Shipbuilding Research Institute

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As a service provider for the shipbuilding industry, a shipbuilding test institute is an engineering office with attached hydrodynamic test facilities.

history

As early as 1870, William Froude carried out systematic towing tests in his research facility in Chelston Cross near Torquay . In 1876 a trough was put into operation by the Royal Shipyard in Amsterdam. In 1894, today's Krylov Research Center with a tow tank was opened in St. Petersburg . From 1900 to 1914 there was a towing test station for overseas ships ( models ) at the North German Lloyd in Bremerhaven, which Johann Schütte set up. One of the oldest research institutes that goes back to the KukMarine is the Shipbuilding Research Institute in Vienna, which has existed since 1912.

In Hamburg, Ernst Foerster was commissioned with the assistance of Blohm & Voss to found a new shipbuilding research institute. As early as March 1910, Ernst Foerster, chief engineer of merchant shipbuilding at Blohm and Voss, was able to win over both Hermann Blohm and the representative of the Hamburg Senate through a memorandum for his plan to build a large shipbuilding research institute in Hamburg - and later through a foundation from Consul Otto Schlick , Hamburg, also realize. It was opened in 1915. For the design and maintenance of the Hamburg institution he managed to win friends and colleagues in shipbuilding and industry and in numerous countries abroad, in study trips to German and foreign shipbuilding and industrial sites and by collecting funds for research work. His influence on the organization and management of the institute's supervisory board lasted for around 20 years from the start.

Investments

The following facilities are part of these test facilities:

  • a towing tank : a test tank in which resistance and propulsion tests on a model scale are used to determine how much power, i.e. what kind of machine, is required for the ship to reach the contractually agreed speed. Further, in order maneuverability to determine a series of Z-maneuvers is driven at different amplitudes and rudder angle from the measurement data by means of system identification created the opportunity to simulate such maneuvers computationally, for which the towing tank too narrow. The towing tank is provided with rails on both sides, on which the towing truck with all measuring devices and computers drives. In order for the model to be immersed in exactly the same depth at every point of the tank, the rails are not exactly straight in vertical direction, but rather follow the curvature of the earth with extreme precision.
    Some tow tanks are also equipped with a wave machine in order to carry out investigations of the sea ​​state . The equipment also includes a PMM system (Planar Motion Mechanism) or a CPMC system (Computerized Planar Motion Carriage) to forcibly move ships or other objects on the water surface or deeply submerged and to measure the hydrodynamic forces and moments. The fact that the term “towing tank” is used should not lead to the mistake that it is a closed container. Rather, it is a long basin or a channel in a correspondingly elongated hall.
Circulation tank UT2 of the research institute for hydraulic engineering and shipbuilding Berlin; popularly: "pink tube"
  • a cavitation tunnel to examine propellers . Conceivable as an annular tube with a very large cross-section, which is arranged vertically and extends over several floors. The measuring section is arranged in the upper area . A parallel flow is created there. A dynamometer is used to measure the propeller's thrust and torque at different ratios of the inflow speed to the propeller speed in order to optimize the propeller. With a stroboscopic lamp that flashes synchronously with the propeller speed, the cavitation bubble can be made visible as if it were standing still, in order to examine whether the propeller would be damaged by cavitation . So that this corresponds to the large version on a model scale, the pressure is lowered and the gas content in the water is carefully adjusted.
  • Workshops : Shipbuilding research institutes mill their ship models out of wood or paraffin, and some also make their own propellers. The installation and removal of measuring devices and the individual production of systems for special tests complete the task.

There are further test facilities that not all shipbuilding test institutes have

  • A maneuvering and swell basin : In contrast to the tow tank, it allows any angle between the ship model and the sea state, and it offers enough space for maneuvers for which the tow tank is too narrow, but by no means for all maneuvers. There is not enough space in such a special tank for a spiral test that fully measures yaw stability. In addition to natural (irregular) sea conditions, transfer functions (RAOs = Response Amplitude Operator ) can also be determined using wave packets in a single experiment for all frequencies.
  • an ice tank : For icebreakers and other ice-breaking ships, it fulfills similar purposes as the towing tank for open water ships. Depending on the thickness of the ice, resistance or required power as well as maneuvering behavior are relevant. There are also measurements of the forces that floating ice exerts on offshore structures. Closed ice sheets are frozen using a special process in such a way that the ice crystals are scaled down. Model tests are also carried out in brash ice.

In addition, shipbuilding research institutes have software and experience to numerically simulate the complicated flow around ships and their propulsion and control organs using CFD methods, which according to the current state of technology does not make model tests superfluous, among other things because suitable elementing is complex and is expensive. Shipbuilding research institutes also do not always obtain the line plans from the client, but sometimes design them themselves, or they optimize specified line plans based on the test results. The same applies to the propeller drafts.

goals and tasks

Model tests that are used by ship models are

  • Resistance and propulsion tests: This is used to investigate which machine (s) the ship needs in order to achieve the required speed. It is also investigated how much the axial force in the propeller shaft (thrust) differs from the force propelling the ship and is opposite equal to the drag. This difference is based on the fact that the negative pressure field in front of the propeller sucks the ship backwards and is described without dimensions as a suction number (thrust deduction fraction).
  • Wake measurement: This is used to measure the flow field behind the ship in order to know the approach velocity at which the propeller will work. This speed at which a free-moving model propeller is examined without a ship model differs from the speed at which the ship travels. This difference is dimensionless as Nachstromziffer described (ger .: wake fraction).
  • Paint testing: Allows the flow pattern is made visible on the outer skin to bilge keels and other attachments align.
  • Sea state tests: They serve a variety of purposes. In irregular (natural) sea conditions, the movements are statistically analyzed in the individual degrees of freedom, and it is documented whether and how often the fore or aft ship dips and the flat bottom hits the water with full force (slamming). How much water gets on deck is of interest, especially in open-top container ships, and just as sensitive the ship is to parametric rolling , especially in aft seas , which can lead to capsizing.
  • Maneuvering attempts, moving freely: This is usually used to check whether the maneuvering properties prescribed by the IMO are being adhered to and whether the ship can drive straight ahead in a stable manner.
  • Maneuvering attempts on the tied model: They serve special purposes.
  • Ice tests: They serve similar purposes as resistance, propulsion and maneuvering tests in open water. The relationship between the ice thickness and the required power depending on the speed as well as the question of how thick ice the ship can still break plays a special role.

Strictly speaking, these experiments (apart from ice) are an experimental solution to the dimensionless Navier-Stokes equation . Actually, both the Reynolds number and the Froude number should correspond to the large version. However, because this is not feasible (the model would have to be huge and run in mercury), only the Froude number is adhered to. In the absence of Reynolds resemblance, the model is covered with strips of sandpaper on the bow in order to adapt the transition from laminar to turbulent flow to the conditions in the large version.

Because these model tests are in competition with corresponding numerical calculations called Computational Fluid Dynamics (CFD), they are sometimes also referred to as EFD (Experimental Fluid Dynamics).

Organizational structures

Some shipbuilding research institutes work as commercial companies, others are state owned, for example subordinate to the Ministry of Defense. The shipbuilding research institutes are united worldwide under the umbrella organization ITTC (International Towing Tank Conference) in order to decide on common standards for the measurement procedures.

The world's most important shipbuilding research institutes are now in Europe. These are MARIN in Wageningen (Netherlands), the Hamburgische Schiffbau-Versuchsanstalt (HSVA) in Hamburg (Germany) and the SSPA in Gothenburg (Sweden). The largest German shipbuilding research institute is the HSVA in Hamburg. The VWS in Berlin is now shut down and in the process of dissolution, but passers-by can still get an idea of ​​the size of a cavitation tunnel from the striking red-blue building on Landwehrkanal / Straße des 17. Juni.

The Shipbuilding Research Institute was founded in Vienna in 1912 and has been working again since 1951 after being destroyed in the Second World War.

Individual evidence

  1. ↑ Karl-Heinz Hochhaus: Simulation in ship technology . In: Hansa , Heft 5/2012, pp. 29-32, Schiffahrts-Verlag Hansa, Hamburg 2012, ISSN  0017-7504

See also

Web links