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- Thread starter Matej
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SteamKing

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What type of object?

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As far as the physics go, it's a solid object with density equal to the density of the liquid

Anything else?

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SteamKing

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A.T.

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And in general the thurst will not be constant for constant power input, but depend on the speed.Since it is a submarine, the power produced by the propulsion machinery is converted into thrust, either by turning a propeller or by means more exotic.

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And in general the thurst will not be constant for constant power input, but depend on the speed.

And that's the point where I got stuck. I found an equation that works if the thrust is constant but that is not the case here.

Perhaps if I expressed drag as a loss in energy (speed

Not quite sure though, we haven't done anything like this at school so far and it might be a few years till we do.

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A.T.

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You won't get an analytic solution for this. The thrust itself is not some simple function but usually derived empirically or numerically. You have a chart like this:And that's the point where I got stuck. I found an equation that works if the thrust is constant but that is not the case here.

And get the thrust by:

thrust = (efficiency * shaft_power) / velocity

To get the speed as function of time you have to integrate the acceleration from the net force (thrust - drag) numerically. For low velocities there is static thrust data.

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