# CFD Design Performance Analysis for a High-Speed Propeller
## 5 Conclusions  
The numerical method employed in this research incorporated a wide range of propeller rotational speeds (from 300 RPM to 5400 RPM, with increments of 300 RPM) and various vessel speeds (from 0 to 10 m/s, with increments of 2 [m/s]). Figure 14: Turbulence convergence diagram for v = 6 [m/s] and 3000 rpm. Figure 15: Wall and boundary convergence diagram for v = 6 [m/s] and 3000 rpm. Figure 16 illustrates the \"Thrust-Propeller RPM\" diagram (the numerical values were indicated in Table 8). The data obtained from the simulation of the marine propeller in ANSYS Fluent provide a detailed representation of its performance as influenced by variations in rotational speed (RPM) and inflow water velocity. The fixed-pitch three-blade propeller, with a diameter of 14 [cm], was tested in a virtual environment to evaluate the axial force generated under diverse operating conditions. The dataset clearly reflects the evolution of this force with respect to the two key variables: RPM and water speed. Under stagnant water conditions (v = 0 [m/s]), the axial force increases markedly with RPM, confirming the typical behavior of a propeller operating in a non-flowing medium. This near-exponential growth suggests an efficient conversion of mechanical energy into  
Figure 16: Thrust vs. propeller RPM diagram. \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 8: The numerical values for the diagram in Figure 16.  
thrust, unaffected by external flow disturbances. However, as the flow velocity increases, particularly in the 2-10 m/s range, the propeller enters a more complex regime in which dynamic interactions with the incident flow significantly alter its performance. At lower RPMs, the axial force becomes negative, indicating not only a lack of thrust generation but also hydrodynamic drag acting in the direction opposite to intended motion. This behavior may be attributed to unfavorable interactions between the blade geometry and incoming flow, resulting in a braking effect. Nevertheless, with increasing RPM, a gradual reversal of this phenomenon is observed. At intermediate water velocities (v = 4-6 [m/s]), the threshold RPM required to achieve positive axial force appears to lie between 2400 and 2700 RPM, denoting a minimum performance benchmark. Surpassing this threshold enables the propeller to regain control over the flow field and to once again convert mechanical input into useful axial thrust. This transition from drag-dominated to propulsion-dominated regimes is essential for characterizing the functional capabilities of the propeller and has implications for both propulsive efficiency and cavitation potential across different operational scenarios. In the upper RPM range (3000-5400 RPM), the axial force becomes progressively more positive, regardless of the flow velocity, demonstrating the propeller's capability to operate effectively in dynamic environments. This trend suggests that at higher water speeds, the propeller not only overcomes hydrodynamic resistance but utilizes it as a stabilizing factor. Consequently, optimal performance is achieved at high RPMs combined with moderate to high water velocities, where the maximum axial thrust is significant and indicative of elevated propulsive efficiency. Figure 17 represents the \"Torque-propeller RPM\" diagram (the numerical values were indicated in Table 9). Figure 17: Torque vs. propeller RPM diagram. The simulation data illustrate how torque varies as a function of propeller rotational speed and water inflow velocity. At low RPMs, particularly under higher flow conditions, the torque values become negative, indicating that the fluid imposes significant resistance on the propeller. This behavior can be associated with a braking regime.