SEAJET HYDROMOLE. Image used by kind permission from SEAJET.

CFE Tool CFD Studies

The Business Need/Requirements

SEAJET is a leading provider of controlled flow excavation (CFE) tools, for subsea excavation and trenching. They have recently developed the world’s only fully electric CFE system, providing increased power, efficiency, and versatility. During the development process of their new HYDROMOLE tool, SEAJET needed to understand the theoretical performance of the system, in order to guide the development pathway and highlight the best routes to optimising the flow pattern.

SEAJET Streamlines closeup 5
SEAJET Surface streamlines

The Project

4c Engineering were engaged to investigate and evaluate the performance of one of the SEAJET tools using CFD (computational fluid dynamics) to model the behaviour of the device. A series of studies were carried out looking at the comparative performance with different combinations of guide vane, nozzle and nosecone components. Further investigative studies used a Design of Experiments (DoE) approach, in which the integrated CFD solver is able to directly alter the CAD model (e.g. blade pitch, nozzle diameter, guide vane profiles) between runs in order to investigate performance trends and suggest the combinations of input geometry likely to give optimal performance.

SEAJET Jet velocity profiles

Our Activities and Deliverables

4c’s activities included:

  • Simplification and update of CAD model to make it suitable for CFD simulation;
  • Simulation model setup and mesh refinement sensitivity checks;
  • Calculation of global results, such as propeller torques and forces, input powers, flow rates, and surface pressures on components;
  • Investigation of flow paths through CFE tool body;
  • Examination of water jet plume, mapping flow trajectories and velocities at various distances from the nozzle;
  • Design of Experiments studies coupled with the CAD model to investigate a more radical set of nozzle, nosecone, and guide vane geometry options.
SEAJET DoE control surfaces
SEAJET Flow trajectories
SEAJET Jet velocity


The initial set of studies provided SEAJET with confirmation of the likely performance of the CFE tool and increased understanding of the behaviour of the flow through the tool and the resulting jet plume. Subsequent physical tests have shown good alignment between the CFD model and real-life power and thrust measurements. The more exploratory Design of Experiments studies have provided useful insights to inform the development of future tool designs.