Reactive Fluid Flow Research Articles

Antigorite dehydration fluids boost carbonate mobilisation and crustal CO2 outgassing in collisional orogens

The processes of carbon mobilisation at convergent plate boundaries are hotly debated. Recent findings suggest that carbon release along subduction geothermal gradients may well be more relevant than previously thought; however, it has remained difficult to achieve steady state atmospheric CO2 conditions over geological time scales based on current volatile cycle models. Here, we report on meta-ophicarbonate rocks in the contact metamorphic aureole of the Bergell intrusion, Val Malenco, European Alps, that reached T-P conditions of at least 650 °C at 0.35 GPa. We demonstrate by combined field evidence, geochemistry, and closed-system thermodynamic modelling that over 50% of the rock carbonate has been mobilised locally in response to reactive fluid flow upon progressive isobaric heating from 350 to >650 °C. Despite complete mineral transformation at the antigorite + calcite devolatilisation reaction, the resulting tremolite-ophicarbonate preserves the original ophicarbonate texture by olivine-chlorite clasts, representing the former antigorite-serpentinite fraction, embedded in a monomineralic tremolite matrix formed from the calcite fraction that often exceeded 50 vol%. Closed system thermodynamic modelling based on an ophicarbonate composition of 80 wt% serpentinite +20 wt% calcite reveals that rock-buffered fluid XCO2 values evolve from <0.09 to as high as ∼0.16, and the total H2O-CO2 fluid fraction released may be as high as 14 wt%; values that are highly sensitive to bulk ophicarbonate composition.Major to trace element geochemistry reveals a history of peridotite melt depletion followed by ocean floor hydration and ophicarbonate formation, consistent with the ocean continent transition (OCT) setting of the mantle rocks in the Mesozoic. This is demonstrated by positive anomalies in B, U, As, Sb, Bi, and W, and by bulk rock and notably carbonate primitive mantle normalised REE patterns that are basically identical to that of calcite precipitated from Jurassic seawater except for its negative Eu anomaly. Prograde metamorphic tremolite and diopside possess enrichments notably in Sr and REE inherited from reactant calcite, as is also supported by a good match between measured and modelled silicate mineral compositions. Specific geochemical characteristics of the prograde meta-ophicarbonate rocks imply fluid mediated, open system processes. Antigorite dehydration fluid ingress, likely produced in neighbouring antigorite-serpentinites, may have shifted bulk tremolite ophicarbonate rock compositions towards higher SiO2/MgO ratios along with an increase in B contents and depletion in fluid mobile elements such as As, Sb, and Sr.The massive, contact metamorphic CO2 mobilisation documented here occurred at P-T conditions that are similar to those that can be achieved in collisional orogenic settings, whose clockwise P-T-t paths are often characterised by further heating upon initial decompression. They thus evolve at large angle to devolatilisation reactions and silicate-carbonate rock-buffered fluid XCO2 isopleths, thus fostering carbon mobilisation towards metamorphic peak temperatures at moderate to low pressures (in the region of between >700 °C – 1.0 GPa and >600 °C – 0.3 GPa). Barrovian metamorphism, too, can reach T-P conditions of 800 °C – 1 GPa. Amagmatic CO2 mobilised this way will eventually reach the atmosphere via dispersion in the groundwater table and diffuse outgassing. Despite the huge uncertainties associated with quantification of such metamorphic carbon fluxes, geological time scale global carbon cycling models should more rigorously explore the significance of these contributions.

Chemically reacting magneto-hydrodynamics (MHD) fluid flow through a porous medium

This paper considered and investigated the effects of chemically reacting Fluid flow through a porous medium in a Magnetic field as a magneto-hydrodynamics fluid flow through a porous medium. We developed a mathematical model for the flow and using perturbation method, the modeled partial differential equations were reduced to a system of ordinary differential equations and solved. The geometry of the problem was considered where the x-axis is taken in the vertical direction along the plate while y-axis is normal to the plate so that all the characteristics of the fluid are independent of the variable x. The impact of Chemical reaction, Magnetic intensity, Prandt number, schmidt number, porosity and thus permeability of the physical parameters were investigated on velocity, temperature, and concentration profiles. More so, the impacts of the same parameters were investigated on the skin-friction, Nuselt number, and Sherwood number. The results showed that growing magnetic intensity leads to decrease in velocity and skin-friction of the flow field at every point, increase in chemical reaction and Schmidt number leads to decrease in temperature and concentration at every point of the flow field. An increase in Prandtl number, Magnetic intensity, and Permeability shows no effect on concentration profile at every point of the flow field.

Author Correction: Instantaneous rock transformations in the deep crust driven by reactive fluid flow

Author Correction: Instantaneous rock transformations in the deep crust driven by reactive fluid flow

Transient Heat and Mass Transfer of Hydromagnetic Effects on the Flow Past a Porous Medium with Movable Vertical Permeablesheet

An unsteady flow of heat and species transport through a porous medium in an infinite movable vertical permeable flat surface is considered. The hydromagnetic chemical reactive fluid flow is stimulated by the thermal and solutant convection, and propelled by the movement of the surface. The formulated nonlinear flow equations in time space are solved analytically by asymptotic expansions to obtain solutions for the flow momentum, energy and chemical concentration for various thermo-physical parameters. The existence of flow characteristic is defined with the assistance of the flow parameters. In the study, the impact of some pertinent flow terms is reported and discussed. The study revealed that the species boundary layer increases with a generative chemical reaction and decreases with a destructive chemical reaction. Also, arise in the generative species reaction term reduces the flow momentum for the cooling surface. The impact of other flow governing parameters is displayed graphically as well as the fluid wall friction, wall energy and species gradients. The results of this study are important in chemical thermal engineering for monitoring processes to avoid solution blow up.

Formation of Mg-carbonates and Mg-hydroxides via calcite replacement controlled by fluid pressure

Reactive fluid flow can control the mineralogical, mechanical and chemical evolution of the Earth’s crust. When rocks are exposed to differential stresses (i.e., vertical stress ≠ horizontal stress ≠ pore-fluid pressure (Pf)) during reactive fluid flow, effective pressure is usually assumed to control the overall reaction process. Here, we show that fluid pressure can play an important role in mineral replacement reactions. We conducted experiments in which calcite (CaCO3) grains (fraction size 53–150 µm) reacted with a Mg-rich solution at ~ 200 °C both in a closed system and under reactive fluid flow conditions with different fluid flow rates and fluid pore pressures, but with similar confining pressure (σn = 10 or 20 MPa) and effective pressure (Pe). Under closed system, vapor-saturated pressures, the magnesite formed with large pores between the magnesite and the calcite. In the open system flow-through experiments, however, brucite (Mg(OH)2) or magnesite (MgCO3) formed, depending on pore-fluid pressure. The main reaction product was brucite at low pore-fluid pressure (0.2 MPa), but magnesite at higher pore-fluid pressures (≥ 1 MPa). Calcite dissolution and precipitation of the product mineral increased concomitantly with flow rate, but the flow rate did not affect the nature of the products. The permeability of the reacting rock was related to the reaction pathway, i.e. the nature of the products. Magnesite replaced the pristine calcite in a pseudomorphic manner, and mantled the pristine calcite with 10–100 µm wide pores. In contrast, tabular and/or platy brucite blocked the porosity and resulted in a decrease in permeability. Our results show that the pore-fluid pressure can be a significant parameter controlling the reaction products and reaction processes in volatile-rich (e.g., CO2, HCl, H2S and SO2) systems at conditions close to phase separation; these conditions occur for example in epithermal and porphyry hydrothermal systems, and in carbonate-replacement and some metamorphic environments.

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).

On Criticality for a Generalized Couette Flow of a Branch-Chain Thermal Reactive Third-Grade Fluid with Reynold’s Viscosity Model

This research considers the third-grade liquid flow and criticality branched-chain of a thermal reaction in a Couette generalized medium with a nonlinear viscosity model. A dimensionless transformation of the system momentum and heat equations are carried out. Compared with the diffusion coefficient, the flow is stimulated by initiation reaction rate, reaction branch-chain order, non-Newtonian term, thermal Grashof number, and pressure gradient. The reactive fluid is fully exothermic with consumption of the material, and the heat exchange in the system is greater than the exchange of heat with the ambient. A semianalytical collocation weighted residual scheme is employed for the branch-chain slice bifurcation, dimensionless energy, and momentum solutions. The results show that exponential decreases in the thermal fluid viscosity can help in controlling the boundless heat produced by the Frank-Kamenetskii term and initiation reaction rate. Therefore, the results will help in stimulating positive combustion processes.

Magnetohydrodynamic nonlinear mixed convection flow of reactive tangent hyperbolic nano fluid passing a nonlinear stretchable surface

The intent of this paper is to unravel the transport of a nonlinear mixed convection tangent hyperbolic nanofluid along a nonlinear stretchable sheet in the neighbourhood of a stagnation point. The impacts of magnetohydrodynamic, thermophoresis, Brownian motion and activation energy together with non-uniform heat source associated with varying thermal conductivity are scrutinized. The outlining transport equations are mutated into a system of nondimensional ordinary differential equations by the use of similarity transformations and then tackled with the Runge–Kutta Fehlberg coupling shooting method. The impact of all essential parameters in respect of the dimensionless quantities are graphically exhibited and deliberated. The significant consequences of the investigation are that increment in the Darcy with magnetic term declines the flow velocity while that uplift the fluid temperature. The skin friction factor triggers a considerable increase with the power-law exponent and magnetic field parameters. The intensity of heat and mass transfer shrink with hike in the values of the thermophoresis parameter. The vetting of the numerical solution is done with earlier related studies in the limiting position and presented in tabular form showing perfect correlation.

Heat and mass transfer of a nonlinear convective Arrhenius reactive fluid flow between two vertical plates filled with a porous material

This article studied concentration and thermal effects on a steady flow of a Magnetohydrodynamics reactive fluid driven by both pressure and temperature gradients through a porous medium. The fluid is assumed to undergo exothermic chemical reaction within the channel. The dimensionless coupled nonlinear ordinary differential governing equations of the problem are derived and solved using optimal homotopy analysis method (OHAM). The validation of OHAM’s results is done by carrying out the comparison of this result with those obtained using Chebyshev collocation method and a good agreement is found. The influences of controlling parameters on the fluid velocity, temperature, concentration and heat transfer rate are analyzed using graph and quantitatively discussed. It is observed from the computational results that an increase in nonlinear convective parameters significantly enhances both the velocity and temperature profiles, while it reduces the concentration profile. The usefulness of this study can be found in crude-oil refineries.

Coupled hydro-chemo-mechanical model for fault activation under reactive fluid injection

Pre-existing faults cross-cutting caprock formations constitute potential leakage pathways during geological CO2 sequestration. When the fault filling material is calcite-rich, dissolution of the fault minerals is expected to occur causing the mechanical weakening of the fault or, even worse, its reactivation. In turn, these chemical-mechanical processes influence the distribution of pore pressure in the vicinity of the fault. Hence, a fully coupled approach including the chemically-induced alteration is necessary while investigating fault’s mechanical stability. In this paper, we present a simplified set of equations that allows the resolution of the coupled hydro-chemo-mechanical problem of reactive fluid flow inside a fault. Empirical relationships are used to describe the change of the fault’s material mechanical properties with porosity. The derived model was used to simulate the evolution of the hydro-chemo-mechanical behavior of a fault following an expected leakage scenario during CO2 storage in the Dogger formation in the Paris Basin. The simulation results showed that under normal conditions, fault reactivation is unlikely to happen even in the long term (∼100 years). Nevertheless, the proposed model is capable of capturing the evolution of fault reactivation and has the potential to become a useful element of the toolbox for assessing the risks related to fault reactivation and leakage for CO2 storage projects.

Radiation and Mixed Convection Effects on Chemically Reactive Sisko Fluid Flow over a Curved Stretching Surface

The main objective of this framework is to establish the modeling and simulation of mixed convection flows along with a curved stretching sheet with Sisko fluid. The impacts of thermal radiation and first-order chemical reaction are also incorporated to illustrate the heat and mass transfer phenomenon. In addition, the convective condition is deliberated to discuss the heat transfer mechanism. The normalized conservation equations emerge as a system of non-linear two-dimensional coupled Partial Differential Equations (PDEs). Under appropriate transformation, these equations are converted into Ordinary Differential Equations (ODEs). Numerical procedures are examined in this study for various active parameters. A significant declining behavior of the velocity profile is depicted with an increase in mixed convection and buoyancy ratio parameter. An enhancement conduct in the temperature of the fluid is reported through the growing values of radiation parameter and Biot number. A remarkable decreasing trend is addressed by the higher values of the chemical reaction parameter while plotting the concentration profile of the fluid. Moreover, the resistive forces, heat, and mass transfer rates are discussed in tabular form. A comparison with shooting and RK-45 Fehlberg method is illustrated to show the validity of the present scheme. Thus the present consequences are well correlated with the existing literature.

Experimental Investigation of Natural Fracture Stiffness and Flow Properties in a Faulted CO2Bypass System (Utah, USA)

AbstractFracture stiffness and flow properties have been measured in the laboratory using naturally fractured fault rock samples from the Little Grand Wash fault, Utah, USA. We compare fracture closure and related flow change during isotropic loading of two fractures which have been subject to various amounts of paleoreactive flow. The two tested fractures are described as (i) a small‐aperture fracture (0.1 mm) with negligible geochemical alterations of the fracture surface and (ii) a large‐aperture fracture (0.53 mm) where precipitates are observed on the fracture surface. X‐ray imaging is used for quantification of fracture aperture and fracture surface contact distribution. The petrographical characterization using scanning electron microscopy and X‐ray powder diffraction is performed pretest and describes burial and uplift diagenesis as well as pulses of reactive fluid flow within the fault. The stress‐dependent flow and deformation experiment provides new data on fracture stiffness and flow for naturally developed fractures in siliciclastic rock. Fracture stiffness is found to be highest for the small‐aperture fracture due to its high‐fracture contact ratio and well‐developed surface mating during closure. For the naturally altered and rougher, large‐aperture fracture, fracture stiffness is lower and a highly stress dependent decay in flow is observed during initial closure. The results illustrate that a natural fracture with high contact ratio and well‐mated surfaces will close during loading, whereas a fracture associated with high flow rates and affected by previous geochemical alteration maintains a high flow rate compared to the host rock during similar loading.

Techniques for improving monotonicity in a fourth-order finite-volume algorithm solving shocks and detonations

Techniques are proposed to reduce numerical oscillations in a fourth-order, finite-volume algorithm for solving thermally-perfect, reacting fluid flows with strong discontinuities, such as shock or detonation waves. These additional mechanisms have proven necessary for multispecies flows solved at fourth-order accuracy, and contribute towards bounding the variation of the solution in the vicinity of strong discontinuities. There, oscillations can form due to strong gradients in the flow and may be further intensified by numerical procedures introduced to treat the thermally-perfect thermodynamic system and physical constraints on species mass fractions. The new techniques are designed to respect the conservative property of the base algorithm, retain fourth-order accuracy of the solution in regions of smooth flow, and cooperate with the high-order piecewise parabolic method limiter. Extensive numerical tests, ranging from multispecies mixing flows to reacting flows with detonations, are performed to verify that the new techniques meet the design criteria while effectively suppressing oscillations. The proposed techniques are applied to solve the Shu-Osher and double Mach reflection problems and a set of oblique detonation wave problems. The results demonstrate the effectiveness and robustness of the algorithm.

Instantaneous rock transformations in the deep crust driven by reactive fluid flow

Fluid–rock interactions are a fundamental component of geodynamic processes. They link mass and energy transfer with large-scale tectonic deformation and drive mineral deposit formation, carbon sequestration and rheological changes of the lithosphere. Spatial evidence indicates that fluid–rock interactions operate on length scales that range from the grain boundary to tectonic plates, but the timescales of regional fluid–rock interactions remain essentially unconstrained. Here we present observations from an exceptionally well-exposed fossil hydrothermal system from an ophiolite sequence in northern Norway that we use to inform a multielement advection–diffusion–reaction transport model. We calculated the velocity of the fluid-driven reaction fronts and found that they can propagate at up to 10 cm per year, equivalent to the fastest tectonic plate motion and mid-ocean-ridge spreading rates. Propagation through the low-permeability rocks of the mid-crust is facilitated by a transient, reaction-induced permeability increase. We conclude that large-scale fluid-mediated rock transformations in continental collision and subduction zones occur on timescales of tens of years when reactive fluids are present. We infer that natural carbon sequestration, ore deposit formation and transient and long-term petrophysical changes of the crust proceed instantaneously, from a geological perspective. Fluid-mediated reaction fronts in rocks can propagate up to 10 centimetres per year, according to a transport model informed by observations of an ophiolite in Norway.

Thermal aspects of chemically reactive Oldroyd-B fluid flow over a rotating disk with Cattaneo–Christov heat flux theory

The current study explores the magnetized flow of an Oldroyd-B fluid by a rotating disk. In this analysis, we use the modified Fourier’s law instead of classical Fourier’s law to study the fluid thermal features. The impact of homogeneous–heterogeneous reactions for mass transport is also considered. The von Karman variables are used to convert the partial differential equations into non-dimensional ordinary differential equations. The BVP Midrich scheme is utilized to acquire the numerical solution. Diverse effects of various involved parameters on the velocities, temperature and concentration of the liquid are analyzed. Additionally, the comparison table is made for limiting case to see the validity of our numerical results with the past outcomes. It is observed that the fluid velocity reduces with the impact of relaxation time parameter. Further, higher values of thermal relaxation time decline the fluid temperature. Moreover, with an increase in homogenous reaction, the concentration boundary layer thickness becomes thinner. The reduction in wall concentration gradient is noticed against homogeneous reaction rate.

Thermal analysis for radiative flow of magnetized Maxwell fluid over a vertically moving rotating disk

In the current framework, we study the chemically reactive Maxwell fluid flow over a vertically moving upward/downward rotating disk during the unsteady motion in the presence of magnetic flux. The problem formulation is made in a manner that governing equations of the physical phenomenon ultimately reduce to classical von Karman viscous pumping problem in the absence of vertical motion. Additionally, the aspects of chemical reaction and nonlinear radiations on heat and mass transfer analysis are studied. For the analysis, we use the similarity transformations that convert the governing system of partial differential equations into ordinary ones. The solution of the transformed system is obtained numerically using bvp4c in MATLAB. The numerical outcomes are demonstrated through graphical and tabular depictions. The results of velocity, temperature and concentration fields are discussed in the presence of upward/downward motion of the disk, magnetic parameter, Deborah number, Schmidt number and chemical reaction parameter. Significant outcomes reveal that the impact of disk upward motion parameter boosts the radial and angular flows. It is further noted that the heat transfer rate grows considerably with the disk rotation and radiation parameters. Moreover, Schmidt and chemical reaction parameters play a vital role in enhancing the Sherwood number.

Reactive fluid flow topology optimization with the multi-relaxation time lattice Boltzmann method and a level-set function

This paper presents a topology optimization algorithm based on the lattice Boltzmann method coupled with a level-set method for increasing the efficiency of reactive fluid flows. The multi-relaxation time model is considered for the lattice Boltzmann collision operator, allowing higher Reynolds numbers flow simulations compared to the ordinary single-relaxation time model. The cost function gradient is obtained with the derivation of the adjoint-state formulation for the fully coupled problem. The proposed method is tested successfully on several numerical applications involving Reynolds numbers from 10 up to 1,000, as well as with different Damkohler and Peclet numbers. A limitation of the maximal pressure drop is also applied. The obtained results demonstrate that the proposed numerical method is robust and efficient for solving topology optimization problems of reactive fluid flows, in different operating conditions.

Analysis of Transient Rivlin-Ericksen Fluid and Irreversibility of Exothermic Reactive Hydromagnetic Variable Viscosity

This study analyzes the unsteady Rivlin-Ericksen fluid and irreversibility of exponentially temperature dependent variable viscosity of hydromagnetic two-step exothermic chemical reactive flow along the channel axis with walls convective cooling. The non-Newtonian Hele-Shaw flow of Rivlin-Erickson fluid is driven by bimolecular chemical kinetic and unvarying pressure gradient. The reactive fluid is induced by periodic changes in magnetic field and time. The Newtons law of cooling is satisfied by the constant heat coolant convection exchange at the wall surfaces with the neighboring regime. The dimensionless non-Newtonian reactive fluid equations are numerically solved using a convergent and consistence semi-implicit finite difference technique which are confirmed stable. The response of the reactive fluid flow to variational increase in the values of some entrenched fluid parameters in the momentum and energy balance equations are obtained. A satisfying equations for the ratio of irreversibility, entropy generation and Bejan number are solved with the results presented graphically and discussed quantitatively. From the study, it was obtained that the thermal criticality conditions with the right combination of thermo-fluid parameters, the thermal runaway can be prevented. Also, the entropy generation can minimize at low dissipation rate and viscosity.

Thermal management of methanol reforming reactors for the portable production of hydrogen

Three-dimensional numerical simulations were performed to address the thermal management issues associated with the design of a methanol reforming microchannel reactor for the portable production of hydrogen. The design of the reactor was fundamentally related to the direct coupling of reforming and combustion reactions by performing them on opposite sides of dividing walls in a parallel flow configuration. Effective autothermal operation was achieved through a combination of microchannel reactor technology with heat exchange in a direction perpendicular to the reacting fluid flow. Computational fluid dynamics simulations and thermodynamic analysis were carried out to investigate the effect of various design parameters on the characteristics of the generation, consumption, and exchange of thermal energy within the system. The results indicated that the ability to control temperature and temperature uniformity is of great importance to the performance of the system. The degree of temperature uniformity favorably affects the autothermal operation of the reactor. Temperature uniformity of the reactor can be improved by controlling the rate of heat transfer through a variety of factors such as wall thermal conductivity, fluid velocities, and dimensions. High wall thermal conductivity would be greatly beneficial to the performance of the system and the temperature uniformity of the reactor.

Devolatilization of Subducting Slabs, Part I: Thermodynamic Parameterization and Open System Effects

AbstractThe amount of H2O and CO2 that is carried into deep mantle by subduction beyond subarc depths is of fundamental importance to the deep volatile cycle but remains debated. Given the large uncertainties surrounding the spatio‐temporal pattern of fluid flow and the equilibrium state within subducting slabs, a model of H2O and CO2 transport in slabs should be balanced between model simplicity and capability. We construct such a model in a two‐part contribution. In this Part I of our contribution, thermodynamic parameterization is performed for the devolatilization of representative subducting materials—sediments, basalts, gabbros, peridotites. The parameterization avoids reproducing the details of specific devolatilization reactions, but instead captures the overall behaviors of coupled (de)hydration and (de)carbonation. Two general, leading‐order features of devolatilization are captured: (1) the released volatiles are H2O‐rich near the onset of devolatilization; (2) increase of the ratio of bulk CO2 over H2O inhibits overall devolatilization and thus lessens decarbonation. These two features play an important role in simulation of volatile fractionation and infiltration in thermodynamically open systems. When constructing the reactive fluid flow model of slab H2O and CO2 transport in the companion paper Part II, this parameterization can be incorporated to efficiently account for the open‐system effects of H2O and CO2 transport.