Fluid Particles Research Articles

Point-of-Care Multiplex Detection of Respiratory Viruses.

The COVID-19 pandemic, in addition to the co-occurrence of influenza virus and respiratory syncytial virus (RSV), has emphasized the requirement for efficient and reliable multiplex diagnostic methods for respiratory infections. While existing multiplex detection techniques are based on reverse transcription quantitative polymerase chain reaction (RT-qPCR) and extraction and purification kits, the need for complex instrumentation and elevated cost limit their scalability and availability. In this study, we have developed a point-of-care (POC) device based on reverse transcription loop-mediated isothermal amplification (RT-LAMP) that can simultaneously detect four respiratory viruses (SARS-CoV-2, Influenza A, Influenza B, and RSV) and perform two controls in less than 30 min, while avoiding the use of the RNA extraction kit. The system includes a disposable microfluidic cartridge with mechanical components that automate sample processing, with a low-cost and portable optical reader and a smartphone app to record and analyze fluorescent images. The application as a real point-of-care platform was validated using swabs spiked with virus particles in nasal fluid. Our portable diagnostic system accurately detects viral RNA specific to respiratory pathogens, enabling deconvolution of coinfection information. The detection limits for each virus were determined using virus particles spiked in chemical lysis buffer. Our POC device has the potential to be adapted for the detection of new pathogens and a wide range of viruses by modifying the primer sequences. This work highlights an alternative approach for multiple respiratory virus diagnostics that is well-suited for healthcare systems in resource-limited settings or at home.

Lattice Boltzmann simulation on particle suspensions containing porous particles in a narrow channel

The suspension of porous particles in fluids occurs widely in various natural and industrial processes. However, the sedimentation behavior of porous particles is not extensively understood as the solid impermeable counterparts. In this work, the drafting–kissing–tumbling (DKT) phenomenon in a narrow channel containing porous particles is investigated by the multi-relaxation-time (MRT) lattice Boltzmann method (LBM). The initial particle spacing Lp* (1.5∼6) and Darcy number Da (8×10−6∼6×10−2) are examined on the sedimentation process of two particles under three initial arrangements, i.e., the trailing particle is porous (case 1), the leading particle is porous (case 2), and both the particles are porous (case 3). The results show that the presence of porous particles can enhance the interactions between two particles, and increasing the penetrability reduces the particle drag force to accelerate sedimentation. The drafting time is insensitive to Da at small Lp*, and it decreases with Da at large Lp* in cases 1 and 3 while it changes to increase with Da in case 2. A phase diagram with respect to Da and Lp* is further extracted to identify three sedimentation modes of particle pairs. It is found that the transition between the one-off DKT and repeated DKT modes is not affected by Lp* in cases 2 and 3, while the critical condition for the non-DKT and one-off DKT modes depends strongly on Da and Lp* in case 2.

Hydrodynamic Impact of Dusty Fluid-Suspended Solid Particles in a Single-Walled Corrugated Channel for Water-Curing Infrastructure Networks

Infrastructure engineering is impacted by solid particles in fluids, and engineering components are influenced by fluid flow methods. This work explores the effects of dusty fluids with suspended solid particles in a single-walled corrugated channel using electromagnetic hydrodynamics. Potential, continuity, and momentum equations were employed to study the periodic sinusoidal waves in the corrugations of two wavy walls using the perturbation method. We assessed the impact of corrugation on velocity for EMHD fluid flow using mathematical computation, concentrating on the analytical velocity solutions. The analysis of velocity profiles through graphs reveals that corrugation affects fluid and particle velocity behavior, with small amplitude reducing wave effects and dusty particles boosting velocity. The proposed model uses mathematical induction to solve engineering problems using corrugated wall conditions for fluid control during curing stages. It may be valuable for sanitation networks, rainwater drainage networks, and irrigation systems. In the end, a thorough examination of the obtained results and information from past papers demonstrated a high level of agreement. Additionally, its use in the curing of water will offer alternative methods of managing the flowing fluid than mechanical pressure.

A hydrodynamic approach to reproduce multiple spinning vortices in horizontally rotating three-dimensional liquid helium-4

This paper reports a three-dimensional (3D) simulation of a rotating liquid helium-4, using a two-fluid model with spin-angular momentum conservation. Our model was derived from the particle approximation of an inviscid fluid with residual viscosity. Despite the fully classical mechanical picture, the resulting system equations were consistent with those of the conventional two-fluid model. We consider bulk liquid helium-4 to be an inviscid fluid, assuming that the viscous fluid component remains at finite temperatures. As the temperature decreased, the amount of the viscous fluid component decreased, ultimately becoming a fully inviscid fluid at absolute zero. Weak compressibility is assumed to express the volume change because some helium atoms do not render fluid owing to Bose–Einstein condensations or change states because of local thermal excitation. One can solve the governing equations for an incompressible fluid using explicit smoothed-particle hydrodynamics, simultaneously reproducing density fluctuations and describing the fluid in a many-particle system. We assume the following fluid–particle duality: a hydrodynamic interfacial tension between the inviscid and viscous components or a local interaction force between two types of fluid particles. The former can be induced in the horizontal direction when non-negligible non-uniformity of the particles occurs during forced two-dimensional rotation, and the latter is non-negligible when the former is negligible. We performed a large-scale simulation of 3D liquid helium forced to rotate horizontally using 32 graphics processing units. Compared with the low-resolution calculation using 2.4 × 106 particles, the high-resolution calculation using 19.6 × 106 particles showed spinning vortices close to those of the theoretical solution. We obtained a promising venue to establish a practical simulation method for bulk liquid helium-4.

Numerical study of the interaction between cylindrical particles and shear-thinning fluids in a linear shear flow

In this paper, the interaction between cylindrical particles and shear-thinning non-Newtonian fluids in a linear shear flow is investigated using particle-resolved direct numerical simulation. The Carreau model is used to represent the rheological properties of shear-thinning fluids, and the numerical method is validated against previously published data. Then, the effects of Reynolds number (Re), aspect ratio (Ar), power-law index (n), Carreau number (Cu), and incident angle (α) on drag coefficient (CD), lift coefficient (CL), and torque coefficient (CT) of cylindrical particles are investigated. The numerical results show that the flow field structure and pressure distribution around the cylindrical particle in a shear flow are different from those in a uniform flow, and the particles in a shear flow generate extra CL and CT. Furthermore, comparing with Newtonian fluids, the shear-thinning properties of the non-Newtonian fluid change the viscosity distribution and significantly decrease the CD, CL, and CT of the particles. The variation laws and influencing mechanisms of CD, CL, and CT under different working conditions are discussed by dividing the total coefficients into pressure and viscous shear contributions. Predictive correlations of CD, CL, and CT are established by considering the effects of Re, Ar, n, Cu, and α. The findings indicate that both the shear flow mode and shear-thinning properties must be considered when evaluating relevant particle–fluid interactions, which provides important guidance for predicting and controlling the orientation and distribution of cylindrical particles in shear-thinning fluids. Meanwhile, the predictive correlations can be used for large-scale simulations of multiphase coupling.

Revisiting the governing equations of a magnetic suspension of polar particles: From microhydrodynamics analysis to rheological response

In this review, we describe a formulation for the stress tensor of a monodisperse magnetic suspension of polarized neutrally buoyant spheroidal particles suspended in a non-magnetic liquid. A magnetic suspension affords a rare example of a material for which the stress tensor is non-symmetric. The present formulation is based on a microhydrodynamics description of a spherical particle suspended in a Newtonian fluid subjected to magnetic forces and torques. The magnetic suspension is considered statistically homogeneous and treated as being a homogeneous equivalent fluid. Under this condition, a volume average over all particles in the carrier fluid is used in order to obtain the magnetization equation evolution and the constitutive equation for the stress tensor of the magnetic suspension, in particular the magnetic stress contribution. The average effects on the homogeneous continuum fluid due to particle pressure, particle dipole, and the applied magnetic field on each particle are computed by our constitutive equation. In this approach, the particles are not considered force or torque free since their permanent magnetization allows them to experience the effects of an applied magnetic field. The calculated stress tension can be used for modeling common flows of symmetric or non-symmetric magnetic fluids flowing in arbitrary geometries and in rheological applications for determination of important properties such as the rotational viscosity of non-symmetric magnetic fluids. The final expression of the constitutive equation for the stress tensor based on a particle scale approach presents some difference as compared with current constitutive models proposed in the current literature. Our constitutive equation considers the effect of a magnetic particle pressure, the average particle stresslet contribution in terms of an effective viscosity, the average particle rotlet in terms of a rotational viscosity, and a configurational tensor associated with dipole–dipole interactions. In addition, we discuss the situation in which the dipole moment of the particle is not frozen on it which leads to the necessity of an internal balance of angular momentum in a fluid element to close the governing equations of the model. An extension of the model for emulsions of polar deformable droplets is also proposed.

Madelung mechanics and superoscillations

In single-particle Madelung mechanics, the single-particle quantum state Ψ(x→,t)=R(x→,t)eiS(x→,t)/ℏ is interpreted as comprising an entire conserved fluid of classical point particles, with local density R(x→,t)2 and local momentum ∇→S(x→,t) (where R and S are real). The Schrödinger equation gives rise to the continuity equation for the fluid, and the Hamilton–Jacobi equation for particles of the fluid, which includes an additional density-dependent quantum potential energy term Q(x→,t)=−ℏ22m∇→R(x→,t)R(x→,t) , which is all that makes the fluid behavior nonclassical. In particular, the quantum potential can become negative and create a nonclassical boost in the kinetic energy. This boost is related to superoscillations in the wavefunction, where the local frequency of Ψ exceeds its global band limit. Berry showed that for states of definite energy E, the regions of superoscillation are exactly the regions where Q(x→,t)<0 . For energy superposition states with band-limit E+ , the situation is slightly more complicated, and the bound is no longer Q(x→,t)<0 . However, the fluid model provides a definite local energy for each fluid particle which allows us to define a local band limit for superoscillation, and with this definition, all regions of superoscillation are again regions where Q(x→,t)<0 for general superpositions. An alternative interpretation of these quantities involving a reduced quantum potential is reviewed and advanced, and a parallel discussion of superoscillation in this picture is given. Detailed examples are given which illustrate the role of the quantum potential and superoscillations in a range of scenarios.

Innovative composite fluidized hydrogel GAC particles for effective membrane fouling mitigation and membrane integrity protection

Membrane filtration is recognized as an environmentally friendly and cost-efficient technology for water treatment, but membrane fouling is still a significant challenge that increases maintenance costs and reduces membrane lifespan. Particle scouring can effectively mitigate fouling with lower energy consumption. This study investigates the use of fluidized granular activated carbon (GAC) particles encapsulated with hydrogel layers to enhance fouling mitigation in microfiltration systems treating surface water. The proposed hydrogel-modified GAC particles aim to balance scouring efficiency with membrane integrity. The results demonstrate that optimizing hydrogel preparation conditions significantly enhanced the mechanical strength and surface hydrophilicity of GAC particles. The incorporation of hydrogel layers notably improved membrane fouling mitigation, reducing transmembrane pressure (TMP) by 19.3 %, 27.1 %, and 34.3 % for layer thicknesses of 0.5 mm, 1.0 mm, and 1.5 mm, respectively. The hydrodynamic behavior of fluidized GAC particles was significantly improved, enhancing the effectiveness of fouling mitigation in water treatment processes. Additionally, the hydrogel layer effectively protected membrane integrity and inhibited carbon release, ensuring minimal damage and stable permeability. This study underscores the pivotal role of hydrogel layers in improving the performance and longevity of membrane filtration systems, when fluidized GAC particles are used for membrane fouling control.

Study on the spray characteristics of transverse jets with elliptical nozzles in supersonic crossflows using the volume of fluid–discrete phase model

The atomization characteristics of liquid jets injected transversely into a supersonic crossflow significantly affect the performance of scramjet engines. Existing research on this topic has mainly focused on circular nozzles, while the influence of nozzle geometry, particularly elliptical nozzles, has received relatively limited attention. Therefore, this study employs a numerical simulation method coupling the volume of fluid and discrete particle model to investigate the breakup and atomization characteristics of transverse liquid jets from elliptical nozzles with different aspect ratios under supersonic crossflow conditions, as well as the total pressure loss. The simulation model is validated against experimental data obtained from a pulse wind tunnel, including measurements of the liquid jet penetration depth and the Sauter mean diameter (SMD). The results indicate that for elliptical nozzles with an aspect ratio (AR) greater than 1, columnar breakup occurs earlier, and the columnar breakup length is shorter compared to circular nozzles. As the AR increases, the jet penetration depth decreases, while the spray expansion angle increases. Furthermore, the SMD of the atomized spray field from the circular nozzle is larger than that from the elliptical nozzles, and the SMD of the spray field is smallest for an elliptical nozzle with AR of 4. Finally, the elliptical nozzles exhibit a higher total pressure recovery coefficient, indicating reduced total pressure loss in the combustion chamber. This reduction in pressure loss is expected to improve the thrust performance of the scramjet engine.

Prediction of steady hydrodynamic performance of pump jet propulsion based on free wake vortex model

Due to mutual interference between various components, the transitional motion of fluid particles in the flow field of pump jet propulsion becomes more complex and variable. Additionally, the vortex structure at the wake can undergo severe contraction and deformation. To further improve the accuracy of predicting the hydrodynamic performance of pump jet propulsion, this paper proposes a time-varying, space-varying, and induced velocity-varying free wake numerical calculation model based on potential flow theory. A set of hydrodynamic performance prediction methods that consider the interference of the free wake model is also established. Furthermore, a velocity smoothing model based on time reversal is constructed based on the distribution pattern of numerical singularity points during the induced velocity calculation process, which enhances the robustness of the calculation program. By comparing and analyzing the numerical calculation results with experimental results, including pressure, circulation distribution, and hydrodynamic performance, the accuracy of the free wake model proposed in this paper is verified. The results also demonstrate that the free wake model proposed in this paper can effectively improve the prediction accuracy of the hydrodynamic performance of the pump jet propulsion.

Direct numerical simulation of open-channel flow over a heterogeneous particle bed at low relative submergence

This study investigates turbulent open-channel flows over beds of irregularly arranged particles, using direct numerical simulations at a friction Reynolds number of Reτ=300. Two distinct cases are examined: a polydisperse bed (P800) composed of multiple layers of randomly distributed spheres of varying sizes, and a monodisperse bed (M1015) formed by a random distribution of uniform sized spheres, with a bottommost single layer of varied-sized particles to introduce realistic randomness. Our investigation unveils a rich network of low- and high-speed streaks within the flow field, exhibiting distinctive behaviors in different bed configurations. The P800 case presents a poorly organized flow pattern induced by the varied particle sizes and arrangements, while the M1015 case shows a more regular flow pattern, marked by larger streaks. We also observe that total wall shear stress is substantially influenced by surface roughness-induced drag, extending beyond the effects documented in existing studies of open-channel flows. The present study reveals intricate secondary flow patterns over irregular particle beds. Large-scale circulations are discerned around particle crests in the P800 case and localized circulations with increased turbulence in the M1015 case. Furthermore, analysis of Reynolds stress tensor components indicates that roughness disrupts coherent turbulent eddies, consequently mitigating peak stress. We quantify correlations between drag force and local fluid velocity fluctuations. Notably, a larger deviation in drag is observed in the P800 case compared to M1015, accentuating the influence of particle size and distribution on fluid–particle interactions.

Computational study of momentum interactions between fluid and a static particle under the impact of anisotropic Stefan flow

The microscale gas–particle interaction is the determining process for the macroscopic flow behaviors of gas–particle systems. Anisotropic Stefan flow is often manifested at the surface of the biomass particle when thermally decomposed. However, the influence of the anisotropic Stefan flow on the gas–particle interactions is not well understood. To this end, particle-resolved direct numerical simulations were carried out in this research to explore the momentum interactions between the gas flow and a static particle emitting mass flux at its surface. A signed distance function based immersed boundary method is first extended to account for the Stefan flow at the gas–particle interface and successfully validated by comparing with literature results in the case of no Stefan flow or uniform Stefan flow. It is found that the presence of the outward uniform Stefan flow leads to an expanded wake formation and the intensity of the vortex (Re ≥ 40) is enhanced as result of the Stefan flow. Subject to the impact of anisotropic Stefan flow parallel to the main flow, the low-speed region in the front and rear of the particle is reduced when the Stefan flow goes inwards, resulting in the increase in the drag coefficient. As the Stefan flow is outward, the low-speed region in the front of the particle is pushed forward by the emitting gas and the velocity magnitude in the wake region is increased, which behaves like an enlargement of the gas cushion and leads to a significant reduction of the drag coefficient comparing with a uniform Stefan flow. In contrast, the impact of anisotropic Stefan flow with the direction perpendicular to the main flow on the fluid–particle drag interaction is less significant due to the fact that the flow structure in the front and rear regions is not significantly disturbed.

Significance of Darcy–forchheimer Casson fluid flow past a non-permeable curved stretching sheet with the impacts of heat and mass transfer

Casson fluid flow based on a curved surface has been mathematically modeled using Brownian motion and the Darcy-Forchheimer equation of porosity. Similarity variables are applied to convert flow-anchored partial differential equations into basic ordinary differential equations. The MATLAB solver “bvp4c” is utilized to derive numerical responses for the problem under consideration. During the numerical approach, all parameters have been set to their values based on reviewed literatures and numerical solutions for all flow fields have been obtained against the concerned parameters. Additionally, a variety of graphs are created utilizing numerical extractions to discuss the results. The curvature parameter (K=1.5,2.5,3.5,4.5) results in an improvement in velocity distribution (f'η=1=0.32564,0.360142,0.378247,0.385401). The reason is that for higher values of the curvature parameter, the radius of a curved sheet decreases. Hence, a smaller region of sheet will be in contact, which produces a small amount of resistance towards fluid particles, so that the velocity profiles show an enhancement. Increasing inputs of Forchheimer number imply stronger inertial effects and it introduce an additional resistance to flow that's why fluid velocity decreased. Additionally, for a curved stretched sheet, a higher drag force is required compared to a flat plate because curved sheet has a larger surface area while flat plate has a minimal surface area in contact with the fluid.

Effect of turbulence intensity on bubble-particle detachment mechanism in a confined vortex

Bubble-particle detachment induced by turbulence is the primary factor for the low recovery of coarse particles, which has attracted much attention in recent years. The prevailing centrifugal detachment theory has achieved broad consensus. However, due to the complexity of bubble-particle aggregate motion in the turbulent field, the influence of turbulence intensity on bubble-particle detachment mechanism remains unclear. In this study, a controlled rotating vortex was generated using a custom-made fluid channel to systematically investigate the effect of turbulence intensity on bubble-particle centrifugal detachment. Firstly, detachment behaviours of bubble-particle aggregates were captured using high-speed cameras, followed by flow field visualization of bubble-particle detachment processes using Computational Fluid Dynamics (CFD). Experimental results reveal three typical detachment modes of bubble-particle aggregates in the confined vortex: fluid shear, bubble oscillation, and particle centrifugal motion, with particle centrifugal detachment becoming dominant with increasing turbulence intensity. This shift is attributed to changes in turbulence intensity directly affecting the trajectories of bubble/aggregates and indirectly influencing the detachment mode of bubble-particle. Compared to low turbulence intensity, bubble-particle aggregates exhibit smaller rotational radii under high turbulence intensity, reducing the probability of fluid shear and bubble oscillation detachment by mitigating the influence of high-speed shear zones at the top of the cavity. Conversely, particles located at the edge of aggregates are more susceptible to acceleration by sidewall flow fields, favouring detachment through particle centrifugal motion. Moreover, unlike traditional centrifugal detachment theories, particles do not merely undergo independent circumferential motion on the bubble surface but participate as a whole with bubbles in centrifugal motion governed by vortices. These findings are expected to provide fundamental insights into the bubble-particle detachment mechanism in turbulent fields.

Kinematics of nonlinear waves over variable bathymetry. Part I: Numerical modelling, verification and validation

Fluid particle kinematics due to wave motion (i.e. orbital velocities and accelerations) at and beneath the free surface is involved in many coastal and ocean engineering applications, e.g. estimation of wave-induced forces on structures, sediment transport, etc. This work presents the formulations of these kinematics fields within a fully nonlinear potential flow (FNPF) approach. In this model, the velocity potential is approximated with a high-order polynomial expansion over the water column using an orthogonal basis of Chebyshev polynomials of the first kind. Using the same basis, original analytical expressions of the components of velocity and acceleration are derived in this work. The estimation of particle accelerations in the course of the simulation involves the time derivatives of the decomposition coefficients, which are computed with a high-order backward finite-difference scheme in time. The capability of the numerical model in computing the particle kinematics is first validated for regular nonlinear waves propagating over a flat bottom. The model is shown to be able to predict both the velocity and acceleration of highly nonlinear and nearly breaking waves with negligible error compared to the corresponding stream function wave solution. Then, for regular waves propagating over an uneven bottom (bar-type bottom profile), the simulated results are confronted with existing experimental data, and very good agreement is achieved up to the sixth-order harmonics for free surface elevation, velocity and acceleration.

Recovering the activity parameters of an active fluid confined in a sphere.

The properties of an active fluid, for example, a bacterial bath or a collection of microtubules and molecular motors, can be accessed through the dynamics of passive particle probes. Here, in the perspective of analyzing experimental situations of confinement in droplets, we consider the kinematics of a negatively buoyant probe particle in an active fluid, both confined within a spherical domain. The active bath generates a fluctuating flow that pushes the particle with a velocity that is modeled as a colored stochastic noise, characterized by two parameters, the intensity and memory time of the active flow. When the particle departs a little from the bottom of the spherical domain, the configuration is well approximated by a particle in a two-dimensional harmonic trap subjected to the colored noise, in which case an analytical solution exists, which is the base for quantitative analysis. We numerically simulate the dynamics of the particle and use the planar, two-dimensional mean square displacement to recover the activity parameters of the bath. This approach yields satisfactory results as long as the particle remains relatively confined; that is, as long as the intensity of the colored noise remains low.

Investigation of heat transfer phenomenon in a complex wavy divergent channel under the effects of thermal radiation, joule heating and electroosmosis

The heat transfer analysis in electro osmotic flow of nanofluid is studied through the complex wavy channel under the consideration of joule heat and thermal radiation effects. The Ellis fluid is considered a base fluid and gold particles are suspended in them. The complex system of equations is converted to dimensionless form with the help of dimensionless transformation and parameters. The concepts of longer wavelength and lower Reynolds number are utilized to simplify the problem and obtain the exact solution of velocity and temperature distribution by using the built-in command DSolve in the mathematical software MATHEMATICA 13.3. The graphs are plotted with the same software to check the effects of various parameters on velocity, temperature, heat transfer rate, and streamlines with the following range of parameters − 5 ≤ U H S ≤ 5 , 0 ≤ β ≤ 5 , 0 ≤ α ≤ 3 , 0 < k ≤ 5 , 0 ≤ ϕ ≤ 0.04 , 20 ≤ P r ≤ 28 , 0 ≤ R n ≤ 5 . The computational results reported that the electroosmotic parameter, Helmholtz-Smoluchowski velocity, and material parameter reduce the velocity in the initial region and enhance the final region of the channel. It is also noted that the velocity profile exhibits increasing and decreasing behavior in the initial and final region respectively with upgrading the values of volumetric concentration of nanoparticles. The heat transfer rate is strongly affected by material parameters α and β , thermal radiation parameter, Prandtl number, and joule heating and these parameters promote the heat transfer rate of the system. The novel research of the current study shows the examination of the heat transfer analysis of blood-gold nanofluid in the presence of an electrical double layer and thermal radiation with the help of the Ellis nanofluid flow model through a complex symmetric wavy channel. The results of the present investigation are useful for the early detection of renal diseases and monitoring of disease progression because of the unique properties of gold nanoparticles. The role of gold nanoparticles as imaging agents, drug delivery antioxidant properties, biosensing, targeted therapy, and renal clearance makes them the perfect choice for renal diseases.

More considerations about the symmetry of the stress tensor of fluids.

Regarding a recent dispute about the symmetry of the stress tensor of fluids, more considerations are presented. The usual proofs of this symmetry are reviewed, and contradictions between this symmetry and the mechanism of gas viscosity are analyzed for simple gas flows. It is emphasized that these proofs depend on the theorem of angular momentum that assumes that internal forces between any two fluid particles are always along the line connecting them. Without this assumption, from Newton's laws of motion one can only obtain the theorem of angular momentum with an additional term. It is proved within classical continuum mechanics that this additional term represents the total moment of internal forces, and its volume density is similar to the body couple introduced in generalized continuum mechanics. When discrete structure of matter is considered, this term corresponds to the total moment of the forces exerted on the nuclei by the internal electrons. This moment of internal forces may lead to nonsymmetry of the stress tensor and is, in general, nonzero as long as shear stress exists. A nonsymmetrical stress tensor suggested in the literature is discussed in terms of its effects in eliminating the contradictions and simplifying the Navier-Stokes equation. The derivation of this stress tensor for ideal gases based on the kinetic theory of gas molecules is presented, and its form in a general orthogonal curvilinear coordinate system is given. Finally, a possible experimental verification of this nonsymmetrical stress tensor is discussed.

Tiny particles thermal motile in magnetized chemically reacting upper-convective Maxwell stagnation point fluid with radiation

The need to enhance industrial working fluid and material thermal strength for quality output of engineering and domestic devices, has increased diverse studies on non-Newtonian viscous fluid under different constraints. Various architectures and geometries have been considered for thermal propagation of fluid particles. As such, this study addresses thermal motility of tiny particles in magnetized chemically reacting upper-convective Maxwell stagnation point fluid with radiation owing to its usages. A partial-differential model is formulated under some certain assumptions and conditions, and with applicable similarity variables, a transformed invariant coupled ordinary-differential model is obtained. The solutions to the model are determined using Galerkin-weighted residual method. The computed outcomes are quantitatively tabulated and qualitatively demonstrated in graphs. The analysis revealed that the hydrodynamic bounding surface alongside with velocity profiles declines due to augmentation of the magnetic field and Deborah number terms.

Development and validation of filtered drag models for fluidization of low-density Geldart A particles

Filtered drag models have been extensively developed and applied in coarse grid simulation of fluidized beds. However, existing filtered drag models were mainly developed using the particle properties of Fluid Catalytic Cracking (FCC), and these models were found to perform less satisfactorily in predicting flow fields for low-density particles. To broaden the applicability of filtered drag models, this study developed a novel filtered drag model tailored explicitly for low-density Geldart A particles. Additionally, this study investigated the differences in filtering outcomes using various filter types. Statistical analyses revealed significant differences between filters, particularly between the median and other filters. The statistical skewness distribution of the filtered quantity datasets can lead to differences in results between median and mean filters. After analyzing one-marker and two-marker models, it was found that filter type has a more pronounced influence on model performance prediction differences at small filter sizes, while it becomes insignificant at larger filter sizes. Validation studies in fluidized bed simulations found that the two-marker model established based on the Median filter performs best in predicting performance. It is also found that more substantial drag corrections are required in the extremely dense phase domain for low-density particle fluidization systems.