Fully Automated Measuring in HSVA’s Old Medium Tunnel
HSVA’s medium cavitation tunnel – dating back to the 1960s – has recently been combined with an automated tunnel control system, enabling the facility to run huge measuring campaigns fully unmanned.
Background to this initiative was an order for determining so-called noise maps for model propellers of same geometry but different materials. Noise maps provide sound pressure levels of a particular (natural) frequency in dependence of both the propeller advance coefficient and the absolute inflow speed. To create such a map, typically some thousand noise spectra need to be acquired for different combinations of tunnel water speed and propeller rotation rate.
This long-lasting data acquisition task could be delegated to a new tunnel control system consisting of a Simatic tunnel control unit with OPC server, an Ono Sokki spectrum analyzer, and an Excel/VBA based data acquisition environment – all linked to each other by a Labview master program. The system ran completely unmanned and all night long to produce noise maps as shown below.
The modular structure of the system allows easy adaptation to a large variety of other measuring tasks, such as unmanned acquisition of propeller thrust break down data or (four-quadrant) open water characteristics.