Unsteady pressure measurements and numerical investigation of the jet control method in a conical diffuser with swirling flow

Abstract

The paper presents our numerical results and experimental measurements for swirling flow with precessing vortex rope into a conical diffuser with water jet control. A test rig was designed and developed at Politehnica University of Timisoara in order to investigate different flow control techniques. Consequently, a vortex rope like in Francis turbine cone at 70% partial discharge is generated into the test rig section. The jet control method is experimentally investigated in order to mitigate the vortex rope and its associated pressure fluctuations. The unsteady pressure is recorded in 8 transducers flush mounted on the wall of the test section at different values of the jet discharge. The amplitude and frequency of the vortex rope is obtained based on unsteady pressure measurements using Fourier analysis. The 3D computational domain corresponds to the test rig section. The three-dimensional full unsteady turbulent computation is performed with jet control for different values of discharge. In numerical simulation, the unsteady pressures are obtained on the cone wall at the same positions as those in experimental investigation. Consequently, the amplitude and frequency of the vortex rope are computed and validated with experimental data. As a result, the amplitude and frequency are diminished if the water jet discharge is increased.