Projects / Programmes
High fidelity experiments and simulations for understanding and predicting cavitation erosion
| Code |
Science |
Field |
Subfield |
| 2.13.00 |
Engineering sciences and technologies |
Process engineering |
|
| Code |
Science |
Field |
| T210 |
Technological sciences |
Mechanical engineering, hydraulics, vacuum technology, vibration and acoustic engineering |
| Code |
Science |
Field |
| 2.03 |
Engineering and Technology |
Mechanical engineering |
cavitation, erosion, simulations, experiments, CFD
Researchers (12)
Organisations (2)
Abstract
Briefly, cavitation is the occurrence of vapour cavities inside a liquid. Vapour structures are then entrained by the flow and violently collapse when entering regions of pressure recovery. The concentration of energy at collapse results in high stress levels, which can cause erosion. For a long time it was believed that cavitation should be avoided because of its negative character. Today cavitation is used in many processes (diagnostic and therapeutic medical applications, semiconductor processing and disinfection of water). Regardless whether cavitation is considered undesired or beneficial its erosion potential must always be considered.
Cavitation and consequently cavitation erosion is one of the most ubiquitous problems at operation of turbines, pumps, ship propellers and valves. As an example in pump turbine Avče the costs for treating the damage caused by cavitation sum up to yearly amount of 100.000 Euro.
Cavitation erosion is problem, which is difficult to approach, as it involves complicated flow phenomena combined with the reaction of the particular material from which the solid walls are made of. Despite large progress in cavitation erosion research in past years the phenomenon is still far from well understood.
This project aims at coordinating and integrating theoretical, numerical and experimental efforts to understand the processes involved in cavitation erosion from both fluid mechanics and material aspects. The emphasis will be on answering some of the key open issues of the cavitation erosion phenomenon and, in the last work package, the implementation of obtained results into a general prediction model. The topic will be approached in four work packages (Wps):
WP1: Measurements to gain new experimental information concerning the structure and the dynamics of cavitating flows will be performed. Non invasive experimental techniques such as high speed visualisation, X-ray imaging, time resolved stereoscopic PIV-LIF, IR and LIF thermography are planed for these investigations.
WP2: A ground breaking scientific strategy, based on innovative DNS and high resolution LES turbulence modelling with multi-domain decomposition, high-order compact finite differences, and massive parallel implementation, is proposed to address the issue of poor agreement of state of the art simulations on a small scale flow characteristics.
WP3: We propose to use innovative measurements of damage, such as time resolved SFS algorithm, simultaneous high speed observation of cavitation and cavitation erosion and PVDF pressure measurements, which enable detailed view into the process of damage occurrence.
WP4: The cavitation erosion prediction approaches are still predominately empirical and application dependent. The outcome of this WP will be a new improved, refined, general and purely physical method for prediction of cavitation erosion, which we will also implement into CFD software.
By determining the physics behind the cavitation erosion, the outcome will be a framework for improving and refining the methods for its prediction, leading to more efficient and longer operation of machines.
Significance for science
In March 2011 a small group of leading scientists in cavitation erosion research was invited to Grenoble to the Cavitation Erosion Workshop organised by the Office of Naval Research. There, we tried to determine the current state of the art and future directions of research. The following list of open questions was formed: – How to compare different laboratory erosion testing methods? – How to transpose erosion data obtained in the laboratory to full scale? – How to measure cavitation impact loads? – How good is it to use accelerometers on shaft housing for cavitation erosion prediction? – How to investigate, analyse and model failure mechanisms involved in cavitation erosion? – Is the concept of "Cavitation Intensity" relevant and how to define it? – How to estimate cavitation intensity from CFD? – What about the importance of bubble/bubble interactions in the cavitation erosion process? – What is the influence of fatigue type mechanisms in the cavitation erosion process? – What are the pros and cons of the various techniques of analysis of pitting tests? – What about an optimal design with respect to cavitation erosion? – What is the role of residual stresses in cavitation erosion? – Any hope to derive quantitative data on the mass loss rate from the only incubation period? – Any progress concerning importance of the micro-jet compared to the emitted shock waves? It is obvious that the phenomenon of cavitation erosion was still far from well understood in 2011. In the scope of this project we coordinated and integrated theoretical, numerical and experimental efforts to answer most of the questions that consider the process of cavitation erosion. Further on the results of the project represent an added value to the work in other areas, such as ecologically acceptable water treatment by cavitation.
Significance for the country
Cavitation and consequently cavitation erosion is one of the most ubiquitous problems at operation of turbines, pumps, ship propellers and valves. As an example in a pump turbine the costs for treating the damage caused by cavitation sum up to yearly amount in excess of 100000 Euro. By determining the physics behind the cavitation erosion, one of the outcomes will be a new framework for improving and refining the methods for prediction of cavitation erosion, leading to more efficient operation and longer lifetime of fluid machines and optimisation of the processes that utilise cavitation. Socio-economic influences of the proposed project will reflect in reduction of costs, which otherwise occur in hybrid physical model measurements. Namely, phenomenological models of relations between influential parameters in hydrodynamic systems will replace the additional measurements on the physical models of real systems. The same goes for verified and selected numerical models, which will be able to replace costly experimental work on physical models used mainly in design of new hydrodynamic objects. The proposed project therefore raises the science level of future users as well as their technological and competitive level in the EU and world markets. Positive impacts on the economy would thus be perceived on the national level and in the wider, regional area. Furthermore, it is necessary to emphasize that the results of the project served as a base and the fundamental idea for successful application the ERC CoG project. The results of the latter will, with meaningful cooperation, eventually further enrich the Slovenian economy.
Most important scientific results
Annual report
2014,
2015,
final report
Most important socioeconomically and culturally relevant results
Annual report
2014,
2015,
final report
