What is Bank Suction and Bow Cushion?

  • When a vessel moves through a restricted channel, there is a restricted flow of water on one side of the vessel. This causes an increase in the velocity of water on that side, together with a drop of pressure head. This loss of pressure head results in a drop of water level at the nearer bank and the thrust is set up towards the nearer bank.
  • The greater fullness over the aft body of the vessel accentuates the thrust and it then appears more strongly at the stern than at the bows. 
  • The stern moves towards the bank, called bank suction, and the bow moves away from the bank called bank cushion.