Author: matthieu

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Electrical passengers boat propeller design

We’ve recently designed a customized propeller for naval architects L2O naval

Their project is a hybrid sail + electric boat that carries passengers on regular lines in Brittany.

Since the boat is battery-powered, a propeller optimization has been carried to outperform the best available traditional B-series propeller.

The gains are following :

  • 6% of gain in consumption
  • 2x increase of strength
  • significative cavitation inception

Cavitation maps comparison :

cavitation map of optimized propeller
cavitation map of traditional propeller

After our loop of optimization with OpenFOAM, the propeller has been re-checked in CFD by L2O with FINE Marine. A very good agreement has been found in the results.

OpenFOAM vs FINE Marine results

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Hydrogeneration propeller design for sailing cargo : second iteration

After validation of performance of a first prototype machined in aluminium for SV GRAIN DE SAIL 2, we designed a second iteration of propeller according to bronze properties.

Since it has much more strength than aluminium, bronze alloy allows thinner blade sections and an increase in performances. It helps to reduce tip cavitation as well.

The fabrication quality was checked with 3D laser scanning method to ensure the final shape is close to the ideal one. The measured deviation on this part is typically +/- 0.3 mm but some small areas show a bit less accuracy.

3D Scan
First prototype in aluminium after a transatlantic loop

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Hydrogeneration propeller design for sailing cargo ship

Grain de Sail 2 – Loys LECLERCQ

We designed a large scale propeller for a hydrogenerator for the sailing cargo Grain De Sail 2.

The goal was to minimize the drag while producing the requested power and maintain a low cavitation despite the proximity of water surface

We designed the propeller geometry which was successfully tested on a transatlantic trip France –> New-York –> France.

underwater view of one hydrogenerator in front of the main propulsor

The measured performances revealed to be very close to what was expected, even in real-life conditions with rough seas and unsteady speeds.

Daily mean power production [kW] vs surface speed [kts] on a transatlantic trip and return
After 4 months of operation
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Benchmark of VP1304 propeller

Few ressources are publicly available to validate propeller numerical tools.

Among the exceptions is the VP1304 case : a variable pitch propeller design by SVA with published open-water results.

In an attempt to validate our VLM code for propulsion case, we have used the geometry tables of this propeller and made a reverse analysis with Vortex Lattice Method.
Below is displayed the comparison which show a good agreement between experimental data and VLM computation.

We can see we have margin of progress for small J values where our model seems to stall before the real one. However it is worth noting the good prediction around the nominal J for this propeller.

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Small-scale wind turbine blade design for racing multihulls

In 2017 we began a project to design a small wind turbine for high speed, marine environment, dedicated to racing multihulls.

The goals were to have a high efficiency propeller to minimize the drag and to be able to withstand a large range of wind speed : 15 to 60 knots.

We designed the blades with our VLM code with simply changing the fluid parameters to air and then optimized the shape with OpenFOAM.

The current design is a variable pitch propeller, made in carbon fiber.

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