Unique Flow Research Articles

Classification between Normal and Cancerous Human Urothelial Cells by Using Micro-Dimensional Electrochemical Impedance Spectroscopy Combined with Machine Learning.

Although the high incidence and recurrence rates of urothelial cancer of the bladder (UCB) are heavy burdens, a noninvasive tool for effectively detecting UCB as an alternative to voided urine cytology, which has low sensitivity, is yet to be reported. Herein, we propose an intelligent discrimination method between normal (SV-HUC-1) and cancerous (TCCSUP) urothelial cells by using a combination of micro-dimensional electrochemical impedance spectroscopy (µEIS) with machine learning (ML) for a noninvasive and high-accuracy UCB diagnostic tool. We developed a unique valved flow cytometry, equipped with a pneumatic valve to increase sensitivity without cell clogging. Since contact between a cell and electrodes is tight with a high volume fraction, the electric field can be effectively confined to the cell. This enables the proposed sensor to highly discriminate different cell types at frequencies of 10, 50, 100, 500 kHz, and 1 MHz. A total of 236 impedance spectra were applied to six ML models, and systematic comparisons of the ML models were carried out. The hyperparameters were estimated by conducting a grid search or Bayesian optimization. Among the ML models, random forest strongly discriminated between SV-HUC-1 and TCCSUP, with an accuracy of 91.7%, sensitivity of 92.9%, precision of 92.9%, specificity of 90%, and F1-score of 93.8%.

Improved Laplacian Matrix based power flow solver for DC distribution networks

Distribution networks feature distinct topologies than transmission networks, such as radial or weakly meshed structures with tens of thousands of nodes. They have more points of power injection owing to the integration of distributed generators and high R/X ratios. Furthermore, there has recently been a surge of interest in DC distribution networks. In the planning and operation of modern distribution systems, load flow needs to be executed in series considering short intervals of time in the order of minutes or even less. Hence, these networks require a load flow solver that can converge fast with low computational burden. In this paper, we propose a unique iterative power flow solver based on graph theory for DC distribution networks. The proposed formulation is flexible and can handle both radial and mesh configurations with just one connectivity matrix. To validate the proposed method, we used the IEEE 33 bus test feeder and compared the results with an existing methodology. Results suggest that the proposed method is robust and possesses fast convergence.

Axial conduction in cross-flow heat exchangers: An analytical approach to the coupled heat transfer problem

Cross-flow heat exchangers are widely used in the process intensification and air separation industry. Its miniaturized versions are touted to be especially useful for aircraft heat exchange, portable cooling systems, and micro-combustion chambers for fuel cells. The desired thermal effect is often obtained in a cross-flow heat exchanger of a shorter length leading to a lower pressure drop penalty. Although miniaturization leads to high heat transfer to volume ratio, the low flow rates and large solid cross-section area to fluid free-flow area ratio might lead to intense axial conduction. Standard mathematical models for macro-scale exchangers neglect this effect and must be modified for micro-scale applications. While the analytical models are available for the counter-current exchanger, a similar analytical tool is missing for the cross-flow device. The present work attempts to develop such a tool, wherein, unlike previous attempts, a three-dimensional modelling approach is undertaken. The unique flow configuration in the cross-flow system necessitates this modification if both axial conduction and thermal resistance of the separating wall (missing in earlier two-dimensional attempts) are to be simultaneously tackled. The developed model can handle both balanced and unbalanced flows. Validations have been performed using conjugate computational studies (with exact geometry and solved in COMSOL), a simplified numerical model, and by comparison with some of the standard cross-flow expressions in the limit of no axial conduction. Results are presented in the form of three-dimensional temperature profiles, effectiveness-NTU (number of transfer units), and conduction effect factor curves for different flow and geometric configurations. It is found that the balanced cross-flow exchanger can experience performance deterioration of ∼45% at low flow rates. The fast convergence of the proposed theory allows it to be nested in heat exchanger optimization routines, where a detailed computational step would have led to prohibitive computational costs.

AN EXTENSIVE INVESTIGATION OF FLOW CONDITIONERS INSIDE A FI-FI MONITOR

As it is known, to provide fire protection for any type of surface vessel, external fire-fighting (EFF) systems have been commonly used for decades as well as in coastal regions. These types of systems exist on several types of vessels such as fire-fighting ships, tugboats, supply vessels and naval vessels. Flow conditioners can be used in the EFF systems to provide better performance by regulating the flow inside the fi-fi monitor. In the present study, a fire-fighting (fi-fi) monitor was designed and different flow conditioners were implemented into the fi-fi monitor. A unique flow conditioner was designed in addition to the recommended ones by ISO 5167-3 in order to improve the performance of the flow conditioner in terms of head ratio and flow rate. A commercial computational fluid dynamics (CFD) solver was used to investigate the performance of the different flow conditioners. Before comparing the numerical results of different flow conditioners, the numerical model was validated with the experimental data and verified with appropriate methods. The results showed that the unique flow conditioner successfully regulates the streamlines and it has better performance than the recommended ones by ISO 5167-3 in terms of flow rate and head ratio. As the last part of the study, the effect of unique flow conditioner length was investigated and the best length was determined.

Numerical study on novel airfoil corrugated plate heat exchanger: A comparison with commercial type and geometrical parameter analysis

• Symmetric airfoil is used for PHE design for the first time. • CFD simulation is validated with a previous experimental. • New type of PHE has less pressure drop than commercial type while maintaining the same amount of heat transfer. • Effects of geometrical parameters of plate heat exchanger on performance was numerically studied. • Airfoil PHE is a potential alternative to commercial type. Utilizing an effective corrugation shape in plate heat exchanger (PHE) results in a substantial increase in thermal performance and a more compact design for these devices. This article presents, for the first time in the literature, an innovative PHE design that employs symmetric airfoil profile corrugation (airfoil corrugated PHE). As a consequence of the airfoil corrugation, unique flow channel is formed inside the PHE, which results in lower pressure drop while maintaining the equivalent heat transfer rate as the commonly used commercial sinusoidal PHE. In order to get a comprehensive understanding of the performance of airfoil corrugated PHE, essential parameters such as corrugated angle, corrugated pitch, mirror arrangement, and airfoil profile were examined over Reynolds number ranges of 4,600–8,400. Compared to sinusoidal corrugation, the innovative PHE has roughly 17% reduced pressure drop while keeping the same amount of heat transfer, as determined by a computational analysis of thermal and hydraulic parameters. 60° was the optimal corrugated angle, demonstrating a 10% increase in overall heat transfer coefficient (OHTC) compared to both 30° and 90°. In addition, the NACA 0030 airfoil profile obtained the highest thermal performance, with an OHTC that was roughly 12% greater than that of the NACA 0020 and NACA 0025 profiles. Nonetheless, as one of the geometrical parameters changes, the pressure drop is proportionate to the increase in heat transfer. NACA 0030 saw a pressure drop increase of around 33.7%, the greatest of any case. The geometrical parametric study indicates that the ideal configuration of the innovative PHE consists of NACA 0030 airfoil profile, chevron angle of 60° degrees, single mirror arrangement, and corrugated pitch of 3.14 mm, as shown by the maximum performance of evaluation criterion (PEC) value of 1.08.

Multiphase flow and geomechanical responses of interbedded hydrate reservoirs during depressurization gas production for deepwater environment

The coupled multiphase flow and geomechanical responses are very important considerations in planning offshore hydrate production. In this work, a novel thermo-hydro-mechanical (THM) coupled simulator has been developed to investigate the THM responses of interbedded hydrate reservoirs using depressurization method in the offshore India. Based on the detailed geological data at the NGHP-02-16 site, a more realistic hydrate reservoir model is constructed to analyze the unique multiphase flow and geomechanical responses induced by depressurization. The results indicate that the average gas production rate of this work is 6370 ST m3/d, which is significantly lower than the previous numerical result of about 9000 ST m3/d using the same 3 MPa production pressure. This is mainly because the geomechanical response gives negative feedback to flow through the stress-dependent porosity and permeability. The reservoir heterogeneity results in the non-uniform hydrate dissociation and effective stress changes in the marine sediments. The depressurization results in significant increase of shear stress and vertical compaction in the hydrate reservoir. The maximum shear stress is no more than 2 MPa and is mainly concentrated in the top and bottom regions of the production interval. The maximum seafloor subsidence is 1.15 m during 100 days depressurization test. Sensitivity analysis results suggest that the production pressure and perforation length are two important parameters affect the gas productivity and mechanical stability. The low production pressure is recommended under the premise of mechanical stability for gas production from hydrate reservoirs. Perforation in the underlying water-saturated sand layer will lead to more serious water production and seafloor subsidence. The coupled multiphase flow and geomechanical results presented in this work are helpful to design the safe hydrate production scheme in the future.

The Rate of $${\mathbb {F}}$$-convergence for Ricci Flows with Closed and Smooth Tangent Flows

This article is a continuation of Chan et al. ( http://arxiv.org/abs/2109.14763 , 2021), where we proved that a Ricci flow with a closed and smooth tangent flow has unique tangent flow, and its corresponding forward or backward modified Ricci flow converges at the rate of $$t^{-\beta }$$ for some $$\beta >0$$ . In this article, we calculate the corresponding $${\mathbb {F}}$$ -convergence rate: after being scaled by a factor $$\lambda >0$$ , a Ricci flow with closed and smooth tangent flow is $$|\log \lambda |^{-\theta }$$ close to its tangent flow in the $${\mathbb {F}}$$ -sense, where $$\theta $$ is a positive number, $$\lambda \gg 1$$ in the blow-up case, and $$\lambda \ll 1$$ in the blow-down case.

Application of a Gas-Kinetic BGK Scheme in Thermal Protection System Analysis for Hypersonic Vehicles

One major problem in the development of hypersonic vehicles is severe aerodynamic heating; thus, the implementation of a thermal protection system is required. A numerical investigation on the reduction of aerodynamic heating using different thermal protection systems is conducted using a novel gas-kinetic BGK scheme. This method adopts a different solution strategy from the conventional computational fluid dynamics technique, and has shown a lot of benefits in the simulation of hypersonic flows. To be specific, it is established based on solving the Boltzmann equation, and the obtained gas distribution function is used to reconstruct the macroscopic solution of the flow field. Within the finite volume framework, the present BGK scheme is specially designed for the evaluation of numerical fluxes across the cell interface. Two typical thermal protection systems are investigated by using spikes and opposing jets, separately. Both their effectiveness and mechanisms to protect the body surface from heating are analyzed. The predicted distributions of pressure and heat flux, and the unique flow characteristics brought by spikes of different shapes or opposing jets of different total pressure ratios all verify the reliability and accuracy of the BGK scheme in the thermal protection system analysis.

Numerical Investigation on Mixing Characteristics and Mechanism of Natural Gas/Air in a Super-Large-Bore Dual-Fuel Marine Engine

Premixed combustion mode dual-fuel (DF) engines are widely used in large-bore marine engines due to their great potential to solve the problem of CO2 emissions. However, detonation is one of the main problems in the development of marine engines based on the premixed combustion mode, which affects the popularization of liquefied natural gas (LNG) engines. Due to the large bore and long stroke, marine dual-fuel engines have unique flow characteristics and a mixture mechanism of natural gas and air. Therefore, the purpose of this study is to present a simulated investigation on the influence of swirl on multiscale mixing and the concentration field, which provides a new supplement for mass transfer theory and engineering applications. It is suggested that the phenomenon of abnormal combustion occurs on account of the distribution of the mixture being uneven in a super-large-bore dual-fuel engine. Further analysis showed that the level of swirl at the late compression stage and the turbulence intensity are the decisive factors affecting the transmission process of natural gas (NG) and distribution of methane (CH4) concentration. Finally, a strategy of improving mixture quality and the distribution of the mixture was proposed.

Oscillations for active sensing in olfaction: bioinspiration from insect antennal movements

Crustacean and insect antennal scanning movements have been postulated to increase odorant capture but the exact mechanisms as well as measures of efficiency are wanting. The aim of this work is to test the hypothesis that an increase in oscillation frequency of a simplified insect antenna model translates to an increase of odorant capture, and to quantify by how much and through which mechanism. We approximate the antennal movements of bumblebees, quantified in a previous study, by a vertical oscillatory movement of a cylinder in a homogeneous horizontal flow with odorants. We test our multiphysics flow and mass transfer numerical model with dedicated experiments using particle image velocimetry. A new entire translating experimental measurement setup containing an oil tank enables us to work at appropriate Strouhal and Reynolds numbers. Increasing antennal oscillating frequency does increase the odorant capture rate, up to 200%, proving this behavior being active sensing. This result holds however only up to a critical frequency. A decrease of efficiency characterizes higher frequencies, due to molecules depletion within oversampled regions, themselves defined by overlaying boundary layers. Despite decades of work on thermal and mass transfer studies on oscillating cylinders, no analogy with published cases was found. This is due to the unique flow regimes studied here, resulting from the combination of organ small size and low frequencies of oscillations. A theory for such flow regimes is thus to be developed, with applications to fundamental research on animal perception up to bioinspired olfaction.

Effects of Loading Level on the Variation of Flow Losses in Subsonic Axial Compressors

The development of the aircraft industry seeks an increase in compressor loading, bringing unique flow phenomena and design problems; thus, insights into the ultrahigh loaded compressor are in great need. To reveal the loss characteristics of the ultrahigh loaded subsonic axial compressors, four well comparable compressor stages are carefully designed with the loading coefficient varying from 0.41 to 0.65. A novel flow-based loss decomposition method is performed to investigate the variation of different kinds of losses (including blade profile loss, tip leakage loss, casing endwall loss, and hub endwall loss) with the change in compressor loading level and operating condition. Results show that the blade profile loss always occupies the largest part of the total loss. In rotor passages, the percentage of the blade profile loss at the design point is increased from 69% to 76% with the increase in the compressor loading. Meanwhile, the proportion of the tip leakage loss decreases as the loading increases. For a specific compressor stage, the total loss of the rotor passage tends to increase with the increase in stage pressure rise coefficient along the operation line, whereas the proportion of the blade profile loss is squeezed by the tip leakage loss. As for stator passages, the proportion of blade profile loss to the total passage loss is nearly constant along the compressor operating line, but increases from 79% to 90% with the increase in the compressor loading level. By correlating the losses with blade solidity, it was found that the increase in flow losses in the highly loaded compressor, i.e., the decrease in efficiency, stems mainly from the high blade solidity.

Flow Performance and Its Effect on Shape Formation in PDMS Assisted Thermal Reflow Process

A theoretical model is proposed to investigate the mechanism of shape formation in polydimethylsiloxane (PDMS) assisted thermal reflow. The thermal curing of PDMS is characterized by a dual-Arrhenius equation and its effect on the reflow process is discussed. It shows that due to the thermal curing of PDMS, the dynamic wetting and interface evolution are constrained successively. This is quite different from the traditional thermal reflow, and will result in unique flow performance, which will facilitate the abilities of the base constraint and shape retaining for the thermal reflow process. These advantages are critical to obtain well-defined microstructures in a simple and controllable way. Theoretical simulations of shape formation are in good agreement with the experimental results. These results provide a comprehensive understanding on PDMS assisted thermal reflow and offer a theoretical guideline for a facile yet versatile fabrication method for high quality microstructures.

Optical cloaking of macroscopic objects by geometric-phase vortex processing

We report on free-space strategy for electromagnetic concealment of three-dimensional macroscopic objects in the optical domain owing to unique energy flow redirection capabilities enabled by optical phase singularities. We propose and implement the generation of a quasi-nodal volume based on optical vortex Fourier processing, which inhibits light scattering from objects placed inside. The proof of concept is made by numerical simulations and the experimental implementation is carried out in the visible domain by using geometric phase vortex phase masks. Optical cloaking demonstration is made by using stainless steel sphere as the object to be concealed. The geometric phase nature of the vortex masks confers polarization independent features to the device and makes it possible to implement in a reflection mode.

Existence of multiple solutions for magnetohydrodynamic flows of second-grade and Walter’s B fluids due continuously contracting flat sheet with partial slip

In the present investigation, an attempt is performed to analyse the existence of multiple exact solutions for magnetohydrodynamic flows of second-grade and Walter’s B fluids due continuously contracting flat sheet with partial slip condition at the boundary. After transforming basic governing equations by suitable similarity transformations, single and double closed-form exact solutions of the flow are achieved on certain restrictions on flow variables of two aforesaid fluids. The impacts of magnetic field and partial slip on existence and non-existence of solutions are revealed. The changes of flow surface drag and velocity with various involved parametric values are also explored. For both viscoelastic type fluids, i.e., second-grade and Walter’s B fluids, double solutions exist for certain flow conditions. In second-grade case, if viscoelastic parameter exceeds a definite value, then double similarity solutions are achieved for any type of flow, i.e., slip flow or no-slip flow. For Walter’s B fluid similar results are obtained with unique similarity slip flow solution if magnitude of viscoelastic parameter exceeds certain fixed value. Importantly, the magnetic field and its MHD effect stabilize the uncertainty situation in existence of similarity solution for both fluids and produce unique solution for a suitable choice.

Measuring the red blood cell shape in capillary flow using spectrally encoded flow cytometry.

Red blood cells in small capillaries exhibit a wide variety of deformations that reflect their true physiological conditions at these important locations. By applying a technique for the high-speed microscopy of flowing cells, termed spectrally encoded flow cytometry (SEFC), we image the light reflected from the red blood cells in human capillaries, and propose an analytical slipper-like model for the cell morphology that can reproduce the experimental in vivo images. The results of this work would be useful for studying the unique flow conditions in these vessels, and for extracting useful clinical parameters that reflect the true physiology of the blood cells in situ.

Vertical C-Shaped-Channel Nanosheet FETs Featured With Precise Control of Both Channel-Thickness and Gate-Length

A novel vertical C-shaped-channel nanosheet field-effect-transistor (VCNFET) featured with precise control of channel-thickness and gate-length, and a unique integration flow of Dual Side Process (DSP) are proposed in this work. The VCNFETs were fabricated by high quality Si/SiGe epitaxy, atomic layer etching with nanometer-scale process control and self-aligned high-k metal gate (HKMG). The integration flow is compatible with mainstream CMOS technology. Thanks to the precise control of channel thickness and doping profiles, perfect SS of 61 mV/dec, small DIBL of 8 mV/V, and remarkably large <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{I}_{\text {on}}/\text {I}_{\text {off}}$ </tex-math></inline-formula> ratio of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${6.28}\times {10}^{{9}}$ </tex-math></inline-formula> were achieved. The device performance and it’s optimization were also investigated with the reduction of the external resistance and numerical simulations.

Estimating Botnet Impact on IoT/IoE networks using Traffic flow Features

The Internet of Things (IoT) as well as Internet of Everything (IoE) services and applications have contributed to the proliferation of web-enabled information technologies. Massive amounts of data and the pervasiveness of the IoT and IoE networks attract botnet attackers. IoT security is indispensable. In order to detect botnet attacks and to estimate their impact on IoT and IoE networks, a set of unique traffic flow features has been presented in this manuscript that is referred to as BIE-TFF (Botnet Impact Estimation using Traffic Flow Features). BIE-TFF developed a lightweight machine learning technique based on traffic flow characteristics that were extracted. In order to determine the pivot confidence of the traffic flow features, the BIE-TFF buffers the traffic flow of a time capsule coefficient during the prediction phase, which is then compared with the pivot confidence of traffic flow characteristics identified during the training phase to determine the severity of the botnet attack. BIE-TFF has achieved the highest decision accuracy with the maximum sensitivity and specificity to predict the scope of early-stage botnet attacks and their impact. The results of the experimental study also indicate that the detection performance of a BIE-TFF-enabled edge gateway remains constant as the number of connections at an IOE-enabled edge gateway increases. Experimentally, BIE-TFF outperformed existing prediction and detection algorithms for botnet attacks.

Reservoir Characterization of Lower Qamchuqa (Shu'aiba) Formation from the Well BH-86, Bai- Hassan Oil field, Northern Iraq

The reservoir characterization of Lower Qamchuqa (Shu'aiba) Formation (Aptian) is studied at the well BH-86 of Bai- Hassan Oilfield in Kirkuk area, Northern Iraq. The lithological study (of 91 thin sections) revealed that the formation consists of shaly limestone, a thin bed of marl within the limestone, and dolomitic limestone. Four petrographic microfacies were noticed Lime mudstone microfacies, Dolomudstone microfacies, Lime wackestone microfacies, subdivided into benthonic foraminifera lime wackestone submicrofacies and bioclasts lime wackestone submicrofacies, and the last microfacies is the Lime packstone microfacies, which is subdivided into pelloidal lime packstone submicrofacies and Orbitolina lime packstone microfacies. Shale content is calculated from the gamma-ry log, showing that the formation is mainly of low shale content (less than 35%). The porosity determined from sonic, density, and neutron logs reflect that the range between &lt;1 and 15% and in some intervals about 6% is secondary porosity type. The estimated permeability ranges between &lt;0.01 and 2.0mD, reflecting low permeability. The formation is subdivided into six reservoir units according to the shale content, average porosity, and permeability. The unit RU-5 has the best reservoir properties among the identified units with an average shale content of about 3.15%, about 6.2% porosity, and about 1.75mD average permeability. On the other hand, the least reservoir property is noticed in the unit RU-1 with average 9.48% shale content, 3.64% porosity, and 0.5mD average permeability. The research indicates that the fractures contribute to the flow within the Lower Qamchuqa Formation. Fluids flow through the formation in four unique Hydraulic Flow Units (HFU). Only about 8% of the gross 146m of the formation is expected to have the required reservoir properties for oil production and about 68% for gas production. The actual productive thickness for oil is only about 2.8% of the gross thickness of the studied section, and it’s more than 50% of the gross thickness for gas.

Speaker-wire vortices in stratified anabatic Prandtl slope flows and their secondary instabilities

Stationary longitudinal vortical rolls emerge in katabatic and anabatic Prandtl slope flows at shallow slopes as a result of an instability when the imposed surface buoyancy flux relative to the background stratification is sufficiently large. Here, we identify the self-pairing of these longitudinal rolls as a unique flow structure. The topology of the counter-rotating vortex pair bears a striking resemblance to speaker-wires and their interaction with each other is a precursor to further destabilization and breakdown of the flow field into smaller structures. On its own, a speaker-wire vortex retains its unique topology without any vortex reconnection or breakup. For a fixed slope angle $\alpha =3^{\circ }$ and at a constant Prandtl number, we analyse the saturated state of speaker-wire vortices and perform a bi-global linear stability analysis based on their stationary state. We establish the existence of both fundamental and subharmonic secondary instabilities depending on the circulation and transverse wavelength of the base state of speaker-wire vortices. The dominance of subharmonic modes relative to the fundamental mode helps to explain the relative stability of a single vortex pair compared to the vortex dynamics in the presence of two or an even number of pairs. These instability modes are essential for the bending and merging of multiple speaker-wire vortices, which break up and lead to more dynamically unstable states, eventually paving the way for transition towards turbulence. This process is demonstrated via three-dimensional flow simulations with which we are able to track the nonlinear temporal evolution of these instabilities.

Optimal design of the field hydrate production test in the offshore India: Insights from the vertically heterogeneous hydrate reservoir model

Recently, the hydrate-bearing sand reservoirs were founded with high saturation in the offshore India by the National Gas Hydrate Program Expedition 02 (NGHP-02). Based on the detailed geological data at the NGHP-02-16 site, a more realistic reservoir model is constructed to analyze the unique multiphase flow and hydrate phase change behaviors from the geologically descriptive hydrate reservoirs. The main goals of this work are to optimize the adjustable production parameters and to predict the long-term gas production performance for guiding the upcoming field hydrate production test in India. The results indicate that gas production rates increase, but water production rates decrease slowly with time from the heterogeneous hydrate-reservoir. This is completely different from the previous prediction of multiphase flow behavior based on homogeneous hydrate-reservoir models. A non-uniform hydrate dissociation front is formed in the hydrate-reservoir due to the reservoir heterogeneity promote the horizontal dissociation of solid-hydrate within the high permeability sand layers. The maximum distance of free gas zone expands to outside more than 500 m from the production well. This indicates that the field fault system should be carefully concerned during the long-term production. Sensitivity analysis results suggest that the complete perforation in the hydrate-bearing layer and the underlying water saturated layer is beneficial for improving the hydrate production performance. Over the 5 years depressurization, a total of 2.08 × 107 ST m3 methane gas can be produced using the recommended well placement. The average gas-to-water ratio and energy ratio reach 10.22 ST m3 CH4/m3 H2O and 30.14, respectively, showing a high gas production potential from this hydrate site.