Calculating Energy for Water Propulsion with Circular Blades

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To calculate the energy required for water propulsion through circular blades at 3 meters per second, one must determine the mass of water being moved and its velocity. The kinetic energy equation is essential for this calculation, providing the minimum power needed under the assumption of 100% efficiency. However, actual power requirements will be higher due to inefficiencies in the system. Estimations can be improved by using correlations based on Reynolds number and specific propeller designs. Generally, efficiency for pumps or propellers is estimated between 50-75%.
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How would you go about calculating the energy required to propel water through a circular-type blade at 3 metres per second??

Thanks.
 
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in this case you would be calculating power (energy per time)

think about how much mass is moving, and how fast it is going.

then use the equation for kinetic energy.

bear in mind, that this is the MINIMUM amount of power required, since it is assumes 100% conversion of propeller work to kinetic energy. The actual number is much greater and difficult to predict.

It is probably only estimable by using correlations based on the reynold's number and propeller design.
 
Obviously it depends on the device, but you can figure 50-75% efficiency for a pump or propeller.
 

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