39권4호
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• pp.351-363
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• 2020

발사체는 비행 중 공기역학적 현상에 기인하는 음향하중의 영향을 받는데, 특별히 천음속 영역에서 그 영향이 증가된다. 음향하중으로 인한 페어링 내부 소음진동은 탑재물의 오작동을 유발할 수 있어 이를 예측하고 저감하는 과정이 필수적이다. 본 연구에서는 발사체 외부에 작용하는 공기역학적 음향하중에 의한 페어링 내부 음향 진동환경을 예측하고, 음향 블랭킷과 헬름홀츠 공명기를 이용하여 소음저감 설계를 구현하는 프로세스를 개발하였다. 음향하중 예측은 Reynolds-Averaged Navier-Stokes(RANS) 유동해석 결과와 난류 경계층 내부 압력섭동에 관한 준 경험식을 이용하였고, 음향진동 연성해석은 ANSYS APDL과 VA One SEA의 Finite Element Statistical Energy Analysis(FE-SEA) 하이브리드 해법을 이용하였다. 개발된 절차를 천음속 해머 헤드형 발사체에 적용하여 음향하중 저감효과를 확인하고 개발된 절차의 유효성을 검증하였다. 본 연구에서 개발된 절차는 타당한 수준의 정확도로 신속한 결과를 얻을 수 있어 발사체 초기설계 단계에 유용하게 쓰일 수 있을 것으로 예상된다.