Fluid Flow Control Research Articles

A novel biomimetic nanocomposite exhibiting petal wetting phenomenon: fabrication and experimental investigations

A functional composite material that simultaneously exhibits hydrophobicity and water droplet adhesion has monumental potential in controlling fluid flow, studying phase separation, and biological research. This article reports the fabrication of a petal wetting biomimetic Boron Nitride Nanotubes (BNNTs) -Polydimethylsiloxane (PDMS) nanocomposite achieved by drop casting. The petal effect was investigated by non-destructive techniques. The nanotubes were synthesized by chemical vapor deposition at 1150 °C and were characterized by x-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. The mean diameter of the nanotubes was found to be 70 nm. The nanocomposites had BNNT fillers ranging from 0.5 wt% to 2 wt%. Water contact angles for pure PDMS polymer was 94.7° and for the 2 wt% BNNT-PDMS nanocomposite was 132.4°. The petal wetting nanocomposite displayed a characteristic trait of high contact angle hysteresis. The surface roughness parameters of the nanocomposites were determined by atomic force microscopy. Laser scanning confocal microscopy aided in analyzing the droplet penetration and in observing the trapped air between the water droplet and the nanocomposite surface. Based on surface observations, roughness parameters, and the extent of droplet penetration by the surface, we shed light on the Cassie impregnating wetting regime followed by the biomimetic nanocomposite. Such a surface would be beneficial in the study of the embryogenesis of cells and aid in moisture collection.

Directional manipulation of diffusio-osmosis flow by design of solute-wall and solvent-wall interactions

Understanding of diffusio-osmosis, the flow induced by a solute gradient acting in narrow interfacial layers at a nanoscale solid-liquid interface, is of great value in view of the increasing importance of micro- and nano-fluidic devices and self-propelling particles. Using molecular dynamics simulations, we employ an appropriate strategy for direct simulation of diffusio-osmosis flows, mimicking a realistic experiment without any assumed external forces. It allows us to obtain reliable flow details, which are hard to obtain in experiments. We found that the solvent-wall interaction, previously overlooked in the classical paradigm, plays a critical role in the diffusio-osmosis process. In particular, diffusio-osmosis is controlled by the interaction difference between the solute-wall and solvent-wall. When the solute-wall interaction is stronger (weaker) than the solvent-wall, a surface excess (depletion) of solute particles on the solid-liquid interface is formed, which induces diffusio-osmosis flow towards a low (high) concentration. We modified the classical Derjaguin expression to include the effect of nanoscale hydrodynamics boundary conditions for the accurate prediction of diffusio-osmosis characteristics. Overall, our results provide clear guidance for controlling fluid flow and manipulating the motion of colloids under tunable solute concentrations.

The Coupling State Equations and the Symplectic Algorithm for Control Rod Drop and Fluid Flow

In this paper, a nonlinear state equation describing the coupling between control rod drop and fluid flow was proposed to solve the problem of control rod drop in nuclear reactor. The state equation has a uniform format for different fluid states in the process of control rod drop, which can conveniently deals with the problem for different working conditions. In order to efficiently analyze the falling process, accurately capture the sudden change of flow state and ensure the numerical stability of time integral, an adaptive time step preserving algorithm is proposed in this paper. Numerical examples show that the numerical model proposed in this paper can accurately calculate the key data such as displacement, velocity, acceleration and falling time of the control rod in the falling process with a large time step, and the calculated results are in good agreement with those obtained by commercial software.

A rock core wettability index using NMR T measurements

Wettability is a critical parameter that controls fluid flow and distribution as well as recovery efficiency in reservoir rocks. The sensitivity of Nuclear Magnetic Resonance (NMR) relaxation measurements to wettability is well-known. Here we develop a new approach to calculate a wettability index based on low field NMR transverse ( T 2 ) measurements which is simpler than existing models in the literature and still affords good agreement with Amott-Harvey and USBM wettability test results. The model relies on the emergence of a bulk like relaxation signal from the non-wetting phase in partially oil/water saturated cores. Unlike other models in the literature, which require T 2 measurements at up to four different saturation states, our model only requires measurements at two partial saturation states; irreducible brine ( S wi ) and residual oil ( S or ). The performance of the model was tested using experimental results from different core types aged with light and heavy oils containing varied amounts of asphaltene. Different wettability conditions with Amott-Harvey/USBM values ranging from −0.39 to 0.79 were thus tested. When compared with measured reference wettability indices from the Amott-Harvey or USBM method, the model prediction showed good agreement (the calculated mean absolute error was 0.10). Additionally, improved accuracy was achieved relative to existing comparable models in the literature for the range of samples considered. • This study presents a new model to calculate a wettability index based on NMR T 2 measurements. • The model requires less calibration points than most existing models. • The model relies on the emergence of a bulk like relaxation signal from the non-wetting phase in partially saturated cores. • The model is tested in different rock types including carbonates and sandstones. • The predicted wettability indices showed good agreement with measured reference values from the Amott-Harvey method.

Effects of Nonuniform Permeability in Variable Bdpm Under a Sinusoidal Arrangement to Control Heat Transfer and Fluid Flow in a Channel - a Numerical Simulation

Effects of Nonuniform Permeability in Variable Bdpm Under a Sinusoidal Arrangement to Control Heat Transfer and Fluid Flow in a Channel - a Numerical Simulation

Ball pen writing-without-ink: a truly simple and accessible method for sensitivity enhancement in lateral flow assays.

Lateral flow assays (LFAs), a popular point-of-care testing platform, have found widespread applications from laboratory to clinics. However, LFA-based testing is still subject to limited detection sensitivity, especially for classical gold nanoparticle-based LFAs. Inspired by traditional pen-based writing technologies, we developed a ball pen writing-without-ink method to amplify the detection signal of LFAs through controlling fluid flow rate. An enhancement of detection sensitivity by two times was obtained. Since the underlying mechanism of this method to improve detection sensitivity is to control the flow rate of the liquid on paper, it may be suitable for most paper-based platforms.

Venturi-effect rotating concentrators and nonreciprocity characteristics based on transformation hydrodynamics

The development of hydrodynamics metamaterials and transformation hydrodynamics has enriched the methods of fluid flow control. In the proposed study, coupling flow rotation and amplification functions, hydrodynamic rotating concentrators with tensorized viscosity are designed based on transformation hydrodynamics. Through numerical simulations, we have demonstrated that the rotating concentrators can simultaneously magnify and rotate the velocity in creeping flows. In the central area of the rotating concentrators, the fluid velocity is amplified, exhibiting the venturi effect; in the external area of the rotating concentrators, the flow state is not interfered with due to the presence of the rotating concentrators, maintaining the original flow state. Additionally, we discover and explain the mechanisms of the rotational hysteresis phenomena that are caused by the nonreciprocity of spatial coordinate transformations. The proposed studies 1) extend and optimize the traditional flow concentrators, 2) raise new approaches for applications related to Venturi effects, and 3) shed light on the design of nonreciprocal coordinate transformations for metamaterials.

A Battery Powered on-Chip Peristaltic Pump for Lab-On-A-Chip Applications

Low-cost and controllable fluid manipulation in small scale is important to biomedical research, and disease testing and diagnostics. In the midst of global disease outbreaks and pandemics such as Ebola and Covid-19, rapid and low-cost testing and diagnostics have become even more crucial. Lab-on-a-chip platforms are good candidates to be applied in these circumstances due their small footprints and lower-costs which enable rapid-prototyping of these devices. However, providing controlled fluid flow handling in small scale for on-chip devices is not currently suitable for point-of-care applications due to the expensive fluid pumping systems that currently used in most of the lab-on-a-chip devices. In this work, a low-cost and practical peristaltic pump is developed using 3D printing and open-sourced microcontroller platform Arduino boards. The entire system is designed to be portable and capable of producing metered fluid flow in small scale devices. The developed device is characterized to provide adjustable fluid flow control between 1.7 µL/s to 23 µL/s which is suitable for many on-chip applications. The peristaltic pump developed in this work can be used in lab-on-a-chip applications due to its simplicity and low-cost.

Control of capillary driven fluid flows for safe operation of spacecraft fluid supply systems using artificial porous media

In weightlessness, capillary forces become the main driving forces in the flow of liquids. Fuel supply of engines being started in weightlessness, water supply to life support systems in habitable modules, heat exchange using capillary pumps – all those processes rely heavily on capillary forces. Thus, safety and reliability of Space mission strongly depends on our skills in controlling capillary driven fluid flows. Adequate mathematical models for predicting capillary driven imbibition in artificial porous specimens are needed. The paper discusses the features of the flow of liquids through a porous medium under the action of capillary forces under microgravity conditions. An important feature of such flows is the hysteresis effect: in the case of multiple imbibition of a porous medium, the liquid flows in different ways through the dry medium and through the medium moistened in the process of previous imbibitions. This effect is observed during experiments on repeated imbibition of an artificial porous medium during parabolic flights of an Airbus A300-ZeroG aircraft organized by the European Space Agency. With each subsequent parabola, the liquid rises to a greater height. Modeling such processes requires special mathematical models described in this work. Comparison of the results of numerical modeling and experimental data provides a unique opportunity to choose empirical constants on an experimental basis thus developing a robust tool for predicting fluid behavior in hydraulic loops of Space vehicles.

CMOS-Based Electrokinetic Microfluidics With Multi-Modal Cellular and Bio-Molecular Sensing for End-to-End Point-of-Care System.

The importance of point-of-care (POC) bio-molecular diagnostics capable of rapid analysis has become abundantly evident after the outbreak of the Covid-19 pandemic. While sensing interfaces for both protein and nucleic-acid based assays have been demonstrated with chip-scale systems, sample preparation in compact form factor has often been a major bottleneck in enabling end-to-end POC diagnostics. Miniaturization of an end-to-end system requires addressing the front-end sample processing, without which, the goal for low-cost POC diagnostics remain elusive. In this paper, we address bulk fluid processing with AC-osmotic based electrokinetic fluid flows that can be fully controlled, processed and automated by CMOS ICs, fabricated in TSMC 65 nm LP process. Here, we combine bulk fluid flow control with bio-molecular sensing, cell manipulation, cytometry, and separation-all of which are controlled with silicon chips for an all-in-one bio-sensing device. We show CMOS controlled pneumatic-free bulk fluid flow with fluid velocities reaching up to 160 μm/s within a microfluidic channel of 100 × 50 μm 2 of cross-sectional area. We incorporate electrode arrays to allow precise control and focused cell flows ( ±2 μm precision) for robust cytometry, and for subsequent separation. We also incorporate a 16-element impedance spectroscopy receiver array for cell and label-free protein sensing. The massive scalability of CMOS-driven microfluidics, manipulation, and sensing can lead to a new design space and a new class of miniaturized sensing technologies.

Modelling of Electrode Size Influence on Electrochemical MHD Processes

The presented article describes a simulation of an electrochemical reaction in a presence of a magnetic field using a custom model implemented into Ansys Fluent. The influence of electrode size and the effect of scan rate is investigated further. The results show that the magnetic field can significantly increase mixing and transport of species towards the electrode, which results in higher obtained current densities. Additionally, this method can be used to control fluid flow in microfluidic devices.

Pumpless three-dimensional photo paper-based microfluidic analytical device for automatic detection of thioredoxin-1 using enzyme-linked immunosorbent assay.

Microfluidic-based biosensors have been developed for their precise automatic reaction control. However, these biosensors require external devices that are difficult to transport and use. To overcome this disadvantage, our group made an easy-to-use, cheap, and light pumpless three-dimensional photo paper-based microfluidic analytical device (3D-μPAD; weight: 1.5g). Unlike conventional paper-based microfluidic analytical devices, the 3D-μPAD can be used to control fluid flow in a 3D manner, thus allowing sophisticated multi-step reaction control. This device can control fluid flow speed and direction accurately using only the capillary-driven flow without an external device like a pump. The flow speed is controlled by the width of the microfluidic channel and its surface property. In addition, fluid speed control and 3D-bridge structure enable the control of fluid flow direction. Using these methods, multi-step enzyme-linked immunosorbent assay (ELISA) can be done automatically in sequence by injecting solutions (sample, washing, and enzyme's substrate) at the same time in the 3D-μPAD. All the steps can be performed in 14min, and data can be analyzed immediately. To test this device, thioredoxin-1 (Trx-1), a biomarker of breast cancer, is used as the target. In the 3D-μPAD, it can detect 0-200ng/mL of Trx-1, and the prepared 3D-μPAD Trx-1 sensor displays excellent selectivity. Moreover, by analyzing the concentration of Trx-1 in real patients and healthy individuals' blood serum samples using the 3D-μPAD, and comparing results to ELISA, it can be confirmed that the 3D-μPAD is a good tool for cancer diagnosis.

Active Flow Control Devices for Wing Load Alleviation

Active flow control has not found wide application in aircraft due to a combination of technical challenges, costs, and small impact on overall aircraft performance. Future applications, like alleviating dynamic loads, could be made possible through continuous improvement of flow control methods and increasingly restrictive environmental regulations. To date, few studies deal with active flow control for load alleviation on transport aircraft wings at high Reynolds and Mach numbers. A systematic assessment of flow control methods for load alleviation is therefore carried out. Multiple flow actuation schemes for gust load alleviation through dynamic lift reduction are investigated over a range of flight conditions using two-dimensional Reynolds-averaged Navier–Stokes simulations. Unsteady gust interactions with a clean airfoil produce target loads for load alleviation. Actuator performance is consequently evaluated based on an engineering model. The results show that select fluidic actuators outperform micro-mechanical actuators at low flight speeds and feature similar steady load response as trailing edge flaps for the entire flight envelope. The Coandă jet features relatively low mass flow requirements, but necessitates minimal dual-slot blowing for baseline performance recovery. The results of this study highlight the potential of fluidic flow control schemes for implementation into a dedicated gust load alleviation system.

Encapsulation of Lutein via Microfluidic Technology: Evaluation of Stability and In Vitro Bioaccessibility

Inadequate intake of lutein is relevant to a higher risk of age-related eye diseases. However, lutein has been barely incorporated into foods efficiently because it is prone to degradation and is poorly bioaccessible in the gastrointestinal tract. Microfluidics, a novel food processing technology that can control fluid flows at the microscale, can enable the efficient encapsulation of bioactive compounds by fabricating suitable delivery structures. Hence, the present study aimed to evaluate the stability and the bioaccessibility of lutein that is encapsulated in a new noodle-like product made via microfluidic technology. Two types of oils (safflower oil (SO) and olive oil (OL)) were selected as a delivery vehicle for lutein, and two customized microfluidic devices (co-flow and combination-flow) were used. Lutein encapsulation was created by the following: (i) co-flow + SO, (ii) co-flow + OL, (iii) combination-flow + SO, and (iv) combination-flow + OL. The initial encapsulation of lutein in the noodle-like product was achieved at 86.0 ± 2.7%. Although lutein’s stability experienced a decreasing trend, the retention of lutein was maintained above 60% for up to seven days of storage. The two types of device did not result in a difference in lutein bioaccessibility (co-flow: 3.1 ± 0.5%; combination-flow: 3.6 ± 0.6%) and SO and OL also showed no difference in lutein bioaccessibility (SO: 3.4 ± 0.8%; OL: 3.3 ± 0.4%). These results suggest that the types of oil and device do not affect the lutein bioaccessibility. Findings from this study may provide scientific insights into emulsion-based delivery systems that employ microfluidics for the encapsulation of bioactive compounds into foods.

Systematic Evaluation of a Novel Self-Healing Poly(acrylamide-co-vinyl acetate)/Alginate Polymer Gel for Fluid Flow Control in High Temperature and High Salinity Reservoirs.

Preferential fluid flow often occurs when water and CO2 is injected into mature oilfields, significantly reducing their injection efficiency. Particle gels have been evaluated and applied to control the short circulation problems. This study systematically investigated a novel poly(acrylamide-co-vinyl acetate)/alginate-based interpenetrated gel system (Alg-IPNG) which is designed to control the preferential fluid flow problems in high-temperature reservoirs. Chromium acetate was incorporated into the gel system to provide the delayed crosslinking feature of the particle gels. The alginate polymer system can also take advantage of the Ca2+ ions in the formation water, which exist in most reservoirs, to reinforce its strength by capturing the Ca2+ to form Ca–alginate bonds. In this paper, various characterizations for the Alg-IPNGs before and after the self-healing process were introduced: (1) the elastic modulus is set at up to 1890 Pa, and (2) the water uptake ratio is set at up to 20. In addition, we also discuss their possible self-healing and reinforcement mechanisms. In particular, the self-healing starting time of the Alg-IPNG particles are modified between 38 to 60 h, which is related to the water uptake ratio, Ca2+ concentration, and temperature. The reinforced Alg-IPNG gel has an enhanced thermal stability (180 days) at the temperature up to 110 °C.

Simulation-enabled Design and Analysis of Globe Valve

Globe valves serve many purposes in oil and gas facilities as a tool to control fluid flow in pipelines. However, older designs of globe valves suffer many problems and faults, mainly from valve leakage and valve passing. In mitigating these problems, this paper will improve the design of a globe valve to enhance its fluid flow performance and reduce the pressure difference value throughout the valve. The improvements on the valve will be validated from the original design with the help of Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA). The project concluded that the improved valve design performs better than the original design in all aspects except in terms of valve passing at the contact seal between the seat and the disk in a fully closed position. Implementation of smart sensors and prototyping will be explored in future studies.

Unsteady radiative nanofluid flow near a vertical heated wavy surface with temperature-dependent viscosity

In the present contribution, a numerical treatment is provided to describe unsteady nanofluid flow near a vertical heated wavy surface. A memorable feature of the present work is the investigation of nanofluid flow associated with thermal radiation that acts as a catalyst for heat transfer rates. Likewise, the effectiveness of variable viscosity is examined as it controls fluid flow as well as heat transfer. It is necessary to study heat and mass transfer for complex geometries because predicting heat and mass transfer for irregular surfaces is a topic of fundamental importance, and irregular surfaces frequently appear in many applications, such as flat-plate solar collectors and flat-plate condensers in refrigerators. A simple coordinate transformation from the wavy surface into a flat one is employed. The non-dimensional boundary layer equations that governing both heat transfer and nanofluid flow phenomena along the wavy surface are solved via a powerful numerical approach called the implicit Chebyshev pseudospectral (ICPS) method with Mathematica code. A comparison graph of the current numerical computation and the published data shows a perfect match. Figures depict the effect of various physical parameters on nanofluid velocities, temperature, salt concentration, nanoparticle concentration, skin friction, Sherwood, nanoparticle Sherwood, and Nusselt numbers. According to the numerical results, increasing the variable viscosity parameter value causes a drop in the local skin friction coefficient value and an increase in the steady-state axial nanofluid velocity profile near the wavy surface. Furthermore, as heat radiation is increased, the local Nusselt number decreases but the nanoparticle Sherwood number increases.

Flow Rate Control by Means of Flow Meter and PLC Controller.

This paper presents a design of a flow meter based on a programmable logic controller (PLC). The new construction of a flow meter controlled by PLC increases the possibilities for the control and automation of fluid flow. Additionally, the didactic potential of the use of simple automation in the form of a programmable logic controller was considered. A device enabling the measurement of fluid flow rate based on a PLC controller was designed, constructed, and tested. The choice of device was the Gems Sensors FT-210 series turbine flow sensor, which is characterized by low purchase and maintenance costs. The properties and the chemical resistance of polyamide-12, the material the sensor is made of, make it possible to test the flow of various types of fluids. As part of the work, an algorithm and a program controlling the device was developed based on the APB Soft software, enabling the accurate reading of the number of impulses sent by the turbine flow sensor. The results of the designed flow meter were compared with the results obtained for the Krohne VA-40 high accuracy rotameter.

Lithographically patterned micro-nozzles for controlling fluid flow profiles for drug delivery and in vitro imaging applications.

Precisely controlling delivery of drugs and other reagents is important for intravital microscopy studies. In this work, photolithographic integration of micro-nozzles onto a microfluidic platform was performed to tune the fluid flow profile and depth of penetration into biological tissue mimics. Performance characteristics were measured by correlating the flow rate through the device to the applied pressure and/or delivery of dyes into solution and agarose gel-based phantom tissue. From these results, the implementation of micro-nozzles was demonstrated to significantly improve the lateral dispersion of delivered fluid and increase the depth of penetration into phantom tissue.

Mapping Hydrothermal Alteration at the Fentale-Dofan Magmatic Segment of the Main Ethiopian Rift

The Main Ethiopian Rift (MER) is characterized by extensional tectonics and volcanism, associated with active hydrothermal systems, hydrothermal alteration and fumarolic deposits. The spatial distribution of these hydrothermal products and their link with faults and rock types provides important clues to what controls fluid flow in the subsurface. However, little is known about this in the East African Rift. We address this issue with a multidisciplinary approach in the Fentale-Dofan magmatic segment of the MER, an area characterized by intense volcanic and tectonic activity and a geothermal prospect. Primarily we conduct mapping of hydrothermal alteration and fumarolic deposits, and rock lithologies using a surface feature classification technique of multispectral satellite images. Then we interpret the map using a new database of faults and active hydrothermal manifestations such as hot-springs and fumaroles. We find that the surface hydrothermal alteration and deposits are mainly focused near Fentale and the Dofan Volcanic Complex (DVC). At DVC the hydrothermal products are focused on rhyolites on the western side of the volcano, in an area of intense NNE striking, rift parallel faults. At Fentale volcano the hydrothermal products are mainly associated with ignimbrite and show a circular pattern around the volcanic edifice, but also in places follow the NNE striking faults. At Fentale, the more complex association of hydrothermal products and active manifestations around the edge of the ignimbrite suggests formation contacts may also localize fluid flow in places. At both volcanoes the association between hydrothermal products with either the rhyolites and ignimbrites is likely due to them being relatively easily altered (in comparison to basalt), and also their brittle nature allows for fracturing through which localized fluid flow can occur (as opposed to the sediments). The general pattern of hydrothermal products suggests a stronger structural influence at the DVC with respect to Fentale. The presence of hydrothermal products and active hydrothermal manifestations, along with other lines of evidence such as locus of subsurface dike intrusion at the volcanic centres, suggest that discrete and localized magma reservoirs beneath Fentale and the DVC are the heat source for hydrothermal circulation. Our study also demonstrates that geology, including hydrothermal deposits, can be successfully mapped using automated remote sensing based classification.