Thrust of Marine Propeller CFD Simulation: ANSYS Tutorial

A marine propeller converts rotational energy into a forward pushing force. This force is called thrust. Calculating this power correctly is highly important for ship design. This guide runs a Thrust of Marine Propeller CFD project to measure these physical fluid forces. The computational setup follows the published test data from Savas Sezen et al. Their research provides the physical foundation for this Thrust of Marine Propeller fluent simulation. To see more of rotating cases, check our MRF CFD simulation category.

• Reference [1]: Sezen, Savas, and Omer Kemal Kinaci. “Incompressible flow assumption in hydroacoustic predictions of marine propellers.” Ocean Engineering186 (2019): 106138.

Figure 1: A physical marine propeller showing the curved metal blades designed to generate forward thrust in water.

Simulation Process: Multiple Reference Frame Configuration

The physical model uses the DTMB-4119 propeller with a radius of 0.25 m. A large cylindrical fluid domain surrounds the metal blades. The Fluent meshing tool divides this liquid space into 5,862,460 poly-hex cells. Polyhedral cells bend perfectly around the curved blades to keep the calculation stable.

The rotation is handled by the Multiple Reference Frame (MRF) method. The rotational speed is set to 2146 RPM. The incoming water enters the domain at an advance velocity of 2.15 m/s. For a similar underwater rotating setup, read our submarine propeller CFD using MRF tutorial.

Figure 2: The 3D geometry displaying the DTMB-4119 propeller and the rotating boundary zone.

Post-processing: Velocity Contours and Hydrodynamic Output

The visual contours and mathematical formulas define the complete propeller performance. The velocity magnitude contours show the water speed. On the front side, the water moves at a safe speed between 10 m/s and 17 m/s. On the back side, called the suction side, the water accelerates rapidly. Bright red zones appear at the blade tips. Here, the water hits a maximum speed of 34.30 m/s. Fast water creates very low static pressure. If the pressure drops too low, harmful vapor bubbles form on the metal. This physical problem is called cavitation. The radial velocity streamlines show the twisting water path. The spinning blades push the water backward and sideways. This creates a rotating wake field behind the propeller.

Figure 3: Streamlines colored by velocity showing the twisting wake field as the water leaves the rotating blades.

Figure 4: Velocity magnitude contours displaying the high-speed red zones at the tips and the slower blue zones near the hub.

To measure the mechanical power, the solver uses specific hydrodynamic formulas. These formulas convert the raw physical forces into non-dimensional coefficients.

• Advance Coefficient: J = \frac{V}{(nD)}
• Thrust Coefficient: K_t = \frac{T}{(\rho n^2 D^4)}
• Torque Coefficient: K_q = \frac{Q}{(\rho n^2 D^5)}
• Open-Water Efficiency:   \eta_o = \frac{(J K_t)}{(2 \pi K_q)}

The calculated results are placed in Table 1. The thrust coefficient is 0.29529756. This is the total forward pushing power. The torque coefficient is 0.061189746. This is the twisting resistance of the heavy water. For an advance coefficient of 0.201, the final efficiency is 15.4%. This low percentage is physically correct for a low advance speed. It proves the propeller is designed to pull heavy loads slowly but it needs improvement in design because it is wasting fuel and energy.

Table 1: Hydrodynamic Coefficients and Open-Water Efficiency

Frequently Asked Questions (FAQ)

• Why does the water speed increase on the back of the blade? Propeller blades have a specific curved shape. As the blades push through the water, this curve forces the fluid to travel a longer distance over the back surface, causing it to accelerate.
• How do you calculate open-water efficiency? Open-water efficiency is calculated using the advance coefficient, the thrust coefficient, and the torque coefficient. The specific formula is (J × Kt) / (2π × Kq).