Fluid Regime Research Articles

Improved analytic modeling of the linear Rayleigh–Taylor instability with plasma transport

The Rayleigh–Taylor (R–T) instability with transport effects has long been studied analytically in the neutral fluid regime. How this picture may differ in plasmas has been given less consideration, however. Leveraging previous numerical simulations with plasma viscosity and diffusion of R–T at a binary plasma interface, we show how plasma transport and kinetic effects alter the linear R–T dispersion relation. Our insight informs a much improved analytical dispersion relation, which better matches the simulation data than previously established models. Additionally, we demonstrate the importance of employing asymptotically correct viscosity coefficients in fluid codes for accurately capturing plasma R–T growth.

Same-sided successive-shock HED instability experiments

Inertial confinement fusion (ICF) and high-energy density (HED) physics experiments experience complicated forcing for instability growth and mix due to the ubiquitous presence of multiple shocks interacting with perturbations on multiple material interfaces. One common driver of instability growth is successive shocks from the same direction. However, there is a severe lack of analytic work and modeling validation for same-sided successive shocks since they are extremely difficult to achieve with conventional (non-HED) drivers. Successive shocks access a large instability parameter space; idealized fluid theory [K. O. Mikaelian, Phys. Rev. A 31, 410 (1985)] predicts 15 different interface evolution scenarios for a sinusoidal perturbation. Growth becomes more complex for multi-mode, compressible HED systems. The Mshock campaign is the first experiment in any fluid regime to probe a wide portion of successive shock parameter space. This is enabled by our development of a hybrid direct/indirect drive platform capable of creating independently controllable successive shocks on the National Ignition Facility. These experiments have delivered the first data capable of rigorously challenging our models and their ability to accurately capture Richtmyer–Meshkov growth under successive shocks. Single-mode and two-mode experiments have successfully demonstrated the ability to access and control the various growth scenarios of the shocked interface, including re-inversion, freeze out, and continued growth. Simulations and theoretical modeling are shown to accurately capture the experimental observations in the linear growth phase, giving us confidence in our ICF/HED design codes.

Comparison of physical and physicochemical methods for 3D printing application with the focus on the unconfined uniaxial compression test

For a commercial success of 3D concrete printing, standardisation is necessary to enable industrial production. To select methods for standardisation from the material side, detailed knowledge of suitable methods and of material behaviour is required in advance. Therefore, this study aims to compare different methods for investigating stiff printable mortars during the transition regime of a non-Newtonian fluid to a cohesive frictional material by physical and physicochemical methods focusing on the unconfined uniaxial compression test. The study shows that all methods exhibit comparable progressions, although the results are affected differently by self-heating, material composition and progressive hydration.

Improvement of electrical performance of Photovoltaic cell with incorporating nanofluid flow as cooling system

The present study is about the modeling of laminar flow of testing fluid within the sinusoidal wall in existence of V shaped fins. The heat absorption of testing fluid has been improved with loading nanoparticles and installing fins within the upper side of the pipe. Heat generation in various layers has been calculated and considered as the source term of conduction equations for each solid layer. The fluid regime within the pipe is laminar and equations have been solved in steady state form. The accuracy of the utilized numerical model has been tested based on data of absorber temperature for the previous article. Grid indecency has been examined and the best size of mesh was obtained. With installing fins, the performances of the system have been improved in both views of electrical (0.1%) and thermal (1.12%). Also, outputs showed that the efficacy of fins on thermal and electrical efficiencies for highest amount of inlet velocity (uin) is 14.30% and 39.75% greater than those of uin = 0.06. Increasing velocity can decrease the cell temperature about 7.4% and thermal performance increase about 17%.

Experimental Modeling of Decarbonation Reactions, Resulting in the Formation of CO2 Fluid and Garnets of Model Carbonated Eclogites under Lithospheric Mantle P,T-Parameters

First experimental modeling of decarbonation reactions resulting in the formation of CO2-fluid and Mg, Fe, Ca, and Mn garnets, with composition corresponding to the garnets of carbonated eclogites of types I and II (ECI and ECII), was carried out at a wide range of lithospheric mantle pressures and temperatures. Experimental studies were performed on a multi-anvil high-pressure apparatus of a “split sphere” type (BARS), in (Mg, Fe, Ca, Mn)CO3-Al2O3-SiO2 systems (with compositional variations according to those in ECI and ECII), in the pressure interval of 3.0–7.5 GPa and temperatures of 1050–1450 °C (t = 10–60 h). A specially designed high-pressure cell with a hematite buffering container—preventing the diffusion of hydrogen into the platinum capsule—was used, in order to control the fluid composition. Using the mass spectrometry method, it was proven that in all experiments, the fluid composition was pure CO2. The resulting ECI garnet compositions were Prp48Alm35Grs15Sps02–Prp44Alm40Grs14Sps02, and compositions of the ECII garnet were Prp57Alm34Grs08Sps01–Prp68Alm23Grs08Sps01. We established that the composition of the synthesized garnets corresponds strongly to natural garnets of carbonated eclogites of types I and II, as well as to garnets from xenoliths of diamondiferous eclogites from the Robert Victor kimberlite pipe; according to the Raman characteristics, the best match was found with garnets from inclusions in diamonds of eclogitic paragenesis. In this study, we demonstrated that the lower temperature boundary of the stability of natural garnets from carbonated eclogites in the presence of a CO2 fluid is 1000 (±20) °C at depths of ~90 km, 1150–1250 (±20) °C at 190 km, and 1400 (±20) °C at depths of about 225 km. The results make a significant contribution to the reconstruction of the fluid regime and processes of CO2/carbonate-related mantle metasomatism in the lithospheric mantle.

Prescribing intravenous fluids: a review

This article highlights the multitude of considerations when prescribing intravenous fluids from the perspective of a trainee advanced practitioner, and emphasises that reassessment of the patient is key to safe fluid administration. Having identified that the practice of prescribing intravenous fluids is commonplace in acute care, this article will explore the level of training and education provided to clinicians, and highlights the importance of undertaking a systematic approach in assessing and decision making. In addition, this article will discuss the complexities of prescribing fluids and examine the considerations required for the assessment of fluid status, methods of determining the most appropriate fluid regime and selection of fluid for the patient, and the available evidence and guidance to aid decision making.

Passive cooling of photovoltaic panel by aluminum heat sinks and numerical simulation

One of the biggest problems of generating electricity by photovoltaic panels is that about 80% of the incoming solar energy is transformed into heat. The heat causes the rise of operating temperature of the panel, thereby reducing its efficiency and performance characteristics. In this research, photovoltaic panel was passively cooled by means of aluminum heat sinks with different geometries in order to determine the enhancement of output characteristics. Decrease in temperature by an average of 7.5 °C by means of heat sinks lead to increase in open-circuit voltage of 0.27 V, compared to the reference panel. Based on the experimentally obtained results, software was used to simulate the temperature and velocity fields for a string of three heat sinks, thus obtaining a better insight in heat transfer process of heat sinks. A polyhedral mesh and laminar fluid flow were applied for the simulation, leading to a good agreement between the experimentally obtained and simulated temperatures of the heat sinks, with average difference of about 1 °C. In order to determine the most efficient geometry of the heat sink for passive PV cooling applications, the data obtained by the experiment and simulation were numerically analyzed. The second heat sink, with its overall design (contact area with the panel, fin length, fin spacing), more effectively dissipates accumulated thermal energy to the surrounding air compared to the other two heat sinks. A model was developed to simulate the characteristics of a heat sink under various conditions using the laminar fluid regime and air temperature and the base temperature as input parameters. The results of this study can be used to optimize the design of heat sinks and improve their efficiency in cooling PV panels.

THE DARK SIDE OF BIGUANIDES: A CASE REPORT ON METFORMIN-ASSOCIATED LACTIC ACIDOSIS (MALA)

Metformin-associated lactic acidosis (MALA) is a rare but potentially fatal complication that can occur in a patient on metformin, who had a sudden reduction in the renal function resulting in a raised serum metformin level. We describe a case of MALA who survived with prompt haemodialysis. An elderly female with diabetes on metformin presented with gastrointestinal losses, lethargy and confusion. She was in circulatory shock and despite an aggressive fluid regime, she remained acidotic with an increasing lactate level of > 15 mmol/L. After endotracheal intubation, she was referred to tertiary centre for haemodialysis. Her serum lactate level rapidly fell to a satisfactory range and a progressive recovery followed. We are highlighting this case for its rarity and to serve as a guidance on the early recognition of MALA for fellow clinicians. Despite the high mortality rate, MALA is reversible, and we urge clinicians to expedite haemodialysis as definitive treatment.

Transport mechanism of temporary plugging agent in complex fractures of hot dry rock: A numerical study

Hydraulic fracturing with temporary plugging agents is one of the most promising technologies to improve the thermal efficiency of deep geothermal reservoirs. Understanding the migration and plugging mechanism of temporary plugging agents in artificial fractures is the key to successful fracturing operations. However, there is currently a lack of understanding of the high temperature effect on the migration of temporary plugging agents in fractures. Therefore, based on the Eulerian-Lagrangian description framework, this paper uses the computational fluid mechanics (CFD)-discrete element method (DEM) two-way coupling algorithm to establish a multiphase flow model for the migration of temporary plugging agents in complex fractures. We carried out relevant numerical simulation research and compared with the experimental results. Numerical simulation results show that the main factors affecting the migration of temporary plugging agent include formation temperature, fracture complexity, viscosity of carrier fluid, mass concentration of temporary plugging agent, flow regime of the carrier fluid, and inter-particle friction coefficient. Among these factors, the high temperature effect reduces the amount of temporary plugging agent entering complex branch fractures, thus weakening the plugging efficiency of temporary plugging agent for branch fractures. However, the adverse effect of high temperature on plugging can be overcome by increasing the injection rate of temporary plugging agent and increasing the width of the fracture to improve the plugging efficiency of branch fractures. The numerical results provide important theoretical and practical significance for the design scheme of temporary plugging and diverting fracturing in hot dry rock.

A Depth‐Averaged Description of Submarine Avalanche Flows and Induced Surface Waves

AbstractThis paper develops a depth‐averaged theory to investigate submarine landslides and resulting water waves. The problems here consist of a pure fluid regime and a mixture regime of grains and fluid. Both regimes separate from one another by an interface, which is a material surface for grains. While the downslope velocities of the both phases are assumed to be identical in the mixture regime, the velocity shear causes a rearrangement of grains, which induces a vertical relative motion between the phases. The established theory consists of five coupled conservation equations, which describe the evolution of the pure fluid thickness, the mixture thickness, the solids volume fraction, and depth‐averaged velocities. To handle nonconservative products emerging in the equations, a new coordinate system is introduced to rewrite the equation system in an equivalent form, so that numerical solutions are insensitive to the choice of discretization of nonconservative products, which enables us to accurately characterize the dynamic behaviors of particles in the collapse experiments of underwater particles and describe free‐surface wave profiles. It is shown that the computed results are in good agreement with the experiments reported in previous literatures.

”MINERALOGY OF IGNEOUS COMPLEXES OF WESTERN VOLYN” – THE FIRST FUNDAMENTAL MONOGRAPH ON REGIONAL MINERALOGY IN UKRAINE

The contribution of the authors of the monograph “Mineralogy of igneous complexes of Western Volyn”, headed by Academician Yevhen Kostiantynovych Lazarenko, to the mineralogy of igneous rocks of the region is highlighted. The results of a detailed geological and mineralogical study, a geological and petrographic essay and the characteristics of mineral formation processes of Archean metamorphic and Zhytomyr-Kirovohrad and Osnitsk intrusive as well as dyke-effusive igneous complexes are discussed. It is shown that the materials obtained by the authors of this first fundamental monograph on regional mineralogy of Ukraine, together with the full use of literature at the time, formed the basis for all subsequent studies of Western Volyn, given its prospects for identifying of copper fields within the Volyn series of the Lower Ediacaria flood continental basalts. The obtained results, together with а set of data obtained later, made it possible to justify the need to intensify targeted efforts in the region. In the future, special attention should be paid to continuing the detailed study of the geological structure, mineral composition, petrographic and petrochemical features of rock-ore complexes of Western Volyn, the fluid regime of mineralogenesis of copper-containing flood continental basalts. Further research in the region will contribute to detailing the conditions for the formation of native copper mineralization in traps of the Volyn series in the aspect of assessing their copper ore potential; their results should be used by production geological organizations to optimize prospecting and exploration work in the preparation of promising areas for exploration. The significance of Yevhen Lazarenko’s contribution to regional mineralogical research, which was initiated by the monograph “Mineralogy of igneous complexes of Western Volyn”, is growing under these conditions. The book is still a powerful source of inspiration for geologists who continue the work of an outstanding scientist in the field of Earth sciences and conduct regional mineralogical research not only in Volyn, but also in other regions of Ukraine.

Fluid regime of Olimpiada gold deposit formation

The PTX-parameters of the fluids formed the Olympiada gold deposit were determined using microthermometry and Raman spectroscopy of carbonic (CO2-N2-CH4) and aqueous-carbonic inclusions in quartz. Weakly gold-bearing metamorphic pyrrhotite-quartz veinlets were formed by oxidized (СО2 / СН4 = 10-100) nitrogen-carbon dioxide fluid at temperatures of 410-360 °C and a pressure of 2,4 ± 0,2 kbar. Gold-arsenopyrite mineralization was formed by deep-seated reduced (СО2 / СН4 ~ 1) methane-carbon dioxide-nitrogen fluid in the temperature range of 360-300 °C and pressure of 1,2 ± 0,1 kbar. Gold-antimonite mineralization was formed by nitrogen-methane fluid at temperatures 290-240 °C and pressure 0,8 ± 0,1 kbar. Gold transport was carried out in a boiling environment in carbonic phase.

Flow development and leading edge vorticity in bristled insect wings

Small flying insects such as the tiny thrip Gynaikothrips ficorum have wings with bristles attached to a solid shaft instead of solid membranes. Air passing through the bristle fringe, however, makes bristled insect wings less effective for aerodynamic force production. In this study, we quantified the ability of bristled wings to generate a leading edge vortex (LEV) for lift support during wing flapping, scored its circulation during wing translation, and investigated its behaviour at the stroke reversals. The data were measured in robotic model wings flapping with a generic kinematic pattern at Reynolds number of ~ 3.4, while applying two-dimensional particle image velocimetry. We found that aerodynamic performance due to LEV circulation linearly decreases with increasing bristle spacing. The wings of Gynaikothrips ficorum might thus produce approximately 9% less aerodynamic force for flight than a solid membranous wing. At the stroke reversals, leading and trailing edge vortices dissipate quickly within no more than ~ 2% of the stroke cycle duration. This elevated dissipation makes vortex shedding obsolete during the reversals and allows a quick build-up of counter-vorticity when the wing reverses flapping direction. In sum, our findings highlight the flow conditions associated with bristled wing design in insects and are thus significant for assessing biological fitness and dispersal of insects flying in a viscosity-dominated fluid regime.

Accuracy and Stability Analysis of the Semi-Lagrangian Method for Stiff Hyperbolic Relaxation Systems and Kinetic BGK Model

In this paper, we develop a family of third order asymptotic-preserving (AP) and asymptotically accurate (AA) diagonally implicit Runge–Kutta (DIRK) time discretization methods for the stiff hyperbolic relaxation systems and kinetic Bhatnagar–Gross–Krook (BGK) model in the semi-Lagrangian (SL) setting. The methods are constructed based on an accuracy analysis of the SL scheme for stiff hyperbolic relaxation systems and kinetic BGK model in the limiting fluid regime when the Knudsen number approaches 0. An extra order condition for the asymptotic third order accuracy in the limiting regime is derived. Linear von Neumann stability analysis of the proposed third order DIRK methods are performed to a simplified two-velocity linear kinetic model. Extensive numerical tests are presented to demonstrate the AA, AP, and stability properties of our proposed schemes.

Boundary integral simulations of boundary layers in linear viscoelastic flow

We investigate the disturbance flow generated by the oscillatory motion of a solid particle in linear viscoelastic (LVE) fluids. We begin with one-mode Maxwell fluids and then add Newtonian components so we can examine a spectrum of Weissenberg numbers and frequency parameters. We compute the fluid dynamics using an accurate boundary integral method with third-order accuracy in space. A unique feature of our method is that we can calculate the stress on the particle surface for a prescribed particle velocity profile. It is well known that a boundary layer develops along an infinite plate under oscillatory motion in a Newtonian fluid. However, when the flow becomes viscoelastic, the boundary layers are fundamentally different from those observed in Newtonian fluids. We perform a series of numerical simulations for the geometry of spheroids, dumbbells, and biconcave disks, and characterize streamlines around these particles and shear stress distributions on the surface of the particles. Specifically, two main results emerge from our investigations: (i) there is a sequence of eddies produced in LVE rather than a single one as in the Newtonian fluid case; and (ii) the eddies develop in the interior of the LVE and barely travel, while in the Newtonian fluid, the eddy is generated on the particle surface and propagates into the fluid. Our numerical findings go beyond the well-known dynamical regimes for Newtonian fluids and highlight the level of complexity of particle dynamics in viscoelastic fluids.

Dynamic structural and microstructural responses of a metal–organic framework type material to carbon dioxide under dual gas flow and supercritical conditions

The structural and microstructural responses of a model metal–organic framework material, Ni(3-methyl-4,4′-bipyridine)[Ni(CN)4] (Ni-BpyMe or PICNIC-21), to CO2 adsorption and desorption are reported for in situ small-angle X-ray scattering and X-ray diffraction measurements under different gas pressure conditions for two technologically important cases. These conditions are single or dual gas flow (CO2 with N2, CH4 or H2 at sub-critical CO2 partial pressures and ambient temperatures) and supercritical CO2 (with static pressures and temperatures adjusted to explore the gas, liquid and supercritical fluid regimes on the CO2 phase diagram). The experimental results are compared with density functional theory calculations that seek to predict where CO2 and other gas molecules are accommodated within the sorbent structure as a function of gas pressure conditions, and hence the degree of swelling and contraction in the associated structure spacings and void spaces. These predictions illustrate the insights that can be gained concerning how such sorbents can be designed or modified to optimize the desired gas sorption properties relevant to enhanced gas recovery or to addressing carbon dioxide reduction through carbon mitigation, or even direct air capture of CO2.

Experimental Study of Void Fraction Measurement Using a Capacitance-Based Sensor and ANN in Two-Phase Annular Regimes for Different Fluids

One of the most severe problems in power plants, petroleum and petrochemical industries is the accurate determination of phase fractions in two-phase flows. In this paper, we carried out experimental investigations to validate the simulations for water–air, two-phase flow in an annular pattern. To this end, we performed finite element simulations with COMSOL Multiphysics, conducted experimental investigations in concave electrode shape and, finally, compared both results. Our experimental set-up was constructed for water–air, two-phase flow in a vertical tube. Afterwards, the simulated models in the water–air condition were validated against the measurements. Our results show a relatively low relative error between the simulation and experiment indicating the validation of our simulations. Finally, we designed an Artificial Neural Network (ANN) model in order to predict the void fractions in any two-phase flow consisting of petroleum products as the liquid phase in pipelines. In this regard, we simulated a range of various liquid–gas, two-phase flows including crude oil, oil, diesel fuel, gasoline and water using the validated simulation. We developed our ANN model by a multi-layer perceptron (MLP) neural network in MATLAB 9.12.0.188 software. The input parameters of the MLP model were set to the capacitance of the sensor and the liquid phase material, whereas the output parameter was set to the void fraction. The void fraction was predicted with an error of less than 2% for different liquids via our proposed methodology. Using the presented novel metering system, the void fraction of any annular two-phase flow with different liquids can be precisely measured.

Cattaneo-Christov heat flux effect on Sakiadis magnetohydrodynamic boundary-layer transport phenomena in the Jeffrey fluid

This study aims to perform a numerical simulation of the boundary flow with the characteristic Sakiadis flow of the MHD Jeffrey fluid under the Cattaneo-Christov heat flux model over the horizontal plate. The similarity transformation for the local similarity solution was used to reduce the set of governing equations to non-linear ODE. The equations were solved by using ?dsolve? command with the numeric option for the boundary value problem in MAPLE. Simulations have been carried out for different values of the relaxation retardation times, the Deborah number, the magnetic field parameter, the heat flux relaxation time, the Prandtl number, and the Schmidt parameter. A comparative study of the numerical results from the previously published paper with the present result for the dimensionless velocity gradient over the horizontal plate shows excellent agreement. It has been found that the growth of the Deborah number leads to the dimensionless velocity gradient enhancement, while the increment of the relaxation retardation times parameter and the magnetic field parameter indicates the opposite trend. The heat transfer rate noticeably decreased with an increment in the Prandtl number and thermal relaxation time at the fluid regime. Also, fluid concentration decreases with larger values of the Schmidt parameter.

On the origin of universal cell shape variability in confluent epithelial monolayers.

Cell shape is fundamental in biology. The average cell shape can influence crucial biological functions, such as cell fate and division orientation. But cell-to-cell shape variability is often regarded as noise. In contrast, recent works reveal that shape variability in diverse epithelial monolayers follows a nearly universal distribution. However, the origin and implications of this universality remain unclear. Here, assuming contractility and adhesion are crucial for cell shape, characterized via aspect ratio (r), we develop a mean-field analytical theory for shape variability. We find that all the system-specific details combine into a single parameter α that governs the probability distribution function (PDF) of r; this leads to a universal relation between the standard deviation and the average of r. The PDF for the scaled r is not strictly but nearly universal. In addition, we obtain the scaled area distribution, described by the parameter μ. Information of α and μ together can distinguish the effects of changing physical conditions, such as maturation, on different system properties. We have verified the theory via simulations of two distinct models of epithelial monolayers and with existing experiments on diverse systems. We demonstrate that in a confluent monolayer, average shape determines both the shape variability and dynamics. Our results imply that cell shape distribution is inevitable, where a single parameter describes both statics and dynamics and provides a framework to analyze and compare diverse epithelial systems. In contrast to existing theories, our work shows that the universal properties are consequences of a mathematical property and should be valid in general, even in the fluid regime.

Study of the heat transfer deterioration of supercritical CO2 in vertical pipes using a hybrid RANS/LES method

Heat transfer deterioration (HTD) is one of the core factors affecting the efficiency of the supercritical carbon dioxide (S–CO2) Brayton cycle. When HTD occurs in a heat exchanger, the local wall temperature increases sharply, which may lead to pinch points in the heat exchanger of the circulation system and excessive thermal resistance, resulting in safety problems during the operation of Brayton cycle power generation systems. In studies concerning the HTD of S–CO2, most simulations currently use Reynolds-averaged equations (RANS) to predict and analyze the S–CO2 flowing upward in vertical tube transfer deterioration problems. In this paper, a hybrid RANS/LES method is used for simulations. The RANS model is used to describe the HTD in the near-wall region, and the LES model is used to calculate the flow details in the bulk region and accurately describe the flow regime and vortex structure of a compressible fluid with variable properties. Firstly, the growth and evolution process of HTD is analyzed from the transient-state, and then the corresponding relationship between HTD temperature and velocity field is expounded from the steady-state. Finally, combined with the buoyancy effect, acceleration effect and relaminarization caused by the change of S–CO2 physical properties, the mechanism of the occurrence and recovery of HTD flowing in vertical tubes and the second peak of wall temperature is expounded.