FINAL DESIGN OF THE NAGS HEAD BEACH NOURISHMENT PROJECT USING A LONGSHORE NUMERICAL MODEL

Nags Head, located at the northeastern part of North Carolina in the U.S., has sustained chronic erosion over the past 50 years. In 2005, Coastal Science & Engineering (CSE) was retained by the town of Nags Head to develop an interim beach restoration plan. Profile volume change was used in the planning and preliminary design of the project, and longshore and cross-shore numerical models were used in the final design to refine the preliminary nourishment plan and increase potential longevity of the project. This paper focuses on the key factors of the longshore numerical model setup for the project. These include model selection, input data and parameters, model calibration, and applications under different design alternatives. The Generalized Model for Simulating Shoreline Changes (GENESIS) was used in this study to evaluate shoreline evolution under normal wave conditions during various stages of the design life following the beach nourishment project. The model was used to identify the potential occurrence of erosional hotspots and to optimize the nourishment design so that the effects of such hotspots could be avoided or minimized where possible. Model results were also used to evaluate the impact of borrow area dredging on longshore transport in the project area and the impact of nourishment on shoaling in the adjacent inlet. The project encompasses 10.11 miles (mi) (16.28 kilometers-km) of ocean shoreline, and the design nourishment volume is based on the total permitted volume of 4 million cubic yards (cy) (3 million cubic meters-m³). [Note: As-built length was 10.0 mi and volume was 4.615 million cubic yards.] The final design has fill densities varying from north to south in relation to historical erosion rates and model projections. The average fill density is 75 cubic yards per foot (cy/ft) (188 m³/m) and ranges from 38 cy/ft to 150 cy/ft (95 m³/m to 375 m³/m). In conclusion, it is shown that the numerical model selected in this study was capable of predicting the overall performance of the large scale beach nourishment project in Nags Head as well as the performance at a particular location within or adjacent to the project, and its design methods can offer guidance to future projects.

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The importance of phase morphology for rheology of ferropericlase-bridgmanite mixtures

10.5194/egusphere-egu21-4384 ◽

2021 ◽

Author(s):

Marcel Thielmann ◽

Gregor Golabek ◽

Hauke Marquardt

Keyword(s):

Lower Mantle ◽

Mantle Convection ◽

Effective Viscosity ◽

Large Scale ◽

Numerical Models ◽

Phase Morphology ◽

Strong Impact ◽

Analytical Approximations ◽

The Impact ◽

Strong Control

<p>The rheology of the Earth&#8217;s lower mantle is poorly constrained due to a lack of knowledge of the rheological behaviour of its constituent minerals. In addition, the lower mantle does not consist of only a single, but of multiple mineral phases with differing deformation behaviour. The rheology of Earth&#8217;s lower mantle is thus not only controlled by the rheology of its individual constituents (bridgmanite and ferropericlase), but also by their interplay during deformation. This is particularly important when the viscosity contrast between the different minerals is large. Experimental studies have shown that ferropericlase may be significantly weaker than bridgmanite and may thus exert a strong control on lower mantle rheology.</p><p>Here, we thus explore the impact of phase morphology on the rheology of a ferropericlase-bridgmanite mixture using numerical models. We find that elongated ferropericlase structures within the bridgmanite matrix significantly lower the effective viscosity, even in cases where no interconnected network of weak ferropericlase layers has been formed. In addition to the weakening, elongated ferropericlase layers result in a strong viscous anisotropy. Both of these effects may have a strong impact on lower mantle dynamics, which makes is necessary to develop upscaling methods to include them in large-scale mantle convection models. We develop a numerical-statistial approach to link the statistical properties of a ferropericlase-bridgmanite mixture to its effective viscosity tensor. With this approach, both effects are captured by analytical approximations that have been derived to describe the evolution of the effective viscosity (and its anisotropy) of a two-phase medium with aligned elliptical inclusions, thus allowing to include these microscale processes in large-scale mantle convection models.</p>

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Crustal Fault Zones (CFZ) as Geothermal Power Systems: A Preliminary 3D THM Model Constrained by a Multidisciplinary Approach

Geofluids ◽

10.1155/2021/8855632 ◽

2021 ◽

Vol 2021 ◽

pp. 1-24

Author(s):

Hugo Duwiquet ◽

Laurent Guillou-Frottier ◽

Laurent Arbaret ◽

Mathieu Bellanger ◽

Théophile Guillon ◽

...

Keyword(s):

High Temperature ◽

Numerical Model ◽

Power Systems ◽

Fault Zone ◽

Field Data ◽

Large Scale ◽

Numerical Models ◽

Massif Central ◽

Temperature Anomalies ◽

Stress Direction

The Pontgibaud crustal fault zone (CFZ) in the French Massif Central provides an opportunity to evaluate the high-temperature geothermal potential of these naturally permeable zones. Previous 2D modeling of heat and mass transfer in a fault zone highlighted that a subvertical CFZ concentrates the highest temperature anomalies at shallow depths. By comparing the results of these large-scale 2D numerical models with field data, the depth of the 150°C isotherm was estimated to be at a depth of 2.5 km. However, these results did not consider 3D effects and interactions between fluids, deformation, and temperature. Here, field measurements are used to control the 3D geometry of the geological structures. New 2D (thin-section) and 3D (X-ray microtomography) observations point to a well-defined spatial propagation of fractures and voids, exhibiting the same fracture architecture at different scales (2.5 μm to 2 mm). Moreover, new measurements on porosity and permeability confirm that the highly fractured and altered samples are characterized by large permeability values, one of them reaching 10-12 m2. Based on a thermoporoelastic hypothesis, a preliminary 3D THM numerical model is presented. A first parametric study highlights the role of permeability, stress direction, and intensity on fluid flow. In particular, three different convective patterns have been identified (finger-like, blob-like, and double-like convective patterns). The results suggest that vertical deformation zones oriented at 30 and 70° with respect to the maximum horizontal stress direction would correspond to the potential target for high-temperature anomalies. Finally, a large-scale 3D numerical model of the Pontgibaud CFZ, based on THM coupling and the comparison with field data (temperature, heat flux, and electrical resistivity), allows us to explore the spatial geometry of the 150°C isotherm. Although simplified hypotheses have been used, 3D field data have been reproduced.

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Dynamic Response of a Single-Layer Reticulated Dome during Aircraft Impact Based on S-J Modeling Method

Shock and Vibration ◽

10.1155/2019/9056810 ◽

2019 ◽

Vol 2019 ◽

pp. 1-12

Author(s):

Li Lin ◽

Bo Huang ◽

Yunhui Sun ◽

Yu Zhu ◽

Duozhi Wang

Keyword(s):

Numerical Model ◽

Temperature Effect ◽

Failure Modes ◽

Numerical Models ◽

Material Model ◽

Modeling Method ◽

Dynamic Responses ◽

Shell Structures ◽

Large Strains ◽

The Impact

In previous numerical models developed for the impact dynamic responses of reticulated domes, mostly BEAM 161 elements and piecewise linear plastic material model have been employed and spherical joints have been simplified as intersection points of beams, which is called the B-P method. The B-P method can be employed in studying the dynamic responses of reticulated shells under low- to moderate-speed impacts with no obvious temperature effect. However, the analysis of the dynamic responses of reticulated shells under moderate- and high-speed impacts of missiles and other aircraft using this method had errors because it could not take into account the temperature effect. To accurately describe the mechanical responses of reticulated shells under aircraft impacts, the Johnson–Cook material model considering temperature effect with corresponding SHELL 163 element was selected for determining the members of the numerical model and the shell element was used to establish the spherical joints of reticulated shells; the whole process was called the S-J modeling method. This modeling method was capable of considering the effects of high strain rates, high temperatures, large strains, stress state change, and loading history. S-J and B-P methods were used to model the reticulated shell structures. Comparing the numerical analysis results of the drop hammer impact of the two developed methods with experimental results verified the accuracy of the S-J modeling method. In addition, based on the results obtained from the S-J modeling method and LS-DYNA finite element analysis software, a numerical model was established for small aircraft impact reticulated shells and the failure modes and dynamic responses of reticulated shell structures under aircraft impacts were studied. In terms of energy analysis, it was found that the effects of roof plates, spherical joints, and temperature softening could not be ignored in such studies.

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A Case Study on Curtailed Tidal Hydrodynamic Modeling along UAE Coast

The International Journal of Ocean and Climate Systems ◽

10.1260/1759-3131.3.1.45 ◽

2012 ◽

Vol 3 (1) ◽

pp. 45-56 ◽

Cited By ~ 1

Author(s):

R Balaji

Keyword(s):

Numerical Model ◽

United Arab Emirates ◽

Numerical Scheme ◽

Large Scale ◽

Water Levels ◽

Abu Dhabi ◽

Scale Model ◽

Large Scale Model ◽

Modeling Software ◽

Model Setup

A curtailed numerical model has been developed to assess the tidal hydrodynamics of entrance of a navigational channel in Abu Dhabi coast, United Arab Emirates. The curtailed model is developed using a finite element based numerical scheme, RMA2 (Donnell et al., 2006). The boundary conditions for the model were extracted from a large scale numerical model covering entire Abu Dhabi coast, developed using TELEMAC (Hervouet, 2000) modeling software. The hydrodynamic results of the curtailed model are validated with that of large scale model. The comparisons of water levels and current velocities obtained from the two models are found to be in agreement, demonstrating the efficiency and accuracy of the curtailed numerical model. The features of the tidal current pattern in the vicinity of the entrance of the navigational channel are also discussed. The details of the numerical scheme, model setup and methodology are presented and discussed in this paper.

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Fixed Grid Numerical Models for Solidification and Melting of Phase Change Materials (PCMs)

Applied Sciences ◽

10.3390/app9204334 ◽

2019 ◽

Vol 9 (20) ◽

pp. 4334 ◽

Cited By ~ 6

Author(s):

José Henrique Nazzi Ehms ◽

Rejane De Césaro Oliveski ◽

Luiz Alberto Oliveira Rocha ◽

Cesare Biserni ◽

Massimo Garai

Keyword(s):

Numerical Model ◽

Boundary Conditions ◽

Phase Change ◽

Latent Heat ◽

Phase Change Materials ◽

Source Term ◽

Numerical Models ◽

Fixed Grid ◽

Numerical Studies ◽

The Impact

Phase change materials (PCMs) are classified according to their phase change process, temperature, and composition. The utilization of PCMs lies mainly in the field of solar energy and building applications as well as in industrial processes. The main advantage of such materials is the use of latent heat, which allows the storage of a large amount of thermal energy with small temperature variation, improving the energy efficiency of the system. The study of PCMs using computational fluid dynamics (CFD) is widespread and has been documented in several papers, following the tendency that CFD nowadays tends to become increasingly widespread. Numerical studies of solidification and melting processes use a combination of formulations to describe the physical phenomena related to such processes, these being mainly the latent heat and the velocity transition between the liquid and the solid phases. The methods used to describe the latent heat are divided into three main groups: source term methods (E-STM), enthalpy methods (E-EM), and temperature-transforming models (E-TTM). The description of the velocity transition is, in turn, divided into three main groups: switch-off methods (SOM), source term methods (STM), and variable viscosity methods (VVM). Since a full numerical model uses a combination of at least one of the methods for each phenomenon, several combinations are possible. The main objective of the present paper was to review the numerical approaches used to describe solidification and melting processes in fixed grid models. In the first part of the present review, we focus on the PCM classification and applications, as well as analyze the main features of solidification and melting processes in different container shapes and boundary conditions. Regarding numerical models adopted in phase-change processes, the review is focused on the fixed grid methods used to describe both latent heat and velocity transition between the phases. Additionally, we discuss the most common simplifications and boundary conditions used when studying solidification and melting processes, as well as the impact of such simplifications on computational cost. Afterwards, we compare the combinations of formulations used in numerical studies of solidification and melting processes, concluding that “enthalpy–porosity” is the most widespread numerical model used in PCM studies. Moreover, several combinations of formulations are barely explored. Regarding the simulation performance, we also show a new basic method that can be employed to evaluate the computing performance in transient numerical simulations.

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Applicability of Calculation Formulae of Impact Force by Tsunami Driftage

Journal of Marine Science and Engineering ◽

10.3390/jmse9050493 ◽

2021 ◽

Vol 9 (5) ◽

pp. 493

Author(s):

Yoshimichi Yamamoto ◽

Yuji Kozono ◽

Erick Mas ◽

Fumiya Murase ◽

Yoichi Nishioka ◽

...

Keyword(s):

Large Scale ◽

Impact Force ◽

Numerical Models ◽

Indian Ocean Tsunami ◽

Tsunami Waves ◽

Secondary Damage ◽

The Pacific ◽

American Society ◽

The Impact ◽

Civil Engineers

The aftermath of the Indian Ocean tsunami on 26 December 2004 triggered by the off Sumatra earthquake (magnitude “M” = 9.1), and the Great East Japan earthquake of 11 March 2011 off the Pacific coast of Tohoku (M = 9.0), evidence the secondary damage from driftage collision due to large tsunami waves. To prevent this type of damage, the establishment of methods for predicting driftage movement and calculating the impact force by driftage is necessary. Several numerical models have been developed to predict the driftage movement of objects. Every year, these improve in accuracy and usability. In contrast, there are many calculation formulae for calculating the impact force. However, since there are considerable differences between values calculated using these formulae, the reliability of each formula is unknown. Therefore, in this research, one team of the committee on tsunami research of the Japan Society of Civil Engineers summarizes the main calculation formulae of impact forces that have been proposed until 2019. In addition, for each type of driftage (driftwood, containers, cars, ships), we compare calculation values of these formulae with measured data of large-scale experiments. Finally, we check the range of calculation values for each formula up to 15 m/s in collision velocity and clarify then the following facts: (1) In the case of driftwood, the formulae of Matsutomi, Federal Emergency Management Agency (FEMA) and National Oceanic and Atmospheric Administration (NOAA), and American Society of Civil Engineers (ASCE) are most reliable; (2) In the case of containers, the formulae of Matsutomi, Arikawa et al., FEMA and NOAA, Ikeno et al., and ASCE are most reliable; (3) In the case of cars, the formulae of FEMA and NOAA, and ASCE are most reliable; (4) In the case of ships, the formulae of Mizutani, FEMA and NOAA, and ASCE are most reliable.

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Influence of Detailed Topography when Modeling Flows in Street Junction During Urban Flood

Journal of Disaster Research ◽

10.20965/jdr.2012.p0560 ◽

2012 ◽

Vol 7 (5) ◽

pp. 560-566 ◽

Cited By ~ 4

Author(s):

Pierre-Henri Bazin ◽

◽

Anne Bessette ◽

Emmanuel Mignot ◽

André Paquier ◽

...

Keyword(s):

Urban Areas ◽

Large Scale ◽

Numerical Models ◽

Flow Section ◽

Urban Flood ◽

Eddy Viscosity Model ◽

Image Velocimetry ◽

Urban Topography ◽

Scale Particle ◽

The Impact

Floods in dense urban areas propagatemainly through the streets, where the flow can be locally affected by elements of urban topography. This study aims at assessing the need of integrating detailed topography in numerical models when simulating urban floods. Acoustic Doppler Velocimetry and Large Scale Particle Image Velocimetry measurements in an experimental three branch junction representing a city crossroad are used to calibrate a numerical model solving the 2D shallow water equations. A constant eddy viscosity model proves to be accurate enough to calculate velocity fields, but such model requires a fine calibration against experimental data. Simulations run with this calibrated model are performed to study the impact of obstacles and sidewalks representative of urban areas. It is found that obstacles located in the downstream branch can highly perturb the velocities distribution downstream of the junction, whereas obstacles located in the upstream branches have less influence. The presence of sidewalks results in reduced flow section and higher velocities, but additional effects occur within and downstream of the junction. Simulations presented here show the need of considering detailed topography and elements of urban furniture if local velocities have to be represented.

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Numerical Model of a Vertical-Axis Cross-Flow Tidal Turbine

Volume 9: Ocean Renewable Energy ◽

10.1115/omae2020-18514 ◽

2020 ◽

Author(s):

Ruiwen Zhao ◽

Angus C. W. Creech ◽

Alistair G. L. Borthwick ◽

Takafumi Nishino ◽

Vengatesan Venugopal

Keyword(s):

Numerical Model ◽

Large Scale ◽

Cross Flow ◽

Vertical Axis ◽

Numerical Predictions ◽

Tidal Turbine ◽

Model Setup ◽

Vertical Axis Tidal Turbine ◽

The University ◽

University Of New Hampshire

Abstract An array of close-packed contra-rotating cross-flow vertical-axis tidal rotors, a concept developed to maximize the fraction of flow passage swept, has potential advantages for hydrokinetic power generation. To predict the commercial feasibility of such rotors in large-scale application, a numerical model of a vertical-axis turbine (VAT) with a torque-controlled system is developed using an actuator line model (ALM). The open-source OpenFOAM computational fluid dynamics (CFD) code is first coupled with this ALM model, and efficiently parallelized to examine the characteristics of turbulent flow behind a vertical axis tidal turbine. The numerical model is validated against previous experimental measurements from a 1:6 scale physical model of a three-bladed reference vertical axis tidal turbine at the University of New Hampshire (UNH-RM2). Satisfactory overall agreement is obtained between numerical predictions and measured data on performance and near-wake characteristics, validating the numerical model. Details of the model setup and discussions on its output/results are included in the paper.

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Impact of TMI SST on the Simulation of a Heavy Rainfall Episode over Mumbai on 26 July 2005

Monthly Weather Review ◽

10.1175/2008mwr2291.1 ◽

2008 ◽

Vol 136 (10) ◽

pp. 3714-3741 ◽

Cited By ~ 13

Author(s):

S. K. Deb ◽

C. M. Kishtawal ◽

P. K. Pal ◽

P. C. Joshi

Keyword(s):

Large Scale ◽

Numerical Models ◽

Convective Available Potential Energy ◽

India Meteorological Department ◽

Tropical Rainfall Measuring Mission ◽

Atmospheric Modeling ◽

Cumulus Parameterization ◽

Surface Boundary ◽

Maximum Rainfall ◽

The Impact

In this study the simulation of a severe rainfall episode over Mumbai on 26 July 2005 has been attempted with two different mesoscale models. The numerical models used in this study are the Brazilian Regional Atmospheric Modeling System (BRAMS) developed originally by Colorado State University and the Advanced Research Weather Research Forecast (WRF-ARW) Model, version 2.0.1, developed at the National Center for Atmospheric Research. The simulations carried out in this study use the Grell–Devenyi Ensemble cumulus parameterization scheme. Apart from using climatological sea surface temperature (SST) for the control simulations, the impact of the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) SST on the simulation of rainfall is evaluated using these two models. The performances of the models are compared by examining the predicted parameters like upper- and lower-level circulations, moisture, temperature, and rainfall. The strength of convective instability is also derived by calculating the convective available potential energy. The intensity of maximum rainfall around Mumbai is significantly improved with TMI SST as the surface boundary condition in both the models. The large-scale circulation features, moisture, and temperature are compared with those in the National Centers for Environmental Prediction analyses. The rainfall prediction is assessed quantitatively by comparing the simulated rainfall with the rainfall from TRMM products and the observed station values reported in Indian Daily Weather Reports from the India Meteorological Department.

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Felled Trees as a Rockfall Protection System, Experimental Study for Numerical Models Calibration

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.566.449 ◽

2014 ◽

Vol 566 ◽

pp. 449-454

Author(s):

I. Olmedo ◽

Franck Bourrier ◽

D. Bertrand ◽

Frédéric Berger ◽

Ali Limam

Keyword(s):

Numerical Model ◽

Numerical Models ◽

Contact Point ◽

Protective Capacity ◽

Mountain Areas ◽

Optimal Position ◽

Energy Forest ◽

Device Interaction ◽

The Impact

In mountain areas, natural hazards, such as snow avalanches, landslides and rockfall threat towns, communication routes and people. It is known that forests have a major capacity to dissipate rockfall energy. Forest maintenance or storms can reduce forest’s protective capacity; after such a reduction, felled trees can be strategically left on the slopes in order to replace live trees. The efficacy of these devices and their optimal position can be analyzed by developing a numerical model describing the rock-wooden device interaction. To develop a relevant model of these wooden devices when impacted, the research was focused, in one hand, on a rigorous characterization of the fresh wood mechanical properties to recreate the real dynamic response of stems after the impact. In the other hand, the local impactor-wood stem interaction at the contact point was analyzed. Laboratory experiments using Charpy pendulum, presented in this text, have been carried out to assess the calibration of the numerical model. Experimental results of the impact force and their relation with stems mass and the impact energy level were treated and commented. A second serie of experiments has enabled to characterize the law describing the contact between the stem and the impactor.

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