A multi-objective factorial design methodology for aerodynamic off-takes and ducts

Fluid off-takes and complex delivery ducts are common in many engineering systems but designing them can be a challenging task. At the conceptual design phase many system parameters are open to consideration and preliminary design studies are necessary to instruct the conceptualisation process in an iterative development of design ideas. This paper presents a simple methodology to parametrically design, explore and optimise such systems at low cost. The method is then applied to an aerodynamic system including an off-take followed by a complex delivery duct. A selection of nine input variables is explored via a fractional factorial design approach that consists of three individual seven-level cubic factorial designs. Numerical predictions are characterised based on multiple aerodynamic objectives. A scaled representation of these objectives allows for a scalarisation technique to be employed in the form of a global criterion which indicates a set of trade-off geometries. This leads to the selection of a set of nominal designs and the determination of their robustness which will eventually instruct the next conceptual design iteration. The results are presented and discussed based on criterion space, design variable space and contours of several flow quantities on a selection of optimal geometries.