Recent railway vehicle carbodies are getting light-weight and structurally-simplified in terms of speed-up and energy saving. They often lead to increase the vertical flexural vibration of carbody which causes deterioration of the ride comfort. Therefore, it has been required to reduce the flexural vibration. An elastic body deforming both vertical and horizontal direction in response to a vertical input has possibility to be a simple but effective vibration absorber, according to previous studies. This paper proposes a new numerical model called "equivalent deformation model" which is able to represent the vibration of such elastic body. The validity of the model is verified through excitation tests for elastic circular cylindrical shells filled with water. And its vibration reduction effect is examined using 1:5 scale model of a Shinkansen. It is confirmed that the equivalent deformation model is applicable for designing an elastic circular cylindrical shell as a dynamic vibration absorber (elastic DVA). And the first-mode of bending vibration of the scale model can be successfully reduced by utilizing the elastic DVA.
Prediction of the low Mach number jet noise ejected from rectangular nozzle with high aspect ratio is described. Firstly measurement of the jet noise was conducted in semi-anechoic wind tunnel at the low Mach number flow condition. We were found that the sound power of the jet obeyed 6-th power of jet velocity. This means the jet noise is resulted not from quadrupole distribution in the shear flow of jet, but from dipole distribution on the surface of the exit of the nozzle. The model of vortex sound is applied as the sound generation mechanism at numerical simulation. The sound emission from the vortices in the shear flow is modified with the compact Green’s function representing the scattering effect from the surface of the exit of the nozzle in the lower frequency range. It is also modified with the non-compact Green’s function in the higher frequency range. Lastly calculated sound spectra are compared with measured spectra. The comparison will prove effectiveness of this modeling.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.