# CFD Design Performance Analysis for a High-Speed Propeller
## 5 Conclusions
For instance, at 300 RPM and v = 10 [m/s], the torque is approximately \(-\)20.55 Nm, suggesting that the incoming flow strongly opposes the motion of the propeller, causing it to act more as a hydrodynamic brake than as a thrust generator. As the rotational speed increases, the propeller begins to dominate the interaction with the fluid, and the torque transitions to positive values. This shift implies that the propeller is actively generating torque that can be converted into mechanical power. Under static water conditions (v = 0 [m/s]), the torque increases almost linearly, rising from 0.24 Nm to over 69 Nm between 300 and 5100 RPM. This reflects a consistent and progressive mechanical efficiency in a quiescent fluid environment. By contrast, at v = 10 [m/s], the torque enters the positive domain only after approximately 2700 RPM, indicating the presence of a minimum power threshold required to overcome flow resistance. Such information is essential for determining the overall efficiency of the system, since torque combined with RPM defines the mechanical power consumed or delivered by the propeller. Therefore, analyzing torque curves enables the evaluation of energy efficiency, identification of optimal operating regimes, and estimation of mechanical overload risks. Negative torque values at low RPMs suggest that these regimes should be avoided in practical applications to prevent unnecessary energy consumption and excessive stress on the mechanical structure. This study aimed to present a novel method for evaluating marine propeller suitability, targeting both the scientific community and, more critically, engineers involved in the design and construction of high-speed vessels who are continuously seeking innovative solutions. Given the current technological reality where engineers can autonomously model and 3D-print propellers, the authors propose a methodology for obtaining \"thrust curves\" and \"torque curves\", before printing the propeller. Thrust curves are instrumental in determining the vessel's attainable speed, while torque curves provide critical data regarding engine load. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**RPM** & **v = 0 [m/s]** & **v = 2 [m/s]** & **v = 4 [m/s]** & **v = 6 [m/s]** & **v = 8 [m/s]** & **v = 10 [m/s]** \\ \hline  
\hline \end{tabular}
\end{table} 
Table 9: The numerical values for the diagram in Figure 17.  
The results demonstrate a noticeable reduction in the propeller's generated thrust at higher speeds. This observation aligns with theoretical expectations, as the propeller itself acts as an appendage contributing to the overall drag resistance of the vessel. Specifically, at a speed of 10 [m/s] (approximately 19.5 knots), the propeller begins to generate positive thrust for the vessel only for a shaft rotation above 2700 RPM. From a hydrodynamic perspective, the data suggest that the propeller features a geometry well-suited for medium to high flow regimes, with a torque distribution that promotes both stability and energy efficiency. The evolution of torque as a function of RPM and water velocity can be used to determine key performance coefficients--such as the torque coefficient and advance ratio--which are essential for characterizing the propeller in open-water conditions. Additionally, these results may be extrapolated to assess cavitation risk, particularly in high-RPM and low-pressure regimes, where pressure distribution across the blades becomes critical. In conclusion, the reference propeller exhibits robust hydrodynamic behavior, with a clear transition between braking and propulsion regimes, and a demonstrated ability to adapt to varying flow conditions. These characteristics make it suitable for applications where torque control and energy efficiency are of primary importance. Furthermore, the investigations identified regions susceptible to cavitation phenomena. This identification is crucial for implementing targeted protective measures to extend the operational lifespan of the propeller.