Flow Components Research Articles

Analysis of the Energy Loss Mechanism of Pump-Turbines with Splitter Blades under Different Characteristic Heads

The operating efficiency of high-head pump turbines is closely related to the internal hydraulic losses within the system. Conventional methods for calculating hydraulic losses based on pressure differences often lack detailed information on their distribution and specific sources. Additionally, the presence of splitter blades further complicates the hydraulic loss characteristics, necessitating further study. In this study, Reynolds-averaged Navier–Stokes (RANS) simulations were employed to analyze the performance of a pump turbine with splitter blades at three different head conditions and a guide vane opening (GVO) of 10°. The numerical simulations were validated by experimental tests using laser doppler velocimetry (LDV). Quantitative analysis of flow components and hydraulic losses was conducted using entropy production theory in combination with an examination of flow field distributions to identify the origins and features of hydraulic losses. The results indicate that higher heads are associated with lower growth rates of total hydraulic losses. In particular, the significant velocity gradients at the trailing edge of the splitter blades contribute to higher hydraulic losses. Furthermore, the hydraulic losses in the runner (RN) region are predominantly influenced by velocity gradients and not by vortices, with the flow conditions in the RN region impacting the hydraulic losses in the draft tube (DT).

Reducing impacts of artificial ponding in modeling salt marshes using a conductivity-formulated subgrid model

The landforms of salt marsh systems are rather complex, with meandering channel networks cutting through low-lying, extensive marsh platforms. Some small-scale topographic details are critical to flooding and draining processes but cannot be reflected in the Digital Elevation Model (DEM) due to limited measurement resolution and vegetation bias. Numerical models need a grid with high enough resolution to capture the small-scale connectivity to correctly model the small-scale flow processes, making the model computationally unaffordable. In this study, we derived a subgrid model, which couples two flow components, one is the regular subgrid model for simulating the subgrid-resolved flows, and the other is a conductivity-formulated porous flow model for modeling small-scale gut flows unresolved at the subgrid level. The model validation was performed using an idealized case with a narrow slot that was unresolved in the coupled flow model. Model results were compared with a slot-resolved regular subgrid model where only surface flows are solved and suggested that, with a proper model parameterization, the coupled flow model is capable of reproducing flooding and draining processes similar to the slot-resolved subgrid model of surface flow. The model was applied to simulating flooding and draining processes in a meso-tidal salt marsh. The model results demonstrate that the coupled subgrid model can be used to reduce the impacts of artificial ponding that usually occur in numerical simulations of salt marshes with numerous narrow gullies and creeks.

Structure‐Aware Image Translation‐Based Long Future Prediction for Enhancement of Ground Robotic Vehicle Teleoperation

Predicting future frames through image‐to‐image translation and using these synthetically generated frames for high‐speed ground vehicle teleoperation is a new concept to address latency and enhance operational performance. In the immediate previous work, the image quality of the predicted frames was low and a lot of scene detail was lost. To preserve the structural details of objects and improve overall image quality in the predicted frames, several novel ideas are proposed herein. A filter has been designed to remove noise from dense optical flow components resulting from frame rate inconsistencies. The Pix2Pix base network has been modified and a structure‐aware SSIM‐based perpetual loss function has been implemented. A new dataset of 20 000 training input images and 2000 test input images with a 500 ms delay between the target and input frames has been created. Without any additional video transformation steps, the proposed improved model achieved PSNR of 23.1; SSIM of 0.65; and MS‐SSIM of 0.80, a substantial improvement over our previous work. A Fleiss’ kappa score of >0.40 (0.48 for the modified network and 0.46 for the perpetual loss function) proves the reliability of the model.

Techno-economic comparison of P2P energy sharing and residential battery storage in the photovoltaic community

ABSTRACT To quantify the techno-economic benefits of peer-to-peer (P2P) sharing and residential battery storage and clarify their inter-relationship, this study proposes four working modes for the PV community with P2P energy sharing and batteries as variables. Besides, the energy flow and electricity cost components are comprehensively quantified at the community and individual customer levels. The yearly simulation results indicate that the batteries and P2P sharing both can increase the community’s self-sufficiency rate (SSR) and self-consumption rate (SCR) by 70–80%. Regarding economics, installing batteries has little effect on average electricity cost (AEC) because of its high cost, while P2P sharing can reduce the AEC by 8.25%. P2P energy sharing combined with battery has the best techno-economicperformance, increasing the SSR and SCR by around 140% and reducing the AEC by 10%, thus is suggested as the optimal mode. In the combined mode, 15% less PV power is stored in batteries than in the only battery storage system, demonstrating that the energy storage role of batteries is not fully exploited. This is because P2P energy sharing is designed to use limited surplus PV power before battery charging. Therefore, the battery size can be reduced to save initial investment in the combined mode.

The propulsive effect generated by fast travelling-wave vibrations

A prototype problem for the propulsion arising from a spatially-dependent source is analysed asymptotically. Such driving is a phenomenon that, while fairly common in biological settings, is less well understood in mechanical and engineering contexts. If two parallel plates bound a fluid and the plates are free to translate relative to each other, recent calculations have shown that vibrations applied to one plate in the form of travelling waves may induce motion of the other. The degree of the propulsion obtained is a function of both the wavelength and the phase speed of the imposed vibrations and there seems to an optimal wavelength for which propulsion is greatest. In order to shed light on these observations, here we undertake a formal asymptotic analysis of the process in the circumstance when the vibrations move quickly. It is shown how the flow structure takes on a form consisting of a bulk core layer supplemented by suitable edge layers attached to the two plates. The efficiency of the mechanism relies on the generation of a mean flow component whose properties are considered. It is found that there is excellent agreement between our analytical predictions and the previous simulations; in particular we are able to find the critical wavelength for maximum propulsion and explain the modifications that arise in the short and long wavelength limits.

The inverse problem of permeability identification for multiphase flow in porous media

Estimating permeability heterogeneity is a key component in modeling multiphase flow in geological porous media such as aquifers and reservoirs. The inverse problem of identifying permeability has been thoroughly studied regarding single-phase flow, however, hardly in two-phase flow problems. In this work, we study the inverse problem of estimating the spatial distribution of permeability in two-phase flow, considering a known saturation distribution, and using an iterative method based on inverting the capillary pressure–permeability relationship. The method is evaluated considering many different problem parameters and shown to be accurate for many cases in both oil–water and CO2–water three-dimensional systems. Large errors are observed when there is significant water trapping due to capillary effects and when conditions are dominated by viscosity. A range of optimal parameters is determined in which the inverse method is most accurate. These parameters can be used in applications, for example, when designing coreflooding experiments for permeability estimation. The estimated permeability is then used to predict the saturation and pressure distributions of two-phase flow with different injection flow rates and fluid fractions. The models are shown to be accurate when permeability estimations are accurate. The results support the possibility of calibrating a numerical model to coreflooding experiments and then using it to replace additional experiments, e.g., for evaluating flow rate effects.

Causal interaction in high frequency turbulence at the biosphere-atmosphere interface: Structure-function coupling.

At the biosphere-atmosphere interface, nonlinear interdependencies among components of an ecohydrological complex system can be inferred using multivariate high frequency time series observations. Information flow among these interacting variables allows us to represent the causal dependencies in the form of a directed acyclic graph (DAG). We use high frequency multivariate data at 10 Hz from an eddy covariance instrument located at 25 m above agricultural land in the Midwestern US to quantify the evolutionary dynamics of this complex system using a sequence of DAGs by examining the structural dependency of information flow and the associated functional response. We investigate whether functional differences correspond to structural differences or if there are no functional variations despite the structural differences. We base our analysis on the hypothesis that causal dependencies are instigated through information flow, and the resulting interactions sustain the dynamics and its functionality. To test our hypothesis, we build upon causal structure analysis in the companion paper to characterize the information flow in similarly clustered DAGs from 3-min non-overlapping contiguous windows in the observational data. We characterize functionality as the nature of interactions as discerned through redundant, unique, and synergistic components of information flow. Through this analysis, we find that in turbulence at the biosphere-atmosphere interface, the variables that control the dynamic character of the atmosphere as well as the thermodynamics are driven by non-local conditions, while the scalar transport associated with CO2 and H2O is mainly driven by short-term local conditions.

Experimental and numerical study on the ejector containing condensable species in the secondary flow for PEM fuel cell applications

Phase transitions in two-phase ejectors have gained attention in various applications, including refrigeration, desalination, and fuel cell systems. The phase transition of condensable components in the primary flow significantly affects the ejector performance. However, studies on the phase transition of condensable species in the secondary flow are scarce. Consequently, this study aims to investigate two-phase flow characteristics of the ejector containing condensable species in the secondary flow. A schlieren experimental system with a visual rectangular ejector was constructed, and a transient Eulerian-Lagrangian two-phase flow model incorporating non-equilibrium condensation was developed. The numerical simulations achieved an average deviation of 4.7% in the entrainment ratio compared to experimental measurements, with a maximum deviation of 11.6%. The schlieren experiment revealed that the condensable species in the secondary flow can condense when the primary pressure exceeds 0.30 MPa. The numerical results showed that the condensed droplets reach a minimum proximity of approximately 3 mm from the primary nozzle exit and exhibit a divergence angle ranging from 7° to 12° as they traverse with the gas flow. Additionally, increasing the primary flow pressure from 0.2 MPa to 0.5 MPa resulted in a noticeable lengthening of the first shock wave, from 1.45 mm to 3.00 mm.

Pengaruh Komponen Arus Kas dan Laba Kotor terhadap Harga Saham (Studi Kasus pada Perusahaan Manufaktur Sub Sektor Otomotif dan Komponen di Bursa Efek Indonesia Tahun 2013-2017)

The purpose of this study was to analyze the effect of cash flow components and gross profit on stock prices. The population in this study is the automotive sub-sector and components listed on the Indonesia Stock Exchange (IDX) in the 2013-2017 period. The sampling method used is the purpose sampling method with a sample of 8 companies for 5 consecutive years of observation so that the total sample is 40. The method of analysis in this study uses multiple linear regression. The results of this study indicate that operating cash flow and gross profit have no significant effect on stock prices. Meanwhile, investment cash flow and financing cash flow have a significant effect on stock prices. Meanwhile the cash flow components (operations, investment, funding and gross profit) have a simultaneous effect on stock prices.

The effect of intake port shape on in-cylinder flow field and turbulence distribution in a high-tumble production engine with endoscope accesses

Three cylinder heads with varied intake port shapes are experimentally investigated to evaluate intake flow structures and their influence on near top dead centre (TDC) flow fields and turbulence distributions in a motored high-tumble engine. The endoscopic high-speed particle image velocimetry (eHS-PIV) is implemented in multi-cylinder engines with two laser endoscopes and a camera endoscope installed in the cylinder head. For a range of engine load and speed conditions, particle seeded and laser illuminated high-speed movies are recorded for 100 cycles with which ensemble-averaged flow fields and spatial-filtered high-frequency flow magnitude distributions are analysed. The results show that a straighter intake port producing a more lateral flow direction results in a larger swinging arc, which is related to enhanced flow later in the compression stroke. The tumble vortex shows an asymmetric structure; the flow field during the compression stroke exhibits higher magnitude vectors at the leading head. This surging flow head becomes stronger with a straighter intake port, which leads to enhanced tumble vortex formation near TDC. As it becomes very strong, the flow vectors originally directed towards the exhaust valves bounce back towards the intake valves, causing a very complex flow structure involving multiple flow components. The result is enhanced turbulence throughout the late compression stroke including the spark timing. However, the impact of the straighter intake port shape on TDC turbulence becomes less significant at lower engine load and speed conditions as the lower intake air momentum limits the enhancement.

Chemical reaction-mass transport model of Ga2O3 grown by TEGa in MOCVD and an intelligent system

Gallium oxide (Ga2O3) is rationally expected to have a wide range of applications prospects in power electronics, solar-blind UV detectors, gas detectors, and other fields. Metal-organic chemical vapor deposition (MOCVD) is a key technology for achieving high-quality and large-scale film growth, but with complex fluid fields, temperature fields, component distribution, and chemical reaction processes, the process is akin to a black box. In this study, the computational fluid dynamics (CFD) approach and a complete reaction mechanism were used to model the chemical reaction and mass transport for gallium oxide film growth based on a vertical rotating disc reactor (RDR) MOCVD system. The effect of temperature on film growth was explored and analyzed. It was found that the growth temperature can be divided into four regions, respectively controlled by thermal flow field, reaction rate, component transport, and parasitic reaction, and there is a competitive relationship between them. In the component transport region, the influence of different process parameters such as pressure, flow rate, and rotational speed on the growth was investigated. The regulation of film uniformity is achieved by the coupled regulation of 5 pairs of MO source inlets and multiple process parameters. Combined with artificial intelligence techniques, an intelligent system for realizing flow field visualization, growth result prediction, process parameter optimization, and abnormal result tracking was proposed for the first time. It can provide systematic guidance for film growth.

A Blockchain Self-Sovereign Identity for Open Banking Secured by the Customer’s Banking Cards

Open finance is evolving and extending open banking. This creates a large context that implies a financial and identity data exchange paradigm, which faces challenges to balance customer experience, security, and the self-control over personal identity information. We propose Self-Sovereign Banking Identity (SSBI), a Blockchain-based self-sovereign identity (SSI) to secure private data sharing by utilizing trusted customer’s banking cards as a key storage and identity transaction-signing enclave. The design and implementation of the SSI framework is based on the Veramo SDK and Ethereum to overcome the limitation of signing curve availability on the current banking Java Cards needed for Hyperledger Indy. SSBI uses the elliptic curve SECP256K1 for transaction signing, which exists for several payment cards in the market. SSBI enables automated financial services and trust in the service provider communication. This work analyzes the flow and framework components, and evaluates the usability, integration, and performance in terms of throughput, latency, security, and complexity. Furthermore, the proposed approach is compared with related solutions. The presented prototype implementation is based on a test Ethereum network and signing transactions on the banking card. The preliminary results show that SSBI provides an effective solution for integrating the customer’s banking cards to secure open banking identity exchange. Furthermore, it allows the integration of several scenarios to support trusted open banking. The Blockchain layer settings need to be scaled and improved before real-world implementation.

Anisotropic biofouling behavior of sharkskin-patterned desalination membranes

Biofouling is a crucial issue in operating water treatment and desalination membranes because it deteriorates membrane performance. Topological tailoring of the membrane surface by implanting a biomimetic sharkskin (Sharklet) pattern has proven effective at mitigating biofouling. However, the anisotropic antibiofouling effect of the uniaxially aligned Sharklet-patterned membrane and its underlying mechanism remain unknown. Herein, the biofouling tendency of the Sharklet-patterned membrane was examined by gradually varying the angle between the pattern orientation and the bulk flow direction from 0° to 90°. The antibiofouling effect of the membrane was gradually enhanced as the pattern orientation angle increased. Computational simulation revealed that increasing the pattern orientation angle intensifies vortex flows and diverts local flows to a large extent while reducing the local flow parallel to the bulk flow; this flow change is hypothesized to effectively prevent foulant accumulation, consequently enhancing biofouling resistance. Furthermore, the observed anisotropic biofouling behavior was quantitatively interpreted using a microbial growth model. A larger pattern orientation angle attenuates the bulk flow component parallel to the pattern alignment, which critically suppresses the rate and extent of microbial growth, thereby mitigating biofouling. Our findings offer fundamental insights into the anisotropic antibiofouling mechanisms of uniaxially and/or biomimetically patterned membranes.

Application of invariance theory methods for measuring the flow rate of natural gas with excess hydrogen sulfide content

The paper presents an invariant method for measuring the flow rate of natural gas with an excess content of hydrogen sulfide, which is based on the principle of multichannelling of the invariance theory. The article describes the structure of the flow measurement system, which allows us to perform separate measurements of hydrogen sulfide flow rate and keep records of the amount of pure gas without hydrogen sulfide. The uncertainty of the flow rate measurement results for individual flow components is estimated. The factors that influence the accuracy of flow rate measurement are investigated, and the design features of the measurement system are discussed. The paper presents the results of experimental studies of the system on gas with excessive content of hydrogen sulfide and mercaptans.

Modeling Thermal Runaway of Lithium-Ion Batteries at Cell and Module Level Using Predictive Chemistry

<div>Thermal runaway of lithium (Li)-ion batteries is a serious concern for engineers developing battery packs for electric vehicles, energy storage, and various other applications due to the serious consequences associated with such an event. Understanding the causes of the onset and subsequent propagation of the thermal runaway phenomenon is an area of active research. It is well known that the thermal runaway phenomenon is triggered when the heat generation rate by chemical reactions within a cell exceeds the heat dissipation rate. Thermal runaway is usually initiated in one or a group of cells due to thermal, mechanical, and electrical abuse such as elevated temperature, crushing, nail penetration, or overcharging. The rate of propagation of thermal runaway to other cells in the battery pack depends on the pack design and thermal management system. Estimating the thermal runaway propagation rate is crucial for engineering safe battery packs and for developing safety testing protocols. Since experimentally evaluating different pack designs and thermal management strategies is both expensive and time consuming, physics-based models play a vital role in the engineering of safe battery packs. In this article, we present all the necessary background information needed for developing accurate thermal runaway models based on predictive chemistry. A framework that accommodates different types of chemical reactions that need to be modeled, such as solid electrolyte interphase (SEI) layer formation and decomposition, anode-solvent and cathode-solvent interactions, electrolyte decomposition, and separator melting, is developed. Additionally, the combustion of vent gas is also modeled. A validated chemistry model is used to develop a module-level model consisting of networks of pouch cells, flow, thermal, and control components, which is then used to study the thermal runaway propagation at different coolant flow rates.</div>

Assessment of Spatiotemporal Groundwater Recharge Distribution Using SWAT-MODFLOW Model and Transient Water Table Fluctuation Method

Recharge is a crucial section of water balance for both surface and subsurface models in water resource assessment. However, quantifying its spatiotemporal distribution at a regional scale poses a significant challenge. Empirical and numerical modeling are the most commonly used methods at the watershed scales. However, integrated models inherently contain a vast number of unknowns and uncertainties, which can limit their accuracy and reliability. In this work, we have proposed integrated SWAT-MODFLOW and Transient Water Table Fluctuation Method (TWTFM) to evaluate the spatiotemporal distribution of groundwater recharge in Anyang watershed, South Korea. Since TWTFM also uses SWAT model percolation output data, calibration was performed for individual models and a coupled model. The coupled model was calibrated using daily streamflow and hydraulic head. The SWAT-MODFLOW model performed well during the simulation of streamflow compared to the SWAT model. The study output showed that the study watershed had significant groundwater recharge variations during the simulated period. A significant amount of recharge happens in the wet season. It contributes a significant amount of the average annual precipitation of the region. The direct flow components (surface and lateral) showed significant contributions when the water balance components were evaluated in the region. TWTFM showed a glimpse to estimate recharge, which requires representative monitoring wells in the study region. Comprehensively, the SWAT-MODFLOW model estimated groundwater recharge with reasonable accuracy in the region.

The impact of flow induced by rotating magnetic fields on processes in a molten conductive medium

This paper studies a method of stirring liquid metal by the action of rotating magnetic fields using two ring inductors placed next to each other. These inductors generate magnetic fields rotating in opposite directions. The aim of this study is numerical investigation of the generated fluid flow and its impact on the homogenization of a two-phase medium, as well as on the crystallization process. The impact of these electromagnetic forces proves to cause the generation of intense poloidal flow component. The arising flow is accompanied by oscillatory motion of vortex structures and their interaction resulting in effective mixing of the liquid metal. The moderate values of the force parameter have been found to lead to the most homogeneous medium under stirring. Under non-stationary action, the force parameter modulations in a certain frequency range have practically no effect on the homogeneity occurrence time and the homogeneity value. The positive effect of stirring by magnetic fields of complex topology on the rate and homogeneity of metal solidification is stated. The obtained results are relevant for improving the quality of foundry ingots.

Anesthesia and the Merry-go-round of Information in the Brain.

Anesthesia and the Merry-go-round of Information in the Brain.

Genetic, vascular and amyloid components of cerebral blood flow in a preclinical population

Aging-related cognitive decline can be accelerated by a combination of genetic factors, cardiovascular and cerebrovascular dysfunction, and amyloid-β burden. Whereas cerebral blood flow (CBF) has been studied as a potential early biomarker of cognitive decline, its normal variability in healthy elderly is less known. In this study, we investigated the contribution of genetic, vascular, and amyloid-β components of CBF in a cognitively unimpaired (CU) population of monozygotic older twins. We included 134 participants who underwent arterial spin labeling (ASL) MRI and [18F]flutemetamol amyloid-PET imaging at baseline and after a four-year follow-up. Generalized estimating equations were used to investigate the associations of amyloid burden and white matter hyperintensities with CBF. We showed that, in CU individuals, CBF: 1) has a genetic component, as within-pair similarities in CBF values were moderate and significant (ICC > 0.40); 2) is negatively associated with cerebrovascular damage; and 3) is positively associated with the interaction between cardiovascular risk scores and early amyloid-β burden, which may reflect a vascular compensatory response of CBF to early amyloid-β accumulation. These findings encourage future studies to account for multiple interactions with CBF in disease trajectory analyses.

Doppler Ultrasound Flow Reversal in the Superior Sagittal Sinus to Detect Cerebral Venous Congestion in Vein of Galen Malformation.

Vein of Galen malformation is a rare congenital cerebrovascular malformation. In affected patients, increased cerebral venous pressure constitutes an important etiologic factor for the development of brain parenchymal damage. The aim of this study was to investigate the potential of serial cerebral venous Doppler measurements to detect and monitor increased cerebral venous pressure. This was a retrospective monocentric analysis of ultrasound examinations within the first 9 months of life in patients with vein of Galen malformation admitted at <28 days of life. Categorization of perfusion waveforms in the superficial cerebral sinus and veins into 6 patterns was based on antero- and retrograde flow components. We performed an analysis of flow profiles across time and correlation with disease severity, clinical interventions, and congestion damage on cerebral MR imaging. The study included 44 Doppler ultrasound examinations of the superior sagittal sinus and 36 examinations of the cortical veins from 7 patients. Doppler flow profiles before interventional therapy correlated with disease severity determined by the Bicêtre Neonatal Evaluation Score (Spearman ρ = -0.97, P = < .001). At this time, 4 of 7 patients (57.1%) showed a retrograde flow component in the superior sagittal sinus, whereas after embolization, none of the 6 treated patients presented with a retrograde flow component. Only patients with a high retrograde flow component (equal or more than one-third retrograde flow, n = 2) showed severe venous congestion damage on cerebral MR imaging. Flow profiles in the superficial cerebral sinus and veins appear to be a useful tool to noninvasively detect and monitor cerebral venous congestion in vein of Galen malformation.