-Fluid structure interaction (FSI)
Hydraulic turbines include both stationary and rotating components. The interaction of the components, mainly between the runner blades and distributor vanes, is critical when the frequency of the rotor-stator interaction (RSI) approaches the runner natural frequency1. In the recent years, several turbines have been exposed to heavy fatigue loading and development of crack in the turbine blades. The fatigue loading and the failures are associated with the hydrodynamic force and the response from the mechanical structure for the given condition. For safe and reliable design of the turbines, detailed understanding of fluid structure interaction (FSI) is essential. However, hydraulic turbine is a complex structure and extremely challenging to understand the behavior as mechanical response is dependent on the operating condition. While designing the turbine, factor of safety based on traditional design and experience is considered. However, it is not proved reliable all the time. The FSI is dependent on several parameters: (1) hydrodynamic damping, (2) nearby structure and submergence level, (3) mode-shape, (4) freestream velocity and vortex shedding, (5) damping during cavitation, (6) material properties, (7) rotational speed, (8) natural frequency of individual and combined structure, (9) flow compressibility, (10) wave propagation speed, etc.
Third Francis-99 workshop is the continuation of previous two workshops. The first workshop attempted to study the steady state operating conditions, and the second workshop attempted to study the transient operating conditions (load variation and start-stop). The third workshop will focus on FSI analysis under steady state operating conditions. Unlike the previous two workshops, the present workshop includes additional (simplified) test case of hydrofoil that allows simplified study of FSI to understand the mechanics behind the fluid structure coupling.
The experiments for the third Francis-99 workshop have been conducted under the HiFrancis project.
Scope of the workshop
Scope of the third workshop is fluid structure analysis under steady state operating conditions. More specifically, parameters such as study of mode-shape, nodal-diameter, deformation, fatigue loading, estimation of fatigue life, individual/combined natural frequencies, hydrodynamic damping, harmonic response, etc. will be investigated2.