Actual Flow Research Articles

Emerging Trend and Causes of Discrepancy between Proposed and Actual Flows of Foreign Capital into Nepalese Energy Sector

This paper aims to investigate the trend and causes of vast gap between actual and proposed FDI flows into energy sector by employing principal component analysis and one sample t test. Foreign direct investment is a main source of capital for the development of energy products in Nepal. Therefore, government of Nepal has emphasized to rise inflows of foreign capital to bridge the gap between demand and supply of capital in energy area. However, Nepal has received very small amount of actual FDI from the proposed FDI. It is found the increasing trend of FDI flows into energy sector after 2014/15 and risk factors of the country, market size, administrators’ quality, availability of physical infrastructure and public servant performance are the major factors causing the all proposed foreign capital do not actually flow into the energy sector. To minimize this divide, it is imperative to enhance country-risk factors. To narrow this gap, it is imperative to enhance country-risk factors and enhance the performance of bureaucrats in their specific domains.

The impact of cash flow forecasting errors on the accuracy of business value estimation

Aim. To assess the impact of cash flow forecasting errors on the accuracy of business value estimation and to develop a methodology for applying the income approach to business valuation, aimed at reducing these errors and improving the accuracy of business valuation.Objectives. To systematize external and internal factors of cash flows of enterprises of the real sector of economy; to give a qualitative assessment of the impact of large-scale hard-to-predict negative events — the so-called black swans — on cash flows, business value and to determine the requirements to the qualities of a modern manager necessary for effective work in conditions of non-stationary impact of hard-to-predict large-scale external risks; to assess the impact of errors in cash flow forecasting of the post-forecast period on the result of business valuationMethods. On the basis of the system approach the author applied quantitative methods of time factor accounting in financial management, methods of situational, comparative, factor and regression analysis, as well as approaches and methods of financial risk management.Results. According to the results of the research the external and internal factors of cash flows of the enterprises of the real sector of economy were systematized, the most significant factors of deviation of expected and actual cash flows were singled out. A qualitative assessment of the influence of “black swans” on cash flows and business value is given, the requirements for the qualities of a modern manager necessary for effective work in conditions of non-stationary impact of hard-to-predict large-scale external risks are determined. In addition, analytical estimates of the impact of cash flow forecasting errors on the results of applying the methods of income approach to business value assessment are obtained. The methodology of business value estimation, oriented on the increase of estimation accuracy on the basis of taking into account the stages of business life cycle, is offered.Conclusions. The quantitative estimates obtained in the article and the developed recommendations serve as a theoretical and methodological basis for increasing the efficiency of the income approach to business value assessment in conditions of increased uncertainty and market volatility.

Optimal shape design of printing nozzles for extrusion-based additive manufacturing

The optimal design seeks the best possible solution(s) for a mechanical structure, device, or system, satisfying a series of requirements and leading to the best performance. In this work, optimized nozzle shapes have been designed for a wide range of polymer melts to be used in extrusion-based additive manufacturing, which aims to minimize pressure drop and allow greater flow control at large extrusion velocities. This is achieved with a twofold approach, combining a global optimization algorithm with computational fluid dynamics for optimizing a contraction geometry for viscoelastic fluids and validating these geometries experimentally. In the optimization process, variable coordinates for the nozzle’s contraction section are defined, the objective function is selected, and the optimization algorithm is guided within manufacturing constraints. Comparisons of flow-type and streamline plots reveal that the nozzle shape significantly influences flow patterns. Depending on the rheological properties, the optimized solution either promotes shear or extensional flow, enhancing the material flow rate. Finally, experimental validation of the nozzle performance assessed the actual printing flow, the extrusion force and the overall print control. It is shown that optimizing the nozzle can significantly reduce backflow-related pressure drop, positively impacting total pressure drop (up to 41 %) and reducing backflow effects. This work has real-world implications for the additive manufacturing industry, offering opportunities for increased printing speeds, enhanced productivity.

Polydisperse particle inline image method and its application onto gas–liquid flow in a stirred tank

AbstractBubbles of different sizes exhibit distinct hydrodynamic behaviors and their dense coexistence complicates seriously the multiphase flow. The commonly‐used arithmetic average method (e.g., PIV) treats every bubble equally and consequently erases many physical details. In this study, a polydisperse particle inline image method is developed to simultaneously measure comprehensive feature set of every bubble in bubble swarms and carrier phase velocity. By harnessing the optimal frame rate capture alongside assigning IDs for tracking, complete identification of polydisperse swarm in single frame is integrated with the accurate acquisition of transient dynamics across multiple frames. In gas–liquid stirred tanks, the bubble deformation is notably intensified owing to the presence of collisions driven by velocity differences. A novel analysis of bubble hydrodynamics decomposed by bubble size reveals they are jointly commanded by the inertial effect and size effect. Actual flow regime of the system is essentially the superposition of multiple dissimilar flow patterns.

A Coupling Model for Measuring the Substitution of Subways for Buses during Snowstorms: A Case Study of Shenyang, China

The development of integrated public transportation networks has received widespread attention in recent years. Especially in global northern cities, improving the substitution of subways for buses could meet population travel demand during snowstorms, which minimizes the impact of snowstorms on the public transportation network. Furthermore, the development of rail transit is conducive to the intensive and efficient use of land resources. Therefore, in this study, we selected a northern Chinese city, Shenyang, as a case study. For obtaining the population travel demand, we collected the actual population flow data in the morning and evening peaks during snowstorms. The network analysis was used to identify the loopholes and key stations in the subway and bus networks, respectively. A coupling model was built to measure the coupling value of each station in the subway and bus networks, according to its population travel demand and supply capacity, which was further used to measure the substitution of subways for buses in the morning and evening peaks during snowstorms. The results indicate that some subway stations were in a coupling state, while their surrounding bus stations were in a decoupling state. These subway stations could replace the bus stations to reduce the impact and damage of snowstorms on public transportation network. However, some subway stations and the surrounding bus stations were all in a decoupling state, which were under great pressure to meet the population commuting demand during snowstorms. This study can provide insight into optimizing public transportation network planning and design in many northern regions and help to coordinate land and transportation utilization.

Low reynolds number carbon-containing composite liquid fuel pipeline transportation under sub-ambient and subzero temperatures

An experimental study of the effect of lowered temperatures (from 25 °C to −5 °C) on the velocity and viscosity of composite liquid fuel (CLF) flow in mini-channels was performed at low Reynolds numbers. Examined CLFs are composed of water, coking coal, and sludge from coking coal processing, mixed with lignite polymer, acidic sodium pyrophosphate, isononylphenol and a mixture of mono-and dialkylphenols with ethylene oxide. The method of adjusting the critical ratio between the Reynolds numbers at the actual liquid flow rate of the local consumer and at the pump flow rate has been developed for CLF pipeline transport in off-season and winter temperature conditions. It is based on the constant regulation of the pump flow rate, depending on the current external temperature. Under a controlled decrease in the pump flow rate and a CLF temperature of −5 °C, its transportation by pipeline was successfully performed at laboratory conditions.

Evaluation of the prototype performance of Wanjiazhai Francis turbine with flow pattern analysis

Multiple Francis turbines are installed in Wanjiazhai water conservancy project to generate electricity, and the operating conditions of the units vary greatly. Because the unit head itself is not high, and the parameters such as head, flow and output vary widely, the operation of the unit becomes very complex. Aiming at this problem, this study predicts and analyzes different typical operating conditions during the operation of the unit, and compares them with the field measured results. The analysis of Prototype unit helps us understand the actual flow state inside the unit and observe the possible complex flow phenomenon. Therefore, the distribution of vortices inside the unit is analyzed in depth, and the flow structures inside the volute, stay vane, guide vane, runner and draft tube are compared to serve the safe and stable operation.

Examining the interfacial behavior of non-Newtonian gas-liquid two-phase flow in horizontal square microchannels

This study investigates the flow dynamics of a non-Newtonian two-phase flow within a horizontal square microchannel. The experimental apparatus employed an acrylic channel with a side length of 8 × 10−4 m. Nitrogen served as the test gas, and the test liquids consisted of water and CMC (Carboxymethylcellulose) aqueous solutions at concentrations of 0.2 and 0.4 %wt. The superficial velocity of working gas and liquids spanned ranges of 0.26–20 m/s and 0.05–1.0 m/s, respectively. A differential pressure transducer was used to measure pressure gradients, while a high-speed video camera captured the flow behavior for analysis with a custom image processing technique. Nonlinear regression statistical analysis was applied to establish the criteria for flow pattern transition. Furthermore, signal processing techniques such as PSD (Power Spectral Density), DWT (Discrete Wavelet Transform), ANN (Artificial Neural Network), and Kolmogorov entropy were employed to analyze the flow behavior based on the pressure gradient signals from the differential pressure transducers. Our findings reveal the occurrence of bubbly, slug, slug-annular, and churn flow patterns. The nonlinear regression statistical analysis offered ambiguous results for determining flow pattern transitions. However, an empirical coefficient was obtained for the nondimensional liquid height. Moreover, the empirical nondimensional liquid height aligned well with the experimental values. The PSD and DWT analysis corroborated each other in clearly characterizing the flow pattern based on pressure gradient fluctuation and wavelet energy. The Kolmogorov entropy effectively captured the chaotic flow pattern. Furthermore, the ANN analysis demonstrated a solid agreement between the predicted and actual flow patterns.

Continuous Eddy Simulation vs. Resolution-Imposing Simulation Methods for Turbulent Flows

The usual concept of simulation methods for turbulent flows is to impose a certain (partial) flow resolution. This concept becomes problematic away from limit regimes of no or an almost complete flow resolution: discrepancies between the imposed and actual flow resolution may imply an unreliable model behavior and high computational cost to compensate for simulation deficiencies. An exact mathematical approach based on variational analysis provides a solution to these problems. Minimal error continuous eddy simulation (CES) designed in this way enables simulations in which the model actively responds to variations in flow resolution by increasing or decreasing its contribution to the simulation as required. This paper presents the first application of CES methods to a moderately complex, relatively high Reynolds number turbulent flow simulation: the NASA wall-mounted hump flow. It is shown that CES performs equally well or better than almost resolving simulation methods at a little fraction of computational cost. Significant computational cost and performance advantages are reported in comparison to popular partially resolving simulation methods including detached eddy simulation and wall-modeled large eddy simulation. Characteristic features of the asymptotic flow structure are identified on the basis of CES simulations.

Exploring compiler optimization space for control flow obfuscation

Code obfuscation is a promising technique for securing software and protecting it from adversaries. The objective is to harden the exploitation of security vulnerabilities for the attacker as well as launching of successful attacks. Obfuscation can be classified into layout, data, and control flow obfuscation. Control flow obfuscation impedes the understanding of the application logic by making it complicated to determine the actual control flows. Although numerous control flow methods exist in the literature, the role of existing compiler optimizations has just been discovered. This paper is the first one that explores the existing optimization space of LLVM compiler for obfuscating code. Our techniques optimally explore the native compiler's optimizations to improve the original code performance and reduce memory space with no disruptive efforts, tools, or extra costs. In the CBench benchmark suite, our work is able to improve 246%, 143%, and 468% in cyclomatic complexity, program length, and implementation effort, respectively, compared to unobfuscated code. Therefore, instead of inventing new obfuscation tools, the existing compiler optimizations can easily be used to obfuscate control flows, saving the overall cost and efforts.

Experiments on capacitance based liquid flow meter with parallel channels used in two-phase

A new flow meter has been proposed to measure liquid mass flow rate in a two-phase system. Irrespective of the input flow, the proposed system transforms incoming stream into laminar stratified flow. This configuration offers a promising avenue for assessing liquid flow rates in a two-phase system by leveraging measurements of liquid column height. Extensive performance assessments have been conducted for different vapour and liquid flows. Since the fluid properties are taken into consideration for designing the system, the temperature dependence on the performance of the flow meter also has been studied. The outcome of these studies has yielded a robust correlation between the actual liquid flow rate and the value deduced from the observed liquid column height. The correlation developed between the actual liquid flow rate and that determined from the height of fluid was accurate with an error of ± 3.8 %. It is also found that this flow meter is capable enough to determine the changes in flow conditions with temperature and would provide flow measurements within an error of ± 4 %. This novel two-phase flow meter not only advances the precision of liquid mass flow rate measurements but also demonstrates its adaptability in accommodating changing flow conditions, particularly those driven by temperature dynamics. The findings presented herein underscore the potential of this innovative flow meter as a reliable tool for accurate flow rate determination in diverse industrial applications such as cryogenics, superconductivity, etc.

Numerical analysis of seepage law for radial fluid flow in a single fracture: Comparison between smooth and rough fractures

This paper investigated the differences for the hydraulic characteristics in a single fracture between using the Navier–Stokes (N–S) equation and Darcy's law, which would be benefit to understand the seepage mechanism in the fracture. A numerical model of the radial flow was established considering the aperture size and water injection flow rate. Some conclusion could be given. First, the Darcy's law only described the seepage characteristics when the flow rate was small when the flow rate and pressure response have a linear relationship. While the N–S equation could describe the linear and nonlinear seepage characteristics, resulting in a better model of the actual fracture seepage flow. Second, the aperture size had a limited influence on the water pressure and seepage velocity inside the fracture when the flow rate was small. It began to have a significant impact influence on the seepage characteristics inside the fracture with the aperture increased. Third, the flow–pressure response conformed to the Forchheimer equation in the fracture. The critical Reynold number would decrease from 1.2 to 0.0116 when fracture aperture decreased from 3 to 0.5 mm using the N–S equation. The degree of nonlinearity of the fluid flow increases with fracture roughness increasing. This work gave a guidance to the difference in the two seepage theories and correction for the result by Darcy law, which was widely used in the engineering calculation.

Cheating in the evaluation. An expedient to estimate the impact of intangibles on the enterprise value of the high-growth start-ups

This study investigates the effect of investments in intangible fixed assets and human capital on the Enterprise Value (EV) of Italian high-growth startups (HGSs). To test our hypotheses, we conducted several Ordinary Least Squares (OLS) regression analyses on a dataset comprising 782 HGSs. The EV was esti-mates using the Discounted Cash Flow (DCF) method. Our findings reveal a posi-tive and statistically significant relationship between investments in intangible as-sets and EV. However, investments in human capital and highly skilled workers show a negatively relationship with EV. Lastly, a positive and statistically signifi-cant relationship between value-added per employees and the EV of HGSs has been identified. This study offers valuable insight into the process through which new firms gener-ate value. By strategically investing in intangible assets and human capital, startups not only enhance their probability of survival but also improve their growth potential. This allows these companies to overcome the challenges of the early stage and embark on a sustainable growth process. To spotlight the unique value drivers of these companies, unlike prior studies, we manually estimate the EV. We have employed the DCF method by playing the cards face up: we used the actual cash flows realized by the HGSs during the study period instead of rely-ing on forecasts. We have therefore "cheated" to measure the value created by the HGSs. This research can be considered a pioneering study that significantly con-tributes to the ongoing debate on the value creation process in fast growing startups.

Vehicle Counting System and Smart Traffic Light Control System

Improving traffic flow efficiency has become more important due to the growing number of vehicles in urban areas, and this requires optimizing traffic control systems. In order to reduce traffic, a smart traffic control system using infrared sharp sensors to count vehicles at intersections is proposed in this paper. The system uses sensors to measure distances to a fixed barrier, accurately counting vehicles while ignoring pedestrians. It was originally designed for four-way intersections but is adaptable to various junction types. Each lane’s unique count is controlled by a separate Arduino Nano Board, and the data is saved in microcontrollers. Following the aggregation and processing of these counts, an Arduino Mega Board modifies the traffic light timings in response to actual vehicle flow.

Research on controlling intelligent traffic light systems based on artificial intelligence algorithms

Intelligent traffic light systems are becoming an important application in traffic coordination. Artificial intelligence with deep learning models effectively recognizes vehicles participating in traffic from extracted images or real-time videos with high speed and accuracy. This paper presents an intelligent traffic light system based on real-time image analysis using the YOLOv8 artificial intelligence method to determine the density of vehicles participating in traffic at intersections. Consequently, the system automatically controls the timing of the traffic lights on the roads to align with the actual traffic flow. Through this method, the operation of traffic lights is continuously adjusted, ensuring efficient and safe traffic flow.

Приготовление растворов различной концентрации

When preparing treatment solutions of fertilizers and pesticides for technological processes, one should mix liquids taking into account the precise dosing of components. However, the existing designs of dosing and mixing devices do not provide qualitative dosing. Moreover, a sharp increase of fraction quantity may result in a hydraulic impact. To eliminate these disadvantages, based on analytical research of available designs and patent search results, the authors worked out a mixer for preparing solutions of various concentrations. The device is also capable of changing the ratio of components in the process of operation. The device provides smooth change of preparation concentrations due to the design of dosing valves forming square-shaped ports with a changing configuration. The port plates move relative to each other both horizontally and vertically. The proposed device smoothly changes the concentration of the solution, thereby providing for more accurate dosing. It was experimentally found that a smoother change in the flow rate of treatment liquid according to the solution concentration is observed at a distance from the axes of symmetry of the dosing device disks to the rotation axis of the distribution ports, equal to 0.04 to 0.1 m. The deviation of the actual treatment liquid flow rate from the calculated one does not exceed 5%. The integration of the developed mixer into the systems of fertigation units, sprayers and other specialized machines will ensure better quality of the fine irrigation of plants, seeds, and soil.

Generalized prediction for self-starting performance of two-dimensional hypersonic inlets

The acceleration self-starting performance of a hypersonic inlet is pivotal for ensuring the stable operation of a scramjet. While the geometric configuration of the internal contraction section (ICS) considerably influences the inlet's self-starting performance, the current prediction model solely considers the internal contraction ratio. To encompass the entire geometric configuration's influence on ICS, a generalized prediction model for the acceleration self-starting Mach number of critical hard unstart two-dimensional hypersonic inlets is proposed. This model calculates the theoretical reattachment pressure rise of the main separation bubble within the actual unstarted flow structure of the hypersonic inlet. Additionally, it computes the theoretical pressure rise assuming the main separation bubble is in a critical state. By comparing these pressures, the model evaluates whether the main separation bubble can be sustained under given incoming flow conditions, predicting the self-starting Mach number. This modeling approach offers broad adaptability to various ICS configurations and incoming flow Reynolds numbers. Each step of the prediction model and the final computational results underwent rigorous evaluation through unsteady numerical simulations. Remarkably, the prediction results demonstrated exceptional alignment with simulation outcomes, surpassing the accuracy of previous prediction methods.

Reliability assessment and optimization of computer networks based on neural networks

Abstract Amidst the swift evolution of computer technologies, the prevalence of computer networks has become pivotal across diverse sectors, increasingly reliant on their robust functionality. This study rigorously evaluates and enhances the reliability of computer networks by leveraging an index system and an evaluation model devised through neural networks. To strengthen network dependability, this research employs a Hopfield neural network to address multi-constraint Quality of Service (QoS) multicast routing challenges, thereby elevating network reliability. Simulation experiments demonstrate that the Hopfield neural network effectively mitigates network latency and exhibits superior convergence performance compared to conventional QoS multicast routing methods. Further, this paper applies the neural network-based evaluation model to analyze the reliability of the air traffic network within the H-area after integrating the optimized computer network framework. It is observed that the most significant contributor to traffic flow loss is the network's degree value. An analysis of traffic flow density, employing actual sector flow data, reveals that high traffic volumes typically precipitate congestion. Nonetheless, the traffic flow density value consistently exceeds 100, suggesting that the enhanced computer network model holds practical applicability in real-world scenarios.

Experimental study on wax deposition of highly paraffinic oil in intermittent gas-oil flow in pipelines

Oil-gas two phase wax deposition is a fairly common and open-ended question in flow assurance of multiphase transportation pipelines. This paper investigated the two main aspects of oil-gas two phase wax deposition layer: apparent thickness and crystal structure characteristics. A typical highly paraffinic oil in Bohai Sea, China, was used as the experimental material to investigate the wax deposition thickness in oil-gas two phase under the influence of different oil temperatures, superficial gas/liquid phase velocities and gas-oil ratios by using multiphase flow loop experimental device. Just as in the classical theory of wax molecular diffusion, it showed that wax deposition thickness of oil-gas two phase increased with increasing oil temperature. Analysis of the impact of different superficial phase velocities found that the actual liquid flow heat transfer and shear stripping was the gas phase dominant mechanisms determining wax deposit thickness. In addition, the crystal structure of the wax deposition layer was characterized with the help of small-angle X-ray scattering (SAXS) for different circumferential positions, flow rates and gas-oil ratios. The bottom deposition layer had a complex crystal structure and high hardness, which were subject to change over flow rate variations. Furthermore, the SAXS results provided evidence that the indirect effect of the actual liquid velocity modified by the gas phase was the main mechanism. Our study of the effect of gas phase on the wax deposition of oil-gas two phase will help shed light onto the mechanism by which this important process occurs. Our findings address a very urgent need in the field of wax deposition of highly paraffinic oil to understand the flow security of oil-gas two phase that occurs easily in multiphase field pipelines.

Analysis and experimental study on flow characteristic and rangeability of plug control valve

According to the specific structure of the plug valve, a method for estimating the rated flow coefficient was proposed. Based on a variable diameter flow passage model, flow coefficient tests for four plug control valves with different specifications were carried out, and the experimental data were analyzed and researched. The results show that: (1) The proposed estimation method for calculating the rated flow coefficient of the plug valve, in which the deviation range is -6.58%∼4.10%, meets the requirement of the standard IEC 60534-2-4-2009 as not exceeding ±10%; (2) Due to the manufacturing errors, the actual inherent flow characteristic of the plug control valve is between equal percentage and parabola. The larger the flow capacity is, the more equal the flow characteristic gets; (3) The plug control valve has an outstanding feature of high rangeability, which can be up to R=979 and is obtained based on the flow coefficient test data.