Application of Fractional Calculus to Frontal Crash Modeling

Fractional derivative viscoelastic model is used in the analysis of a frontal impact of a vehicle against a rigid obstacle. The frontal part of the vehicle is first modeled as a viscoelastic fractional rod and then it is modeled as two different viscoelastic fractional rods with a different length. In the second model also the friction is taken into account. A motion is analyzed during several phases because of both different lengths of the rods and the presence of a dry friction force in the later model. Governing systems of differential equations together with the corresponding initial conditions are derived. Parameter identification is done on the basis of the existing experimental results using the solution of a posed impact problem. What makes the problem more complex, regarding the second model, is the fact that it belongs to the class of nonsmooth fractional order systems, which require special treatment when dealing with deformation history during different motion phases

An investigation into the effects of complex topography on particle dry deposition

There is a requirement to predict the spatial variation of particle dry deposition following a nuclear accident. The interaction of landscape features, atmospheric flow and particle dry deposition has been investigated with this in mind. Wind tunnel studies have been used with computational fluid dynamics to predict the deposition rate relative to a flat landscape. Good quantitative agreement was seen for this relative deposition rate. Landscape shapes showed significant effects on deposition rate, increasing it by more than two in some cases, over limited areas. The effect of turbulence intensity, in the absence of landscape features, was also studied and a weak relationship to dry deposition was observed. Computational fluid dynamics methods used in wind tunnel comparisons were extended to a wide range of landscape cases. Deposition rates varied spatially around the landscape features. In general, for hills and ridges, deposition was seen to increase on the windward face, decrease on the leeward face and near wake, and increase in the further wake, before returning to the flat case value. The computational results were applied to a real landscape with the use of a customised geographical information system. Good general agreement was seen when compared with a test case

Аnalysis of energy dissipation in the impact problems of two or more bodies

Анализиран је судар два тела као и дисипација енергије укључена кроз механизам сувог трења моделираног неглатком вишевредносном функцијом и кроз деформацију вискоеластичног штапа чији модел укључује фракционе изводе. Проблем судара два тела је приказан у форми Кошијевог проблема који припада класи неглатких вишевредносних диференцијалних једначина произвољног реалног реда. Кошијев проблем је решен нумеричким поступком заснованим на Тарнеровом алгоритму. Испитано је кретање система и дисипација енергије за разне вредности улазних параметара. Показано је да се уведене методе могу применити и на проблем судара три тела.Analiziran je sudar dva tela kao i disipacija energije uključena kroz mehanizam suvog trenja modeliranog neglatkom viševrednosnom funkcijom i kroz deformaciju viskoelastičnog štapa čiji model uključuje frakcione izvode. Problem sudara dva tela je prikazan u formi Košijevog problema koji pripada klasi neglatkih viševrednosnih diferencijalnih jednačina proizvoljnog realnog reda. Košijev problem je rešen numeričkim postupkom zasnovanim na Tarnerovom algoritmu. Ispitano je kretanje sistema i disipacija energije za razne vrednosti ulaznih parametara. Pokazano je da se uvedene metode mogu primeniti i na problem sudara tri tela.Impact of two bodies was analyzed as well as energy dissipation, which was included through dry friction phenomena modelled by a set-valued function, and through deformation of a viscoelastic rod modelled by fractional derivatives. The impact problem was presented in the form of the Cauchy problem that belongs to a class of set-valued fractional differential equations. The Cauchy problem was solved by the numerical procedure based on Turner’s algorithm. Behaviour and energy dissipation of the system was investigated for different values of input parameters. It was shown that suggested procedure can be applied on the problem of impact of three bodies

Modelling scour around submerged objects with TELEMAC3D - GAIA

Hydrodynamic

Online proceedings of the papers submitted to the 2020 TELEMAC-MASCARET User Conference October 2020

Hydrodynamic

Development of Large-Scale Unstructured Grid Storm Surge and Sub-Grid Inundation Models for Coastal Applications

Storm surge and inundation induced by hurricanes and nor\u27easters pose a profound threat to coastal communities and ecosystems. These storm events with powerful winds, heavy precipitation, and strong wind waves can lead to major flooding for cities along U.S. Coasts. Recent examples of Hurricane Irene (2011) in North Carolina and Virginia and Hurricane Sandy (2012) in New York City not only demonstrated the immense destructive power by the storms, but also revealed the obvious, crucial need for improved forecasting of storm tide and inundation. in part I, a large-scale unstructured-grid 3-D barotropic storm tide model SCHISM (Semi-implicit Cross-scale Hydroscience Integrated System Model) is developed with open ocean boundary aligning along the 60-degree West longitude to catch most Atlantic hurricanes that may make landfall along U.S. East and Gulf Coasts. The model, driven by high-resolution NAM (North America Mesoscale) and ECMWF (European Centre for Medium-Range Weather Forecasts) atmospheric fields, was coupled with Wind Wave Model (WWMIII) to account for wave effects, and used to simulate storm surge in 3-D barotropic mode rather than the traditional 2-D vertical average mode. For Hurricane Sandy, the fully coupled wave-current interaction 3-D model using ECMWF atmospheric forcing performs the best. The storm tide results match well with observation at all nine NOAA tidal gauges along the East Coast. The maximum total water level in New York City, is accurately simulated with absolute error of amplitude less than 8 cm, and timing difference within 10 minutes. The scenarios of 2-D versus 3-D and with versus without wind wave model were compared and discussed in details. Overall, the wave contribution amounts to 5-10% of surge elevation during the event. Also, the large-scale model with similar setup is applied to hindcasting storm tide during Hurricane Irene and the results are excellent when compared with observed water level along Southeast Coast and inside Chesapeake Bay. in part II, a high-resolution sub-grid inundation model ELCIRC-sub (Eulerian-Lagrangian CIRCulation) was developed from the original finite-volume-based ELCIRC model. It utilized the sub-grid method for imbedding high-resolution topography/bathymetry data into the traditional model grid and delivering the inundation simulation on the street level scale. The ELCIRC-sub contains an efficient non-linear solver to increase the accuracy and was executed in the MPI (Message Passing Interface) parallel computing platform to vastly enlarge the water shed coverage, and to expand the numbers of sub-grids allowed. The ELCIRC-sub is first validated with a wetting/drying analytic solution and then applied in New York City for Hurricane Sandy (2012). Temporal comparisons with NOAA and USGS water level gauges showed excellent performance with an average error on the order of 10 cm. It accurately captured the highest surge (during Hurricane Sandy) at Kings Point on both maximum surge height and the explosive surge profile. Spatial comparisons of the modeled peak water level at 80 locations around New York City showed an average error less than 13 cm. The modeled maximum modeled inundation extent also matched well with 80% of the FEMA flooding map. in terms of robustness and efficiency for practical application, ELCIRC-sub surpasses the prototype model UnTRIM2

Proceedings of the XXVIIIth TELEMAC User Conference 18-19 October 2022

Hydrodynamic

Geschachtelte Modellierung von Wellenprozessen vom tiefen zum seichten Wasser: Aufbau eines operationellen Wellenmodellsystems

In this thesis, a model system for simulating the wave processes from the open ocean to the shoreline is proposed. In particular, the focus is put on modelling extreme wave conditions in the Mediterranean Sea and the aim is to develop a supporting tool for decision making in the early-warning process. This aim is motivated by the high number of damages due to extreme high waves conditions which occur worldwide every year. Moreover, the increasing population density and climate change in coastal zones enhance the risk for human life and coastal activities in the next future. The model system is built by linking three existing models, properly selected for their ability of simulating physical In particular, the WAVEWATCH~III model is selected for the wave processes in deep water, the SWAN model for wave processes in intermediate/shallow water, and the XBeach model for wave processing in the nearshore where changes of seabed will affect wave propagation. The three models are nested by adopting a modular approach, in which each model works separately, and a new module is developed in order to transfer the initial and boundary conditions from the largest scale to the smallest scale of the model chain. The advantage of the modular approach is that no or only slight modifications of the source code of the existing models are needed. Moreover, the system can be easily updated by introducing improvements/extensions, or fully new versions of the single models without modification of the structure of the system. The developed model system, called NEMO system, is calibrated and validated, and applied to a real test case in the coast of Versilia (North Tuscany, Italy).In dieser Doktorarbeit ist ein Modellsystem zur Simulation der Wellenprozesse vom offenen Ozean bis zur Küstenlinie entwickelt worden. Insbesondere liegt der Schwerpunkt dieser Studie auf der Modellierung extremer Wellenereignisse, welche durch extreme Sturmereignisse im Mittelmeer erzeugt werden. Das Ziel ist es ein Frühwarnsystem zu entwickeln, welches bei der Entscheidungsfindung über Küstenschutzmaßnahmen, auch im Katastrophenfall, unterstützen kann. Diese Arbeit ist durch die hohe Anzahl und die Größe der weltweiten Schäden in Küstengebieten, welche jedes Jahr als Folge von extremen Wellenereignisse auftreten, motiviert worden. Darüber hinaus erhöht sich in der nahen Zukunft das Risiko für die zunehmende Bevölkerung, welche in den Küstengebieten lebt und arbeitet, durch den Klimawandel, welcher zu einer Zunahme von Schlechtwetterereignissen führt. Das Modellsystem besteht aus der Verknüpfung von drei vorhandenen Modellen. Jedes Modell ist entsprechend seiner Fähigkeiten ausgewählt worden, um die Gesamtheit der physikalische Prozesse zu simulieren, welche die räumliche und zeitliche Verteilung der Wellen beeinflusst. Insbesondere sind das WAVEWATCH III-Modell für die Wellenprozesse in tiefem Wasser, das SWAN-Modell für Wellenprozesse in intermediärem / seichtem Wasser und das XBeach-Modell für Wellenprozesse im Küstenbereich, wo Veränderungen des Meeresbodens die Wellenausbreitung beeinflussen, ausgewählt worden. Die drei Modelle werden verschachtelt, indem ein modularer Ansatz gewählt wird, bei dem jedes Modell separat arbeitet und ein neues Modul entwickelt, um die Anfangs- und Randbedingungen vom größten Maßstab auf den kleinsten Maßstab der Modellkette zu übertragen. Der Vorteil des modularen Ansatzes besteht darin, dass keine oder nur geringfügige Modifikationen des Quellcodes der vorhandenen Modelle erforderlich sind. Darüber hinaus kann das System leicht aktualisiert werden, indem Verbesserungen / Erweiterungen oder vollständig neue Versionen der einzelnen Modelle einfach eingeführt werden, ohne die Struktur des Systems zu verändern. Das entwickelte Modellsystem, welches NEMO-System genannt wird, ist auf einen realen Testfall an der Küste der Versilia (Nordtoskana, Italien) kalibriert und validiert und angewendet worden