Projects / Programmes
Modelling of hydrodynamics, sediment transport and sediment bound pollutants using the SPH method
| Code |
Science |
Field |
Subfield |
| 2.20.00 |
Engineering sciences and technologies |
Hydrology |
|
| Code |
Science |
Field |
| T220 |
Technological sciences |
Civil engineering, hydraulic engineering, offshore technology, soil mechanics |
mathematical modelling, hydraulics, SPH method, sediment, retention volume of reservoirs, sediment transport, transport of pollutants, dam break
Researchers (16)
Organisations (2)
Abstract
SPH (Smoothed Particle Hydrodynamic) is a relatively new method in hydraulic modelling, where discrete particles are used to perform simulations. Recently the method is more and more often used to solve hydraulic problems worldwide. The advantages of the method are: it does not require a numerical grid to describe the computational domain, thus the modelling resolution can be very fine. Moreover, pollutants, their transport and some of their transformations can be described using such method. The description of the two-phase flow is easier and more reliable compared to other known method, since it does not require additional equations to describe the free surface. This is of particular importance for modelling of sudden events, such as waves due to different impulses or flow due to dam-break. Comparisons of SPH modelling results and laboratory measurements show excellent agreement for free surface, which is of great importance in simulations of maximum level that water reaches at, for example, flow over the top of a dam or at the dam-break. One drawback of the method is longer computational time (or use of more powerful computers) due to a large number of particles which are necessary for detailed description of the modelled phenomena. The project will concentrate on practical aspects and use of the SPH models in Slovenian hydrotechnical practice. Theoretical background and basic algorithms are well described in the literature and several ready-to-use computer models, programmes and libraries are available on this topic. Using these, it is possible to achieve good results during the available time for the project.
The following problems connected to Slovenian hydro-energetic objects will be treated: 1) consequences of eventual dam-breaks; 2) the influence of bed-load transport on retention volume decrease in the reservoirs and both of its impacts: on flood-security and efficiency of the energy production of the power plants, and 3) transport of sediment-bound pollutants into and out of reservoirs during the flow through the bottom-outlets.
In the three-year duration of the project, the following results can be expected: 1) transfer of the published theoretical knowledge into Slovenian hydrotechnical practice, 2) use of already developed and published models to solve the practical problems in Slovenian hydrotechnical practice, 3) a comparison of the currently used 1D, 2D and 3D models based on the control volume method with the new SPH method, 4) calibration of the newly developed models on practical cases for which measurements are available 5) upgrade of the existing and development of new algorithms in accordance with the needs of the Holding Slovenske elektrarne (HSE), in particular to a) cases of partial, gradual, or, in the worst-case scenario, complete and immediate dam-breaks, b) modelling a decrease in the reservoir retention-volume due to bed-load transport, c) modelling the flushing of sediments due to flow through the bottom-outlets of the reservoirs, and d) modelling the desorbtion of pollutants from sediment in reservoirs; on similar problems (for example oil-spill modelling), the advantages of particle-based methods over widely-used control-volume methods have already been determined.
After the first year we expect the first comparison between the models; improvements and calibration of the new models are planned for the second year and during the third year an operational tool, capable of dealing with all the four proposed types of simulations will be ready to use. During the last year a comparison of the SPH modelling tools with existing environmental river models will be performed.
Significance for science
The SPH method is a recent method in hydraulic research and at the moment it is only used by a few institutions and scientists. Our research on mathematical modelling of phenomena and processes in dam breaks, sediment transport, and transport of particle-bound pollutants using the SPH method is an important contribution in hydraulics and environment protection on a global level. With the realisation of the proposed project we are among the first to use this type of research for computing practical cases. We were also the first in Slovenia to use SPH for practical application in the area of water enginering.
The SPH method and SPH-based mathematical models are in relatively early stages of development. Numerous theoretical improvements are therefore still possible. The developed three-dimensional mathematical model Tis Isat, its mathematical background, implementation and the addition of a new boundary condition, are important achievements on the international scale. The currently available methods of describing friction between liquid particles and the walls at domain boundaries are inadequate because they result in the formation of an area of particle “shoving” between the wall and liquid. This causes flow irregularities. The Tis Isat model with the built-in improvement of the boundary condition is at least as good as other published and utilised models. A comparison with measurements published in literature (Martin and Moyce, 1952) showed better agreement than other models, which is especially evident in longer simulations of water column collapse. The Tis Isat model is significantly faster than the models used for comparison. Additional improvement of boundary conditions enabled a larger computational time step. The SPH simulations are time-demanding and therefore, such an improvement is of great importance. The results of Tis Isat were acknowledged by the “SPHERIC” society (of which FGG is now a member) and published in their internet newsletter. The Tis Isat model, the new formulation of the boundary condition and the comparison with measurements are described in detail in an article published in the Journal of Mechanical Engineering.
The model Tis Isat, partially based on our own theoretical expertise, was upgraded with new theoretical and applied knowledge. The model was verified using measurements in natural and laboratory conditions. It was upgraded with pollutants and suspended sediment transport as well as the possibility of simulating sediment resuspension and flushing in the case of erodible bed. Advective and dispersive transport of pollutants and sediment were taken into account. Despite the rapid development of the SPH method and models, at present only the Tis Isat model is capable of all these simulations. This improved model has significantly wider possibilities of use: beside hydraulic research studies, the model can be used for simulations of sediment dynamics in reservoirs, as well as water quality simulations. Such simulations are especially important in areas with polluted sediment, which are often found in Slovenia and abroad (e.g. HPP reservoirs and, coastal areas where polluted sediment is transported by rivers). Verification of the model also included new measurement techniques (non-contact visualisation methods), which enable measurements in very short time intervals using cameras with high Fps ratio.
The method was integrated in the teaching process at the Faculty of Civil and Geodetic Engineering of the University of Ljubljana. SPH is included in several curricula. The method is the topic of several graduation theses and a doctoral dissertation. The junior researcher collaborating on the project has co-authored most of the publications in the last three-year period. Especially the younger staff members who were involved in the project have numerous possibilities of international collaborations and will be able to apply the obtained knowledge in the development of water engineering in Sloveni
Significance for the country
The SPH method and its practical use offer a wide range of uses in hydraulic and environmental research and are therefore interesting to water management, especially in the area of hydroenergetics. The improved model represents an important tool for Slovenian water-engineering community and the society in general. It can contribute to more efficient energy production from renewable resources and improve the quality of life in flood-endangered areas. A very important contribution is also increased flood protection made possible by applying the simulation results in areas where possible dam-breaks can cause substantial damage and endanger human lives. The method is directly linked to the priority tasks of environment protection and energy saving. Hydroelectric reservoirs are highly environmentally sensitive areas where pollutants are often deposited in the sediment. Knowing sediment and suspended solids dynamics in these areas and especially knowing flow processes in the areas of hydroelectric structures are important factors in adequate management of renewable energy sources and natural resources in general.
Good collaboration with co-financers has enabled direct information on the actual needs of the Slovenian water-engineering practice and on the other hand, the applications could immediately be tested in solving actual problems. As the first reference case, a partial embankment break of a planned pumped-storage hydro power plant reservoir was defined. Measurement data obtained on a physical model and a previously developed mathematical model were used to verify and calibrate the Tis Isat model. Good agreement of results was obtained, showing that Tis Isat can be used as the numerical part of an operative tool in assessing various types of dam break risks. The second reference case is the study of flow in a channel with instantaneous expansions and contractions. In this case, detailed measurements on a physical model were used to verify the model. Both case-studies were presented to wider expert society.
Collaboration with top experts and organisations in the field of the SPH method within the SPHERIC society, of which the Faculty of Civil and geodetic Engineering is the first Slovenian member, is an important promotion of the knowledge and work of the University of Ljubljana and of Slovenia. Participation at scientific meetings of the society enables access to the latest findings and techniques that are being introduced and implemented within the expert group of SPH developers. The contacts obtained in this way and the potential future collaborations with institutions that use this method are an important potential for inclusion into new international scientific and expert circles.
The development of the Tis Isat model is an exceptional example of transferring international knowledge into the Slovenian scientific and professional milieu. Cooperation with co-financers and the research institute (Jožef Stefan Institute) enables practical application of theoretical knowledge obtained at the University. It also provides optimal hardware and software and sufficient data as input parameters used in the models.
The personnel included into the project (especially young researchers) have wide opportunities for international cooperation and with the obtained knowledge they will be able to contribute to the successful scientific and expert development in Slovenia. The transfer of knowledge between institutions that include the fields of education, research and economy (CGS plus, d.o.o.) and the cooperation in research and implementation of state-of-the-art modelling and result visualisation tools represents a great potential for further cooperation.
With the developed graphic interfaces, the SPH method is efficiently used in the educational process in undergraduate courses. It is included in several curricula at the postgraduate level.
Most important scientific results
Annual report
2008,
2009,
final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Annual report
2008,
2009,
final report,
complete report on dLib.si
