navyspecial
1960s. At that time, Free Running turning circle manoeuvres were carried out in the Wind Wave and Current Basin. Since that time, the techniques of data acquisition and modelling have increased significantly. But more importantly, the time projects take has speeded up dramatically over the years.
A new century calls for a new approach, which has led to a redesign of the test set-up for Free Running submarines. The core of the submarine model is a re-usable, water- tight container (WTC) completely filled with measuring and control equipment. A new hull shape can be placed around the WTC for investigations into any type of submarine. The implementation of measurement tech- niques in the Seakeeping and Manoeuvring Basin using an on-line position measure- ment system, gives submarine designers and users the possibility to asses the quali- ties of their submarine design in a fast and reliable way. MARIN has been involved in captive model testing for submarines many times but Free Running Model tests have only recently been added to the toolbox of the submariner.
Ideal size MARIN’s Seakeeping and Manoeuvring Basin is ideal to perform a range of manoeuvring and seakeeping tests. At 170 m by 40 m, the basin is a good size for testing manoeu- vres in calm water and in waves. The long length of the basin facilitates acceleration and deceleration phase testing and with the width at 40 m, the basin can comfortably accommodate a submarine making a range of turning circle tests.
In addition, the versatile wave-makers of the Seakeeping and Manoeuvring Basin makes it possible to judge the submarine’s behaviour while sailing just under the
waves, in snorting or submerged conditions. The ability to combine an assessment of the submarine’s behaviour in calm water and in waves, means Free Running Model tests have the advantage of giving a com- plete picture in a short time frame, which is especially important for submarine designers.
For the model of the submarine, there are three important enablers: - Underwater power of up to 14 hours, meaning that the basin can operate its usual double shifts, without delays for recharging the submarine power.
- An accurate underwater position measurement system.
- The model-following capabilities of the car- riage of the Seakeeping and Manoeuvring Basin. This facilitates wireless, two-way communication between the carriage and
model, and as such, online control over the submarine.
Free Running manoeuvring tests for the Royal Netherlands Navy, comprising amongst other things, near bottom sailing, have recently been carried out. Results are being used to improve mathematical model- ling of the simulation code of the Walrus- class submarine. This is used for failure mode and effect analysis, as well as for crew training.
During manoeuvres, propeller thrust and torque and also rudder forces are measured and registered. This data is gathered with the motion data of the submarines. Together they form a basis to be able to compare the results of fast time or real time computer predictions, against the results of the Free Running Model tests.
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