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Optimization and Computational Fluid Dynamics - Department of ...

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178 René A. Van den Braembussche<br />

Fig. 6.23 Definition <strong>of</strong> θ distribution<br />

Fig. 6.24 Parameterized thickness distribution perpendicular to the blade camber line<br />

(not to scale)<br />

can vary between 20% <strong>and</strong> 35% at hub <strong>and</strong> shroud (2 extra design parameters).<br />

The number <strong>of</strong> blades could also be a design parameter to be optimized,<br />

but has been fixed to 7 for manufacturing reasons. This brings the total<br />

number <strong>of</strong> design parameters that need to be defined by the optimizer to 23.<br />

6.6.2 Multidisciplinary Objective Function<br />

The OF driving the multidisciplinary optimization increases with decreasing<br />

aero performance <strong>and</strong> when the aero <strong>and</strong> mechanical requirements are not<br />

met<br />

OF = wm · Pmech + wη · Pperf + wm · Pmass + wM · PMach<br />

The first penalty concerns the mechanical stresses. Limiting the maximum<br />

stress results in an inequality <strong>and</strong> geometries that do not satisfy this condition<br />

should be eliminated. However, this information about undesired geometries<br />

can also be used to guide the optimization algorithm towards acceptable<br />

ones. This is achieved by adding to the OF an extra term that increases

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