Simulation Of Morphological Changes Research Articles

Modelling beach volume changes caused by moderate and weak hydrodynamic conditions

The goals of this study were the calibration of the XBeach model for moderate and weak hydrodynamic conditions in 2D mode and the determination of the volumetric changes induced by them. An evaluation of model performance was made based on the Brier Skill Score (BSS), the visual match of the profile shape (VMS), the absolute volumetric change error (m3/m) and the relative volumetric change error (%). An analysis of accuracy in determining volumetric changes in the dune coast, with XBeach applied, provided an average absolute error in determination of volumetric changes of 4.0 m3/m for a significant storm and 1.5 m3/m for moderate and weak hydrodynamic conditions in a 2D model calibration process. Simulations of morphological changes caused by moderate and weak hydrodynamic conditions for seven timeframes classified into three groups have been run in 2D mode. Within a validation process, the average absolute error in the determination of volumetric changes in the beach was ranging from 0.64 m3/m to 2.42 m3/m depending on the group of hydrodynamic conditions. A high value of the correlation coefficient (R) between the measured and modelled balance of volumetric changes (m3/m) for all timeframes – 0.79 and for the ‘strongest’ group no. 3 – 0.91 were revealed. For the remaining groups, i.e., group no. 1 and no. 2 of hydrodynamic conditions, no such correlation was observed. Furthermore, the temporal analysis of the sum of beach volumes proved that a rising trend was observed over 4 months. Thus, moderate and weak hydrodynamic conditions dominated the accumulation within the area of study. XBeach reflected this trend well, producing a difference between the measured and modelled sum of volumes at the end of the timeframe of 7.27 m3/m, which is close to the volume determination error by the model.

Mathematical model for simulation of morphological changes associated to crypt fission in the colon

<p style='text-indent:20px;'>Morphological changes due to colorectal cancer propagation by an abnormal crypt fission is an interesting application arising in medicine and biology, that we try to analyse by a differential equations model coupled with a discrete crypt fission model. A colonic crypt can slowly change its shape in three steps: growth, bifurcation and fission. Fission is a rare event in a normal tissue, however if transit cells are unable to differentiate, due to an activation of Wnt signaling, then it may become fast and uncontrolled and cause a formation of aberrant crypt foci (ACF), defined as clusters of aberrant crypts. The differential equation system is composed by a convective diffusive equation for transit cell density and an elliptic equation for cell pressure, both defined on a manifold. The discrete crypt fission model acts in a set of adjacent crypts in order to investigate the ACF dynamics, due to a differentiation block. By using a Galerkin finite element method we solve numerically the differential equation model and show some interesting results about an ACF formation caused by a deformation and fission of abnormal crypts.</p>

Numerical Simulation to Determine the Effectiveness of Groynes and Breakwaters as Protective Structures for Gandoriah Beach, Pariaman City

This research is about numerical simulation to determine the effectiveness of groynes and breakwaters as protective structures for Gandoriah Beach in Pariaman City (West Sumatra - Indonesia) using an existing program. The effectiveness of the protective structure can be seen based on the bathymetry that is formed as a result of this structure performance. In the simulation of the present research, the direction of the incoming waves at the offshore boundary condition is the dominant direction, namely the west direction, with two wave conditions, namely during normal and stormy times. Simulations of morphological changes are carried out in six scenarios. The first three scenarios are for wave simulations under normal conditions with no shore protective structures (scenario 1), with groynes (scenario 2) and with breakwaters (scenario 3). Meanwhile, the second three scenarios are for wave simulation in storm conditions with no shore protective structures (scenario 4), with groynes (scenario 5) and with breakwaters (scenario 6). The simulation results for the 20 days state show that in normal wave conditions, the breakwaters have a fairly good performance for the formation of sedimentation behind the structures so that it is estimated that the formation formed is tembolo. Meanwhile, groyne is only effective to restrain the sedimentation rate along the structures. In the wave simulation during stormy time, there is a dominant current along the nearshore. In this case the performance of the groynes is better than the breakwaters because the groynes can inhibit the rate of erosion along the shore. Due to the use of breakwaters there is erosion behind the structures. Based on the simulation results without shore protective structures, both in normal and storm waves, abrasion and erosion processes occur, so that Gandoriah Beach needs handling.

Development of methodology for assessment of long‐term morphodynamic impact on flood hazard

AbstractA methodology for quantification of the impact of sediment transport on flood hazard is proposed. The applied algorithm consists of several Python scripts for automation of sediment routing, hydrodynamic simulations, and geoprocessing of results. Flood hazard maps are uniquely linked with particular simulations of morphological changes in a river. Finally, the maps are stochastically processed. The proposed procedure was applied for a selected reach of the Warta river, located in Poland. Simulations were run for 6‐ and 12‐year flow series composed randomly on the basis of historical data. The 30 flow series for each period and four functions describing the transport of sediment were treated as uncertain variables. It was assumed that the features characterising the mean sample may properly represent the sediment content in the river reach studied. The final results are presented as maps showing the probabilities of inundation. The comparison of results with literature data confirmed the significance of the impact related to sediment transport processes on the quantification of flood hazard uncertainty. The main advantages of the presented algorithm are effective management of simulations and processing of results obtained in 240 runs of the sediment routing model.

Numerical Simulation of Morphological Changes due to the 2004 Tsunami Wave around Banda Aceh, Indonesia

The 2004 Indian Ocean tsunami caused massive morphological changes around the coast of Sumatra, Indonesia. This research investigates the coastal morphological changes in the Banda Aceh area via coupling a hydrodynamic model with a sediment transport module. The Cornell Multigrid Coupled Tsunami Model (COMCOT) was coupled with the XBeach Model to simultaneously simulate sediment transport and the hydrodynamic process during the tsunami. The coupled model is known as COMCOT-SED. Field bathymetric data measured in 2006 were used to validate the coupled model. This study reveals that the tsunami’s impact was more severe on the eastern part of the coast, where it hit directly. Meanwhile, the western part of the coast suffered a lower impact because of the sheltering effects from a series of small islands and a headland to the north. This study has shown that the model results from COMCOT-SED are consistent with field data and show where the tsunami waves caused offshore erosion.

A coarse-grained multiscale model to simulate morphological changes of food-plant tissues undergoing drying.

Numerical modelling has emerged as a powerful and effective tool to study various dynamic behaviours of biological matter. Such numerical modelling tools have contributed to the optimisations of food drying parameters leading to higher quality end-products in the field of food engineering. In this context, one of the most recent developments is the meshfree-based numerical models, which have demonstrated enhanced capabilities to model cellular deformations during drying, providing many benefits compared to conventional grid-based modelling approaches. However, the potential extension of this method for simulating bulk level tissues has been a challenge due to the increased requirement for higher computational time and resources. As a solution for this, by incorporating meshfree features, a novel coarse-grained multiscale numerical model is proposed in this work to predict bulk level (macroscale) deformations of food-plant tissues during drying. Accordingly, realistic simulation of morphological changes of apple tissues can now be performed with just 2% of the previous computational time in microscale and macroscale simulations can also be conducted. Compared to contemporary multiscale models, this modelling approach provides more convenient computational implementation as well. Thus, this novel approach can be recommended for efficiently and accurately simulating morphological changes of cellular materials undergoing drying processes, while confirming its potential future expansion to efficiently and accurately predict morphological changes of heterogeneous plant tissues in different spatial scales.

Effectiveness of N-waves for predicting morphological changes due to tsunamis

The research on morphological changes caused by tsunamis has increased considerably in the last few years, yet the processes behind this phenomenon are still not fully understood. This paper analyzes and compares numerical simulations of morphological changes caused by the leading elevation and leading depression N-waves and tsunami waves propagating over a channel with a simple bed slope. The simulations were carried out by means of a coupled flow, sediment transport and morphodynamic two-dimensional-vertical numerical model. The modeled channel bed was composed of cohesionless sediments, and range of values for the bed slope and the wave height were employed. Four tsunami waveforms were studied to test the appropriateness of N-waves in modeling the morphological changes caused by tsunamis. On the modeling performed here, runup values were quite well represented by N-waves. N-waves also represented qualitatively well the morphological changes caused by tsunamis. Yet, values of flow velocities and suspended sediment concentration showed more severe deviations from the modeled results corresponding with tsunami waves, very likely due to differences on the steepness of the waves. Therefore, even when N-waves can and have been used to represent tsunami runup and inundation distance, our results suggest that they should be considered with caution when intended to predict magnitudes of tsunami flow velocities and consequently morphological changes. The use of N-waves to simulate morphological changes caused by tsunamis is not yet converging and must be further investigated.

Numerical simulations of morphological changes in barrier islands induced by storm surges and waves using a supercritical flow model

In this paper, an advanced explicit finite volume flow model in two-dimensions is presented for simulating supercritical coastal flows and morphological changes in a tidal/coastal inlet and barrier islands due to storm surges and waves. This flow model is coupled with existing wave-action model and sediment transport model. The resulting integrated coastal process model is capable of simulating flows induced by extreme conditions such as waves, surge tides, river flood flows, etc., and morphological changes induced by rapid coastal currents and waves. This developed supercritical flow model is based on the solution of the conservative form of the nonlinear shallow water equations with the effects of the Coriolis force, uneven bathymetry, wind stress, and wave radiation stresses. The forward Euler scheme is used for the unsteady term; and the convective term is discretized using the Godunov-type shockcapturing scheme along with the HLL Riemann solver on non-uniform rectilinear grids. The accuracy of the developed model is investigated by solving an experimental dam-break test case. Barrier island breaching, overflow and overwash due to severe storm attack are simulated and the predicted morphological changes associated to the events are analyzed to investigate the applicability of the model in a coast where all the physical forces are present.

Multi-Layered Potts Model Simulation of Morphological Changes of the Neck during Sintering in Cu-Ni System

A mathematical model is developed in this study to simulate the morphological change of the sintering neck by neck growth and the Kirkendall void formation in the Cu-Ni interdiffusion system. The fluxes of materials and vacancy are analyzed for estimating excessive-deficient vacancy regions. The Multi-Layered Potts Model (MLP Model) is used as the mathematical model. The MLP Model is an improved model of the traditional Potts Model which can treat multiple materials transportation mechanisms such as interdiffusion system. The Potts Model uses a two dimensional (2-d) array to describe a 2-d microstructure, on the contrary, the MLP Model uses a three dimensional (3-d) array which stacks several 2-d arrays. The MLP Model of present study could treat an interdiffusion and an intrinsic diffusion coefficient as a function of the local alloy component. The morphological change and analyzed materials and vacancy fluxes of the simulation results are compared with the experimental results, then good agreements is observed.

Numerical simulation of morphological changes in rivers and reservoirs

For the computation of the morphological changes in river or reservoir beds, due to erosion or deposition, a hydrodynamic model is combined with the sediment continuity equation. The hydrodynamic model is based upon the equations of mass and momentum conservation. For the solution of the above system of three partial differential equations, the explicit numerical schemes of MacCormack and Lax-Wendroff are tested. The whole mathematical model is applied to two experimental cases and to a real case. The first experimental case concerns the aggradation in a laboratory channel due to sediment overloading, and the second one the sediment release from a reservoir after a dam break. The real case concerns the morphological changes in the torrent Mallero (Northern Italy) during a flood event.

Computer-generated surgical simulation of morphological changes in microstructures: concepts of “virtual retractor”

The author's goal was to develop a computer graphics model to simulate the displacement and morphological changes that are caused by the retraction of fine intracranial structures. The authors developed an application program to interpolate the contour of models of an artery and a retractor. The center of the displacement was determined by spatial coordinates, and the shape of the displacement of the arterial model was calculated by using a cosine-based formula with representation of a brain retractor. This computer graphics model was applied to the simulation of the displacement and morphological changes that occur when retraction is performed in the optic nerve. An illustrative case is presented, in which the optic nerve was displaced by a retractor to simulate the surgery performed in a carotid cave aneurysm of the internal carotid artery. The authors have named this methodological tool “virtual retractor.” This new navigational system for open microneurosurgery would be useful in teaching surgical microanatomy and in presurgical operative planning.

Simulation of Trabecular Surface Remodeling based on Local Stress Nonuniformity.

In this study, to investigate mechanical remodeling of cancellous bone from the viewpoint of trabecular surface remodeling due to trabecular level mechanical stimuli, a rate equation for trabecular surface remodeling is proposed based on the uniform stress hypothesis, which suggests that nonuniformity in the local stress distribution on the trabecular surface is the driving force for remodeling. A proposed local rate equation for trabecular surface remodeling is applied to a computational simulation of morphological changes, in which the trabeculae are modeled as an assemblage of two-dimensional boxel elements and their morphological changes are simulated by removal / addition of the elements from / to the trabecular surface. The basic features of the proposed rate equation and simulation method are investigated through remodeling simulations applied to the basic trabecular-level structure, cancellous-bone-level structure and the proximal femur. In all cases, the trabecular orientation, thickness and connectivity are adapted to the mechanical environment, which demonstrates the capability of the proposed rate equation for computational prediction of the adaptation phenomenon and supports the hypothesis regarding the optimality of trabecular architecture as a mechanical load bearing structure.

Simulation of Trabecular Surface Remodeling Based on Local Stress Nonuniformity.

To investigate mechanical remodeling of cancellous bone from the viewpoint of trabecular surface remodeling due to trabecular level mechanical stimuli, first, a rate equation for trabecular surface remodeling is proposed based on the uniform stress hypothesis, which suggests that the nonuniformity of the local stress distribution on the trabecular surface is the driving force for remodeling. The proposed local rate equation for trabecular surface remodeling is applied to a computational simulation of morphological changes, in which the trabeculae are modeled as an assemblage of two-dimensional boxel elements and their morphological changes are simulated by removal/addition of the elements from/to the trabecular surface. The basic features of the proposed rate equation and simulation method are investigated through the remodeling simulations applied to the basic trabecular element, cancellous bone structure and the proximal femur. In all cases, the trabecular orientation, thickness, and connectivity are adapted to the mechanical environment, which demonstrates the capability of the proposed rate equation for computational prediction of the adaptation phenomenon and supports the hypothesis regarding the optimality of trabecular architecture as a mechanical load bearing structure.

Computer simulation of morphological changes of grain boundary precipitates growing by the ledge mechanism

A previously developed computer model was modified to simulate the growth of grain boundary precipitates which grow by the ledge mechanism. The ledges were assumed to be nucleated in the grain boundary region at constant, parabolically decreasing, and random rates and to grow under the control of volume diffusion of solute to or from the riser of ledges. At lower under coolings at which the motion of individual ledges is slow, late-nucleated ledges soon catch up with first-nucleated ones, and precipitates tend to extend along the grain boundary: the overall precipitate shape is essentially that of a grain boundary allotriomorph. At larger undercoolings, first-nucleated ledges move fast to form a protuberance similar to Widmanstatten sideplates, while late-nucleated ones stay near the grain boundary region. The transition of precipitate shape from one to the other occurs in a very narrow range of supersaturation. The results are compared with various characteristics of the growth of proeutectoid ferrite allotriomorphs and sideplates in Fe-C alloys documented in the literature.

A SYSTEM OF MATHEMATICAL MODELS FOR THE SIMULATION OF MORPHOLOGICAL PROCESSES IN THE COASTAL AREA

A compound mathematical model (COMOR) for the simulation of morphological changes in the coastal area is being developed. The model is very flexible; it can be composed according to the specific demands of the problem which is considered. So far the model is being applied in the advisory practice to predict initial morphological changes. Recent experiences have shown that the model is quite useful, although at present the knowledge of the individual coastal processes and their interactions is still insufficient to utilize it optimally. However, it is foreseen that in the near future such mathematical models will become a powerful tool in coastal engineering.