Modeling Aerodynamic Lift For Ultrafast Workboats And Passenger Vessels with Omnis Marine

Meanwhile, in a conventional monohull or multihull, fuel consumption per passenger is directly linked to the size of the vessel: the bigger the vessel, the lower the fuel consumption is per passenger when the boat is fully loaded.

 

Thanks to the aerodynamic lift, faster means lighter and more efficient

A2V technology has changed the rules by developing and commercializing a new generation of fast and fuel efficient passenger transport vessels. The company markets workboats for the offshore industry, the commercial passenger maritime transport industry, and the states for their patrol, surveillance and rescue missions. How? They have designed and patented a wing-like catamaran geometry, which at high speed provides aerodynamic lift above the water, alleviating the vessel and thus reducing its power requirements. Thanks to the aerodynamic support, above a critical speed, the faster A2V vessels go, the less fuel they use.

 

“The A2V vessel has a fuel consumption of about 9 liters per passenger per 100km at 50 knots, independent on vessel size, from 10 to 100 passengers, from 12 to 30 meters. As a comparison, present state-of-the-art crewboats typically burn more than 30 liters per passenger per 100km and travel below 40 knots”. (source: http://www.aavessels.com/concept/).

 

One of the challenges in the design of such a vessel is the modelization of the free surface deformation at high speed, to which the stepped hulls are very sensitive since the aft part of the hull is operating in the wake of the forebody. The aerodynamic with the ground effect, both in steady and unsteady conditions, has also been a challenge. In order to model the behavior in the waves with reasonable computational times, A2V carried out systematic aerodynamic analyses and used the results to build a mathematical model. This aerodynamic model was implemented in the hydrodynamic computations using Omnis Marine (formerly knows as FINE/Marine) dynamic libraries.

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CFD is the core of the design approach of this vessel. With Cadence’s software Omnis Marine, A2V relied entirely on simulation during the design of the fully instrumented 10.5m prototype.

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Accurate predictions

Computational Fluids Dynamics is the core of the design approach of this vessel. With Cadence’s software Omnis Marine, A2V relied entirely on simulation during the design of the fully instrumented 10.5m prototype. The full scale measurements showed that numerical predictions were accurate, as shown in the Figure 1 where numerical predictions are continuous lines and measurements are dots. The total drag is plotted versus speed for three different cases: (1) 10 knots head wind in red, (2) no wind in green and (3) 10 knots tail wind in blue. Omnis Marine also allowed detailed analysis of the flow to refine the design.