Kaplan Turbine: Blade Pressure and Cavitation Analysis

Kaplan Turbine CFD Simulation, ANSYS Fluent Training

Description

This project simulates a Kaplan turbine using ANSYS Fluent. Turbomachines, also known as fluid machines, are widely used across industry, making it essential to understand their behavior in a fluid environment. Turbomachines generally fall into two categories: the first group — such as fans and compressors — takes energy and transfers it to the fluid, while the second group extracts energy from the fluid and transfers it to the system, as seen in wind and water turbines. Kaplan turbines belong to this second category.

Kaplan turbines are a type of inward-flow reaction turbine, among the most widely used turbine designs in industry, operating through a combination of axial and radial flow concepts. Water enters through an inlet tube that rotates around guide vanes, flowing tangentially through these vanes before being redirected into a spiral pattern by the runner's propeller blades — ultimately driving the runner's rotation.

This project investigates water flow passing through a Kaplan turbine rotating at 3300 rpm. The geometry was designed in Design Modeler and meshed in ANSYS Meshing using an unstructured grid totaling 919,824 cells.

Methodology

Turbine rotation was modeled using the MRF (Moving Reference Frame) approach, applied through the Frame Motion option. Rather than rotating the turbine blades themselves, the surrounding fluid is treated as rotating at a velocity matching the turbine's own rotational speed, implemented through the MRF tool within Cell Zone Conditions.

Conclusion

Results include 2D and 3D contours of pressure, velocity, and surface pressure, along with velocity vector fields illustrating the fluid's rotational motion around the turbine blades.

The surface pressure contour reveals localized regions on the turbine blades experiencing notably reduced pressure — these areas represent potential sites where cavitation could occur, and warrant closer examination in subsequent, more detailed analysis to assess cavitation risk and its potential impact on turbine performance and blade integrity.