The programs behind the propeller design and analysis pages are based on the properties of the standard atmosphere with a density of 1.225 kg/m³. To design or analyze a hydroprop, the properties of water have to be taken into account.
Power and thrust of a propeller depend directly on the density of the fluid into which the propeller is submerged. As the density of the fluid can be changed on the Options card, you can design a propeller without any special specification. Typically, seawater has a density of 1025 kg/m³. This means, that a propeller, designed for air, will produce 1025/1.225 = 836.7 times the thrust when it is immersed into water. The same factor applies to the power consumption.
In order to avoid cavitation, the design lift coefficient should be fairly low, depending on the thickness of the airfoil and its velocity (pressure) distribution. Also, the vapor pressure depends strongly on the water temperature. As a rough rule of thumb, lift coefficients in the order of 0.2 (thick airfoil) to 0.4 (thin airfoil) should not be exceeded.
The analysis module can be used without changes. The resulting power and thrust coefficients can be used to calculate the power and thrust for any given fluid density.
[Considerations for Hydrofoils]
Last modification of this page: 20.04.06
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