There are a lot of different energy saving devices (ESD) on the market, e.g. pre-swirl fins, ducts (Schneekluth, Mewis), and post-swirl devices (costa bulbs, rudder fins and hub fins).
The suppliers promise efficiency rates, which lie within achieved rates of former projects and the spread is often relatively high, e.g. savings of “2 up to 6%”. For ship owners it is difficult to decide, which device is the best solution for their particular ship design.
Ship owners often select a device only on base of the promised rates and/or try to judge the effectiveness due to model tank tests. As the devices are mainly fitted within the boundary layer of the ship hull, which cannot be modelled correctly in model scale, the promised/ measured rates are at least questionable.
With the use of RANSE methods, it is possible to compare the different devices in full-scale; errors due to scaling will be avoided. In addition, the boundary conditions of each run are exactly the same in each computational run – which is not possible to assure during model tank tests. Another big advantage is the possibility to get a deep view inside the fluid dynamics – analysing velocity vectors in any place can be used to optimize the device.
Conmecs provides efficiency analysis of any propulsion improving device – we are fully independent and can assist ship owners in the device selection process by using highly accurate computations.