Relative Flow Rate Research Articles

A novel micromixer based on coastal fractal for manufacturing controllable size liposome

The traditional lipid preparation methods are complex, time-consuming, and consume a large amount of reagents, increasing costs and difficulties. Although microfluidic technology is considered a promising solution, achieving controllable liposome production with a simple and inexpensive microfluidic mixing device remains an important problem. This paper presents a wall-type micro-mixer based on coastal zone fractals. Four parameters related to the geometric shape of the coastline fractal in the microchannel are used as design variables, and the mixing index is the objective function. Single-objective optimization numerical analysis of the primary wall-type fractal baffle micromixer under four Reynolds numbers conditions yields the optimal structural configuration. Visualization experiments verify the correctness and accuracy of the numerical simulation, and the optimized mixer is used to produce liposomes. The results show that the micro-mixer with the optimal double-sidewall cross arrangement enhances chaotic convection and improves mixing efficiency. At Re = 0.1 and Re = 100, the mixing efficiency reaches 99%, 50.44% higher than the reference design. By changing the relative flow rates of lipid and aqueous solutions, microfluidic blank liposomes with a particle size of 165.12 ± 11.6 nm and a polydispersity index of 0.35± are obtained. This wall-type fractal micro-mixer has broad application prospects due to its high mixing efficiency.

Comprehensive validation of a compact laser speckle contrast imaging system for vascular function assessment: from the laboratory to the clinic.

Proper organ functioning relies on adequate blood circulation; thus, monitoring blood flow is crucial for early disease diagnosis. Laser speckle contrast imaging (LSCI) is a noninvasive technique that is widely used for measuring superficial blood flow. In this study, we developed a portable LSCI system using an 805-nm near-infrared laser and a monochrome CMOS camera with a 10 × macro zoom lens. The system achieved a high-resolution imaging (1280 × 1024 pixels) with a working distance of 10 to 35 cm. The relative flow velocities were visualized via a spatial speckle contrast analysis algorithm with a 5 × 5 sliding window. In vitro experiments demonstrated the system's ability to image flow velocities in a fluid model, and a linear relationship was observed between the actual flow rate and the relative flow rate obtained by the system. The correlation coefficient (R2) exceeded 0.83 for volumetric flow rates of 0 to 0.2 ml/min when channel widths were greater than 1.2 mm, and R2 > 0.94 was obtained for channel widths exceeding 1.6 mm. Comparisons with laser Doppler flowmetry (LDF) revealed a strong positive correlation between the LSCI and LDF results. In vivo experiments captured postocclusive reactive hyperemic responses in rat hind limbs and human palms and feet. The main research contribution is the development of this compact and portable LSCI device, as well as the validation of its reliability and convenience in various scenarios and environments. Future applications of this technology include evaluating blood flow changes during skin injuries, such as abrasions, burns, and diabetic foot ulcers, to aid medical institutions in treatment optimization and to reduce treatment duration.

Control of Liquid Hydrocarbon Combustion Parameters in Burners with Superheated Steam Supply

A numerical simulation of reacting mixture flow in a full-scale combustion chamber of a prototype burner with a fuel-sprayed jet of superheated steam and a controlled excess air ratio was performed based on a verified model. The influence of steam jets on the combustion parameters of the created prototype device was analyzed based on the results, and a comparison with data from various atmospheric burners, including evaporative and spray types, direct-flow and vortex types, and those with natural and forced (regulated) air supply, was made. Various schemes for supplying steam to burner devices were discussed. It was shown that the relative steam consumption is a parameter for controlling the emission of toxic combustion products, such as NOx and CO, for all designs. A high burner performance is achieved when superheated steam is supplied at more than 250 °C with a relative steam flow rate of >0.6. The design features of the burner systems and operational parameters that ensure high thermal and environmental efficiency when burning various types of fuel and waste are identified.

Green hydrogen production from thermoelectric condensation of ambient moist air

As the world transitions towards reducing carbon emissions, green hydrogen produced through solar-powered alkaline water electrolysis (AWE) presents a promising eco-friendly fuel option. In response to the challenges caused by global warming, including air moisture saturation leading to unbalanced rainfall, flooding, concern for freshwater depletion and the limited availability of water and energy sources in arid regions. The present study introduces a novel method of integrating thermoelectric water condenser (TEWC) and AWE for green hydrogen production in remote and arid regions where both the water and the conventional energy sources are scarce. Numerical simulations of the present study show that the impact of relative humidity, temperature, and air flow rate significantly affect water condensation, energy requirement, and hydrogen production. The TEWC and AWE models showed excellent agreement with the experimental data. TEWC model reveled that the highest water production rate of 1.50 kg/(m2h) is achieved at ambient air temperature of 308 K and relative humidity of 80%. Furthermore, increasing the moist air flow from 1 m/s to 2 m/s results in a 47.5% increase in water production rate. The AWE model showed that cell's performance improved with higher temperatures, lower electrode-separator gap, and overpotentials. The hydrogen evolution rate reached a maximum of 5.2 kg/(m2h) at current density of 1.4 A/cm2 and potential of 3.96 V. By optimizing the TEWC and AWE systems the integrated method proved to be an efficient way of converting moist air into green hydrogen using solar energy, making it a viable and sustainable setup in remote arid regions.

Stretch-induced hepatic endothelial mechanocrine promotes hepatocyte proliferation

Background & Aims: Partial hepatectomy (PHx)-induced liver regeneration causes the increase in relative blood flow rate within the liver, which dilates hepatic sinusoids and applies mechanical stretch on liver sinusoidal endothelial cells (LSECs). Heparin-binding EGF-like growth factor (HB-EGF) is a crucial growth factor during liver regeneration. We aimed to investigate whether this sinusoidal dilation-induced stretch promotes HB-EGF secretion in LSECs and what the related molecular mechanism is. Approach & Results: In vivo PHx, ex vivo liver perfusion and in vitro LSEC mechanical stretch were applied to detect HB-EGF expression in LSECs and hepatocyte proliferation. Knockdown or inhibition of mechanosensitive proteins were used to unravel the molecular mechanism in response to stretch. This stretch triggers amplitude- and duration-dependent HB-EGF up-regulation in LSECs, which is mediated by Yes-associated protein (YAP) nuclear translocation and binding to TEAD. This YAP translocation is achieved in two ways: On one hand, F-actin polymerization-mediated expansion of nuclear pores promotes YAP entry into nucleus passively. On the other hand, F-actin polymerization up-regulates the expression of BAG family molecular chaperone regulator 3 (BAG-3), which binds with YAP to enter nucleus cooperatively. In this process, β1-integrin serves as a target mechanosensory in stretch-induced signaling pathways. This HB-EGF secretion-promoted liver regeneration after 2/3 PHx is attenuated in endothelial cell-specific Yap1-deficient mice. Conclusions: Our findings indicate that mechanical stretch-induced HB-EGF up-regulation in LSECs via YAP translocation can promote the hepatocyte proliferation during liver regeneration through a mechanocrine manner, which deepens the understanding of the mechanical-biological coupling in liver regeneration.

Mechanistic insights into how mixing factors govern polyelectrolyte-surfactant complexation in RNA lipid nanoparticle formulation

Hypothesis: Lipid nanoparticle self-assembly is a complex process that relies on ion pairing between nucleic acids and hydrophobic cationic lipid counterions for encapsulation. The chemical factors influencing this process, such as formulation composition, have been the focus of recent research. However, the physical factors, particularly the mixing protocol, which directly modulates these chemical factors, have yet to be mechanistically examined using a reproducible mixing platform comparable to the industry standard. We here utilize Flash NanoPrecipitation (FNP), a scalable rapid mixing platform, to isolate and systematically investigate how mixing factors influence this complexation step, first by using a model polyelectrolyte-surfactant system and then generalizing to a typical RNA lipid nanoparticle formulation.Experiments: Aqueous polystyrene sulfonate (PSS) and cetrimonium bromide (CTAB) solutions are rapidly homogenized using reproducible FNP mixing and controlled flow rates at different stoichiometric ratios and total solids concentrations to form polyelectrolyte-surfactant complexes (PESCs). Then, key mixing factors such as total flow rate, inlet stream relative volumetric flow rate, and magnitude of flow fluctuation are studied using both this PESC system and an RNA lipid nanoparticle formulation.Findings: Fluctuations in flow as low as ± 5 % of the total flow rate are found to severely compromise PESC formation. This result is replicated in the RNA lipid nanoparticle system, which exhibited significant differences in size (132.7 nm vs. 75.6 nm) and RNA encapsulation efficiency (34.0 % vs. 82.8 %) under fluctuating vs. steady flow. We explain these results in light of the chemical variables isolated and studied; slow or nonuniform mixing generates localized concentration gradients that disrupt the balance between the hydrophobic and electrostatic forces that drive complex formation. These experiments contribute to our understanding of the complexation stage of lipid nanoparticle formation and provide practical insights into the importance of developing controlled mixing protocols in industry.

The relationship between intraosseous catheter tip placement, flow rates, and infusion pressures in a high bone density cadaveric swine (Sus scrofa) model.

Intraosseous (IO) infusion is a life-preserving technique when intravenous access is unobtainable. Successful IO infusion requires sufficiently high flow rates to preserve life but at low enough pressures to avoid complications. However, IO catheter tips are often misplaced, and the relative flow rates and pressures between IO catheter tips placed in medullary, trabecular, and cortical bone are not well described, which has important implications for clinical practice. We developed the Zone Theory of IO Catheter Tip Placement based on bone density and proximity to the venous central sinus and then tested the influence of catheter tip placement locations on flow rates and pressures in a cadaveric swine model. Three cross-trained participants infused 500mL of crystalloid fluid into cadaveric swine humerus and sternum (N=210 trials total) using a push‒pull method with a 60 cm3 syringe. Computed tomography scans were scored by radiologists and categorized as zone 1 (medullary space), zone 2 (trabecular bone), or zone 3 (cortical bone) catheter tip placements. Differences between zones in flow rates, mean pressures, and peak pressures were assessed using analysis of variance and analysis of covariance to account for participant and site differences at the p<0.05 threshold. Zone 1 and zone 2 placements were essentially identical in flow rates, mean pressures, and peak pressures (each p>0.05). Zone 1 and zone 2 placements were significantly higher in flow rates and lower in pressures than zone 3 placements (each p<0.05 or less). Within the limitations of an unpressurized cadaveric swine model, the present findings suggest that IO catheter tip placements need not be perfect to acquire high flow rates at low pressures, only accurate enough to avoid the dense cortical bone of zone 3. Future research using in vivo animal and human models is needed to better define the clinical impact of IO catheter placement on infusion flow rates and pressures.

Mass Transfer Performance of a Rotating Spiral: Comparison with Conventional Contacting Methods

Previous work by the authors develops a novel technology for counter-current contacting of immiscible fluid phases based on a rotating spiral channel. The work has established theoretical modelling allowing prediction of mass transfer rates for physical absorption and desorption of dilute solute species and has verified the main hydrodynamic elements of the theory, with experimental measurements over a wide range of flow rates and liquid viscosity. A key feature of rotating spiral contacting is that the relative thicknesses of the phase layers is constant throughout the contacting process and, along with the relative phase flow rates, can be varied regardless of phase and solute properties to produce optimum conditions for the contacting. It has been shown that there are two criteria that determine the optimum. First, the flow rate ratio of the phases is matched to the equilibrium distribution of the solute between the two phases, so that sufficient solvent phase flows to allow full removal of solute from the processed stream. Second, the relative layer thicknesses should maximise specific throughput, i.e. the flow rate of the processed stream per device volume. These ideas of optimum contacting guide a comparison here of recent mass transfer data for the spiral with corresponding literature data for the packed column and rotating packed bed.

South African flag sign: A Red Flag in ECG

A method is developed to allow cardiologists to find changes in the blood flow rate in larger coronary arteries, caused by the appearance of their pathological tortuosity, and a hemodynamic significance of those changes based on the data taken from the appropriate coronarographies only. This method is based on replacement of blood flows in the originally healthy and subsequently pathologically tortuous artery with the corresponding averaged ones, and subsequent calculation of flow characteristics of interest in terms of the corresponding averaged flow characteristics. It allows one not to take account of a number of identical factors for the originally healthy and subsequently pathologically tortuous segment of the investigated artery, and gives one the possibility to determine the flow parameters of concern at any time after carrying out a coronarography. In addition, it is not associated with solving complicated technical problems, and does not require special facility to be used, special professional training and significant financial and temporal expenses. The method was successfully tested in-vitro and then applied to appropriate patients. It was found that the hemodynamic significance of the tortuosity generally increases/decreases as the number of the tortuosity arcs increases/decreases. Also, strong correlation between fundamental geometric and hemodynamic characteristics of the tortuosity and basic clinical indicators of the corresponding patients was established. This suggests a strong independent influence of the tortuosity on the clinical symptoms of the corresponding patients. The critical values for the number of the tortuosity arcs, the relative blood flow rate loss and the rate of angina.

Experimental parametric evaluation of adsorption characteristics for silica gel - water based open-bed system for seasonal thermal energy storage

This study aims to investigate the potential of using commercial silica gel as an energy storage material in a bulk-scale open bed adsorption-based system to achieve efficient domestic heating using renewable energy sources. Designing an efficient thermal energy storage (TES) system for practical use requires understanding of the sorption properties of the adsorbent and the effects of different operating and physical parameters on the sorption process. One critical parameter that significantly affects the energy storage density when scaling up from a laboratory to a prototype system is the amount of adsorbent in the reactor. Surprisingly, this aspect has been overlooked in previous studies. To address this research gap, a laboratory-scale test rig was designed and constructed. This rig enables the evaluation of the effects of different operating parameters (such as relative humidity, flow rate, and regeneration temperature) and physical parameters (such as the quantity of adsorbent and particle diameter) on the energy storage density of silica gel and the temperature lift in the process. The water adsorption capacity of the silica gel was measured in-house to assist in future theoretical modelling of a prototype TES system. Optimum operating conditions were determined for the system, with a relative humidity of 80 %, an air flow rate of 100 L/min, and material regeneration at 120 °C. The system's performance in terms of material energy storage density and maximum temperature lift was observed for varying amounts of adsorbent, particle diameter, and regeneration temperature at these optimal operating conditions. Finally, the required storage volume to meet domestic space heating demands was estimated based on optimal discharging conditions and compared to other experimental and theoretical studies involving silica gel-based energy storage systems.

Water transport in PEMFC with metal foam flow fields: Visualization based on AI image recognition

Water transport is an essential process in proton exchange membrane fuel cells (PEMFC). For the novel metal foam flow fields, water transport is difficult to be visualized and still remains inadequately understood. In this work, for the first time, the two-phase flows in the metal foam flow fields of a transparent PEMFC was visualized by using an artificial intelligence (AI) image recognition method. In order to distinguish water from the metal foam ligaments, a scoring system was developed, which effectively solved the problem of inconsistent reflectance of liquid water between the ligament and the gas diffusion layer. According to the state of liquid water, the scoring system categorized the local images into three labels of waterless state, wet state, and slug state for AI image recognition network training. The trained AI image recognition model was then used to visualize the liquid water state in the metal foam flow fields under different operating conditions of relative humidity (RH), temperature, and inlet flow rate. Results show that, since the porous structure of the metal foam provides flexible transport paths, the PEMFC can operate effectively in a wide range of wet states. Even a 25% difference in the wet-state percentage between different operating conditions yields an almost consistent voltage. The increased slugs in the flow fields are the primary reason for the performance degradation of the PEMFC. At a high current density of 2 A/cm2, the voltage is as low as 0.03 V when the slug state occupies 35% of the flow fields (100% RH, 60 °C, 1.0 SLPM cathode inlet flow rate), and as high as 0.56 V when the slug state is absent in the flow fields (100% RH, 60 °C, 2.0 SLPM cathode inlet flow rate). The present work provides a novel approach for the studies of water transport in PEMFC.

Determination of Effective Parameters for Hydropower Plants’ Energy Generation: A Case Study

The current study aims to conduct a comprehensive analysis of the key parameters that affect the energy output of the Bagisli Hydropower Plant, located on the Zap River in the Dicle (Tigris) basin of Turkey. It considers the daily data for the time interval of 2016–2019 related to flow rate, precipitation, and temperature in relation to the generation of electricity. The relationship between energy output and flow rate is evident; however, the energy production is limited by the design flow rate. The largest flow rates were seen during the spring season after the occurrence of peak precipitation, which exhibited a shifting pattern. Similarly, energy generation also reaches its highest level during this time period. Another outcome of this study is that there is no apparent association between daily precipitation and daily energy generation. Moreover, a novel correlation with an R2 value of 0.89 has been proposed, in the deviation band of ±20%, to estimate energy generation when only flow rate data are available.

Impact of steam flow into a combustion chamber of a contact gas-steam installation on its energy characteristics

Relevance. Reduction of natural gas consumption and emissions of harmful substances into the environment based on introduction of water vapor into a combustion chamber of a contact gas-steam installation. Aim. To carry out numerical studies on the influence of relative steam flow into the combustion chamber of the contact gas-steam installation on its energy characteristics. Objects. Contact gas-steam installations based on gas turbines with steam injection into the combustion chamber. Methods. Numerical methods based on material and energy balances of systems and elements of gas-steam installations. Results. Based on the calculation of the thermal circuit of the contact gas-steam installation, the authors have studied the influence of the relative steam flow into the combustion chamber on its energy characteristics. It was determined that the absolute electrical efficiency of the contact gas-steam installation increases linearly with growth of relative steam flow into the combustion chamber. The range of changes in the relative steam flow into the combustion chamber strongly depends on the temperature of the gases behind the combustion chamber and the compression ratio in the air compressor; the smaller these parameters are, the greater the range of changes. The maximum efficiency of 56% for all options is achieved at the maximum relative steam flow into the combustion chamber. It was established that the excess air coefficient, depending on the relative steam flow rate, decreases linearly, and the higher the temperature of the gases behind the combustion chamber and the compression ratio in the air compressor, the greater the rate of decline and the smaller the range of changes in the relative steam flow rate. It was revealed that the efficiency coefficient strongly depends on the relative steam flow into the combustion chamber, the temperature of the gases behind it and the degree of compression in the air compressor; with increasing these parameters, it increases linearly. It was determined that the temperature of the gases at the outlet of the gas turbine also strongly depends on the relative flow of steam into the combustion chamber, the temperature of the gases at its outlet and the compression ratio in the compressor. With an increase in the relative flow of steam into the combustion chamber, this temperature increases linearly from 600 to 700°C, while the higher the temperature of the gases at the outlet of the combustion chamber and the compression ratio in the compressor, the higher the temperature of the gases at the outlet of the gas turbine. The authors revealed the dependence of useful work on a gas turbine shaft on the relative steam flow into the combustion chamber. With an increase in the relative steam flow, the useful work on the gas turbine shaft increases along the branch of the parabola. The higher the temperature of the gases behind the combustion chamber and the compression ratio in the compressor, the steeper the branch of the parabola, but the smaller the range of changes in the relative steam flow. It was established that with an increase in the relative steam flow, the gas flow to the gas turbine decreases according to a hyperbola. Moreover, the lower the temperature of the gases behind the combustion chamber and the compression ratio in the compressor, the more the gas flow to the gas turbine drops.

Effect of fertilization on emitter clogging in drip irrigation using high sediment water: Perspective of sediment discharge capacity

Emitter clogging is a major issue that restricts drip irrigation technology with high-sediment loaded water. Traditional anti-clogging method using water filtration is not only costly but also consumes an excessive amount of energy. This study provided a new anti-clogging method for drip irrigation systems by directly desilting sediment from the emitter flow channel. The emitter SDC was assessed using three types of fertilizers [Urea (UN), ammonium poly-phosphate (APP), and mono-ammonium phosphate (MAP)] and a control group (CK, no fertilizer). The results showed that most sediment can be discharged through the emitter flow channel. Nitrogen fertilizer applications significantly affected (P<0.05) the emitter SDC. Both APP and MAP significantly reduced the emitter SDC, causing an average decrease of 0.61μm-1.21μm in the control threshold for particle size μ0 and 0.55%−1.67% in the sediment discharge rate (φe), while the sediment deposition and discharge ratio (φ) increased by 0.004%−0.040% on average. However, UN application effectively increased the emitter SDC, with an increase of 0.45μm-0.53μm in the control threshold for particle size μ0, 0.70%−5.99% in φe, while the sediment deposition and discharge ratio (φ) decreased by 0.002%−0.003%. The relative average flow rate (Dra) among different fertilizer treatments demonstrated DraUN＞DraCK＞DraMAP＞DraAPP. The findings suggested that the emitter SDC can be improved by using suitable fertilizer type. This study clarified the effect of fertilizer on the sediment discharge capacity of emitter, with implications for the management of high-sediment loaded water in irrigation.

Estimation of river discharge using Monte Carlo simulations and a 1D hydraulic model based on the artificial multi-segmented rating curves at the confluence of two rivers

During extreme floods caused by climate change, reliable flow discharge data are essential for successful reservoir operation to mitigate downstream flood damage. Generally, the flow discharge is computed using the rating curve (RC) established from the relationship between the flow rate and water stage level. Determining the parameters of rating curves is subject to uncertainties related to the difficulties and limitations of flow monitoring in covering a wide range of flow variations. Especially at river confluences, the uncertainties are pronounced when floods occur owing to several factors such as roughness change, backwaters, and levee overflow. The Seomjin River Basin in Korea suffered from flood inundation that occurred at the tributary confluence during an extreme flood in 2020. To identify a reliable flow rate of the main stream and tributary, this study proposes an indirect flow assessment scheme using a 1D hydrodynamic simulation model to find the best simulated water level in an iterative manner based on Monte Carlo (MC) simulations. With a large amount of discharge data generated from random-number combinations, it is possible to obtain the best results automatically by specifying the reliability limitation considering the uncertainty of the predetermined RC parameters associated with the roughness coefficient. Nash Sutcliffe Efficiency (NSE) was incorporated to evaluate the reproduced water level to meet the threshold specified for NSE ≥ 0.75. The simulated flowrates computed from the revised RC and roughness coefficients revealed an error range of 8%–36.6% compared with the design flood. The approach proposed in this study is applicable for determining the valid parameters necessary to create a revised RC at an existing water level gauge station, where the uncertainties of the RC are pronounced, particularly in the vicinity of the channel confluence.

On the scalability of helium-filled soap bubbles for volumetric PIV

The scalability of experiments using PIV relies upon several parameters, namely illumination power, camera sensor and primarily the tracers light scattering capability. Given their larger cross section, helium-filled soap bubbles (HFSB) allow measurements in air flows over a significantly large domain compared to traditional oil or fog droplets. Controlling their diameter translates into scalability of the experiment. This work presents a technique to extend the control of HFSB diameter by geometrical variations of the generator. The latter expands the more limited range allowed by varying the relative helium-air mass flow rates. A theoretical model predicts the bubble size and production rate, which is verified experimentally by high-speed shadow visualization. The overall range of HFSB produced in a stable (bubbling) regime varies from 0.16 to 2.7 mm. Imaging by light scattering of such tracers is also investigated, in view of controversies in the literature on whether diffraction or geometrical imaging dominate the imaging regime. The light scattered by scaled HFSB tracers is imaged with a high-speed camera orthogonal to the illumination. Both the total energy collected on the sensor for a single tracer, as well as its peak intensity, are found to preserve scaling with the square of the diameter at object magnification of 10–1 or below, typical of PIV experiments. For large-scale volumetric applications, it is shown that varying the bubble diameter allows increasing both the measurement domain as well as the working distance of the imagers at 10 m and beyond. A scaling rule is proposed for the latter.Graphical abstract

Experimental study on voltage instability of proton exchange membrane fuel cell: Types and boundaries

ABSTRACT This paper presents an experimental study on the voltage instability in proton exchange membrane fuel cells operating at high current densities, which is important for improving their reliability and durability. Based on experimental findings regarding transparent fuel cells, a method is proposed to identify different types of voltage instability via statistical results of linear changing rate and oscillation amplitude. The types and boundaries of voltage instability are elucidated while evaluating the impact of cathode relative humidity and flow rate on voltage instability. The findings reveal that (1) the voltage instability is greatly influenced by the cathode-side relative humidity and flow rate, (2) there are three typical types of voltage instability: voltage decline, voltage oscillation, and both, and (3) voltage decline occurs at low cathode humidity, while voltage oscillation becomes more severe at large cathode humidity and low flow rate; (4) Reduction of water content in the membrane leads to voltage decline, while an increase in water content in the catalyst layer, gas diffusion layer, and channels leads to voltage oscillation. A full-condition map diagram demonstrating voltage instability during high current density conditions is presented. The method for creating this map for voltage instability will be employed to enhance fuel cell performance.

In Situ pH Measurement in Microfluidic Porous Media Indicated by Surfaces Functionalized with Polyaniline (PAni)

Aqueous phase pH is a critical metric with significant importance in understanding reactive transport processes in porous media. At the microscale, however, traditional pH detection methods face challenges in capturing dynamic pH due to limited sample volume and sensing time. To overcome these limitations, we leveraged micro/nanofabrication techniques to create a microfluidic porous medium coated with polyaniline (PAni) on its surface. Using this innovative microfluidic design, we achieved colorimetric delineation of pH spatial distribution with fast response and robustness in porous media. By conducting coinjection tests with hydrochloric acid (pH = 2) and DI water (pH ≈ 5.8, equilibrated with air) at various flow rates and relative flow rate ratios in a sandstone-patterned microfluidic device, we observed dynamic pH changes in porous media and obtained a comprehensive understanding of the acid advection-diffusion dynamics. The results highlighted the capability of PAni to enable microscale pH sensing. This research contributes to the development of advanced porous media microfluidics and applications, particularly in mass transfer limits during reactive transport of carbon dioxide sequestration and geological hydrogen storage.

Experimental evaluation of water infiltration through concrete-geocell liners

In this article we study the infiltration rate and flow characteristics of water through concrete-geocell liners by experimental and analytical means. Geocells filled with concrete have been used in the construction of many hydraulic works, such as shore protections (both marine and riverine), spillways, and canal liners; these liners have been reported to offer high performance, as they are able to withstand large flow velocities, hydrodynamic effects, and environmental stresses, while still being more cost-effective than other hard-armor systems such as reinforced concrete and articulating concrete blocks (ACBs). Despite their increasing use there is no report of their hydraulic conductivity in the literature, which this paper aims to fulfil. First, an analytical solution to the problem is achieved by parting from the incompressible Navier-Stokes equations and applying reasonable assumptions to arrive at a formula that relates flow rate to pressure gradient, fluid properties, and importantly, the hydraulic aperture (the idealized gap at the concrete-geocell interface); this gap is then estimated using the ACI-209 method for the prediction of concrete shrinkage, resulting in the proposed semi-analytical method. The formulation was then evaluated experimentally by conducting hydraulic tests on full scale geocell specimens filled with concrete under conditions that are deemed representative of real case applications. The results indicate that the proposed methodology has satisfactory predictive capabilities and provides flow rate estimates in accordance with measured data.

Numerical investigation of cooling performance of 3D-printable cooling structure for aero-engine combustor

Thermal protection is an essential technology for gas turbine hot components to cope with the unprecedented thermal loads, and to ensure their enduring and efficient operation. A 3D-printable hybrid cooling cellular structure is suggested in this paper, the cooling property of which in a Can-type combustion chamber with chemical reaction considered is evaluated in detail. Reynolds Stress Turbulence Model together with the non-premixed combustion model are used to resolve the detailed flow structures and turbulence-chemistry interactions. Cases of cooling cellular with various film hole inclined angles are compared and analyzed. Results show that the cooling cellular can reduce the temperature of combustor liner noticeably, especially at the region near the second row of dilution holes. Meanwhile, the cooling performance is improved as the decrease of inclined angle, with an improvement of 29.1% as the inclined angle range from 90° to 30°, because the smaller incline angle is more resilient to coolant lift-off. A comparation with effusion cooling scheme is also made and concluded that the case of hybrid cooling exhibits a 673%-1409% higher porosity ratio, while the cooling effectiveness is reduced about 3.6%-8.3%. The lower performance of the hybrid cooling is explored further with a flat plate conjugate heat transfer numerical test, and ultimately attributed to the relative lower flow rate of coolant air induced by higher pressure loss of hybrid cooling cellular. Finally, the compound angle is further introduced into the hybrid cooling cellular. Results show that the impact of compound angle on cooling property depends highly on the angle between the film outflow and the swirling main-flow. The performance of compound angle cases will only increase when cooling cellular deflects in opposite directions of swirling flow, not vice versa. Overall, the hybrid cooling cellular shows a great potential in the cooling design of combustor liner. A smaller incline angle with compound angle deflected in the opposite direction of the swirling main-flow are also recommended for increased cooling performance.