Light Fluid Research Articles

The synergy of light/fluid flow and membrane modification of a novel membrane microalgal photobioreactor for direct air carbon capture

In this paper, a novel microalgal attached membrane photobioreactor based on the modified polyvinylidene difluoride (PVDF) / polyvinyl pyrrolidone (PVP) composite membrane for microalgae direct air carbon capture is developed and optimized. The Computational Fluid Dynamics (CFD) simulation, molecular dynamic study (MDS) and experimental study are adopted to investigate the synergy between light transmission and fluid flow, CO2 transmission mechanism inside the membrane and microalgae cells. The modified composite membrane is proposed and processed to improve the carbon sequestration rate of the microalgal attached membrane photobioreactor (AM-PBR). First, the synergy angle between the light transmission direction and fluid flow direction of the flat-plate photobioreactor (FP-PBR) is analyzed. To improve the synergy of light and fluid flow, the AM-PBR is proposed. Secondly, for the MDS part, the models of PVDF membrane and polytetrafluoroethylene (PTFE) membrane are developed. A three-layer simulation model is proposed to reveal the transmission mechanism of CO2 from the gas-liquid layer to the microalgae cell membrane layer. Several parameters including CO2 diffusion coefficient, CO2 concentration profile and velocity profile of CO2 are analyzed to compare the performance of different membranes and working conditions. Then, for verification of the simulation work, AM-PBR experiments are designed. To further enhance the CO2 transmission and microalgae attached performance, different PVDF/PVP composite membranes are assessed. The carbon sequestration rate of the modified membrane is improved according to the experiments. Finally, the novel microalgae membrane photobioreactor with the modified PVDF/PVP membrane is developed and the carbon sequestration rate of the PBR system is improved. The results showed that the best ratio for PVDF and PVP is 2:1 with 20 wt% solution, and with this modified membrane the carbon sequestration rate of the PVDF/PVP-based AM-PBR is 18.61% higher than the original PVDF-based AM-PBRs. The proposed novel AM-PBR is especially useful for low-concentration CO2 direct air carbon capture.

Rayleigh–Taylor instability under multi-mode perturbation: Discrete Boltzmann modeling with tracers

The two-dimensional Rayleigh–Taylor Instability (RTI) under multi-mode perturbation in compressible flow is probed via the Discrete Boltzmann Modeling (DBM) with tracers. The distribution of tracers provides clear boundaries between light and heavy fluids in the position space. Besides, the position-velocity phase space offers a new perspective for understanding the flow behavior of RTI with intuitive geometrical correspondence. The effects of viscosity, acceleration, compressibility, and Atwood number on the mixing of material and momentum and the mean non-equilibrium strength at the interfaces are investigated separately based on both the mixedness defined by the tracers and the non-equilibrium strength defined by the DBM. The mixedness increases with viscosity during early stage but decreases with viscosity at the later stage. Acceleration, compressibility, and Atwood number show enhancement effects on mixing based on different mechanisms. After the system relaxes from the initial state, the mean non-equilibrium strength at the interfaces presents an initially increasing and then declining trend, which is jointly determined by the interface length and the macroscopic physical quantity gradient. We conclude that the four factors investigated all significantly affect early evolution behavior of an RTI system, such as the competition between interface length and macroscopic physical quantity gradient. The results contribute to the understanding of the multi-mode RTI evolutionary mechanism and the accompanied kinetic effects.

SPILLMOD – МОДЕЛЬ ГИДРОДИНАМИЧЕСКОГО ТИПА ДЛЯ ИНФОРМАЦИОННОЙ ПОДДЕРЖКИ РЕАГИРОВАНИЯ НА РАЗЛИВЫ НЕФТИ В МОРЕ

A mathematical model of the evolution of marine oil spills with taking into account the processes of spreading and weathering, has been implemented as a software package called SPILLMOD. In doing so, a new Eulerian-Lagrangian method for Computational Fluid Dynamics (CFD) has been developed in the context of solving shallow-water-type equations with the capability to handle the situation where advancing/vanishing layer of the light fluid (oil) only partially covers the heavy (water) in a domain with an arbitrary configuration of the coastline shape. When calculating the evaporation of high-viscosity oil types, the effect of reduction the evaporation rate due to molecular diffusion of lighter oil fractions within the oil layer is taken into account. Simulation of the natural dispersion of oil layer is carried out considering multiple factors, such as: sea surface conditions, experimental data on oil film crushing in the wave mixing layer, turbulent diffusion in the upper layer, as well as changes of physical and chemical properties of oil over time. An additional module in the model is designed to estimate domain boundaries of possible spill detection for different sources of uncertainties during oil spill modeling. Modeling examples of application in realistic configuration of port-water areas for an actually occurred emergency situation of oil spill demonstrate the declared qualities of the model as a tool for supporting emergency response operations.

On the Rayleigh–Taylor instability for the two-phase Navier–Stokes equations in cylindrical domains

We are considering the two-phase Navier–Stokes equations with surface tension, modelling the dynamic behaviour of two immiscible and incompressible fluids in a cylindrical domain, which are separated by a sharp interface forming a contact angle with the fixed boundary. In the case that the heavy fluid is situated on top of the light fluid, one expects the effect which is known as Rayleigh–Taylor instability . Our main result implies the existence of a critical surface tension with the following property: In the case that the surface tension of the interface separating the two fluids is smaller than the critical surface tension, Rayleigh–Taylor instability occurs. On the contrary, if the surface tension of the interface is larger than the critical value, one has exponential stability of the flat interfaces. The last part of this article is concerned with the bifurcation of nontrivial equilibria in multiple eigenvalues. The invariance of the corresponding bifurcation equation with respect to rotations and reflections yields the existence of bifurcating subcritical equilibria.

Exact Solutions for Gravity-Segregated Flows in Porous Media

The review is devoted to exact analytical solutions for quasi-2D gravity segregated flows or gravity currents in subterranean porous formations. The problems under consideration are quasi-linear. The driving forces are two components of the buoyancy—one exerting the bulk of the light fluid and one due to the curvilinearity of the interface between the fluids. In the case of homogeneous formation or where the seal slope is negligible, the transport equation is parabolic and allows for a wide set of self-similar solutions. In a large-scale approximation of the buoyancy domination, the governing equation is hyperbolic; the method of characteristics allows for a detailed analytical description of gravity current propagation with final accumulation in the geological trap. Analytical models for leakage via the caprock seal are also discussed. The work was completed by formulating some unsolved problems in segregated flows in porous media.

Rayleigh–Taylor instability in strongly coupled plasma

Rayleigh–Taylor instability (RTI) is the prominent energy mixing mechanism when heavy fluid lies on top of light fluid under the gravity. In this work, the RTI is studied in strongly coupled plasmas using two-dimensional molecular dynamics simulations. The motivation is to understand the evolution of the instability with the increasing correlation (Coulomb coupling) that happens when the average Coulombic potential energy becomes comparable to the average thermal energy. We report the suppression of the RTI due to a decrease in growth rate with increasing coupling strength. The caging effect is expected a physical mechanism for the growth suppression observed in both the exponential and the quadratic growth regimes. We also report that the increase in shielding due to background charges increases the growth rate of the instability. Moreover, the increase in the Atwood number, an entity to quantify the density gradient, shows the enhancement of the growth of the instability. The dispersion relation obtained from the molecular dynamics simulation of strongly coupled plasma shows a slight growth enhancement compared to the hydrodynamic viscous fluid. The RTI and its eventual impact on turbulent mixing can be significant in energy dumping mechanisms in inertial confinement fusion where, during the compressed phases, the coupling strength approaches unity.

Preparation, Characterization, and Antioxidant Properties of Phycocyanin Complexes Based on Sodium Alginate and Lysozyme.

In this study, phycocyanin-sodium alginate/lysozyme complex (PC-SLC) was prepared for the first time and characterized by UV spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and circular dichroism spectroscopy (CD). The stability of PC-SLC under light, temperature, pH and simulated gastrointestinal fluid was investigated. The scavenging ability of the complexes against DPPH and ABTS radicals was determined. The results showed that the complex formed by the mass ratio of SA-LZM of 0.1 showed the highest PC encapsulation rate (89.9 ± 0.374%). The combination of SA and LZM changed the secondary conformation of PC. The PC-SLC complex shows an irregular spherical structure and the spheres are clustered together. Compared with phycocyanin (PC), its thermal stability was obviously improved, but it was still greatly influenced by light. It could exist stably in simulated gastric fluid (SGF) for 2 h and be slowly digested in simulated intestinal fluid (SIF), which helped to promote the absorption of nutrients in the intestinal tract. Meanwhile, the complex PC-SLC showed high scavenging ability for DPPH and ABTS radicals. It can be concluded that the complexes have good antioxidant activity. This study provides an idea for the construction of PC delivery system and makes it more widely used in food industry and other fields.

Simulating a pulsed-power-driven plasma with ideal MHD

We describe a simple practical numerical method for simulating plasma driven within a vacuum chamber by a pulsed power generator. Typically, in this type of simulation, the vacuum region adjacent to the plasma is approximated as a highly resistive, light fluid; this involves computationally expensive solvers describing the diffusion of the magnetic field through this fluid. Instead, we provide a recipe for coupling pulsed power generators to the magnetohydrodynamics (MHD) domain by approximating the perfectly insulating vacuum as a light, perfectly conducting, inviscid MHD fluid and discuss the applicability of this counter-intuitive technique. This much more affordable ideal MHD representation is particularly useful in situations where a plasma exhibits interesting three-dimensional phenomena, either due to the design of the experiment or due to developing instabilities. We verified that this coupling recipe works by modeling an exactly solvable flux compression generator as well as a self-similar Noh-like solution and demonstrated convergence to the theoretical solution. We also showed examples of simulating complex three-dimensional pulsed power devices with this technique. We release our code implementation to the public (see https://github.com/beresnyak/verif_coupling).

From breakup to coiling and buckling regimes in buoyant viscoplastic injections

We study the injection flow of a heavy viscoplastic fluid into a light Newtonian fluid, via modelling and experiments. The injection is carried out downward, via an eccentric inner pipe inside a vertical closed-end outer pipe. This configuration results in a core viscoplastic fluid surrounded by an annular Newtonian fluid. The flow is structured and mixing is negligible. As the injection rate increases in a typical experiment, we observe three distinct flow regimes, associated with the core fluid behaviour, namely the breakup, coiling and buckling (bulging) regimes. In the breakup regime, the core fluid is yielded due to the extension caused by buoyancy, while in the buckling regime the yielding occurs due to the compression promoted by the pressure and the interfacial shear stress applied by the upward flow of the annular fluid. For the coiling regime, the core fluid remains largely unyielded until it exhibits a coiling behaviour. We develop a lubrication approximation model, using the Herschel–Bulkley constitutive equation, with dimensionless flow parameters including the Bingham number, the power-law index, the buoyancy number, the viscosity ratio, the diameter ratio, the eccentricity and the aspect ratio. Based on a reasonable prediction to the yielding onset, the model allows us to classify the flow regimes versus an elegant combination of the dimensionless numbers.

Hydrodynamics explanation for the splitting of higher-charge optical vortices

We show that a two-dimensional hydrodynamics model provides a physical explanation for the splitting of higher-charge optical vortices under elliptical deformations. The model is applicable to laser light and quantum fluids alike. The study delineates vortex breakups from vortex unions under different forms of asymmetry in the beam, and it is also applied to explain the motion of intact higher-charge vortices.

Critical velocity for superfluidity in the one-dimensional mean-field regime: From matter to light quantum fluids

We determine in a nonperturbative way the critical velocity for superfluidity of a generic quantum fluid flowing past a localized obstacle in the one-dimensional mean-field regime. We get exact expressions in the narrow- and wide-obstacle limits and interpolate them numerically using an original relaxation algorithm for the stationary problem. The existence of a Josephson-type critical current across a very high and slowly varying obstacle is discussed. Particle losses, if present, are treated within an adiabatic approach of the dynamics giving results in excellent agreement with full numerics. Relevant for experiments with quantum fluids of matter, of mixed matter-light, and of light, our study paves the way for further nonperturbative investigations in higher dimensions and beyond mean-field theory.

Determination of the discharge coefficient through vent driven by a non-Boussinesq plume in an emptying filling box

The effect of high buoyancy forces due to density contrast between the fluids on either side of the vent on the discharge coefficient Cd is taken into account in the laboratory. Salt water experiments are conducted at small scale in a large fresh water tank with saline to generate buoyancy force. In non-Boussinesq cases, a larger discharge parameter Γd at the vent may make plume-like flow contract further with a smaller value of the discharge coefficient. A nearly twofold time in the non-dimensional form for draining light fluid fully out of the space is observed comparing with time predicted with a constant value of Cd = 0.6 for simple draining flows. A displacement flow theoretical model with virtual source correction at the initial position of an internal source is developed to reveal a time-dependent movement of the layer interface, and the oscillatory amplitude of the interface overshooting during the transient period is found to depend on the two dimensionless geometrical parameters Λ and Θ.

Neurofilament light as a biomarker of axonal degeneration in patients with mild cognitive impairment and Alzheimer's disease.

Cerebrospinal fluid neurofilament light and plasma neurofilament light concentrations are elevated in patients with mild cognitive impairment and Alzheimer's disease. We investigated the clinical relevance of increased neurofilament light concentrations in mild cognitive impairment and Alzheimer's disease patients. In this study, 244 subjects were divided into cognitively normal control (n = 67), stable mild cognitive impairment (n = 52), progressive mild cognitive impairment (n = 68), and Alzheimer's disease (n = 57). Linear regression examined the relationships between neurofilament light levels in cerebrospinal fluid or plasma and the diagnostic group. The relationships between neurofilament light and other biomarkers were assessed by Spearman correlation. Linear mixed-effects models were used to test cerebrospinal fluid and plasma neurofilament light as predictors of Alzheimer's disease characteristics, including cognition, cortical glucose metabolism, and brain structure. Cerebrospinal fluid and plasma neurofilament light levels were significantly elevated in Alzheimer's disease. Still, the correlations between neurofilament light and other cerebrospinal fluid biomarkers within the diagnostic groups were often not statistically significant. In addition, the diagnostic accuracy of cerebrospinal fluid and plasma neurofilament light for progressive mild cognitive impairment and Alzheimer's disease was almost the same as that of cerebrospinal fluid total tau (T-tau). It is phosphorylated tau (P-tau) and high cerebrospinal fluid. Neurofilament light predicted conversion from mild cognitive impairment to Alzheimer's disease. A high neurofilament light is related to poor cognition, low cerebral metabolism, hippocampal atrophy, and ventricular enlargement caused by Alzheimer's disease. Our work further identifies cerebrospinal fluid neurofilament light and plasma neurofilament light as biomarkers of axonal degeneration in patients with mild cognitive impairment and Alzheimer's disease.

Lipogranulema of the hernia sac. Clinical case

Lipogranulomas in surgical practice, are the most often encountered in the mammary glands, penis and facial area associated with subcutaneous injections for cosmetic purposes of various types of fillers that cause chronic granulomatous inflammation. Atypical localization occurs due to the development of reactions to foreign bodies after traumatic injuries and reactions to suture material used in surgical interventions. The article presents a clinical case of revealing a large peritoneal lipogranuloma localized in the area of the hernial sac in a patient who 7 years ago suffered from endometrial cancer and underwent extirpation of the uterus using median incision access. Subsequently, the patient was treated for a long time in an outpatient care because of the ligature abscesses with the formation of fistulas; several rough ligatures were removed from the subcutaneous tissue. Lipogranuloma, found in the wall of the hernial sac measuring 15 × 6 × 5 cm, covered from all sides with an unaltered peritoneum, contained a cystic cavity with a light fluid, thick synthetic ligatures of a braided structure were present in the cyst wall. The use of large-diameter braided non-absorbable sutures for suturing the peritoneum does not meet modern requirements for the use of suture material and can cause complications.

Zinc Isotopes of the Mariana and Ryukyu Arc‐Related Lavas Reveal Recycling of Forearc Serpentinites Into the Subarc Mantle

AbstractMantle source heterogeneity of arc‐related magmas was traditionally thought to be predominantly affected by slab‐derived components. However, the role of forearc serpentinites in causing subarc mantle heterogeneity remains poorly constrained. Here, we present the first Zn isotope data for lavas from the Mariana and Ryukyu subduction zones. Notably, the δ66Zn values of basaltic lavas from the Mariana arc (0.16–0.18‰) and southern Okinawa Trough (0.15–0.17‰) are generally lower (∼0.10‰) than those of the mid‐ocean ridge basalts (MORB) (0.27 ± 0.05‰). Since mantle melting and magmatic differentiation respectively induce heavy Zn isotope enrichment in primary and evolved magmas, while melt extraction yields the limited Zn isotope fractionation in the mantle, lavas with low δ66Zn values thus potentially indicate the addition of subducted components. The negative correlation between the δ66Zn values and the Ba/La ratios of the basaltic lavas suggests the involvement of isotopically light fluids in their mantle sources. Forearc serpentinites are typically characterized by extremely light Zn isotope compositions. Such forearc materials were likely dragged downward to subarc depths and released isotopically light Zn in fluids to modify the overlying mantle wedge, thereby producing low δ66Zn values in arc‐related magmas. Beyond subarc depths, forearc serpentinites are broken down completely, so light Zn isotope fluids are absent. Accordingly, the basalts from the middle Mariana and Okinawa Trough display MORB‐like δ66Zn values. Collectively, Zn isotope provides new insights into the role of the recycling of forearc serpentinites in generating chemical heterogeneity in the mantle source of subduction‐related magmas.

RK4 and HAM Solutions of Eyring-Powell Fluid Coating Material with Temperature-Dependent-Viscosity Impact of Porous Matrix on Wire Coating Filled in Coating Die: Cylindrical Co-ordinates.

In this work, we studied the impacts of transmitting light, nonlinear thermal, and micropolar fluid mechanics on a wire surface coating utilizing non-Newtonian viscoelastic flow. Models with temperature-dependent variable viscosity were used. The boundary layer equations governing the flow and heat transport processes were solved using the Runge–Kutta fourth order method. A distinguished constituent of this study was the use of a porous matrix that acted as an insulator to reduce heat loss. In this paper we discuss the effects of numerous development parameters, including , , and (non-Newtonian parameter, heat-producing parameter, viscosity parameter, variable viscosity parameter, porosity parameter, and Brinkman number, respectively). Furthermore, the effects of two other parameters, D and M, are also discussed as they relate to velocity and temperature distributions. We observed that the velocity profiles decreased with increasing values of . Fluid velocity increased as the values of , and increased, while it decreased when the values of , and increased. For increasing values of , the temperature profile showed increasing behavior, while showed decreasing behavior. Furthermore, the present work is validated by comparison with HAM and previously published work, with good results.

Statistical characteristics of turbulent mixing in spherical and cylindrical converging Richtmyer–Meshkov instabilities

In this paper, the Richtmyer–Meshkov instabilities in spherical and cylindrical converging geometries with a Mach number of approximately 1.5 are investigated by using the high resolution implicit large eddy simulation method, and the influence of the geometric effect on the turbulent mixing is investigated. The heavy fluid is sulphur hexafluoride (SF6), and the light fluid is nitrogen (N2). The shock wave converges from the heavy fluid into the light fluid. The Atwood number is 0.678. The total structured and uniform Cartesian grid node number in the main computational domain is 20483. In addition, to avoid the influence of boundary reflection, a sufficiently long sponge layer with 50 non-uniform coarse grids is added for each non-periodic boundary. Present numerical simulations have high and nonlinear initial perturbation levels, which rapidly lead to turbulent mixing in the mixing layers. Firstly, some physical-variable mean profiles, including mass fraction, Taylor Reynolds number, turbulent kinetic energy, enstrophy and helicity, are provided. Second, the mixing characteristics in the spherical and cylindrical turbulent mixing layers are investigated, such as molecular mixing fraction, efficiency Atwood number, turbulent mass-flux velocity and density self-correlation. Then, Reynolds stress and anisotropy are also investigated. Finally, the radial velocity, velocity divergence and enstrophy in the spherical and cylindrical turbulent mixing layers are studied using the method of conditional statistical analysis. Present numerical results show that the geometric effect has a great influence on the converging Richtmyer–Meshkov instability mixing layers.

Hydrodynamics of noncircular vortices in beams of light and other two-dimensional fluids

The motion of noncircular two-dimensional vortices is shown to depend on a form of coupling between vortex ellipticity and the gradient of fluid density. The approach is based on the perspective that an elliptic vortex can be described as the projection of a virtual construct, a circular vortex with a symmetry axis that is tilted with respect to the direction of propagation. The resulting kinetic equation offers insights into how tilt and vortex velocity coevolve in few-body nonequilibrium settings such as vortex pair nucleation and annihilation. The model is developed and applied in association with optical vortices, and optical experiments are used to verify its predictive power. It is valid for quantum fluids and classical hydrodynamics settings as well.

Roles of degenerate quantum plasma temperature and stationary heavy nucleus species in nucleus-acoustic shock waves

The warm degenerate plasma model (on the basis of warm degenerate inertialess electron species, warm dissipative inertial light nucleus species, and stationary heavy nucleus species) is considered. The effects of degenerate plasma temperature and stationary heavy nucleus species on the basic features of cylindrical and spherical nucleus-acoustic shock waves propagating in such a warm degenerate plasma system are investigated. The reductive perturbation method (which is valid for small amplitude shock waves) and special stretched co-ordinates (which corresponds to the omission of the dispersion effect, and is appropriate for the monotonic shock waves) are employed. The kinematic viscous force acting in the light nucleus fluid is the only source of dissipation, and is responsible for the formation of monotonic shock waves. It is observed that the basic features of these monotonic shock waves are significantly modified by the effects of degenerate plasma temperature, ultra-relativistically degenerate electron species, and stationary heavy nucleus species. The applications of this new plasma model (defined by generalized Chandrasekhar equation of state which is also valid for finite temperature) in the cold, as well as hot white dwarfs are addressed.

Explorations on footprints of salt-rich fluid and salt-depleted fluid immiscibility in hydrothermal systems: Insights from divergent partitioning of sulfate and perchlorate in the ZnSO4–Zn(ClO4)2–H2O system

A variety of salt fluids (e.g., aqueous Li2SO4, ZnSO4 and UO2SO4 fluid) were observed to separate into a heavy salt-rich fluid (F1) and a light salt-depleted fluid (F2) when heated to appropriate temperatures. The F1–F2 immiscibility (FFI) likely provides an efficient pathway for hydrothermal transport and accumulation of certain ore elements and influences the compositional evolution of hydrothermal fluids, as it considerably concentrates these elements into the F1 phase. However, geological studies to date have paid little attention to the occurrence and influence of this kind of fluid immiscibility. The discrepancy may be explained from two perspectives. First, the complex pressure–temperature–composition (P–T–x) conditions of geological fluids may destabilize the FFI or suppress its occurrence. Alternatively, the FFI in geological fluids may be neglected during geologic investigations due to a lack of knowledge. To bridge the gap between experimental research and geological studies, this study aims to reveal more properties of the FFI and establish some geological constraints for discerning the FFI in geological systems. The partitioning behaviors of sulfate (FFI-relevant component) and perchlorate (FFI-irrelevant component) during the FFI and boiling process in the ZnSO4–Zn(ClO4)2–H2O system were quantified using Raman spectroscopic analyses integrated with the mass conservation law. Results show inconsistent partitioning behaviors of SO42− and ClO4− during the FFI; SO42− is highly concentrated into the F1 phase relative to the light F2 phase, while ClO4− partitions almost equally between the two phases. On the contrary, SO42− and ClO4− are concentrated proportionally in the residual liquid with boiling. Accordingly, some possible geological constraints, in addition to microthermometry, are postulated for the identification of the FFI in hydrothermal fluids, including (a) the P–T–x trajectory of the fluid intersecting with the FFI's stability region; (b) fluid inclusions showing divergent contents of FFI-relevant components but consistent concentrations of FFI-irrelevant components. This study sheds new light on the research of the salt-rich fluid and salt-depleted fluid immiscibility in geological systems.