Like a conventional helicopter, an autonomous underwater helicopter (AUH) can move horizontally and vertically, but that is where the similarities end. Designed with surveys and environmental monitoring in mind, the disk-shaped AUH bears more of a resemblance to a flying saucer and relies on horizontal and vertical thrusters to control its motion and produce a stable hover.

Wang et al. conducted numerical simulations to investigate the craft’s hydrodynamic properties, important for selecting appropriate thrusters, battery capacities, and trajectories for a specific mission. They obtained information about the complex flow around the AUH, as well as instantaneous drag and lift coefficients.

“These hydrodynamic coefficients are important quantities to determine appropriate thrusters for the AUH,” said author Zhikun Wang. “The multiscale vorticities, the influence of the installed working loads, and the correlation of the force acting on the AUH with the surrounding flow structures are determined via Improved Delayed Detached Eddy Simulations. Furthermore, we performed Dynamic Mode Decomposition analysis to study the spatial and temporal details of the large-scale and dominant wake flow structures behind the AUH.”

The three-dimensional simulations revealed crucial information about how the AUH maneuvers through the water at different pitch angles and incoming flow velocities. The spatial and temporal behavior of the wake flow will be important for drag reduction measures.

In the future, the authors will continue to analyze the hydrodynamic performance of the AUH to further understand its maneuverability.

“Investigating the hydrodynamic characteristics of the AUH is crucial for achieving good control, improving its design, and planning the path,” Wang said.

Source: “Improved delayed detached eddy simulations of flow past an autonomous underwater helicopter,” by Zhikun Wang, Guang Yin, Muk Chen Ong, and Ying Chen, Physics of Fluids (2023). The article can be accessed at