Corner Flow Research Articles

A Comparative Study on the Prediction of Hydrogen, Nitrogen, and Water Vapor of Regenerative Hydrogen Pump With Different Turbulence Models

Abstract The flow in a regenerative hydrogen pump used in a proton exchange membrane (PEM) fuel cell system is complex, including velocity mixing, streamline distortion, swirling flow, corner flow, and possible boundary separation. Experimental measurement and computational fluid dynamics (CFD) prediction are the main methods used to evaluate such performance. In this work, regenerative hydrogen designed for fuel cell electric vehicles with an impeller diameter of 91 mm and a shaft speed of 22,000 rpm is tested with a mixture of nitrogen, hydrogen, and water vapor. During the test, the flowrate and shaft speed ranges are 151–881 L/min and 8000–22,000 rpm, respectively. The inlet pressure and temperature are 171 kPa and 66 °C, respectively. Then, the flow is predicted by the k − ε model, the renormalization group (RNG) k − ε model, the explicit algebraic Reynolds stress models (EARSM) and the shear-stress transport (SST) detached eddy simulation (DES) model. The differences between the tested and predicted performances are compared. With these results, the velocity distribution in the side channel, the radial force of the impeller and casting, and the changes in the downstream pressure and velocity are analyzed in consideration of the ability of the turbulence models to simulate each characteristic flow. On this basis, the differences and abilities of the turbulence models for predicting the flow in regenerative hydrogen pumps are summarized.

New constraints to subduction zone arc and backarc mantle temperatures: a test of the corner flow model

The heat source for the hot volcanic arc of subduction zones and the uniformly warm backarc is not well understood, particularly where backarc extension is absent. In the widely studied corner flow model, the traction of the underthrusting plate drags down the overlying viscous mantle, and the induced shallower seaward flow brings in heat from the landward and deeper asthenosphere. However, earlier comparisons with observations, especially backarc heat flow, gave poor agreement. There are several new constraints to the temperatures and structures above the underthrusting plate and in the backarc, especially those in western North America, for comparison with model predictions. Seismic receiver functions map horizontal boundaries, including the lithosphere-asthenosphere boundary (LAB). Seismic shear wave tomography gives mantle velocity-depth that provides an approximate proxy for temperature. Attenuation of seismic wave speed indicates high temperature or partial melting. The presence of recent backarc volcanics and their geochemistry give the depth and temperature of the LAB. From these constraints in western North America, the LAB reflects ponding of partial melt, is consistently at a depth of 65±3 km and temperature of 1350±25°C, and overlies nearly constant temperature (adiabatic) asthenosphere across the backarc from Mexico to Alaska. These depth and temperature estimates are greatly different from corner flow model predictions. An alternative hypothesis more consistent with these constraints is vigorous small-scale convection in the backarc asthenosphere. Whether or how this convection coexists with the large-scale flow patterns inferred from the interpretation of seismic anisotropy analyses, and to what degree it prevails in the arc-forearc region, deserve further research.

Pore-scale study of three-dimensional three-phase dynamic behaviors and displacement processes in porous media

Carbon dioxide geological sequestration is a key method to alleviate global warming and enhance oil recovery, where the three-phase displacement processes of oil, water, and carbon dioxide gas in porous media are frequently encountered. In this study, a three-phase three-dimensional lattice Boltzmann method coupled with special wettability and outlet boundary schemes is adopted to simulate the three-phase displacement processes in porous media. The method is validated by the contact angles on a curved surface and droplet flowing through the outlet boundary. With this method, the influences of capillary number, wettability, and local large pores on three-phase flow are investigated. In particular, different dynamic behaviors of fluids are observed at the pore scale, such as bypass-double displacement, stop-wait displacement, burst displacement, snap-off trapping, and corner flow. Further, Euler number and oil saturation are calculated to quantitatively characterize the fluidic morphology and displacement efficiency under different conditions. For all three phases, the Euler number of low capillary number, strong water-wet, and structures with large and medium pores is relatively low, indicating that the morphology of fluids is more connective. For enhancing oil recovery efficiency, high capillary number and strong water-wet structures are beneficial.

The Law of the Total Pressure Loss in Supersonic Streamwise Corner Flow

Abstract The total pressure loss is a critical issue in the design of internal flow channels for hypersonic vehicles. In the flow through the streamwise corner region, the adjacent walls induce secondary flows that exacerbate the viscous effects, thereby intensifying the total pressure loss. This study investigates the impact of the corner’s dihedral angle and the compressibility of the flow on the total pressure loss in the streamwise corner region. The results indicated that as the dihedral angle increases, the distribution of the total pressure contour in the corner region became significantly distorted. The proportion of the boundary layer area within the corner region concurrently increased as the dihedral angle deviates from 90 degrees. Furthermore, we deduce that the total pressure loss is the largest in the supersonic flat plate boundary layer. This paper normalized the total pressure loss coefficient for different dihedral angles in the corner region and established an empirical relationship for the distribution of normalized total pressure loss coefficients along the flow path. It is discovered that under supersonic inflow conditions, the distribution law of the total pressure loss in the corner region exhibits higher predictive accuracy.

Optimization‐based pore network modeling approach for determination of hydraulic conductivity function of granular soils

AbstractA wide range of applications of unsaturated hydraulic conductivity is well known in geotechnical, hydrological, and agricultural engineering fields. The standard prediction models for hydraulic conductivity function overlook the complexity of soil pore structure and employ a simplistic approach based on the bundle of capillary tubes. This study proposes an alternative approach employing pore network models calibrated to match soil water retention data to predict the hysteretic hydraulic conductivity function of granular soils. A novel approach to constructing a multidirectional pore network built on an irregular lattice with variable coordination numbers is presented for the realistic representation of soil voids. The geometric and topological parameters of the pore network model are optimized using the genetic algorithm, and adequate pore‐scale processes (piston‐like advance and corner flow during drainage and piston‐like advance, pore body filling, and snap‐off during imbibition) are modeled to get reasonable predictions of hysteretic hydraulic conductivity functions over the entire suction range of granular soils. Comparisons between the pore network model results, standard physically based models, and measured data for a variety of granular soils show that the proposed pore network has a superior performance over other models and compares favorably to the experimental data.

Data-driven wall modeling for LES involving non-equilibrium boundary layer effects

PurposeWall-modeled large eddy simulation (LES) is a practical tool for solving wall-bounded flows with less computational cost by avoiding the explicit resolution of the near-wall region. However, its use is limited in flows that have high non-equilibrium effects like separation or transition. This study aims to present a novel methodology of using high-fidelity data and machine learning (ML) techniques to capture these non-equilibrium effects.Design/methodology/approachA precursor to this methodology has already been tested in Radhakrishnan et al. (2021) for equilibrium flows using LES of channel flow data. In the current methodology, the high-fidelity data chosen for training includes direct numerical simulation of a double diffuser that has strong non-equilibrium flow regions, and LES of a channel flow. The ultimate purpose of the model is to distinguish between equilibrium and non-equilibrium regions, and to provide the appropriate wall shear stress. The ML system used for this study is gradient-boosted regression trees.FindingsThe authors show that the model can be trained to make accurate predictions for both equilibrium and non-equilibrium boundary layers. In example, the authors find that the model is very effective for corner flows and flows that involve relaminarization, while performing rather ineffectively at recirculation regions.Originality/valueData from relaminarization regions help the model to better understand such phenomenon and to provide an appropriate boundary condition based on that. This motivates the authors to continue the research in this direction by adding more non-equilibrium phenomena to the training data to capture recirculation as well.

Teleseismic measurements of Upper Mantle Shear-Wave Anisotropy in Southern Mexico

The Mexican subduction system is an ideal region to study 3-D mantle deformation patterns in response to changes in slab geometry and the presence of tears. Shear-wave splitting measurements were made using SKS, SKKS, and PKS waves in southern Mexico, where the Cocos slab subducts beneath the North American and western Caribbean plates. For most of southern Mexico, the results are consistent with predominantly trench-normal fast polarization directions that can be interpreted as a consequence of sub-slab entrained flow and 2-D corner flow in the mantle wedge in the presence of A-type olivine fabric (or similar). This pattern of trench-perpendicular fast axes extends northward to the region southeast of the Trans-Mexican Volcanic Belt. Beneath its eastern end, fast axes rotate ∼20° clockwise and are likely controlled by the absolute motion of the North American plate. In southeastern Mexico, along the coast and above the mantle wedge tip, the fast axes are trench-normal and the delay times are the shortest. They were interpreted to result from a possibly serpentinized mantle wedge tip. In the same region above the mantle wedge core, the splitting parameters appear to result from different flow patterns in the mantle wedge and the sub-slab mantle.

Slab steepening and rapid mantle wedge replacement during back-arc rifting in the New Hebrides

The effects of the composition and angle of the subducting slab and mantle wedge flow on tectonic and magmatic processes in island arcs and associated back-arcs are poorly understood. Here we analyse the ages and compositions of submarine lavas from the flanks and the floor of the back-arc Futuna Trough some 50 km east of Tanna Island in the New Hebrides arc front. Whereas >2.5 Ma-old back-arc lavas formed from an enriched mantle source strongly metasomatized by a slab component, the younger lavas show less slab input into a depleted mantle wedge. The input of the slab component decreased over the past 2.5 million years while the enriched mantle was replaced by depleted peridotite. The change of Futuna Trough lava compositions indicates rapid (10 s of km/million years) replacement of the mantle wedge by corner flow and slab steepening due to rollback, causing extensional stress and back-arc rifting in the past 2.5 million years.

Pore-scale investigation of forced imbibition in porous rocks through interface curvature and pore topology analysis

Forced imbibition, the invasion of a wetting fluid into porous rocks, plays an important role in the effective exploitation of hydrocarbon resources and the geological sequestration of carbon dioxide. However, the interface dynamics influenced by complex topology commonly leads to non-wetting fluid trapping. Particularly, the underlying mechanisms under viscously unfavorable conditions remain unclear. This study employs a direct numerical simulation method to simulate forced imbibition through the reconstructed digital rocks of sandstone. The interface dynamics and fluid–fluid interactions are investigated through transient simulations, while the pore topology metrics are introduced to analyze the impact on steady-state residual fluid distribution obtained by a pseudo-transient scheme. The results show that the cooperative pore-filling process promoted by corner flow is dominant at low capillary numbers. This leads to unstable inlet pressure, mass flow, and interface curvature, which correspond to complicated interface dynamics and higher residual fluid saturation. During forced imbibition, the interface curvature gradually increases, with the pore-filling mechanisms involving the cooperation of main terminal meniscus movement and arc menisci filling. Complex topology with small diameter pores may result in the destabilization of interface curvature. The residual fluid saturation is negatively correlated with porosity and pore throat size, and positively correlated with tortuosity and aspect ratio. A large mean coordination number characterizing global connectivity promotes imbibition. However, high connectivity characterized by the standardized Euler number corresponding to small pores is associated with a high probability of non-wetting fluid trapping.

Novel capillary rise enhancement of dual-shape hybrid groove made by laser etch-sputtering

High aspect ratio groove is attractive in varied applications, but is not easy to fabricated in practice. A dual-shape hybrid groove (DSHG), with a novel capillary wicking performance, was simply fabricated using laser etch-sputtering method on aluminum sheet. Except for the high aspect ratio grooves, outer super-hydrophilic grooves covered with micro/nano multi-scale structures were also sputtered by pulsed laser in the simultaneous processing of DSHG. It was found that the combination of high capillary pressure and high permeability of DSHG, as well as the fluid interaction within the dual structure, contributes to improving capillary transport. Consequently, the capillary rise of DSHG reached 200 mm in just 85 s, with an average speed of 24 mm/s within the first 2 s. The rectangle flow defined in the rectangle groove, along with the bulk flow and corner flow in the tapered groove, can establish the capillary dynamics equations for DSHG. The laser etch-sputtering of DSHG presents a promising approach in mass production of liquid capillary devices.

Investigating snap-off behavior during spontaneous imbibition in 3D pore-throat model by pseudopotential lattice Boltzmann method

As a result of complex pore-throat geometry and precursor corner flow, the snap-off of the non-wetting phase occurs during the spontaneous imbibition (SI) of wetting phase. However, accurate modeling of such pore-scale flow behavior remains a big challenge, and its influencing factors remain unclear. In this study, an improved pseudopotential lattice Boltzmann method (LBM) is used to analyze the snap-off behavior during the SI process in three-dimensional (3D) pore-throat models with rough surfaces. The influence of the pore-to-throat size ratio (λ), contact angles (θ), and Ohnesorge number (Oh) on the occurrence of the snap-off are investigated and based on which a 3D phase diagram is established. The snap-off is more likely to occur with the increase in λ and Oh and decrease in θ, respectively. Only when the λ is ≥2 and the θ is <13°, the snap-off may occur. With the increase in θ from 0° to 13°, the snap-off is suppressed due to the relatively small advancing difference between the corner flow and the bulk meniscus. Volume fraction of the entrapped gas bubble in the pore increases with the increase in λ and Oh and the decrease in θ. The time when snap-off occurred increases with the increase in λ and θ, and decrease in Oh. These results are fundamental for investigating snap-off phenomena in real 3D pore space and guide how to avoid or facilitate the occurrence of snap-off and to control the degree of snap-off.

The PDI model system for parameterizing soil hydraulic properties

AbstractThe Peters–Durner–Iden (PDI) model system for describing soil hydraulic properties (SHP) has been developed over a decade. Inspired by Rien van Genuchten's seminal work, the PDI system focuses on an efficient and simple parameterization of water retention curves and hydraulic conductivity curves (HCC) across the entire soil moisture spectrum. By combining capillary and non‐capillary components for water retention and conductivity, it aims to reconcile mathematical simplicity and insights on water adsorption and film flow in soils. Recent developments have reduced the number of free parameters of the conductivity model to zero, enhancing the model's applicability in cases of limited data availability. The first reduction was achieved by a prediction of absolute non‐capillary conductivity based on the consideration of film and corner flow on the pore scale, and the second by a prediction of absolute capillary conductivity by a capillary bundle model. This allows a complete characterization of SHP over the entire moisture range with only four retention curve parameters. The inclusion of a maximum pore size in the capillary conductivity model prevents an unrealistic drop of the HCC near saturation. This paper provides a comprehensive overview of the PDI model system, emphasizing its conceptual features and mathematical details. An Excel sheet and a Python code stored in a repository are provided for accessibility.

Pressure-dependent large-scale seismic anisotropy induced by non-Newtonian mantle flow

SUMMARY Observations of large-scale seismic anisotropy can be used as a marker for past and current deformation in the Earth’s mantle. Nonetheless, global features such as the decrease of the strength of anisotropy between ∼150 and 410 km in the upper mantle and weaker anisotropy observations in the transition zone remain ill-understood. Here, we report a proof of concept method that can help understand anisotropy observations by integrating pressure-dependent microscopic flow properties in mantle minerals particularly olivine and wadsleyite into geodynamic simulations. The model is built against a plate-driven semi-analytical corner flow solution underneath the oceanic plate in a subduction setting spanning down to 660 km depth with a non-Newtonian n = 3 rheology. We then compute the crystallographic preferred orientation (CPO) of olivine aggregates in the upper mantle (UM), and wadsleyite aggregates in the upper transition zone (UTZ) using a viscoplastic self-consistent (VPSC) method, with the lower transition zone (LTZ, below 520 km) assumed isotropic. Finally, we apply a tomographic filter that accounts for finite-frequency seismic data using a fast-Fourier homogenization algorithm, with the aim of providing mantle models comparable with seismic tomography observations. Our results show that anisotropy observations in the UM can be well understood by introducing gradual shifts in strain accommodation mechanism with increasing depths induced by a pressure-dependent plasticity model in olivine, in contrast with simple A-type olivine fabric that fails to reproduce the decrease in anisotropy strength observed in the UM. Across the UTZ, recent mineral physics studies highlight the strong effect of water content on both wadsleyite plastic and elastic properties. Both dry and hydrous wadsleyite models predict reasonably low anisotropy in the UTZ, in agreement with observations, with a slightly better match for the dry wadsleyite models. Our calculations show that, despite the relatively primitive geodynamic setup, models of plate-driven corner flows can be sufficient in explaining first-order observations of mantle seismic anisotropy. This requires, however, incorporating the effect of pressure on mineralogy and mineral plasticity models.

Mantle Flow Induced by the Interplay of Downgoing Slabs Revealed by Seismic Anisotropy Beneath the Sula Block in Eastern Indonesia

AbstractThe North Sulawesi subduction zone is characterized by southward subduction of the Celebes Sea slab to a depth of ∼250 km, mainly overlying the Sangihe slab that subducts west from the Molucca Sea and penetrates the mantle transition zone. The palaeo‐subducted Sula slab dips northward and partially underlies both the Sangihe and Celebes Sea slabs. Adjacent subduction zones with horizontal overlapping subducting slabs in the upper mantle have unclear dynamic interactions. An extensive strike‐slip fault forms the western boundary of the active North Sulawesi subduction zone, providing an ideal setting to study mantle flow between overlapping slabs. We use local S‐wave and teleseismic S and SK(K)S waveform splitting analysis to measure seismic anisotropy in the northern Sulawesi region. Our observations reveal typical mantle wedge corner flow within the Sangihe subduction system. In the Gulf of Tomini, the observed trench‐oblique fast‐axis orientations above the Celebes Sea slab are likely a consequence of the interaction between two subducting slabs. The southernmost measurement with an E–W‐trending fast direction in the mantle wedge might be related to the subduction of the Sula slab. Furthermore, fault‐parallel fast‐axis orientations of anisotropy near the southern segment of the Palu‐Koro fault are attributed to large‐scale shearing across this lithospheric‐scale strike‐slip fault system. Overall, our observations suggest that the strain caused by lithospheric and asthenospheric deformation is mainly confined within the microplate, displaying a restricted flow pattern and localized effects due to the size of the plate boundaries, such as the Palu‐Koro fault.

Two-stage exhumation of high-pressure rocks by corner flow and mud volcanism within an active subduction zone – A case study from serpentinite mud volcanoes along the Mariana convergent margin

During International Ocean Discovery Program (IODP) Expedition 366 cores were recovered from three serpentinite mud volcanoes containing clasts that originate from the subduction-channel along the Philippine Sea Plate – Pacific Plate boundary. The drilled and sampled mud volcanoes (Yinazao, Fantangisña, and Asùt Tesoru) are located at distances of 55 to 72 km from the Mariana Trench. Mafic rock clasts, embedded within a serpentinite mud matrix, from the flanks and summits of both Asùt Tesoru and Fantangisña Seamounts were analyzed for reconstruction of their metamorphic and deformational overprint in order to reveal the tectono-metamorphic conditions at the metamorphic peak within the subduction channel and the subsequent low-grade overprint during exhumation. Several seamounts comprise clasts of lower plate metabasites with different metamorphic overprint (from low-grade sub-greenschist facies to lower blueschist facies). The metabasites are also associated with clasts of fossiliferous carbonates and cherts with different degrees of metamorphic and deformational overprint, that also originated from the Pacific lower Plate. This implies that these rocks were exhumed from different depths within the subduction channel before being regurgitated within a serpentinite mud matrix. The blueschist facies metamorphic rocks, being affected by metamorphic pressures in the range of 11 to 13.8 kbar at minimum, were very likely exhumed from greater depth within the subduction channel before being captured by uprising, localized serpentinite mudflows, indicating evidence that corner flow is actually taking place along the Mariana convergent margin, and that the high-pressure rocks were exhumed by corner flow in an active subduction zone. Final exhumation, however, is related to the embedding of the rocks within a serpentinite mud matrix and the buoyant ascent of serpentinite mudflows along forearc fracture zones extending from the plate boundary to the upper plate sea floor.

Mathematical modeling of mass transfer in CO2 injection for confined fluids at near-miscible condition

Complex interaction between fluid and solid in tight formations leads to capillary confinement and interface slip. Mass transfer between oil and CO2 in CO2 flooding is essential to understand the flow complexity. Therefore, the objective of this work is to propose a comprehensive model to analyze the mass transfer during CO2 injection in the confined fluids. The modified Peng-Robinson equation of state considering the fluid-wall interaction and adsorption was established to calculate the properties of hydrocarbons and CO2. Relative permeability for the near-miscible state was then estimated using the new relative permeability model with corner flow effect. Predicted results agree well with the experimental observations. Afterwards, it was integrated with a one-dimension mathematical model to analyze the physical mechanisms of CO2 flooding in tight reservoirs. Results indicate that nanoconfinement increases the relative permeability at near-miscible condition, and confined fluid is more likely to be miscible than the bulk fluid. Additionally, nanoconfinement can reduce the velocity of CO2 front and increase the breakthrough time of CO2, which is favorable to improve the efficiency of CO2 flooding. This model provides a deep understanding of mass transfer between CO2 and hydrocarbons, and it can be integrated with compositional simulators to solve the field-scale cases including the microscale mechanism of tight reservoirs.

Unsaturated hydraulic property measurements of subtropical anthropogenic (purple) soils in China

AbstractMany anthropogenic soils, often referred to as red bed or purple soils, are distributed in various areas of southern China. Purple soils typically are highly weathered and often lead to natural and engineering hazards because of their relatively poor water retention properties. Knowledge of the unsaturated soil hydraulic properties of purple soils is crucial for their optimal management and various assessment studies. In this work, the hydraulic properties of purple soils from southern China were measured in the laboratory over the full moisture range using a combination of evaporation (HYPROP) and psychrometer (WP4C) approaches. Measured data were analyzed in terms of four different unimodal and bimodal soil hydraulic models. The measurements and analyses showed that bimodality was not overly significant for most samples. The good fit of the Peters–Durner–Iden models furthermore suggested that corner and film flows were important under relative dry conditions. Existing soil pedotransfer functions were found to provide a fairly close match for the slope of water retention curves with the exception of near saturated water contents and the saturated conductivity. To the best of our knowledge, this is the first time that unsaturated hydraulic data of purple soils are provided over the full moisture range.

Inferring the Paleo‐Location of Proto‐Arc Magmas During Subduction Infancy in the Izu‐Bonin‐Mariana

AbstractSubduction zones are one of the principal drivers of the modern‐day plate tectonics, but the processes that develop as incipient subduction zones mature are yet to be understood. Finding modern analogs for different stages of subduction infancy remains an outstanding challenge to answer questions on how and when an oceanic subduction zone reaches a quasi‐steady state to become long‐lived. Here, we compare the southern Mariana intra‐oceanic arc, in which near‐trench spreading and infant arc magmatism developed ∼3–4 Myr ago, with the Izu‐Bonin‐Mariana (IBM) proto‐arc magmas that formed during subduction infancy ∼52 Myr ago. Building upon this comparison, we propose that the Southern Mariana may be considered as a modern analog to subduction infancy. The similarities between the Southern Mariana arc magmas and the IBM Eocene proto‐arc magmas suggest that the IBM proto‐arc crust might have formed within 80–90 km from the paleo‐trench (slab at &lt; 90 km paleo‐depth), while the Eocene infant arc was likely located at ∼100 km from the paleo‐trench (∼100–125 km slab paleo‐depth). We use our constraints further to propose a new conceptual model of subduction evolution for IBM. In this model, development of the subduction channel during arc infancy facilitated downward slab penetration and intensified corner flow in the sub‐arc asthenosphere of the mantle wedge. As such, cooling and serpentinization of the fore‐arc mantle might be considered as the principal drivers of subduction maturation and stabilization over the IBM lifetime.

Pore-scale simulation of low-salinity waterflooding in mixed-wet systems: effect of corner flow, surface heterogeneity and kinetics of wettability alteration

The initial wettability state of the candidate oil reservoirs for low-salinity waterflooding (LSWF) is commonly characterized as mixed-wet. In mixed-wet systems, both the two-phase flow dynamics and the salt transport are significantly influenced by the corner flow of the wetting phase. Thus this study aims at comprehensive evaluation of LSWF efficiency by capturing the effect of corner flow and non-uniform wettability distribution. In this regard, direct numerical simulations under capillary-dominated flow regime were performed using the OpenFOAM Computational Fluid Dynamics toolbox. The results indicate that corner flow results in the transport of low-salinity water ahead of the primary fluid front and triggers a transition in the flow regime from a piston-like to multi-directional displacement. This then makes a substantial difference of 22% in the ultimate oil recovery factors between the 2D and quasi-3D models. Furthermore, the interplay of solute transport through corners and wettability alteration kinetics can lead to a new oil trapping mechanism, not reported in the literature, that diminishes LSWF efficiency. While the findings of this study elucidate that LSWF does exhibit improved oil recovery compared to high-salinity waterflooding, the complicating phenomena in mixed-wet systems can significantly affect the efficiency of this method and make it less successful.

Stagnation enthalpy effects on hypersonic turbulent compression corner flow at moderate Reynolds numbers

Stagnation enthalpy effects on hypersonic turbulent compression corner flow at moderate Reynolds numbers