Numerical investigation of hydrodynamics of the cavitating turbulent flow in a low head prototype francis turbine

Cavitation is one of the most critical hydrodynamic phenomena which occurs during the hydraulic turbine operations. Higher flow velocities (especially in high specific speed, low head Francis turbines) give rise to increased cavitation. Analysis of cavitating turbulent flow is one of the most important prerequisites for hydraulic design of the water turbines. Present work provides a closer insight of the phenomenon in a low head prototype Francis turbine of 3MW capacity. Different stages of cavitation are thoroughly analyzed numerically using ANSYS CFX and critical zones of operation are identified. A comprehensive cavitation analysis is performed and complete cavitation characteristics of the turbine is derived using steady state simulations for with and without cavitation cases by considering different operating conditions. Obtained computational results are validated with the experimental and available literature results which are found in a fair agreement.