SPACE- Desenvolvimento e validação de um modelo Smoothed Particle Hydrodynamic para aplicações a estruturas costeiras / A Smoothed Particle Hydrodynamic model development and validation for Coastal Engineering applications
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Ref.: PTDC/ECM/114109/2009
Budget (Total/UALG-CIMA): 127.787,00€
Starting date: Janeiro 2011
Ending date: Janeiro 2014
Coordinator: Eric Didier (LNEC)
Domain: Engenharia Civil e de Minas
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Due to the important role that both the coast and harbours play in the national economy, there is the need to protect the coastline and to have calm wave conditions inside harbour basins. This requires frequently the construction of protecting structures, which act as an obstacle to the natural wave propagation, creating areas of reduced wave activity. Knowledge on the hydrodynamic behaviour of these coastal and harbour protection structures is necessary for their design, to guarantee both its structural safety and functionality. The analysis of the hydraulic behaviour of the structure is usually carried out using semi-empirical formulae. However, direct application of these formulae is limited to simple structural configurations and to specific wave conditions. In engineering case studies, physical model testing is also undertaken, which permit a reliable evaluation of the structure’s efficiency. The greatest disadvantages of physical model tests are the required time for their construction and exploitation, their high cost and their lack of flexibility to changing structural geometrical characteristics. Moreover the results could be affected by scale effects that should be known in order to be corrected. In recent years, due to the continuous increase in computer power, numerical models have been developed further and their use is becoming increasingly attractive. The models should correctly represent all the physical phenomena involved, such as shoaling, breaking and flow in porous medium. In the last decade, numerical modelling of free-surface flow has attracted the interest of a large scientific community. Recently, models based on Lagrangian methods, such as the Smoothed Particle Hydrodynamics (SPH) approach, have emerged. One example of that is the SPHysics model. These methods, based on the Navier-Stokes equations, allow modelling of complex structures and phenomena in the surf zone, due to its completely mesh-free technique. SPHysics has been studied and applied in Portugal since October 2007, by LNEC research team in straight collaboration with the European group SPHERIC (Smoothed Particle Hydrodynamics European Research Interest Community), an international group (Special Interest Group for SPH) supported by ERCOFTAC (European Research Community On flow, Turbulence and Combustion). SPH method, and in particular the SPHysics model, was first developed and applied to astrophysics. Application to hydrodynamic simulations is recent, which means that further development is needed, especially to convert it into an useful tool for real case studies of coastal engineering. For example, wave generation is performed using a piston-type wave-maker without dynamic absorption; only impermeable structures can be modelled, whereas most of coastal protection structures are porous, etc. |
Overtoping at the Albufeira breakwater |
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The model also needs to be verified and validated for studying wave-structure interaction. The relevance of the validation is related to the required accuracy of the results as a function of the initial particle density, to the viscosity models and to the model parameters. The computational time is also vital and it is mainly dependent on the initial particle density. Consequently, this density has to be defined with a view to obtain consistent and accurate results whilst still requiring a computational effort admissible for practical engineering applications. For SPHysics systematic testing and validation, field and/or laboratory data are required. Although field data are more difficult to obtain and more costly than laboratory data, they are extremely valuable for model validation, since they are not affected by scale effects. In this respect, the University of Algarve has wide experience in field work, specially related to beaches. For coastal protection structures, these data are rare, not only in Portugal but worldwide. Furthermore, these data, together with physical model data obtained for the same conditions, will enable the quantification and correction of scale effects. Finally, scale effect will be analyzed by comparing all results: field data, physical model data (scaled) and numerical data (different scales). The expected results are the SPHysics further development, testing and validation with field and physical model data, including a user-friendly interface, with a view to create a useful tool for coastal engineering studies. Its versatility and capabilities yield a promising model. Future model applications include studies related to sediment transport, interaction between petroleum and water during spilling, wave energy plants, among others. Vídeo de 19 de janeiro sobre a Campanha do projecto SPACE
Campanha do projecto “SPACE - Desenvolvimento e validação de um modelo Smoothed Particle Hydrodynamic” para aplicações a estruturas costeiras, que decorreu no passado sábado, dia 19 de Janeiro de 2013 (condições de tempestade). Para além de pretender contribuir para a validação e melhoria dos modelos numéricos amplamente usados na predição das condições de overtopping em estruturas costeiras, o projeto pretende ainda colher dados in-situ que permitam caracterizar fluxos de overtopping e sua frequência, associados a diferentes condições de agitação marítima. Os dados adquiridos contribuem diretamente para a gestão de risco em áreas de actividade portuária onde estão presentes estruturas de protecção marítima. No âmbito do projeto, efectuámos no dia 19 de Janeiro medições de onda e vento no molhe Oeste da Marina de Albufeira, molhe este bastante frequentado por pescadores e turistas e que observa ocasionalmente episódios de overtopping. Durante a campanha, as ondas atingiram cerca 4.5 m (Hs) e alturas máximas de cerca 6.5 m, provocando episódios quase sucessivos de overtopping no molhe. >> video |
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