Use Of Numerical Models Research Articles

Geochemical Modelling of Inorganic Nutrients Leaching from an Agricultural Soil Amended with Olive-Mill Waste Biochar

This work examines in silico the dominant geochemical processes that control inorganic nutrients (Ca, Mg, Na, K) availability in irrigated agricultural soil amended with potassium-enriched biochar (from olive mill wastes) at mass doses of 0.5%, 1%, 2% and 10%. The geochemical modelling step was supported by analytical measurements regarding the physicochemical characteristics of the irrigation water, the agricultural soil and the biochar. Two geochemical approaches, namely equilibrium exchange (E.E.) and kinetic exchange (K.E.) models were applied and compared to assess nutrient release with an emphasis on potassium availability. Equilibrium exchange perspective assumed that nutrient release is controlled by ion-exchange reactions onto the biochar surface, whilst kinetic exchange perspective assumed the contribution of both ion-exchange and dissolution of salts. Results indicated that for the E.E. model, the soluble amount of potassium is readily available for transport within the pores of the porous media, and therefore is leached from the column within only 10 days. For the K.E. model that assumes a kinetically controlled release of potassium due to interactions occurring at the solid-solution interface, the assessed retention times were more realistic and significantly higher (up to 100 days). Concerning the applied doses of biochar, for a 2% biochar fraction mixed with soil, for example, the available K for plants doubled compared with the available K in the soil without biochar. In any case, the use of numerical modeling was proven helpful for a quick assessment of biochar performance in soil, by avoiding time-consuming and laborious experimental set-ups. Validation of the models by experimental data will further establish the proposed mechanisms.

Environmental State of a Harbor in Terms of Waters Renewal. A Case Study for a Fishery Harbor in Thessaloniki Gulf

The waters renewal of the fishery harbor of Nea Krini is presented here. The harbor is located at the east Thessaloniki Gulf (NE Thermaikos Gulf, Greece). The main research point is focused on the environmental state of the harbor which is under construction. Under that point of view, the description of a two-dimensional, depth average, hydrodynamic model follows, in order to simulate the wind generated circulation of waters, initially on the greater area of Thermaikos Gulf and then on the coastal basin of the fishing harbor. The renewal of waters in the harbor’s basin is subsequently studied. Tidal effects on the waters’ renewal are also studied. The calculation of the concentration of Biochemically Oxygen Demand (BOD) in the fishing harbor for the average time of waters’ renewal is then examined for three different cases, concerning the existence and operation of openings on the body of the groins. Finally, the analysis of the results shows a good environmental state of the harbor. It is obvious that the use of numerical models for different scenarios of engineering and design approaches can lead to the prognosis of hydrodynamic and environmental sate of a harbor’s basin so that the best possible technical design can be adopted.

РАСЧЕТНЫЙ АНАЛИЗ ПОВЕДЕНИЯ ПОДШПАЛЬНОГО ОСНОВАНИЯ ПРИ ЕГО СТАБИЛИЗАЦИИ ГЕОСИНТЕТИЧЕСКИМИ МАТЕРИАЛАМИ

Common feature of reconstruction and construction of new railways is in the need to have a high-quality track subgrade. Meanwhile, geosynthetic materials play an important role, for example, for improving bearing strength of the subgrade and for the increase of service life of track structure in whole. Hardness of the «subgrade - geogrid» composite system and the change of the stress-strain condition of unstabilized sleeper bearing in the comparison with the stabilized one are estimated with the use of the finite element modeling. According to results of culvert tests the paper presents comparison of plate settlement on the subgrade stabilized by the geogrid and unstabilized road-metal subgrade. Moreover, the authors assess the efficiency of subgrade strengthening by the geogrid with the use of numerical modeling.

Computational analysis of aortic haemodynamics in the presence of ascending aortic aneurysm.

BACKGROUND: The usefulness of numerical modelling of a patient’s cardiovascular system is growing in clinical treatment. Understanding blood flow mechanics can be crucial in identifying connections between haemodynamic factors and aortic wall pathologies.OBJECTIVE: This work investigates the haemodynamic parameters of an ascending aorta and ascending aortic aneurysm in humans.METHODS: Two aortic models were constructed from medical images using the SimVascular software. FEM blood flow modelling of cardiac cycle was performed using CFD and CMM-FSI at different vascular wall parameters.RESULTS: The results showed that highest blood velocity was 1.18 m/s in aorta with the aneurysm and 1.9 m/s in healthy aorta model. The largest displacements ware in the aorta with the aneurysm (0.73 mm). In the aorta with the aneurysm, time averaged WSS values throughout the artery range from 0 Pa to 1 Pa. In the healthy aorta, distribution of WSS values changes from 0.3 Pa to 0.6 Pa.CONCLUSIONS: In the case of an ascending aortic aneurysm, the maximum blood velocity was found to be 1.6 times lower than in the healthy aorta. The aneurysm-based model demonstrates a 45% greater wall displacement, while the oscillatory shear index decreased by 30% compared to healthy aortic results.

Extreme Rainfall-Runoff Events Modeling by HEC-HMS Model for Koudiet Rosfa Watershed, Algeria

Changing of precipitation regime and intensification of extreme storms in semi-arid regions because of climate change requires the use of numerical models to forecast the outlet hydrographs. In this paper, HEC-HMS software was applied using a loss method the curve number CN to estimate the precipitation excess and a parametric unit hydrograph model to compute the transformation of precipitation excess into direct runoff over the watershed. The Muskingum-Cunge routing model was used to simulate the propagation of direct runoff through the main streams of Koudiet Rosfa watershed. The curve number CN and lag time parameters were used to calibrate the model towards several storms. The Nash–Sutcliffe efficiency coefficient (NSE) was adopted to assess the performance of the model to reproduce the observed hydrographs. Volume of the storms, peak discharges, times of peak and times of center of mass between the simulated and observed discharges were used to validate the model. The simulated discharges reproduce the hydrological events. The calibrated model was used to simulate the different hypothetical storms that could occur in the future in order to ensure the safety of Koudiet Rosfa dam towards extreme rainfall-runoff events. Keywords:  HEC-HMS model; Hydrologic model; Rainfall-runoff; Semi-arid region.

STRESS-DEFORMED STATE RESEARCH OF THE MAIN GIRDER IN THE SINGLE-GIRDER CRANE AND SELECTION OF A RATIONAL SECTION

The paper studies of the stress-strain state of the main girder of a single-girder crane were carried out using finite element analysis. A large share of the mechanization of various production processes is made up of lifting and transporting machines. Overhead cranes are the main lifting equipment of production shops. Single-beam cranes are widely used in all parts of workshops: in the machine room, in the warehouse of finished products. The use of crane equipment, its trouble-free operation determines the efficiency of modern production and the productivity of the enterprise. Reducing the weight of the crane, its cost price while maintaining and even improving the technical characteristics is an urgent requirement of the time. The design and optimization of modern metal constructions of cranes is a complex task that requires the use of numerical modeling. To analyze the resulting stresses and movements in Autodesk Invertor 2018, a 3D model of the main girder of a single-girder overhead crane with a load capacity of 2 tons and a span of 6 meters was built. The material of the main beam of the crane is СТ09Г2С steel. In the study, a finite-element model of the metal structure of a bridge suspended single-girder crane was developed and a finite-element static analysis was made in order to determine the stress-strain state of the metal structure in the most loaded state. Boundary conditions for fixing the beam and the load were set, taking into account the own weight of the beam and the weight of the electric hoist. The distribution of stresses and displacements along the entire length of the beam was analyzed. In order to reduce the weight of the crane, four versions of the metal structure were analyzed: basic and three with reduced weight. After the analysis of the stressed-strained state, the most optimal option was proposed. Prospects for the development of further study of this problem were also identified. Keywords: beam, stress, deformation, finite element analysis.

Multi-scale physico-chemical characterization of CEB/ANS bio-composites

A current concern of researchers is to improve the response of compressed earth blocks (CEB), mainly to water attacks by reducing the hydrophilic character of the soil matrix. this work contributes to the formulation of a new soil-based material containing argan nutshell powder (ANS), insofar as the stabilization of compacted soil by cellulosic materials allows to obtain a higher impermeability aspect. Accordingly, a regression of about 32% of the coefficient of capillary absorption has been highlighted with the addition of 2% ANS stabilizer, beyond this percentage, the decrease in absorption becomes less significant.In a vision to identify the non-linear behavior of the compressed earth blocks (CEB) reinforced by the Argan nut shells particles (ANS) influenced by many parameters like the shape, the distribution, and the quantity of the stabilizers, as well as the interactions between both phases: matrix and reinforcement. The use of numerical models seems to be indispensable. Yet, simulations of heterogeneous structures quickly become unaffordable by direct calculations on finite element software. Therefore, a homogenization of the experimental, and numerical macrostructure is performed. Thus, an overall micro-meso-macro approach to modeling the mechanical behavior of CEB/ANS biocomposites has been established. It is mainly based on the notion of the representative elementary volume with two different structures (periodic structure and structure with a poisson distribution). The numerical homogenization results were validated by the Young’s modulus values resulting from the experimental compression test and the corresponding stress–strain curves.

Development of a simplified methodology for furnace aerodynamics with vortex combustion of organic fuel modeling

This paper describes the process of developing a simplified methodology for furnace aerodynamics during the development or modernization of combustion schemes with direct-flow burners. This technique is based on the use of numerical modeling of air movement and turbulence phenomena in the furnace volume and allows for a relatively short period of time to analyze a large number of options for the burners and nozzles location. This is its advantage in comparison with the use of experimental modeling or numerical simulation with combustion when analyzing a variety of schemes. The model was developed on the basis of validated results of combustion processes numerical simulation in the K-50 boiler furnace. The paper presents the results of calculations performed for several variants of the simplified methodology. For further use, the option that best corresponds to full-scale studies taking into account the fuel combustion process has been selected. The main states of the methodology are formulated.

Green Roofs for domestic wastewater treatment: Experimental and numerical analysis of nitrogen turnover

The use of Green Roofs (GRs) for domestic wastewater treatment and nitrogen (N) removal is an appealing opportunity to conjugate hydrological, energetic, and water quality benefits. However, the research in this direction has been limited to few experimental studies, while the role of numerical modeling for analysis and design has been overlooked. To advance understating of reactive transport processes in GRs and investigate the use of numerical models, this study presents a comprehensive experimental and numerical investigation of the N turnover in vegetated and non-vegetated GRs exposed to domestic wastewater injection. A Bayesian framework is used to calibrate a mechanistic numerical model against multiple observations from a controlled laboratory experiment. A Global Sensitivity Analysis complements the framework to further enlighten the role of multiple physical processes. Results indicate that GRs have high nitrification capacity, which increases after wastewater application. The total leached N is 94% of the total injected N in a non-vegetated GR, compared to 67% for a vegetated GR. Nitrate leaching is negatively correlated with the root solute uptake capacity of the vegetation, which may reach up to 32% of the total injected N. Maximization of this factor is desirable and can be achieved by selecting appropriate plant species and reducing water stress periods using a proper irrigation schedule.

Numerical modelling of large deformation problems in geotechnical engineering: A state-of-the-art review

Many problems in geotechnical engineering involve large movements or rotations, examples include natural processes such as landslides, and man-made processes such as earthmoving and pile penetration. While the use of numerical modelling, primarily the finite element method (FEM), is now routine in geotechnical design and analysis, the limitations of conventional FEMs soon become apparent when attempting to model large deformation problems. For this reason, the search for alternatives remains a key goal of many geotechnical researchers, both to find accurate methods but also to develop efficient ones. In this review paper, prompted by Technical Committee 103 of the International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE), we survey the current state-of-the-art in numerical modelling techniques aimed at large deformation problems in geotechnics. The review covers continuum and discontinuum methods and provides a clear picture of what is and is not currently possible, which will be of use to both practitioners seeking suitable methods and researchers developing existing or new methods.

A numerical modelling of a multi-layer LaFeCoSi Active magnetic regenerator by using Artificial Neural Networks

• Artificial Neural Networks are included into an active magnetic regenerator model. • The analytical formulation of the new numerical model is evidenced. • Artificial Neural Networks improve the evaluation of magnetocaloric properties. • The new model shows a better accuracy than the previous one. One of the main problems in the framework of magnetic refrigeration regards low adiabatic temperature changes that occur in the magnetocaloric materials, which limits the widespread application of this technology. Therefore, the major effort of researchers is focused on the development of multi-layer Active Magnetic Regenerators, which allows to enlarge the temperature span of a magnetic refrigerator. The use of numerical models can help to understand the feasibility of such application with less effort in comparison with the use of experimental facilities. One of the main challenges in designing a numerical model of a multi-layer Active Magnetic Regenerator is the effective incorporation of the magnetocaloric data of different magnetocaloric materials, which are fundamental to correctly optimize the configuration of such a device with the aim to improve its performance. These data are usually obtained experimentally from different measurements and their integration into the numerical model is challenging. Therefore, this work proposes a modified multi-layer Active Magnetic Regenerator numerical model based on Artificial Neural Networks to integrate the magnetocaloric properties of magnetocaloric materials, allowing an easier and a more reliable implementation of the real properties of magnetocaloric materials. The proposed model was tested simulating a four-layer and a seven-layer LaFeCoSi Active Magnetic Regenerator. The use of Artificial Neural Networks to integrate the magnetocaloric properties of magnetocaloric materials into the multi-layer Active Magnetic Regenerator allowed to improve the accuracy of the model in comparison with the commonly used technique (i.e., Curie temperature shift method) when compared to the experimental data. Indeed, the maximum error of the maximum temperature span with zero thermal load was reduced from about 13 K to 6.6 K , for the seven-layer configuration, and from about 4.1 K to 1.0 K , for the four-layer configuration. Furthermore, the new model allows to obtain more reliable simulated data about the effectiveness of each layer of the Active Magnetic Regenerator, providing a more useful tool to discuss about the optimization of its configuration. The results shows that Artificial Neural Networks can be successfully applied for integrating the magnetocaloric properties of magnetocaloric materials into a multi-layer Active Magnetic Regenerator numerical model, improving its performance. They represent an innovative way to address the problem of including magnetocaloric properties into numerical models, opening the way to other possible Machine Learning techniques as alternatives to the usual Curie temperature shifting method used in the literature to date.

Assessment of mmWave Handset Arrays in the Presence of the User Body

The emergence of mobile terminals operating at millimeter-wave frequencies necessitates the ability to evaluate the effect the environment, and in particular, users have on their radiation properties. Some studies evaluated the shadowing effects of a hand or an entire body for simple antenna configurations. This letter proposes a method for reliably predicting the performance of different array geometries in the presence of the users when they operate the mobile with one or with two hands. In practice, the way a mobile is operated is varying strongly between users, and hence, it is of great interest to draw a methodology to both numerically and experimentally evaluate any handset design in a large number of use cases in a repeatable manner. The use of numerical models and realistic phantoms allow high repeatability when evaluating the terminal radiation under real use conditions. Both the simulated body and the human phantom are used to study the field scattering from the handset arrays subject to the user interaction, yielding consistent results between them. Results suggest that shadowing by the user's torso usually decreases gain between 20-30 dB close to the region of the user. The user posture largely affects the spherical coverage, particularly for those antennas close to the corners in a two-hand mode.

Development and applications of debris mobility models in Hong Kong

Landslides are major natural hazards that can pose significant risks to human lives and properties in mountainous areas. Mobility assessments of landslide debris are integral to the management of landslide risks. Over the past two decades, the Geotechnical Engineering Office (GEO) in Hong Kong has expended considerable effort on the development of debris mobility models, and a suite of advanced numerical tools has been developed using different numerical techniques, including particle-in-cell, smoothed particle hydrodynamics and arbitrary Lagrangian–Eulerian methods. The accuracy of the tools was corroborated against historical landslides in Hong Kong and typical values of model parameters were established for use in routine practice. These numerical tools offer geotechnical practitioners a pragmatic and efficient approach to assess the dynamics of landslide debris in landslide hazard investigations and quantitative risk assessments. Some of the numerical tools recently developed by the GEO can also be used to assess the dynamic interaction between landslide debris and structural countermeasures, thereby allowing design optimisation. This paper presents a holistic review of the technical development and engineering applications of these numerical tools with a focus on their roles in landslide risk management in Hong Kong. It also documents the experience of Hong Kong in steering and promoting the use of numerical modelling of large ground mass deformations for the purposes of slope safety management.

The role of parameters of foundation structures in the formation of a stress-strain state of the foundations of the building

Requirements for the reliability and cost-effectiveness of rational foundation structures determine the performance of calculations taking into account the interaction of the loadbearing structures of the building with the soil base. Computer modeling makes it possible to perform such calculations and obtain the stress-strain state of the structures of the building and the soil base.
 Numerical modeling of the interaction of a building with a soil massif makes it possible to study the influence of all components of the system "soil base - foundation - building". At the same time, during numerical modeling it is possible to consider different options for the location of elements in the plan, different geometric dimensions of the elements and their properties. The results of the interaction calculations of the building with the soil base make it possible to choose the best option for foundation structures, which is cost-effective and ensures reliable operation of the building.
 In this study, the search for rational parameters of the foundation structures of the building was performed by numerical modeling of the joint work of the elements of the system "soil base - foundation - building". The study was performed on the example of a 16-storey frame building.
 A study of the influence of the parameters of the pile foundation on the stress-strain state of the foundation structures and bearing elements of the frame of the building:
 -The influence of the piles location in the plan is considered. The process of redistribution of forces in piles depending on the amount and location within the contour of the building is investigated. Deformation assessment is performed.
 -The optimal pile length has been searched. The relationship between the length of piles and deformations, their load-bearing capacity and quantity has been studied. The distribution of piles according to the coefficient of use of their bearing capacity has been obtained.
 -A study of the influence of the stiffness of the foundation pile cap on the redistribution of stresses and strains in the structures of the building. The relationship between the thickness of the pile cap and the percentage of reinforcement elements of the frame of the building has been obtained.
 It is confirmed by the results of the research that the use of numerical modeling of the interaction of the pile foundation with the soil base allows to obtain a quantitative assessment of the stress-strain state. It becomes possible to search for rational parameters at the design stage of foundation structures.

Analysis of the production process of the forked forging used in the excavator drive system in order to improve the currently implemented technology by the use of numerical modeling

Abstract The study concerns a comprehensive analysis of a multistage hot-die forging on hammers, in order to produce a yoke-type forging, used as a component of excavator power transmission systems. The investigations were conducted with the aim to analyze and identify the sensitive areas in the process and then improve the currently implemented forging technology by using finite element (FE) simulation. QuantorForm (the developer of the QForm program) has developed a thermomechanical numerical model for the production of forked forging. The software Computer-Aided Three-Dimensional Interactive Application (CATIA) was used to develop and build Computer-Aided Design (CAD) models of forging tools. As a result of the numerical simulations, the plastic deformations and temperature distributions for the forgings and tools were obtained, and the force courses during the forging process were analyzed. The obtained results enabled a thorough analysis of the forging process, including identification of potential forging defects (laps) as well as those tool areas that are the most loaded and exposed to damage. On this basis, changes were implemented in the production process, which allowed for the improvement of the currently implemented technology and obtaining the corrected forgings.

FEM for prediction of surface deformations induced by flooding of steeply inclined mining seams

The closure of coal mines is closely linked to the change in European energy policy regarding the reduction of CO2 emissions. The process of closing underground mines has impacted many mining companies, especially in Europe. Along with the decision to close a mine, a number of steps have to be taken with regard to its liquidation. One of these is the decision to begin flooding the mining excavations with underground water. The process of liquidation of an underground mine brings with it a number of problems and dangers related to, among others, the environment, geomechanics and surface protection.This article aims to present the possibility of forecasting deformation of the land surface as a result of the flooding of underground excavations characterised by steeply inclined seams and to indicate the dangers posed by the liquidation of underground mines to the environment and civil engineering structures. The use of numerical modelling is an innovative approach to the problem of steeply inclined flooded seam induced surface deformations. It is an interdisciplinary area that encompasses mining and environmental protection.The authors present numerical calculations and simulations of land surface uplift resulting from the liquidation process for a case study (Spanish mine). The calculations were made by Finite Element Modelling (FEM). The authors have created numerical models characterised by steeply inclined seams, and based on the authorship methodology they have calculated the surface deformation. The obtained results were verified by measurements. Such analysis was never done before. The authors proved that with numerical modelling and developed methodology, it is possible to successfully forecast surface deformations during the liquidation of mines by flooding. Then, based on the obtained forecast values, a discussion on the possibility of mining damage in the analysed area may begin. Such damages have been observed during the flooding of German mines.The conducted research is interdisciplinary in the field of mining and civil and environmental engineering. Furthermore, the very issue of damage is also important from the socio-economical point of view.

Variation of Seasonal Monsoon Wave-Driven Circulation Pattern in the Lee of Groyne in Kuala Nerus beach

Terengganu coast tend to dual monsoonal as presenting Northeast Monsoon (NEM) as a storm season and Southwest Monsoon (SWM) as a calm season. The area of interest is a groyne in Kuala Nerus, Terengganu on east part of Peninsular Malaysia. The use of numerical model was performed on the dual monsoon seasons with MIKE 21 modules (Spectral Wave FM and Flow Model Hydrodynamic FM modules). Two numerical model were set up according to the two season. The resulting model indicates, the current circulation pattern consisted of persistent eddy re-circulation in the lee of the groyne during both season. As the longshore current directed into the groyne, it deflected offshore resulting in rip current along the groyne. The rip current and incoming wave converge at the tip of the groyne and flow parallel to coastline before being projected onshore performing a re-circulation cell. During NEM, the model shows a clockwise re-circulation cell and counter-clockwise formation during SWM. The formation of the rip current and eddy circulation is associated with erosion event as the sediment transported offshore causing sediment shortage on the adjacent shore. The importance of this study can be a reference to any development of coastal defense monsoon dominated environment.

Numerical investigation of the mechanism of granular flow impact on rigid control structures

Baffles and check-dam systems are often used as granular flow (rock avalanches, debris flows, etc.) control structures in regions prone to dangerous geological hazards leading to massive landslides. This paper explores the use of numerical modelling to simulate large volume granular flow and the effect of the presence of baffles and check dam systems on granular flow. In particular, the paper offers a solution based on the smoothed particle hydrodynamics numerical method, combined with a modified Bingham model with Mohr–Coulomb yield stress for granular flows. This method is parallelised at a large scale to perform high-resolution simulations of sand flowing down an inclined flume, obstructed by rigid control structures. We found that to maximise the flow deceleration ability of baffle arrays, the design of baffle height ought to reach a minimum critical value, which can be quantified from the flow depth without baffles (e.g. 2.7 times for frictional flows with friction angle of 27.5°). Also, the check-dam system was found to minimise run-out distances more effectively but experiences substantially higher forces compared to baffles. Finally, flow-control structures that resulted in lower run-out distances were associated with lower total energy dissipation, but faster kinetic energy dissipation in the granular flows; as well as lower downstream peak flow rates.

Numerical modelings of ultrashort pulse propagation and conical emission in multimode optical fibers

We make use of two well-known numerical approaches of nonlinear pulse propagation, namely, the unidirectional pulse propagation equation and the multimode generalized nonlinear Schrödinger equation, to provide a detailed comparison of ultrashort pulse propagation and possible conical emission in the context of multimode optical fibers. We confirm the strong impact of the frequency dispersion of the nonlinear response on pulse splitting and supercontinuum dynamics in the femtosecond regime for pumping powers around the critical self-focusing threshold. Our results also confirm that the modal distribution of optical fibers provides a discretization of conical emission of the corresponding bulk medium (i.e., here fused silica). This study also provides some criteria for the use of numerical models, and it paves the way for future nonlinear experiments in commercially available optical fibers.

Study of three domestic sewage submarine outfall plumes through the use of numerical modeling in the São Sebastião channel, São Paulo state, Brazil

The dispersion of the thermotolerant coliform plumes emitted from the Araçá, Itaquanduba and Cigarras domestic sewage submarine outfalls in the São Sebastião Channel was modeled. The plumes were simulated as the only pollution sources considering bacterial decay for the summer and winter of 2016. The main goal was to determine if and which areas were impacted by the disposal systems. The simulated concentrations were quantitatively compared with Enterococcus and thermotolerant coliform data provided by sanitation agencies in São Paulo state (CETESB and SABESP). The UM3 model from Visual Plumes software and the ECOM were used as the near-field and far-field models, respectively. The ECOM was configurated with 37 sigma levels and its horizontal resolution varies from 0.2 km to 5 km. The modeled concentrations did not exceed the limit stated by CONAMA Resolution 274 (2000), with the exception of that in June 2016. The main conclusion of this study is that channel hydrodynamic patterns are sufficient to disperse the plumes from sewage disposal outfalls. The areas adjacent to Araçá outfall presented the highest persistence of coliform concentrations; however, the modeled concentrations did not exceed 1000 MPN/100 mL for more than 0.1% of the time. The simulations satisfactorily reproduced the coliform variability and dispersion in the region.