Armor block stability of submerged breakwaters predicted by numerical wave flume

Akira Matsumoto, Akira Mano, Jun Mitsui, Minoru Hanzawa

Research output: Contribution to journalArticlepeer-review


Submerged breakwaters are one of the most fundamental structures to protect coastal areas from wave action. To ensure the stability of a whole structure, it is primarily important to determine the required mass of armor units accurately. This study aims to evaluate the armor block stability based on a flow field calculated by a numerical wave flume. The flow field was calculated by using a 2D VOF-type numerical wave flume. The wave force acting on an armor block was calculated using the Morison formula. Drag, inertia and lift coefficients for the Morison formula were determined by using an exact 3D VOF-type numerical model. The resultant stability of the armor block was judged from a comparison between the wave force and the stabilizing force originating from the mass of the armor block. An evaluation method for the critical condition of armor block stability of submerged breakwaters is proposed. Parameters for the evaluation were calibrated through comparisons between experimental and numerical results. An impact wave force with short duration acted when the water depth above the breakwater was shallow. In such a situation, even if the peak value was large, the impulse was not so large. To estimate the displacement of the block, the equation of the motion of the block was solved. The agreement between predicted and experimental stability was improved by using the fluid force coefficient corresponding to an individual water depth condition. That is to say, the applicability of the model was shown to have improved.

Original languageEnglish
Pages (from-to)338-343
Number of pages6
JournalJournal of Coastal Research
Issue numberSPEC. ISSUE 65
Publication statusPublished - 2013


  • Hudson formula
  • Morison formula
  • Stabilizing force
  • VOF method
  • Wave force

ASJC Scopus subject areas

  • Ecology
  • Water Science and Technology
  • Earth-Surface Processes


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