Numerical modelling of the lock approach conditions

Context

When a ship crosses a canal or a river equipped with hydroelectric power stations, for example, it has to pass through one or more locks. These structures generally consist of a lock chamber, into which the ship enters. A hydraulic circuit raises or lowers the water level. The opposite gate then opens and the ship continues on its way.

The approach of ships to locks is regulated and, in particular, a maximum approach speed must be observed. The locks in question are fitted with a fuse at their upstream end to protect the lock gate in the event of a ship being unable to stop before the gate.

Objective

The objective of this study is to provide information to define the rules of admittance regarding entrance velocity of the vessels in the locks.

Numerical simulation are done in order to verify the final vessel’s velocity at the fuse taking into consideration that the vessel enters the ship lock with a determined speed and stops the motors without braking at the lock entrance.

Simulation and results

The present study focused on the upstream entry of two different ships, respectively a cargo ship and a tourism vessel. 3D models locks are designed taking into account the bottom bathymetry.

Both ships were accelerated to a given speed velocity, then released when entering the lock. The simulation is unsteady in order to capture the vessels dynamics and decelerations along the lock. A remeshing method with a mesh adaptation is used to take into account the movement of the vessel in the numerical domain. A Level Set Method is used to handle the free surface flow simulations of vessel’s dynamics. Turbulent effects are taken into account.

The study is twofold :

1. focusing on determining the maximum allowed entrance velocity based on the fuse specifications
2. focusing on the most frequent vessel’s entrance velocity and determination of final vessel velocity at the fuse

The main output of the simulation was the velocity/kinetic energy after deceleration due to the drag force alone in the locks, to assess the energy the fuse needed to absorb.

The video below shows a ship approaching a lock, the result of simulations carried out by OptiFluides.