SH Acoustic Waves in a Lithium Niobate Plate and the Effect of Electrical Boundary Conditions on Their Properties

2001 ◽  
Vol 47 (3) ◽  
pp. 282 ◽  
Author(s):  
S. G. Joshi
Keyword(s):  
Lithium Niobate ◽  
Boundary Conditions ◽  
Acoustic Waves ◽  
Electrical Boundary Conditions

Investigation of acoustic waves in thin plates of lithium niobate and lithium tantalate

2001 ◽  
Vol 48 (1) ◽  
pp. 322-328 ◽  
Author(s):  
I.E. Kuznetsova ◽  
B.D. Zaitsev ◽  
S.G. Joshi ◽  
I.A. Borodina
Keyword(s):  
Lithium Niobate ◽  
Acoustic Waves ◽  
Lithium Tantalate ◽  
Thin Plates

scholarly journals Atmospheric radiation boundary conditions for the Helmholtz equation

2018 ◽  
Vol 52 (3) ◽  
pp. 945-964 ◽  
Author(s):  
Hélène Barucq ◽  
Juliette Chabassier ◽  
Marc Duruflé ◽  
Laurent Gizon ◽  
Michael Leguèbe
Keyword(s):  
Boundary Conditions ◽  
Helmholtz Equation ◽  
Acoustic Waves ◽  
Numerical Study ◽  
Outgoing Wave ◽  
Atmospheric Radiation ◽  
Angle Of Incidence ◽  
Radiation Boundary Conditions ◽  
Radiation Boundary ◽  
Dirichlet To Neumann Map

This work offers some contributions to the numerical study of acoustic waves propagating in the Sun and its atmosphere. The main goal is to provide boundary conditions for outgoing waves in the solar atmosphere where it is assumed that the sound speed is constant and the density decays exponentially with radius. Outgoing waves are governed by a Dirichlet-to-Neumann map which is obtained from the factorization of the Helmholtz equation expressed in spherical coordinates. For the purpose of extending the outgoing wave equation to axisymmetric or 3D cases, different approximations are implemented by using the frequency and/or the angle of incidence as parameters of interest. This results in boundary conditions called atmospheric radiation boundary conditions (ARBC) which are tested in ideal and realistic configurations. These ARBCs deliver accurate results and reduce the computational burden by a factor of two in helioseismology applications.

Experimental Investigation of Thermoacoustic Instabilities for a Model Combustor With Varying Fuel Components

2011 ◽  
Author(s):  
X. Y. Zhang ◽  
H. Zhang ◽  
M. Zhu
Keyword(s):  
Boundary Conditions ◽  
Acoustic Waves ◽  
Thermal Power ◽  
Supply System ◽  
Dynamic Processes ◽  
Combustion Instabilities ◽  
Thermoacoustic Instabilities ◽  
Instability Modes ◽  
Syngas Combustion ◽  
Fuel Components

In this study, a combustion facility was constructed that includes a flexible fuel supply system to produce synthesis gas using a maximum of three components. The rig with lean premixed burner is able to operate at up to 5 bars. The length of the inlet plenum and the outlet boundary conditions of the combustion chamber are adjustable. Experiments were carried out under a broad range of conditions, with variations in fuel components including hydrogen, methane and carbon monoxide, equivalence ratios, thermal power and boundary conditions. The dynamic processes of self-excited combustion instabilities with variable fuel components were measured. The mechanisms of coupling between the system acoustic waves and unsteady heat release were investigated. The results show that instability modes and flame characteristics were significantly different with variations in fuel components. In addition, the results are expected to provide useful information for the design and operation of stable syngas combustion systems.

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