In this paper, the layout and the hydrodynamic interference of multiple propellers behind the ship is studied using numerical simulation. Using the self-propulsion factor as the evaluation standard, the influence of parameter changes such as front-to-rear distance, lateral distance and relative position of the thruster was evaluated and analyzed. The longitudinal advance of the thruster has a beneficial effect on the hull efficiency. Similarly, appropriately increasing the lateral distance of the thruster will also have a beneficial effect on the hull efficiency. The change of the self-propulsion factor mainly comes from the wake fraction, and the change of the thrust reduction is small in most cases. The research in this paper will provide a reference for the layout design of multiple thrusters.
As the requirements for dynamic positioning and maneuverability of marine engineering ships become higher and higher, the operation platform often adopts multi-thruster arrangement to improve the flexibility of manipulation. For multiple thrusters, different arrangements will have different interference effects on the hull-thruster and thruster-thruster, sometimes resulting in unfavorable factors such as thrust loss of the thruster unit and increased hull resistance. Analyzing and evaluating the influence of the parameters of the layout of multiple thrusters to obtain their regular characteristics can provide an important reference for the design of offshore engineering work platforms.
In recent years, many scholars have carried out related research work on the layout of multiple thrusters. Shrubsole (1990) proposed that there is interference between the propellers in ships propelled by three propellers. The working environment of the middle propeller and the side propeller is quite different, and a series of studies have been conducted through test methods. Lehn (1980) conducted an experimental study on the effect of the front and rear distance of propellers. The front propeller's wake will have a certain effect on the hydrodynamic force of the rear propeller over a longer distance. Tang (2012) carried out the influence of the forward and backward distances and lateral distances of two single-propeller models on the propeller hydrodynamics. His research shows that when the axial distance exceeds 5D (D is the diameter of the propeller), the hydrodynamic interference of the front and rear propellers tends to be stable, and after the lateral distance is increased to 2D, the influence between the two propellers becomes stable. Bi (2013, 2018) introduced the interference factor parameters, which combined the multi-propeller wake fraction and the thrust deduction into a single parameter. The interference factor of a four-pods boat was calculated and evaluated. Xi et al (2014) used a numerical method to predict the self-propulsion factor of a surface vessel with four thrusters, and analyzed the difference in the wake fraction of the inner and outer propellers, but ignored the interference between the inner and outer propellers. Therefore, the prediction accuracy needs to be improved in the future. Sun et al (2018) used numerical methods to study the effects of different rudder angles on the multi-propeller propulsion system. Zhou et al (2017) explored the four-propeller maneuverability under the combined propeller working conditions. They studied the slewing performance of two inner propellers, two outer propellers and four propellers respectively, and discussed the working combination scheme of the propeller at the best azimuthon performance. Sun et al (2016) used the RANS method to solve the hydrodynamic results of the double rudder ship with four propellers. The resistance of ship and the propeller hydrodynamic performance without free surface were studied, and achieved good forecast accuracy. It can be seen that many scholars have carried out a lot of researches on the hydrodynamic performance of multi-propeller ship, but there are still few studies on the layout of multi-propeller ship and their interference. This article mainly focuses on this issue, which is of great significance to the ship and propeller designer.