Fluid Flow Systems Research Articles

RETRACTED ARTICLE: Discovery of nanoscale sanal flow choking in cardiovascular system: exact prediction of the 3D boundary-layer-blockage factor in nanotubes

Evidences are escalating on the diverse neurological-disorders and asymptomatic cardiovascular-diseases associated with COVID-19 pandemic due to the Sanal-flow-choking. Herein, we established the proof of the concept of nanoscale Sanal-flow-choking in real-world fluid-flow systems using a closed-form-analytical-model. This mathematical-model is capable of predicting exactly the 3D-boundary-layer-blockage factor of nanoscale diabatic-fluid-flow systems (flow involves the transfer of heat) at the Sanal-flow-choking condition. As the pressure of the diabatic nanofluid and/or non-continuum-flows rises, average-mean-free-path diminishes and thus, the Knudsen-number lowers heading to a zero-slip wall-boundary condition with the compressible-viscous-flow regime in the nanoscale-tubes leading to Sanal-flow-choking due to the sonic-fluid-throat effect. At the Sanal-flow-choking condition the total-to-static pressure ratio (ie., systolic-to-diastolic pressure ratio) is a unique function of the heat-capacity-ratio of the real-world flows. The innovation of the nanoscale Sanal-flow-choking model is established herein through the entropy relation, as it satisfies all the conservation-laws of nature. The physical insight of the boundary-layer-blockage persuaded nanoscale Sanal-flow-choking in diabatic flows presented in this article sheds light on finding solutions to numerous unresolved scientific problems in physical, chemical and biological sciences carried forward over the centuries because the mathematical-model describing the phenomenon of Sanal-flow-choking is a unique scientific-language of the real-world-fluid flows. The 3D-boundary-layer-blockage factors presented herein for various gases are universal-benchmark-data for performing high-fidelity in silico, in vitro and in vivo experiments in nanotubes.

Machine learning to identify geologic factors associated with production in geothermal fields: a case-study using 3D geologic data, Brady geothermal field, Nevada

In this paper, we present an analysis using unsupervised machine learning (ML) to identify the key geologic factors that contribute to the geothermal production in Brady geothermal field. Brady is a hydrothermal system in northwestern Nevada that supports both electricity production and direct use of hydrothermal fluids. Transmissive fluid-flow pathways are relatively rare in the subsurface, but are critical components of hydrothermal systems like Brady and many other types of fluid-flow systems in fractured rock. Here, we analyze geologic data with ML methods to unravel the local geologic controls on these pathways. The ML method, non-negative matrix factorization with k-means clustering (NMFk), is applied to a library of 14 3D geologic characteristics hypothesized to control hydrothermal circulation in the Brady geothermal field. Our results indicate that macro-scale faults and a local step-over in the fault system preferentially occur along production wells when compared to injection wells and non-productive wells. We infer that these are the key geologic characteristics that control the through-going hydrothermal transmission pathways at Brady. Our results demonstrate: (1) the specific geologic controls on the Brady hydrothermal system and (2) the efficacy of pairing ML techniques with 3D geologic characterization to enhance the understanding of subsurface processes.

Giant Seafloor Depressions Caused by Slope Failures and Bottom Currents on the Namibia Continental Margin

AbstractMore than 100 circular, elongate or crescent‐shaped very large seafloor depressions were found on the southern Namibian continental margin in water depths between 900 and 1700 m. These depressions show extraordinary sizes of up to 3 km diameter and 180 m depth. Multichannel seismic and bathymetric data show the influence of bottom currents on their morphology through prograding infills on the upcurrent and erosion on the downcurrent flanks, thus creating a crescent morphology in the largest depressions. Although their seafloor morphology resembles pockmarks related to seafloor fluid seepage, no indications for an active fluid flow system were observed in the area. Some depressions show extensive underlying cut‐and‐fill sequences that could be traced down to slope failure structures and deposits at depth. A correlation to ODP drill site 1085 indicates a continuous development of seafloor depressions for ∼10 Ma, documented by successive stages of infilling, erosion and size variations. Analysis of the seismic reflection data suggests that these depressions formed through the interaction of bottom currents with existing seafloor morphology. The equilibrium seafloor of the continental margin was initially disturbed by mass‐wasting events, common occurrences in the region. Subsequently, ongoing sedimentation in their vicinity was affected by ocean bottom currents, leading to the preservation and constant re‐shaping of seafloor depressions until recent times. This study thus highlights the ability of continental slope sedimentation under bottom‐current influence to produce unique seafloor features over long geological time scales.

Fracture networks in shale-hosted igneous intrusions: Processes, distribution and implications for igneous petroleum systems

Igneous intrusions in sedimentary basins can influence basin-scale fluid flow and petroleum systems in various ways. They may act as barriers, preferential pathways or even reservoirs for fluids. The fracture networks of intrusions usually represent the main control of their hydraulic properties. However, our understanding of different fracturing mechanisms and their quantitative effect on fracture network properties remains limited, and good field examples are sparse. Here, we present a comprehensive field study from the Neuquén Basin, Argentina, using a reservoir-scale outcrop of a sill complex emplaced in organic-rich shale, which constitutes a direct analogue of oil-producing fractured igneous reservoirs. We provide field evidence of various fracturing mechanisms affecting the fracture network, including cooling joints, bituminous dykes, hydrothermal veins, and tectonic faults. Using high-resolution digital fracture network quantification, we then tie these fracture mechanisms to spatial variations of fracture orientation, intensity and connectivity. Our results indicate that all observed fracture types are involved in hydrocarbon migration and/or storage. Bitumen of very high thermal grade within the intrusions implies migration of hydrocarbons into the sills in a destructive high-temperature environment. Importantly, bitumen dykes and faults locally alter the fracture network, creating zones of strongly increased fracture intensity and connectivity and therefore improved reservoir properties.

Epigenetic-Hydrothermal Fluorite Veins in a Phosphorite Deposit from Balaton Highland (Pannonian Basin, Hungary): Signatures of a Regional Fluid Flow System in an Alpine Triassic Platform

The middle Anisian extensional tectonics of the Neotethyan realm developed a small, isolated carbonate platform in the middle part of the Balaton Highland (western Hungary), resulted in the deposition of uranium-bearing seamount phosphorite on the top of the drowned platform and produced some epigenetic fluorite veins in the Middle Triassic sequence. The stable C-O isotope data of carbonates are shifted from the typical Triassic carbonate ranges, confirming the epigenetic-hydrothermal origin of veining. Primary fluid inclusions in fluorite indicate that these veins were formed from low temperature (85–169 °C) and high salinity NaCl + CaCl2 + H2O type (apparent total salinity: 15.91–22.46 NaCl wt%) hydrothermal fluids, similar to parent fluids of the Alpine-type Pb-Zn deposits. These findings indicate that the Triassic regional fluid circulation systems in the Alpine platform carbonates also affected the area of the Balaton Highland. This is also in agreement with the previously established palinspatic tectonic reconstructions indicating that the Triassic carbonate and basement units in the Balaton Highland area were a part of the Southern Alpine. Similar fluorite veining in phosphorite deposits is also known in the Southern Alpine areas (e.g., Monte San Giorgi, Italy). Raman spectroscopic analyses detected H2 gas in the vapor phase of the fluid inclusions and a defect-rich fluorite structure in violet to black colored growth zones. This unique phenomenon is assumed to be the result of interaction between the uranium-rich phosphorite and the parent fluids of the epigenetic fluorite veins.

Dynamics of aluminum oxide and copper hybrid nanofluid in nonlinear mixed Marangoni convective flow with entropy generation: Applications to renewable energy

One of the hottest topics in industrial and engineering applications of applied mathematics is the advances in nanotechnology particularly in nanofluids, hybrid nanofluids which consist of a typical base fluid saturated with nano-size metallic particles with enhanced thermophysical properties. In this regard, current study reports an entropy nature of steady, laminar, relative contributions of thermal and solutal Marangoni convections on passage in Casson Al2O3−Cu−H2Ohybrid nanofluid stream past over a disk under the impact of nonlinear heat source/sink, viscous dissipation, radiation, and nonlinear convection. Suitable similarity transformation is apt to reduce the governing partial differential equations to a series of ordinary differential equations. The obtained nonlinear ODE set is then solved numerically by using bvp4c method. The impact of various pertinent flow parameters on the velocity, thermal, concentration, entropy production, rate of heat and mass transfer fields are discussed in detail through graphs. The results reveal that, boost up values of Marangoni number and radiation parameter inclines the heat transfer of the fluid flow system. The upsurge in Exponential heat source/ sink parameter and thermal source/sink parameter inclines the thermal profile. Further, increase in value of volume fraction inclines the rate of mass transfer.

Collective influence of substrate chemistry with physiological fluid shear stress on human umbilical vein endothelial cells.

In the treatment of cardiovascular diseases, vascular scaffold materials play an extremely important role. The appropriate substrate chemistries and 15 dynes/cm2 physiological fluid shear stress (FSS) are both required to ensure normal physiological activity of human umbilical vein endothelial cells (HUVECs). The present study reported the collective influence of substrate chemistries and FSS on HUVECs in the sense of its biological functions. The CH3 , NH2 , and OH functional groups were adopted to offer a variety of substrate chemistries on glass slides by the technology of self-assembled monolayers, whereas FSS was generated by a parallel-plate fluid flow system. Substrate chemistries on its own by no means had noticeable effects on eNOS, ATP, NO, and PGI2 expressions, while FSS stimuli enhanced their production. While substrate chemistries, as well as FSS, were both exerted, the releases of ATP, NO, and PGI2 were dependent on substrate chemistries. Study of F-actin organization and focal adhesions (FAs) formation of HUVECs before FSS exposure proves that F-action organization and FAs formation followed similar chemistry-dependence. Hereby proposed a feasible mechanism, that is, the F-actin organization and FAs formation of HUVECs are controlled by substrate chemistries, further advancing the modulation of FSS-triggered responses of HUVECs.

Focused methane migration formed pipe structures in permeable sandstones: Insights from uncrewed aerial vehicle‐based digital outcrop analysis in Varna, Bulgaria

AbstractFocused fluid flow shapes the evolution of marine sedimentary basins by transferring fluids and pressure across geological formations. Vertical fluid conduits may form where localized overpressure breaches a cap rock (permeability barrier) and thereby transports overpressured fluids towards shallower reservoirs or the surface. Field outcrops of an Eocene fluid flow system at Pobiti Kamani and Beloslav Quarry (ca 15 km west of Varna, Bulgaria) reveal large carbonate‐cemented conduits, which formed in highly permeable, unconsolidated, marine sands of the northern Tethys Margin. An uncrewed aerial vehicle with an RGB sensor camera produces ortho‐rectified image mosaics, digital elevation models and point clouds of the two kilometre‐scale outcrop areas. Based on these data, geological field observations and petrological analysis of rock/core samples, fractures and vertical fluid conduits were mapped and analyzed with centimetre accuracy. The results show that both outcrops comprise several hundred carbonate‐cemented fluid conduits (pipes), oriented perpendicular to bedding, and at least seven bedding‐parallel calcite cemented interbeds which differ from the hosting sand formation only by their increased amount of cementation. The observations show that carbonate precipitation likely initiated around areas of focused fluid flow, where methane entered the formation from the underlying fractured subsurface. These first carbonates formed the outer walls of the pipes and continued to grow inward, leading to self‐sustaining and self‐reinforcing focused fluid flow. The results, supported by literature‐based carbon and oxygen isotope analyses of the carbonates, indicate that ambient seawater and advected fresh/brackish water were involved in the carbonate precipitation by microbial methane oxidation. Similar structures may also form in modern settings where focused fluid flow advects fluids into overlying sand‐dominated formations, which has wide implications for the understanding of how focusing of fluids works in sedimentary basins with broad consequences for the migration of water, oil and gas.

One-step versus two-step dolomite calcitization (dedolomitization): differences and inferences

Polycrystalline calcite pseudomorphs after dolomite can exhibit mosaic or drusy fabric caused by replacement of the dolomite by calcite (one-step dedolomitization) or dolomite dissolution followed by calcite cementation (two-step dedolomitization), respectively. This study discusses the differences between the two types and interprets the characteristics of the fluid causing them. Conclusions drawn here are founded on a microscopic and petrophysical examination of an outcrop of Tuwaiq Mountain Formation, central Arabian Peninsula. Petrographic examination shows that dedolomite has distinct microfabrics in each part of the section. The lower part of the section is not affected by dolomite calcitization, the middle part is dominated by replacement fabrics, and the upper part is dominated by dissolution and/or cementation fabrics. Petrophysical examination shows a wider range of porosity and permeability values for the upper part of the section, relative to the middle and lower parts. One-step dedolomitization is characterized by preservation of the external morphology of the parent dolomite, confinement to the volume previously occupied by the dolomite, development of intracrystalline porosity and permeability that allows the fluid to maintain contact with the reaction front, and no significant effect on porosity of the original rock. Two-step dedolomitization is characterized by corrosion of the external morphology of the parent dolomite, association with other forms of calcite cementation, development without intracrystalline porosity and permeability, and positive or negative effects on the porosity. While one-step dedolomitization appears to occur within a stagnant zone of fluid circulation, the two-step dedolomitization is considered to reflect an active fluid-flow system.

A variable time-stepping algorithm for the unsteady Stokes/Darcy model

This report considers a variable time-stepping algorithm proposed by Dahlquist, Liniger and Nevanlinna and discusses its application to the unsteady Stokes/Darcy model. Although long-time forgotten and little explored, the algorithm performs advantages in variable time-stepping analysis of various fluid flow systems, including the coupled Stokes/Darcy model. We first prove that the approximate solutions to the unsteady Stokes/Darcy model are unconditionally stable due to the G-stability of the method. Then variable time-stepping error analysis follows from the combination of G-stability and consistency of the method. Numerical experiments verify the theoretical results, demonstrating both accuracy and stability of the algorithm.

Invariant solutions of the supersymmetric version of a two-phase fluid flow system

A supersymmetric extension of a two-phase fluid flow system is formulated. A superalgebra of Lie symmetries of the supersymmetric extension of this system is computed. The classification of the one-dimensional subalgebras of this superalgebra into 63 equivalence classes is performed. For some of the subalgebras, it is found that the invariants have a non-standard structure. For six selected subalgebras, the symmetry reduction method is used to find invariants, orbits of the subgroups and reduced systems. Through the solutions of the reduced systems, the most general solutions are expressed in terms of arbitrary functions of one or two fermionic and one bosonic variables.

An experimental technique to simulate and measure leakages in twin-screw compressor

The phenomenon of leakages through various clearances in the twin-screw compressor and its accurate prediction affect its design and performance. The blowhole leakage within the twin-screw compressor is estimated by previous researchers using the convergent nozzle equation, which has certain idealized assumptions and hence has a scope of improvement considering the actual phenomena taking place within the screw compressor. The mathematical model presented in this study takes into account, the shape of a gap and its geometric dimensions, the parameters before and after the gap, the gas friction and the local resistance at entry and exit. An iterative model is used to calculate the leakage rate through the blowhole cross-sections at different pressure differences. The analytical results for the leakage using the mathematical models are verified experimentally by simulating the leakages through the circular cross section convergent nozzles of different sizes at different pressure differences. The experimental study along with analytical deduction suggests suitable multiplier to estimate the blowhole leakages within ±7.2%. This methodology may be extended to estimate the other types of leakages occurring dynamically within the screw compressor and fluid flow systems.

A novel decoupled second-order time marching scheme for the two-phase incompressible Navier–Stokes/Darcy coupled nonlocal Allen–Cahn model

We construct a novel second-order time marching scheme with the full decoupling structure to solve a highly coupled nonlinear two-phase fluid flow system consisting of the nonlocal mass-conserved Allen–Cahn equation where two types of flow regimes are considered (Navier–Stokes and Darcy). We achieve the full decoupled structure by introducing a nonlocal variable and designing an additional ordinary differential equation for it which plays the key role to maintain the unconditional energy stability. The whole scheme is built upon the pressure correction/ quadratization approach for the fluid equation and nonlinear double-well potential, respectively. At each time step, one only needs to solve several independent elliptic equations with constant coefficients illustrating the high practical efficiency. We strictly prove that the scheme satisfies the unconditional energy stability, and carry out various numerical simulations to prove its stability and accuracy numerically, such as spinodal decomposition and fingering instability due to the continuous injection flow, etc.

Stochastic Fluid Models with Positive Jumps at Level Zero

This paper is interested in studying a type of production models-stocks that can be seen as a stochastic fluid flow system with upward jumps at level zero. The joint distribution of the stocks level and the controlling Markov process is governed by two differential systems with specific boundary conditions. The uniqueness of the solution of this problem has been proved. Also, a unified solution with no distinction between singular or invertible drift matrix is proposed. The mathematical expectation is therefore derived. This method is based on the uniformization technique, which is acknowledged by its numerical stability and accuracy. A comparative study with a spectral-based solution is achieved to confirm this statement.

Numerical simulation of periodic MHD casson nanofluid flow through porous stretching sheet

The perspective of this paper is to characterize a Casson type of Non-Newtonian fluid flow through heat as well as mass conduction towards a stretching surface with thermophoresis and radiation absorption impacts in association with periodic hydromagnetic effect. Here heat absorption is also integrated with the heat absorbing parameter. A time dependent fundamental set of equations, i.e. momentum, energy and concentration have been established to discuss the fluid flow system. Explicit finite difference technique is occupied here by executing a procedure in Compaq Visual Fortran 6.6a to elucidate the mathematical model of liquid flow. The stability and convergence inspection has been accomplished. It has observed that the present work converged at, Pr ≥ 0.447 indicates the value of Prandtl number and Le ≥ 0.163 indicates the value of Lewis number. Impact of useful physical parameters has been illustrated graphically on various flow fields. It has inspected that the periodic magnetic field has helped to increase the interaction of the nanoparticles in the velocity field significantly. The field has been depicted in a vibrating form which is also done newly in this work. Subsequently, the Lorentz force has also represented a great impact in the updated visualization (streamlines and isotherms) of the flow field. The respective fields appeared with more wave for the larger values of magnetic parameter. These results help to visualize a theoretical idea of the effect of modern electromagnetic induction use in industry instead of traditional energy sources. Moreover, it has a great application in lung and prostate cancer therapy.

Observer Design for a Class of Semilinear Hyperbolic PDEs With Distributed Sensing and Parametric Uncertainties

We study a class of heterodirectional semilinear hyperbolic partial differential equations, where the distributed state vector is partially measured. An observer estimating the unmeasured part of the state vector is designed. The design is, for instance, applicable to multiphase 1-D fluid models, where the pressure is measured, but the distributed flow and phase concentrations are not. Furthermore, the observer is extended to systems with parametric uncertainties appearing in the dynamics of the unmeasured part of the state. While required to be linear in the uncertain parameter, the uncertain term may be nonlinear in the state, even in the unmeasured part of the state. Terms of this type appear often in applications and cover, for instance, viscous drag in fluid flow systems. A noteworthy property of the design is that convergence of the state estimate is achieved without requiring persistent excitation. Two example applications are presented, and the design is illustrated in a simulation.

Heterogeneous Catalysts Using Strontium Oxide Agglomerates Depositing upon Titanium Plate for Enhancing Biodiesel Production

Strontium oxide (SrO) is an effective catalyst for transesterification. SrO powder that is firmly deposited onto a light titanium plate (TiO2_P), denoted as SrO/TiO2_P, can be reinforced by forming strontium titanate (SrTiO3) at the interface. Exposed SrO agglomerates can promote subsequent continuous transesterification process. In this work, conversion efficiency and production of biodiesel from olive oil on SrO/TiO2_P is investigated. The as-designed SrO/TiO2_P was followed by dip-coating and heat treatment. The physical properties of SrO/TiO2_P were verified through ASTM D3359; the chemical structures before and after transesterification, were respectively identified by X-ray photoelectron spectroscopy and Raman spectroscopy. A focused microwave heating system was utilized for transesterification. In the optimized sample SrO/TiO2_P (x) (x = 0.5 M), SrO firmly bonds with TiO2_P and forms the SrTiO3 structure. With the support of TiO2_P, the tested oil with SrO agglomerates subsequently reacts with SrO under microwave heating. The biodiesel conversion rate reaches 87.7% after a reaction time of 4 min, while the biodiesel product has an average of 39.37 MJ/kg of combustion heat and less than 1 vol% of water content. The as-designed SrO/TiO2_P (0.5) thus has great potential for biodiesel production and is promising with high stability in particular for a continuous fluid flow system.

Heat Transfer From Convecting Magma Reservoirs to Hydrothermal Fluid Flow Systems Constrained by Coupled Numerical Modeling

AbstractMagma flow, heat conduction, and hydrothermal fluid flow control the heat transfer through the upper crust. Magmatic‐hydrothermal activity is essential for the utilization of geothermal energy, formation of ore deposits, and predictions of volcanic hazards, but the interplay between magmatic and hydrothermal processes is not well constrained due to the lack of adequate scientific tools. Simulation results from our novel coupled numerical model resolving both magma (Navier‐Stokes) and hydrothermal (Darcy) flow quantify the influence of magma convection and rock permeability on energy transfer. Convection of a hot‐dry rhyolitic magma has an accelerating effect of up to 15% on the cooling of the reservoir by enhancing the heat transfer toward the magma‐hydrothermal interface. However, at high permeabilities and high brittle‐ductile transition temperatures, magma flow can also have a secondary decelerating effect, because it prevents efficient permeability creation and entrainment of hydrothermal fluids at the edges of the magma reservoir.

Discrete-time model-based output regulation of fluid flow systems

Model-based discrete-time output regulator design is proposed for fluid flow systems using a geometric approach. More specifically, a class of vortex shedding and falling thin film phenomena modelled by complex Ginzburg–Landau equation (CGLE) and Kuramoto–Sivashinsky equation (KSE) are considered. Differently from a traditional continuous-time controller design, a novel discrete-time modelling technique is proposed in a general infinite-dimensional state-space setting, which does not pertain any spatial approximation or model reduction, and preserves model intrinsic properties (such as stability, controllability and observability). Based on the time discretized plant model (CGLE and KSE systems) by the Cayley–Tustin method, discrete regulator regulation equations are established and facilitated for an output regulator design to achieve fluid flow control and manipulation. To address model instability, a spectrum analysis is utilized in stabilizing continuous-time CGLE and KSE systems, and a link between discrete- and continuous-time closed-loop system stabilizing gains is established. Finally, the proposed methodology is demonstrated through a set of simulation cases, by which the output tracking, disturbance rejection, and model stabilization are achieved for the considered CGLE and KSE systems.

A unifying basis for the interplay of stress and chemical processes in the Earth: support from diverse experiments

The interplay between stress and chemical processes is a fundamental aspect of how rocks evolve, relevant for understanding fracturing due to metamorphic volume change, deformation by pressure solution and diffusion creep, and the effects of stress on mineral reactions in crust and mantle. There is no agreed microscale theory for how stress and chemistry interact, so here I review support from eight different types of the experiment for a relationship between stress and chemistry which is specific to individual interfaces: (chemical potential) = (Helmholtz free energy) + (normal stress at interface) × (molar volume). The experiments encompass temperatures from -100 to 1300 degrees C and pressures from 1 bar to 1.8 GPa. The equation applies to boundaries with fluid and to incoherent solid–solid boundaries. It is broadly in accord with experiments that describe the behaviours of free and stressed crystal faces next to solutions, that document flow laws for pressure solution and diffusion creep, that address polymorphic transformations under stress, and that investigate volume changes in solid-state reactions. The accord is not in all cases quantitative, but the equation is still used to assist the explanation. An implication is that the chemical potential varies depending on the interface, so there is no unique driving force for reaction in stressed systems. Instead, the overall evolution will be determined by combinations of reaction pathways and kinetic factors. The equation described here should be a foundation for grain-scale models, which are a prerequisite for predicting larger scale Earth behaviour when stress and chemical processes interact. It is relevant for all depths in the Earth from the uppermost crust (pressure solution in basin compaction, creep on faults), reactive fluid flow systems (serpentinisation), the deeper crust (orogenic metamorphism), the upper mantle (diffusion creep), the transition zone (phase changes in stressed subducting slabs) to the lower mantle and core mantle boundary (diffusion creep).