Modeling nonlinear acoustic waves in media with inhomogeneities in the coefficient of nonlinearity.

2010 ◽  
Vol 127 (3) ◽  
pp. 1866-1866
Author(s):  
L. Demi ◽  
M. D. Verweij ◽  
K. W. A. van Dongen
Keyword(s):  
Acoustic Waves ◽  
Nonlinear Acoustic

Propagation of nonlinear acoustic waves in bimodular media with linear dissipation

Wave Motion ◽  
2013 ◽  
Vol 50 (2) ◽  
pp. 191-196 ◽  
Author(s):  
A. Radostin ◽  
V. Nazarov ◽  
S. Kiyashko
Keyword(s):  
Acoustic Waves ◽  
Nonlinear Acoustic ◽  
Bimodular Media

Amplification of energy flux of nonlinear acoustic waves in a gas-filled tube under an axial temperature gradient

2002 ◽  
Vol 456 ◽  
pp. 377-409 ◽  
Author(s):  
N. SUGIMOTO ◽  
K. TSUJIMOTO
Keyword(s):  
Boundary Layer ◽  
Temperature Gradient ◽  
Energy Flux ◽  
Acoustic Waves ◽  
Wave Equations ◽  
Main Flow ◽  
Nonlinear Wave Equations ◽  
Axial Temperature Gradient ◽  
Axial Temperature ◽  
Nonlinear Acoustic

This paper considers nonlinear acoustic waves propagating unidirectionally in a gas-filled tube under an axial temperature gradient, and examines whether the energy flux of the waves can be amplified by thermoacoustic effects. An array of Helmholtz resonators is connected to the tube axially to avoid shock formation which would otherwise give rise to nonlinear damping of the energy flux. The amplification is expected to be caused by action of the boundary layer doing reverse work, in the presence of the temperature gradient, on the acoustic main flow outside the boundary layer. By the linear theory, the velocity at the edge of the boundary layer is given in terms of the fractional derivatives of the axial velocity of the gas in the acoustic main flow. It is clearly seen how the temperature gradient controls the velocity at the edge. The velocity is almost in phase with the heat flux into the boundary layer from the wall. With effects of both the boundary layer and the array of resonators taken into account, nonlinear wave equations for unidirectional propagation in the tube are derived. Assuming a constant temperature gradient along the tube, the evolution of compression pulses is solved numerically by imposing the initial profiles of both an acoustic solitary wave and of a square pulse. It is revealed that when a positive gradient is imposed, the excess pressure decreases while the particle velocity increases and that the total energy flux can indeed be amplified if the gradient is suitable.

Finite-difference time-domain scheme for nonlinear acoustic waves in solids

2019 ◽  
Vol 130 ◽  
pp. 790-799 ◽  
Author(s):  
Xiaoyu Wang ◽  
Xun Gong ◽  
Chuanxi Qin ◽  
De Zhang ◽  
Haodong Wu ◽  
...  
Keyword(s):  
Finite Difference ◽  
Time Domain ◽  
Acoustic Waves ◽  
Finite Difference Time Domain ◽  
Nonlinear Acoustic ◽  
Difference Time

Nonlinear Ultrasonic Techniques for Testing Micro-Defects in Metal Matrix Composite Structure

2011 ◽  
Vol 483 ◽  
pp. 784-788
Author(s):  
Yi Dun ◽  
Shuan Jie Wang ◽  
Xiao Hong Shi ◽  
Zhao Ying Zhou
Keyword(s):  
Metal Matrix Composite ◽  
Matrix Composite ◽  
Composite Structure ◽  
Acoustic Waves ◽  
Metal Matrix ◽  
Amplitude Ratio ◽  
Second Harmonic ◽  
Harmonic Amplitude ◽  
Acoustic Features ◽  
Nonlinear Acoustic

Micro-defects inside metal matrix composite structure seriously influence the mechanic properties of materials and can undermine machine operations. In order to detect the micro-defects, we can make use of one of the nonlinear acoustic features, i.e., harmonics, which usually appear together with ultrasound when propagating through a damaged material. Based on the relationship between the harmonics, a method of using nonlinear acoustic harmonic amplitude ratio to distinguish micro-defects in metal matrix composite structure is discussed. The test results show that acoustic features, such as second harmonic excitation efficiency were very obvious for the damaged group samples. The method presented is effective in detecting the micro-defects, which means that nonlinear acoustic waves may provide us a good solution for quantitative evaluation of the early damages in metal matrix composite structure.

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