Dispersion Coefficient Research Articles

Study on the segregation effect of pyrite and brass ore particles under combined pendulum vibration

This article uses a combined pendulum mode to study the segregation behavior of spherical particles of pyrite and brass ore with different diameters using the discrete element method. The numerical simulation program includes extensive oscillation tests on binary mixed particles of pyrite and brass ore spherical particles in different steel U-shaped oscillation grooves, different oscillation frequencies, oscillation angles, and particle sizes. The dispersion coefficient γ calculated from the Lacey mixing index M is used to characterize the segregation behavior of binary mixed particles and track the evolution of segregation. Numerical simulation shows that the oscillation frequency is 8 Hz, the oscillation amplitude is 14°, and the dispersion coefficient γ of the first group with protrusions reaches 0.8, which is about 19.4% higher than the dispersion coefficient 0.67 of the first group with light grooves. The dispersion coefficient γ of the second group with added protrusions reached 0.69, which is about 16.95% higher than the dispersion coefficient 0.59 of the second group when using a light groove. The addition of protrusions improved the particle layering effect. The oscillation amplitude is taken as 14°, and the oscillation frequencies are taken as 6Hz, 8Hz, 10Hz, and 12Hz, respectively. As the oscillation frequency increases, collisions between particles become more intense, and the dispersion coefficient γ between particles increases to a certain extent when it changes from 6Hz to 8Hz. Then, as the oscillation frequency increases, the dispersion coefficient γ decreases in severe fluctuations, and the particle stratification effect actually deteriorates. The oscillation frequency is taken as 8Hz, and the oscillation amplitude is taken as 10°, 14°, and 18°, respectively. After the oscillation amplitude increases to 14°, the dispersion coefficient γ of the particles remains basically stable, and changing the oscillation amplitude has almost no effect on the particle stratification effect. The oscillation frequency is 8Hz, and the oscillation amplitude is 14°. When adding protrusions to the steel U-shaped oscillation groove, the average relative errors of both experimental schemes are less than 1%, and the correlation coefficients are close to 1. The data points are very close to the 45° line. It indicates that the experimental data and simulation values have high consistency, and the discrete element method is feasible and reliable as a method for studying mineral particulate matter. The in-depth study of the separation and stratification behavior of ore particles under combined oscillation is of great scientific significance for the development of new combined vibration equipment.

Effect of phase exchange kinetics on Taylor dispersion of chemically reactive solutes in an oscillatory magnetohydrodynamics flow between two parallel plates

The study of kinetic sorptive effects on the transport phenomena of reactive solute has numerous real-world applications, including in the industrial and environmental sectors. These kinds of investigations become more realistic when an oscillatory pressure gradient with both the reversible and irreversible reactions at the channel walls is considered in a magnetohydrodynamics flow. In the past, Ng and Yip [J. Fluid Mech. 446, 321–345 (2001)] studied the effect of sorptive phase exchange at boundaries on the solute transport phenomena in an open-channel flow using Mei's multiple-scale homogenization technique. They considered fluid flows without magnetic field and boundary absorption. This work uses the above-mentioned method to investigate the phase exchange kinetics of Taylor dispersion phenomena in a two-dimensional magnetohydrodynamics fluid flowing through a parallel channel. The paper discusses how various parameters and dimensionless numbers, such as the Hartmann, oscillatory Reynolds, and Damkohler, affect the flow velocity, transport coefficient, multi-dimensional concentration distributions, and transverse variation rate. Due to the strong magnetic field, the flow velocity and Taylor dispersivity are adversely affected and conspicuously reduced. Additionally, for large Damkohler numbers, the total dispersion coefficient and the Taylor dispersion coefficient both decrease. However, the longitudinal concentration distribution rises with the Hartmann number and partition coefficient. It is worth noting that in the presence of unequal boundary absorption, there is no occurrence of transverse symmetry in solute concentration at any given time. Controlling various processes of tracer dispersion in environmental systems, especially water purification and the chemical industry, may benefit from these intriguing findings.

Transient dispersion of reactive solute transport in electrokinetic microchannel flow

Motivated by emerging applications in bio-microfluidic devices, the present study rigorously examines the generalized Taylor–Gill hydrodynamic dispersion of a point source solute injected into a microchannel, influenced by a constant axial static electric field along the channel and charged surface with different wall potentials. The solute engages in a first-order irreversible chemical reaction at both the microchannel walls. By incorporating different wall potentials and absorptive coefficients at the lower and upper walls, the current transport model for electro-osmotic flows is extended to encompass a wider range of applications. The solute transport phenomenon is intricately modeled using the unsteady convective diffusion equation. Employing Gill's generalized dispersion model, a concentration decomposition technique, up to the third-order accuracy, we meticulously analyze the transport process. Furthermore, a comprehensive comparison between analytical outcomes and numerical simulations using the Brownian Dynamics method is undertaken, enhancing the robustness of the analytical approach. The scattering process is mainly analyzed with the help of exchange, convection, dispersion, and asymmetry coefficients, along with the mean concentration profile. The effect of initial solute release at various vertical locations in the microchannel is shown to exert a considerable impact on all the transport coefficients at initial times.

Athermal pulsational mode dynamics with negative ions

The stability dynamics of the pulsational mode of gravitational collapse (PMGC), excitable in athermal (nonthermal) spherical complex dust molecular clouds (DMCs) in the presence of active role of negative ions, is semi-analytically investigated. The adopted partially ionized DMC model consists of five constitutive plasma species, well-coupled via the gravito-electrostatic Poisson formalism, depicting the corresponding potential-density correlations. The nonthermal uncorrelated lighter (inertialess) species are electrons, positive ions, and negative ions. The thermal correlated heavier (inertial) species are neutral and charged dust grains. The application of a standard spherical wave analysis results in a generalized linear cubic dispersion equation involving a new set of multi-factorial dispersion coefficients dependent on diverse equilibrium plasma parameters. A numerical illustrative platform is broadly created to analyze the DMC stabilization and destabilization factors relative to the non-local inward Newtonian self-gravity. It is interestingly seen that the DMC stabilizing agents are the radial cloud size, dust charge, neutral dust viscoelastic relaxation time, Tribeche thermostatistical parameters, etc. In contrast, the dust mass and equilibrium neutral dust density show destabilizing effects, and so forth. The results systematically explored here are fairly consistent and reliably correlated with the previous results on structure formation mechanism in the DMCs as heretofore reported extensively in the literature.

Effect of an inclined magnetic field on dispersion of solute in a pulsatile flow through a channel of absorptive porous walls

The present investigation gives an insight to comprehend the complex mechanism of species transport through porous walls, which has applications for crude oil refining, oil reservoir engineering, and separation of metal from fluids. The paper analyzes the impact of an inclined magnetic field on mass transport phenomena of solute through an unsteady, viscous, incompressible, and electrically conducting fluid flowing between two parallel plates. Both plates are permeable, and the flow is driven by a periodic pressure gradient. At both channel walls, the first order boundary reaction is applied. The governing time depending advection and diffusion equation is solved numerically based on Aris's method of moments. To determine the axial mean concentration distribution of solute, the first four central moments are used in a Hermite polynomial representation. It is significant to note that the dispersion of tracer is more significant for the low frequencies rather than the high frequencies. The behavior of the dispersion process of the tracer is studied for various flow parameters such as the angle of inclination of the magnetic field (α), Hartmann number (M), absorption parameter (β), suction Reynolds number (R), injection Reynolds number (R′), Womersley number (ω), and dispersion time (t) for both purely oscillatory and combined flows. It is significant to note that with the increment of R, α, and M, the amplitude of the dispersion coefficient of the solute reduces. On the other hand, an opposite phenomenon is observed for R′. It is seen that the transport coefficient moves cyclically with a double frequency period for all values of R and R′. Also, it is found that the peak of the mean concentration distribution enhances with the increment of α and M because the flow velocity decreases.

Modeling the deterioration of the stiffness and of the collagen fibril distribution in a discrete model of the cornea microstructure

We present a stochastic approach to model the mechanical deterioration of the reinforcing microstructure of the human cornea. The fundamental structural micro-components of the stroma, collagen and crosslinks, are assembled deterministically into an elementary trusswork cell, multiply repeated and distorted to form a three-dimensional shell with the shape of a cornea. The spatial orientation of the collagen-like elements of each cell is thus characterized stochastically with a non correlated random angle field, obeying an assigned probability density function, leading to a non-deterministic structural stiffness. It follows that the mechanical response of the model to the action of deterministic forces equivalent to the intraocular pressure is stochastic due to the random spatial orientation of collagen fibers. The deterioration of the mechanical stiffness of the collagen components is described through a scalar variable field, evolving in space and in time, representative of a progressive damage which causes heterogeneity and asymmetric behavior. The damage variable acts in two ways on the global stiffness: (i) by reducing the stiffness of the collagen components; (ii) by modifying the dispersion coefficient of the probability density function. The equilibrium equations of the damaging model are solved at discrete time steps, with a fully explicit solution scheme, by means of the stochastic finite element improved perturbation method. The results show that when the collagen fibril stiffness reduces to 10% of the healthy value, as expected in the case of the vision-impairing condition known as keratoconus, the displacement field due to intraocular pressure is significantly affected in terms of both average and variance distributions. This effect confers a typical conical shape to the cornea. In particular, the analysis shows that high values of the response variances are confined in the keratoconus area, which agrees with a high level of uncertainties due to loss of fibril organization and thickness reduction under pathologic conditions.

Quantum scattering of icosahedron fullerene C60 with noble-gas atoms

There exist multiple ways to cool neutral molecules. A front runner is the technique of buffer gas cooling, where momentum-changing collisions with abundant cold noble-gas atoms cool the molecules. This approach can, in principle, produce the most diverse samples of cold molecules. We present quantum mechanical and semiclassical calculations of the elastic scattering differential cross sections and rate coefficients of the C60 fullerene with He and Ar noble-gas atoms in order to quantify the effectiveness of buffer gas cooling for this molecule. We also develop new three-dimensional potential energy surfaces for this purpose using dispersion-corrected density functional theory (DFT) with counterpoise correction. The icosahedral anisotropy of the molecular system is reproduced by expanding the potential in terms of symmetry-allowed spherical harmonics. Long-range dispersion coefficients have been computed from frequency dependent polarizabilities of C60 and the noble-gas atoms. We find that the potential of the fullerene with He is about five times shallower than that with Ar. Anisotropic corrections are very weak for both systems and omitted in the quantum scattering calculations giving us a nearly quantitative estimate of elastic scattering observables. Finally, we have computed differential cross sections at the collision energies used in experiments by Han et al. (Chem Phys Lett 235:211, 1995), corrected for the sensitivity of their apparatus, and we find satisfactory agreement for C60 scattering with Ar.

Quantifying the impact of upscaled parameters on radionuclide transport in three-dimensional fracture-matrix systems

Assessing the long-term safety of geological repositories for high-level radioactive waste is critically dependent on understanding radionuclide transport in multi-scale fractured rocks. This study explores the influence of upscaled parameters on radionuclide movement within a three-dimensional fracture-matrix system using a discrete fracture-matrix (DFM) model. The developed numerical simulation workflow includes creating a random discrete fracture network, meshing of the fractures and matrix, assigning upscaled parameters, and conducting finite element simulations. We simulated the spatiotemporal evolution of radionuclide concentrations in the fractures and matrix over a century, revealing significant spatial heterogeneity driven by a heterogeneous seepage field. Employing geostatistics-based upscaling methods, we predicted the effective ranges of crucial solute transport parameters at the field scale. The matrix diffusion coefficient, matrix distribution coefficient, and longitudinal dispersivity were upscaled by factors of 2.0–3.0, 2.5–4.0, and 10–104, respectively, based on laboratory-scale measurements. Incorporating these upscaled parameters into the DFM model, we analyzed their impact on radionuclide transport. Our findings demonstrate that an upscaled matrix diffusion coefficient and matrix distribution coefficient result in a delayed transport of radionuclides in fractures by enhancing mass transfer between the fractures and rock matrix, while an upscaled longitudinal dispersivity accelerates transport by advancing the positions of concentration peaks. Sensitivity analysis revealed that the matrix distribution coefficient is the most impactful, followed by dispersivity and matrix diffusion coefficient. These insights are important for minimizing parameter uncertainties and enhancing the accuracy of predictions concerning radionuclide transport in multi-scale fractured rocks.

In-depth analysis of MgAl layered double oxide AC composite for sulfate removal from United Arab Emirates Ground Water: Synthesis optimization, fixed-bed performance, and economic feasibility

Excessive sulfate (SO42−) concentrations in groundwater pose health and environmental risks that require effective treatment strategies. This study focuses on optimizing the synthesis conditions of activated carbon doped MgAl layered double oxide (MgAl LDO/AC) and addresses the treatment of SO42− contamination in United Arab Emirates (UAE) groundwater. The study delves into key parameters such as the Mg/Al molar ratio and calcination temperature, unveiling optimal adsorption performance at a 3:1 M ratio and 500 ℃ calcination. The optimized MgAl LDO/AC(3:1/500 ℃) demonstrated notable selectivity for SO42− in the presence of NO3–, while exhibiting competition with H2PO4−, CO32−, HCO3−, and Cl−. In fixed-bed column studies, optimal performance was achieved with a lower influent concentration (50 mg/L), longer bed height (10 cm), and reduced flow rate (5 mL/min), resulting in a prolonged saturation time of 31.7 h, adsorption capacity of 429.5 mg/g, reduced axial dispersion coefficient, and enhanced mass transfer process. The real groundwater treatment demonstrated the composite's efficiency in reducing SO42− from 2606.6 to 817.5 mg/L, with additional removal of Cl− and NO3− ions, emphasizing its potential as an efficient pretreatment stage for highly contaminated and saline groundwater. Material characterization revealed the dominance of the chemical adsorption process of SO42− including surface complexation and ion exchange. Economic feasibility evaluation underscored the practicality of the composite, indicating its potential application in real plants with a cost below 20 US$/kg. Overall, MgAl LDO/AC(3:1/500℃) stands as a promising and cost-effective solution for removing SO42− in real-world water treatment scenarios, especially in regions facing water challenges.

Influence of cladding tube structure on transmission characteristics of negative curvature terahertz fiber

A novel type of polarization negative curvature terahertz fiber has been designed, which has a cladding region composed of two long semi-circular cladding tubes in the horizontal direction and four long semi-elliptical cladding tubes in the oblique direction. The optimal fiber dimensions are determined to investigate the internal relationship between polarization characteristics and fiber cladding structure. The transmission performances of the negative curvature fiber are investigated by varying the thickness of fiber cladding tubes and adjusting the structural characteristics of cladding tubes in different directions. Relatively good transmission performances can be obtained with a cladding tube thickness of 80 μm. The birefringence can be stably maintained at the order of 10−4, and the confinement loss of the x-polarized mode at 2.55 THz is 0.036 dB cm−1. Moreover, the dispersion coefficient of the two polarized modes is stable between ±0.6 ps (THz·cm)−1 in the 2.3–2.6 THz band. The bent performance of the designed fiber at 2.52 THz is also discussed. The results show that the fiber has low bending sensitivity, and can still maintain excellent birefringence and low confinement loss in the bending state. For the y polarization, the birefringence can be basically stabilized at the order of 10−4 within a bending radius of 10–60 cm.

Laboratory determination of hydrogen/methane dispersion in rock cores for underground hydrogen storage

Underground hydrogen storage in saline aquifers is a promising way to store large amounts of energy. Utilization of gas cushion enhances the deliverability of the storage and increases the volume of recovery gas. The key factor for the cushion characterization is cushion gas and storage gas mixing which can be used for simulation of mixing zone evolution. In this work coreflooding setup utilizing Raman spectroscopy is built and used for dispersion coefficient determination. Berea sandstone rock core is used as a test sample for setup validation and core entry/exit effects estimation. Dispersion for hydrogen and methane as displacing fluids is determined for 4 locations perspective for hydrogen storage in Poland is found. Reservoir structures most suitable for pure hydrogen or hydrogen/methane blend storage are selected.

Analysis of time-fractional Schrödinger equation with group velocity dispersion coefficients and second-order spatiotemporal effects: a new Kudryashov approach

Analysis of time-fractional Schrödinger equation with group velocity dispersion coefficients and second-order spatiotemporal effects: a new Kudryashov approach

Water quality monitoring and modeling for an urban storm drainage channel in Thane, India.

The absence of a sewer system and inadequate wastewater treatment plants results in a discharge of untreated wastewater to the urban drainage channels and pollutes receiving waters. Field visits were carried out to observe water quality parameters such as dissolved oxygen (DO), biochemical oxygen demand (BOD), and chemical oxygen demand (COD) in an urban drainage system (Kolshet drain) in Thane City, Mumbai Metropolitan Region, India. Dye-tracing studies using rhodamine WT dye were used for computing the velocity, discharge, and dispersion coefficient of the drain. The data analysis shows that the BOD and COD values in the drain are higher than the permissible limits (30mg L-1 for BOD and 250mg L-1 for COD), which is not suitable for disposal to any receiving water body. Also, the DO was less than the permissible limit of a minimum of 3mg L-1 (for the survival of aquatic life). It is seen that the higher BOD load significantly reduced the DO throughout the drain. The Water Quality Analysis Simulation Program (WASP 8.32, 2019) developed by the US Environmental Protection Agency (USEPA) has been used for the simulation of the DO and BOD in the drainage channel. The model simulates an appropriate estimate of the expected variation of DO and BOD at points of interest. The modeling for the Kolshet drain is expected to enable better estimates of the wastewater parameters and the pollution transport in the drain for planning purposes.

Comparative analysis of tracer studies in the determination of longitudinal dispersion coefficient.

The research presented in this paper is to determine the best tracer studies that will give acceptable estimates of longitudinal dispersion coefficient for Orashi river using rhodamine WT dye and sodium chloride as water tracer. Estimated results obtained for longitudinal dispersion coefficient for the case of rhodamine WT experiment ranges between 71 and 104.4 m2s-1 while that of sodium chloride experiment ranges between 20.1 and 34.71 m2s-1. These results revealed lower dispersion coefficient using sodium chloride as water tracer (WT) indicating that for larger rivers, sodium chloride should not be used as water tracer. The usage of sodium chloride as water tracer in the estimation of longitudinal dispersion coefficient is recommended in smaller streams as NaCl is relatively conservative. The established equations for both cases of investigation are proving satisfactory upon validation as degree of accuracy of 100.0% was obtained using discrepancy ratio (Dr). Standard error (SE), normal mean error (NME) and mean multiplication error (MME) of the developed equations is better when compared with other existing equations. However, Equation (17) is satisfactorily recommended.

Physicochemical and Heavy Metal Analysis of Industrial Pollution Model Calibration and Validation Using Field Measurements

This study assessed industrial pollution impacts on rivers near Port Harcourt, Nigeria using physicochemical analysis, heavy metal data, and contaminant transport modeling. Key findings show the rivers are severely degraded with extreme levels of heavy metals, low dissolved oxygen, high conductivity, nutrients, and fecal bacteria exceeding water quality guidelines. Uncontrolled effluent discharges from industries are primarily responsible. A first-order advection-diffusion model reliably predicted the rapid initial dilution and slower downstream attenuation of metals like magnesium and cadmium. The model was successfully calibrated and validated using field measurements to determine key transport parameters including dispersion coefficients. The severe contamination indicates current effluent treatment and regulations are inadequate and require urgent strengthening to control sources, expand monitoring, remediate contamination, restore habitats, and protect ecosystem and public health. Sustained engagement of government, industry, communities and researchers is essential to devise integrated solutions that improve water quality. The modeling provides quantitative guidance on pollution impacts and mitigation needs. Further work should refine predictions, establish ecological thresholds, and validate model results with biomonitoring to support evidence-based, adaptive management.

DEVELOPMENT OF A MATHEMATICAL MODEL FOR ANALYSING THE HAZARDOUS IMPACT ON THE STATE OF GROUNDWATER IN CITY AGGLOMERATIONS FROM MISSILE AND ARTILLERY ATTACKS

The authors have developed a mathematical model for analysing the hazardous impact on the groundwater in urban agglomerations from missile and artillery attacks. The mathematical model consists of a system of four analytical dependencies. The first analytical dependence describes determining the area of groundwater intake from the groundwater level, considering the presence of artificial coatings, infiltration, evaporation, and transpiration, as well as the effect of evapotranspiration. The second dependence determines the area of influence of the missile and artillery danger from the type of weapon, the explosive charge, calibre (diameter), and territorial conditions, the key indicators of the content of which in the territory of the critical infrastructure object, which suffered damage, are further determined by expert calculation using natural samples of soils and groundwater. The third dependence determines the impact of harmful (polluting) substances on groundwater in the territory of the critical infrastructure object, which suffered damage, depending on the process of groundwater movement in the area of the emergency, taking into account the hydraulic pressure and water yield coefficient; the process of distribution of chemically dangerous substances in groundwater, taking into account the coefficient of hydrodynamic dispersion and the velocity of groundwater; convective diffusion of chemically hazardous substances, taking into account the kinetics of sorption. The fourth dependency allows us to choose an efficient concept for the organisation of groundwater monitoring on the territory of a critical infrastructure object that suffered damage based on the variation of formalised parameters for solving individual problems. The initial conditions of the mathematical model are related to the presence of chemically dangerous compounds in groundwater at the maximum permissible concentration level. The boundary conditions of the mathematical model relate to the non-overgrowth of consequences beyond the object level in terms of the number of victims. Keywords: mathematical model, groundwater, missile and artillery damage, critical infrastructure object, emergency prevention.

Why Stable Finite-Difference Schemes Can Converge to Different Solutions: Analysis for the Generalized Hopf Equation

The example of two families of finite-difference schemes shows that, in general, the numerical solution of the Riemann problem for the generalized Hopf equation depends on the finite-difference scheme. The numerical solution may differ both quantitatively and qualitatively. The reason for this is the nonuniqueness of the solution to the Riemann problem for the generalized Hopf equation. The numerical solution is unique in the case of a flow function with two inflection points if artificial dissipation and dispersion are introduced, i.e., the generalized Korteweg–de Vries-Burgers equation is considered. We propose a method for selecting coefficients of dissipation and dispersion. The method makes it possible to obtain a physically justified unique numerical solution. This solution is independent of the difference scheme.

Dispersion of artificial tracers in ventilated caves

Artificial CO2 was used as a tracer along ventilated karst conduits to infer airflow and investigate tracer dispersion. In the karst vadose zone, cave ventilation is an efficient mode of transport for heat, gases and aerosols and thus drives the spatial distribution of airborne particles. Modelling this airborne transport requires geometrical and physical parameters of the conduit system, including the cross-sectional areas, the airflow and average air speed, as well as the longitudinal dispersion coefficient which describes the spreading of a solute. Four gauging tests were carried out in one mine (artificial conduit) and two ventilated caves (natural conduits). In this paper, we demonstrate that it is possible to gain reliable airflow rates and geometric information of ventilated karst conduits using CO2 as a tracer. Airflow was gauged along two caves and one mine and compared with punctual measurements made with a hot-wire anemometer. Cross-sectional areas estimated with CO2 tests were compared with those measured in situ. Moreover, breakthrough curve (BTC) analysis displayed an accentuated tailing along the investigated natural conduits due to the presence of dispersive singularities which possibly enable aerosol deposition. The long tailing observed in Milandre and Longeaigue Caves is probably due to cross-section variations. A 1-D advection-dispersion model tested for these sites was unable to fit BTC tailing in natural conduits. In Baulmes artificial conduit, where long tailing is not observed, the dispersion coefficient has been estimated using Chatwin’s method, and compared with the prediction of Taylor’s theory. Despite the regular geometry of Baulmes Mine, Taylor’s correlation significantly underestimates the dispersion coefficient deduced from field data, showing the need for more theoretical work on turbulent dispersion in mines. This paper gives a first insight into air motion and matter dispersion along ventilated karst conduits, preparing for proper aerosol dispersion modelling.

Multiple solitons structures in optical fibers via PNLSE with a novel truncated M-derivative: modulated wave gain

This study introduces a novel truncated Mittage–Leffler (M)- proportional derivative (TMPD) and examines its impact on the perturbed nonlinear Schrödinger equation (PNLSE) that includes fourth-order dispersion and cubic-quintic nonlinearity. The TMPD-PNLSE is used to model light signals in nanofibers. In addition to dispersion and Kerr nonlinearity, which are characteristics of the NLSE, the PNLSE also exhibits self-steepening and self-phase modulation effects. The unified method is implemented to derive exact solutions for the model equation. These solutions provide a variety of phenomena; including breathers, geometric chaos, and complex solitons. The solutions also exhibit numerous structures, such as geometric chaos, where undulated M-shaped and M-shaped solitons are embedded. The modulation instability is analyzed, finding that it is triggered when the coefficient of the fourth-order dispersion surpasses a critical value.

Water Quality Modelling with Industrial and Domestic Point Source Pollution : a Study Case of Cikakembang River, Majalaya District

Rapid industrial development is one of the leading causes of environmental degradation. The textile industries and the domestic activities in Majalaya District produce wastewater directly discharged into the Cikakembang River. As a result, the Cikakembang River’s water quality has decreased to the point that the water quality cannot be used for daily needs. This study modeled three main parameters in water quality modelling, namely Dissolved Oxygen (DO), Biological Oxygen Demand (BOD), and Chemical Oxygen Demand (COD). Using MATLAB, the three-water quality governing equations originating from the Advection-Dispersion Equation were solved using the Runge Kutte-4 discretization scheme. The numerical modelling was carried out along 2.36 km of the Cikakembang River. All water quality coefficients, such as the DO Saturation (DOsat), the Reaeration Rate (ka), the Dispersion Coefficient (D), the Deoxygenation Rate (kd), and the Decomposition Rate (kc), for the Cikakembang River were estimated using equations developed by existing studies. The estimation of ka and D coefficients requires hydraulic parameters, which in this study were estimated using the HEC-RAS simulation. Meanwhile, kd and kc values were obtained from the calibration and verification process. The Relative Root Mean Square Error (RRMSE) objective function was used to evaluate the results of water quality modelling at three sampling points. In the calibration process, the resultsof water quality modelling produced RRMSE values for the DO, BOD, and COD parameters of 1.99%, 0.36% and 0.92%, respectively. Meanwhile, for the verification process, the RRMSE values for the DO, BOD, and COD parameters are 1.95%, 1.02% and 1.86%. All water quality parameters produce small RRMSE values in the calibration and verification processes. Hence, the water quality model created has good accuracy and stability.