Using propeller simulations to evaluate numerical modelling methods

As a ship’s propeller cuts through the water, it leaves behind it a turbulent wake. Understanding this turbulent flow is crucial for hydrodynamic optimization and noise reduction. However, the wake is extremely complex and challenging to model accurately.

Wang et al. studied propeller wake under heavy loading conditions, using more powerful simulation methods to explore the evolution of the wake instability.

“The mechanism of propeller wake behaviors, such as the evolution from stable regime to unstable regime and the flow phenomenon in a complex operating environment, have always been difficult and hot topics in the field of fluid mechanics,” said author Lianzhou Wang.

The researchers employed two numerical methods, an improved delayed detached-eddy simulation (IDDES) and a large-eddy simulation (LES), to evaluate the propeller wake as it developed from a stable regime to an unstable regime. Their goal was to study the complex dynamics of the wake and evaluate each method to see how well it captured those dynamics.

Both simulations showed the propeller tips created spiraling vortices, which eventually interfered with each other and devolved into general turbulence. The LES method produced a more detailed rendering of the turbulence than the IDDES method, but it predicted the vortex breakdown too early.

The researchers hope their analysis of these two numerical methods will help others looking to explore various propeller wake dynamics, and they are planning to do the same themselves in the future.

“The physical mechanisms of other instability phenomena of propeller wake, such as short-wave instability, long-wave instability and breakdown process, needs to be further revealed,” said author Tiecheng Wu.

Source: “Numerical simulation of the wake instabilities of a propeller,” by Lianzhou Wang, Tiecheng Wu, Jie Gong, and Yiren Yang, Physics of Fluids (2021). The article can be accessed at https://doi.org/10.1063/5.0070596 .