M. Usai, S. Carcangiu, G. Concu
Department of Electrical and Electronic Engineering, University of Cagliari, Cagliari, Italy
Department of Civil Engineering, Environmental and Architecture, University of Cagliari, Cagliari, Italy
In the field of assessment methodologies, particular importance is given to Non-Destructive Testing Techniques, which aspire to achieve the highest number of information about materials and structures without altering their condition. Ultrasonic Testing exploits the transmission and reflection characteristics of mechanical waves with appropriate frequencies passing through the investigated item. ...
R. Costley, H. Diaz-Alvarez, M. McKenna, A. Miller
U.S. Army Engineer Research and Development Center, Vicksburg, MS, USA
Two finite element models have been developed to investigate the acoustic radiation from a Pratt truss train bridge. The first model was a time dependent structural model that determined the vibration response of the structure due to two wheels, representing a single axle, moving across the bridge at constant speed. This model was expanded to include multiple axles to represent a locomotive. The ...
G. Campa and S.M. Camporeale
DIMEG, Politecnico di Bari, Bari, Italy
Modern gas turbines suffer of the phenomenon of combustion instability, also known as “humming”. The main origin of the instability is considered to be related to the interaction between acoustic waves and fluctuations of the heat released by the flame. This paper presents a novel numerical method in which the governing equations of the acoustic waves are coupled with a flame heat ...
S. Ni, C. Yang Koh, S. Kooi, and E. Thomas
Institute for Soldier Nanotechnologies
Dept. of Materials Science and Eng.
Recently, the concepts of fractal geometry have been introduced into electromagnetic and plasmonic metamaterials. With their self-similarity, structures based on fractal geometry should exhibit multi-band character with high Q factors due to the scaling law. However, there exist few studies of phononic metamaterials having fractal geometry. COMSOL is used to investigate vector elastic and ...
Empirical Model Dedicated to the Sensitivity Study of Acoustic Hydrogen Gas Sensors Using COMSOL Multiphysics®
A. Ndieguene, I. Kerroum, F. Domingue, A. Reinhardt
Laboratoire des Microsystèmes et de Télécommunications/Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada
Laboratoire d’Électronique et des Technologies de l’Information, CEA, LETI Grenoble, France
Due to the increasing demand for hydrogen gas sensors for applications such as automation, transportation, or environmental monitoring, the need for sensitive and reliable sensors with a short response time is increasing. This paper presents an empirical model that studies the sensitivity of acoustic hydrogen gas sensors. A parametric study based on the variation of physical properties of ...
Glass Plates Noise Transmission Suppression by Means of Distributed Piezoelectric Composite Actuators Shunted by an Active Circuit
K. Novakova, P. Mokry
Research Centre for Special Optics and Optoelectronic Systems (TOPTEC), Institute of Plasma Physics, Academy of Sciences of the Czech Republic, Turnov, Czech Republic
Institute of Mechatronics and Computer Engineering, Technical University of Liberec, Liberec, Czech Republic
Glass windows represent a virtual sound source for buildings interior. It is very easy to make them vibrate by action of incident acoustic pressure wave. Therefore, non-negligible part of the wave is transmitted through the window. We propose and simulate a method based on the change of mechanical properties of the plate using flexible piezoelectric Macro Fiber Composite actuators distributed on ...
K. Koppenhoefer, S.Yushanov, and M.H. McKenna
AltaSim Technologies, LLC, Columbus, Ohio, USA
U.S. Army Engineering Research and Development Center
Aging infrastructure requires frequent inspections to assess their structural integrity. However, the large amount of existing infrastructure, and the distance between these structures present significant challenges to inspectors. Acoustics-based technologies represent a simple, and relatively inexpensive, technique to monitor the integrity of a structure. To develop these techniques, designers ...
Alcon Research Ltd., Lake Forest, CA, USA
Anomalous acoustic streaming is observed from sharp edges of vibrating solid bodies in fluids. The streaming velocities can be orders of magnitude higher than expected from the Rayleigh streaming at similar amplitudes of vibrations. Acoustic velocity of a fluid relative to a solid body diverges at a sharp edge giving rise to a localized time-independent body force acting on the fluid. The ...
Poznan University of Technology, Poland
This paper examines a sound propagation without airflow through circular ducts with spiral element inside. Models are numerically computed in three-dimensions. The spiral element in the duct is a newly analyzed acoustical element, geometrically similar to the well-known Archimedes screw. It can be applied significantly in ducted systems, such as ventilation, air-conditioning and heat ...
On The Use of a Diffusion Equation Model for Sound Energy Flow Prediction in Acoustically Coupled Spaces
Y. Jing, and N. Xiang
Rensselaer Polytechnic Institute, Troy, NY, USA
This paper studies sound energy flows through an aperture across two coupled spaces using a diffusion equation model. The so-called double sloped sound energy decay is believed to be caused by the sound energy exchange through the aperture coupling the two rooms. The room diffusion equation is first solved by COMSOL, then the time dependent energy flow is visualized via COMSOL arrow plotting, ...