CFD challenges in hydro-machinery
Prior to the last decade, experimental investigation, mostly at the final stages of the design cycle, was the primary method of study into the complex flow of moving water, making the analysis of hydro-machinery design at all stages extremely costly. With the constant growth of affordable computing power, the role of computational modeling in fluid dynamics investigations continues to become more and more prominent. CFD analysis is now accepted as a valuable analysis tool contributing to the understanding of 3D transient flow in hydraulic structures and machinery.
Pumps and hydraulic turbines, engines with water or liquids as the working fluid, produce flows with a variety of physical phenomena including cavitation, large pressure gradients and strong rotational and curvature effects requiring a numerical model that is well-tuned and validated for the complex interaction of these flow features. To accurately capture flow behavior in pumps and turbines a number of application-specific topics must be addressed, in particular high quality meshes for complicated geometries, flows with highly fluctuating pressure dynamics, time-dependent solutions, rotor-stator interactions, interaction of hydraulic structures with the flow, and optimization of hydraulic designs.
The confidence of industry and academia in the use of CFD techniques in the hydro-machinery field can only be achieved with the successful application and validation of CFD codes. Computational verification of hydraulic designs at a range of operating conditions should be efficient and reliable while providing the engineer with a detailed understanding of the flow complexity, all within a tight project timeframe.