A model-scale still water tank test is made to predict propulsive performance of a full-scale vessel.

The results can be used when important decisions about main engine, gearbox and propeller are to be made for a newbuilding. Furthermore, this type of data is utilized as baseline data for sea trials and/or performance evaluation of vessels in service. 

Three types of tests

Generally, still water tests consist of three standard types of model tests:

  • open water performance of the propeller alone. The result is a non-dimensional propeller characteristic where the first conclusions about the propeller design can be made, i.e. is the propeller efficient and how much power is needed to generate the requested thrust. Furthermore, the open water characteristics are important for QA checks during the self-propulsion model tests
  • resistance tests of the hull alone, i.e. hull without propeller but including all other appendages. This test indicates if the hull lines are optimal or if further optimization steps are needed, e.g. further CFD studies. The resistance is important for evaluation of the overall propulsive efficiency
  • self-propulsion tests with the appended hull where the propeller is mounted. These are the third and last tests to be carried out in order to have a complete performance prediction. Input from the open water and resistance tests is important for the self-propulsion analysis and full-scale performance prediction. The most important results of the self-propulsion tests are curves with propeller revolutions and power as a function of the vessel speed. 

In the combined analysis of all three tests, data describing the propulsive performance can be deducted, e.g. if the hull lines are suitable for the propeller, and how is the performance of the operating propeller as compared to the open water performance.

The International Towing Tank Conference (ITTC)

The still water tests follow the given ITTC recommendations. ITTC is the International Towing Tank Conference in which worldwide-acknowledged procedures for model tests have been developed and maintained for years.