A one-dimensional hydroacoustic model is set up to perform the numerical simulation of the rotor-stator interaction of a Francis pump-turbine scaled model. The numerical results enable to identify both rotating diametrical modes in the vaneless gap between the 20 guide vanes interacting with the 9 rotating impeller blades and the standing waves in the spiral casing. Moreover, the simulations enlighten the interaction between these rotating diametrical modes and the standing waves.