Episode 7. A journey to PIV flow measurements at ship scale.

Sea Trials

As mentioned in the previous post, the development of the full-scale PIV unit – named FlowPike – was led by MARIN, with LaVision GmbH performing optical design and delivery of optical components. The optical design included simulating and selecting the individual components necessary to create a large (1 m wide, 3-4 m long) laser sheet, as well as applying special camera mounts that were resistant to vibration and therefore possible misalignment.
Besides this, a custom design was made for all the electrical and optical cables and the air and water hoses necessary for the operation of the cameras, and the laser and electrical motors used for lens controls. All these needed to extend from the unit mounted under the ship to the power/control equipment inside the ship, a distance of 10 m, passing through several water-tight bulkheads.
The biggest challenges of mechanical design included making a strong yet streamlined body that will be relatively easy to mount and dismount from the vessel, either in dry-dock or at the port in ballast conditions. This included designing a cradle for the device that is used for lifting and a dummy frame used for aligning the hull penetration and unit supports that need to be cut and welded onto the ship hull. Further, in order to enlarge the measurement area, the unit needed to be able to turn around its axis to a given angle and maintain the angle against the flow forces acting on it. This was achieved by placing a motor, an encoder and a brake in the front part of the device. Naturally, the water-tightness of the static and rotational seals and the cable feed-throughs on the bulkheads needed to be ensured as well.   

To be continued…

3D design of the PIV unit

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