Fluid Speed Research Articles

The Development of Serum Amyloid P as a Possible Therapeutic.

Pentraxins such as serum amyloid P (SAP; also known as PTX2) regulate several aspects of the innate immune system. SAP inhibits the differentiation of monocyte-derived fibroblast-like cells called fibrocytes, promotes the formation of immuno-regulatory macrophages, and inhibits neutrophil adhesion to extracellular matrix proteins. In this minireview, we describe how these effects of SAP have led to its possible use as a therapeutic, and how modulating SAP effects might be used for other therapeutics. Fibrosing diseases such as pulmonary fibrosis, cardiac fibrosis, liver fibrosis, and renal fibrosis are associated with 30–45% of deaths in the US. Fibrosis involves both fibrocyte differentiation and profibrotic macrophage differentiation, and possibly because SAP inhibits both of these processes, in 9 different animal models, SAP inhibited fibrosis. In Phase 1B and Phase 2 clinical trials, SAP injections reduced the decline in lung function in pulmonary fibrosis patients, and in a small Phase 2 trial SAP injections reduced fibrosis in myelofibrosis patients. Acute respiratory distress syndrome/ acute lung injury (ARDS/ALI) involves the accumulation of neutrophils in the lungs, and possibly because SAP inhibits neutrophil adhesion, SAP injections reduced the severity of ARDS in an animal model. Conversely, depleting SAP is a potential therapeutic for amyloidosis, topically removing SAP from wound fluid speeds wound healing in animal models, and blocking SAP binding to one of its receptors makes cultured macrophages more aggressive toward tuberculosis bacteria. These results suggest that modulating pentraxin signaling might be useful for a variety of diseases.

Performance Analysis and Visualization of Canard and Fuselage Effects on Flow Patterns around a Straight-Body-Type-Fuselage (SBTF) Fighter Models with Experimental Method in Water Tunnel

Performance analysis and visualization of canard and fuselage effects on flow patterns around an SBTF fighter model have been conducted. An SBTF fighter model with an experimental method in a water tunnel would easily reveal visually the vortex dynamics phenomenon that occurred. Testing has been done, with some form of non-canard and canard aircraft in a water tunnel, on vortex dynamics and aerodynamic power on the aircraft model. The stream demonstration used a fluid speed of 0.1 m/s and Reynolds number 6.577x103 on a 1:110 scale model and measured using dye injection method with a print ink type with a mixture ratio of 1:8. The result of the research using GAMA water tunnel showed the aerodynamic force and vortex dynamics phenomenon that happened on the model aircraft. The research on the benefits of the canard is also done by examining the performance and the flow visualization of an SBTF fighter without fuselage, with the symmetrical plane and with the regular fuselage in a water tunnel. The results showed that the use of canard affected the lift, drag, and flow pattern around the wings. The use of canard can enhance the lift of the plane and function to delay the stall by restoring the flow above the wing which should have experienced turbulence back into laminar so that the fighter can maneuver to a higher angle of attack (AoA) without stalling. It is identified that canard and fuselage play significant roles on the design of a fighter. The design choice of the fuselage and the employment of canard are fundamental to support the ability of maneuver and agility of the fighter.

Efficacy study of Chiari type I malformation treatment using neuroendoscope assisted with neuronavigation and intraoperative ultrasound

Objective To explore and evaluate the clinical outcome of neuroendoscopic treatment assisted with neuronavigation and intraoperative ultrasound for Chiari type Ⅰ malformation. Methods Between January 2011 to June 2017, 132 patients underwent neuroendoscopic atlantooccipital decompression at Neurosurgery Department of Shanxi Provincial People′s Hospital. During the operations, the surgical fields were lightened by the illuminator of endoscope. All manipulations were conducted with neuronavigation. Intraoperative ultrasound was applied in 34 cases to detect the flowing speed of cerebrospinal fluid (CSF) which determined whether the outer dura was opened. We evaluated the clinic efficacy based on the Tator criteria which was classified into excellent (symptomatic improvement), good (symptomatic stability) and poor (symptomatic worsening). Results All 132 patients had follow-up lasting for 6-24 months. There were 92 patients who were determined as excellent in recovery, 36 as stable and 4 as worse. The clinical symptoms were improved in 69.7% (92/132). The clinical symptoms were improved in 65.3% (64/98) of the cases without intraoperative ultrasound and 82.4% (28/34) among those with intraoperative ultrasound, although there was no significant difference (P=0.06). MRI follow-up was conducted in 78 cases with comorbidity of myelosyringosis, which was improved in 41.0% (32/78). There were no cases of scalp hydrops in the occipital area or cerebrospinal fluid leakage post operation. Four cases reported intracranial infection. Conclusion Neuroendoscope-assisted atlantooccipital decompression, combined with neurona-vigation, intraoperative ultrasound and dura opening, seems to have satisfactory effect in treatment of Chiari type Ⅰ malformation and low complication rate, which still needs study involving larger number of samples. Key words: Arnold-Chiari malformation; Natural orifice endoscopic surgery; Neuronavigation; Ultrasonography, Doppler; Atlantooccipital decompression

Reaction kinetics of phenols and p-nitrophenols in flowing aerated aqueous solutions generated by a discharge plasma jet.

In this paper, we propose a method for removing phenols and p-nitrophenols (PNPs) from flowing aqueous solutions generated by atmospheric pressure plasma jets (APPJs). For analyzing the removal characteristics, multiple techniques were used, including flow speed analysis of the aerated solution, optical emission spectroscopy (OES), and liquid chromatography. In addition, the reaction kinetics of diffusion and activation control processes were evaluated using aerated fluid speed variation and the corresponding activation energy. From these results, the relative intensities of hydroxyl radicals produced by an APPJ in water were found to be stronger than those in air and to decrease with increasing flow speed. Furthermore, the reaction kinetics were found to be diffusion-controlled when the solution flow speed was low and activation-controlled under high solution flow speed. It was also found that the degradation efficiency was enhanced with increasing flow speed, which increased the discharge voltage and temperature of the solution and changed the initial pH value when TiO2/UV catalysis was used. From the complex relationship between the reactive species, fluid diffusion, and discharge parameters in wastewater described herein, it is anticipated that these findings will facilitate new approaches to both the design and optimization of discharge reactors intended for wastewater treatment.

A nonlinear surface-stress-dependent model for vibration analysis of cylindrical nanoscale shells conveying fluid

• A nonlinear surface-stress-dependent nanoshell model is developed. • Flowing fluid is taken into account in the cylindrical nanoshells. • Nonlinear free vibration of fluid-conveying cylindrical nanoshells is studied. • Surface stress influences nonlinear vibration characteristics of fluid-conveying nanoshells. • Shell theory is used to model the present fluid-conveying nanostructures. A nonlinear surface-stress-dependent nanoscale shell model is developed on the base of the classical shell theory incorporating the surface stress elasticity. Nonlinear free vibrations of circular cylindrical nanoshells conveying fluid are studied in the framework of the proposed model. In order to describe the large-amplitude motion, the von Kármán nonlinear geometrical relations are taken into account. The governing equations are derived by using Hamilton's principle. Then, the method of multiple scales is adopted to perform an approximately analytical analysis on the present problem. Results show that the surface stress can influence the vibration characteristics of fluid-conveying thin-walled nanoshells. This influence becomes more and more considerable with the decrease of the wall thickness of the nanoshells. Furthermore, the fluid speed, the fluid mass density, the initial surface tension and the nanoshell geometry play important roles on the nonlinear vibration characteristics of fluid-conveying nanoshells.

Estimation of the average velocity of a fluid by means of a single modulated beam

We propose an optical method to estimate the average velocity of a liquid fluid circulating through a square pipe with transparent walls. The velocity is obtained from the photovoltage data measured in a semiconductor crystal when is illuminated with a single intensity modulated laser beam, transmitted through the pipe in a perpendicular direction of the moving fluid. Experimental results considering parameters as wavelength, modulation frequency, particles concentration and fluid speed were obtained, and a comparative statistical analysis considering additional measurements obtained by Laser Doppler Anemometry (LDA) as a reference, was performed too.

Conducting-Polymer, Magnetohydrodynamic Devices for Sustained Microfluidic Pumping

We have developed a mechanism to indefinitely extend unidirectional pumping of fluids by redox-magnetohydrodynamics (R-MHD) in a controllable fashion for the purpose of facilitating lab-on-a-chip applications. Electrochemistry is fundamental to R-MHD microfluidics. It allows conversion of electronic current at electrodes to ionic current, j, that when in the presence of a magnetic field, B, generates the MHD force, FB, (the magnetic component of the Lorentz force). FB is a body force that can be generated in a localized space (without a channel, inlet, outlet, or exterior pumping mechanism) and is governed by the right-hand rule when the ionic current travels perpendicularly to the magnetic field. We use microelectrodes for pumping, which are patterned in different, individually-addressable geometries on chips, and can be selectively activated to start, stop, reverse, adjust speed, and manipulate profiles of the fluid flow. Therefore the fluid flow is programmable. By modifying the electrodes first with poly(3,4-ethylenedioxythiophene), PEDOT, a conducting polymer, we have eliminated bubble formation and electrode corrosion, while accommodating a wider variety of electrolyte solutions compatible with chemical analysis [1]. We have merged the uniform, flat flow profile generated by R-MHD between coplanar pairs of PEDOT-modified band electrodes with epitaxial light sheet confocal microscopy to perform continuous high-resolution fluorescence imaging of cellular suspensions that can count and differentiate white blood cells (i.e. granulocytes, monocytes, and lymphocytes) in a self-contained cartridge with no moving parts [2]. A disadvantage of the conducting-polymer modified R-MHD, however, is that the duration of pumping in a single direction is limited by the amount of charge contained in the polymer. We have developed a new strategy that extends the pumping time of PEDOT-modified R-MHD that involves reconfiguring the spatial and temporal relationships between j and B. Namely we have developed a simple and small device containing permanent magnets of opposite orientations in a linear array that slides beneath the microfluidics chamber in synchrony with the switching of the ionic current. This approach offers several advantages over sinusoidal AC-MHD [3], including a more constant speed with less disruption, a higher magnetic field (to produce higher fluid speeds), and dramatically simplified and less bulky instrumentation. We will report this novel approach to sustaining R-MHD pumping and its effect on the temporal evolution of the fluid flow and the impact on the flow profiles. Acknowledgements: We are grateful for financial support from National Science Foundation (CBET-1336853), the Women’s Giving Circle, and Arkansas Bioscience Institute, the major research component of the Arkansas Tobacco Settlement Proceeds Act of 2000.

Multi-Response Optimization Of Machining Parameters In CNC Turning Of AISI 316L Stainless Steel Using MQL Nano fluids

In this research work, optimization of machining parameters in plain turning operation to minimize surface roughness and cutting temperature by applying Taguchi based Desirability function analysis and ANOVA method under Nano cutting fluid environment is performed. Experiments have been performed by plain turning of AISI 316L stainless steel on CNC lathe under MQL setup with Multi-walled carbon Nanotube (MWCNT) inclusions using carbide inserts. Carbon Nano tubes are mixed in a specific ratio (0.20% by wt.) with the cutting fluid. The impact of input parameters on the response variables such as surface roughness and cutting temperature are analysed by using desirability function based approach. Experimental results reveal that feed rate is said to have more effect on the response variables followed by depth of cut, type of cutting fluid and spindle speed.

Predicting the breaking strength of gravity water waves in deep and intermediate depth

We revisit the classical but as yet unresolved problem of predicting the strength of breaking 2-D and 3-D gravity water waves, as quantified by the amount of wave energy dissipated per breaking event. Following Duncan (J. Fluid Mech., vol. 126, 1983, pp. 507–520), the wave energy dissipation rate per unit length of breaking crest may be related to the fifth moment of the wave speed and the non-dimensional breaking strength parameter $b$. We use a finite-volume Navier–Stokes solver with large-eddy simulation resolution and volume-of-fluid surface reconstruction (Derakhti & Kirby, J. Fluid Mech., vol. 761, 2014a, pp. 464–506; J. Fluid Mech., vol. 790, 2016, pp. 553–581) to simulate nonlinear wave evolution, with a strong focus on breaking onset and postbreaking behaviour for representative cases of wave packets with breaking due to dispersive focusing and modulational instability. The present study uses these results to investigate the relationship between the breaking strength parameter $b$ and the breaking onset parameter $B$ proposed recently by Barthelemy et al. (J. Fluid Mech., vol. 841, 2018, pp. 463–488). The latter, formed from the local energy flux normalized by the local energy density and the local crest speed, simplifies, on the wave surface, to the ratio of fluid speed to crest speed. Following a wave crest, when $B$ exceeds a generic threshold value at the wave crest (Barthelemy et al. 2018), breaking is imminent. We find a robust relationship between the breaking strength parameter $b$ and the rate of change of breaking onset parameter $\text{d}B/\text{d}t$ at the wave crest, as it transitions through the generic breaking onset threshold ($B\sim 0.85$), scaled by the local period of the breaking wave. This result significantly refines previous efforts to express $b$ in terms of a wave packet steepness parameter, which is difficult to define robustly and which does not provide a generically accurate forecast of the energy dissipated by breaking.

Redox-Magnetohydrodynamically Controlled Fluid Flow with Poly(3,4-ethylenedioxythiophene) Coupled to an Epitaxial Light Sheet Confocal Microscope for Image Cytometry Applications.

We present the merging of two technologies to perform continuous high-resolution fluorescence imaging of cellular suspensions in a deep microfluidics chamber with no moving parts. An epitaxial light sheet confocal microscope (e-LSCM) was used to image suspensions enabled by fluid transport via redox-magnetohydrodynamics (R-MHD). The e-LSCM features a linear solid state sensor, oriented perpendicular to the direction of flow, that can bin the emission across different numbers of pixels, yielding electronically adjustable optical sectioning. This, in addition to intensity thresholding, defines the axial resolution, which was validated with an optical phantom of polystyrene microspheres suspended in agarose. The linear fluid speed within the microfluidics chamber was uniform (0.16-2.9%) across the 0.5-1.0 mm lateral field of view (dependent upon the chosen magnification) with continuous acquisition. Also, the camera's linear exposure periods were controlled to ensure an accurate image aspect ratio across this span. Poly(3,4-ethylenedioxythiophene) (PEDOT) was electrodeposited as an immobilized redox film on electrodes of a chip for R-MHD, and the fluid flow was calibrated to specific linear speeds as a function of applied current. Images of leukocytes stained with acridine orange, a fluorescent, amphipathic vital dye that intercalates DNA, were acquired in the R-MHD microfluidics chamber with the e-LSCM to demonstrate imaging of biological samples. The combination of these technologies provides a miniaturizable platform for large sample volumes and high-throughput, image-based analysis without the requirement of moving parts, enabling development of robust, point-of-care image cytometry.

TiO2-water nanofluid in a porous channel under the effects of an inclined magnetic field and variable thermal conductivity

The TiO2-water based nanofluid flow in a channel bounded by two porous plates under an oblique magnetic field and variable thermal conductivity is formulated as a boundary-value problem (BVP). The BVP is analytically solved with the homotopy analysis method (HAM). The result shows that the concentration of the nanoparticles is independent of the volume fraction of TiO2 nanoparticles, the magnetic field intensity, and the angle. It is inversely proportional to the mass diffusivity. The fluid speed decreases whereas the temperature increases when the volume fraction of the TiO2 nanoparticles increases. This confirms the fact that the occurrence of the TiO2 nanoparticles results in the increase in the thermal transfer rate. The fluid speed decreases and the temperature increases for both the pure water and the nanofluid when the magnetic field intensity and angle increase. The maximum velocity does not exist at the middle of the symmetric channel, which is in contrast to the plane-Poiseuille flow, but it deviates a little bit towards the lower plate, which absorbs the fluid with a very low suction velocity. If this suction velocity is increased, the temperature in the vicinity of the lower plate will be increased. An explicit expression for the friction factor-Reynolds number is then developed. It is shown that the Hartmann number of the nanofluid is smaller than that of pure water, while the Nusselt number of the nanofluid is larger than that of pure water. However, both the parameters increase if the magnetic field intensity increases.

Intermittent back-flash phenomenon of supersonic combustion in the staged-strut scramjet engine

The scramjet-powered hypersonic vehicle depends on the sustained and stable supersonic combustion processes, which requires a balance between the flame propagation velocity and the fluid speed. Flame propagation inside a kerosene-fueled staged-strut scramjet engine was experimentally studied in Mach 3.0 incoming flow with the stagnation temperature of 1899 K. The fuel mass flow rate was linearly controlled by an adjustable venturi during the dynamic injection experiment. Two inspection windows were installed on the side and top walls of the combustor respectively. A mirror was utilized to change the light path from the top window to be horizontal to capture the flame structure in the two windows simultaneously. A high-speed imaging camera was employed to capture the flame propagation process described in this short communication. Video imaging showed that the flame was mainly stabilized in the boundary-layer separation region when the upstream equivalence ratio was less than 0.2. In particularly, this short communication reported an intermittent back-flash phenomenon while the fuel equivalence ratio was turned up near to 0.2. The back-flash flame was suggested to be detonation wave by a primary C-J analysis.

Infiltration behaviour of liquids over fibres or woven

The high porosity of fabrics and fibres have hindered the study of the interaction between fluids and those kind of materials. In order to understand penetration mechanisms of polymeric matrices or woven sealing, some properties such as wettability or capillarity must be analysed. The fluid speed through some woven could be compared with metallic meshes in those is easy to determine pores size. In this work it is tried to solve these problems from a theoretical point of view by using hydrostatic laws and capillarity effect.

The passage of fluid into the peritoneal cavity during hysteroscopy in pre-menopausal and post-menopausal patients

The present study aimed to determine the amount of fluid medium passing through the Fallopian tubes into the peritoneal cavity during a hysteroscopy. This was done to understand the pathophysiology of complications related to the hysteroscopy. Conducted in a general hospital setting, the study examined the fluid inflow–outflow during a hysteroscopy both in pre- and post-menopausal women. A hysteroscopy was performed vaginoscopically for both diagnostic and therapeutic procedures. The study involved 117 patients. 84 (71.8%) of them were pre-menopausal and 33 (28.2%) were classified as post-menopausal. The fluid volume difference in the peritoneal cavity prior to hysteroscopy was 26.0 ± 4.2 mL in the pre-menopausal and 7.7 ± 2.4 mL (p = .001) in the post-menopausal group. The pre-menopausal group’s flow rate through the Fallopian tubes was 1.5 ± 0.2 mL/min. In the post-menopausal group, it was 0.4 ± 0.1 mL/min (p < .05). It was found that during the hysteroscopy in the pre-menopausal patients, more fluid flows through the Fallopian tubes and at a higher flow rate.Impact statementWhat is already known on this subject? The complications during a hysteroscopy (HSC) are usually fluid-related and can result in adverse events such as a fluid overload, the dissemination of malignant cells, or electrolyte misbalance. Currently, there is a poor understanding of how HSC fluid behaviour impacts on the pathophysiology of these adverse procedure effects.What do the results of this study add? There have been no quantitative studies of the behaviour of fluid inside the uterine cavity during HSC, which means a quantification of fluid inflow and absorption is required. Our study adds a quantitative understanding of fluid behaviour during HSC. It shows increased rates of fluid passage, as well as fluid speed, into the peritoneal cavity in pre-menopausal patients.What are the implications of these findings for clinical practice and/or further research? Due to the higher rates of fluid passage and speed in pre-menstrual patients, caution regarding the complications during hysteroscopy and further studies are needed on the impact of different fluid distribution.

Volumetric segmentation-free method for rapid visualization of vascular wall shear stress using 4D flow MRI.

To develop a rapid segmentation-free method to visualize and compute wall shear stress (WSS) throughout the aorta using 4D Flow MRI data. WSS is the drag force-per-area the vessel endothelium exerts on luminal blood; abnormal levels of WSS are associated with cardiovascular pathologies. Previous methods for computing WSS are bottlenecked by labor-intensive manual segmentation of vessel boundaries. A rapid automated segmentation-free method for computing WSS is presented. Shear stress is the dot-product of the viscous stress tensor and the inward normal vector. The inward normal vectors are approximated as the gradient of fluid speed at every voxel. Subsequently, a 4D map of shear stress is computed as the partial derivatives of velocity with respect to the inward normal vectors. We highlight the shear stress near the wall by fusing visualization with edge-emphasized anatomical data. As a proof-of-concept, four cases with aortic pathologies are presented. Visualization allows for rapid localization of pathologic WSS. Subsequent analysis of these pathological regions enables quantification of WSS. Average WSS during peak systole measures approximately 50-60 cPa in nonpathological regions of the aorta and is elevated in regions of stenosis, coarctation, and dissection. WSS is reduced in regions of aneurysm. A volumetric technique for calculation and visualization of WSS from 4D Flow MRI data is presented. Traditional labor-intensive methods for WSS rely on explicit manual segmentation of vessel boundaries before visualization. This automated volumetric strategy for visualization and quantification of WSS may facilitate its clinical translation.

Numerical investigation of pressure distribution in a low specific speed centrifugal pump

To study the pressure distribution of the volute casing, front casing and back casing in a prototype centrifugal pump, the pressure experiments and numerical simulations are carried out at six working conditions in this paper. The experimental results shows that the asymmetry of static pressure distribution on volute casing and front cavity is caused by the tongue of the volute and it may result in high radial and axial resultant force which can cause vibration and noise in the centrifugal pump. With the increasing of flow rate, the asymmetry of static pressure distribution and the magnitude of static pressure values reduce. The numerical results indicate that the pressure fluctuation near the tongue is strongest and it becomes slighter at point away from the tongue. With the increasing of flow rate, the local high-pressure region in impeller passage reduces and the flow becomes smoother accordingly, whereas the fluid speed becomes much higher which may cause further flow losses. The results predicted by numerical simulation are in coincident with the experimental ones. It shows that the turbulence model for simulating the flow field in centrifugal pumps is feasible.

Pressure Gradient, Power, and Energy of Vortices

We consider small vortices, such as tornadoes, dust devils, waterspouts, small hurricanes at low latitudes, and whirlpools, for which the Coriolis force can be neglected, and hence within which the flow is cyclostrophic. Such vortices are (at least approximately) cylindrically symmetrical about a vertical axis through the center of a calm central region or eye of radius reye. In the region reye≤r≤rmax fluid (gas or liquid) circulates about the eye with speed v∝rn(n<0). We take rmax to be the outer periphery of the vortex, where the fluid speed is reduced to that of the surrounding wind field (in the cases of tornadoes, dust devils, water-spouts, and small hurricanes at low latitudes) or deemed negligible (in the case of whirlpools). If n=-1, angular momentum is conserved within the fluid itself; if n≠-1, angular momentum must be exchanged with the surroundings to ensure conservation of total angular momentum. We derive the steepness and upper limit of the pressure gradients in vortices. We then discuss the power and energy of vortices. We compare the kinetic energy of atmospheric vortices and the power required to maintain them against frictional dissipation with the same quantities for Earth’s atmosphere as a whole. We explain why the kinetic energy of atmospheric vortices must be replaced on much shorter timescales than is the case for Earth’s atmosphere as a whole. Comparisons of cyclostrophic flow with geostrophic and friction-balanced flows are then provided. We then consider an analogy that might be drawn, at least to some extent, with gravitational systems, considering mainly spherically-symmetrical and cylindrically-symmetrical ones. Generation of kinetic energy at the expense of potential energy in fluid vortices, in geostrophic and friction-balanced flows, and in gravitational systems is then discussed. We explain the variations of pressure and gravitational gradients corresponding to generation of kinetic energy equaling, exceeding, and falling short of frictional dissipation. In the Appendix, we describe a simple method for maximizing power extraction from environmental fluid (water or air) flows, which is also applicable to artificial (e.g., internal combustion) engines. In summary, we provide an overview of features and energetics of Earth’s environmental fluid flows (focusing largely on vortices) and of gravitational analogies thereto that, even though mainly semiquantitative, hopefully may be helpful.

Effect of radial turbo-expander design on off-highway vehicle organic Rankine cycle system efficiency

Compared to other waste heat recovery (WHR) technologies, organic Rankine cycle (ORC) system is regarded as the most candidate technology due to its simplicity, low cost and small back pressure impact. Expanders are crucial components of an ORC system along with working fluid. In this simulation study, an in-house code has been developed to explore the effect of various working fluids on optimum radial expander geometry. In addition, an off-design turbine analysis has been employed in order to evaluate the performance of the calculated expander geometry under various engine operating conditions. Finally, the effect of various expanders' designs on fuel consumption and emissions of an off-highway vehicle is presented. Compared to conventional diesel powertrain systems, the WHR system showed an up to 5.7% increase in brake torque and brake power and a 5.4% reduction in BSFC. The results also showed that working fluid and expander speed are critical parameters on the performance of the proposed powertrain configuration.

Multiple stable isotope fronts during non-isothermal fluid flow

Stable isotope signatures of oxygen, hydrogen and other elements in minerals from hydrothermal veins and metasomatized host rocks are widely used to investigate fluid sources and paths. Previous theoretical studies mostly focused on analyzing stable isotope fronts developing during single-phase, isothermal fluid flow. In this study, numerical simulations were performed to assess how temperature changes, transport phenomena, kinetic vs. equilibrium isotope exchange, and isotopic source signals determine mineral oxygen isotopic compositions during fluid-rock interaction. The simulations focus on one-dimensional scenarios, with non-isothermal single- and two-phase fluid flow, and include the effects of quartz precipitation and dissolution.If isotope exchange between fluid and mineral is fast, a previously unrecognized, significant enrichment in heavy oxygen isotopes of fluids and minerals occurs at the thermal front. The maximum enrichment depends on the initial isotopic composition of fluid and mineral, the fluid-rock ratio and the maximum change in temperature, but is independent of the isotopic composition of the incoming fluid. This thermally induced isotope front propagates faster than the signal related to the initial isotopic composition of the incoming fluid, which forms a trailing front behind the zone of transient heavy oxygen isotope enrichment. Temperature-dependent kinetic rates of isotope exchange between fluid and rock strongly influence the degree of enrichment at the thermal front. In systems where initial isotope values of fluids and rocks are far from equilibrium and isotope fractionation is controlled by kinetics, the temperature increase accelerates the approach of the fluid to equilibrium conditions with the host rock. Consequently, the increase at the thermal front can be less dominant and can even generate fluid values below the initial isotopic composition of the input fluid. As kinetics limit the degree of isotope exchange, a third front may develop in kinetically limited systems, which propagates with the advection speed of the incoming fluid and is, therefore, traveling fastest. The results show that oxygen isotope signatures at thermal fronts recorded in rocks and veins that experienced isotope exchange with fluids can easily be misinterpreted, namely if bulk analytical techniques are applied. However, stable isotope microanalysis on precipitated minerals may – if later isotope exchange is kinetically limited – provide a valuable archive of the transient thermal and hydrological evolution of a system.

Effect of temperature and fluid speed on the corrosion behavior of carbon steel pipeline in Qatari oilfield produced water

Metals integrity, such as carbon steel used in pipeline network can be seriously damaged by produced water causing serious corrosion problems. This can result in significant threats to safe operation of the oilfield facilities and leads to considerable economic losses. In this study, the effect of produced water from the North oilfield of Ras Laffan in Qatar on corrosion and scaling of carbon steel is investigated using electrochemical methods. The specimen rotation speed ranged from 0 to 2m/s and temperature between 20 and 60°C were used as test parameters for the study. X-ray power diffractometer (XRD) and scanning electron microscopy (SEM) techniques were employed in the analysis of the corroded steel samples. It was found that the corrosion rate increased with increasing temperature and specimen rotation speed. These results also showed that the steel reacted with the corrosive ions at the early stage of its exposure to the produced water leading to the formation of corrosion products on the steel surface in which CaCO3 scale layer were deposited on the surface of the specimen as loose products due to the presence of large amounts of Ca2+ and HCO3− ions contained in the Rass Lafan oilfield produced water. More so, pitting and cracks were observed on the steel surface which increased as the temperature and specimen rotation speeds were increased, suggesting localized corrosion mechanism.