SITHYM

Simulation of Transients in Hydraulic Machines

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 Obiettivo del progetto (Objective)

'Because of the evolution of the electricity market in Europe hydraulic machines are operated in non conventional conditions. This leads to the apparition of strong transient flow phenomena that are not well understood. Conventional numerical simulation tools are not well adapted to capture these transient phenomena. It is proposed to use a novel approach based on the mesh-free technique Smoothed Particle Hydrodynamics to simulate these flows. This numerical method has recently proved its ability to overcome some major shortcomings of conventional CFD techniques. The method can also remarkably simulate fast-transient phenomena. The novelty of the approach is firstly that the SiTHyM projects aims at using the SPH method to simulate internal flows, secondly that a coupling of the SPH and Finite Volumes approaches will be achieved. The idea is to take profit of the ability of the FV method to model boundary layers efficiently and with a reasonnable cost, while the main part of the flow where convective phenomena are predominant is solved by the SPH method. As a consequence the method does not need any rotor-stator interface. It is expected that this feature will bring a major improvement to the study of rotor-stator interactions in transient phases. In order to implement the coupled method in an industrial CFD process, an efficient parallel implementation of the tool is required. The project will tackle a GPU implementation, as it is a very promising technology that has recently emerged in the HPC community. The numerical tool will then be applied to transient free surface flows in Pelton turbines and to transient internal flows in reversible pump turbines.'

Introduzione (Teaser)

EU-funded scientists developed a numerical tool to create robust hydraulic machine designs able to withstand vibrations.

Descrizione progetto (Article)

The electricity market evolution in Europe caused hydraulic machines to be operated in new modes because of frequent start-up and shut-down cycles. This led to the emergence of strong transient flow phenomena that are not yet clearly understood. Conventional numerical simulation tools are not well adapted to capture such transient phenomena.

The EU-funded project 'Simulation of transients in hydraulic machines' (SITHYM) used a novel approach to simulate transient flows and hydraulic loadings during unit start-up and shut-down. Researchers used a numerical method that does not rely on a computational mesh to solve transient flows in hydraulic machines.

This predictive approach was based on the smoothed particle hydrodynamics (SPH) computational method. The innovative part was SPH and finite-volume (FV) coupling. Based on this, FVs were used around hydraulic components to model boundary layers efficiently. The main flow part in which convective phenomena are predominant is solved by the SPH method.

Project members eventually developed a variant to the standard SPH method to manage moving boundary conditions for internal flows. This method was used successfully to simulate the start-up of a pump turbine in turbine mode. Notably and despite the coarse discretisation, it was still possible to measure the hydraulic loading on various hydraulic components.

To implement coupling in an industrial computational fluid dynamics process, efficient parallel implementation of the tool is required. To this end, scientists relied on a hybrid parallel strategy that allows multi graphics processing unit computing.The developed tool enables engineers to assess the capacity of the installed machines for safe operation even in modes that were unavailable at design time. Project activities have laid the foundation for optimisation of simulations with innumerable applications in mechanical engineering and the energy sector.