# CFD Design Performance Analysis for a High-Speed Propeller
## 4 Results and Discussion
### Velocity on propeller  
Figure 9 highlights that the maximum speed is reached on the tip of the blades (yellow to red color on the drawing). Even when the water speed is 6 [m/s], on the tip of the blades the flow can reach a speed of up to 30.48 [m/s]. This phenomenon can be explained by the combination of the propeller's rotational speed and centrifugal effects [30] occurring near the blade tips. From a scientific standpoint, the pronounced increase in local velocity at the blade extremities has several implications:  
* The blade tip effect amplifies local velocity because the outermost points of the blades travel at a significantly higher linear speed compared to sections closer to the hub. As a result, the relative velocity between the blade and the fluid increases, leading to accelerated flow around the blade surface. Figure 8: Pressure on propeller [Pa]. * The substantial velocity differential between the axial inflow (6 [m/s]) and the local tip velocity (30.48 [m/s]) generates a steep pressure gradient, which contributes significantly to thrust generation but also introduces risks such as cavitation. * The regions highlighted in yellow and red indicate zones of maximum velocity--these colors not only reflect an intensified flow but also mark potential critical points in terms of blade structural integrity. These areas are subject to the highest dynamic loads. * Tip vortices and turbulent flow structures may emerge as a consequence of this phenomenon, potentially reducing overall propeller efficiency and leading to energy losses. This simulation is highly valuable for marine propulsion engineering, offering insights into blade geometry optimization, avoidance of overload regimes, and adaptation of blade profiles for high-speed applications. The data support energy distribution analysis around the blades and provide a foundation for calculating coefficients such as the pressure coefficient (C\({}_{\text{p}}\)) and estimating propulsive efficiency under turbulent flow conditions. Tables 4 and 5 summarize the case studies for the middle of the analysis interval (v = 4 [m/s] v = 6 [m/s], respectively). As presented in Table 4, the simulations performed at a constant inflow velocity of 4 [m/s] and varying rotational speeds of 300, 1800 and 4200 RPM highlight a clear and continuous evolution of the propeller's hydrodynamic behavior as a function of rotational regime. At low RPM, the pressure and velocity fields are weakly developed, with minimal pressure differentials and low flow acceleration, indicating a subcritical operating regime with limited thrust and negligible fluid-structure interaction. As the rotational speed increases, the pressure gradient across the blade surfaces becomes more pronounced, and local flow velocity rises significantly--particularly near the blade tips. These changes reflect a shift toward efficient thrust generation, where hydrodynamic loading becomes substantial and the propeller operates under more favorable energetic conditions. At the highest rotational speed, extreme pressure values and peak surface velocities are observed, exceeding the inflow velocity by several times. These conditions signal the onset of turbulent flow features, elevated structural loads, and an increased risk of cavitation, especially in low-pressure regions on the suction side. Overall, the trend reveals a transition from a passive to an active hydrodynamic regime, where enhanced propulsion performance is accompanied by intensified mechanical stresses and cavitation risk. These insights are essential for defining optimal oper  
Figure 9: Velocity on the propeller [m/s]. ating parameters and for validating the propeller's design from both performance and durability perspectives. As illustrated in Table 5, the pressure and velocity distributions at 1500, 3600 and 5400 RPM (with constant inflow velocity of 6 [m/s]) highlight the progressive evolution of the propeller's hydrodynamic performance.