Fluid Mixing Research Articles

Numerical Investigation of Increasing-Decreasing Stepped Micro Pin Fin Heat Sink Having Various Arrangements

The ongoing trend of miniaturization of electronic devices, including computer processors, high-speed servers and micro-electro-mechanical system devices, should go hand in hand with their improved performance. However, managing heat remains a major challenge for these devices. In the present study, a numerical investigation was done on a micro-channel heat sink with an open-stepped micro-pin fin heat sink with various arrangements through ANSYS software. Pin fin was varied in a fashion of increasing and decreasing. The working fluid opted for was water in a single phase. The analysis takes into account varying thermo-physical properties of water. The operating parameters, i.e. the Reynolds number was taken as 100–350 and heat flux as 500 kW/m2. Arrangements selected were staggered and inline. Observations revealed that the staggered 2 arrangement has shown better thermal performance than other arrangements within the entire investigated range of Reynolds numbers because of the effective mixing of fluids. Furthermore, the inline configuration of micro pin fin heat sink has the worst performance. It is interesting to note that a very small difference was observed in the heat transfer capability of both staggered configurations, while the pressure drop in the staggered 2 arrangement has shown an elevated value at a higher Reynold number value compared to the staggered 1 arrangement.

A numerical investigation on rheological turbulent flow through a 90° mixing elbow

Mixing elbows are widely used in various industrial processes to mix two different Newtonian or non-Newtonian fluids under turbulent flow conditions. This study numerically investigates the fluid flow and mixing characteristics in 90-degree elbows with different bend curvatures (curvature ratios of 3, 6, and 9) and Reynolds numbers ranging from 1 × 104 to 5 × 105 for both fluid types. The Reynolds-Averaged Navier–Stokes equations are solved using the turbulent k-epsilon model in ANSYS Fluent. Results show that the bend curvature creates an adverse pressure gradient that drives secondary flows, which become more pronounced with higher Reynolds numbers and lower curvature ratios. Higher Reynolds numbers improve mixing quality, as indicated by velocity and temperature variations quantified using standard deviations. For Reynolds numbers in the range of 104, velocity fluctuations initially increase, but at higher values (~ 105), they decrease, even by up to 64% as the Reynolds number rises from 1 × 105 to 5 × 105. Similarly, increasing the curvature ratio enhances mixing efficiency, with a 32% reduction in velocity fluctuations when the curvature ratio increases from 6 to 9. Furthermore, shear-thinning fluids (n=0.6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$n = 0.6$$\\end{document}) exhibit superior mixing performance, with a standard deviation of velocity fluctuations at the outlet of 0.32, compared to 0.54 for shear-thickening fluids (n=1.4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$n = 1.4$$\\end{document}). In terms of temperature fluctuations also, a similar trend is observed. These findings are valuable for optimizing mixing and fluid transport in industries such as chemical processing and food production, where effective mixing of complex fluids is critical. This study provides insights for improving the design of mixing systems that handle fluids with various rheological characteristics.

Improvement of mixing performance in laminar micromixers utilizing vortex-induced vibration of two circular cylinders

Micromixers have found extensive applications in various fields such as engineering, biomedicine, medical and chemistry. The utilization of vortex-induced vibration (VIV) of bluff bodies can greatly enhance fluid mixing in micromixers. This study focuses on numerically investigating the interaction between vortex-induced vibration of two cylinders, labeled Cyl-S (stationary cylinder) and Cyl-V (vibrating cylinder), and the mixing performance of micromixers. Specifically, the study examines the effects of spacing ratio (S/D) and vibration system configurations (Cyls-S+S, Cyls-S+V, and Cyls-V+V) on vibration response, near-wake structure, mixing concentration, and mixing index. The results indicate that the spacing ratio directly influences the vibration response of the cylinders, thereby significantly impacting the mixing performance. For the Cyls-V+V configuration, the downstream cylinder exhibits a considerably higher vibration amplitude compared to the upstream cylinder. Increasing the S/D ratio substantially improves the mixing effect in the Cyls-S+S configuration. For the Cyls-S+V and Cyls-V+V configurations, the enhancement of mixing due to VIV is particularly noticeable when S/D ratios of 2 and 3 are employed. The mixing index for Cyls-V+V is higher than that for Cyls-S+V within the range of 3 ≤ U⁎ ≤ 5 (where U* represents the reduced velocity). At a reduced velocity of U⁎ = 4 for Cyls-V+V, the optimal mixing indexs are found to be 0.77 (S/D = 2), 0.76 (S/D = 3), 0.78 (S/D = 4), and 0.77 (S/D = 5), respectively. However, when U⁎ = 6–10, the mixing index decreases due to the vibration of the cylinder is suppressed. Additionally, the Cyls-V+V configuration exhibits a significantly higher pressure drop within the flow channel compared to the Cyls-S+V configuration.

Dynamic modeling of air–metal plasma mixture of single-turn coil with erosion at megaGauss magnetic field

Single-turn coil (STC) is a destructive pulsed magnet aiming at 100–300 T magnetic field. Due to the high discharge current, the conductor of STC is heated rapidly and undergoes melting and vaporization, leading to the generation of supersonic air–metal vapor mixed plasma jet and the magneto-fluid effect. In this study, the mixed plasma mass-transfer and fluid dynamic characteristics are modeled at megaGauss magnetic field, high temperature, high pressure, and supersonic conductor shock deformation. The collision integral method is employed to calculate the fluid transport properties. In addition, a boundary constraint model of fluid–structure interaction (FSI) compatible with both fluid wall boundary condition and plasma jet entrance condition and a model to simultaneously solve the thermal ionization and high electric field ionization of the mixed vapor are proposed. As the result, the distributions of plasma electrical conductivity, current density, electron, heavy particles, temperature, air body load, and velocity are derived. Especially, the region of highest electrical conductivity is not the air domain near the inner surface of the conductor with the highest electron density and the highest magnetic field, but the air domain near the outer surface of the conductor with the relatively higher electron density and lower magnetic field.

Fluid inclusion LA-ICP-MS constraint on hydrothermal evolution of proximal cassiterite-bearing quartz veins in the giant Gejiu orefield: Implications for controls on metallogenic potential of granite-related skarn system

Sn and Cu are proposed to have their mineralization potential predetermined by their contents in initial fluids of granite-related magmatic-hydrothermal systems. However, it remains ambiguous whether the giant Sn-mineralized skarn system is applicable, and whether the Sn-Cu association in some deposits is predominantly determined by their initial metal contents. The Gejiu orefield is one of the most essential Sn-polymetallic districts worldwide, with proven resources of 3.27 million tons of tin, 3.25 million tons of copper, 4.29 million tons of lead and zinc, and >20 other metals with economic significance. Sn-polymetallic mineralization at Gejiu constitutes a composite skarn ore system that includes proximal skarn and related cassiterite-sulfide, greisen, and tourmaline-vein types. The Laochang Sn-polymetallic deposit hosts several largest skarn and cassiterite-sulfide orebodies in the eastern part of Gejiu. Recent exploitation at Laochang discovered Sn-mineralized quartz veins hosted in the concealed granite, providing a valuable opportunity to characterize the proximal magmatic-hydrothermal process of the mineralizing granitic system. Here, fluid inclusion analysis is carried out on these veins to discuss the fluid evolution, cassiterite precipitation mechanism and whether metal content in early proximal magmatic fluids determines the metal association and endowment in the deposit.Based on the paragenesis of ore and gangue minerals, three hydrothermal stages are distinguished, including quartz-tourmaline stage (Stage I), cassiterite-arsenopyrite-quartz stage (Stage II) and late sulfide stage (Stage III). Fluid evolution controlling vein formation is constrained by microthermometry and LA-ICP-MS analysis of four fluid inclusions generations successively entrapped in quartz and cassiterite. The fluids involved during vein formation show an interplay between single-sourced magmatic fluids and meteoric water. The intermediate-density single phase fluid recorded at stage I quartz is derived from initial fluids directly exsolving from granitic magma. At stage II, fluid immiscibility occurred and the separated brines were entrapped in quartz and early-formed cassiterite. Along with cassiterite precipitation, brines were mixed with low-salinity and cooler meteoric water, leading to entrapment of low-salinity aqueous fluid in outer growth zones of cassiterite at stage II. The constructed fluid evolution history suggests that fluid immiscibility may have facilitated the nucleation of cassiterite crystals at the onset of deposition while mixing of magmatic fluid with meteoric water likely dominate later cassiterite mineralization.Compared with the fluid dataset of barren and mineralized granitic systems worldwide, pre-ore fluids of the studied quartz veins are enriched in Sn, confirming that high Sn content in the initial magmatic fluid can serve as indicator to distinguish mineralized system. In contrast, although Cu mineralization is economically important in the Laochang deposit, predicted Cu contents in pre-ore proximal magmatic fluids are as low as those obtained from Cu-barren system. This implies introduction of Cu into the hydrothermal system from other sources.

Thermal characteristics of a double-tube heat exchanger with different twist directions of the inner oval tube

A new configuration featuring an inner oval tube with alternating twist directions is proposed to improve the thermal performance of double-tube heat exchangers. This design enhances the heat transfer efficiency by inducing longitudinal vortices within the annular space, thereby disrupting the boundary layer on the heat transfer surface, promoting fluid mixing, and significantly augmenting heat transfer. Numerical simulations were conducted to investigate the effects of alternating twist directions of the inner oval tube on thermal performance. The results demonstrate that alternating twist direction of the inner tube creates more pronounced vortices, significantly enhances heat transfer performance compared with the conventional tubes. This novel oval tube led to a substantial enhancement of up to 173.6 % in the Nu, with a corresponding increase of 96.4 % in the f. At Re = 2600, the highest thermal performance factor of the reported annular tube with an alternately twisted oval inner tube can reach up to 2.18, indicating a 118 % improvement in overall heat transfer performance. Fitted correlations for Nu and f are provided to facilitate engineering applications.

Application of Phytoremediation to Hydraulic Binders Alkaline Inclusion in Forest Roads Pavement Construction

The use of hydraulic binder materials for the improvement of pavement subgrade has many implications for the surrounding ecosystem due to the possible leakage of alkaline compounds. The objective of this study is to evaluate the capacity of plants to remedy the subgrade affected by alkaline inclusion. To reduce the impact and return the subgrade to its original state, a phytoremediation process is studied. The impact of two materials commonly used for the subgrade improvement is analysed – fluid ash (slag) and lime+cement mixture. Three different mixes of plants – Mix A, Mix B and the native natural vegetation Mix N – are proposed. Totally 99 samples were collected and 990 specimens were chemically and geotechnically analysed and statistically evaluated. The success of phytoremediation process for both Mix A and Mix B can be observed. It is considerably higher for the undersurface alkaline inclusion than for the surface one. Mix B appears to be the best for fluid ash binder and Mix A for lime+cement mixture binder. It is worth noting that the native natural vegetation in Mix N also contributes to the phytoremediation process and that the appropriate plant selection – e.g. Mix A and Mix B – can accelerate this process.

Simulation study of R1234ze and its mixed working medium in TEG‐ORC combined cycle

AbstractThermoelectric generation (TEG) and organic Rankine cycle (ORC) technologies both have their respective limitations in recovering waste heat from ships. However, the combination of TEG and ORC is an effective approach to achieve cascaded waste heat recovery and improve heat utilization efficiency. There has been some progress in research on waste heat recovery in maritime applications based on TEG‐ORC combined cycles. The selection of a working medium is a crucial element that directly influences the design and performance of the entire system, but there is limited research on the impact of different working fluids on combined cycle systems. In this study, a simulation model of a TEG‐ORC combined cycle system was established to examine its output potential using two different working fluids R1234ze and a mixture of R245fa/R1234ze. The results demonstrate that compared to employing the R1234ze working medium, the combined cycle system with the mixed working medium achieved a 13% increase in maximum output power, a 102% improvement in optimum thermal efficiency, and a 53% reduction in optimum power production cost. Additionally, the power output distribution in the system utilizing the mixed working fluid was more uniform compared to the system employing a single working medium. This confirms the great potential of using a mixed working fluid in a combined cycle system.

Calculation and application of elastic modulus of mineral components in tight sandstone based on adaptive method

Abstract For the petrophysics modelling of tight sandstones, the elastic modulus of their sandstone and mudstone components are often substituted with those of quartz and clay, which affects model accuracy. To solve this problem, we innovate an adaptive approach for modelling the rock physics characteristics of tight sandstone. First, based on the relationship between P- and S-wave velocities from well logs and the elastic modulus of the rocks, the equivalent elastic modulus of tight sandstone under saturated conditions is calculated. Next, The Lee model and the Gassmann equation were jointly used to determine the equivalent elasticity modulus of tight sandstone matrix. The upper and lower limits of the equivalent elasticity modulus for mudstone and sandstone are established using the mudstone content curve, the least squares method and the Voigt–Reuss–Hill (V-R-H) model. We used the random-walk algorithm to accurately calculate the equivalent elastic modulus of the sandstone and mudstone components. Finally, using the accurately obtained elastic modulus of sandstone and mudstone, the equivalent elastic modulus of the matrix is calculated. The Kuster–Toksöz (K-T) model is subsequently applied to compute the dry frame bulk modulus and shear modulus of the rock. Following this, the Brie model is used to calculate the elastic modulus of the mixed fluid, thereby completing the construction of the rock physics model for the study area. The results demonstrate that our improved petrophysics model can predict the S-wave velocity curve with ≤ 15% errors relative to the true curve. When sweet spot prediction was performed using reservoir-sensitive parameter (Vp/Vs) derived from the petrophysics template, the agreement between the predictions and well-log data was 80%. Thus, our petrophysics modelling method can be used to predict tight gas reservoirs effectively and will aid efforts to improve petroleum exploration works in the study area.

Optimization of Rotational Hydrodynamic Cavitation Reactor Geometry

A Rotary-Pulsation Apparatus (RPA), also known in the literature as a Rotational Hydrodynamic Cavitation Reactor (RHCR), is a device which typically consists of a rotating mechanism that generates pulsations or vibrations within a fluid. This can be achieved through various means such as mechanical agitation, pneumatic pulses, or hydraulic forces. It is widely used in food, chemical, pharmaceutical, and microbiological industries to improve the mixing of different fluids, dispersion, pasteurization, and sterilization. In the present paper, a CFD study was conducted to develop and optimize the geometry of the RPA’s rotor and stator to induce cavitation in the fluid flow. The effect of cavitation has the potential to improve dispersion and emulsion properties and to significantly reduce operation pressure, in comparison to conventional mixing systems.

Enhanced Acoustic Mixing in Silicon-Based Chips with Sharp-Edged Micro-Structures

The small dimensions of microfluidic channels allow for fast diffusive or passive mixing, which is beneficial for time-sensitive applications such as chemical reactions, biological assays, and the transport of to-be-detected species to sensors. In microfluidics, the need for fast mixing within milliseconds arises primarily because these devices are often used in fields where rapid and efficient mixing significantly impacts the performance and outcome of the processes. Active mixing with acoustics in microfluidic devices involves using acoustic waves to enhance the mixing of fluids within microchannels. Using sharp corners and wall patterns in acoustofluidic devices significantly enhances the mixing by acoustic streaming around these features. The streaming patterns around the sharp edges are particularly effective for the mixing because they can produce strong lateral flows that rapidly homogenize liquids. This work presents extensive characterizations of the effect of sharp-edged structures on acoustic mixing in bulk acoustic wave (BAW) mode in a silicon microdevice. The effect of side wall patterns in different angles and shapes, their positions, the type of piezoelectric transducer, and its amplitude and frequency have been studied. Following the patterning of the channel walls, a mixing time of 25 times faster was reached, compared to channels with smooth side walls exhibiting conventional BAW behavior. The average locally determined acoustic streaming velocity inside the channel becomes 14 times faster if sharp corners of 10° are added to the wall.

Geochemical modeling of U-Ni-Co-As transport and deposition in acidic basinal brines: Implications for unconformity-related U-(Ni-Co-As) mineralization in the Athabasca Basin (Canada)

The unconformity-related uranium (URU) deposits, which are best developed in the Proterozoic Athabasca Basin (Canada), can be divided into the monometallic (U) and polymetallic (U-Ni-Co-As) subtypes. Different models have been proposed to explain the formation of the two subtypes of URU deposits. The conventional “diagenetic-hydrothermal” model suggests that both subtypes formed from oxidizing, acidic basinal brines in a unified mineralization system, whereas a newly proposed model suggests that the polymetallic deposits formed from monometallic U deposits superimposed by Ni-Co-As mineralization. While the second model has been the subject of ongoing debates, there are also unanswered questions in the diagenetic-hydrothermal model; in particular, it remains unclear what geological factors controlled the formation of one subtype or another in a unified mineralization system. This paper aims to address this question with geochemical modeling of hydrothermal U-Ni-Co-As transport and deposition using the Geochemist's Workbench (GWB) software. The conditions for U-Ni-Co-As transport were examined with thermodynamic modeling. The results indicate that highly oxidizing (log fO2(g) > −25), acidic (pH = 3.5) brines can transport large amounts (>100 ppm) of U together with Ni-Co-As, whereas moderately oxidizing (−40 < log fO2(g) < −25), less acidic (3.5 < pH < 6) brines can transport only minor amounts (<1 ppm) of U while still capable of carrying large amounts (>100 ppm) of Ni-Co-As, and very reducing (log fO2(g) < −40) brines with pH from 3.5 to 6 can dissolve only minor amounts (<1 ppm) of U and Ni-Co-As. The mechanisms of U-Ni-Co-As deposition were examined with reaction path modeling involving fluid-rock interaction and fluid-fluid mixing. The results indicate that as a U-Ni-Co-As-bearing, acidic, oxidizing brine progressively reacts with basement rocks or mixes with a reducing fluid, U precipitates before Ni-Co-As in relation to pH increase and fO2(g) decrease. In the case of fluid mixing, while U precipitation can be caused by any of the reducing agents (CH4(aq), H2(aq), H2S(aq), and Fe2+(aq)) in the reducing fluids examined, Ni-Co-As deposition requires the participation of CH4(aq) or H2(aq). Based on the modeling results, it is inferred that U and Ni-Co-As were not transported by the same fluid, otherwise all the URU deposits would be polymetallic. The U was most likely derived from the basin rather than from the basement, because as oxidizing basinal brines infiltrate and interact with basement rocks, their ability to dissolve and transport U quickly diminishes due to fO2(g) decrease and pH increase. In contrast, as these basinal brines infiltrate the upper part of the basement, which is moderately oxidizing, they retain the ability to dissolve and transport significant amounts of Ni-Co-As, enabling the scavenging of these metals from the basement. While all URU mineralization requires U-bearing basinal brines and reducing agents, the formation of polymetallic (U-Ni-Co-As) deposits depends on the availability of Ni-Co-As-rich lithologies in the upper part of the basement, together with an ample supply of robust reducing agents, such as CH4 and H2 that were derived from the deeper part of the basement. Therefore, although the possibility that polymetallic U-Ni-Co-As deposits formed from Ni-Co-As mineralization superimposing on monometallic U deposits cannot be ruled out, the results of this study demonstrate that both polymetallic and monometallic URU deposits can be formed in a unified diagenetic-hydrothermal mineralization system in the Athabasca Basin.

Analysis of hydrodynamics and thermal–hydraulic performance of twisted angle fins within an annular conduit

AbstractThis paper investigated the influence of various twisted angles of fin inserts integrated on the inner heated pipe wall of a double-pipe heat exchanger by analysing the thermal–hydraulic performance through numerical simulations. Results showed twisted angle fin (TAF) induced turbulent fluid flow phenomena, generating transverse and longitudinal vortices, along with swirling flow. This collaboration between the vortices and swirling flow effectively prevents heat trapping and enhances heat transfer from the inner pipe wall through the intensive fluid mixing. Despite longitudinal swirling vortices and turbulence significantly enhance local and global heat transfer performance, they led to increased pressure drop. However, TAF twisting reduces pressure drop by streamlining flow. The performance evaluation criterion (PEC) value is a dimensionless quantity that facilitates the comprehensive evaluation of optimal configurations by comparing the increment in Nusselt number and the increment in friction factor. PEC values greater than 1 indicate that the increase in Nusselt number exceeded the increase in friction factor. Among tested configurations, the twisted fin angles of 60° (TAF60) exhibited the highest improvement in Nusselt number and friction factor, also achieving the highest PEC of 1.59712 at Reynolds number of 1194.71. TAF40 and TAF50 were identified as optimal configurations for enhancing the thermal–hydraulic efficiency, with average PEC values of 1.26893 and 1.27030, respectively. Overall, the study indicated a consistent enhancement trend with increasing twisted angles and emphasizes the significant thermal performance improvement of TAF configurations compared to the smooth conduit. Furthermore, the results showed a converging tendency across all TAF configurations in the percentage improvement in Nusselt number and friction factor, as well as PEC compared to the baseline No fin configuration with increasing Reynolds number, suggesting that future improvements in thermal–hydraulic performance are more dependent on geometric angles than fluid flow velocity.

Hypogene Alteration of Base–Metal Mineralization at the Václav Vein (Březové Hory Deposit, Příbram, Czech Republic): The Result of Recurrent Infiltration of Oxidized Fluids

The Václav vein (Březové Hory deposit, Příbram ore area, Czech Republic) is a base–metal vein containing minor Cu-Zn-Pb-Ag-Sb sulfidic mineralization in a usually hematitized gangue. A detailed mineralogical study using an electron microprobe revealed a complicated multistage evolution of the vein. Early siderite and Fe-rich dolomite were strongly replaced by assemblages of hematite+rhodochrosite and hematite+kutnohorite/Mn-rich dolomite, respectively. In addition, siderite also experienced strong silicification. These changes were associated with the dissolution of associated sulfides (sphalerite, galena). The following portion of the vein contains low-Mn dolomite and calcite gangue with Zn-rich chlorite, wittichenite, tetrahedrite-group minerals, chalcopyrite, bornite, and djurleite, again showing common replacement textures in case of sulfides. The latest stage was characterized by the input of Ag and Hg, giving rise to Ag-Cu sulfides, native silver (partly Hg-rich), balkanite, and (meta)cinnabar. We explain the formation of hematite-bearing oxidized assemblages at the expense of pre-existing “normal” Příbram mineralization due to repeated episodic infiltration of oxygenated surface waters during the vein evolution. Episodic mixing of ore fluids with surface waters was suggested from previous stable isotope and fluid inclusion studies in the Příbram ore area. Our mineralogical study thus strengthens this genetic scenario, illustrates the dynamics of fluid movement during the evolution of a distinct ore vein structure, and shows that the low content of ore minerals cannot be necessarily a primary feature of a vein.

Simultaneous Optimization of Exergy and Economy and Environment (3E) for a Multistage Nested LNG Power Generation System

The study introduces an innovative three-stage nested power generation system that enables the cascading utilization of LNG cold energy. It makes the most of wasted energy by using ship jacket cooling water (JCW) and exhaust gas (EG) as heat sources, a trans-critical carbon dioxide cycle as internal circulation, and utilizing the pressure exergy of LNG. We choose two azeotrope mixing fluids that match the requirements and create four cases for the outer and middle cycle working fluids in the three-stage nested system. To discover the ideal system performance from the perspectives of exergy (E), economy (E), and environment (E), four cases were subjected to multi-objective optimization using the multi-objective particle swarm optimization technique (MOPSO). Finally, the optimal solution was found by applying the TOPSIS decision-making method. Through comparative analysis, the optimal system is selected among the four optimization results. R170 (22.66%) and R1150 (77.34%) are used as the outer circulating working medium, while R170 (90.86%) and R1270 (9.14%) are utilized as the inter-cycle working fluid. The net output work is 575.75 kW, the optimal exergy efficiency is 46.09%, the optimal electricity production cost is $0.04009 per kWh, the carbon dioxide emissions can be reduced by 36,910 tons, and the payback period is 2.548 years. After optimization, a more energy-efficient and environmentally friendly power generation system is obtained.

Diagnosing tracer transport in convective penetration of a stably stratified layer

We use large-eddy simulations to study the penetration of a buoyant plume carrying a passive tracer into a stably stratified layer with constant buoyancy frequency. Using a buoyancy-tracer volume distribution, we develop a method for objectively partitioning plume fluid in buoyancy-tracer space into three regions, each of which corresponds to a coherent region in physical space. Specifically, we identify a source region where undiluted plume fluid enters the stratified layer, a transport region where much of the transition from undiluted to mixed fluid occurs in the plume cap and an accumulation region corresponding to a radially spreading intrusion. This method enables quantification of different measures of turbulence and mixing within each of the three regions, including potential energy and turbulent kinetic energy dissipation rates, an activity parameter and the instantaneous mixing efficiency. We find that the most intense buoyancy gradients lie in a thin layer at the cap of the penetrating plume. This provides the primary stage of mixing between plume and environment and exhibits a mixing efficiency around 50 %. Newly generated mixtures of environmental and plume fluid join the intrusion and experience relatively weak turbulence and buoyancy gradients. As the intrusion spreads radially, environmental fluid surrounding the intrusion is mixed into the intrusion with moderate mixing efficiency. This dominates the volume of environmental fluid entrained into the region containing plume fluid. However, the ‘strongest’ entrainment, as measured by the specific entrainment rate, is largest in the plume cap, where the most buoyant environmental fluid is entrained.

Magma Degassing andGoldMineralizationinthe Alkaline Intrusion- HostedGiltEdgeGoldDeposit,NorthernBlackHills, SouthDakota,USA

Gold mineralization in the Gilt Edge deposit was closely associated with magmatic differentiation and the formation of a Tertiary alkaline intrusive complex within the Lead–Deadwood dome.. Fluid inclusions and trace element geochemistry were used to study fluid evolution and determine sources. Quartz disseminated in unaltered trachyte porphyry hosts two populations of primary inclusions: 1) hypersaline i S–L–V a red hematite crystal and 2) mixtures of L–V and V– L that record phase separation at ~700oC. Whereas samples of hydrothermal quartz collected from in ore zones within and beyond structures (e.g., fault and breccia zones) contain dominant populations of V–L and L–V inclusions, respectively. Mineralization in structures formed from complex fluids of magmatic origin based on inclusions containing five transparent salt crystals and opaque crystals with cubic and round habits that have homogenization temperatures (Th) 650oC and salinities 63 wt.% NaCl equiv. In contrast, broader areas of disseminated mineralization in argillized and propylitized rocks contain hydrothermal quartz hosting large populations of L–V inclusions with Th of 200o360oC and salinities of 10–30 wt.% NaCl equiv., which reflect fluid mixing. Trace element concentrations are significantly higher in samples from structures and define zones of near surface Ag–As–Zn–Pb and deep Au–W–Mo–Cu. Whereas low trace element concentrations characterize propylitized quartz trachyte porphyry, except for high concentrations of Sb and Hg that occur at depth and likely track the retreat of isotherms as the hydrothermal system collapsed. These data show that during differentiation in a deep magma chamber, volatile-rich low-density fluids were periodically degassed into preexisting structures that were reactivated. Gold deposition during four stages of mineralization likely occurred due to boiling, changes in oxygen fugacity, and fluid mixing.

Investigating Enhanced Convection Heat Transfer in 3D Micro-Ribbed Tubes Using Inverse Problem Techniques

The improved heat dissipation observed in 3D micro-ribbed tubes is primarily influenced by the intricate interplay of multiple structural parameters. Nevertheless, research into the coupling mechanisms of these multi-structural parameters remains constrained by the absence of effective methodology in numerical solutions. In the present work, a new 3D micro-rib structure based on discrete adjoint method is established. Firstly, the research examines the interplay of different parameters (such as arrangement, relative roughness height, angle of attack, and circumferential rows) on the thermo-hydraulic performance. It is noted that the heat transfer efficiency is notably impacted by the relative roughness height. And the arrangement methodology dictates the optimal positioning for heat transfer efficiency. An increase in the number of circumferential rows enhances fluid mixing, while the angle of attack plays a crucial role in the formation of longitudinal vortices. Secondly, the coupling optimization technique is employed to obtain the optimal structure featuring non-uniform relative roughness height by the developed numerical solution. Overall, in comparison to the smooth tube, the optimized ribbed tube exhibits a remarkable 64.9% enhancement in performance evaluation criteria. Finally, a notable enhancement of 10.65–22.78% is observed when comparing with the prevailing micro-rib structures.

Effect of Ultrasound on Microstructure and Properties of Aluminum–Copper Friction Stir Lap Welding

In this paper, the influence mechanism of ultrasound on plastic flow and microstructure features of the aluminum–copper friction stir lap welding (Al/Cu-FSLW) process is systematically investigated by adjusting the welding speed and improving the shear rheology in the plastic stirring zone. Through adjusting the ultrasonic vibration and welding speed, the directional control of mechanical properties is realized. It is found that increasing the welding speed properly is beneficial to enhance the mechanical shear between the tool and the workpiece, thus forming more staggered layered structures at the copper side and improving the tensile strength of the weld. The acoustic softening enhances the viscoplastic fluid mixing and strengthens the mechanical interlock of the Al/Cu lap interface. As the welding speeds increase or ultrasonic vibration is applied, the thickness of Al/Cu intermetallic compound (IMC) decreases, and the tensile strength and elongation of the Al/Cu joints are enhanced. Compared with adjusting the welding speed, the ultrasonic vibration can further refine the copper particles which are stirred into the plastic zone, and the thinning effect of ultrasound on IMC layers is better than that of increasing welding speed. At the welding speed of 60 mm/min, the IMC layer thickness is reduced by 42% under ultrasonic effect. In three welding speed conditions, the UV reduced the absolute value of the effective heat of formation (EHF) for Al2Cu and Al4Cu9 and suppressed the formation of AlCu phase. Meanwhile, only when the welding speed is increased from 60 mm/min to 100 mm/min can the formation of AlCu be suppressed. Under the ultrasonic optimization, the stable improvement of welding efficiency is ensured.

The bronchoalveolar lavage dilution conundrum: an updated view on a long-standing problem.

Bronchoalveolar lavage (BAL) is used by researchers to study molecular interactions within healthy and diseased human lungs. However, the utility of BAL fluid measurements may be limited by difficulties accounting for dilution of the epithelial lining fluid (ELF) sampled and inconsistent collection techniques. The use of endogenous markers to estimate ELF dilution has been proposed as a potential method to normalize acellular molecule measurements in BAL fluid, but these markers are also imperfect and prone to inaccuracy. The focus of this report is to review factors that affect the interpretation of acellular molecule measurements in lung ELF and present original data comparing the performance of several BAL dilution markers during health and in a human endobronchial endotoxin challenge model of acute inflammation. Our findings suggest that incomplete ELF and lavage fluid mixing, flux of markers across the alveolar barrier, and lung inflammation are all possible factors that can affect marker performance. Accounting for these factors, we show that commonly used markers including urea, total protein, albumin, and immunoglobulin M are likely unreliable BAL dilution markers. In contrast, surfactant protein D appears to be less affected by these factors and may be a more accurate and biologically plausible marker to improve the reproducibility of acellular BAL component measurements across individuals during health and inflammatory states.NEW & NOTEWORTHY In this report, mathematical prediction models and real-world measurements are used to compare the performance of molecular markers of dilution in bronchoalveolar lavage fluid samples. Effects of acute inflammation within individual subjects are highlighted. These findings inform recommendations for normalizing measurements across bronchoalveolar lavage samples and highlight the need for additional markers to improve the rigor of translational studies utilizing bronchoalveolar lavage measurements.