Flow Direction Research Articles

Hydraulic and axial force characteristics of large axial flow pumps under different flow conditions

Abstract Axial flow pumps often experience uneven distribution of axial force on the blades when deviating from design conditions, which can easily lead to local damage to the pump blades. In response to this issue, this article conducts a detailed study on the hydraulic and axial force characteristics of large vertical axial flow pumping stations in China based on constant and non-constant numerical simulation research methods. Research has found that under biased operating conditions, due to the angle between the water flow direction inside the impeller and the impeller blades, the water body collides with the blades, resulting in concentrated pressure distribution on both sides of the inlet side of the impeller blades. Under low flow conditions, the high axial force area of the impeller blade is concentrated in the middle and rear position of the suction surface, while under high flow conditions, the high axial force area is widely distributed. Under the conditions of 0.8 Q to 1.4 Q, the fluctuation of axial force on the impeller blades is mainly affected by the rotation of the impeller blades. However, under low flow conditions, due to the turbulence of the flow state, there is no obvious pattern of axial force variation on the impeller blades. In addition, under different flow conditions, there is no obvious pattern in the fluctuation of axial force on the guide vanes. This also proves that there are problems such as uneven axial force distribution and no periodic changes in the impeller blades under low flow conditions, which can easily lead to damage to the impeller blades. The above analysis can provide some reference for the design of impeller blades.

Flow characteristics inside rectangular Tesla valve with different width-to-narrow ratios

To investigate the influence of the flow channel’s width-to-narrow ratio on the Tesla valve’s flow characteristics, this paper establishes five Tesla valve models with different width-to-narrow ratios. Employing the laminar flow model, CFD methods were used to numerically simulate both the forward and reverse flows through the Tesla valve across a spectrum of width-to-narrow ratios, ranging from 0.2 to 1. The results reveal the flow trends in the straight or arc channels show opposite variation patterns when flowing in forward and reverse directions. The flow rate passing through straight channel is more sensitive to the response of a small width-to-narrow ratio. Irrespective of the flow direction, as the width-to-narrow ratio increases, the fluid flow within the valve demonstrates increasingly pronounced stratification. The pressure curve of the diversion section assumes an “∞” shape in forward flow, whereas in reverse flow, it assumes a “flat plate” shape.

Modulation of Residual Current on Impacts of Shoreline Changes in the Yangshan Deepwater Harbor

Abstract Coastal land reclamation projects significantly alter tidal wave propagation and residual flow structures. This study focuses on the Yangshan Deepwater Harbor (YDH) in China, aiming to scrutinize the effects of construction activities on residual flow patterns employing the Finite Volume Community Ocean Model (FVCOM). By calculating Lagrangian residual currents across different tidal periods, we analyzed alterations in flow patterns and velocity distribution pre- and post-construction. The research findings reveal that, although the residual flow direction in the harbor and the southern sea area remains largely unchanged from the pre-construction phase, the northern sea area has experienced a shift in residual flow direction. It is noteworthy that after the implementation of the project, the residual flow at the East Entrance was greatly weakened. This study underscores that coastal constructions can lead to remarkable influence on residual currents and emphasizes the necessity for thorough hydrodynamic assessments in the planning and implementation stages of coastal constructions.

The Cervical and Meningeal Lymphatic Network as a Pathway for Retrograde Nanoparticle Transport to the Brain.

The meningeal lymphatic vessels have been described as a pathway that transports cerebrospinal fluid and interstitial fluid in a unidirectional manner towards the deep cervical lymph nodes. However, these vessels exhibit anatomical and molecular characteristics typical of initial lymphatic vessels, with the absence of surrounding smooth muscle and few or absent valves. Given its structure, this network could theoretically allow for bidirectional motion. Nevertheless, it has not been assessed as a potential route for nanoparticles to travel from peripheral tissues to the brain. We employed superparamagnetic iron oxide nanoparticles (SPIONs), exosomes loaded with SPIONs, gold nanorods, and Chinese ink nanoparticles. SPIONs were prepared via chemical coprecipitation, while exosomes were isolated from the B16F10 melanoma cell line through the Exo-Spin column protocol and loaded with SPIONs through electroporation. Gold nanorods were functionalized with polyethylene glycol. We utilized C57BL/6 mice for post-mortem and in vivo procedures. To evaluate the retrograde directional flow, we injected each nanoparticle solution in the deep cervical lymph node. The head and neck were fixed for magnetic resonance imaging and histological analysis. Here we show that extracellular vesicles derived from the B16F10 melanoma cell line, along with superparamagnetic iron oxide nanoparticles, gold nanorods, and Chinese ink nanoparticles can reach the meningeal lymphatic vessels and the brain of C57BL/6 mice after administration within the deep cervical lymph nodes post-mortem and in vivo, exclusively through lymphatic structures. The functional anatomy of dural lymphatics has been found to be conserved between mice and humans, suggesting that our findings may have significant implications for advancing targeted drug delivery systems using nanoparticles. Understanding the retrograde transport of nanoparticles through the meningeal lymphatic network could lead to novel therapeutic approaches in nanomedicine, offering new insights into fluid dynamics in both physiological and neuropathological contexts. Further research into this pathway may unlock new strategies for treating neurological diseases or enhancing drug delivery to the brain.

Simulation and performance characteristics of rock with borehole using Visual Finite Element Analysis

Purpose. This study aims to investigate fluid flow and heat transfer within rocks containing boreholes, focusing on the complex mechanisms within hot reservoirs. Non-commercial finite element (FE) software is used to visualize and present the results. Methods. The study involved the use of FE method with Visual Finite Element Analysis (VisualFEA) software to analyze the coupled phenomena of fluid flow and heat transfer in a rock sample. Special attention was given to incorporating material structure and geotechnical analysis in the software, as well as the treatment of cracked elements. In addition, the validation was done by comparing the current numerical solution using VisualFEA with the numerical solution using ANSYS Software. Findings. The study findings highlight the capabilities of VisualFEA software to accurately represent fluid flow, stress, and heat transfer in borehole-containing rocks. The results include insights into flow direction within the borehole, temperature distribution, and the validation of the software performance against expected system behavior. The study demonstrates the effectiveness of VisualFEA in handling complex loading and its ability to visualize multiple flow directions within a 2D model. The results are presented in the form of contours and curves. Originality. This study contributes to the field demonstrating the application of VisualFEA software in analyzing fluid flow and heat transfer in rocks with boreholes. The focus on incorporating material structure, geotechnical analysis, and treatment of cracked elements adds originality to the study, providing a comprehensive understanding of the coupled phenomena in hot reservoirs. Practical implications. The practical significance of this study is in the validation and benchmarking of VisualFEA software for studying fluid flow and heat transfer in geotechnical application. The findings can be utilized by geotechnical engineers and researchers to better understand the behavior of borehole-containing rocks under specific pressure and thermal loading conditions. The insights gained from this study can be used in decision-making processes related to resource mining, reservoir engineering, and geothermal energy use.

Migration processes in the Republic of Kazakhstan: current situation and consequences

Rural population migration is an objective process that affects the economic, environmental, social and demographic development of countries and their individual territories. Regulation and supervision of the migration process is one of the priority tasks of the state. The aim is to the scale and direction of migration flows in rural areas of the republic, the reasons for migration and the degree of influence on the labor market in rural areas are considered. Methods - comparisons to determine quantitative indicators characterizing the level of resettlement of economically active citizens. Assessment of the dynamics of those who arrived and left the RS was carried out by the methods of grouping and graphical analysis. Generalization method - in formulating the main aspects of resettlement. Results - the authors state that it is necessary to improve the mechanisms of legal labor migration, explanation and counseling, legal protection and organizational measures for those arriving and departing. Special attention should be paid to the development of infrastructure, creation of new jobs, career opportunities, high income, social conditions in rural settlements (RS) with high levels of local displacement. Based on the study, it is concluded that even positive trends and sustainable growth in production do not suppress the incentives for outflow to the city both for permanent residence and in search of temporary work. Conclusions - the location of rural areas near the regional center, the location of agricultural enterprises and farms, favorable natural and climatic conditions have a great impact on the attraction of migrants to rural areas. Based on the above, the key factor contributing to the reduction of migration loss of population can be called diversification of the economy in rural areas, further development of existing and creation of new production facilities.

Mathematical analysis for flow of hybrid nanofluid over a vertical stretchable surface: Assisting and opposing flows

Research Problem: The importance of improving the temperature properties of commonly used fluids in industrial processes is being addressed in this research. Nanofluids, which are composed of extremely small particles dispersed in common liquids such as water or petrol, are the main subject of this area of study. Using a vertically stretchable surface subjected to thermal radiation, the study examines the heat transfer behavior and efficiency of nanofluids. Methodology: Nanofluids that convey heat are studied by applying the fundamental rules of fluid physics to the variables that control their motion. To measure the amount of energy transferred, a nanofluid model is used. Similarity transformations are used to convert the system’s differential equations into ordinary differential equations (ODEs). The subsequent set of nonlinear ODEs is solved using numerical methods. Utilizing graphical analysis, patterns of velocity and temperature may be seen, and their responses to changes in other parameters can be investigated. Implications: This research has important implications for our knowledge of how nanofluids act in heat transfer applications, especially when exposed to thermal radiation and working with vertically stretchy surfaces. The effects of flow direction and thermal conductivity on distributions of velocity and temperature were elucidated, among other important results. More effective heating and cooling systems may be possible as a result of these findings, which have consequences for improving heat transfer processes in industrial environments. Future Work: To better understand how nanofluids behave in heat transfer applications, future studies might investigate more complicated situations and boundary circumstances. It may be possible to optimize nanofluid formulations by studying the impact of various nanoparticle kinds and concentrations on heat transfer efficiency. Research could be more applicable to real-world industrial processes if the numerical results were experimentally validated.

Research on the jet active control mechanism of gas-liquid separation in helical-axial multiphase pumps

In the field of deep-water oil and gas extraction, the intermittent gas blocking phenomenon in helical-axial multiphase pumps leads to decreased pump performance and reliability, severely limiting their large-scale application and promotion in engineering projects. To address this challenge, this study is based on the principle of jet flow field control to flow separation, utilizing external energy for active intervention to suppress the separation phenomena and improve the hydraulic efficiency within the impeller flow channel. The research reveals that the jets achieved a reconstruction of the internal flow in the helical-axial gas-liquid mixed transport pumps. Using orthogonal experimental methods, a preliminary predictive analysis of the factors influencing the effectiveness of the jet system was conducted. The study explored the impact of jet parameters on enhancing the performance of helical-axial gas-liquid mixed transport pumps from the perspective of diminishing gas aggregation at the trailing edge of the rotor cascade and curtailing backflow conditions, and established a mathematical model for the head and efficiency of helical-axial multiphase pumps under jet active control. Research indicates that the jet velocity significantly impacts the efficiency enhancement of multiphase pumps, with an optimal jet speed coefficient, Cjet = 10, identified. Beyond this speed, the benefits brought by increased jet velocity do not compensate for the costs of introducing high-speed jets, and instead, may lead to a reduction in the efficiency of the pump. Jet flow field control methods alleviate the suction side gas aggregation downstream of the jet holes and in the flow domain traversed by the jets, effectively reducing the aggregation of gas phases in the rear channel of the rotor and suppressing backflow near the trailing edge of the rotor cascade. Jet control measures strengthen the working capacity of the blade in the flow direction beyond 0.35 times the length of the streamline, expanding the working range of the blade and enhancing the work efficiency of the multiphase mixed transport pump. Higher jet velocities result in more significant enhancements of blade working power, especially under conditions of high initial gas content, where the relative increase in blade load is more pronounced.

Segmented catalyst layer with varied catalyst loading to improve the cost performance of proton exchange membrane electrolysis cell, a numerical investigation

In this work, a steady-state, three-dimensional and non-isothermal numerical model for a proton exchange membrane electrolysis cell (PEMEC) is established. Based on this model, the distribution of catalyst loading is specifically designed according to the flow characteristics of both parallel and serpentine channels. In general, the catalyst loading is progressively reduced from inlet to outlet along the flow direction to match the local water content, leading to an innovative segmented catalyst layer which has not been studied yet for PEMEC applications. The electrochemical behavior of different segmentation schemes is investigated by comparing their polarization curves normalized by either electrode area or catalyst loading, while other physical fields such as velocity, pressure, water mole fraction and temperature distributions are also characterized. The numerical results reveal that a reasonable distribution of catalyst can reduce its amount of usage while still maintaining most of the PEMEC performance. In other words, the cost performance is significantly improved. This is mainly attributed to the full use of uneven water distribution in the flow channel, which improves the catalyst utilization efficiency significantly. This strategy is proved to be effective for both serpentine and parallel channels, ensuring a broad application prospect.

Mechanism analysis of turbulent convective heat transfer of supercritical carbon dioxide in serpentine tubes

This study examines turbulent convective heat transfer in serpentine tubes, a critical topic given their widespread use in supercritical carbon dioxide (SCO2) cycle heat exchangers. Despite their importance, this area remains underexplored. The novelty of this work lies in analyzing various serpentine tube orientations to optimize heat exchanger design under different mass and heat fluxes. Using a validated numerical method, the study explores the impact of SCO2 thermophysical variations on gravitational and centrifugal forces. Furthermore, heat transfer effects are evaluated by analyzing Morton and Dean vortices as well as Richardson numbers under various conditions. The results show that changes in mass and heat fluxes have a greater impact on the gravitational Richardson number than on the centrifugal Richardson number. When both effects are considered together, the Richardson ratio increases with higher mass and heat fluxes, emphasizing the dominance of centrifugal force over gravitational force. The study also found that changes in SCO2 flow direction most significantly affect the thermal and hydraulic characteristics of serpentine tube in a vertical orientation. The improvement index reaches values of 1.13, 2.38, and 3.26 at heat fluxes of 20, 40, and 60 kW/m2, respectively. However, under conditions of low mass fluxes and high heat fluxes, the serpentine tube with a lateral orientation and downward SCO2 flow demonstrates optimal overall performance. In this configuration, the performance index for thisconfiguration increases by up to 15 % at a heat flux of 60 kW/m2.

Modeling of the temperature field in the soil massive for different operating modes of the ground source heat pump

The paper considers modeling the influence of the operating modes of the ground source heat pump for heating and air conditioning systems using geothermal source of energy from borehole on the temperature of the soil formation around the borehole with the account of climate conditions of Ukraine. The proposed methodology of modelling of the ground source heat pump with the account of reversible direction of heat flow for heating and cooling work modes contributes to the field of energy system models. The ultimate goals are to obtain criterion dependencies for calculating the operating parameters of a geothermal borehole and to develop a methodology for designing geothermal boreholes taking into account their long-term operation in a cyclic mode. The idea behind the method allows high spatial and temporal resolution as well as the inclusion of the technical details of the power system and formation the temperature of the soil massive around the borehole for the climate conditions of the Ukraine and South-East Regions of Europe. The novelty of this method is the usage of a parametric approach is chosen to analyze different reversible operating modes of the ground source heat pump for heating and cooling. This provides insights on the systematic effects of ground source heat pump operation with regeneration with limitation on reaching negative temperatures at the bottom of the borehole, which can lead to ice formation, an increase in the volume of soil massive during freezing and destruction of pipelines. The article describes the change in the temperature of the soil mass under the operating conditions of a heat pump in two modes - stationary and with alternating "heat supply - cooling (air conditioning)" for long-term operation. Based on the obtained results it was revealed that when a geothermal borehole operates with an alternating direction of heat flow (with regeneration), the long-term consequences of operation associated with the deviation of the soil massive temperature from the background value are reduced. The additional novelty aspect of modelling was obtained for the operating parameters of a geothermal source of energy with the account of longterm reversible operating mode of the heat pump. The energy balance model is well suited for the analysis of temperature in the bottom part of the geothermal boreholes was revealed for heating and air conditioning systems due to the non-stationary thermal loads determined by climatic conditions of the Ukraine and South-East Regions of Europe. The obtained results may serve as a new approach to optimization technical and economic indicators of geothermal boreholes during operation of the ground source heat pump operating with the account of reversible direction of heat flow for heating and cooling work modes to have continuous improvement of energy efficiency

Numerical modeling of heat transfer mechanism in remote sensing bulb of thermal expansion valves

Thermal management of automotive systems has garnered a lot of focus in recent times to improve the energy efficiency of vehicles and address the challenge of global warming. In combustible fuel vehicles, the heat pump compressor is driven by the engine power which leads to changes in operating condition of the cycle while the vehicle is in motion. In electric vehicles, a combined thermal management strategy handles both cabin and battery pack cooling/heating depending on the ambient conditions and power requirements by adjusting refrigerant flow rates and flow directions with sophisticated valves. Irrespective of the vehicle type, effective variable refrigerant flow control is prerequisite to ensure optimum thermal comfort with minimum energy. Thermal expansion valves (TXV) are the most widely used method for regulating mass flow rate of refrigerant during the expansion step of the vapor compression cycle based on the principle of trying to maintain a fixed degree of superheat at the evaporator outlet. Conventional models of the thermal expansion valve ignore the time lag between fluctuation of temperature at the evaporator outlet and the corresponding change in pressure of the TXV remote sensing bulb, treating the valve as an instantaneous element during transient operation. This paper presents a novel method for determining the temperature profile and time constant of the remote sensing bulb response using numerical methods, in an attempt to capture the dynamics of thermal expansion valve in active heat pump cycle. Finite difference method was used to solve for the conduction heat transfer between the bulb and the heat exchanger outlet tube in perfect thermal contact applying the necessary boundary conditions. This improved modeling approach will be helpful in better prediction of the dynamic behavior of thermal expansion valves and how it influences the evaporative heat exchanger performance during transient operations to determine control algorithm and strategies.

Badminton birdie-like aerodynamic alignment of drifting dust grains by subsonic gaseous flows in protoplanetary discs

ABSTRACT Recent (sub)millimetre polarization observations of protoplanetary discs reveal toroidally aligned, effectively prolate dust grains large enough (at least $\sim 100$$\mu$m) to efficiently scatter millimetre light. The alignment mechanism for these grains remains unclear. We explore the possibility that gas drag aligns grains through gas–dust relative motion when the grain’s centre of mass is offset from its geometric centre, analogous to a badminton birdie’s alignment in flight. A simple grain model of two non-identical spheres illustrates how a grain undergoes damped oscillations from flow-induced restoring torques which align its geometric centre in the flow direction relative to its centre of mass. Assuming specular reflection and subsonic flow, we derive an analytical equation of motion for spheroids where the centre of mass can be shifted away from the spheroid’s geometric centre. We show that a prolate or an oblate grain can be aligned with the long axis parallel to the gas flow when the centre of mass is shifted along that axis. Both scenarios can explain the required effectively prolate grains inferred from observations. Application to a simple disc model shows that the alignment time-scales are shorter than or comparable to the orbital time. The grain alignment direction in a disc depends on the disc (sub-)structure and grain Stokes number (St) with azimuthal alignment for large St grains in sub-Keplerian smooth gas discs and for small St grains near the gas pressure extrema, such as rings and gaps.

Piezo Electric Properties of Epitaxial SiGe

Piezo resistivity of B- and P-doped epitaxial Si1-xGex (x=10-30%) is investigated to assess its application potential for thin film strain sensors. The gauge factor (GF) is calculated based on the change in resistivity to the externally induced compressive uniaxial strain along the current flow direction. In the case of B-doped SiGe, the resistivity decreases under the induced compressive strain which may be related to hole mobility enhancement, while no influence on the resistivity of the P-doped SiGe. A significant increase in the GF is observed by lowering B concentration. At the same B concentration, slightly higher GF is observed for higher Ge content. Moreover, the GF is slightly improved by lowering the SiGe growth temperature. The slight improvement may be related to improved crystallinity. These results suggest that the low-doped p-type SiGe deposited at low temperature has reasonable GF and can potentially be applied in strain sensors.

Numerical Investigation on Two-Phase Flow Pressure Drop in Cathode Channels of Proton Exchange Membrane Fuel Cells

As liquid water is produced by electrochemical reactions in a proton exchange membrane (PEM) fuel cell, liquid–gas two-phase flow forms within the porous structure of the electrodes and gas channels (GCs), resulting in complex gas pressure drop within GCs. This study investigates the two-phase flow pressure drop in a GC connected with a fibrous gas diffusion layer (GDL) using volume of fluid simulations. Fibrous GDLs are stochastically reconstructed to give a rather realistic liquid water breakthrough, and the effect of GDL straight and curved carbon fibers is studied. The results show that droplet breakthrough position and breakthrough size are dependent on the carbon fiber shape, resulting in further distinct pressure drop in GCs. It is also found that the two-phase flow pressure drop has no close correlation with the water content within the GC but a strong relationship with the liquid flow types. Specifically, the cross-section liquid area variation along the gas flow direction is found to be proportional to the pressure drop variation. This study aims to provide the information required for an accurate two-phase flow pressure drop prediction model.

Perceived travel distance depends on the speed and direction of self-motion.

Although estimating travel distance is essential to our ability to move through the world, our distance estimates can be inaccurate. These odometric errors occur because people tend to perceive that they have moved further than they had. Many of the studies investigating the perception of travel distance have primarily used forward translational movements, and postulate that perceived travel distance results from integration over distance and is independent of travel speed. Speed effects would imply integration over time as well as space. To examine travel distance perception with different directions and speeds, we used virtual reality (VR) to elicit visually induced self-motion. Participants (n = 15) were physically stationary while being visually "moved" through a virtual corridor, either judging distances by stopping at a previously seen target (Move-To-Target Task) or adjusting a target to the previous movement made (Adjust-Target Task). We measured participants' perceived travel distance over a range of speeds (1-5 m/s) and distances in four directions (up, down, forward, backward). We show that the simulated speed and direction of motion differentially affect the gain (perceived travel distance / actual travel distance). For the Adjust-Target task, forwards motion was associated with smaller gains than either backward, up, or down motion. For the Move-To-Target task, backward motion was associated with smaller gains than either forward, up or down motion. For both tasks, motion at the slower speed was associated with higher gains than the faster speeds. These results show that transforming visual motion into travel distance differs depending on the speed and direction of optic flow being perceived. We also found that a common model used to study the perception of travel distance was a better fit for the forward direction compared to the others. This implies that the model should be modified for these different non-forward motion directions.

Numerical Simulation Study on Evolution Process of Carrying-Soil Effect of Rectangular Pipe Jacking

The carrying-soil effect is an important factor affecting the success or failure of rectangular pipe jacking construction. Because it is difficult to explore the dynamic evolution process of the carrying-soil effect in the field test, this paper relies on the pipe jacking project of a comprehensive pipe gallery in Suzhou City, and uses ABAQUS 2021 finite element software to simulate the jacking process of rectangular pipe jacking. Based on the theory of plastic mechanics of rock and soil and the related research and application status, the equivalent plastic strain index is introduced as the basis for judging the failure boundary of soil in the numerical simulation results, and the boundary between the carrying-soil area and the surrounding soil is determined, that is, the shear fracture surface. According to the principle of plastic potential energy, the development direction of the fracture surface is consistent with the direction of plastic flow, so as to predict the development direction of the boundary of the carrying-soil area. According to the change in the equivalent plastic strain cloud map with the jacking mileage, the evolution process of the carrying-soil effect is clarified, and the dynamic evolution law of the carrying-soil area is revealed, which is of great significance for predicting the disturbance of the surrounding soil during the construction of rectangular pipe jacking and accurately evaluating the environmental effect of the construction.

Research on the Influence of Matrix Shape on Percolation Threshold Values for Current Flow Conducted Using the Monte Carlo Simulation Method

In this study, in order to determine the effect of matrices’ shape on the percolation threshold values, computer simulations were performed using the Monte Carlo method for a 200 × 200 square-shaped matrix and rectangular matrices containing the same number of nodes as the square matrix. Based on the simulations, the average values of the percolation thresholds and standard deviations for the current flow along and across the matrices were determined. It was determined that for a square-shaped matrix, the average values of the percolation thresholds in both directions of the current flow were the same. Extending the rectangular matrix while reducing its height causes the average value of the percolation threshold in the direction of the current flow along the matrix to increase from 0.592740 to 0.759847, while in the transverse direction, it decreases from 0.592664 to 0.403614. The values of the classical asymmetry coefficients of the probability distributions of the percolation thresholds for both directions of the current flow were determined. Histograms of the probability distributions of the percolation threshold values for a square-shaped matrix and rectangular matrices were made and compared with the normal distributions. It was found that the occurrence of two percolation thresholds in rectangular layers should be considered when analyzing the electrical conductivity measurements of nanocomposite thin films.

Flooding Hazard Vulnerability Assessment Using Remote Sensing Data and Geospatial Techniques: A Case Study from Mekkah Province, Saudi Arabia

Flash floods are catastrophic phenomena that pose a serious risk to coastal infrastructures, towns, villages, and cities. This study assesses the risk of flash floods in the ungauged Mekkah province region based on specific and effective morphometric and topographic features characterizing the study region. Shuttle Radar Topography Mission (SRTM) data were employed to construct a digital elevation model (DEM) for a detailed analysis, and the geographical information systems software 10.4 (GIS) was utilized to assess the linear, area, and relief aspects of the morphometric parameters. The ArcHydro tool was used to prepare the primary parameters, including the watershed border, flow accumulation, flow direction, flow length, and stream ordering. The study region’s flash flood hazard degrees were assessed using several morphometric characteristics that were measured, computed, and connected. Two different and effective methods were used to independently develop two models of flood vulnerability behaviors. The integrated method analysis revealed that most of the eastern and western parts of the studied province provide high levels of flood vulnerability. Due to it being one of the most helpful topographic indices, the integrated flood vulnerability final map was overlayed with the topographic position index (TPI). The integrated results aided in understanding the link between the general basins’ morphometric characteristics and their topographical features for mapping the different flood susceptibility locations over the entire studied province. Thus, this can be applied to investigate a surface-specific reduction plan against the impacts of flood hazards in the studied landscape.

A modified microscale viscosity model of polymer melts and experimental verification

AbstractDuring the micro‐molding of polymer melts, ensuring the viscosity models' accuracy was essential. Existing models had neglected the temperature dependence of microscale factor, rendering them unsuitable for materials with varying temperature sensitivities. This research employed a twin‐bore capillary rheometer and dies of distinct characteristic dimensions as the experimental setup to investigate the viscosity variations across four materials exhibiting diverse temperature sensitivities. A modified MCA viscosity model was established by integrating a microscale factor that accounted for both dimension and temperature dependence into the macroscopic Carreau viscosity model. The traditional MCAc model, which ignored the microscale factor's temperature dependence, offered a comparative reference. These models were subsequently applied to evaluate the influence of coupling effects between viscosity and viscous dissipation on melt temperature, with results compared to experimental data. The results indicated that the MCA model's viscosity forecasts were in closer accord with experimental measurements, maintaining an accuracy within a 16% margin. The models' application to temperature calculations under varying inlet velocities and temperatures confirmed that the MCA model's predictions of the temperature increase along the flow direction were more congruent with experimental outcomes, underscoring the critical importance of incorporating both dimension and temperature dependence when establish microscale viscosity models.