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This research adopted CMCOT model (Cornell Multi-grid Coupled Tsunami Model) to simulate the wave ran up as the tsunami entered the shoaling water of coastlines, the inundation range on land, and the bridge scour caused by tsunami as it made its way upstream in the rivers. The inundation range was estimated with the fault parameters of Manila Trench and a simulation of bell-sphaped curve waves. The result indicated that if the height of bell-sphaped curve was the same as the maximum water level of the tsunami passed to Kaohsiung offshore, the inundation rage was generally consistent. In the simulation of different water level, we discovered that one meter of wave height was sufficient to inundate the entire coastland of Qijin and Gushan District and that the inundation rage would expand as the wave height increased. With the maximum simulated wave height of six meters, the inundation rage included Gushan, Qijin, Yancheng, Qianjin (small scope), Qianzhen, Fengshan, and Xiaogang District. As to the comparison of historical tsunami, according to the particle size analysis of geological survey from the Kaohsiung Mass Rapid Transit, a layer of fine sediment could be found at specific depth, and its particle size (about 8£r) was significantly different than that of other layers. If this fine sediment was the border of tsunami sediment, the height of historical tsunami wave could be 4.9 meters. With regard to bridge scour, Gwando Bridge was chosen as research area. The result from the sediment simulation of COMCOT model was similar to the scour hole and sediment deposition formed by horseshoe vortex system. Based on the result, the scouring and depositing processes were mainly influenced by the particle size of the sediment. In the simulation, the results of different sediment particle sizes were as follows: (1) If the particle size of sediment was greater than 62£gm, the maximum scour depth was less than 4 cm, and the maximum height of deposition was under 3 cm. (2) If the particle size of sediment was between 4 and 62£gm, the maximum scour depth was between 4 and 5 cm, and the maximum height of deposition was between 3 and 4 cm. (3) If the particle size of sediment was smaller than 4£gm, the maximum scour depth was above 6.8 cm, and the maximum height of deposition was greater than 5 cm.

The aim of this study is to compare observational data to data simulated by a one dimensional model. Observational data collected from January to July 2006 at Lake Whitney, Texas, included water current velocities from an Acoustic Doppler Current Profiler, and an Acoustic Doppler Velocimeter from which shear stress, turbulent kinetic energy dissipation rates, and turbulence kinetic energy were computed using several methods. Numerical model experiments, forced by the surface heat and momentum fluxes, velocity profiles, and temperature profiles were conducted to simulate the development of the turbulence parameters. Two equation models, k-epsilon and k-kl, were used to find which model best describes the observed physical processes (turbulence kinetic energy, turbulent kinetic energy dissipation rate and velocity variances). The combined observational and simulated results show a change in stratification levels that consequently leads to variations in turbulent kinetic energy dissipation rate, turbulent kinetic energy, and the velocity variances. In order to investigate the accuracy of the model, we quantitatively compared these parameters to estimates from the observed data in the bottom boundary layer. In general, the model and observational data agree well for the three parameters, with the exception of some time periods, during which the model prediction differed from the observed. This was at times when the Acoustic Doppler Velocimeter measurements were at the noise level of the instrument. Overall, the k-kl model simulation results appear to be closer to the observational results during the weakly and strongly stratified periods than the k-epsilon model.

As world population increases, coastal areas experience an increase in human occupancy. These community locations come with a greater risk of impacts due to extreme natural events. Tsunami, being one of the most unpredictable and most devastating types of extreme hydrodynamic events, received significant attention over the past decades due to the recent extreme events (2004 Indian Ocean, 2010 Chile, 2011 Japan, 2018 Indonesia). The focus of this thesis is on investigating scour around structures generated by tsunami. Scouring was found to be one of the greatest sources of building damage during the 2011 Tohoku Japan Tsunami and, at the date of the redaction of this thesis, this phenomenon is still little understood by the scientific community. The main objective of this thesis is to study the change in scouring when multiple buildings are constructed in close proximity, as opposed to individual elements such as in the case of all previous studies focussed on tsunami-induced scour. This topic was first investigated by the candidate with the use of a numerical model, FLOW-3D, using the large eddy simulation approach and the Nielsen (1992) bed load sediment transport model. The model results showed a significant increase in scouring when a second building was located along the same transversal plane as the building investigated. Then, three structure arrangements were investigated in a comprehensive physical experiment conducted in the new Dambreak Flume of Hydraulic Laboratory of the University of Ottawa, Canada, to study the effects of (1) upstream constriction, (2) lateral spacing and (3) sheltering on tsunami-induced scour. All three structure arrangements showed a significant effect on tsunami-induced scour. A secondary project was conducted in collaboration with the Technical University of Braunschweig, Germany, and the Leibniz University Hannover, Germany. This large-scale physical experiment, performed in the Large Wave Flume of the Leibniz Institute Hannover, Germany, was used to investigate three different research phenomenon that influence tsunami scouring: (1) the wave drawdown on scour around structures, (2) the evolution of flow eddies and (3) the change in the soil’s pore pressure.

yes / The accurate prediction of the dilution and motion of the produced denser water (e.g. discharge of concentrated brine generated during solution mining and desalination) is of importance for environmental protection. Boundary conditions and ambient stratification can significantly affect the dilution and motion of gravity currents. In this study, a multiphase model is applied to simulate the gravity current descending a slope into a linearly stratified ambient. The k- turbulence model is used to better simulate the near bed motion. The mathematical model, initial and boundary conditions and the details of the numerical scheme are described. The time-dependent evolution of the gravity current, the flow thickness and the velocity and density field are simulated for a range of flow parameters. Simulations show that the Kelvin–Helmholtz billows are generated at the top of trailing fluid by the interfacial velocity shear. The K-H type instability becomes weaker with the slope distance from the source due to the decrease of the interfacial velocity shear along slope. The ambient stratification restricts and decreases the current head velocity as it descends slope, which differs from the situation in homogenous ambient while the head velocity remains an approximately steady state. Motion of the descending flow into the stratified ambient has two stages: initial acceleration and deceleration at later stage based on the balance of inertial, buoyancy and friction forces. When the descending current approaches the initial neutral position at later stage, it separates from the slope and spreads horizontally into environment. The simulated results, such as vertical velocity and density profiles and front positions, agree well with the measurements, indicating that the mathematical model can be successfully applied to simulate the effect of the boundary condition and ambient stratification on the dilution and propagation of gravity currents. / UK EPSRC

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Various numerical modelling software packages are available for predicting moored ship motions and forces. The focus of this study was to validate the numerical models QUAYSIM and WAVESCAT and how these models together form a procedure for predicting moored ship motions and forces under the impact of high and low frequency waves. The validation procedure applied in the study involved numerical modelling of a given physical model situation in which moored ship motions and forces were measured under both high and low frequency wave conditions. A physical model with built-in bathymetry was provided by the Council for Scientific and Industrial Research (CSIR) Hydraulics Laboratory in Stellenbosch. The model consisted of a moored container vessel at a jetty, with various mooring lines and fenders. A JONSWAP spectrum, which combines high and low frequency wave components, was used to simulate wave conditions for the modelling of ship motions. The wave periods and wave heights were measured at observation stations located at specific points in the basin. Other measurements such as those of the forces in the fenders and mooring lines were also determined. A multi-step approach was used to numerically predict the ship motions and forces. Firstly, the coastal processes occurring within the basin, which was set up to simulate the physical model wave behaviour, were measured to calibrate the SWAN Delft3D-WAVE model. The wave heights and periods for the respective observation stations were obtained and compared to the physical model measurements. The Delft3D-FLOW SURFBEAT model was used to calculate the low frequency waves in the coastal area. Low frequency waves are the main cause of larger ship motions and forces, therefore it is important to investigate them as part of the ship motion prediction procedure. After the waves had been computed, wave forces acting on the vessel needed to be determined for both high and low frequency waves. These wave forces were modelled with the combinations SURFBEAT/LF-STRIP (low frequency waves) and SWAN/WAVESCAT (high frequency waves). LF-STRIP provided the link between low frequency wave models and ship motion models, converting the low frequency waves into long wave forces acting on the vessel. WAVESCAT converted the high frequency waves to short wave forces. The calculated long wave forces and short wave forces served as the input required to run the ship motion model QUAYSIM to determine the movements of the moored ship as well as the restraining forces in the lines and fenders. The ship motions and forces were compared to the physical model, with the intention of possibly validating the QUAYSIM/WAVESCAT approach for predicting moored ship motions. The study provides an overview of both the setup and results of the physical and numerical model. A description of each of the numerical models SWAN, SURFBEAT, LF-STRIP, WAVESCAT and QUAYSIM is provided, along with a comparison between the physical and numerical models for each procedure. The validation procedure provided useful documentation of the quality of these numerical modelling approaches, already in use in some design projects. The numerical models WAVESCAT and QUAYSIM models of ship motion have shown to provide a good correlation between the physical model and the numerical approach. However, improvements are still required. Good comparisons were obtained for the long wave motions (horizontal movements - surge, sway and yaw). The surge and sway motions were slightly overestimated by QUAYSIM. The magnitude of the yaw was comparable but the not well represented in spectral plots. / AFRIKAANSE OPSOMMING: Daar is verskeie numeriese modellering-sagtewareprogramme beskikbaar waarmee skipbewegings en -kragte voorspel kan word. Die fokus van hierdie studie was om die numeriese modelle QUAYSIM en WAVESCAT te valideer. Saam vorm hierdie twee modelle ’n prosedure om vasgemeerde skipbewegings en -kragte veroorsaak deur lang- en kortgolfaksie te bepaal. Die validasieprosedure wat in hierdie studie gebruik is, behels ’n numeriese modelering van ’n fisiese situasie waar ’n vasgemeerde skip se bewegings en kragte onder kort- en langgolfkondisies gemeet is. ’n Fisiese model met ingeboude batimetrie is voorsien deur die Council for Scientific and Industrial Research (CSIR) se hidroliese laboratorium in Stellenbosch. Die model bestaan uit ’n vasgemeerde houerskip by ’n pier met verskeie ankerlyne en bootbuffers. ’n JONSWAPspektrum, wat kort- en langgolfkomponente kombineer, is gebruik om golfomstandighede vir die modellering van skipbewegings te simuleer. Golfperiodes en golfhoogtes is by spesifieke waarnemingstasies in die gesimuleerde hawe-area gemeet. Verdere opmetings, soos dié van die kragte in die bootbuffers en ankerlyne, is ook gedoen. ’n Stap-vir-stap benadering is gevolg om die skipbewegings numeries te voorspel. Eerstens is die kusprosesse wat in die gesimuleerde hawe plaasvind, gekalibreer met die numeriese paket SWAN Delft3D-WAVE. Die golfhoogtes en golfperiodes vir elke waarnemingstasie is bereken en vergelyk met die fisiese model se opmetings. Die SURFBEAT-module van Delft3D-FLOW is gebruik om die lae-frekwensie golwe in die kusarea te bereken. Lae-frekwensie golwe is die hoofoorsaak van skipbewegings en daarom is dit belangrik om dit te ondersoek gedurende die voorspellingsprosedure van skipbewegings. Na die golwe bereken is, moes die kragte wat beide kort en lang golwe op die skip uitoefen ook bereken word. Hierdie golfkragte is gemodelleer deur middel van die kombinasies SURFBEAT/LFSTRIP (langgolwe) en SWAN/WAVESCAT (kortgolwe). LF-STRIP het die skakel tussen golfmodelle en skipbewegingsmodelle verskaf en die lae-frekwensie golwe omgeskakel in langgolfkragte wat op die skip uitgeoefen is. WAVESCAT het die hoë-frekwensiegolwe omgeskakel in kortgolfkragte wat op die skip uitgeoefen is. Die berekende langgolf- en kortgolfkragte is ingevoer op die skipbewegingsmodel QUAYSIM om die skipbewegings en inperkingskragte in die bootbuffers en ankerlyne te bepaal sodat dit vergelyk kon word met die fisiese model, met die doel om moontlik die QUAYSIM/WAVESCAT-prosedure om gemeerde skipbewegings te voorspel te valideer. Die studie verskaf ’n oorsig van die opstel en resultate van die fisiese en numeriese modelle. Elk van die numeriese modelle SWAN, SURFBEAT, LF-STRIP, WAVESCAT en QUAYSIM word beskryf en vergelykings word getref tussen die numeriese en fisiese modelle vir elke prosedure. Die validasieprosedure verskaf nuttige dokumentasie van die kwaliteit van hierdie numeriese modeleringsprosedures wat reeds in sekere ontwerpprojekte gebruik word. Die numeriese WAVESCAT en QUAYSIM modelle van skipbewegings het ’n goeie korrelasie tussen die fisiese model en die numeriese benadering gelewer. Verbeteringe is wel steeds nodig. Goeie vergelykings is verkry vir langgolfbewegings (horisontale bewegings – stuwing (“surge”), swaai (“sway”) en gier (“yaw”)). Die stu- en swaaibewegings was effens oorskat met QUAYSIM. Die grootte van die gier was wel vergelykbaar maar is nie grafies goed uitgebeeld nie.

The process of calibrating a numerical model is examined in this thesis with an application to the flow of groundwater in the Willunga Basin in South Australia. The calibration process involves estimating unknown parameters of the numerical model so that the output obtained from the model is comparable with data that is observed in the field. Three methods for calibrating numerical models are discussed, these being the steepest descent method, the nonlinear least squares method, and a new method called the response function method. The response function method uses the functional relationship between the model's output and the unknown parameters to determine improved estimates for the unknown parameters. The functional relationships are based on analytic solutions to simplifed model problems or from previous experience. The three calibration methods are compared using a simple function involving one parameter, an idealised steady state model of groundwater flow and an idealised transient model of groundwater flow. The comparison shows that the response function method produces accurate estimates in the least amount of iterations. A numerical model of groundwater flow in the Willunga Basin in South Australia has been developed and the response function method used to estimated the unknown parameters for this model. The model of the Willunga Basin has been used to examine the sustainable yield of groundwater from the basin. The effect on groundwater levels in the basin using current and estimated extraction rates from the literature for sustainable yield has been examined. The response function method has also been used to estimate the rate of extraction to return the groundwater levels at a specific location to a desirable level. / Thesis (M.Sc.)--Department of Applied Mathematics, 2001.

This paper investigates the role of end-effects in superhydrophobic microchannels for frictional reduction through COMSOL based modeling. Two precursor derivations, the Kim & Hidrovo and Enright model are discussed and expanded upon through analytical and numerical simulations. The author performed numerical models on superhydrophobic microchannels with planar, stationary and finite separation distance of surface roughness element with perfect Cassie-Baxter air-layers. The simulations indicate an asymptotic limit for the flow-rate, indicating an optimum air-layer thickness. Numerical post processing reveals that this phenomenon is due to the recirculation end-effects that are relevant when the surface roughness separation distance is on order of magnitude of the channel width. These results are the first that identify end-effects as inducing a plateauing flow-rate and can serve as a benchmark for future studies. / text

Many environmental free surface flows involve water and sediment transport. The net changes to the surface level of an erodible bed by sediment entrainment and deposition processes have a feedback effect on the local ow hydrodynamics. Bed morphological change is of great socio-economic and environmental importance in that it affects navigation, flood risk management, water quality, species diversity, and overall river sustainability. This thesis describes a mathematical model of the depth-averaged shallow water-sediment equations based on mass and momentum conservation laws. A 2D numerical model is then presented of the fully coupled, variable-density governing equations, which are solved using a Godunov-type HLLC scheme. Dependent variables are specially selected in the numerical model to handle the presence of the variable-density mixture in the mathematical formulation. The model includes suspended sediment, bedload transport, and bed morphological change. The numerical model is verified against benchmark analytical and semi-analytical solutions for complicated, clear water flows, bedload transport and suspended sediment transport. The well-balanced property of the governing equations is verified for a variable-density dam break flow over a bed step. Simulations of an idealised dam-break flow over an erodible bed, in excellent agreement with previously published results, validate the ability of the model to capture complex water-sediment interactions under rapidly-varying flow conditions and a mobile bed, and validate the eigenstructure of the system of variable-density governing equations. The model is then further validated against laboratory based data for complex 2D partial dam breaks over fixed and mobile beds, respectively. The simulations of 2D dam break flows over mobile beds highlight the sensitivity of the results to the choice of closure relationships for sediment transport. To investigate this further, a parameter study is carried out using a variety of commonly used empirical formulae for suspended sediment transport. The numerical model is also used to inform a theoretical model that predicts the flow through and around a porous obstruction in a shallow channel. This problem is relevant to several practical applications, including flow through aquatic vegetation and the performance of arrays of tidal turbines in a finite-width tidal channel. The theoretical model is used to reinterpret the core flow velocities in laboratory-based data for an array of emergent cylinders in a shallow channel. Comparison with experimental data indicates the maximum obstacle resistance for which the theoretical model is valid. In a final application, the theoretical model examines the optimum arrangement of tidal turbines to generate power in a tidal channel, confirming that natural bed resistance increases the power extraction potential for a partial tidal fence.

Knee joint kinematics is the result of a complex roto-translation movementcharacteristic of the tibio-femoral (TF) and patello-femoral (PF) articulations.This movement depends on the shape of the femur, the tibial plateau andthe patella. Moreover, it depends also on the morphological and mechanicalproperties of the soft tissues of the knee joint. In fact, the knee is characterizedby an extrinsic stability due to the active constraints (muscles and tendons)and passive soft tissues (menisci, retinaculum and ligaments) that surround it.As a result, knee kinematics and kinetics are different in each human being, andsometimes, even in the same person, with the right knee behaving differentlycompared to the left one.The ideal total knee arthroplasty TKA, used to correct pathologies that couldaffect the knee joint, should enable the restoration of the patient’s functionalknee kinematics and kinetics, so that the patient does not normally notice theTKA implant.Nowadays, TKA surgery is a well-established procedure and surgeons maychoose from among the broad range of TKA solutions available on the marketto meet the patient’s request. Prostheses may differ because of shape, materials,and mechanical constraints of their components. Consequently, the restorationof the knee joint biomechanics is limited by the degrees of freedom guaranteedby the adopted design solution.Despite the success of TKAs, pain and limited motor skills are reportedto still affect the clinical outcomes and not all patients are shown to be happyafter a TKA.Current complaints regarding post-TKA surgery might be related to the absenceof a proven tool that enables predicting patient-specific outcomes based ondifferent TKA solutions and providing guidelines to surgeons. In fact, surgicalpre-planning is usually based on a patient’s evaluation that the clinician canmake also based on medical images, and clinical experience. Data reported inthe literature can help in guiding the surgeon to a final decision regarding thebest subject-specific solution.Numerical methods, able to simulate knee biomechanics for various configurations,can be fundamental for the development of the appropriate reliableand effective tools to support clinically-tailored responses to a question.In particular, they can be used for subject-specific analyses on the intact kneeand for supporting the surgical pre-planning phase by comparing the effect ofdifferent solutions.When developing a subject-specific knee model, different kinds of datainputsare needed, such as the knee shapes and alignment information, softtissuesbehavior and boundary conditions describing the investigated motortasks. Often, most of this requested data are unlikely to be available (e.g.subject-specific soft-tissues material properties). Consequently, it is a commonoperating procedure to integrate literature data with subject-specific informationin order to develop knee models for collecting personalized outputsthat could be used to address research and clinical questions.However, up to now, the resulting effect of different generalized sources, asa mix of subject-specific and literature data, still needs to be evaluated for itsimpact on personalized outputs concerning knee behaviour.Furthermore, clinical questions are often focused on specific requests thatpartially use features of more complex knee models that could require too muchtime to be efficiently incorporated into daily clinical evaluations.For these reasons, the principal aims of this research have been to assess,first, the impact of differently derived generalized sources on the developmentof an intact subject-specific knee model or after a TKA; second,to provide guidelines to identify efficient clinically-tailored data sourcesused in and for knee modeling.To accomplish these tasks, a numerical knee model of an intact knee wasdeveloped based on both subject-specific and literature data sources. Theinfluence of different approaches to deal with a subject’s information, such asthe reconstruction of the knee geometries from different imaging sources, hasiiibeen evaluated. Moreover, a sensitivity analysis was performed to understandthe potential changes on kinetics and kinematics outcomes due to differentlyderived literature inputs, such as models and the properties that characterizethe joint materials and ligaments description. The outputs collected after finiteelement analyses were analyzed and compared with already published experimentaloutcomes for the same analyzed specimen and replicated boundaryconditions.Additionally, the effects on knee joint contact forces and kinematics afterTKA surgery and due to the mis-alignment of implant components or misidentificationsof ligament insertions were evaluated in another sensitivityanalysis performed with a rigid body analysis for four different TKA designsimplanted in a subject-specific knee model. As for the intact knee model, theanalyzed configurations were compared against already published experimentaloutputs or literature data replicating similar boundary conditions.Moreover, several dedicated knee models were developed to address specificclinical questions, such as the lack of biomechanical explanations for certainbehaviours of TKA designs.Once compared to already published experimental or literature data, the resultsof the developed models agree.The main results from the numerical simulations performed show that, changingthe values of some of the parameters used as inputs, the knee model kinematicsis less influenced than the contact forces and stresses outputs.In particular, in developing an intact knee model, the main effecting parameteris the material properties selection for the knee cartilage layers. Among theconfigurations analyzed using subject-specific knee models with TKAs, theposition of the tibial component and the height of the patellar buttonare the most effecting inputs.Exploring the different chapters of this research thesis, several specific resultsare shown regarding each main step followed in developing a knee numericalmodel. For example, new approaches based on MRIs have been suggested andtested proving that they are suitable for collecting subject-specific informationregarding geometrical shapes and landmark definitions. Moreover, a newgraphical method was proposed resulting more effective and immediate thanconventional representations in reporting huge amount of data. In particular,the method is the favourite to show complex biomechanical analyses especiallyfor the clinical audience that replied to a survey. Furthermore, the differentmodels tailored to address specific clinical questions collected useful biomechanicalresults, to provide clinical advice or industrial guidelines, and can beconsidered as examples of what should be included in a knee model for similarscenarios.The results of this thesis offer several contributions. Generally, these findingscould provide useful guidelines for knee-model developers to achievea more balanced approach to subject-specific intact knee models based upongeneral sources in order to improve the understanding of personalized kneebiomechanics.To address a general comment to the title of this thesis, there is no singleanswer. In fact, the selection of data sources is case-dependent using, forexample, the subject’s or literature available data to describe material’s behavioror the boundary conditions of a specific motor task. Moreover, differentclinical questions can be addressed with different numerical approaches, e.g.finite element analysis is necessary especially in the case that stress outputs arerequested, but can be too time-consuming for addressing complex sensitivityanalyses.Once the knee model developer has identified the necessary data sources andthe approaches to be implemented, the question-tailored knee models can thusbe used for several applications such as predicting subject-specific abnormalknee kinematics and kinetics for different TKA designs, polyethylene wear,patellofemoral dislocation and bone remodeling, choosing the best fitting TKAdesign for a specific patient, and developing a procedure to optimize TKAimplant designs. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished