SCALE EFFECTS IN THE MODELING OF BULWARKS, FREEING PORTS, AND WATER ON THE DECK OF SHIPS

Draws up certain guidelines for scaling the flow of water out of freeing ports, over bulwarks, and across the deck on ship models. Because water on the deck can affect both the ship's motion and crew operability it is important that conditions on the model simulate the real conditions of the ship. Because of effects such as viscosity and surface tension modeling begins to break down as the model size decreases. Orifice and weir flow were used to analyze freeing port and bulwark flow respectively because of their similarities. An experiment was performed to supplement the limited data for small diameter orifices. Results of the experiment were consistent with available data and provided helpful data for anlayzing the scaling problem. It was found that for each of the flows there was a minimum diameter or depth for which it would be possible to scale the flow properly. By equating these minimums with the smallest relevant depth of water on the ship, a limiting model scale size was reached. Various methods were devised to determine the relevant depths for static and dynamic conditions. The results indicate three major categories for scale size validity. For ratios lower than 20:1 the modeling is generally valid except possibily for roll damping. From 20:1 to 60:1 certain areas of scaling may model incorrectly, depending upon the specific geometry. For 60:1 ratios and higher it is likely that most flows will not scale properly and one must be aware that a model test in this ratio range will not accurately scale water on deck.

  • Corporate Authors:

    Massachusetts Institute of Technology

    Department of Civil Engineering, 77 Massachusetts Avenue
    Cambridge, MA  USA  02139
  • Authors:
    • Kahn, L A
  • Publication Date: 1976-1

Subject/Index Terms

Filing Info

  • Accession Number: 00131203
  • Record Type: Publication
  • Source Agency: Massachusetts Institute of Technology
  • Files: TRIS
  • Created Date: Apr 21 1976 12:00AM