river energy

[margssmith]

how much energy is used in transportation on a river

[magicdice]

the whole river? find it's mass (conveniently water has a density of 1kg/m^3 so finding it's volume would do), work out how fast it's going, multiply them together & halve it

[trilobite]

... and subtract the mass of the bedload, the mass of the suspended load, and the friction of the river bed, (this being proportional to the width of the river and the co-efficient of friction, which itself is determined by the nature of the river bed ie rock, sand mud etc.) 

All put together, you have a whole load of variables and a pointless question.

[Peter Pedant]

My turn My turn

From my MKS hydrodynamics course the density of water is 100 000 kg m-3. A cubic metre cant be 1 kg, just think of a litre.

Its either ten to the four or ten to the five

although what trilobite says is absolutely true, this difficulty does not make engineers - boring little b*stards at the best of times - give up.

They just approximate. Google Chezy and you;ll see what I mean. Chexy equations are used in open channel flow and are not that big a deal.

howver that is not the question - the q mentions energy used in transportation and not river flow energies.

 

In other words if you had a barge of 10 metric tonnes what energy would be reqd to yank it up stream 100 km againt a flow of 0.1 m/s?

Interesting q., Marge

Are there any engineers out there?

 

[Peter Pedant]

sorry i get 1 cu metre of water to be 1000 kg

[1 m is 100 cm, so 1 ** * is 100 power 3 cc.

but 1000 cc is 1 kg so  1 000 000 cc is 1 000 kg]

[magicdice]

so sue me, peter pedant.

[paralysis]

none