# CFD Design Performance Analysis for a High-Speed Propeller
## 4 Results and Discussion
The local fluid velocity on the blade surfaces increases noticeably, especially near the blade tips, where orange and red bands appear--signaling substantial acceleration of the flow induced by rotation. This behavior suggests that the propeller is operating in an active and efficient regime, where the interaction with the fluid is strong enough to produce useful thrust forces, yet remains within safe mechanical limits without triggering cavitation risks associated with higher rotational speeds. From a hydrodynamic standpoint, the 1800 RPM regime represents a balanced zone between performance and stability, making it ideal for evaluating energy efficiency and calibrating numerical models. It serves as a valuable reference point in propeller analysis, allowing the clear observation of the transition from passive to high-performance operation without introducing major flow instabilities or excessive blade loading. At 4200 RPM, the pressure distribution becomes highly pronounced and well-defined. Bright red zones appear on the pressure side, while deep blue regions dominate the suction side, indicating a strong pressure gradient. Local fluid velocity reaches elevated levels, with extensive red and yellow areas, especially near the blade tips. This regime is characteristic of peak performance, where the propeller generates a powerful pressure and velocity field with maximum thrust potential. Although cavitation risk is reduced in the absence of external flow, mechanical stresses on the blades are significant, particularly at the tips. These simulations demonstrate how, in the absence of water inflow, the propeller generates pressure and velocity distributions solely through rotation, with a clear progression from passive to active regimes. Such observations are essential for understanding the fundamental behavior of the propeller and for calibrating numerical models under controlled conditions. The three simulations (Table 3) at rotational speeds of 1500, 3600, and 5400 RPM with a 10 [m/s] inflow velocity reveal the propeller's hydrodynamic response under increasing load. As the rotational speed rises, pressure and velocity gradients on the blade surfaces intensify, enhancing thrust generation and overcoming inflow resistance. At lower speeds, pressure differences and surface velocities are moderate, limiting performance. With higher speeds, pressure gradients and local velocities, especially near blade tips, increase sharply, indicating improved propulsive efficiency but also greater mechanical stresses and a higher risk of cavitation due to extreme negative pressures. These simulations demonstrate how increasing rotational speed enables the propeller to transition from a braking regime to one of efficient propulsion, with a clear evolution in the pressure and velocity fields. These observations are essential for optimizing the operating regime of the propeller in high-speed marine applications and for validating its hydrodynamic design under maximum load conditions. For a better understanding of the simulations and the results obtained, the following are detailed in the case analysis for:  
* the fluid flow velocity of 6 [m/s]. * the propeller shaft speed of 3000 [RPM]. Two aspects have been considered and detailed below. A. Pressure on propeller  
In Figure 8 two regions of interest can be observed on the tip of the propeller: the red region where the maximum pressure is reached; the blue region, where there are negative values and cavitation phenomena is most probable to occur (this region is usually protected by special surface treatments or more resistive material insertion). The simulation of pressure distribution across the propeller clearly highlights the complex hydrodynamic behavior of the blades during rotation [29].