DualSPHysics: from fluid dynamics to multiphysics problems

[Abstract:] DualSPHysics is a weakly compressible smoothed particle hydrodynamics (SPH) Navier–Stokes solver initially conceived to deal with coastal engineering problems, especially those related to wave impact with coastal structures. Since the first release back in 2011, DualSPHysics has shown to be robust and accurate for simulating extreme wave events along with a continuous improvement in efficiency thanks to the exploitation of hardware such as graphics processing units for scientific computing or the coupling with wave propagating models such as SWASH and OceanWave3D. Numerous additional functionalities have also been included in the DualSPHysics package over the last few years which allow the simulation of fluid-driven objects. The use of the discrete element method has allowed the solver to simulate the interaction among different bodies (sliding rocks, for example), which provides a unique tool to analyse debris flows. In addition, the recent coupling with other solvers like Project Chrono or MoorDyn has been a milestone in the development of the solver. Project Chrono allows the simulation of articulated structures with joints, hinges, sliders and springs and MoorDyn allows simulating moored structures. Both functionalities make DualSPHysics especially suited for the simulation of offshore energy harvesting devices. Lately, the present state of maturity of the solver goes beyond single-phase simulations, allowing multi-phase simulations with gas–liquid and a combination of Newtonian and non-Newtonian models expanding further the capabilities and range of applications for the DualSPHysics solver. These advances and functionalities make DualSPHysics an advanced meshless solver with emphasis on free-surface flow modelling.This work was partially financed by the Ministry of Economy and Competitiveness of the Government of Spain under project “WELCOME ENE2016-75074-C2-1-R” and financed by Xunta de Galicia (Spain) under project ED431C 2017/64 ″Programa de Consolidación e Estructuración de Unidades de Investigación Competitivas (Grupos de Referencia Competitiva)" co-funded by European Regional Development Fund (ERDF). We are grateful for funding from the European Union Horizon 2020 programme under the ENERXICO Project, Grant Agreement No. 828947 and the Mexican CONACYT- SENER Hidrocarburos Grant Agreement No. B-S-69926. Dr. J. M. Domínguez acknowledges funding from Spanish government under the program “Juan de la Cierva-incorporación 2017” (IJCI-2017-32592). Dr. C. Altomare acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No.: 792370.Xunta de Galicia; ED431C 2017/64México. CONACYT- SENER Hidrocarburos; B-S-6992

Comparison of machine learning techniques for reservoir outflow forecasting

Número especial: Advances in machine learning for natural hazards risk assessment[Abstract:] Reservoirs play a key role in many human societies due to their capability to manage water resources. In addition to their role in water supply and hydropower production, their ability to retain water and control the flow makes them a valuable asset for flood mitigation. This is a key function, since extreme events have increased in the last few decades as a result of climate change, and therefore, the application of mechanisms capable of mitigating flood damage will be key in the coming decades. Having a good estimation of the outflow of a reservoir can be an advantage for water management or early warning systems. When historical data are available, data-driven models have been proven a useful tool for different hydrological applications. In this sense, this study analyzes the efficiency of different machine learning techniques to predict reservoir outflow, namely multivariate linear regression (MLR) and three artificial neural networks: multilayer perceptron (MLP), nonlinear autoregressive exogenous (NARX) and long short-term memory (LSTM). These techniques were applied to forecast the outflow of eight water reservoirs of different characteristics located in the Miño River (northwest of Spain). In general, the results obtained showed that the proposed models provided a good estimation of the outflow of the reservoirs, improving the results obtained with classical approaches such as to consider reservoir outflow equal to that of the previous day. Among the different machine learning techniques analyzed, the NARX approach was the option that provided the best estimations on average.FEDER; 0034_RISC_ML_6_EXunta de Galicia; ED431C 2021/44Xunta de Galicia; ED481B-2021-108Universidade de Vigo; 0000 131H TAL 64

Multiscale flood risk assessment under climate change: the case of the Miño river in the city of Ourense, Spain

[Abstract:] River floods, which are one of the most dangerous natural hazards worldwide, have increased in intensity and frequency in recent decades as a result of climate change, and the future scenario is expected to be even worse. Therefore, their knowledge, predictability, and mitigation represent a key challenge for the scientific community in the coming decades, especially in those local areas that are most vulnerable to these extreme events. In this sense, a multiscale analysis is essential to obtain detailed maps of the future evolution of floods. In the multiscale analysis, the historical and future precipitation data from the CORDEX (Coordinated Regional Downscaling Experiment) project are used as input in a hydrological model (HEC-HMS) which, in turn, feeds a 2D hydraulic model (Iber+). This integration allows knowing the projected future changes in the flow pattern of the river, as well as analyzing the impact of floods in vulnerable areas through the flood hazard maps obtained with hydraulic simulations. The multiscale analysis is applied to the case of the Miño-Sil basin (NW Spain), specifically to the city of Ourense. The results show a delay in the flood season and an increase in the frequency and intensity of extreme river flows in the Miño-Sil basin, which will cause more situations of flooding in many areas frequented by pedestrians and in important infrastructure of the city of Ourense. In addition, an increase in water depths associated with future floods was also detected, confirming the trend for future floods to be not only more frequent but also more intense. Detailed maps of the future evolution of floods also provide key information to decision-makers to take effective measures in advance in those areas most vulnerable to flooding in the coming decades. Although the methodology presented is applied to a particular area, its strength lies in the fact that its implementation in other basins and cities is simple, also taking into account that all the models used are freely accessible.Xunta de Galicia; ED431C 2021/44FEDER; 0034_RISC_ML_6_EXunta de Galicia; ED481B-2021-10

IberWQ: A GPU Accelerated Tool for 2D Water Quality Modeling in Rivers and Estuaries

Este artigo inclúese no número especial "Modelling Flow, Water Quality, and Sediment Transport Processes in Coastal, Estuarine, and Inland Waters"[Abstract] Numerical models are useful tools to analyze water quality by computing the concentration of physical, chemical and biological parameters. The present work introduces a two-dimensional depth-averaged model that computes the most relevant and frequent parameters used to evaluate water quality. High performance computing (HPC) techniques based on graphic processing unit (GPU) parallelization have been applied to improve the efficiency of the package, providing speed-ups of two orders of magnitude in a standard PC. Several test cases were analyzed to show the capabilities and efficiency of the model to evaluate the environmental status of rivers and non-stratified estuaries. IberWQ will be freely available through the package Iber.European Commission; INTERREG-POCTEP; 0034_RISC_ML_6_EXunta de Galicia; ED431C 2017/64-GRCXunta de Galicia; ED481A-2017/31

An accelerated tool for flood modelling based on Iber

Este artigo inclúese no número especial "Selected Papers from the 1st International Electronic Conference on the Hydrological Cycle (ChyCle-2017)"[Abstract:] This paper presents Iber+, a new parallel code based on the numerical model Iber for two-dimensional (2D) flood inundation modelling. The new implementation, which is coded in C++ and takes advantage of the parallelization functionalities both on CPUs (central processing units) and GPUs (graphics processing units), was validated using different benchmark cases and compared, in terms of numerical output and computational efficiency, with other well-known hydraulic software packages. Depending on the complexity of the specific test case, the new parallel implementation can achieve speedups up to two orders of magnitude when compared with the standard version. The speedup is especially remarkable for the GPU parallelization that uses Nvidia CUDA (compute unified device architecture). The efficiency is as good as the one provided by some of the most popular hydraulic models. We also present the application of Iber+ to model an extreme flash flood that took place in the Spanish Pyrenees in October 2012. The new implementation was used to simulate 24 h of real time in roughly eight minutes of computing time, while the standard version needed more than 15 h. This huge improvement in computational efficiency opens up the possibility of using the code for real-time forecasting of flood events in early-warning systems, in order to help decision making under hazardous events that need a fast intervention to deploy countermeasures.Water JPI—WaterWorks Programme, project Improving Drought and Flood Early Warning, Forecasting and Mitigation, IMDROFLOOD; PCIN-2015-243European Commission; project RISC_ML 034_RISC_ML_6_EXunta de Galicia; ED431C 2017/64-GRCXunta de Galicia; ED481A-2017/314Xunta de Galicia; ED481B-2018/020European Commission; IMDROFLOOD PCIN-2015-24

Towards an automatic early warning system of flood hazards based on precipitation forecast: the case of the Miño River (NW Spain)

[Abstract:] An early warning system for flood prediction based on precipitation forecast is presented. The system uses rainfall forecast provided by MeteoGalicia in combination with a hydrologic (Hydrologic Modeling System, HEC-HMS) and a hydraulic (Iber+) model. The upper reach of the Miño River and the city of Lugo (NW Spain) are used as a study area. Starting from rainfall forecast, HEC-HMS calculates the streamflow and Iber+ is automatically executed for some previously defined risk areas when a certain threshold is exceeded. The analysis based on historical extreme events shows that the system can provide accurate results in less than 1 h for a forecast horizon of 3 d and report an alert situation to decision makers.We especially thank Carlos Ruiz del Portal Florido, Head of the Hydrological Planning Office, Hydrographic Confederation of Miño-Sil River for helpful discussions and for providing access to real data within the context of INTERREG-POCTEP Programme project RISC_ML (Code: 0034_RISC_ML_6_E). This work was partially supported by the Water JPI-WaterWorks Programme under project Improving Drought and Flood Early Warning, Forecasting and Mitigation (IMDROFLOOD, code: PCIN-2015-243) and by Xunta de Galicia under project ED431C 2017/64-GRC “Programa de Consolidación e Estructuración de Unidades de Investigación Competitivas (Grupos de Referencia Competitiva)”.European Regional Development Fund (ERDF); 0034_RISC_ML_6_EXunta de Galicia; ED431C 2017/64-GR

Coupling of an SPH-based solver with a multiphysics library

[Abstract:] A two-way coupling between the Smoothed Particle Hydrodynamics-based (SPH) code with a multiphysics library to solve complex fluid-solid interaction problems is proposed. This work provides full access to the package for the use of this coupling by releasing the source code, completed with guidelines for its compilation and utilization, and self-contained template setups for practical uses of the novel implemented features, is provided here. The presented coupling expands the applicability of two different solvers allowing to simulate fluids, multibody systems, collisions with frictional contacts using either non-smooth contact (NSC) or smooth contact (SMC) methods, all integrated under the same framework. The fluid solver is the open-source code DualSPHysics, highly optimised for simulating free-surface phenomena and structure interactions, uniquely positioned as a general-purpose Computational Fluid Dynamics (CFD) software with a GPU-accelerated solver. Mechanical systems that comprise collision detection and/or multibody dynamics are solved by the multiphysics library Project Chrono, which uses a Discrete Element Method (DEM). Therefore, this SPH-DEM coupling approach can manage interactions between fluid and complex multibody systems with relative constraints, springs, or mechanical joints.Funding for open access charge: Universidade de Vigo/CISUG, Spain. This work was supported by the project SURVIWEC PID2020-113245RB-I00 financed by MCIN/AEI/10.13039/501100011033 and by the project ED431C 2021/44 “Programa de Consolidación e Estructuración de Unidades de Investigación Competitivas” financed by Xunta de Galicia, Consellería de Cultura, Educación e Universidade. This study forms part of the Marine Science programme (ThinkInAzul) supported by Ministerio de Ciencia e Innovación and Xunta de Galicia with funding from European Union NextGenerationEU ( PRTR-C17.I1 ) and European Maritime and Fisheries Fund. I. Martínez-Estévez acknowledges funding from Xunta de Galicia under “Programa de axudas á etapa predoutoral da Consellería de Cultura, Educación e Universidades da Xunta de Galicia” ( ED481A-2021/337 ). O. García-Feal was funded by Spanish “Ministerio de Universidades” and European Union – NextGenerationEU through the “Margarita Salas” post-doctoral grant. The authors wish to acknowledge the support provided by the Project Chrono developers: Prof. Dan Negrut and Dr. Radu Serban (University of Wisconsin–Madison, US), and Prof. Alessandro Tasora (University of Parma, Italy). The list of authors of the DualSPHysics code is published on its website ( https://dual.sphysics.org/developers/ ) and the Copyright can be seen in the license file of the code ( https://github.com/DualSPHysics/DualSPHysics/blob/master/LICENSE ). The list of authors of the Project Chrono code is shown on its website ( https://projectchrono.org/about/ ) and its Copyright can be seen in the license file of the code ( https://github.com/projectchrono/chrono/blob/main/LICENSE ). DSPHChronoLib code has been developed by the following authors: I. Martínez-Estévez, J.M. Domínguez, R. Canelas, B. Tagliafierro, O. García-Feal, A.J.C. Crespo and M. Gómez-Gesteira; and its Copyright is available in DualSPHysics-Chrono/src_extra/DSPH-Chrono-Lib/LICENSE. DualSPHysics and DSPHChronoLib are released under the GNU Lesser General Public License (LGPL). Project Chrono is released under BSD-3-Clause License.Xunta de Galicia; ED431C 2021/44Xunta de Galicia; ED481A-2021/33

How to mitigate flood events similar to the 1979 catastrophic floods in the lower Tagus

[Abstract:] The floods that struck the lower Tagus valley in February 1979 correspond to the most intense floods in this river and affected the largest number of people in a river flow event in Portugal during the last 150 years. In fact, the vast area affected significantly impacted circa 10 000 people in the lower Tagus sector (and an additional 7000 in other regions of Portugal), including thousands of people evacuated or made homeless. In this context, the present study focuses on an in-depth analysis of this event from a hydrodynamic perspective by means of the Iber+ numerical model and on developing strategies to mitigate the flood episodes that occur in the lower section of the Tagus River using the exceptional floods of February 1979 as a benchmark. In this sense, dam operating strategies were developed and analyzed for the most important dam along the Tagus River basin in order to propose effective procedures to take advantage of these infrastructures to minimize the effect of floods. Overall, the numerical results indicate a good agreement with watermarks and some descriptions of the 1979 flood event, which demonstrates the model capability to evaluate floods in the area under study. Regarding flood mitigation, results obtained indicate that the frequency of floods can be reduced with the proposed strategies, which were focused on providing optimal dam operating rules to mitigate flooding in the lower Tagus valley. In addition, hydraulic simulations corroborated an important decrease in water depth and velocity for the most extreme flood events, and also a certain reduction in the flood extension was detected. This confirms the effectiveness of the proposed strategies to help in reducing the flood impact in the lower Tagus valley through the efficient functioning of dams.This research has been partially supported by Xunta de Galicia, Consellería de Cultura, Educación e Universidade, under project ED431C 2021/44 “Programa de Consolidación e Estructuración de Unidades de Investigación Competitivas”. This research has also been partially supported by the European Regional Development Fund under the Interreg POCTEP project RISC_PLUS (code: 0031_RISC_PLUS_6_E). This research has also been partially funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) – UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020), UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020). Diego Fernández-Nóvoa was supported by Xunta de Galicia through a post-doctoral grant (ED481B-2021-108). Alexandre M. Ramos was supported by the Helmholtz “Changing Earth – Sustaining our Future” program. Cristina Catita was supported by EEA Financial Mechanism 2014–2021 and the Portuguese Environment Agency through Pre-defined Project 2 National Roadmap for Adaptation XXI (PDP-2). Orlando García-Feal was funded by the Spanish Ministerio de Universidades and European Union – NextGenerationEU – through a Margarita Salas post-doctoral grant. Ricardo M. Trigo was supported by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES, through project AMOTHEC – DRI/India/0098/2020 (https://doi.org/10.54499/DRI/India/0098/2020).Xunta de Galicia; ED431C 2021/44Xunta de Galicia; ED481B-2021-108European Regional Development Fund (ERDF); 0031_RISC_PLUS_6_EPortugal. Fundação para a Ciência e a Tecnologia (FCT); UIDB/50019/2020Portugal. Fundação para a Ciência e a Tecnologia (FCT); UIDP/50019/2020Portugal. Fundação para a Ciência e a Tecnologia (FCT); LA/P/0068/2020Portugal. Fundação para a Ciência e a Tecnologia (FCT); DRI/India/0098/202

Benchmarking of the Iber Capabilities for 2D Free Surface Flow Modelling

CONTENTS: 1. Introduction; 2. Test 1: Flooding a disconnected water body; 3. Test 2: Filling of floodplain depressions; 4. Test 3: Momentum conservation over a small obstruction; 5. Test 4: Speed of flood propagation over an extended floodplain; 6. Test 5: Valley flooding; 7. Test 6: Dambreak; 8. Test 7: Rainfall and point source surface flow in urban areas; 9. Test 8: Overland flow in a four-branch junction; 10. Test 9: Rainfall-runoff in a three-slope 1D channel; 11. Test 10: Rainfall-runoff over a simplified V-shaped valley; 12. Test 11: Rainfall-runoff over a simplified urban configuration; 13. References.[Abstract] Iber is a software for simulating turbulent free surface unsteady flow and transport processes in shallow water flows. The hydrodynamic module of Iber solves the depth averaged two-dimensional shallow water equations (2D Saint-Venant Equations). This document presents the performance of the software Iber in a series of two-dimensional modelling benchmark tests. Some of these tests were developed by the United Kingdom Joint Defra / Environment Agency under Defra’s Flood and Coastal Erosion Risk Management R&D program, and have been used to benchmark other 2D free surface flow models, as the 2D version of HEC-RAS

Numerical simulation of the deadliest flood event of Portugal: Unravelling the causes of the disaster

The flood event of November 25 and 26, 1967 corresponds to the deadliest storm affecting Portugal in recent centuries being responsible for >500 fatalities. The main trigger was the heavy rain that fell in just a few hours, provoking a rapid increase in river flows, although other concurrent circumstances had to occur to reach the dramatic water levels estimated in some affected places. However, even today, several important uncertainties related to water levels achieved and timing of floods remain. Here we aim to clarify some of the pending issues by applying suitable high performance numerical tools to elucidate the main conditioning factors that played a key role in the intensification of this dramatic flood. In particular, the analysis has been focused on Quintas village, the location most affected, where >100 fatalities were recorded, close to 2/3 of its total population at the time. The main conclusion provided by the numerical simulations was that a plugging of water flow downstream of Quintas village, favoured by a poor terrain maintenance coupled with the bottleneck created by topographic features, caused the critical over-elevation of water levels. Simulations also corroborate the rapid increase in water levels in Quintas village, with an estimated rise of >2 m in just two hours, as well as the occurrence of the flood during the night, preventing many people to be aware of the extreme danger they were facing and safeguarding themselves.Universidade de Vigo/CISU