Neerstrom
The Neerstrom is a countercurrent and partially circular current in flowing waters. It forms in bays , behind jetties and other obstacles. A neer current is always weaker than the actual main current.
root cause
The Neerstrom is created by the drainage of water from the main stream on an obstacle, for example on a sandbank , a rock reef , a sheet pile wall or a river barriers . The draining water must be fed back into the body of water. First of all, a vortex is created that presses between the main stream and the bank and then directs the diverted water in this zone against the main stream. Such a circular flow often catches floating debris from the main stream.
Neer currents also arise from the screw current of a motor ship, for example in a canal or in a lock .
application
Ships make use of neer currents by using the countercurrent when traveling upstream. However, this only works for ships with a shallow draft, which can still sail in the mostly shallow bank areas.
hazards
There is usually a fairly sharp transition between the Neerstrom and the mainstream. If a ship moves from the Neerstrom into the mainstream or vice versa, part of the ship is moved upstream and the other part is moved downstream. This creates a strong torque , which often leads to the ship becoming unstable and overturning . In the transition, ships are difficult to steer. The yaw movement is also composed of two opposing movements.
See also
Individual evidence
- ↑ Neerstrom. Sailing Lexicon, 2015, accessed March 9, 2018 .