UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Scale effects of freeing ports Williamson, Peter Bruce


Freeing ports are found on almost all ships and their ability to drain water from the deck of a ship in rough weather can be critical to both the ship and crews' survival. At present, tests of freeing port performance on models may not be performed due to the effects of viscosity and surface tension that arise due to the decreased scale. In this thesis, the effect of scaling down freeing ports to a model size is examined, and a method of testing freeing ports on models is proposed that would incorporate the monitoring of water on the deck of the model and a control algorithm that would control the discharge from the model. To examine the effect of scale on freeing port discharge, discharge through twelve different sizes of long narrow slots ranging from 1 to 15 millimetres high are tested. Comparisons are made between the cases of steady state discharge, with a constant head, unsteady discharge, with a declining head, and unsteady discharge with the test vessel rocking to generate the sloshing motion of the water that one would expect to find on the deck of a ship in rough seas. It is found that while larger holes drain water off at the rate that one would expect at full scale, the smaller holes can let off either too much water or too little water, depending on the relative water depth. For this reason, it appears that an active system is needed to be able to test freeing port performance successfully on models.

Item Media

Item Citations and Data


For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.