Diffusion Boundary Research Articles

Axisymmetric background-oriented schlieren measurement for cylindrical combustion flow in micro-rocket torches

A high-precision background-oriented schlieren (BOS) measurement technique was developed to analyze the density field of gases ejected from a micro-rocket torch in scramjet combustors. The BOS method was enhanced using an axisymmetric model and inverse Abel transforms, thereby allowing accurate density measurements in complex flow fields and addressing the limitations of traditional BOS applications. Validation tests confirmed the accuracy and stability of the BOS analysis, demonstrating its robustness against experimental noise and reliable density reconstruction. Experiments with varying equivalence ratios revealed significant effects on the ejected gas-density distribution and spread. Under fuel-rich conditions, the combustion temperature and molecular interactions increase, resulting in a lower density and greater jet expansion. This effect produced a clear boundary between the ejected gas and the surrounding atmosphere, whereas lean combustion conditions displayed more diffuse gas boundaries and instability, owing to the lower hydrogen concentration and combustion temperature. These observed behaviors were linked to Lewis number effects, where higher values under fuel-rich conditions enhanced combustion stability and maintained a more defined gas boundary. To further improve the accuracy of the density analysis, this study applied a modified Gladstone–Dale constant based on the in-flame gas composition. The BOS approach was optimized for angled fields of view and extended measurement areas. The results demonstrated that the BOS technique, particularly with the integration of axisymmetric modeling, provides an effective approach for capturing intricate flow structures in combustion, including spatial density gradients along both radial and axial directions.

Single-item continuous-review inventory models with random supplies

Abstract This paper analyzes single-item continuous-review inventory models with random supplies in which the inventory dynamic between orders is described by a diffusion process, and a long-term average cost criterion is used to evaluate decisions. The models in this class have general drift and diffusion coefficients and boundary points that are consistent with the notion that demand should tend to reduce the inventory level. Random yield is described by a (probability) transition function which depends on the inventory on hand and the nominal amount ordered; it is assumed to be a distribution with support in the interval determined by the order-from and the nominal order-to locations of the stock level. Using weak convergence arguments involving average expected occupation and ordering measures, conditions are given for the optimality of an (s, S) ordering policy in the general class of policies with finite expected cost. The characterization of the cost of an (s, S) policy as a function of two variables naturally leads to a nonlinear optimization problem over the stock levels s and S, and the existence of an optimizing pair $(s^*,S^*)$ is established under weak conditions. Thus, optimal policies of inventory models with random supplies can (easily) be numerically computed. The range of applicability of the optimality result is illustrated on several inventory models with random yields.

Strong turbulent flow in the subauroral region in the Antarctic can deteriorate satellite-based navigation signals

In the subauroral zone at the boundary of the auroral oval in the evening and night hours during geomagnetic disturbances, a narrow (about 1°–2°) and extended structure (several hours in longitude) is formed. It is known as a polarization jet (PJ) or the subauroral ion drift (SAID). The PJ/SAID is a fast westward ion drift and is one of the main signatures of a geomagnetic disturbance in the subauroral ionosphere at the altitudes of the F-layer, when the geomagnetic AE index reaches more than 500 nT. Plasma speed in the PJ/SAID can reach several kilometres per second, and the size of plasma irregularities inside it can reach scales from tens of meters to several hundred meters. Such high velocities and structured plasma can affect trans-ionospheric radio waves and lead to scintillations in the received signal. We show that at the moment of auroral activity intensification, an increase in the magnitude of phase scintillation index (σϕ) as well as loss of satellite signals lock were observed in the region of the PJ/SAID equatorward of the auroral oval over Dronning Maud Land (Queen Maud Land) in Antarctica. We find that fluctuations inside the PJ/SAID can lead to serious deterioration of radio communication or navigational services. We emphasize the importance of considering the geometry of the beam passing from the GNSS satellite to the receiver on the ground. We highlight the mutual contribution of the PJ/SAID and the diffuse aurora boundary, which are almost impossible to separate in practice. Our results demonstrate the importance of considering the subauroral zone, where very dynamic plasma formations can occur with a strong flow and various-scale irregularities inside that lead to serious interference in satellite communications.

Double-faced diffusive gradient in thin films sampler (df-DGT): Proposing an improved DGT sampler design for water deployments.

The Diffusive Gradients in Thin Films (DGT) technique has become the most widely used passive sampling method for inorganic compounds. This widespread adoption can be partly attributed to the development of new binding phases that facilitate the sampling of numerous analytes. In contrast, to date, the DGT sampler for inorganic compounds has not seen any significant design improvements. In this manuscript, a new design for the DGT sampler is proposed. The new design, referred to as the Double-Faced DGT (df-DGT) sampler, features dual sampling windows, enabling a twofold increase in analyte mass uptake compared to the conventional DGT sampler. The proposed sampler was characterized for Cd, Co, Mn, Ni, and Zn by performing the following tests: deployment curves, the effect of the diffusive boundary layer (DBL), pH, ionic strength and deployment in synthetic samplers. It was demonstrated that the df-DGT sampler can accumulate twice the mass over time compared to the conventional DGT sampler. The effects of the DBL, pH, and ionic strength on the measurements of Cd, Co, Mn, Ni, and Zn, when sampling with the df-DGT, were consistent with those previously reported for the conventional DGT sampler. When the df-DGT sampler and the DGT sampler were deployed simultaneously in synthetic samples with varying concentrations of Cd, Co, Mn, Ni, and Zn, no significant differences were observed (at the 95% confidence level) in the results obtained from both samplers. To the best of our knowledge, this is the first time a new DGT sampler, featuring conceptual innovations, is being proposed for sampling inorganic species in water. The proposed sampler is twice as effective in terms of mass uptake and is useful for short deployments or enhancing sensitivity. In the future, the application of this sampler could potentially be expanded to other uses, such as o-DGT.

CFD algorithm for moving boundary problems of isothermal drying and shrinkage: Case of prunes

A moving-boundary FEM model describing isothermal drying of fruit was employed as an inverse problem to estimate water diffusivity and peel resistance, including shrinkage. Water diffusivity and peel resistance were estimated using the Levenberg-Marquardt (L-M) optimisation algorithm based on the experimental drying data. The surface resistance is accounted as the sum of the peel and the diffusive boundary layer resistances, the latter being negligible compared to the former. The estimated peel resistance decreased by 86% as the drying temperature increased from 45 °C to 65 °C and by 44% as the drying temperature increases from 55 °C to 65 °C. The CFD optimisation model efficiently predicted the experimental water content and shrinkage.

Thermal enhancement using variable characteristics and tripartite diffusion features of solar aircraft wings in context of Reiner-Philippoff hybrid nanofluid passing through a parabolic trough solar collector

The application of solar energy to manufacturing processes and thermal power has changed dramatically. This time, the analysis of solar radiation and the possible combination of solar radiation and nanotechnology to increase the efficiency of solar-powered aircraft becomes a significant area of research. Solar-thermal applications often use parabolic trough solar collectors (PTSCs) to achieve high temperatures. This is a theoretical study that discuss the effects of hybrid nano-solid particles on the parabolic trough’s surface collector which is located inside the solar aircraft wings. For this investigation, the non-Newtonian Reiner-Philippoff model; a renowned and cutting-edge type of thermally efficient fluid as well as the stability triple diffusive boundary layer natural convective flow contained in a Darcy-Forchheimer porous medium have been taken into consideration. To verify the thermophysical behavior of the suggested model, unique hybrid nanoparticles copper along with zirconium dioxide with engine oil as base fluid (Cu+ZrO2/EO) has been added to the solar aircraft wings to improve the heat transfer performance. Scientists are currently investigating how to use solar radiation and nanotechnology to increase aircraft manufacturing. To investigate the phenomenon of heat transfer rate, a hybrid nanofluid stream is traveling in the direction of a parabolic-shaped trough found inside solar airplane wings. Solar thermal radiation was the term used to describe the heat transfer process. Heat source/sink phenomena, various slip boundary conditions, thermal radiative, chemical reaction, variable thermal conductivity, and variable molecular diffusivity are some of the special characteristics that are taken into account while assessing the heat transfer efficiency of airplane wings. With the utilization of the appropriate similarity transformations, partial diferential equations that represent the mathematical model can be decreased to ordinary diferential equations. To address the obtained dimensionless ordinary diferential equations, MATLAB’s Lobatto IIIA numerical technique was employed. By comparing the obtained results with the current literature, the credibility of the numerical results is ascertained. It’s vital to remember that velocity reduces as the Bingham number parameter increases. Elevation of thermal radiation enhances the functionality of aircraft wings that are exposed to heat transfer. Moreover, the rate of heat transfer is enhanced by positive variations in heat source and thermal conductivity effects.

Capacity and limitations of microfluidic flow to increase solute transport in three-dimensional cell cultures.

Culturing living cells in three-dimensional environments increases the biological relevance of laboratory experiments, but requires solutes to overcome a diffusion barrier to reach the centre of cellular constructs. We present a theoretical and numerical investigation that brings a mechanistic understanding of how microfluidic culture conditions, including chamber size, inlet fluid velocity and spatial confinement, affect solute distribution within three-dimensional cellular constructs. Contact with the chamber substrate reduces the maximally achievable construct radius by 15%. In practice, finite diffusion and convection kinetics in the microfluidic chamber further lower that limit. The benefits of external convection are greater if transport rates across diffusion-dominated areas are high. Those are omnipresent and include the diffusive boundary layer growing from the fluid-construct interface and regions near corners where fluid is recirculating. Such regions multiply the required convection to achieve a given solute penetration by up to 100, so chip designs ought to minimize them. Our results define conditions where complete solute transport into an avascular three-dimensional cell construct is achievable and applies to real chambers without needing to simulate their exact geometries.

Understanding ammonia's role in mitigating concentration polarization in anion-exchange membrane electrodialysis.

In processes such as electrodialysis, the applied electrical potential is constrained by concentration polarization at the membrane/solution interface. This polarization, which intensifies at higher current densities, impedes ion transport efficiency and may lead to problems such as salt precipitation, membrane degradation, and increased energy consumption. Therefore, understanding concentration polarization is essential for enhancing membrane performance, improving efficiency, and reducing operational costs. This study investigates the impact of ammonia buffer (NH4 +/NH3) on sulfate ion transport through anion-exchange membranes with a particular focus on limiting current density and concentration polarization under constant current conditions. The findings demonstrate that ammonia effectively eliminates concentration polarization and enhances chemical reactions at the membrane interface. Notably, the plateau region was absent in the current-voltage curves, as was the transition time in the chronopotentiograms. Furthermore, the Warburg impedance arc in the Nyquist plot of the electrochemical impedance spectra was absent in both limiting and overlimiting current regions and the increasing dominance of the Gerischer arc was registered. At an ammonia concentration of 0.1 M, the influence of concentration polarization on mass transport was effectively mitigated, enabling sulfate counterions to pass through the membrane without encountering concentration polarization. The addition of ammonia catalytically accelerated the proton-transfer reactions, which accelerated the water dissociation reaction at earlier polarization stages, preventing the formation of diffusion boundary layers and facilitating the transport of sulfate counterions through the AMX anion-exchange membrane. As a result, the polarization plateau disappeared and the overlimiting current region shifted closer to the ohmic region, all without affecting the limiting current density (j lim ).

PH, pOH shift and electroconvection of strong and weak electrolytes under ion concentration polarization

Ion concentration polarization (ICP) phenomenon near permselective membranes and associated electroconvection contributes greatly to ion enrichment, desalination, and biomolecular separation. Despite extensive studies on ion transport and fluid dynamics near the ion exchange membrane (IEM) surface, the influence of hydrolysis and buffer reactions on pH changes and electroconvection remains unclear. This study investigates the pH variations and electroconvection changes in different electrolytes under ICP, through numerical simulations in strong (NaCl) and weak electrolytes (Na2HPO4). Our findings reveal that the free ions produced by reactions increase the electrical conductivity, significantly boosting the current by approximately 14.82% in weak electrolyte in the overlimiting current (OLC) regime. The vortex velocity generated by electroconvective instability also increases by two times at the threshold voltage of 23 times the thermal voltage (25.8 mV). Additionally, the decrease in ion concentration during the ICP causes a significant pH and pOH surge in the quasi-equilibrium electric double layer (QE-EDL) and extended space charge (ESC) region, causing the water self-ionization constant (pKw) to surpass 14. Hydrolysis reactions release H+, reducing the pH surge by 0.5 and raising the OH− concentration in the diffusion boundary layer (DBL) region, resulting in a pOH of 6.5, which is higher than that of the bulk solution. In Na2HPO4 solution, weak acid dissociation reactions confine pH changes to the QE-EDL and ESC regions, maintaining pH stability in the DBL region. It was also found that at the boundary of the DBL region, the disruption of electro-neutrality results in the highest dissociation reaction rates. This research highlights the interplay of buffer reactions, hydrolysis, pH changes, and electroconvection near the IEM surface, with implications for applications involving ion transport and pH control.

Chemo-mechanical benchmark for phase-field approaches

Abstract Phase-field approaches have gained increasing popularity as a consequence of their ability to model complex coupled multi-physical problems. The efficient modeling of migrating diffuse phase boundaries is a fundamental characteristic. A notable advantage of phase-field methods is their ability to account for diverse physical driving forces for interfacial motion due to diffusive, mechanical, electro-chemical, and other processes. As a result of this versatility, phase-field methods are frequently employed in the fields of materials science, mechanics, and physics, and are continually undergoing development. To test the accuracy of these developments, it is indispensable to establish standardized benchmark tests, to ensure the thermodynamic consistency of studies carried out. This work presents a series of such tests based on chemo-elastic equilibrium states for Fe-C binary alloys, benchmarking the performance of a phase-field model with chemo-elastic coupling based on the grand potential density. Use of parameters for the Fe-C system from a Calphad database allows for the determination of the Gibbs free energy, thereby enabling the quantification of chemical driving forces. For a circular inclusion, the capillary driving force is derived on a geometrically motivated basis using the lever rule and expressed as a function of the chemical potential. These simulations contribute to the development of standardized benchmark tests that validate chemical, capillary, and mechanical driving forces separately and in combination. The present study compares phase-field simulation results with results from the analytic solution of chemo-elastic boundary value problems and the generalized Gibbs–Thomson equation.

Mathematical modeling of stationary thermopervaporation through hydrophobic membrane

The paper proposes a one-dimensional mathematical model of stationary thermopervaporation of water-organic mixture through a non-porous hydrophobic membrane. The driving force of the process is the difference in the temperature and concentration of the mixture components on both sides of the membrane. The model takes into account the difference in interaction between molecules of the liquid and vapor phases of the mixture components with the membrane matrix (equilibrium distribution coefficients), as well as the difference in the diffusion coefficients of the components in all areas. The problem of heat transfer is solved independently. The temperature distribution in layers of the membrane system (diffusion boundary layer, membrane and permeate) is determined. It is assumed that the evaporation front coincides with the working side of the membrane. In the general case, the boundary value problem is solved numerically by the shooting method. As a result, the distribution of the mass fraction of the organic component over the membrane cell is obtained. The dependences of the separation factor and the pervaporation separation index (PSI) on the main parameters of the problem are determined. It is demonstrated that the dependence of the PSI on the separation factor has extremal character. This allows to select optimal conditions for thermopervaporation for the given parameters of the membrane system. In the limiting case when the fluxes of the mixture components are equal to zero, the solution is obtained analytically. The maximum possible separation factor can be determined using an analytical solution. The present model was successfully verified using the literature experimental data on the thermopervaporation separation of butanol and ethanol aqueous solutions through the membranes of various types.

Diffusive gradients in thin-films (DGT) for in situ measurement of neonicotinoid insecticides (NNIs) in waters

Neonicotinoid insecticides (NNIs) are among the most widely-used insecticides, although their threat to non-target organisms has attracted attention in recent years. In this study, a diffusive gradient in thin-films (DGT) passive sampling technique was developed for in situ monitoring of time-weighted average (TWA) concentrations of NNIs in groundwater and wastewater. Systematic studies demonstrated that DGT with HLB as binding gels (HLB-DGT) is suitable for quantitative sampling of NNIs under a wide range of conditions, independent of pH (5–9.5), ionic strength (0.001–0.5 M) and dissolved organic matter (0–10 mg/L). The HLB-DGT performance was also independent of the typical groundwater ionic environments. The thicknesses of in-situ measured diffusive boundary layer were 0.35 and 0.25 mm in the groundwater and effluent, respectively. HLB-DGT can provide TWA concentrations over 14–18 days’ deployment with linear uptake in both groundwater and wastewater. Concentrations and occurrence patterns of NNIs obtained by HLB-DGT were consistent with those measured from grab samples. The median TWA concentration of NNIs was 4.42 ng/L in water from the largest urban lake of China (the Tangxun Lake) in winter, with wastewater discharge being the main potential source. The reliability and stability of the HLB-DGT for measuring NNIs in the groundwater and surface water were confirmed and can be used to improve understanding of the occurrence and fate of NNIs in aquatic environment.

The global well-posedness of the relativistic Boltzmann equation with hard potentials and diffuse reflection boundary condition in bounded domains

The global well-posedness of the relativistic Boltzmann equation with hard potentials and diffuse reflection boundary condition in bounded domains

Operando Tracking of Transport Properties in Na3V2(PO4)2F3 and LiFePO4 Battery Electrodes by In-Plane Measurements

The development of batteries has become a major challenge and requires new operando techniques for tracking reaction kinetics in battery electrodes during operation. Taking Na3V2(PO4)2F3 and LiFePO4 as examples of positive electrode materials, the present work deals with the design of an operando technique to measure the ionic and electronic transport properties of battery electrodes during polarization. In the case of LiFePO4, large electronic resistance changes were revealed when crossing the solid-solution domains. Such resistance changes are consistent with thermodynamic models proposing the existence of a diffuse phase boundary between Li-poor and Li-rich domains, as a result of the non-linear variation of the chemical potential of the LFP particles, which in turn leads to restricted lithium diffusion. Concerning Na3V2(PO4)2F3, the important variations of electronic resistance measured were correlated with different phase changes and superstructures formed during the insertion-disinsertion of Na+ ions, as well as the polarization and entropy heat variations. These results are fully consistent with a substantial correlation of structural changes with transport properties and reaction kinetics, and thus, performances. More generally, this technique shows great promise as a tool to aid in designing battery electrodes with improved ionic and electronic percolations.

Microfluidics for hydrodynamic investigations of sand dollar larvae

The life cycle of most marine invertebrates includes a planktonic larval stage before metamorphosis to bottom-dwelling adulthood. During the larval stage, ciliary-mediated activity enables feeding (capturing unicellular algae) and transporting materials (e.g., oxygen) required for the larva’s growth, development, and successful metamorphosis. Investigating the underlying hydrodynamics of the ciliary activities is valuable for addressing fundamental biological questions (e.g., phenotypic plasticity) and advancing engineering applications (e.g., biomimetic design). We combined microfluidics and fluorescence microscopy as a miniaturized particle image velocimetry approach to study ciliary-mediated hydrodynamics during suspension feeding in sand dollar larvae (Dendraster excentricus). First, feasibility was confirmed by examining the underlying hydrodynamics (ciliary-mediated vortex patterns) for low- and high-fed larvae. Next, ciliary hydrodynamics were tracked from 11 days post-fertilization (DPF) to 20 DPF for 21 low-fed larvae. Microfluidics enabled the examination of baseline activities (without external flow) and behaviors in the presence of environmental cues (external flow). A library of qualitative vortex patterns and quantitative hydrodynamics (velocity and vorticity profiles) was generated. Velocities were used to examine the role of ciliary activity in transporting materials. Given the laminar flow and the viscosity-dominated environments surrounding the larvae, overcoming the diffusive boundary layer is critical. Péclet number analysis for oxygen transport suggested that ciliary velocities help overcome the diffusion-dominated transport. The approach was used to examine the hydrodynamics of two additional marine larvae (P. helianthoides and S. purpuratus). Microfluidics provided a scalable and accessible approach for investigating the ciliary hydrodynamics of marine organisms.

Enhancing retention of biological fluid transport of magnetized thermal radiative pseudoplastic nanofluid with double diffusion convection, viscous dissipation and boundary slips

This study investigates how thermal radiation, viscous dissipation, double-diffusive convection, and slip boundaries collectively affect the peristaltic movement of a magneto-pseudoplastic nanofluid within a uniform channel. The inclusion of slip boundary conditions at the channel walls helps to accurately represent the flow behavior of the nanofluid near these boundaries. The magneto-pseudoplastic nanofluid exhibits peculiar rheological features to flow dynamics due to pseudoplastic characteristics of nanoparticles in its composition and exposure to magnetic force. The mathematical formulation of motion equations is done through appropriate technique combining the properties of heat radiation, magnetic flux, double diffusion convection, and rheological features. The equation is further simplified by suitable method. The current study aims to evaluate the peristaltic movement under influence of slip boundaries characteristics, sort of concentration, heat radioactivity, flux properties, and temperature profile. Moreover, it will assess the flow dynamics with ratio of mass and heat exchange under the effect of critical parameters which include Prandtl number, Grashof number, slip limitations, and Hartmann number. So, the research will widen the theoretical underpinning of complex fluid transportation of magneto-pseudoplastic nanofluids under peristaltic flux and explicate the practical outcomes in terms of slip boundary settings in such systems. The results and conclusions are imperative for restructuring and devising biomedicine engineering, microfluidic equipment and gadgets, manufacturing techniques for complex fluid with peristaltic flow under the influence of slip limitations and magnetic force.

Molecular dynamics simulations of nanoparticle sintering in additive nanomanufacturing: insights from sintering mechanisms

The sintering behavior of nanoparticles (NPs), which determines the quality of additively nanomanufactured products, differs from conventional understanding established for microparticles. As NPs have a high surface-to-volume ratio, they are subjected to a higher influence from surface tension and a lower melting point than microparticles, resulting in variations in both crystallographic defect-mediated and surface diffusion mechanisms. Meanwhile, the interplay between these controlling mechanisms in NPs has not been well understood, primarily because sintering occurs on the nanosecond timescale, making it an exceptionally transient process. In this work, sintering of both equal and unequal sized Ag and Cu NP doublets with and without misorientation (both tilt and twist) is modeled through molecular dynamics (MD) simulations. The formation and evolution of crystallographic defects, such as vacancies, dislocations, stacking faults, twin boundaries, and grain boundaries, during sintering are investigated. The influence of these defects on plastic deformation and diffusion mechanisms, such as volume diffusion and grain boundary (GB) diffusion, is discussed to elucidate the responsible sintering mechanisms. The surface diffusion mechanism is visualized by using detailed atomic trajectories generated during the sintering process. Finally, the overall effectiveness of all diffusion sintering mechanisms is quantified. This study provides first insights into the complexity and dynamics of NP sintering mechanisms which can aid in the development of accurate predictive models.

Nanostructure and dislocation interactions in refractory complex concentrated alloy: From chemical short-range order to nanoscale B2 precipitates

Refractory complex concentrated alloys (RCCAs) have emerged as a promising class of structural materials, demonstrating exceptional mechanical performance in aggressive environments. However, the complex atomic environments, significant lattice distortion, and vast compositional space of RCCAs present challenges to understanding the mechanisms that govern structure-property relationships. In this study, we explore the dislocation mechanisms in three model quaternary RCCAs, namely Mo25Nb10Ta25W40 (at. %), Mo25Nb25Ta25W25, and Mo25Nb40Ta25W10 using large-scale atomistic simulations and machine learning based Spectral Neighbor Analysis Potential. Our atomistic simulations examine how the chemical composition and local ordering influence the mobility of both edge and screw dislocations, and how lattice distortion and diffuse anti-phase boundary energy (DAPBE) affect dislocation behaviors during nanostructural evolution. Notably, with the increase in Nb concentration in the model RCCAs, both DAPBE and lattice distortion are simultaneously enhanced as the chemical short-range order (CSRO) evolves into nanoscale B2 precipitates. This evolution results in high lattice distortion due to the lattice mismatch between B2 precipitates and the random matrix. Consequently, B2 nanoprecipitates provide a stronger pinning effect, hindering edge dislocation motion while promoting cross-slip of screw dislocations, leading to a reduced screw-to-edge ratio in slip resistance and mobility discrepancy. These findings offer valuable insights into dislocation behaviors and interactions with ordered precipitates, highlighting the importance of exploring non-equiatomic compositions and advancing beyond CSRO in RCCAs. This study has implications for optimizing alloy compositions and processing methods for superior performance in aggressive environments.

Stability of solutions to the logistic equation with delay, diffusion and nonclassical boundary conditions

Stability of solutions to the logistic equation with delay, diffusion and nonclassical boundary conditions

The Particle Drifting Effect: A Combined Function of Colloidal and Drug Properties.

The particle drifting effect, where nanosized colloidal drug particles overcome the diffusional resistance of the aqueous boundary layer adjacent to the intestinal wall and increase drug absorption rates, is drawing increasing attention in pharmaceutical research. However, mechanistic understanding and accurate prediction of the particle drifting effect remain lacking. In this study, we systematically evaluated the extent of the particle drifting effect affected by drug and colloidal properties, including the size, number, and type of the moving species using biphasic diffusion experiments combined with computational fluid dynamics simulations and mass transport analyses. The results showed that the particle drifting effect is a sequential reaction of particle dissolution/dissociation in the diffusional boundary layer, followed by absorption of the free drug. Therefore, factors affecting the rate-limiting step, which can be either process or both under different circumstances, alter the particle drifting effect. Experimental results also agree with the theory that the particle dissolution rate is dependent on particle size, concentration, and drug solubility. In addition, rapid bile micelle dissociation and bile salt absorption facilitated drug absorption by the particle drifting effect. Our findings explain the highly dynamic nature of the particle drifting effect and will contribute to rational formulation development and better bioavailability prediction for formulations containing colloidal particles.