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Ice formation phenomena can be observed in many natural and technical processes. The formation of an ice layer is mainly dependent on the surrounding thermal and flow characteristics such as surface temperatures and natural or forced convection in fluids. Those, however, are greatly influenced by the geometric constraints of the considered system. A naturally grown ice layer aspires in steady state to a minimum of energy dissipation. Driven by this goal, this phenomenon can be used as a natural idea creator for a further numerical optimisation of complex geometries. This paper presents in detail the methodology of an approach combining a natural optimisation represented by the naturally grown ice layer together with a conventional numerical optimisation method. Exemplarily, this approach is applied to optimise the shape of the separating web in a 180-degree bend in terms of minimised pressure drop as it is used in internal gas turbine cooling channels. For this, the separating web is cooled and the different ice layers are classified according to Reynolds numbers and wall to fluid temperature ratios. In a second step, the experimentally best performing ice contour is taken as starting geometry for a subsequent applied numerical optimisation using evolutionary algorithms.
180-degree bend, evolutionary strategy, ice formation method, optimisation, turbine blade cooling channel
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