This is the author accepted manuscript.INTRODUCTION
The performance of a hydraulic reaction turbine is significantly affected by the efficiency of its draft tube. Factors which
impede the tube’s performance include the geometrical shape (profile), and velocity distribution at the inflow. So far, the
design of draft tubes has been improved through experimental observations resulting in empirical formulae or ‘rules of
thumb’. The use of Computational Fluid Dynamics (CFD) in this design process has only been a recent addition due to its
robustness and cost-effectivenesses with increasing availability to computational power. The flexibility of CFD, allowing
for comprehensive analysis of complex profiles, is especially appealing for optimising the design. Hence, there is a need
for developing an accurate and reliable CFD approach together with an efficient optimisation strategy.
Flows through a turbine draft tube are characterised as turbulent with a range of flow phenomena, e.g. unsteadiness, flow
separation, and swirling flow. With the aim of improving the techniques for analysing such flows, the turbomachinery
community have proposed a standard test case in the form of the Turbine-99 draft tube [1]. Along with this standard
geometry, with the aim of simulating the swirling inflow, an additional runner proposed by Cervantes [2] is included in
the present work. The draft tube geometry is shown in Fig.1. The purpose of this abstract is to outline the framework
developed to achieve the automated shape optimisation of this draft tube.This work was supported by the UK Engineering and Physical Sciences Research Council (EPSRC) grant (reference number: EP/M017915/1) for the University of Exeters College of Engineering, Mathematics, and Physical Sciences
