Acoustic propagation modeling for marine hydrokinetic applications

Abstract

The combination of riverine, tidal, and wave energy have the potential to supply over one third of the United States' annual electricity demand [1]. However, in order to deploy and test prototypes and commercial installations, marine hydrokinetic (MHK) devices must meet strict regulatory guidelines. These regulations mandate the maximum amount of noise that can be generated and sets particular thresholds for determining disturbance and injury caused by noise. In the absence of measured levels from in-situ deployments, a model for predicting the propagation of a MHK source in a real hydroacoustic environment needs to be established. An accurate model for predicting the propagation of a MHK source(s) in a real-life hydro-acoustic environment has been established. This model will help promote the growth and viability of marine, water, and hydrokinetic energy by confidently assuring federal regulations are meet and harmful impacts to marine fish and wildlife are minimal. A 3D finite-difference solution to the governing velocity-pressure equations is presented and offers advantages over other acoustic propagation techniques for MHK applications as spatially varying sound speeds, bathymetry, and bed composition that form complex 3D interactions can be modeled. This solution method also allows for the inclusion of complex MHK sound spectra from turbines and/or arrays of turbines. A number of different cases for hydro-acoustic environments have been validated by both analytical and numerical results from canonical and benchmark problems. Several of these key validation cases are presented in order to show the applicability and viability of a finite difference numerical implementation code for predicting acoustic propagation in a hydro environment. With the model successfully validated for hydro-acoustic environments, more complex and realistic MHK sources from turbines and/or arrays can be modeled. A systematic investigation of MHK relevant scenarios is presented with increasing complexity including a single- and multi- source investigation, a random phase change study, and a hydro-acoustic model integration