RESEARCH PAPER Effect of Rake and Skew on the Hydrodynamic Characteristics and Noise Level of the Marine Propeller Mohsen Gorji 1 • Hassan Ghassemi 2 • Jalal Mohamadi 1 Received: 18 January 2016 / Accepted: 24 August 2017 Ó Shiraz University 2017 Abstract The research performed in this paper is con- ducted to predict the hydro-acoustics of the ship propeller by Reynolds-averaged Navier–Stokes solver in various skew and rake angles. Those angles may cause changes in pressure fluctuations and have effect on the propeller noise level. The two-step Ffowcs Williams and Hawkings equations are used to calculate hydrodynamic pressure and its performance as well as sound pressure level (SPL) at various points around the propeller. Comparison of the numerical results shows good agreement with the previous works. Based on these results, propellers skew and rake angles have effect on the noise sources. Many results for the pressure distribution, hydrodynamic performance and SPL at different rake and skew angles are presented and discussed. Keywords Skew and rake angles  Pressure distribution  Sound pressure level  Hydrodynamic performance 1 Introduction Various factors including environmental and structural factors play an important role in the generation of under- water noise. Ship’s propeller creates noise from its work behind the ship to make the thrust overcome the resistance at designed speed. Noise generated by the propellers in terms of intensity and spectrum has been a strategic issue for warships and military designers over the years. The generated sound can be heard for hundreds of meters below the surface and may be detected by sonar. In the design process, for marine propellers specifically to reach lowest noise possible (Carlton 2013). Conventional procedures to study the propeller unsteady force are the lifting surface and the panel methods. Kerwin and Lee (1978) applied the unsteady vortex lattice technique to formulate the unsteady propeller. Hoshino (1993) employed the panel method to simulate unsteady flow on propeller. These methods do not account for viscous effects, such as the boundary layer and separation flow and usually repair results with empirical treatments. To overcome the deficiency of potential methods, RANS model has been successfully employed for marine propellers. Funeno (2002) studied unsteady flow around a high-skewed propeller in non-uniform inflow. Hu et al. (2009) applied RANS model to simulate the test case, DTMB 4119, the propeller worked on non-uniform inflow conditions. Li and Yang (2009) investigated numerical prediction of flow around a propeller. Numerical simula- tion of tonal and broadband hydrodynamic noises of non- cavitating underwater propeller was carried out by Kher- admand et al. (2014). The FW-H model was used to find spectral distributions of flow noise for different advance coefficients. Seol et al. (2005) presented a numerical study on the non-cavitating and blade sheet cavitation noises of the underwater propeller. The noise is predicted using time- domain acoustic analogy and Ffowcs Williams–Hawkings formulation for far-field acoustics, while the flow field is analyzed with potential-based panel method. Park et al. (2009) numerically analyzed the tip vortex cavitation behavior and sound generation. In their work, they used hybrid method which integrates RANS solver and dissi- pation vortex model for flow field. Seol et al. (2002) used & Hassan Ghassemi gasemi@aut.ac.ir 1 Department of Marine Engineering, Malekashtar University of Technology, Shahinshahr, Iran 2 Department of Maritime Engineering, Amirkabir University of Technology, Tehran, Iran 123 Iran J Sci Technol Trans Mech Eng DOI 10.1007/s40997-017-0108-y