The rudder is an essential element in the manoeuvrability of a conventional ship; a well-design of the rudder must ensure the manoeuvring response in service conditions of the vessel, as well in manoeuvres with large blade angles or maintaining the course in free sailing. Likewise, the rudder plays an important role in the propulsion of the ship because it interacts with the propeller, recovering part of the rotational energy contained in the water flow that leaves the propeller, improving the propulsive efficiency. This is the reason for which their design has several constraints that must be considered.
Some important aspects of a rudder design are:
- Arrangement (spade, with pintle, etc...)
- Position relative to the propeller
- Area and aspect ratio
- Type of connection to the rudder stock.
Rudder design as a steering element requires the definition of the vessel manoeuvrability requirements, specifying speeds, blade angles and propeller load. We must also take the ship hull form and dimensions into account, as they condition the manoeuvring response.
Rudder blade optimization from a power efficiency point of view requires a previous analysis of the water speeds downstream the propeller, to optimize the geometry and profiles of the blade for maximum power recovery. In this case, hydrodynamic study of the hull, propeller and rudder must be carried out all together. The design is done applying optimization techniques coupled with potential and viscous CFD codes, helping to define the optimum profile geometry in each section.
VICUSdt has experience in the design of adapted rudders, improving the propulsive efficiency of the ship by approximately 6%. These improvements have been stated by means of tests in towing tanks.
At the moment there are some ongoing research projects related to the improvement of rudder design for all types of vessels, from large fishing boats to ferries.
