I The Physics of unloding sand from a barge

[oz93666]

TL;DR Summary

How to efficiently move sand with water jets.

I think it's easist first to watch a short vidio clip

I find these videos very relaxing to watch .. I got to thinking is this being done in the most efficient way?

The sand has to be suspended in the water to move it to the outlet ... The faster the water , the more turbulance and the sand stays suspended, so it seems to me the rule of thumb is the hose be aimed towards the outlet at all times .. Many times the workers hit the sand directly which will greatly reduce the water velocity , it will dislodge the sand but it will be more likely to settle out elsewhere and need moving again ...

Another way to maintain velocity is to carve narrow channels (with the water jet) to the exit point , wide expances of flow reduce velocity.

Any thoughts ?

 

[Baluncore]

They are moving the sand to the pump inlet using water jets. The volume ratio of water to sand, in order to be pumped, requires that high volume of water. The water volume that is needed to pump out the sand, is more than sufficient to dislodge and transport the sand within the hull.

The same pump, being used here to unload the bulk sand, would have been used to load the sand earlier, at the suction dredge site in the navigable channel.

The river has plenty of water to circulate. The cost of wages for local employment is not too high, and almost all of those wages circulate within the local economy. The cost of the diesel needed to run the slurry transfer pump cannot be reduced. How could the process be made more efficient?

Transport of sand like that is used throughout the lower Mekong River. There is the regular YouTube 'Nguyen Che Linh Channel', video from the Tra Vinh dam, that shows the almost over-loaded transport barges, with their slurry pumps, fighting to get from the tidal to the fresh water navigable river.
An example:

 

[sophiecentaur]

I love to watch dredgers dumping silt out of the hull by opening doors in the bottom. Very elegant to let gravity do the work. The ship slowly rises up out of the water.