Rev­o­lu­tion­iz­ing water drone propul­sion: a hybrid toroidal rim-driven design

A New Era of Propul­sion Inno­va­tion – Powered by CAESES

Under­wa­ter drones, commonly known as Under­wa­ter Unmanned Vehicles (UUVs) or Remotely Operated Vehicles (ROVs), are trans­form­ing marine research, offshore energy, and rescue oper­a­tions. Yet, design­ing propul­sion systems that meet the growing demands of these appli­ca­tions remains a major engi­neer­ing challenge.

In a recent bachelor’s thesis, Tomáš Jakuš of Brno Uni­ver­sity of Tech­nol­ogy explored a new approach: com­bin­ing toroidal and rim-driven pro­peller tech­nolo­gies into a hybrid design. Using advanced para­met­ric modeling and sim­u­la­tion, this novel pro­peller promises higher effi­ciency, lower noise, and greater debris resilience – a perfect match for the complex tasks facing next-gen­er­a­tion UUVs.

At FRIEND­SHIP SYSTEMS, we’re proud that CAESES supports inno­v­a­tive engi­neer­ing like this, enabling smarter, faster design of cutting-edge marine propul­sion systems.

The Design Chal­lenge: Powering a Drone for Extreme Environments

Picture a drone nav­i­gat­ing the treach­er­ous depths of the world’s second deepest flooded pit cave, where space is tight, battery power is limited, and debris poses constant hazards.

This project targeted exactly that scenario. The pro­peller design had to:

• Fit within a compact 60 mm diameter
• Provide equal thrust in forward and reverse for maneuverability.
• Maximize energy effi­ciency for long missions
• Allow debris to pass safely, min­i­miz­ing the risk of entanglement

The Solution: A Hybrid Toroidal Rim-Driven Propeller

Toroidal geometry

Loop-shaped blades elim­i­nate tip vortices, leading to less energy loss and less noise. Inspired by inno­va­tions like MIT’s toroidal drone pro­peller, toroidal designs can sub­stan­tially improve efficiency.

Rim-driven thruster

The blades are mounted on a rotating outer ring, sim­pli­fy­ing the overall arrange­ment and allowing debris to pass through easily, enhanc­ing its reli­a­bil­ity in harsh under­wa­ter environments.

The hybrid design inte­grates these features: a toroidal blade form powered by a rim drive. The goal? Aiming to reduce drag and improve bidi­rec­tional thrust while sim­pli­fy­ing assembly and enhanc­ing resilience to fouling and debris.

Engi­neer­ing the Concept – Powered by Para­met­ric Modeling and CFD

Workflow Overview

CAESES gen­er­ates geometry vari­a­tions using design para­me­ters like blade count, cen­ter­line angle, stagger angle, and advance ratio. These vari­a­tions are then trans­ferred to Ansys Work­bench via the API, allowing for auto­mated meshing, sim­u­la­tion setup, and hybrid ini­tial­iza­tion. The sim­u­la­tion is run on an HPC, eval­u­at­ing thrust, torque, and effi­ciency. The results are then trans­ferred to the opti­mizer, which refines the design. If a set of design para­me­ters leads to a null solution, it is flagged as invalid. This auto­mated pipeline reduces manual workload, accel­er­ates design explo­ration, and ensures only feasible, high-per­form­ing designs are selected.

Design Modeling with CAESES

A fully para­met­ric model of the pro­peller geometry was created, with key vari­ables such as:

• The blade cen­ter­line was defined as a qua­dratic curve, spanning a defined angle (χ) between its end points on the rim.
• The stagger angle (ψ) was intro­duced to define a tandem-like blade con­fig­u­ra­tion by adjust­ing the cen­ter­line rotation.
• The cross-section of the blade was modeled using a NACA 0021 sym­met­ric airfoil, selected for its balanced per­for­mance in both forward and reverse flow operation.
• Addi­tion­ally, tra­di­tional design vari­ables included the number of blades (B) and the advance ratio (J).

Using CAESES, the design space was explored effi­ciently allowing geometry vari­a­tions to be linked seam­lessly with sim­u­la­tion workflows.

Sim­u­la­tion with Ansys Fluent

The para­met­ric model was incor­po­rated into Com­pu­ta­tional Fluid Dynamics analysis, uti­liz­ing Ansys Fluent sim­u­la­tions of fluid flow, tur­bu­lence, and cav­i­ta­tion poten­tial for detailed per­for­mance analysis. The setup had been opti­mized through­out the oper­at­ing con­di­tions with mesh inde­pen­dence and grid refine­ment studies demon­strat­ing accurate, repro­ducible results.

Physical Testing

Fol­low­ing the virtual design process, a physical pro­to­type was con­structed and tested in a tank envi­ron­ment in a con­trolled setting with sensors mea­sur­ing thrust, torque, and power draw. The testing results con­firmed that the hybrid pro­peller had more thrust and was more effi­cient than pre­dicted; and there was also excel­lent bidi­rec­tional thrust, con­firm­ing the thrust per­for­mance pro­jected in the simulation.

Results at a Glance

The hybrid pro­peller demon­strates that with the right geometry and design tools, it’s possible to achieve:

• Longer mission endurance
• Energy-effi­cient, quieter operation
• Safer nav­i­ga­tion in chal­leng­ing environments

The Bigger Picture: Design Inno­va­tion with CAESES

The project show­cases how CAESES helps engi­neers model complex geome­tries, effi­ciently search large design spaces, and link CAD to sim­u­la­tion tools. This facil­i­tates the design-to-analysis workflow, accel­er­at­ing inno­va­tion in marine propul­sion and other design areas. The com­bi­na­tion of intel­li­gent design and advanced digital toolsets is crucial for creating effec­tive, reliable, and green propul­sion systems.

About the Author

Tomáš Jakuš com­pleted this research as part of his bachelor’s degree in mechan­i­cal engi­neer­ing at Brno Uni­ver­sity of Tech­nol­ogy. The work was super­vised by Ing. David Štefan, Ph.D., and high­lights modern design approaches at the inter­sec­tion of fluid dynamics, marine engi­neer­ing, and para­met­ric modeling.

Read the full thesis:

Design and Opti­miza­tion of the Geometry of a Periph­er­ally Driven Water Drone Drive  

FRIEND­SHIP SYSTEMS: Shaping the Future of Marine Propulsion

At FRIEND­SHIP SYSTEMS, we help engi­neers design more and faster with CAESES, our com­pu­ta­tional platform for sim­u­la­tion-driven design. With CAESES, you have complete control of your geometry and the per­for­mance-based para­me­ters that are critical to your design, keeping your design effi­cient, while innovating.

From early concepts to detailed pro­peller opti­miza­tions, CAESES inte­grates para­met­ric modeling with sim­u­la­tion and opti­miza­tion tools to facil­i­tate the entire workflow. This inte­gra­tion leads to rapid devel­op­ment, improved per­for­mance, and orga­nized creative potential.