SHORELINE AT JETTY DUE TO CYCLIC AND RANDOM WAVES

This paper examines the effects of random and deterministic cycling of wave direction on the updrift beach planform adjacent to a jetty. Results provided using a simplified numerical model cast in dimensionless form indicate the importance of the time series of wave direction in determining design jetty length for a given net sediment transport. Continuous cycling of • wave direction leads to the expected analytical solution. Simplications in the numerical model used restrict the applications to small wave angles, no diffraction, no reflection of waves off structure, no refraction, and no sand bypassing at jetty. The concept can be extended to more sophisticated numerical models.

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Comparison of Local and Global Optimization Methods for Calibration of a 3D Morphodynamic Model of a Curved Channel

Water ◽

10.3390/w12051333 ◽

2020 ◽

Vol 12 (5) ◽

pp. 1333

Author(s):

Vahid Shoarinezhad ◽

Silke Wieprecht ◽

Stefan Haun

Keyword(s):

Global Optimization ◽

Sediment Transport ◽

Numerical Model ◽

Numerical Models ◽

Optimization Algorithms ◽

Flow Characteristics ◽

Optimization Methods ◽

Computational Time ◽

Curved Channel ◽

Time Model

In curved channels, the flow characteristics, sediment transport mechanisms, and bed evolution are more complex than in straight channels, owing to the interaction between the centrifugal force and the pressure gradient, which results in the formation of secondary currents. Therefore, using an appropriate numerical model that considers this fully three-dimensional effect, and subsequently, the model calibration are substantial tasks for achieving reliable simulation results. The calibration of numerical models as a subjective approach can become challenging and highly time-consuming, especially for inexperienced modelers, due to dealing with a large number of input parameters with respect to hydraulics and sediment transport. Using optimization methods can notably facilitate and expedite the calibration procedure by reducing the user intervention, which results in a more objective selection of parameters. This study focuses on the application of four different optimization algorithms for calibration of a 3D morphodynamic numerical model of a curved channel. The performance of a local gradient-based method is compared with three global optimization algorithms in terms of accuracy and computational time (model runs). The outputs of the optimization methods demonstrate similar sets of calibrated parameters and almost the same degree of accuracy according to the achieved minimum of the objective function. Accordingly, the most efficient method concerning the number of model runs (i.e., local optimization method) is selected for further investigation by setting up additional numerical models using different sediment transport formulae and various discharge rates. The comparisons of bed topography changes in several longitudinal and cross-sections between the measured data and the results of the calibrated numerical models are presented. The outcomes show an acceptable degree of accuracy for the automatically calibrated models.

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A RANS numerical model for cross-shore beach profile evolution

10.5194/egusphere-egu2020-10501 ◽

2020 ◽

Author(s):

Julio Garcia-Maribona ◽

Javier L. Lara ◽

Maria Maza ◽

Iñigo J. Losada

Keyword(s):

Sediment Transport ◽

Numerical Model ◽

Transport Model ◽

Numerical Models ◽

Computational Cost ◽

Physical Modelling ◽

Computational Effort ◽

Beach Profile ◽

Time Step ◽

Wave Conditions

The evolution of the cross-shore beach profile is tightly related to the evolution of the coastline in both small and large time scales. Bathymetry changes in extreme maritime events can also have important effects on coastal infrastructures such as geotechnical failures of foundations or the modification of the incident wave conditions towards a more unfavourable situation.The available strategies to study the evolution of beach profiles can be classified in analytical, physical and numerical modelling. Analytical solutions are fast, but too simplistic for many applications. Physical modelling provides trustworthy results and can be applied to a wide variety of configurations, however, they are costly and time-consuming compared to analytical strategies. Finally, &#160;numerical approaches offer different balances between cost and precision depending on the particular model.Some numerical models provide greater precision in the beach profile evolution, but incurring in a prohibitive computational cost for many applications. In contrast, the less expensive ones assume simplifications which do not allow to correctly reproduce significant phenomena of the near-shore hydrodynamics such as wave breaking or undertow currents, neither to predict important features of the beach profile like breaker bars.In this work, a new numerical model is developed to reproduce the main features of the beach profile and hydrodynamics while maintaining an affordable computational cost. In addition, it is intended to reduce to the minimum the number of coefficients that the user has to provide to make the model more predictive.The model consists of two main modules. Firstly, the already existing 2D RANS numerical model IH2VOF is used to compute the hydrodynamics. Secondly, the sediment transport model modifies the bathymetry according to the obtained hydrodynamics. The new bathymetry is then considered in the hydrodynamic model to account for it in the next time step.The sediment transport module considers bedload and suspended transports separately. The former is obtained with empirical formulae. In the later,the distribution of sediment concentration in the domain is obtained by solving an advective-diffusive transport equation. Then, the sedimentation and erosion rates are obtained along the seabed. Once these contributions are calculated, a sediment balance is performed in every seabed segment to determine the variation in its level.With the previously described strategy, the resulting model is able to predict not only the seabed changes due to different wave conditions, but also the influence of this new bathymetry in the hydrodynamics, capturing features such as the generation of a breaker bar, displacement of the breaking point or variation of the run-up over the beach profile. To validate the model, the numerical results are compared to experimental data.An important novelty of the present model is the computational effort required to perform the simulations, which is significantly smaller than the one associated to existing models able to reproduce the same phenomena.

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A Mathematical Model of Gas and Water Flow in a Swelling Geomaterial—Part 1. Verification with Analytical Solution

Minerals ◽

10.3390/min10010030 ◽

2019 ◽

Vol 10 (1) ◽

pp. 30 ◽

Cited By ~ 1

Author(s):

Elias Ernest Dagher ◽

Julio Ángel Infante Sedano ◽

Thanh Son Nguyen

Keyword(s):

Mathematical Model ◽

Numerical Model ◽

Analytical Solution ◽

Analytical Solutions ◽

Gas Flow ◽

Numerical Models ◽

Model Verification ◽

Model Complexity ◽

Gas Migration

Gas generation and migration are important processes that must be considered in a safety case for a deep geological repository (DGR) for the long-term containment of radioactive waste. Expansive soils, such as bentonite-based materials, are widely considered as sealing materials. Understanding their long-term performance as barriers to mitigate gas migration is vital in the design and long-term safety assessment of a DGR. Development and the application of numerical models are key to understanding the processes involved in gas migration. This study builds upon the authors’ previous work for developing a hydro-mechanical mathematical model for migration of gas through a low-permeable geomaterial based on the theoretical framework of poromechanics through the contribution of model verification. The study first derives analytical solutions for a 1D steady-state gas flow and 1D transient gas flow problem. Using the finite element method, the model is used to simulate 1D flow through a confined cylindrical sample of near-saturated low-permeable soil under a constant volume boundary stress condition. Verification of the numerical model is performed by comparing the pore-gas pressure evolution and stress evolution to that of the results of the analytical solution. The results of the numerical model closely matched those of the analytical solutions. Future studies will attempt to improve upon the model complexity and investigate processes and material characteristics that can enhance gas migration in a nearly saturated swelling geomaterial.

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A Method to Reduce the Calculation Time of Sediment Simulation by Controlling the Number of Long-term Wave Data

Korea Society of Coastal Disaster Prevention ◽

10.20481/kscdp.2021.8.4.307 ◽

2021 ◽

Vol 8 (4) ◽

pp. 307-314

Author(s):

Gweon-su Kim ◽

Ha-sang Ryu ◽

Sang-hoon Kim

Keyword(s):

Numerical Simulation ◽

Time Series ◽

Numerical Model ◽

Real Time ◽

Wave Direction ◽

Wave Data ◽

Simulation Results ◽

The Difference ◽

Reduced Time

In order to solve the difficulty of performing a numerical model using a long-term wave time series, a method of reducing wave time series was considered. And Numerical simulation of the sediment by the Delft3d model at the Maengbang Beach was conducted to verify the validity of the method. NOAA wave data were collected for about 40 years from January 1979 to May 2019. Among them, waves, which are judged to have insignificant effect on the beach, were removed and the wave time series was reduced. To this end, the entire wave time series was graded at intervals of 0.5m, period 2sec, and wave direction 10° to generate a total of 749 representative waves, and a numerical simulation of sediment was performed for each representative wave for 1 day. When the maximum sediment height was less than 0.01m/day, it was assumed that the influence of the representative wave on the area was negligible. As a result of conducting numerical simulation of the sediment using the 23-month real-time waves and the wave by the reduced time series, the difference between the two simulation results indicates a local sedimentation difference of 0.1 to 0.5 m near Deokbongsan. There is a difference in sedimentation of 0.01 to 0.1m overall, and the pattern of repeated erosion and sedimentation along the entire coast is very similar to both real-time waves and reduced time series waves.

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Aeolian Sediment Transport Integration in General Stratigraphic Forward Modeling

Journal of Geological Research ◽

10.1155/2011/186062 ◽

2011 ◽

Vol 2011 ◽

pp. 1-12

Author(s):

T. Salles ◽

C. Griffiths ◽

C. Dyt

Keyword(s):

Sediment Transport ◽

Numerical Model ◽

Transport Model ◽

Numerical Models ◽

Three Dimensional ◽

Transport Processes ◽

Aeolian Deposits ◽

Geological Processes ◽

Wide Range ◽

Mixed Soils

A large number of numerical models have been developed to simulate the physical processes involved in saltation, and, recently to investigate the interaction between soil vegetation cover and aeolian transport. These models are generally constrained to saltation of monodisperse particles while natural saltation occurs over mixed soils. We present a three-dimensional numerical model of steady-state saltation that can simulate aeolian erosion, transport and deposition for unvegetated mixed soils. Our model simulates the motion of saltating particles using a cellular automata algorithm. A simple set of rules is used and takes into account an erosion formula, a transport model, a wind exposition function, and an avalanching process. The model is coupled to the stratigraphic forward model Sedsim that accounts for a larger number of geological processes. The numerical model predicts a wide range of typical dune shapes, which have qualitative correspondence to real systems. The model reproduces the internal structure and composition of the resulting aeolian deposits. It shows the complex formation of dune systems with cross-bedding strata development, bounding surfaces overlaid by fine sediment and inverse grading deposits. We aim to use it to simulate the complex interactions between different sediment transport processes and their resulting geological morphologies.

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"Barbs" for river bend bank protection: application of a three-dimensional numerical model

Canadian Journal of Civil Engineering ◽

10.1139/l07-088 ◽

2007 ◽

Vol 34 (9) ◽

pp. 1087-1095 ◽

Cited By ~ 16

Author(s):

B Minor ◽

C D Rennie ◽

R D Townsend

Keyword(s):

Sediment Transport ◽

Numerical Model ◽

Flow Field ◽

Numerical Models ◽

Laboratory Data ◽

Three Dimensional ◽

Channel Bend ◽

Bank Protection ◽

Three Dimensional Models ◽

Movable Bed

A three-dimensional numerical model was used to examine the turbulent flow field and associated sediment transport due to a series of barbs (submerged groynes) in a channel bend. Model results were in good agreement with measured laboratory data and adequately simulated the important features of sediment transport. Statistical comparison of the predicted and measured equilibrium bed geometry found average regression coefficients of determination of 0.77 and 0.72 for the 90° and 135° channels, respectively. The predicted velocity data followed expected trends. The capability of a three-dimensional numerical model to simulate sediment transport through bend sections of a channel containing barbs was verified. This included the simulation of the effects of different arrangements of barb groups and an analysis of the data to determine the relation of the flow field to associated scour and deposition in a complex fluvial environment. These novel results are useful for improved analyses of the bank-protection capabilities of these structures and for the development and improvement of design guidelines.Key words: three-dimensional models, numerical models, movable bed models, channel bends, turbulence, secondary flow, scour, barbs, groynes.

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Preliminary Results on the Dynamics of a Pile-Moored Fish Cage with Elastic Net in Currents and Waves

Journal of Marine Science and Engineering ◽

10.3390/jmse9010014 ◽

2020 ◽

Vol 9 (1) ◽

pp. 14

Author(s):

Gianluca Zitti ◽

Nico Novelli ◽

Maurizio Brocchini

Keyword(s):

Numerical Model ◽

Laboratory Experiments ◽

Numerical Models ◽

Offshore Structures ◽

Fish Farm ◽

Maximum Displacement ◽

Drag Forces ◽

Real Size ◽

Lift And Drag ◽

Mesh Grid

Over the last decades, the aquaculture sector increased significantly and constantly, moving fish-farm plants further from the coast, and exposing them to increasingly high forces due to currents and waves. The performances of cages in currents and waves have been widely studied in literature, by means of laboratory experiments and numerical models, but virtually all the research is focused on the global performances of the system, i.e., on the maximum displacement, the volume reduction or the mooring tension. In this work we propose a numerical model, derived from the net-truss model of Kristiansen and Faltinsen (2012), to study the dynamics of fish farm cages in current and waves. In this model the net is modeled with straight trusses connecting nodes, where the mass of the net is concentrated at the nodes. The deformation of the net is evaluated solving the equation of motion of the nodes, subjected to gravity, buoyancy, lift, and drag forces. With respect to the original model, the elasticity of the net is included. In this work the real size of the net is used for the computation mesh grid, this allowing the numerical model to reproduce the exact dynamics of the cage. The numerical model is used to simulate a cage with fixed rings, based on the concept of mooring the cage to the foundation of no longer functioning offshore structures. The deformations of the system subjected to currents and waves are studied.

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Artificial Intelligence Application on Sediment Transport

Journal of Marine Science and Engineering ◽

10.3390/jmse9060600 ◽

2021 ◽

Vol 9 (6) ◽

pp. 600

Author(s):

Hyun Dong Kim ◽

Shin-ichi Aoki

Keyword(s):

Sediment Transport ◽

Numerical Models ◽

Beach Nourishment ◽

Hydraulic Model ◽

Alternative Methods ◽

Cross Sectional ◽

Sand And Gravel ◽

Incident Waves ◽

Artificial Intelligence Application ◽

Deep Learning Model

When erosion occurs, sand beaches cannot maintain sufficient sand width, foreshore slopes become steeper due to frequent erosion effects, and beaches are trapped in a vicious cycle of vulnerability due to incident waves. Accordingly, beach nourishment can be used as a countermeasure to simultaneously minimize environmental impacts. However, beach nourishment is not a permanent solution and requires periodic renourishment after several years. To address this problem, minimizing the period of renourishment is an economical alternative. In the present study, using the Tuvaluan coast with its cross-sectional gravel nourishment site, four different test cases were selected for the hydraulic model experiment aimed at discovering an effective nourishment strategy to determine effective alternative methods. Numerical simulations were performed to reproduce gravel nourishment; however, none of these models simultaneously simulated the sediment transport of gravel and sand. Thus, an artificial neural network, a deep learning model, was developed using hydraulic model experiments as training datasets to analyze the possibility of simultaneously accomplishing the sediment transport of sand and gravel and supplement the shortcomings of the numerical models.

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Development of Detailed FE Numerical Models for Assessing the Replacement of Metal with Composite Materials Applied to an Executive Aircraft Wing

Aerospace ◽

10.3390/aerospace8070178 ◽

2021 ◽

Vol 8 (7) ◽

pp. 178

Author(s):

Valerio Acanfora ◽

Roberto Petillo ◽

Salvatore Incognito ◽

Gerardo Mario Mirra ◽

Aniello Riccio

Keyword(s):

Composite Material ◽

Composite Materials ◽

Numerical Model ◽

Numerical Models ◽

Structural Performance ◽

Aircraft Wing ◽

Resin Infusion ◽

Effectiveness Analysis ◽

Liquid Resin Infusion ◽

Process Constraints

This work provides a feasibility and effectiveness analysis, through numerical investigation, of metal replacement of primary components with composite material for an executive aircraft wing. In particular, benefits and disadvantages of replacing metal, usually adopted to manufacture this structural component, with composite material are explored. To accomplish this task, a detailed FEM numerical model of the composite aircraft wing was deployed by taking into account process constraints related to Liquid Resin Infusion, which was selected as the preferred manufacturing technique to fabricate the wing. We obtained a geometric and material layup definition for the CFRP components of the wing, which demonstrated that the replacement of the metal elements with composite materials did not affect the structural performance and can guarantee a substantial advantage for the structure in terms of weight reduction when compared to the equivalent metallic configuration, even for existing executive wing configurations.

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