Is there a theoretical upper speed limit to jet drive?

[RatliffFranklin]

Is there a speed at which water would be entering the intake faster than the pump could expel it? Or is it just determined by available horsepower?

[jehardiman]

For a jet drive to produce thrust, the inlet velocity must always be less than the outlet velocity. There is a real limit caused by cavitation considerations which leads to a ram pressure issues which causes the inlet to jet diameters to vary in strange ways if you want to go faster.

On the other hand there are some really quirky things you can do theoreticaly...such as a suction drive.

[RatliffFranklin]

Originally Posted by jehardiman

For a jet drive to produce thrust, the inlet velocity must always be less than the outlet velocity. There is a real limit caused by cavitation considerations which leads to a ram pressure issues which causes the inlet to jet diameters to vary in strange ways if you want to go faster.

On the other hand there are some really quirky things you can do theoreticaly...such as a suction drive.

So in theory what might a suction drive look like? And what's the underlying principle?

[jehardiman]

Originally Posted by RatliffFranklin

So in theory what might a suction drive look like? And what's the underlying principle?

Suction caused by the lower inlet pressure/higher velocity of a centrifugal impeller.

[RatliffFranklin]

Originally Posted by jehardiman

Suction caused by the lower inlet pressure/higher velocity of a centrifugal impeller.

Okay, now I get it.

You're talking about replacing axial impellers with a centrifugal impeller.

http://www.ualberta.ca/~rchladny/ima...t/impeller.jpg