Evaluation of Methods for Characterizing the Air/Water Interface for Parabolic Equation Transmission Loss Modeling

摘要

Proper characterization of underwater acoustic transmission loss (TL) relies on proper treatment of the air/water and water/sediment interfaces. This paper will focus on how the air/water interface is treated in parabolic equation (PE) models such as the range dependent acoustic model (RAM) Collins, M. D., 'Applications and time-domain solution of higher-order parabolic equations in underwater acoustics,' J. Acoust. Soc. Am., 86 (3), 1097-1102, 1989 and the finite element parabolic equation (FEPE) model Collins, M.D., 'A higher-order parabolic equation for wave propagation in an ocean overlying an elastic bottom', J. Acoust. Soc. Am. 86, 1459-1464, 1989. Two surface loss methods have been implemented in RAM, a surface loss versus angle (LVA) and a conformal mapping (CM) method. Additionally, the CM method has been implemented in FEPE. These two methods are discussed and compared for realistic test cases and a third option, which has accuracy consistent with the CM but speed more aligned with the LVA approach is discussed.