Multi-fluid Model Research Articles

Nuclear Meltdown Relocation and Core Catcher Analysis

Nuclear meltdown with the potential human and environmental harm is one of the major accident hazard (MAH) faced by nuclear power plants. Limiting (or entirely avoiding) criticality events are the main design strategies for reactors of generations 3½ and 4 (Gen3½ and Gen4). These include ensuring negative void and negative temperature coefficients (for both moderator and fuel) regardless of operational conditions, which provide a self-regulating mechanism that helps preventing accidents occurrence (i.e., to address safety and reliability aspects of Gen4’s goals). However, in severe accident scenarios (e.g. during loss-of-coolant, LOCA, events) where failure to extract heat from the reactor may lead to core degradation, strategies to mitigate reactor meltdown and relocation are critical in the design of safety protocols. This work aims to numerically investigate core relocation as an integrated multi-fluid and heat dynamics problem in which flow of melted materials (UO2, Zircaloy and graphite) are modelled through interface capturing/tracking methods. Two interface tracking/capturing methods were compared, the level-set volume of fluid method (VOF) in Ansys Fluent, and the compressive advection method (CAM) in Fluidity/ICFERST. Both methods are in good agreement for the core relocation simulation. An in-vessel core catcher (IVCC) of tungsten alloy was also proposed to demonstrate core degradation control strategy through cooling of the melted multi-materials. The IVCC was simulated with a multifluid model in Ansys Fluent, in a specified applied heat flux model. The thickness of the IVCC is 0.20 m and the heat flux used is 600 kW m-2. The tungsten material used was able to withstand both thermal and mechanical loads on the lower plenum by extracting decay heat from the corium.

Open-Source and Multi-Fluid Numerical Modeling of Proton Exchange Membrane Fuel Cell

Numerical modeling is a powerful tool for the virtual design and optimization of the next-generation proton exchange membrane fuel cells (PEMFC). While almost all of them are not open-source, which causes inconvenience and limits. In this paper, a three-dimensional, multi-component, multi-fluid, open-source model developed in the commercial CFD package (CFX) is used to investigate the species’ transport in a proton exchange membrane fuel cell. The model includes a complete fuel cell with both the seven-layer membrane-electrode-assembly and the gas flow channels and bipolar plates, which account for all major transport phenomena. In the porous medium, liquid water transport is dominant by the capillary pressure gradient; momentum loss describes the Darcy equation; and mass transfer between phases by a nonequilibrium phase change model. Multi-component gas phases are governed by convection and diffusion. Moreover, diffusion is the predominant transport mechanism for dissolved water between the membrane and catalyst layers. Consequently, the code of this model is shared on GitHub to provide a starting point and inspire further development and optimization.

Numerical Modeling of Water Jet Plunging in Molten Heavy Metal Pool

The hydrodynamic and thermal interaction of water with the high-temperature melt of a heavy metal was studied via the Volume-of-Fluid (VOF) method formulated for three immiscible phases (liquid melt, water, and water vapor), with account for phase changes. The VOF method relies on a first-principle description of phase interactions, including drag, heat transfer, and water evaporation, in contrast to multifluid models relying on empirical correlations. The verification of the VOF model implemented in OpenFOAM software was performed by solving one- and two-dimensional reference problems. Water jet penetration into a melt pool was first calculated in two-dimensional problem formulation, and the results were compared with analytical models and empirical correlations available, with emphasis on the effects of jet velocity and diameter. Three-dimensional simulations were performed in geometry, corresponding to known experiments performed in a narrow planar vessel with a semi-circular bottom. The VOF results obtained for water jet impact on molten heavy metal (lead–bismuth eutectic alloy at the temperature 820 K) are here presented for a water temperature of 298 K, jet diameter 6 mm, and jet velocity 6.2 m/s. Development of a cavity filled with a three-phase melt–water–vapor mixture is revealed, including its propagation down to the vessel bottom, with lateral displacement of melt, and subsequent detachment from the bottom due to gravitational settling of melt. The best agreement of predicted cavity depth, velocity, and aspect ratio with experiments (within 10%) was achieved at the stage of downward cavity propagation; at the later stages, the differences increased to about 30%. Adequacy of the numerical mesh containing about 5.6 million cells was demonstrated by comparing the penetration dynamics obtained on a sequence of meshes with the cell size ranging from 180 to 350 µm.

Numerical study of the feasibility of injecting CO2-containing off-gas in an ironmaking blast furnace

The injection of CO2-containing blast furnace top gas (BFTG) to replace reducing gas partially in an ironmaking blast furnace (BF) is a promising approach to achieve carbon neutralisation while potentially maintaining or improving BF performance. However, the feasible injection operating strategy for using CO2-containing BFTG and its effects on in-furnace phenomena are not well understood. In this study, a multi-fluid industrial-scale BF model with a tuyere injection submodel is developed to investigate the impacts of injecting CO2-containing BFTG at the BF tuyere on the in-furnace phenomena in terms of gas flow, temperature field, iron oxides distribution, and BF performance. The results show that: the maximum reducing gas replacement ratio by BFTG is ∼ 15 %, and a further increase leads to an unacceptable flame temperature. As more reducing gas is replaced by the BFTG, the start temperature of the intensified reduction for hematite and magnetite increases while those for wustite and iron decreases; the indirect reduction of iron oxides is improved in 1073–1273 K. The coke rate is increased by around 0.87 kg-coke/tHM with every 1 % reducing gas replaced by the BFTG. The top CO2 emission rate is decreased. This work provides a cost-effective tool to understand the flow-thermal-chemical behaviours inside a BF when CO2-containing gases are recycled in the BF ironmaking process.

The magnetised plasma Richtmyer–Meshkov instability: elastic collisions in an ion–electron multifluid plasma

The influence of an applied magnetic field on the collisional plasma Richtmyer–Meshkov instability (RMI) is investigated through numerical simulation. The instability is studied within the five-moment multifluid plasma model without any simplifying assumptions such as infinite speed of light, negligible electron inertia or quasineutrality. The plasma is composed of ion and electron fluids, and elastic collisions are modelled with the Braginskii transport coefficients. A collisional regime is investigated and the magnetic field is applied in the direction of shock propagation, which is perpendicular to the density interface. The primary instability is influenced by several terms affecting the evolution of circulation, the most significant of which are the baroclinic, magnetic field torque and intraspecies collisional terms. The applied magnetic field results in a reduction of interface perturbation growth, agreeing qualitatively with previous numerical simulations for the case of an ideal multifluid plasma RMI. The only major difference in the present case's instability mitigation by applied magnetic field, relative to the ideal case with applied magnetic field, is that the elastic collisions replace and obstruct the secondary vorticity suppression mechanism through collisional dissipation of vorticity. Additionally the collisions, influenced by the combination of self-generated and the applied magnetic field, introduce anisotropy to the problem. The primary suppression mechanism for the RMI is unchanged relative to the ideal case, i.e. the magnetic field torque resisting baroclinic deposition of vorticity in the ion fluid.

An alternative method to mimic mode conversion for ion cyclotron resonance heating

Ion cyclotron range of frequency waves in hot plasmas exhibit spatial dispersion effects and the wave equation takes the integro-differential form. Under the local plasma model assumption, the wave equation can be simplified to the differential form and adapts to the numerical scheme of the finite element method (FEM). Even though direct absorption of fast waves by ions and electrons can be described well by the local plasma model, linear mode conversion associated with non-local effects is absent. To deal with this issue, an alternative method is put forward in this paper where quasi-electrostatic fluid waves based on the multi-fluid warm plasma model are employed to take the place of ion Bernstein waves in mode conversion. On this basis, an interative fluid-kinetics (INTFLUK) code based on the FEM is developed for full-wave simulation in hot plasmas. Derivation of the wave equations as well as benchmarking of the INTFLUK code against other wave simulation codes are carried out. In both one- and two-dimensional cases, the validity of the INTFLUK code was verified by comparison of the wave field distributions and power deposition. As a useful illustration of the INTFLUK code including the scrape-off layer and a realistic antenna, the influence of the poloidal antenna phasing difference on ion cyclotron resonance heating is analyzed. Finally, it should be noted that the method in this paper has the potential to be extended to the three-dimensional case, which will be considered in the near future.

Electrostatic solitary waves in a bi-ion plasma with two suprathermal electron populations – application to Saturn’s magnetosphere

ABSTRACT Non-thermal particle distributions characterized by a high-energy tail are ubiquitous in space plasmas. They are usually described by a kappa distribution function, that has been shown to be an excellent fit in most real circumstances. Among other space missions, Cassini and Voyager have both recorded evidence of a coexistence of non-thermal electron populations (with different characteristics) in Saturn’s magnetosphere, and subsequent studies showed that these are well-described by using different tailor-fit realizations of the (parametrized) kappa distribution. Motivated by these observations we have formulated a multifluid plasma model incorporating two types of (positive) ions and two distinct kappa-distributed electron populations, in order to study electrostatic solitary waves (ESWs) in Saturn’s magnetosphere from first principles. Our analysis reveals that the spectral index (in fact, the κ parameter value related to the cold electron population mainly) is vital in explaining the difference among different types of non-linear structures. A comparison with spacecraft observations suggests that our theoretical model provides an efficient framework for the interpretation of ESW observations in Saturn’s magnetosphere. Our qualitative predictions may also apply to other planetary magnetospheres, where a similar multispecies plasma composition may be present.

Existence of Korteweg-de Vries solitons and relevance of relativistic effects in a dusty electron-ion plasma

Nonlinear effects in the propagation of perturbations in a dusty electron-ion plasma are studied, considering fully relativistic wave motion. A multifluid model is considered for the particles, from which a KdV equation can be derived. In general, two different soliton solutions are found depending on the kind of dispersion of the KdV equation. We study when the dispersion coefficient of this equation is positive. In this case, two kinds of behavior are possible, one associated with a slow wave mode, another with a fast wave mode. It is shown that, depending on the value of the system parameters, compressive and/or rarefactive solitons, or no soliton at all, can be found and that relativistic effects for ions are much more relevant than for electrons. It is also found that relativistic effects can strongly decrease the soliton amplitude for the slow mode, whereas for the fast mode they can lead to compressive-rarefactive soliton transitions and vice versa, depending on the dust charge density in both modes.

A Numerical Algorithm for Calculating Critical Points and Its Application to Predictive Mixture Models and Binary CO_2 Mixtures

The use of supercritical fluids in technical applications requires an accurate knowledge of their critical points. For mixtures, these can deviate significantly and without a linear dependency from the critical points of its individual pure components. Since even small amounts of admixture can have noticeable effects, this not only concerns blends of targeted compositions, but also unintentional mixtures for example caused by impurities. Within this work, a method for the calculation of critical points is presented which focuses on numerical robustness promoting a fast and reliable generation of results. Implemented into the thermodynamic property software TREND, with its mixture modeling capabilities, the method allows a flexible combination of different equations of state and mixture models which also includes predictive approaches. Against the background of an increasing relevance of mixtures based on supercritical CO_2 (sCO_2) for energy applications, critical lines are calculated and compared against experimental results for selected sCO_2-based mixtures recently considered for power plant applications. Herein, several combinations of equations of state (EoS) and mixture models are compared. Critical lines are calculated for the first time in this work with the combination of the multi-fluid mixture model with excess Gibbs energy (g^text {E}) models. It was found that the critical lines calculated with the combination of the multi-fluid mixture model with the g^text {E}-model COSMO-SAC yields good predictive results for the investigated CO_2 mixtures.

COCONUT-MF: Two-fluid ion-neutral global coronal modelling

Context. The global coronal model COCONUT (COolfluid COronal uNstrUcTured) was originally developed to replace semi-empirical models such as the Wang-Sheeley-Arge model in space weather forecasting chains in order to improve the physical accuracy of the predictions. This model has, however, several simplifications implemented in its formulation to allow for rapid convergence in an operational setting. These simplifications include the assumptions that the plasma is fully ionised, sufficiently collisional, and that quasi-neutrality holds, so that it can be modelled as a single fluid. This means that all interactions with the low-concentration neutral fluid in the corona, such as collisions or charge exchange, are neglected. Aims. In this paper, we have two goals. Firstly, we aim to introduce a novel multi-fluid global coronal model and validate it with simple cases (like a magnetic dipole) as well as with real data-driven applications. Secondly, we aim to investigate to what extent considering a single-fluid plasma in the global coronal model might affect the resulting plasma dynamics, and thus whether the assumptions on which the single-fluid coronal model is based are justified. Methods. We developed a multi-fluid global coronal model following the ideal magnetohydrodynamics (MHD) COCONUT model, COCONUT-MF, which resolves the ion and neutral fluid equations separately. While this model is still steady-state and thus does not resolve unsteady processes, it can account for resistivity, charge exchange, and chemical (ionisation and recombination) and collisional contributions due to the presence of the neutrals in the fluid equations. Results. We present the results of the ion-neutral COCONUT-MF modelling for a magnetic dipole, a minimum of solar activity case (August 1, 2008), and a solar maximum case (March 9, 2016). Through comparison with the ideal MHD results, we confirm that the resolved multi-fluid solver features are physical and also demonstrate the higher accuracy of the applied upwind numerical flux scheme compared to the one used in the original MHD model. Subsequently, we also repeat the multi-fluid simulations while excluding the charge exchange and the chemical and collisional terms to evaluate the effect these terms have on the resulting plasma dynamics. It is observed in numerical results that, despite the very low concentration of neutrals, they still do affect the flow field to a limited but non-negligible extent (up to 5 to 10% locally), with a higher impact being seen in the case of the solar maximum. It is also demonstrated that the collisional terms are primarily responsible for the neutrals adopting the electromagnetic profiles of the ions, while the charge exchange and chemical terms yield the largest thermal effects of the neutrals on the ion plasma. Despite the fact that the coronal plasma is generally assumed to be collisionless, our results show that there is sufficient collisionality in it to couple the two fluids. Conclusions. We present a novel multi-fluid global coronal model that can separately simulate the behaviour of the ion and neutral fluids. Using this model, we also show that in our set-up, in which the chromosphere is not considered and steady-state solutions are assumed, the presence of the neutrals affects the flow field, though to a limited extent. It is shown that this effect is larger when the flow field is more complex due to a higher magnetic activity. This analysis may change in the future when the global coronal model will be extended to include the lower atmospheric layers as well as terms to model coronal heating, radiation, and thermal conduction. To that end, the current model may need to be further calibrated to better represent the different layers of the atmosphere. We presume that the use of the proposed COCONUT-MF set-up will then be necessary and new numerical experiments will need to be performed in order to confirm this hypothesis.

Regulation of Proton–α Differential Flow by Compressive Fluctuations and Ion-scale Instabilities in the Solar Wind

Large-scale compressive slow-mode-like fluctuations can cause variations in the density, temperature, and magnetic-field magnitude in the solar wind. In addition, they also lead to fluctuations in the differential flow U pα between α-particles and protons (p), which is a common source of free energy for the driving of ion-scale instabilities. If the amplitude of the compressive fluctuations is sufficiently large, the fluctuating U pα intermittently drives the plasma across the instability threshold, leading to the excitation of ion-scale instabilities and thus the growth of corresponding ion-scale waves. The unstable waves scatter particles and reduce the average value of U pα . We propose that this “fluctuating-drift effect” maintains the average value of U pα well below the marginal instability threshold. We model the large-scale compressive fluctuations in the solar wind as long-wavelength slow-mode waves using a multi-fluid model. We numerically quantify the fluctuating-drift effect for the Alfvén/ion-cyclotron and fast-magnetosonic/whistler instabilities. We show that measurements of the proton–α differential flow and compressive fluctuations from the Wind spacecraft are consistent with our predictions for the fluctuating-drift effect. This effect creates a new channel for a direct cross-scale energy transfer from large-scale compressions to ion-scale fluctuations.

Unified fluid theory of the collisional thermal Farley–Buneman instability including magnetized multi-species ions

This paper develops a unified linear theory of cross field plasma instabilities, including the Farley–Buneman, electron thermal, and ion thermal instabilities, in spatially uniform collisional plasmas with partially unmagnetized multi-species ions. Collisional plasma instabilities in weakly ionized, highly dissipative, weakly magnetized plasmas play an important role in the lower Earth's ionosphere and may be of importance in other planetary ionospheres, stellar atmospheres, cometary tails, molecular clouds, accretion disks, etc. In the Earth's ionosphere, these collisional plasma instabilities cause intense electron heating. In the solar chromosphere, they can do the same—an effect originally suggested from spectroscopic observations and modeling. Based on a simplified 5-moment multi-fluid model, the theoretical analysis presented in this paper produces the linear dispersion relation for the combined Thermal Farley–Buneman Instability with an important long-wavelength limit analyzed in detail. This limit provides an easy interpretation of different instability drivers and wave dissipation. This analysis of instability, combined with simulations, will enable us to better understand plasma waves and turbulence in these commonly occurring collisional space plasmas.

Numerical simulations of underwater explosions using a compressible multi-fluid model

We present a novel solver for simulating compressible multi-fluid multiphase flow in underwater explosions (UNDEXs). The developed solver uses a modified version of Saurel's six-equation model, which includes an additional total mixture energy equation to resolve discrepancies in the thermodynamic states predicted under shock conditions. Additionally, we integrate a more precise stiffened gas equation of state (SG-EOS) that is determined using a novel method to enhance the accuracy of predicting experimental data based on a shock Hugoniot curve. We also propose a solution procedure using the modified Saurel's six-equation model on a three-dimensional (3D) structured Cartesian grid system. This involves discretizing the equation system using a Godunov scheme with a two-fluid Harten-Lax-van Leer-Contact approximate Riemann solver and a MUSCL-Hancock primitive scheme with total-variation-diminishing limiters, achieving a second-order extension. Both the dimensional splitting and fractional-step methods are utilized to model one-dimensional (1D) operators, splitting them into sequential operators. The modified model is validated for 1D and 3D problems, including the water–air shock tube, cavitation, shock–bubble interaction, and UNDEX problems in a free field, near a free surface, and near a rigid dam. Our simulations accurately predict the shockwave propagation, shock and free-surface interactions, cavitation evolution, and water jetting impact characteristics, exhibiting satisfactory agreement with those of previous studies. The proposed solver provides insight into the effects of UNDEXs on rigid structures, with potential applications in engineering and defense. The proposed method for determining the SG-EOS parameters can be applied to other areas of research involving high-pressure multi-phase flows.

Mysterious non-detection of HeI (23S) transit absorption of GJ436b

Abstract Possible reasons for the non-detection of absorption in the metastable HeI(23S) line at transit observations of warm Neptune GJ436b, in spite of the well pronounced strong absorption features measured earlier in Lyα for this planet, are investigated. We perform numeric simulations of the escaping upper atmosphere of this planet and its HeI(23S) triplet absorption with a global 3D multi-fluid self-consistent hydrodynamic model. By fitting the model parameters to the lowest detection level of absorption measurements, we constrain an upper limit the He/H abundance three times smaller than the solar value. We demonstrate that neither the significant changes of the stellar wind related with possible stellar coronal mass ejections (CMEs), or possible variations in the stellar ionization radiation, nor the presence of heavy trace elements have crucial effect on the absorption at the 10 830 Å line of HeI(23S) triplet. The main reason of weak signature is that the region populated by the absorbing metastable helium is rather small (<3Rp), as well as the small size of the planet itself, in comparison to the host star. We show that the radiation pressure force acting on the HeI(23S) atoms spreads them along the line of sight and around the planet, thus further reducing peak absorption.

Evaluation of numerical approaches for the simulation of water-flow in gravity-driven helical mineral separators

ABSTRACT Advancing the understanding of the fluid behavior in a mineral separation spiral has seen computational fluid dynamic models being validated using various flow properties. In this research article, capturing a focussed line of bubbles, which is commonly encountered in spirals, was utilized as a novel means to evaluate various numerical simulation approaches. To match experimental data, the simulations used a measured wall roughness, wall contact angle, and bubble size, in addition to a fluid domain geometry based on a 3D scan of a full-scale spiral. Through comparison with experimental data, the research investigated the effects of different numerical modeling approaches on the bubble line behavior, calibrated the unknown bubble mass flow rate, and performed a sensitivity analysis on the bubble diameter, wall roughness, and wall contact angle. The effects of changing the drag coefficient, the use of a simplified turbulence model, and the bubble–water interaction were investigated. The only model that allowed the formation of a bubble line was a two-phase Eulerian multi-fluid VOF model with the bubbles being included as a Lagrangian phase, with both drag and virtual mass forces modeled. The use of this model with a full-length domain of the spiral produced the first numerical evidence of a postulated tertiary radial flow in mineral separation spirals.

Equation for the Dynamic Viscosity of Propane for the Use in Mixture Models

In the present paper, a new equation for the dynamic viscosity of propane is presented, which is suitable for the application in mixture models. The dilute-gas contribution was adopted from Vogel and Herrmann (J Phys Chem Ref Data 45:043103, 2016). The residual part is an empirical approach designed following the example of thermodynamic Helmholtz equations of state. With this functional form, an approach is proposed, which will allow to combine pure-fluid equations in the manner of high precision Helmholtz equations of state in a multifluid mixture model in the future. The parameters of the equation are adjusted to experimental data, so that the data are mostly reproduced within their experimental uncertainty. The present equation is valid in a temperature range from 90 K to 525 K with a maximum pressure of 145 MPa.

The Mass Fractionation of Helium in the Escaping Atmosphere of HD 209458b* *Revised Manuscript on 2022 June 7

The absorption signals of metastable He in HD 209458b and several other exoplanets can be explained via an escaping atmosphere model with a subsolar He/H ratio. The low abundance of helium can be a result of planet formation if there is a small amount of helium in their primordial atmosphere. However, another possibility is that the low He/H ratio is caused by the process of mass fractionation of helium in the atmosphere. In order to investigate the effect of fractionation in the hydrogen-helium atmosphere, we developed a self-consistent multi-fluid 1D hydrodynamic model based on the well-known open-source MHD code PLUTO. Our simulations show that a lower He/H ratio can be produced spontaneously in the multi-fluid model. We further modeled the transmission spectra of He 10830 lines for HD 209458b in a broad parameter space. The transmission spectrum of the observation can be fitted in the condition of 1.80 times the X-ray and extreme-ultraviolet flux of the quiet Sun. Meanwhile, the ratio of the escaping flux of helium to hydrogen, F He/F H, is 0.039. Our results indicate that the mass fractionation of helium to hydrogen can naturally interpret the low He/H ratio required by the observation. Thus, in the escaping atmosphere of HD 209458b, decreasing the abundance of helium in the atmosphere is not needed even if its He abundance is similar to that of the Sun. The simulation presented in this work hints that in the escaping atmosphere, mass fractionation can also occur on other exoplanets, which needs to be explored further.

Effect of ion collision on separation between light and heavy ions in multi-component vacuum arc

In multi-component vacuum arc discharge, light ions and heavy ions usually have different spatial distributions of density and velocity. Previous research has suggested that the difference in spatial distribution of light and heavy ions is due to the mixing effect of cathode spot jet. However, in this work, the ion collision is found to be an important factor leading to the separation of light and heavy ions. In this paper, multi-fluid model is used to study the effect of ion collisions on separation mechanism in multi-component vacuum arc. The simulation results show that, during the jet mixing process, the collisions between different ions will reduce the velocity of light ions, and greatly increase the density and temperature. As a result, the pressure expansion of light ions is significantly enhanced. In addition, the collision between different ions will also increase the size of jet mixing region for light ions, which makes the plasma jet of light ions mixing more fully. These effects make their isotropic expansion dominant, and the ion density at the center is not much different from that at the edge. However for heavy ions, the collision between different ions has little influence on their movement. The pressure is far less than the inertia force, so the density of heavy ion mainly distributes along the convection direction, and the center is greater than the edge. This is the main separation mechanism of ion angular flux. It is also found there are three main factors leading to the separation of light and heavy ions: ion mass, ion density and ion temperature. The separation effect can be enhanced by increasing ion temperature, decreasing ion density and selecting electrode components with significant differences in elemental mass. This paper provides an insight into the mechanism of ion separation in multi-component vacuum arc.

Numerical Study on the Granular Flow and Heat Transfer of a Calcium Looping CO2 Capture System

AbstractThe calcium looping process has become a promising technology for reducing carbon dioxide emissions because of its lower energy consumption compared with other methods. A three‐dimensional multifluid model based on the kinetic theory was employed to study the movement of granules in the calciner. The results demonstrated that an increase in the rotation speed and inclination angle of the calciner led to a decrease in the residence time of the particles. Simultaneously, the probability of the particles being heated was reduced. Insufficiently calcined particles reduce the carbon capture capacity in the next cycle; therefore, suitable operating conditions and mechanism designs are very important.

The Impact of Multifluid Effects in the Solar Chromosphere on the Ponderomotive Force under SE and NEQ Ionization Conditions

The ponderomotive force has been suggested to be the main mechanism to produce the so-called first ionization potential (FIP) effect—the enrichment of low-FIP elements observed in the outer solar atmosphere, in the solar wind, and in solar energetic events. It is well known that the ionization of these elements occurs within the chromosphere. Therefore, this phenomenon is intimately tied to the plasma state in the chromosphere and the corona. For this study, we combine IRIS observations, a single-fluid 2.5D radiative magnetohydrodynamics (MHD) model of the solar atmosphere, including ion–neutral interaction effects and nonequilibrium (NEQ) ionization effects, and a novel multifluid multispecies numerical model (based on the Ebysus code). Nonthermal velocities of Si iv measured from IRIS spectra can provide an upper limit for the strength of any high-frequency Alfvén waves. With the single-fluid model, we investigate the possible impact of NEQ ionization within the region where the FIP may occur, as well as the plasma properties in those regions. These models suggest that regions with strongly enhanced network and type II spicules are possible sites of large ponderomotive forces. We use the plasma properties of the single-fluid MHD model and the IRIS observations to initialize our multifluid models to investigate the multifluid effects on the ponderomotive force associated with Alfvén waves. Our multifluid analysis reveals that collisions and NEQ ionization effects dramatically impact the behavior of the ponderomotive force in the chromosphere, and existing theories may need to be revisited.