Fluid Transport Phenomena Research Articles

Thermodynamics, static properties and transport behaviour of fluids with competing interactions

Competing interaction fluids have become ideal model systems to study a large number of phenomena, for example, the formation of intermediate range order structures, condensed phases not seen in fluids driven by purely attractive or repulsive forces, the onset of particle aggregation under in- and out-of-equilibrium conditions, which results in the birth of reversible and irreversible aggregates or clusters whose topology and morphology depend additionally on the thermodynamic constrictions, and a particle dynamics that has a strong influence on the transport behaviour and rheological properties of the fluid. In this contribution, we study a system of particles interacting through a potential composed by a continuous succession of a short-ranged square-well (SW), an intermediate-ranged square-shoulder and a long-ranged SW. This potential model is chosen to systematically analyse the contribution of every component of the interaction potential on the phase behaviour, the microstructure, the morphology of the resulting aggregates and the transport phenomena of fluids described by competing interactions. Our results indicate that the inclusion of a barrier and a second well leads to new and interesting effects, which in addition result in variations of the physical properties associated to the competition among interactions.

BACKGROUND-ORIENTED SCHLIEREN FOR FLOW AND THERMAL SYSTEMS: PRINCIPLES OF IMAGE FORMATION AND APPLICATIONS

Imaging fluid flow and transport phenomena has gained considerable attention in the recent past. The imaging techniques are not only limited to visualization tools but, when coupled with suitable data reduction algorithms, can lead to the generation of the complete whole field quantitative data of flow and transported properties. In this direction, the technique of background-oriented schlieren (BOS) is one of the latest developments that has garnered significant attention among the research community. The present article reviews the plausible configurations of the BOS system, including principles of image formation and its applications in the domain of flow and thermal systems. Particular attention is paid to various constraints that one faces while configuring the imaging technique correctly from its first principles and those associated with the development of data reduction methodologies for BOS image analysis. Various modifications affected in the standard BOS, since the time it was proposed by Meier et al. (2002, 2013), for mapping the flow and transported properties as well as thickness variations of liquid surfaces are reviewed. Following an extensive review of the available literature, the potential of BOS in imaging single- as well as two-phase heat transfer phenomena is demonstrated by setting up lab-based test configurations that include natural convection over a heated vertical flat plate and horizontally placed circular cylinder, and the evaporation dynamics of impinging acetone droplet(s). The recorded BOS images are quantitatively analyzed to retrieve the field distribution of parameters of interest in each of the configurations studied.

A mathematical model for understanding nanoparticle biodistribution after intratumoral injection in cancer tumors

To exploit the benefits of a multifunctional nanomaterial as theranostics, drug carriers, and adjuvant therapeutics, tissue parameters affecting in-vivo transport, intratumoral diffusion, need to be understood properly. Literature has reported different regions of tumor such as necrotic core, viable tumor which are surrounded by healthy tissue. Transvascular exchange of the fluid and solute plays a crucial role in nanoparticle retention in the tumors. Modeling fluid and solute transport phenomenon in tissue considering in-vivo tumor architecture is essential. In this study, the influence of necrotic core presence, transvascular transport, nanoparticle size, and vascular normalization have been investigated to better understand the nanoparticle distribution in tumors. A three-dimensional numerical model has been developed to study the interstitial fluid flow and nanoparticle distribution in tumors considering the reported in-vivo scenario. The effects of nanoparticle size, intratumoral single-site, and multi-site injection methods, and vascular normalization on the distribution were investigated. In-silico investigations were carried out with respective parameters of tumor and healthy tissues using finite element based COMSOL Multiphysics 5.6® software. Interstitial fluid pressure, velocity, and nanoparticle concentration in interstitial space were predicted by solving the developed models. It was found that the interstitial fluid pressure is elevated and uniform throughout the tumor region, inhibiting the convective transport of the nanoparticles. Post-injection distribution patterns of nanoparticles revealed that the smaller nanoparticles show faster diffusion and rapid clearance from the tissues, while larger particles are retained for longer periods. The multi-site infusion method is more efficacious than the single-site method, gives better distribution patterns in the tumor. Vascular normalization does not affect the distribution of larger particles while it has shown a profound effect on the 10 nm particle distribution. Considering necrotic core and transvascular transport is inevitable in modeling to replicate the in-vivo scenario in in-silico investigations. Based on the results obtained, it is found that very fine particles of the size 10 nm will lead to lower therapeutic concentrations due to vascular clearance, despite faster diffusion rates. Particle sizes larger than 30 nm will not diffuse into the tumor due to lower diffusion coefficients and retained at the injected site. This study proposes 15 nm–30 nm as the suitable size for hyperthermia considerations.

Modeling of micro-channel critical flow with inlet sub-cooling: Metastable liquid and nucleation

Critical flows are relevant multiphase phenomena in many applications or scenarios for chemical processes. The paper aims to propose a reliable two-fluid model to accurately simulate the micro-channel critical flow. The fluid density of the metastable liquid is determined using an isentropic transformation assumption. The onset of flashing is evaluated by solving conservation equations coupled with a nucleation model. The available constitutive relations (interfacial force and interfacial heat transfer) are compared and evaluated depending on the analysis of the transfer process in two-phase flow regions to seek reasonable constitutive relations. The paper compares the proposed model and separated flow models using available constitutive relations, especially for the pressure profile. The proposed model shows superior performance in critical flow simulations. To further advance the understanding of the critical flow, the fluid flow and transport phenomena in a micro-channel are studied intensively, especially for the cooling of micro-channels.

Predicting Fluid Flow Regime, Permeability, and Diffusivity in Mudrocks from Multiscale Pore Characterisation

In geoenergy applications, mudrocks prevent fluids to leak from temporary (H2, CH4) or permanent (CO2, radioactive waste) storage/disposal sites and serve as a source and reservoir for unconventional oil and gas. Understanding transport properties integrated with dominant fluid flow mechanisms in mudrocks is essential to better predict the performance of mudrocks within these applications. In this study, small-angle neutron scattering (SANS) experiments were conducted on 71 samples from 13 different sets of mudrocks across the globe to capture the pore structure of nearly the full pore size spectrum (2 nm–5 μm). We develop fractal models to predict transport properties (permeability and diffusivity) based on the SANS-derived pore size distributions. The results indicate that transport phenomena in mudrocks are intrinsically pore size-dependent. Depending on hydrostatic pore pressures, transition flow develops in micropores, slip flow in meso- and macropores, and continuum flow in larger macropores. Fluid flow regimes progress towards larger pore sizes during reservoir depletion or smaller pore sizes during fluid storage, so when pressure is decreased or increased, respectively. Capturing the heterogeneity of mudrocks by considering fractal dimension and tortuosity fractal dimension for defined pore size ranges, fractal models integrate apparent permeability with slip flow, Darcy permeability with continuum flow, and gas diffusivity with diffusion flow in the matrix. This new model of pore size-dependent transport and integrated transport properties using fractal models yields a systematic approach that can also inform multiscale multi-physics models to better understand fluid flow and transport phenomena in mudrocks on the reservoir and basin scale.

Overlapping grid spectral collocation approach for electrical MHD bioconvection Darcy–Forchheimer flow of a Carreau–Yasuda nanoliquid over a periodically accelerating surface

AbstractThe focus of this study is on computational grid‐manipulation to enhance the accuracy, convergence, and computational efficiency of the multidomain bivariate spectral local linearization method (MD‐BSLLM). The improved method is used in the scrutiny of Darcy–Forchheimer bioconvection flow of Carreau–Yasuda nanofluid induced by an oscillatory moving surface with cross‐diffusion, activation energy with binary chemical reactive species, combined electrical and magnetohydrodynamic field effects. The proposed method is utilized in solving the nondimensional form of the flow equations. Sensitivity and error analyses are provided to aid an understanding of the efficiency, stability, convergence rate, and accuracy of the iterative scheme. The impact of different parameter values on fluid properties and transport phenomena is discussed. Numerical simulation has indicated that the overlapping grid MD‐BSLLM is computational efficacious, and produces stable and sufficiently accurate results using a few collocation nodes in each respective subinterval and the entire computational domain. Other findings include the fact that fluid properties are enhanced with injection while flow characteristics are improved with suction. Using the Darcy–Forchheimer model in the flow analysis improves the temperature of the nanofluid. The imposition of electric field augments nanofluid velocity, the amplitude of skin friction coefficient, rates of mass, and motile microorganisms transfer while reducing the rate of heat transfer. The considered flow analysis can contribute towards engineering solicitations in paper production, polymer solution, metal extrusion, and glass blowing.

Unsteady conjugate model of fluid mechanics and mass transfer for butanol pervaporation process by non-porous membrane

A diffusion-convective mass transfer mathematical conjugated model of butanol recovery from a re-circulating aqueous solution by pervaporation using a polydimethylsiloxane (PDMS) membrane was developed based on computational fluid dynamics. Discretized continuity, linear momentum, and convective-diffusion mass transfer equations were solved by an in-house code based on the finite volume method for a laminar flow with a flat attached non-porous membrane. In addition, a novel numerical procedure to determine the butanol diffusivity in the PDMS membrane was developed based on the solution of the conjugate unsteady convection-diffusion model that included five coupled partial differential equations. The evolution of the distribution of the velocity profile in the fluid flow and the transient variation of butanol concentration in the feed solution and inside the PDMS membrane were determined. Variations in time and space of the dimensionless mass flux along the length of the pervaporation module were calculated from the conjugate convection-diffusion mass transfer model. The numerical predictions of the butanol mass flux in the feed solution exhibited good agreement with the experimental results with an error smaller than 3%. Understanding the mechanisms of mass and fluid transport phenomena by computational modeling can be helpful for improving the design of pervaporation processes.

Sparse nonlinear models of chaotic electroconvection.

Convection is a fundamental fluid transport phenomenon, where the large-scale motion of a fluid is driven, for example, by a thermal gradient or an electric potential. Modelling convection has given rise to the development of chaos theory and the reduced-order modelling of multiphysics systems; however, these models have been limited to relatively simple thermal convection phenomena. In this work, we develop a reduced-order model for chaotic electroconvection at high electric Rayleigh number. The chaos in this system is related to the standard Lorenz model obtained from Rayleigh–Benard convection, although our system is driven by a more complex three-way coupling between the fluid, the charge density, and the electric field. Coherent structures are extracted from temporally and spatially resolved charge density fields via proper orthogonal decomposition (POD). A nonlinear model is then developed for the chaotic time evolution of these coherent structures using the sparse identification of nonlinear dynamics (SINDy) algorithm, constrained to preserve the symmetries observed in the original system. The resulting model exhibits the dominant chaotic dynamics of the original high-dimensional system, capturing the essential nonlinear interactions with a simple reduced-order model.

Special Issue “Fluid Dynamics, Multi-Phase Flow, and Thermal Recovery Methods”

Intricate fluid flow and transport phenomena in porous media are ubiquitous in natural processes and engineering systems [...]

Computational fluid dynamics modeling of a new high-pressure chemical vapor deposition reactor design

The design of a new super-atmospheric pressure metal organic chemical vapor deposition (MOCVD) reactor with spatially separated source zones and rotating susceptor is proposed and analyzed using computational fluid dynamics (CFD) techniques to determine fluid transport phenomena and suitability for thin-film synthesis of group III nitrides. This High-Pressure Spatial Chemical Vapor Deposition (HPS-CVD) reactor is designed to permit high-temperature growth of high-indium content group III nitrides. This is made possible by increasing the partial pressure of nitrogen by up to two orders of magnitude in the system thereby increasing decomposition temperatures of the group III nitride thin film. The effects of rector design, chamber height, system pressure, inlet flow rate, and rotational speed are investigated and discussed. Flow instabilities arising from the heated and rotating susceptor traversing separate source zones are minimized. Growth rates of group III nitride materials synthesized in an HPS-CVD reactor are estimated to be enhanced by approximately a factor of 10 compared to an existing super-atmospheric MOCVD reactor due to improved reactor design thereby providing comparable growth rates to current atmospheric MOCVD systems.

Powerful Acoustogeometric Streaming from Dynamic Geometric Nonlinearity.

Past forms of acoustic streaming, named after their progenitors Eckart (1948), Schlichting (1932), and Rayleigh (1884), serve to describe fluid and particle transport phenomena from the macro to micro-scale. Governed by the fluid viscosity, traditional acoustic streaming arises from second-order nonlinear coupling between the fluid's density and particle velocity, with the first-order acoustic wave time averaging to zero. We describe a form of acoustogeometric streaming that has a nonzero first-order contribution. Experimentally discovered in nanochannels of a height commensurate with the viscous penetration depth of the fluid in the channel, it arises from nonlinear interactions between the surrounding channel deformation and the leading order acoustic pressure field, generating flow pressures three orders of magnitude greater than any known acoustically mediated mechanism. It enables the propulsion of fluids against significant Laplace pressure, sufficient to produce 6 mm/s flow in a 130-150nm tall nanoslit. We find quantitative agreement between theory and experiment across a variety of fluids and conditions, and identify the maximum flow rate with a channel height 1.59 times the viscous penetration depth.

Numerical investigation on fluid transport phenomena in electron beam welding of aluminum alloy: Effect of the focus position and incident beam angle on the molten pool behavior

In this study, a three-dimensional model involving heat transfer and melt flow is established to study the influence of the focus position and incident beam angle on the molten pool behavior in electron beam welding of aluminum alloy. The effects of gravity, surface tension and recoil pressure are considered during the simulation process. The formation process of a dynamic keyhole is also investigated. Numerical results indicate that a nail-shaped weld seam with the large aspect ratio is easily formed at the defocus of 0 mm and a wedge-shaped weld seam with the small aspect ratio is easier to appear at the defocus of −8 or +8 mm. The keyhole and molten pool are inclined along the incident direction of the electron beam. Besides, a wider and shallower keyhole could be found with an incident angle of 30° or 150°. The processing parameters at the defocus of 0 mm and with beam inclination angle greater than 90° are helpful to improve the weld quantity. Moreover, the corresponding welding experiments are performed to verify the precision of the numerical models applied in this work. The simulated weld results agree well with the experimental data.

Microheart: A microfluidic pump for functional vascular culture in microphysiological systems

Advances in microphysiological systems have prompted the need for long-term cell culture under physiological flow conditions. Conventional laboratory pumps typically lack the ability to deliver cell culture media at the low flow rates required to meet the physiological ranges of fluid flow, and are often pulsatile or require flow reversal. Here, a microfluidic-based pump is presented, which allows for the controlled delivery of media for vascular microphysiological applications. The performance of the pump was characterized in a range of microfluidic systems, including straight channels of varying dimensions and self-assembled microvascular networks. A theoretical framework was developed based on lumped element analysis to predict the performance of the pump for different fluidic configurations and a finite element model of the included check-valves. The use of the pump for microvascular physiological studies demonstrated the utility of this system to recapitulate vascular fluid transport phenomena in microphysiological systems, which may find applications in disease models and drug screening.

Swelling-Induced Interface Crease Instabilities at Hydrogel Bilayers

Two dissimilar hydrogel layers bonded together become unstable when the compressive stresses due to diffusion-driven swelling of the layers reach a critical point and creases form at the interface. Although creasing instabilities observed on surfaces of soft solids subjected to large compressions are well studied, the transient nature and critical conditions for the emergence of interface creases as a result of swelling behavior of hydrogels remain elusive. Here, we investigate the formation and transient growth of interface creases in bilayer hydrogels through experimental and computational approaches. Equipped with a mixed isogeometric analysis that accounts for large swelling deformations along with dissipative fluid transport phenomena, we show that both the equilibrium and the transient characteristics of interface creases can be tuned by controlling the material properties, in contrast to the reported material-independent behavior of creases in elastomers. The effects of material parameters on the onset and growth of interface creases are quantified in terms of the critical swelling ratio and critical chemical potential, and these values are compared to the critical conditions for the emergence of wrinkling instabilities. In agreement with our experimental observations of swelling bilayer hydrogels, our computational results demonstrate that the formation of creases is energetically more favorable than wrinkle formation at the interface.

Constriction length dependent instabilities in the microfluidic entry flow of polymer solutions.

Transport phenomena of fluids and particles through contraction and/or expansion geometries have relevance in many applications. Polymer solutions are often the transporter in these processes, giving rise to flow complexities. The separation distance between a contraction and a following expansion in microfluidic entry flow can affect the interplay between the shear and extension force dominated flow regimes, but the process is still little understood. We investigate the rheological responses of such constriction length dependent instabilities with three different polymer solutions and water in planar contraction-expansion microchannels differing only in the constriction length. The viscoelastic polyethylene oxide (PEO) solution is found to exhibit strong constriction length-dependent instabilities in both the contraction and expansion flows. Such a dependence is, however, completely absent from the flow of shear-thinning xanthan gum (XG) solution and Newtonian water. Interestingly, it is only present in the expansion flow of the both shear thinning and viscoelastic polyacrylamide (PAA) solution.

Multiple Slip and Inspiration Effects on Hydromagnetic Casson Fluid in a Channel with Stretchable Walls

Increasingly innovatory techniques are being developed for the manufacturer of coated sheets. Magnetite non-Newtonian fluids have been shown to exhibit stretchable wall slip, which arises due to non-adherence of the non-Newtonian fluid to the boundary. Motivated by the physical nature of the magnetic non-Newtonian fluid in manufacturing transport phenomena, we develop a model to analyze the collective influence of velocity and thermal slips, radiative heat flux effects on fluid and heat transport phenomena in magnetic non-Newtonian fluid flow in a channel with stretchable walls. Governing equations are non-dimensionalized and solved numerically. Grid independence test has been performed and then compared with existing literature in limiting cases. Results are discussed with the aid of graphs for the sway of several physical parameters, Casson parameter, Magnetic parameter, Thermal radiation parameter on fluid velocity, as well as temperature profiles for different cases: No-slip, only first-order slip, and first and second-order slips.

In Pursuit of Designing Multicellular Engineered Living Systems: A Fluid Mechanical Perspective

From intracellular protein signaling to embryonic symmetry-breaking, fluid transport ubiquitously drives biological events in living systems. We provide an overview of the fundamental fluid mechanics and transport phenomena across a range of length scales in cellular systems, with emphasis on how cellular functions are influenced by fluid transport. We also highlight how understanding the physical basis of these fluid dynamic phenomena can be implemented to engineer increasingly complex multicellular systems that recapitulate tissue-level functions. Examples discussed include the manipulation of intracellular fluid volume to achieve cell differentiation/dedifferentiation and the use of microfluidic systems to control the spatial and temporal distribution of morphogens and fluid forces to generate vascularized organoids.

Membrane catalyst layer assembly production method and membrane catalyst layer assembly production device

A detailed computational fluid dynamics (CFD) model has been developed in this study for the water gas shift of untreated biogas reformate in both fixed bed and membrane reactors to gain insights into the interaction of 3Ni5Cu/Ce0.5Zr0.33Ca0.17 catalyst with fluid transport phenomena taking place in the reactor. The developed CFD model closely agreed with data from both literature and experiments. An average absolute deviation of 8.59% and 6.32% was obtained when the CFD model was validated with a fixed bed reactor and membrane reactor experiments respectively. The membrane reactor enabled equilibrium conversion at 2.95 gcat.h/mol CO weight-time with equilibrium conversion attained at lower weight-time and steam to carbon ratio of 3.4. Also, it was found that the counter-flow configuration resulted in better enhanced CO conversion, and the wall heat transfer coefficient above 8.6 W/m2/K had negligible on conversion, amounting to only a 1% increase in conversion for both reactors.

CFD investigation of biogas reformate using membrane-assisted water gas shift reaction: Parametric analyses

A detailed computational fluid dynamics (CFD) model has been developed in this study for the water gas shift of untreated biogas reformate in both fixed bed and membrane reactors to gain insights into the interaction of 3Ni5Cu/Ce0.5Zr0.33Ca0.17 catalyst with fluid transport phenomena taking place in the reactor. The developed CFD model closely agreed with data from both literature and experiments. An average absolute deviation of 8.59% and 6.32% was obtained when the CFD model was validated with a fixed bed reactor and membrane reactor experiments respectively. The membrane reactor enabled equilibrium conversion at 2.95gcat.h/mol CO weight-time with equilibrium conversion attained at lower weight-time and steam to carbon ratio of 3.4. Also, it was found that the counter-flow configuration resulted in better enhanced CO conversion, and the wall heat transfer coefficient above 8.6W/m2/K had negligible on conversion, amounting to only a 1% increase in conversion for both reactors.

Entropy analysis for the peristaltic flow of third grade fluid with variable thermal conductivity

Recently there is a need to enhance the cooling capabilities required in many industrial applications. Therefore it is important to know the factors for system’s disorderliness. This work is based on the study of entropy analysis in fluid transport phenomenon by peristalsis. Mixed convective flow in compliant wall channel is considered. Here third grade fluid is considered. Effect of gravity is also encountered. Magnetohydrodynamic and Joule heating are part of flow modeling. Energy equation is addressed subject to viscous dissipation and variable thermal conductivity. Resulting system is solved with the help of NDSolve command in Mathematica. Proper attention is given to the study of velocity, temperature and entropy analysis. This analysis is carried out via graphical results for different embedded parameters. Graphs for heat transfer coefficient are also plotted and analyzed.