Three cases are proposed to the participants. They all correspond to the simulation of the operational mode T, i.e. the top of the propeller curve. The first case is designed to evaluate the capability of different turbulence models for steady draft tube flow simulations. The second case is concerned with unsteady calculations, which may allow a comparison with steady calculations and an evaluation of the turbulence models for this matter. It will also yield new information on unsteady flow structures. The third case is related to the optimization of the draft tube and represents the ultimate goal. The optimization is geometrically limited to fit inside the actual one in order to decrease renovation coast. This case gives a large importance to the engineering qualities, the flow understanding and imagination of each participant and is expected to give rise to very interesting and constructive discussions.