Earthrace is a wave-piercing 78 ft. trimaran powerboat designed to circumnavigate the world fueled exclusively by biodiesel. Earthrace, which aims to demonstrate the viability of biofuel to to power a ship around the world, found FLOW-3D invaluable for simulating and optimizing their design performance.
(We) were able to see how the boat was likely to perform in the different types of seas we were likely to come across on our global voyage. We were then able to modify the design to ensure that not only speed, but fuel efficiency and safety were taken into account. — Pete Bethune, skipper of Earthrace
Validating Hull Designs
One of the primary goals of the Earthrace design is to minimize fuel consumption. To achieve this, a unique hull design was conceived so that the boat pierces through waves instead of going over them. This design allows Earthrace to maintain a nearly constant speed regardless of how rough the sea conditions are.
Simulation plays an important role in validating new hull designs, since flow characteristics around the hull affect many aspects of the ship’s performance. However, simulating Earthrace poses challenges because traditional flow simulation tools assume the flow past the hull is relatively calm. In heavy seas, Earthrace is likely to experience significant wave forces all around itself as it pierces through waves.
FLOW-3D was chosen by the Earthrace project because of its ability to simulate general 6-DOF motion of the ship hull while fully coupling its motion with the wave motion. The sea state is computed from a solution of the fully non-linear Navier-Stokes. The sea state is coupled with the ship hull’s motion, which is treated as a rigid body subject to 6-DOF motion (surge, heave, sway, pitch, roll and yaw) including the thrust generated by the ship’s engines.
XC Engineering, Flow Science’s associate in Italy, ran the simulations for Earthrace. The simulations produced an accurate prediction of the hull’s resistance including form drag, skin friction and interference drag. These results were validated against scaled model tests. As a result, the Earthrace team was able to hit the seas with great confidence in their design’s ability to break the world circumnavigation record.