Propeller Optimization

Design data for the Wageningen B-Series propellers, References 9 and the Gawn-Burrill series, References 10 are incorporated in the program enabling propeller performance to be predicted using either series. Three modes of optimization are available:

• Given design speed and rpm, determine optimum diameter, pitch and blade area ratio.

• Given design speed and diameter, determine optimum rpm, pitch and blade area ratio.

• Given delivered power and rpm, determine optimum diameter, pitch and blade area ratio.

There are three options available for Reynold's Number Correction:

1. No correction to be applied.

2. Correction according to Oosterveld and Oossanen, References 9.

3. ITTC 1978 method, References 11.

you are also able to specify that the propeller is a Controllable Pitch Propeller type and/or Noise Reduced. Either feature has the effect of reducing the propeller open water efficiency by 3% or a combined 6%.

The propeller optimization process checks the design against cavitation. To achieve this you have to enter a value of Shaft Height from which the cavitation number is calculated. By interpolating the Burrill 5% cavitation line with this value of cavitation number a minimum allowable value of blade area ratio is obtained. Hydro then ensures that the actual blade area ratio is greater than the minimum allowable value multiplied by you specified cavitation safety factor.

The actual BAR must also be greater than the user specified minimum Blade Area Ratio. Note that the propeller series data is limited by a minimum BAR of 0.4

Note:
If more than one loading condition is specified, the propeller is designed for the first condition (assumed to be the design condition) and the same propeller is then used for subsequent conditions.