DEVELOPED ACTIVITIES
The original numerical model (SPHysics) was developed regarding the application to the case study (West breakwater of Albufeira Harbour), by implementing a piston-type wave-maker with an absorption system for the reflected waves, allowing the modelling of a semi-infinite flume, and consequently, suppressing the refection problems in the calculations domain. This will enable the increase of the simulation time, resulting on a fair statistical analysis of the results.

Convergence analysis on the numerical model resolution (number of particles) and comparisons with data from the physical model were settling the specific criterion for the future model applications on the studied structure.A coupling technique between FLUINCO (Teixeira, FURG) or Bouss-2D propagation models and SPH allows modeling a complete flume, from the wave-maker to the breakwater, taking into account the wave transformation along the flume. The coupling method and the active absorption implemented in the SPH code allows reducing significantly the computational domain and the CPU time.

The rock blocks or artificial blocks of armor layers of a breakwater are modeled by rectangular blocks located above an impermeable boundary. This technique for modeling porous media of breakwater allows to calculated forces on the blocks and flow inside the armor layers. Convergence analysis was performed for determining a resolution criterion inside the porous media.

The breakwater was fully-equipped in 2011-2012 and a protocol was established for any case of an eminent overtopping event. A topographic and bathymetric survey has been already made to the 12 m depth. Field measurements were collected during the 2012-2013 Winter during two overtopping events.

RESULTS
1. SPH MODEL: development and validation
For SPH numerical model developments (based on SPHysics freeware model), physical model tests were performed for three impermeable structures (vertical and rubble-mound breakwaters). The tests were defined to guarantee a consistent reproduction of the numerical model characteristics: the boundary conditions are the same as the physical model (important condition to the validation of the numerical model regarding the experimental data), such as the computational domain and the piston type wave-maker. The obtained data (free surface, pressure forces and overtopping discharge) enabled a criterion definition for the model resolution and to verify the model capability to estimate the impact forces in vertical breakwaters.




In order to model real coastal structures it is necessary to consider the porosity of the structure, made by stones or by artificial blocks. Thus, it was implemented in the SPH model the possibility of placing cubic blocks in order to directly model the porous layers and the flow inside and outside the layers (i.e. between the blocks). The main goal is to calculate the forces at each block over the time. Such information is important for future stability studies of the rubble-mound breakwaters.


2. CASE STUDY: OVERTOPPING OVER THE WEST BREAKWATER OF ALBUFEIRA HARBOUR

Field campaign




Physical model
The physical modeling of the breakwater section was performed at LNEC, in a 1:30 scaled 2D model. The wave flume has 49.4 m length, 1.6 m wide, and 1.2 m height. The breakwater is located 37.0m from the piston-type wave-maker. Several incident regular waves were tested for the maximum tide level, varying the wave height, H, and wave period, T. For the conducted tests, experimental data was collected with 10 resistive-type wave-gauges to obtain the time series of surface elevation at 10 sections, both in front and inside the breakwater.

For controlling the characteristics of the incident wave, a wave-gauge, G2, was located at the beginning of the smooth ramp (1.2º slope). Wave-gauges G3 to G7 allow obtaining the free surface elevation in front of the breakwater. Wave-gauges G8 to G10 were located at the armor layer for measuring the water elevation inside the porous layer and the water level above structure. Finally, wave-gauge G11 was located at the crest of the breakwater for measuring the water level above the impermeable slab. Overtopping volume was also measured using a water level gauge deployed in a tank located at the back of the structure.






Application of numerical models: AMAZON, IH-2VOF and SPH
Sensibility analysis, considering the parameters of each numerical model, was made for AMAZON, IH-2VOF and SPH models.




Application of SPH numerical model to breakwater of Albufeira
The numerical simulation was performed for a regular incident wave with 12s period, 2.5m wave height and a water level of +3.5m (CD) which correspond to 2.191s wave period, 0.083m wave height and water level 0.112m at 1:30 scale model.

A coupling technique between FLUINCO propagation model (Teixeira, FURG) and SPH allows modeling the complete flume and taking into account the wave transformation along the flume and the smooth ramp. The coupling is performed at section of gauge G5.

Wave-maker with active absorption is placed at section G5 of the SPH flume. The coupling method and the active absorption allow reducing significantly the computational domain and the CPU time. In SPHyCE, only the primary armor layer of the breakwater was considered and rock blocks were modeled by rectangular blocks located above the impermeable boundary. The resolution, i.e. the dimension of particles, is do=0.0022m (volume 4.85x10-6 m3/m) and corresponds to a number of particles of N=131503. The simulation time is 15s and the time step is around 1.7x10-5s.

Numerical results of free surface elevation are in good accordance with the experimental data outside and inside the breakwater. It was observed during the experimental tests that overtopping does not occur for the wave configuration presented here and the maximum run-up does not reach the end of the crest berm. Nevertheless, in the numerical simulation a small overtopping occurs with a mean overtopping discharge of 1.11x10-4 m3/s. This discrepancy is probably due to the influence of the subjacent porous layer. The water level above the rock armour layer obtained with SPHyCE is significantly larger than the experimental, explaining the difference in the overtopping volume.




Selected publications:

• Didier E., Martins R., Neves M.G., 2013, Numerical and experimental modeling of regular wave interacting with a composite breakwater. IJOPE - International Journal of Offshore and Polar Engineering, 23(1), pp 46-54.
• Didier E., Neves D.C.B., Martins R., Neves M.G., 2012, Modelling of an impermeable breakwater: comparison between SPH numerical model and physical model, RETERM, 11(1-2), pp 68-76.
• Didier E., Rodrigues A., Neves M.G., Neves D.R.C.B., 2013, Força de impacto num quebra-mar misto obtidas com um modelo numérico SPH e formulações empiricas. Proc. 8as Jornadas Portuguesas de Engenharia Costeira e Portuaria, eds Delegação Portuguesa da PIANC, Lisboa, Portugal.
• Neves D.R.C.B., Didier E., Neves M.G., 2013, Aplicação de modelo SPHyCE a estruturas porosas: Quebra-mar Oeste do porto de Albufeira. Proc. 8as Jornadas Portuguesas de Engenharia Costeira e Portuaria, eds Delegação Portuguesa da PIANC, Lisboa, Portugal.
• Dias J., Didier E., Neves D.R.C.B., Neves M.G., 2013, Modelação numérica à escala do protótipo de um quebra-mar de talude com o código SPHyCE. Proc. 8as Jornadas Portuguesas de Engenharia Costeira e Portuaria, eds Delegação Portuguesa da PIANC, Lisboa, Portugal.
• Didier E., Neves D.R.C.B, Teixeira P.R.F., Neves M.G., Soares H., Viegas M., 2013, Coupling of FLUINCO mesh-based and SPH mesh-free numerical codes for the modelling of wave overtopping over a porous breakwater. Proc. 6th SCACR – International Short Course/Conference on Applied Coastal Research, Lisbon, Portugal, (10 p. CDRom).
• Ferreira O, Reis T., Carrasco A.R., Neves M.G., Neves D., Didier E., 2013, Small overtopping at Albufeira harbour: filed measurements and modelling. Proc. 6th SCACR – International Short Course/Conference on Applied Coastal Research, Lisbon, Portugal, (10 p. CDRom).
• Neves, D.R.C.B, Didier E., Teixeira P.R.F, Neves M.G., 2013, Resolution refinement technique in a smoothed particle hydrodynamics numerical flume for coastal engineering applications. Proc. International Conference on Computational Methods in Marine Engineering V, MARINE 2013, B. Brinkmann and P. Wriggers (Eds), Hamburg, Deutshland, pp 388-399.
• Didier E., Neves D.R.C.B., Martins R., Neves M.G., 2012, Modelação de um quebra-mar de talude impermeável: comparação entre modelo numérico SPH e modelo físico. Proc. V Seminário e Workshop em Engenharia Oceânica – V SEMENGO, ISBN 978-85-7566-236-7, Rio Grande, RS – Brazil, pp 71-83.
• Neves D.R.C.B., Didier E., Reis T., Neves M.G., 2012, Overtopping of a porous structure using a Smoothed Particle Hydrodynamics numerical model. Proc. Coastlab12 – Fourth International Conference on the Application of Physical Modelling to Port and Coastal Protection, Ghent, Belgium.
• Didier E., Neves M.G., A semi-infinite numerical wave flume using Smoothed Particle Hydrodynamics. IJOPE - International Journal of Offshore and Polar Engineering, 22(3), pp 193-199, 2012.
• Didier E., Neves M.G., Reis M.T., Determinação do caudal galgado numa estrutura porosa utilizando um modelo Smoothed Particle Hydrodynamics. Proc. 2as Jornadas de Engenharia Hidrográfica, Lisboa, Portugal, 2012.
• Mariz S., Patrício T., Reis M.T., Neves M.G., Pires Silva A., Didier E., Hu K., Cálculo do galgamento no quebra-mar poente do Porto de Pesca de Albufeira: Aplicação dos modelos AMAZON e IH-2VOF. Proc. IV Conferência Nacional en Mecânica dos Fluidos, Termodinâmica e Energia, Lisboa, Portugal, 2012.
• Didier E., Martins R., Neves D., Neves M.G., Modelação física e numérica da interacção entre uma onda regular e um quebra-mar vertical, Proc. IV Conferência Nacional en Mecânica dos Fluidos, Termodinâmica e Energia, Lisboa, Portugal, 2012.
• Didier E., Martins R., Neves M.G., Vasco J.R.G., Interaction between wave and coastal structure: validation of two Lagrangian numerical models with experimental results. Proc. Computational Methods in Marine Engineering IV – MARINE 2011, ISBN 978-84-89925-31-1, (12 p. CDRom), Lisbon, Portugal, 2011.
• Didier E., Ferreira O., Matias A., Neves M.G., Reis M.T., Pacheco A., Desenvolvimento e validação de um modelo Smoothed Particle Hydrodynamics para aplicação a estruturas costeiras. Proc. 7as Jornadas Portuguesas de Engenharia Costeira e Portuaria, eds Delegação Portuguesa da PIANC, pp 30 (15 p. CDRom), Porto, Portugal, 2011.
• Didier E., Marins R., Neves M.G., Validação e aplicação de um modelo numérico SPH para o cálculo de forças num quebra-mar vertical. Proc. 7as Jornadas Portuguesas de Engenharia Costeira e Portuaria, eds Delegação Portuguesa da PIANC, pp 23 (18 p. CDRom), Porto, Portugal, 2011.
• Didier E., Martins R., Neves G., Análise da interacção entre uma onda regular e um quebra-mar misto usando um modelo numérico SPH. Proc. Congresso de Métodos Numéricos em Engenharia – CMNE, pp 131 (20 p. CDRom), Coimbra, Portugal, 2011.

Team

Eric Didier		Principal researcher		LNEC
Maria Graça Neves		Researcher		LNEC
Maria Teresa Reis		Researcher		LNEC
Óscar Manuel Fernandes Cerveira Ferreira		Researcher		UAlg
Ana Margarida de Almeida Matias		Researcher		UAlg
Diogo Rúben Castelo Branco das Neves		Research Grant Holder		LNEC
André Miguel Duarte Pacheco		Research Grant Holder		UAlg
João Dias		Research Grant Holder		LNEC
Ana Rita Carrasco		Research Grant Holder		UAlg