SERGHEI (SERGHEI-SWE) v1.0: a performance-portable high-performance parallel-computing shallow-water solver for hydrology and environmental hydraulics

The Simulation EnviRonment for Geomorphology, Hydrodynamics, and Ecohydrology in Integrated form (SERGHEI) is a multi-dimensional, multi-domain, and multi-physics model framework for environmental and landscape simulation, designed with an outlook towards Earth system modelling. At the core of SERGHEI's innovation is its performance-portable high-performance parallel-computing (HPC) implementation, built from scratch on the Kokkos portability layer, allowing SERGHEI to be deployed, in a performance-portable fashion, in graphics processing unit (GPU)-based heterogeneous systems. In this work, we explore combinations of MPI and Kokkos using OpenMP and CUDA backends. In this contribution, we introduce the SERGHEI model framework and present with detail its first operational module for solving shallow-water equations (SERGHEI-SWE) and its HPC implementation. This module is designed to be applicable to hydrological and environmental problems including flooding and runoff generation, with an outlook towards Earth system modelling. Its applicability is demonstrated by testing several well-known benchmarks and large-scale problems, for which SERGHEI-SWE achieves excellent results for the different types of shallow-water problems. Finally, SERGHEI-SWE scalability and performance portability is demonstrated and evaluated on several TOP500 HPC systems, with very good scaling in the range of over 20 000 CPUs and up to 256 state-of-the art GPUs

Effective Computation Resilience in High Performance and Distributed Environments

The work described in this paper aims at effective computation resilience for complex simulations in high performance and distributed environments. Computation resilience is a complicated and delicate area; it deals with many types of simulation cores, many types of data on various input levels and also with many types of end-users, which have different requirements and expectations. Predictions about system and computation behaviors must be done based on deep knowledge about underlying infrastructures, and simulations' mathematical and realization backgrounds. Our conceptual framework is intended to allow independent collaborations between domain experts as end-users and providers of the computational power by taking on all of the deployment troubles arising within a given computing environment. The goal of our work is to provide a generalized approach for effective scalable usage of the computing power and to help domain-experts, so that they could concentrate more intensive on their domain solutions without the need of investing efforts in learning and adapting to the new IT backbone technologies

Urban food simulation by coupling a hydrodynamic model with a hydrological model

PhD ThesisThis work introduces a new integrated flood modelling tool in urban areas by coupling a hydrodynamic model with a hydrological model in order to overcome the drawbacks of each individual modelling approach, i.e. high computational costs usually associated with hydrodynamic models and less detailed physical representations of the underlying flow processes corresponding to hydrological models. Crucial to the simulation process is to first divide the catchment hydraulic and hydrological zones where the corresponding model is then applied. In the hydrological zones that have more homogeneous land cover and relatively simple topography, a conceptual lumped model is applied to obtain the surface runoff, which is then routed by a group of pre-acquired ‘unit hydrographs’ to the zone border, for high-resolution flood routing in the hydraulic zones with complex topographic features, including roads, buildings, etc. In hydraulic zones, a full 2D hydrodynamic model is applied to provide more detailed flooding information e.g. water depth, flow velocity and arrival time. The new integrated flood modelling tool is validated in Morpeth, the North East of England by reproducing the September 2008 flood event during which the town was severely inundated following an intense rainfall event. Moreover, the coupled model is investigated and evaluated according to the effects from temporal and spatial resolutions, friction, rainfall, infiltration, buildings and coupling methods. In addition, the model is also employed to implement flood damage estimations with different scenarios of the upstream storage and flood defences in the town centre. Whilst producing similar accuracy, the new model is shown to be much more efficient compared with the hydrodynamic model depending on the hydrological zone percentage. These encouraging results indicate that the new modelling tool could be robust and efficient for practitioners to perform flood modelling, damage estimation, risk assessment and flood management in urban areas and large-scale catchments.financial sponsorship of ‘The School of Civil Engineering and Geosciences’ and ‘The Chinese Scholarship Council’ for the first three years. Then for the fourth year of my PhD study ‘The Henry Lester Trust Limited’ and ‘The Great Britain-China Educational Trust

High performance computing for modelling of stereolithography process

In this dissertation, a state-of-the-art 3D computational model has been developed for Stereolithography process to investigate the evolution of properties in a multi-physics framework using Stabilized Optimal Transportation Meshfree (OTM) method based on a continuum approach. In order to accelerate the computational performance, HPC framework of the OTM method has been developed. Stereolithography process is a complex process in the sense that several physical processes are involved therein. In this work, some of the key phenomena incorporated in the modeling framework are highly coupled thermo-chemo-mechanical evolution of resin properties and propagation of the UV laser through the resin. The photopolymerization is driven by the interaction of fluid resin with the UV light and consequently generates heat due to its exothermic nature and resulting in building up of mechanical stresses. The numerical and geometrical complexities arising from these phenomena pose serious challenges and complications in grid-based techniques such as Finite element (FE). Generally, such issues are referred to as mesh distortion. OTM based computational modeling is one solution to these issues. The method is quite new in the field of Stereolithography simulation and it is efficient in capturing the deformations generated during printing process. Moreover, parallelization using MPI with an objective for scalability on large scale CPU clusters reduces the computational efforts. And, the obtained results leads to highly scalable results. The developed tool can be employed to optimize the material and process parameters during the printing process to achieve improved accuracy in the printed parts

Shallow Water Equations in Hydraulics: Modeling, Numerics and Applications

This Special Issue aims to provide a forum for the latest advances in hydraulic modeling based on the use of shallow water and related models as well as their novel application in practical engineering. Original contributions, including those in but not limited to the following areas, will be considered for publication: new conceptual models and applications, flood inundation and routing, sediment transport and morphodynamic modelling, pollutant transport in water, irrigation and drainage modeling, numerical simulation in hydraulics, novel numerical methods for the shallow water equations and extended models, case studies, and high-performance computing

Developing a multi-scale parallelised coupled system for wave-current interactions at regional scales

At coastal areas, the interplay between waves and currents is crucial. This interaction impacts many phenomena and applications, highlighting the necessity for accuracy and speed in the numerical representation of Wave-Current Interactions (WCI). These applications encompass a wide spectrum, including coastal morphology, sediment transport, offshore structure scouring, pollutant mixing, infrastructure design, marine energy projects, and storm surges. The complexity in representing WCI stems from incorporating multi-scale processes with diverse temporal and spatial scales. For example, wind wave periods range from seconds to hours, while the wavelengths span from centimetres to kilometres. In contrast, tides showcase much larger scales with periods in the order of hours and wave-lengths in the order of thousands of kilometres. Practically, reconciling all these processes and scales within a single model is improbable, leading to the need for coupled systems to address this challenge. This study presents the development of a Python-interfaced multi-scale parallelised coupled modelling system for WCI. It is formed by coupling the spectral wave model Simulat ing WAves Nearshore (SWAN) with the 2-D shallow-water equation hydrodynamics model Thetis. The coupling is facilitated by the Basic Model Interface (BMI), a lightweight generic coupling interface. The impact of waves on current is introduced via the radiation stress formulation, accompanied by the integration of wave-roller effects. Two coupling options are offered: online and offline. The online choice supports both one-way and two-way coupling, while the offline alternative is focused on one-way coupling. Considering that only few existing WCI models report on validation in controlled environments, a suite of benchmarking scenarios is established consisting of analytical and experimental scenarios in quasi 1-D and 2-D configurations. In these cases, sensitivity analyses are performed spanning various parameters in both models. The results underscore the importance of customising each coupled configuration when WCI are prominent, rather than solely relying on recommended or “default” values. Calibrated results align well with the data and often showcase the same level of accuracy as other 3-D WCI. This efficiency means less computational cost, as the developed model converges faster and requires less CPU time compared to alternative options. A month-long numerical representation of the field configuration located in Duck, North Carolina, investigates the coupled system’s performance under moderate wind conditions. This scenario serves to assess the influence of various coupling approaches on its predictions. Since this area is primarily influenced by waves and features low current speeds, the coupling modes have minor impact on wave predictions. However, with coupling modes transitioning from no to two-way coupling, the hydrodynamics predictions exhibit substantial improvement in regions where WCI are evident. The improved accuracy does not encompass areas characterised by rip currents or other processes that require a vertical discretisation for their hydrodynamics. Discrepancies between online and offline one-way coupling configurations are evident, with the most pronounced differences observed in the SWAN-to-Thetis coupling. They can be attributed to different interpolation methodologies. Ultimately, the WCI system is applied in a regional configuration within the Orkney archipelagos, UK. Specifically, the model simulates the waters of Westray Firth, a region known for its energetic tidal conditions, to assess its capacity for effectively depicting WCI phenomena in regional scales. Our predictions correlate well with the observations, accurately mirroring the sinusoidal pattern of the measured wave parameters, usually attributed to tidal effects. Furthermore, our model showcases similar precision to a 3-D WCI coupled system implemented in the same region at lower computational cost. The coupled system developed during this thesis presents an efficient tool for incorporating WCI phenomena across various scales, exhibiting performance comparable to its 3-D counterparts. Its efficiency is highlighted by: (a) minimising computational resource usage, as evidenced by a 38% reduction in the number of cores employed during the Westray Firth application; (b) reducing elapsed real times; and (c) accelerating convergence, such as achieving convergence 1.4 to 18 times faster in benchmarking scenarios. It provides a crucial foundation for researchers and stakeholders that seek to adopt a precise and efficient solution, independent of the 3-D nature of WCI. This unlocks new opportunities for its versatile employment in a range of applications spanning from initial research and decision-making stages to optimisation studies and to the development of forecasting systems

RiverFlow2D numerical simulation of flood mitigation solutions in the Ebro River

[EN] A study of measures oriented to flood mitigation in the mid reach of the Ebro river is presented: elimination of vegetation in the riverbed, use of controlled flooding areas and construction or re-adaptation of levees. The software used is RiverFlow2D which solves the conservative free-surface flow equations with a finite volume method running on GPU. The results are compared with measurements at gauge stations and aerial views. The most effective measure has turned out to be the elimination of vegetation in the riverbed. It is demonstrated that not only the maximum flooded area is narrower but also it reduces the water depth up to 1 m. The other measures have local consequences when the peak discharge is relatively high although they could be useful in case the discharge is lower[ES] En este trabajo se presenta un estudio de medidas orientadas a la mitigación de avenidas en el tramo medio del río Ebro: limpieza de vegetación del cauce, uso de zonas de inundación controlada y construcción o re-adaptación de motas. Para ello se utiliza el software RiverFlow2D que resuelve las ecuaciones conservativas del flujo de superficie libre con un método de volúmenes finitos realizando los cálculos sobre GPU. Se comparan los resultados con medidas en estaciones de aforo e información extraída de ortofotos. La medida más efectiva, de las analizadas, ha resultado ser la eliminación de la vegetación en el cauce. Se demuestra que no sólo el área máxima inundada es menor en todo el tramo sino que también reduce la altura de agua hasta en 1 m. El resto de medidas tienen consecuencias locales y de poca entidad cuando los caudales pico son altos, aunque podrían resultar de utilidad para avenidas con caudales más bajos.Este trabajo se encuentra en el marco del proyecto de investigación CGL2015-66114-R financiado por el Ministerio de Ciencia e Innovación/FEDER. Los autores quieren agradecer también a la Confederación Hidrográfica del Ebro por su disponibilidad de consulta y gestión de datos.Echeverribar, I.; Morales-Hernández, M.; Lacasta, A.; Brufrau, P.; García-Navarro, P. (2017). Simulación numérica con RiverFlow2D de posibles soluciones de mitigación de avenidas en el tramo medio del río Ebro. Ingeniería del Agua. 21(1):53-70. https://doi.org/10.4995/ia.2017.6550SWORD5370211Ahmad, S., Simonovic, S. 2006. An intelligent decision support system for management of floods. Water Resources Management, 20(3), 391-410. doi:10.1007/s11269-006-0326-3Ahmadian, R., Falconer, R. A., Wicks, J. 2015. Benchmarking of flood inundation extent using various dynamically linked one- and two-dimensional approaches. Journal of Flood Risk Management, 1-15. doi:10.1111/jfr3.12208Bates, P. D., De Roo, A. P. J. 2000. A simple raster-based model for flood inundation simulation. Journal of Hydrology, 236(1-2), 54-77. doi:10.1016/S0022-1694(00)00278-XBladé, E., Cea, L., Corestein, G., Escolano, E., Puertas, J., Vázquez-cendón, E., Dolz, J., Coll, A. 2014. Iber: herramienta de simulación numérica del flujo en ríos. Revista internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería, 30(1), 1-10. doi:10.1016/j.rimni.2012.07.004Brufau, P., García-Navarro, P. 2001. Modelo de simulación bidimensional de transitorios en aguas superficiales: aplicación a roturas de presa. Ingeniería Civil, 121, 33-40.Caviedes-Voullième, D., Morales-Hernández, M., López-Marijuan, I., García-Navarro, P. 2014. Reconstruction of 2D river beds by appropriate interpolation of 1D cross-sectional information for flood simulation. Environmental modelling & software, 61, 206-228. doi:10.1016/j.envsoft.2014.07.016Comisión Técnica del Comité Español de la Estrategia Internacional para la Reducción de Desastres, Dirección general de protección civil y emergencias, Ministerio del interior, Gobierno de España. Reducción del riesgo de desastres, nº 3 enero-abril 2016. http://www.proteccioncivil.org.DHI. 2009. MIKE 21 Flow Model. Hydrodynamic Module Scientific Documentation. MIKE by DHI, 2009.García, R., Restrepo, P., Deweese, M., Ziemer, M., Palmer, J., Thornburg, J., Murillo, J., Morales, M., García-Navarro, P., Lacasta, A. 2015. Advanced GPU Parallelization for two-dimensional operational river flood forecasting. Proceedings of the 36th IAHR World Congress, Junio 28-Julio 3. The Hague, The Netherlands.Lacasta, A., Morales-Hernández, M., Murillo, J., García-Navarro, P. 2014. An optimized GPU implementation of a 2D free surface simulation model on unstructured meshes. Advances in engineering software, 78, 1-15. doi:10.1016/j.advengsoft.2014.08.007Lacasta, A., Juez, C., Murillo, J., García-Navarro, P. 2015. An efficient solution for hazardous geophysical flows simulation using GPUs. Computers & Geosciences, 78, 63-72. doi:10.1016/j.cageo.2015.02.010Morales-Hernández, M., García-Navarro, P., Burguete, J., Brufau, P. 2013. A conservative strategy to couple 1D and 2D models for shallow water flow simulation. Computers & Fluids, 81, 26-44. doi:10.1016/j.compfluid.2013.04.001Murillo, J., Brufau, P., García-Navarro, P., Rodríguez, M., Andrés-Urrutia, A. 2007. A mathematical model for numerical simulation of shallow water flow: description and practical application of Guad2D. Proceedings of the Environmental Informatics and System Research Congress (Enviroinfo 2007), September 12-14, Warsaw, Poland, 409-416.Plan de Gestión del Riesgo de Inundación, Confederación Hidrográfica del Ebro. http://www.chebro.es/PGRI. Último acceso: enero 2017.Roe, P. L. 1981. Approximate Riemann solvers, parameter vectors and difference schemes. Journal of Computational Physics, 43(2), 357-372. doi:10.1016/0021-9991(81)90128-5Shang, Z. 2014. High performance computing for flood simulation using Telemac based on hybrid MPI/OpenMp parallel programming. International Journal of modeling, simulation and scientific computing, 5(4), 1-13.Suman, A., Akther, F. 2014. River Flood Modelling Using SOBEK: A Case Study from Ciliwung Catchment, Indonesia. International Journal of Engineering Research, 3(11), 662- 668. doi:10.17950/ijer/v3s11/1108Toriman, M.E., Hassan, A.J., Gazim, M.B., Mokhtar, M., Mastura, S.A., Jaafar, O., Karim, O., Aziz, N.A. 2009. Integration of 1-d Hydrodynamic Model and GIS Approach in Flood Management Study in Malaysia. Research Journal of Earth Sciences, 1(1), 22-27.Van der Knijff, J.M., Younis, J., De Roo, A.P.J. 2010. LISFLOOD: a GIS-based distributed model for river basin scale water balance and flood simulation. International Journal of Geographical Information Science, 24(2), 189-212. doi:10.1080/1365881080254915

Optimisation of tidal range schemes

Marine renewable energy, including tidal renewable energy, is one of the less exploited renewable energy sources that could contribute to energy demand while reducing greenhouse gas emissions. Several proposals to build tidal range structures, e.g. Swansea Bay Lagoon (SBL), have not received support from the UK government due to the high electricity costs or uncertainty about the environmental impacts. This makes the optimisation of such schemes particularly important for the future. The aim of this research was to optimise the design and operational characteristics of Tidal Range Schemes (TRSs) to make them more economically attractive by maximising the energy generation, or a flexible energy output to achieve multi-objectives. The study has focused on two key issues of TRSs optimisation. Firstly, the majority of studies before adopted the traditional non-flexible operation scenarios for electricity generation. In this approach, the operation heads were fixed throughout the operation simulations. It ignores the variability of tidal range over time and the fact that the operation of each generation phase affects the water levels inside the basin which in turn impact the electricity generation of the next phase. Secondly, the flexibility of energy output provided by renewable energies including tidal energy was underexploited, but it is regarded as one of the most important parts of the UK’s energy mix. Hence, the first objective was to propose and optimise flexible operation schemes to maximise energy generation. To achieve this, optimisation approaches were considered by breaking the operation into small components to optimise the operation of TRSs using a widely used 0-D modelling methodology. The optimisation outcomes were verified by a 2-D unstructured model under the same conditions. The flexibility of operation could at least increase generated electricity by 10% compared to the traditional non-flexible head operation. This increase was further improved by at least 10% when pumping was included. Meanwhile, a Genetic Algorithm (GA) method used for flexible operation optimisation was able to achieve the same amount of electricity generation compared to using a Grid Search (GS) method. However, the GA model could save approximately 50% of the computational cost, and it could be 95% in the optimisation of multiple variables, e.g. design parameter combining with flexible operation. Additionally, the optimisation using GA was used in designing of the two of the biggest lagoons proposed in the UK, namely West Somerset Lagoon and North Wales Tidal Lagoon, with the energy generation of 5.57 TWh/Year and 4.81 TWh/Year, respectively. The second objective in this study was to achieve the flexible energy output optimisation, including utilising generation flexibility from multilagoons to help match the continuous trends of energy output. The flexible operation optimisation was proved to facilitate better utilisation of renewable energy through the development of TRSs for multiobjective decision making