Diffraction of Plane Acoustic Pulses by Obstacles of Arbitrary Cross Section with an Impedance Boundary Condition

1968 ◽  
Vol 44 (4) ◽  
pp. 1062-1068 ◽  
Author(s):  
Richard P. Shaw
Keyword(s):  
Boundary Condition ◽  
Cross Section ◽  
Arbitrary Cross Section ◽  
Impedance Boundary Condition ◽  
Impedance Boundary

Axial backscattering from an absorbing finite cone

1970 ◽  
Vol 48 (9) ◽  
pp. 1098-1099
Author(s):  
John J. Bowman
Keyword(s):  
Boundary Condition ◽  
Cross Section ◽  
High Frequency ◽  
Diffraction Theory ◽  
Impedance Boundary Condition ◽  
Impedance Boundary ◽  
Backscattering Cross Section ◽  
Leading Term

The high-frequency, backscattering cross section for axial incidence on a highly absorbing, flat-based cone is obtained. The cone is assumed to obey an impedance boundary condition. The tip contribution is neglected, while the leading term in the base contribution is derived by means of wedge diffraction theory where the wedge has arbitrary face impedances. Surprisingly, the result is relatively simple.

A METHOD FOR THE TREATMENT OF A SLOPING SEA BOTTOM IN THE PARABOLIC APPROXIMATION

1996 ◽  
Vol 04 (01) ◽  
pp. 89-100 ◽  
Author(s):  
J. S. PAPADAKIS ◽  
B. PELLONI
Keyword(s):  
Boundary Condition ◽  
Helmholtz Equation ◽  
Pressure Field ◽  
Impedance Boundary Condition ◽  
Parabolic Approximation ◽  
Impedance Boundary ◽  
Local Boundary ◽  
Sea Bottom ◽  
Local Boundary Condition ◽  
Non Local

The impedance boundary condition for the parabolic approximation is derived in the case of a sea bottom profile sloping at a constant angle, as a non-local boundary condition imposed exactly at the interface. This condition is integrated into the IFD code for the numerical computation of the pressure field and implemented to test its accuracy in some benchmark cases, for which the backscattered field is negligible. It is shown that by avoiding the sloping interface, the results obtained are closer to the benchmark results given by normal mode codes solving the full Helmholtz equation, such as the 2-way COUPLE code, than those of the standard IFD or other 1-way codes, at least for problems that do not have significant backscattering effects.

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