Numerical Hydroacoustic Analysis of NACA Foils in Marine Applications and Comparison of Their Acoustic Behavior

One of the most important parameters to be considered in the design process of lifting surfaces for marine applications is the acoustic noise emitted by the designed surface. In the present work, the hydroacoustic fields of NACA0012 and NACA0018 hydrofoils are calculated, and the acoustic behavior of these sections is examined and compared at different angles of attack. The Ansys-CFX Navier-Stokes solver is used for hydrodynamic analysis, and a highly accurate multithread program named ACOPY is developed in Python programming language based on the Ffowcs Williams and Hawkings method for acoustic analysis. The developed code has high capability in parallel programming. Results of hydrodynamic and acoustic analyses have been validated against available data. A parametric study is conducted, and the best integration surface for FW-H method is introduced. The acoustic behavior of the sections is calculated in an extensive parametric study for different angles of attack of the hydrofoils. The operational acoustic fields of the foils have been calculated and compared. The results indicate that NACA0012 hydrofoil is a better choice and, more effective, when the acoustic behavior of the hydrofoil is a significant design criterion. 1. Introduction The prediction and calculation of the noise generated from airfoils have been an extensive aero-acoustic research topic in the last half century, both experimentally and numerically. The numerous efforts in this area have been mostly motivated by the desire to understand the nature and the origins of airfoil noise and to find effective applicable methods to minimize it. However, although lifting surfaces are widely used in marine applications and despite the importance of acoustic noise in marine environments, the noise generation of hydrofoils has been barely considered in acoustic publications. The primordial motivation of the present work is to numerically predict and compare the acoustic behavior of two foil sections, that is, NACA0012 and NACA0018, in marine environment. Generally, there are two principal ways to numerically calculate sound propagation in a fluid: solving the Navier-Stokes equations and solving the wave equation. Therefore, the literature is bounded by these two categories. In the first method, the Navier-Stokes equations are solved for the entire domain in which the observer and the source are included. This method is numerically very expensive for large domains, but all nonlinear phenomena are considered and can be captured [1–9]. Shen et al. [7] in 2004 solved the Navier-Stokes equations for a