Jaime Klapp

• Instituto Nacional de Investigaciones Nucleares

Reservoir management becomes increasingly critical as fields decline to a fully mature state. During this stage, engineers and managers must make decisions based on a limited set of field measurements (such as pressure and production rates). At the same time, up-to-date information concerning the reservoir’s geophysical characteristics and petroche...

Smoothed Particle Hydrodynamics (SPH) has become a promising tool for the simulation of fluids. Although too much research has been addressed to improve the method over the years, a comparison of the errors and consistency evolution when trying different approaches are still necessary to define the best scheme for practical applications. Here, a tw...

The adsorption of dibenzothiophene (DBT) on MoS 2 nanoparticles as a previous step to the catalytic activity in hydrodesul-furization (HDS) is studied with Dissipative Particle Dynamics (DPD) and Density Functional Theory (DFT) simulations. It is found that DBT exhibits both chemisorption and physisorption in its contact with the MoS 2 nanoparticle...

We have collected a database of more than 43,000 spectra of atmospheres of massive stars. These spectra have been generated with the CMFGEN code of Hillier & Miller (1998) by systematically varying stellar parameters: effective temperature, luminosity, metallicity and mass loss rate for stars from 9 to 120 solar masses (Zsargó et al. 2020) In this...

A Gaussian mixture model (GMM) was implemented to investigate the relationship between the liquid holdup (in various parts of the flow) and the pressure for different experimental realizations of high-viscosity gas–liquid flows. We considered a Newtonian fluid with a constant viscosity of 6 Pa s (600 cP) under a laboratory-controlled temperature. B...

Ground-based and satellite observations have revealed dust temperatures as low as ∼5 − 7 K in the centre of low-mass, pre-stellar cloud cores, where star formation takes place. However, external heating may rise the outer core temperatures up to ∼15 − 20 K. Such low temperatures at the centre of pre-stellar cores are a key factor to constrain the c...

In this paper we report experiments on the growth of dry foams and their rise in thin vertical pipes of different circular cross-sectional radii. Air injection at the bottom of the pipes is performed at a constant flow rate by means of a single capillary tube. The formation and rising of the foam was investigated for two different cases: (a) when t...

This work aims to analyse different injection configurations for the analysis of the emulsification process in a Y-junction staggered horizontal pipeline. The case study comprises a multiphase analysis between two liquids, one with high and the other with low viscosity. Through numerical simulations, it is intended to explain the behaviour and desc...

For this work, we condense current endeavors and improvements in the expansion of applications of the DualSPHysics code to nuclear reactor safety analysis, that includes the analysis of very complex multiphysical phenomena, involving, in some cases, a highly nonlinear deformation. Computational fluid dynamic (CFD) codes have been developed to analy...

This article condenses current endeavors and improvements in the expansion of applications of the DualSPHysics code to analyze heat transfer in a nuclear reactor core. This includes the essential conservation equations and certain physical considerations, particularly the thermal conductivity variable model, considering changes in the reference den...

Numerical modeling simulations and the use of high-performance computing are fundamental for detailed safety analysis, control and operation of a nuclear reactor, allowing the study and analysis of problems related to thermal-hydraulics, neutronic, and the dynamic of fluids that are involved in these systems. In this work, we introduce the basis fo...

The swirling secondary flow in curved pipes is studied in three-space dimensions using a weakly compressible Smoothed Particle Hydrodynamics (WCSPH) formulation coupled to new non-reflecting outflow boundary conditions. A large-eddy simulation (LES) model for turbulence is benchmarked with existing experimental data. After validation of the present...

Here we present a new self-consistent script to compute the equilibrium temperature of any configuration given in the article.

An experimental and numerical smoothed particle hydrodynamics (SPH) analysis was performed for the convective flow arising from a horizontal, thin cylindrical heat source enclosed in a glycerin-filled, slender enclosure at low Rayleigh numbers ($1.18\leq {\rm Ra}\leq 242$). Both the experiments and the SPH calculations were performed for positive (...

Aims.$ We present a database of 43,340 atmospheric models ($\sim$80,000 models at the conclusion of the project) for stars with stellar masses between 9 and 120 $M_{\odot}$, covering the region of the OB main-sequence and Wolf-Rayet (W-R) stars in the Hertzsprung--Russell (H--R) diagram. $Methods.$ The models were calculated using the ABACUS I supe...

Aims. We present a database of 43 340 atmospheric models (∼80 000 models at the conclusion of the project) for stars with stellar masses between 9 and 120 M⊙, covering the region of the OB main-sequence and Wolf-Rayet stars in the Hertzsprung-Russell diagram. Methods. The models were calculated using the ABACUS I supercomputer and the stellar atmo...

Numerical modeling simulations and the use of high-performance computing are fundamental for detailed safety analysis, control and operation of a nuclear reactor, allowing the study and analysis of problems related with thermal-hydraulics, neutronic and the dynamic of fluids which are involved in these systems. In this work we introduce the bases f...

We present the classical Bondi accretion theory for the case of non-isothermal accretion processes onto a supermassive black hole (SMBH), including the effects of X-ray heating and the radiation force due to electron scattering and spectral lines.The radiation field is calculated by considering an optically thick, geometrically thin, standard accre...

I make available this simple MMA script, to read and fast plotting the calculations made in https://iopscience.iop.org/article/10.3847/0067-0049/226/2/22/meta. Any question about its manipulation is welcome.

In this paper, we present a generalization of the classical Bondi accretion theory for the case of non-isothermal accretion processes onto a supermassive black hole (SMBH), including the effects of X-ray heating and the radiation force due to electron scattering and spectral lines. The radiation field is calculated by considering an optically thick...

We present three-dimensional calculations of spherically symmetric Bondi accretion onto a stationary supermassive black hole (SMBH) of mass 10 8 M ⊙ within a radial range of 0.02 − 10 pc, using a modified version of the smoothed particle hydrodynamics (SPH) gadget-2 code, which ensures approximate first-order consistency (i.e., second-order accurac...

The use of computer simulations techniques is an advantageous tool in order to evaluate and select the most appropriated site for radionuclides confinement. Modelling different scenarios allow to take decisions about which is the most safety place for the final repository. In this work, a bidimensional numerical simulation model for the analysis of...

We present three-dimensional calculations of spherically symmetric Bondi accretion onto a stationary supermassive black hole (SMBH) of mass $10^{8}$ $M_{\odot}$ within a radial range of $0.02-10$ pc, using a modified version of the smoothed particle hydrodynamics (SPH) \gad \sp code, which ensures approximate first-order consistency (i.e., second-o...

The use of computer simulations techniques is an advantageous tool in order to evaluate and select the most appropriated site for radionuclides confinement. Modelling different scenarios allow to take decisions about which is the most safety place for the final repository. In this work, a bidimensional numerical simulation model for the analysis of...

In recent decades, the Tulancingo municipality (Mexico), has been affected by numerous extreme weather phenomena that caused heavy flooding events with severe damage to property and people. Most of the weather phenomena placed several dams under hydrologic risk. The hurricane “ Dean”, in 2007, led to the overflow of the dam “ La Esperanza”, generat...

In this paper, we derive an asymptotic expansion for the semi-infinite sum of Dirac-δ functions centered at discrete equidistant points defined by the set Na={x∈R:∃n∈N∧x=na,∀a>0}. The method relies on the Laplace transform of the semi-infinite sum of Dirac-δ functions. The derived series distribution takes the form of the Euler-Maclaurin summation...

We present a database of 25,000 atmospheric models (which is to grow to a grand total of 75000 models by the conclusion of the project) with stellar masses between 9 and 120 M\(_{\odot }\), covering the region of the OB main sequence and W-R stars in the H–R diagram. The models were calculated using the ABACUS I supercomputer and the stellar atmosp...

In this paper we have analyzed theoretically the super free fall of a near inviscid mass of liquid, which fills partially a small section of a very long vertical conical pipe. Through the use of a one-dimensional inviscid model, we describe the simultaneous and pecular motion of the two interphases of the liquid.

During development, blood vessel networks adapt to gradual changes in the oxygen required by surrounding tissue, shear stress, and mechanical stretch. The possible adaptations include remodeling the vessel network and thickening the walls of blood vessels. However, the treatment of several vascular diseases including cerebral arteriovenous malforma...

Currently, high performance computing is a very important tool in material science. The study of materials at the microscopic level for obtaining macroscopic properties from the behavior at atomic level is a big challenge, even more when a large number of atoms are involved in the analysis. One of the most important open source codes capable of per...

This chapter is a presentation of the programming philosophy behind a novel numerical particle method for the simulation of the interaction of compressible fluids and elastic structures, specifically designed to run in multiple Graphics Processing Units (GPUs). The code has been developed using the CUDA C Application Programming Interface (API) for...

We present the intensive calculations of digital tables for the radiative terms that appear in the energy and momentum equations used to simulate the accretion onto supermassive black holes (SMBHs) at the centers of galaxies. Cooling and heating rates are presented, calculated with a Spectral Energy Distribution constructed from: an accretion disk...

The statefinder parameters characterize the expansion history of the Universe in a model independent way. The standard method to estimate them is named Standard Cosmography (SC). In this paper we show how these estimations turn out to be highly biased and the standard deviations of their probability distributions very large. The Eis method was tail...

We present the experimental observations of the Faraday instability when the vibrated liquid is contained in a network of small square cells for exciting frequencies in the range \(10\le F\le 24\) Hz. A sweep of the parameter space has been performed to investigate the amplitudes and frequencies of the driving force for which different patterns for...

We study the consistency and convergence of smoothed particle hydrodynamics (SPH), as a function of the interpolation parameters, namely the number of particles $N$, the number of neighbors $n$, and the smoothing length $h$, using simulations of the collapse and fragmentation of protostellar rotating cores. The calculations are made using a modifie...

We study the consistency and convergence of smoothed particle hydrodynamics (SPH), as a function of the interpolation parameters, namely the number of particles $N$, the number of neighbors $n$, and the smoothing length $h$, using simulations of the collapse and fragmentation of protostellar rotating cores. The calculations are made using a modifie...

The deformation of a thin-walled vertical tube, filled with a liquid or a cohesionless granular material is investigated theoretically and experimentally. Experiments with an overload and without it were made with latex tubes filled with water or spherical glass beads and the results were compared with the theoretical profile derived from the Janss...

Non equilibrium coarse – grained, dissipative particle dynamics simulations of complex fluids, made up of polymer brushes tethered to planar surfaces immersed in a solvent yield non monotonic behavior of the friction coefficient as a function of the polymer grating density on the substrates, , while the viscosity shows a monotonically increasing d...

Non equilibrium coarse grained, dissipative particle dynamics simulations of complex fluids, made up of polymer brushes tethered to planar surfaces immersed in a solvent yield non monotonic behavior of the friction coefficient as a function of the polymer grating density on the substrates, \Gamma, while the viscosity shows a monotonically increasin...

In this paper the problem of consistency of smoothed particle hydrodynamics (SPH) is solved. A novel error analysis is developed in $n$-dimensional space using the Poisson summation formula, which enables the treatment of the kernel and particle approximation errors in combined fashion. New consistency integral relations are derived for the particl...

We present digital tables for the radiative terms that appear in the energy and momentum equations used to simulate the accretion onto supermassive black holes (SMBHs) in the center of galaxies. Cooling and heating rates and radiative accelerations are calculated with two different Spectral Energy Distributions (SEDs). One SED is composed of an acc...

With the use of simulated supernova catalogs, we show that the statefinder parameters turn out to be poorly and biased estimated by standard cosmography. To this end, we compute their standard deviations and several bias statistics on cosmologies near the concordance model, demonstrating that these are very large, making standard cosmography unsuit...

In this paper we introduce a correlation for the trajectories of sand jets, of a non-cohesive granular material, emerging from vertical sidewall orifices of diameter D and wall thickness w. A contrast with water jet in similar configurations has been performed. We found that the theoretical trajectories agree well with the experimental ones.

In this paper, we derive an asymptotic expansion for the semi-infinite sum of Dirac-𝛿 functions centered at discrete equidistant points defined by the set Na = {x ∈ R ∶ ∃n ∈ N ∧ x = na, ∀a > 0}. The method relies on the Laplace transform of the semi-infinite sum ofDirac-𝛿 functions. The derived series distribution takes the form of the Euler-Maclau...

The problem of consistency of smoothed particle hydrodynamics (SPH) has demanded considerable attention in the past few years due to the ever increasing number of applications of the method in many areas of science and engineering. A loss of consistency leads to an inevitable loss of approximation accuracy. In this paper, we revisit the issue of SP...

Dam safety is an issue that affects directly or indirectly all society sectors. Up to now, Mexico does not have a proper federal or state legislation to evaluate dam safety, thus it is difficult to assign liability when total or partial dam failure occurs or to prevent failure by programming cost-effective dam supervision. Dam safety risk analysis...

Fluid and composition dispersion in a porous media plays a relevant role in some industrial processes. The proper characterization of the porous media and the dynamics of the involved fluids are key parameters for the study of some industrial processes. This characterization is a challenge for the numerical methods community. The SPH open-source co...

In this work we present a programming philosophy and a template code for achieving computational scalability when using multiple graphics processing units (GPUs) in the numerical solution of any mathematical system of equations found in continuum dynamic simulations. The programming philosophy exploits the principal characteristics of the GPU hardw...

The results described in this work are part of a larger project. The long term goal of this project is to help physicians predict the hemodynamic changes, and associated risks, caused by different treatment options for brain arteriovenous malformations. First, we need to build a model of the vascular architecture of each specific patient. Our appro...

The pressure-driven slurry flow of heavy oil in a horizontal pipe is investigated experimentally and numerically for Reynolds numbers in the range 44–805, solid concentrations by weight between 1 and 12%, and mean slurry velocities of ∼ 0.2–2.3 m s . A three-dimensional, algebraic slip mixture (ASM) model is used as part of the CFD software FLUENT...

A smoothed particle hydrodynamics (SPH) model is presented for simulating the decay chain transport of radionuclides in confined aqueous solutions. The SPH formulation is based on the open-source parallel code DualSPHysics extended to solve the advective-diffusion equation for the evolution of the concentration field coupled to the fluid-dynamic eq...

We report experiments performed to describe the behavior of the experimental mass flow rate of cohesionless granular material, mβexpt, through circular orifices of diameter D made on sidewalls of tilted bins. In such experiments, the influence of the wall thickness of the bin, w, and the tilt angle with respect to the vertical, β, were also regarde...

En este trabajo se presenta un análisis de la extracción de un fluido inmiscible saturado en un medio poroso homogéneo utilizando Dinámica Computacional de Fluidos (CFD) con el método Hidrodinámica de Partículas Suavizadas (SPH). El flujo de fluidos con múltiples propiedades a través de sólidos porosos ocurre en una gran variedad de procesos natura...

We test here the first stage of a route of modifications to be applied to the public GADGET2 code for dynamically identifying accretion centers during the collision process of two adjacent and identical gas cores. Each colliding core has a uniform density profile and rigid body rotation; its mass and size have been chosen to represent the observed...

We test here the first stage of a route of modifications to be applied to the public GADGET2 code for dynamically identifying accretion centers during the collision process of two adjacent and identical gas cores. Each colliding core has a uniform density profile and rigid body rotation; its mass and size have been chosen to represent the observed...

The rapid evaporation and explosive boiling of a van der Waals (vdW) liquid drop in microgravity is simulated numerically in two-space dimensions using the method of smoothed particle hydrodynamics. The numerical approach is fully adaptive and incorporates the effects of surface tension, latent heat, mass transfer across the interface, and liquid-v...

Multiphase flows in porous media have a relevant role on the analysis of many industrial activities. The velocity, dispersion, and displacement of fluids in a porous media are key parameters for processes such as pollutant transport, mobile reactive beds, oil recovery, etc. A multiphase SPH model that can be used to simulate miscible and immiscible...

In this work we have analyzed experimentally the lateral mass outflow rate (m) over dot, for cohesionless granular solids (coarse grains) through circular orifices of diameter D made on side walls of bins. Experiments were performed to determine the influence of the wall thickness of the bin w, and of the grain diameter d on (m) over dot. Geometric...

Efficient and detailed visualization of fluid flow simulations through complex meso-porous structures are fundamental for many applications in different areas such as medicine, biotechnology, oil recovery procedures, industry applications, environmental science and design of new intelligent and efficient meso-porous materials. Here we present the v...

This chapter presents an overview of the equations describing the flow of multiphase and multicomponent fluids through fractured and unfractured porous media using the framework of continuum mixture theory. The model equations and constraint relationships are described by steps of increasing level of complexity. We first describe the governing equa...

A numerical simulation of water flow through a Venturi tube was made with the DualSPHysics code, which uses the Smoothed Particle Hydrodynamics (SPH) method. The dimensions of the simulated system are equal to the laboratory experimental setup. The experimental data were measured in the laboratory using a rotameter and a mercury manometer. The expe...

We study numerically liquid-vapor phase separation in two-dimensional, nonisothermal, van der Waals (vdW) liquid drops using the method of smoothed particle hydrodynamics (SPH). In contrast to previous SPH simulations of drop formation, our approach is fully adaptive and follows the diffuse-interface model for a single-component fluid, where a reve...

We investigate the thermodynamics of general fluids that have the constriction that their pressure is constant. For example, this happens in the case of pure dust matter, for which the pressure vanishes and also in the case of standard dark matter phenomenology. Assuming a finite non-zero pressure, the corresponding dynamics is richer than one naiv...

The environmental fluid dynamics provides a comprehensive overview of the basic principles, it emphasizes the relevance of environmental fluid dynamics research in society, public policy, infrastructure, quality of life, security, and the law. It then discusses established and emerging focus areas. As communities face existential challenges posed b...

The aim of this work was to simulate the transport of uranium in the unsaturated zone of an experimental parcel located in the community of San Cayetano, State of Mexico. The implanted cultivation is corn, fertilized with granulate triple superphosphate. During the transport of fertilizers through the unsaturated media, the physicochemical processe...

The continuously soap film tunnel is a device suitable for experimental studies of the hydrodynamic evaluation of cross sections. The velocity of the undisturbed film is among the important flow parameters of these particular devices. This paper suggests an indirect method for quickly estimating the velocity of vertically falling soap films.

The main goal of this study is to simulate fluid flow across a fractured medium and to visualize its motion as a function of several parameters such as the tortuosity, the inlet pressure and the geometry of the fracture. Using the concept of double porosity, we have developed a hybrid model based on the Finite Element Method. The hydraulic characte...

The aim of this paper is to present a set of numerical simulations of a penetrating collision, in which a small gas core (the bullet) penetrates a larger gas core (the target). In the target core, the gravitational collapse is supposed to be ongoing before the collision. Each colliding core has a uniform density profile and rigid body rotation; bes...

We review the hydrodynamics of the dark sector components in Cosmology. For this purpose we use the approach of Newtonian gravitational instability, and thereafter we add corrections to arrive to a full relativistic description. In Cosmology and Astrophysics, it is usual to decompose the dark sector into two species, dark matter and dark energy. We...

We study numerically liquid-vapor phase separation in two-dimensional, nonisothermal, van der Waals (vdW) liquid drops using the method of smoothed particle hydrodynamics (SPH). In contrast to previous SPH simulations of drop formation, our approach is fully adaptive and follows the diffuse-interface model for a single-component fluid, where a reve...

Using the data obtained previously from Fabry-Perot interferometry, we study the orbital characteristics of the interacting pair of galaxies KPG 302 with the aim to estimate a possible interaction history, the conditions necessary for the spiral arm formation, and initial satellite mass. We found by performing N-body/smoothed particle hydrodynamics...

Virtually all economic sectors as well as many public and private activities are affected in some measure by changes in weather and climate. Uncertainties in the scope and severity of these changes pose financial and social risks for individuals, businesses, and government agencies, with direct influence on food security and production, transport,...

The fluid flow through saturated and non-saturated homogeneous porous media is studied numerically using a modified version of a Smoothed Particle Hydrodynamics (SPH) code. The modifications implemented in the original SPH code to model the incompressible flow at low Reynolds numbers through a porous medium are described. The performance of the mod...

We investigate the details of protostellar mass accretion, \(\dot{M}\), during the collapse of isolated, initially uniformly rotating, low-mass cores, using hydrodynamic models of star formation. The assumption of rigid rotation is supported by recent observations that there is no apparent correlation between the level of turbulence and fragmentati...

In this work, we study the dynamical behaviour of As(V) and Se(IV) absorption in a biofilter through a mathematical simulation, comparing dimensions, flux, and removal percentage in packed columns. From the numerical simulation we obtained breakthrough curves. When comparing the experimental and numerical breakthrough curves, the best correlation g...

Recent observations indicate that there is no correlation between the level of turbulence and fragmentation in detected protostellar cores, suggesting that turbulence works mainly before gravitationally bound prestellar cores form and that their inner parts are likely to be velocity coherent. Based on this evidence, we simulate the collapse and fra...

In this paper we present a set of numerical simulations designed to study the interaction process of H II molecular clouds. For the initial conditions we assume head-on and oblique collisions of binary identical clouds placed adjacent to one another, with their surfaces just in contact. The colliding initial clouds are uniform density molecular gas...

We undertake the investigation of sheared polymer chains grafted on flat surfaces to model liposomes covered with polyethylene glycol brushes as a case study for the mechanisms of efficient drug delivery in biologically relevant situations, for example, as carriers for topical treatments of illnesses in the human vasculature. For these applications...

The method of Smoothed Particle Hydrodynamics (SPH) has been widely studied and implemented for a large variety of problems, ranging from astrophysics to fluid dynamics and elasticity problems in solids. However, the method is known to have several deficiencies and discrepancies in comparison with traditional mesh-based codes. In particular, there...

In this chapter we use the method of Smoothed Particle Hydrodynamics (SPH) to study the number and properties of accretion centres formed when a molecular gas cloud collapses, starting with initial conditions corresponding either to a turbulent or a rigidly rotating sphere. To do so we use a modified version of the SPH code GADGET-2, which is capab...

Transport simulation of radioactive contaminants in fluids through saturated porous media provides a powerful tool to prevent the risk they could represent to the environment. This kind of waste is stored in containers. These containers are collocated in subterranean places for being confined. Proper election of those places requires the appropriat...

A continuous fixed bed study was carried out using the non-living biomass Lemna minor as a biosorbent for the removal of Se(IV) from an aqueous solution. A 3D numerical model was constructed for solving the Navier–Stokes–Brinkman and mass transport equations using the finite element technique with 161,764 tetrahedral elements. Experimental and nume...

The objective of this chapter is to review the importance of fluid dynamics research and its impact on science and technology. Here we consider four particular areas of study, namely environmental fluid mechanics, turbulence, nano- and microfluids, and biofluid dynamics, with deeper emphasis on environmental flows. Each of these topics is illustrat...

The confinement of radioactive waste (radionuclides) in underground installations has to take into account its influence on the environment, the solvent action and the waste groundwater drag. This work evaluates by computer simulations how radionuclides migrate through the subsurface of a typical site in Mexico. The simulations show preferential ro...

We review the role of fluids in cosmology by first introducing them in General Relativity and then by applying them to a FRW Universe's model. We describe how relativistic and non-relativistic components evolve in the background dynamics. We also introduce scalar fields to show that they are able to yield an inflationary dynamics at very early time...

A fixed bed study was carried out using the non-living biomasses Eichhornia crassipes and Lemna minor as a biosorbent for the removal of selenium from an aqueous solution. A 3D model, capable to represent the real system, was configured using the Navier Stokes, Brinkman and mass transport equations. Experimental and numerical results were compared...

Sand flowing through the constriction of an hourglass or jumping on a vibrating plate is fluidized in the sense that it moves analogously to a fluid. Dense flows of grains driven by gravity down inclines occur in nature and in industrial processes. Natural examples include rock avalanches and landslides. Applications are found in the chemical, phar...

In this work we study the tertiary structure of ionic surfactants when the pH in the system is modified using electrostatic dissipative particle dynamics simulations (DPD). The dependence with pH and kind of surfactant is presented. Our simulations reproduce the experimental behavior reported in the literature. The scaling for the radius of gyratio...

The controlled deposition of a dispensed liquid drop onto the surface layer of another liquid is a process that is widely applied in the industry. In most applications, the deposition of stationary drops requires a micrometric translational approach to the surface. Here we describe a computer controlled apparatus that has been constructed to perfor...

This work presents the mathematical formalism of a numerical model used for the simulation of 226Ra migration and decay in saturated porous layers. The simulation methodology employs Darcy’s law for calculating the velocity field; it is subsequently used as input data for solving the transport equation. The latter includes advection, diffusion and...

Godunov-type methods relying on Riemann solvers have performed spectacularly well on supersonic compressible flows with sharp discontinuities as in the case of strong shocks. In contrast, the method of standard smoothed particle hydrodynamics (SPH) has been known to give a rather poor description of strong shock phenomena. Here we focus on the one-...

Although massive stars play a dominant role in shaping galactic structure and evolution, their origin and early evolution are not well understood mainly because of the lack of a good observational guidance. One major conceptual problem in massive star formation arises from the radiation pressure they exert on the surrounding dust and gas, which cou...

Migration and mass transfer of radionuclides through a saturated porous media taking into account the retention in the solid matrix as a function of the pH, is studied using the Darcy’s law equation for the effective velocity, and solving the contaminant transport diffusion equation within a porous media by the finite element method. The retardatio...

In this paper we present computer simulations of interstellar cloud collisions that for a given range of initial conditions could favor stellar cluster formation. We first construct a single spherical molecular hydrogen cloud with the Plummer radial density distribution with rigid rotation and an m=2 density perturbation. The isolated cloud collaps...

Experiments in natural porous media such as Eicchornia crassipes biomass for determining the sorption of arsenic are compared with numerical simulations done with the COMSOL Multiphysics code. The close agreement between the experimental and numerical results suggest that the theoretical model of hydrodynamic dispersion can be used to model the tra...

This paper shows the parallel implementation of the Linked Cell Method using CUDA and MPI. The so called Linked Cell method is employed in particle simulations with short range interactions. The method divides the physical domain into uniform sub domains while limiting the interactions to particles occupying the same cell and the flanking ones. In...

Numerical simulation of transport and radioactive decay of 226Ra as a constant product of 238U decay from a simulated storage facility containing uranium tailings is presented in this work. The simulation domain consists of six subsoil layers through which one of the uranium daughters 226Ra is migrating as well as decaying. The methodology consists...

Numerical simulation of transport and radioactive decay of 226Ra as a constant product of 238U decay from a simulated storage facility containing uranium tailings is presented in this work. The simulation domain consists of six subsoil layers through which one of the uranium daughters 226Ra is migrating as well as decaying. The methodology consists...