Editing Ship model basin (section)

=== Towing tank ===
[[File:UCL OTT.jpg|thumb|The Ocean Towing Tank - with both towing and wave making facilities - at [[University College London]]]]
[[Image:NewcastleTowingTank.jpg|thumb|A model being tested in the Towing Tank of [[University of Newcastle upon Tyne|Newcastle University.]]]]
[[Image:Berlin-tiergarten vws 20050404 p1020295.jpg|thumb|Cavitation tunnel of the Versuchsanstalt für Wasserbau und Schiffbau in Berlin]]
[[Image:Cavitating-prop.jpg|thumb|Cavitating propeller in a water tunnel experiment at the David Taylor Model Basin]]
A towing tank is a basin, several metres wide and hundreds of metres long, equipped with a towing carriage that runs on two rails on either side. The towing carriage can either tow the model or follow the self-propelled model, and is equipped with computers and devices to register or control, respectively, variables such as speed, propeller thrust and torque, rudder angle etc. The towing tank serves for resistance and propulsion tests with towed and self-propelled ship models to determine how much power the engine will have to provide to achieve the speed laid down in the contract between shipyard and ship owner. The towing tank also serves to determine the maneuvering behaviour in model scale. For this, the self-propelled model is exposed to a series of zig-zag maneuvers at different rudder angle amplitudes. Post-processing of the test data by means of [[system identification]] results in a numerical model to simulate any other maneuver like [[Dieudonné spiral test]] or turning circles. Additionally, a towing tank can be equipped with a PMM ([[Ship motion test#Planar motion mechanism (PMM)|planar motion mechanism]]) or a CPMC (computerized planar motion carriage) to measure the hydrodynamic forces and moments on ships or submerged objects under the influence of oblique inflow and enforced motions. The towing tank can also be equipped with a wave generator to carry out seakeeping tests, either by simulating natural (irregular) waves or by exposing the model to a wave packet that yields a set of statistics known as ''[[response amplitude operator]]s'' (acronym ''RAO''), that determine the ship's likely real-life sea-going behavior when operating in seas with varying wave amplitudes and frequencies (these parameters being known as ''[[sea state]]s''). Modern seakeeping test facilities can determine these RAO statistics, with the aid of appropriate computer hardware and software, in a single test.