# CFD Design Performance Analysis for a High-Speed Propeller
## 1 Introduction  
Turbulence is a non-linear phenomenon in fluid dynamics and represents a formidable challenge in computational science and engineering. Nowadays there are many researchers who are trying to develop various models within the framework of Reynolds-averaged Navier-Stokes (RANS) equations. Among the topics related to naval propellers, which have preoccupied researchers over time, is the turbulent regime of fluid flow around the propeller (considering or not the presence of the hull of the ship in its vicinity). The methods of modeling/simulation, analysis and interpretation that stimulate the interest of the authors of this work are Computational Fluid Dynamics (CFD) and Shear Stress Transport (SST). Documenting the results obtained by various researchers over time, with reference to the turbulent flow regime (targeting high-speed marine propellers) and the study methods used by them, the following can be briefly mentioned. In [1,2] authors highlight the usefulness of using Computational Fluid Dynamics (CFD) and SST methods for turbulence modeling and analysis in various domains, like marine engineering as well as aeronautical or civil engineering. Their results are relevant for real-world applications, but rely heavily on numerical simulations, requiring more robust experimental validations to confirm the accuracy of the modeling. Using Navier-Stokes equations for predicting the coherentstructures in turbulent flow, the study [3] concerns the local flow analysis around a rotating KP505 propeller in open water conditions at an advance ratio of 0.7. They [4] used the CFD method to compare propeller hydrodynamic performance in case of a single propeller, tandem propellers and contra-rotating propellers demonstrating that the last two increase propeller thrust. The ship's behavior in waves depends, among others, on propeller-hull interactions in waves. They demonstrate that the use of advanced models such as PANS or the sinusoidal blade motion can improve performance predictions. However, these approaches remain limited by the complexity of real-world operating conditions and the lack of comparisons with extensive experimental data. [PERSON], [PERSON] and their colleagues [5] were interested in the propeller movement at the stern of the caused by the ship motion in waves. The propeller performance was calculated using Computational Fluid Dynamics (CFD) at several constant tilt angles, the thrust and torque of the propeller being analyzed in sinusoidal pitch motion were compared with the results obtained in constant tilt angles. In study [6], the advance speed of the virtual propeller disk was determined using an improved momentum conservation principle combined with the body force method, enabling the accurate real-time calculation of the advance speed. Study [7] introduces a three-dimensional non-linear (k-\(\varepsilon\)) turbulence model to analyze flow dynamics, velocity distributions, and mass transport mechanisms in both a meandering and straight navigation way. With the help of ANSYS software CFX, authors of [8] studied the effects of the surface roughness and protrusions on propeller performance. Their conclusion was that efficiency is increased by protrusions located on the pressure surface of the propeller and those with 0.2 mm protrusions show the best performance. [PERSON] et al. [9] focused on analyzing the streamlines, velocity, and pressure distributions in and around the propeller region. Their study employed Ansys-CFX 14.0, utilizing a viscous flow finite volume solver with a two-phase Eulerian-Eulerian fluid model and the SST turbulence approach. Meanwhile, [PERSON] and [PERSON] [10] investigated the turbulent flow surrounding a marine cycloidal propeller using a 2.5-dimensional numerical technique based on the unsteady Reynolds-averaged Navier-Stokes equations coupled with the SST k-\(\omega\) turbulence model. They conclude that the hydrodynamic efficiency of analyzed marine propellers drops as the blade number increases.