Mixed Flow Research Articles

Measuring Collision Risk in Mixed Traffic Flow Under the Car-Following and Lane-Changing Behavior

This study proposes a risk measurement approach to assess collision risks in mixed traffic flow, focusing on the integrated behavior of car-following and lane-changing. A new surrogate safety measure (SSM), denoted as Rtotal, is developed to provide a comprehensive risk assessment. Numerical analysis is used to determine the weights of parameters within Rtotal, and its validity is substantiated using an empirical dataset, with a risk threshold of 0.49 established when the time to collision (TTC) is set to 2 s. The study incorporates scenarios of connected and automated vehicle (CAV) degradation and evaluates the influence of penetration rates, perception–reaction time (PRT), and lane-changing modes on risk levels. Simulation results reveal that a CAV penetration rate between 0.4 and 0.6 represents a critical range where collision risks significantly increase, reflecting safety dynamics under CAV degradation. Furthermore, in scenarios involving lane-changing, the degradation of the following vehicle in the target lane poses the highest risk. At lower PRTs, the penetration rate exerts a more significant influence on collision risks. Rtotal has been validated across various scenarios, showing strong applicability and more sensitive trends than other SSMs, making it well-suited for assessing long-term comprehensive traffic flow risks. These findings offer practical guidance for traffic management to establish real-time risk prediction and warning systems for identifying high-risk car-following and lane-changing behaviors. Future research can explore the applicability of the proposed risk index in more complex traffic scenarios and its effectiveness across different levels of vehicle automation and connectivity.

Congo Red Dye Removal from Aqueous Solutions by Photocatalytic Redox Reactions Using Anatase Nano-TiO2 as a Heterogeneous Catalyst: Degradation Kinetics and Simulation Using Dispersion Model

Water pollution caused by Congo red as a textile dye is a significant concern for the aquatic environment. The photocatalytic redox reactions were carried out in a closed batch photoreactor using 0.2 g/L Anatase nano-TiO2 as a catalyst to remove different initial concentrations (32, 71, and 178 ppm COD) of the dye from its neutral aqueous solutions at 40℃. The air was supplied to the reactor as an oxygen source at a rate of 0.2 L/min. The COD removal values decreased with the increasing initial dye concentration, and the best removal value was recorded (89.47 %) for the lowest initial COD (32 ppm) after 255 minutes of radiation. The kinetics study showed that the Congo red dye removal followed a first-order reaction model. A mathematical model was developed based on the axial dispersion phenomenon to simulate the product distribution of the dye through several types of reactors (ideal and nonideal plug flow and mixed flow reactors). Effects of initial concentration, dispersion number, and space-time on the organic distribution through the reactors were studied and discussed. The simulated results show that the ideal plug flow reactor (zero dispersion) performance was better than that of the nonideal plug flow reactor, and the performance decreased with the increasing dispersion number and gave the worst performance in the mixed flow reactor (infinity dispersion).

Application of Resistance Ring Array Sensors for Oil–Water Two-Phase Flow Water Holdup Imaging in Horizontal Wells

Unconventional oil and gas reservoirs are frequently developed using inclined and horizontal wells, leading to intricate multiphase flow patterns due to spatial asymmetry surrounding the wellbore and gravitational differentiation effects. Through the examination of water holdup imaging, the spatial arrangement of oil and water phases within the wellbore may be clearly depicted, yielding critical information for precisely assessing the ratios of oil and gas. This study employed No. 10 industrial white oil and tap water as fluid media, with measurements obtained using a resistive ring array tool (RAT) to evaluate its response properties over the wellbore cross-section. The data gathered throughout the trials were analyzed by two-dimensional interpolation imaging utilizing 2020 version MATLAB software. To enhance the analysis of water holdup distribution in the wellbore, three interpolation algorithms were utilized: Simple Linear Interpolation (SLI), Inverse Distance Weighting Interpolation (IDWI), and Ordinary Kriging Interpolation (OKI). The results indicated that RAT operates effectively in medium and low flow circumstances, correctly representing the real distribution of oil and water phases while yielding more dependable water holdup data. The SLI algorithm effectively delineates the oil-water interface during stratified flow of oil and water phases, rendering it the optimal algorithm for determining water holdup in standard flow patterns. Under DW/O&W and DO/W&W flow patterns, SLI continues to perform well; however, the accuracy of IDWI and OKI markedly enhances, with IDWI more effectively delineating the attributes of intricate mixed flow and more precisely representing the dynamic fluid distribution. Under DW/O and DO/W flow patterns, the OKI algorithm exhibits optimal performance in these intricate dispersed flow patterns. OKI more precisely represents the dynamic distribution of dispersed oil and water due to its capacity to simulate the spatial correlation of both phases, surpassing both SLI and IDWI.

Inertia-induced mixing and reaction maximization in laminar porous media flows

Solute transport and biogeochemical reactions in porous and fractured media flows are controlled by mixing, as are subsurface engineering operations such as contaminant remediation, geothermal energy production, and carbon sequestration. Porous media flows are generally regarded as slow, so the effects of fluid inertia on mixing and reaction are typically ignored. Here, we demonstrate through microfluidic experiments and numerical simulations of mixing-induced reaction that inertial recirculating flows readily emerge in laminar porous media flows and dramatically alter mixing and reaction dynamics. An optimal Reynolds number that maximizes the reaction rate is observed for individual pore throats of different sizes. This reaction maximization is attributed to the effects of recirculation flows on reactant availability, mixing, and reaction completion, which depend on the topology of recirculation relative to the boundary of the reactants or mixing interface. Recirculation enhances mixing and reactant availability, but a further increase in flow velocity reduces the residence time in recirculation, leading to a decrease in reaction rate. The reaction maximization is also confirmed in a flow channel with grain inclusions and randomized porous media. Interestingly, the domain-wide reaction rate shows a dramatic increase with increasing Re in the randomized porous media case. This is because fluid inertia induces complex three-dimensional flows in randomized porous media, which significantly increases transverse spreading and mixing. This study shows how inertial flows control reaction dynamics at the pore scale and beyond, thus having major implications for a wide range of environmental systems.

Determination of Experimental Characteristics of a Jet-vortex Pump

A methodology has been developed and the results of experimental studies of high-pressure jet-vortex pump models with a mixing chamber and working nozzle area ratio of 3.429 and 3.795 have been obtained. In the flow part of the pump, inclined guide elements for swirling the mixed flows are installed. An increase in the velocity of swirling screw jets increases the level of turbulence, intensifies the energy exchange of the mixed media, and improves the conditions for transferring kinetic energy from the working flow to the injected one. Improvement of the flow mixing mechanism allows increasing the energy efficiency of jet pumps. The velocity of swirling screw jets is determined by the angle of inclination of the guide elements and the flow rate of the mixed flows. The efficiency of simultaneous swirling of the mixed media may be less than the efficiency of swirling a separate flow if there is a difference in the directions of the velocity vectors of the swirling jets. There has been obtained the dependence of the injection coefficient on the Reynolds number of the working flow, pressure and energy characteristics for a straight-through jet pump for the case of swirling of the exclusively injected flow and simultaneous swirling of the working and injected flows. According to the results of the conducted studies, an increase in the injection coefficient, relative pressure and efficiency caused by swirling of the mixed flows was established by 26.34%, 19.43% and 23.75%, respectively.

Analysis of Hydrothermal Flow and Performance of Heat Transfer in 3D Pipes Based on Varying Dimple Structure Configurations

ABSTRACTIn the current work, the study examines the flow patterns and heat transfer capabilities of tubes with various spherical dimple configurations. A numerical analysis, supported by experimental validation on a reference model, was conducted on a circular tube with an alternating flow path. The primary goal was to enhance the thermal performance of circular tubes by inducing mixing and vortex flows. The impact of three design factors on thermal–hydraulic performance was investigated, dimple pipe diameter (DPD), dimple group number (DGN), and number of dimples (NODs). Dimpled tubes consistently outperformed smooth tubes in heat transfer due to increased flow mixing and separation. Both increasing the Reynolds number and decreasing the design factors led to the formation of mixing and vortex patterns. The performance evaluation factor (PEF) varied across different dimple configurations. For DPD, PEF ranged from 1.14 to 1.33; for DGN, it ranged from 1.15 to 1.28; for NOD, it ranged from 0.95 to 1.21, all within a Reynolds number range of 4000–15,000. At a Reynolds number of 6000, all three configurations of DPD, DGN, and NOD outperformed the smooth pipe in terms of the Nusselt number. For DPD, Nusselt number improvements ranged from 25.7% to 30.8%, and friction factors increased by 21% to 67%. DGN configurations exhibited a wider range of Nusselt number enhancement from 25% to 49.6%, and friction factor increase from 37% to 72%. NOD configurations also demonstrated consistent improvements, with Nusselt number increases ranging from 27.35% to 31% and friction factor increases from 42% to 74%. Spherical dimples can significantly enhance the thermal–hydraulic performance of tubes, so the best configuration depends on the specific application, and the highest performance, with a 1.33 increase in PEF, was achieved with a dimple diameter of 2 mm (DPD = 2 mm) and a dimple density of four dimples per unit area (NOD = 4).

Mechanisms of mixed slurry flow of deep-sea hydrate exploitation

Marine gas hydrate test production faces several challenges, including low hydrate yield, severe sand sedimentation under jet-breaking conditions, and minimal or even absent fluid returns. To address these challenges and enhance gas hydrate production while maximizing the value of extraction equipment, a layered control engineering strategy is proposed. This strategy is based on the integrated vertical development approach encompassing natural gas hydrates, shallow gas, and natural gas reservoirs. Using a gas-liquid two-phase flow theory and considering both the self-dissociation behavior of hydrates and the effective transport conditions of solid-phase particles, a mathematical model for slurry lifting across different extraction stages was established. The model was solved and validated, ultimately producing a process flow diagram for natural-assisted lifting of hydrate slurry. During the horizontal drilling phase, effective transport of solid-phase particles can be achieved without additional gas injection when the drilling fluid flow rate exceeds 13 L/s. However, gas injection can be used to further accelerate solid particle transport, with an injection range of 0 to 67 L/s, depending on the drilling fluid input. During the hydrate fracturing and recovery stage, solid particle transport can be effectively maintained without additional gas injection when the fracturing flow rate is between 49 and 55 L/s. Within this range, gas injection can be adjusted from 0 to 129 L/s to meet the requirements of hydrate slurry flow. This research provides a reference for improving gas hydrate extraction yield, accelerating early commercialization of hydrate exploitation, and supporting China's “dual carbon” strategic goals.

Application of oscillating elastic surfaces for heat transfer enhancement from heat dissipating electronic chips

The present study investigates the possibility of heat transfer enhancement from discrete heat sources by an oscillating elastic surface. The three liquid cooled heat sources are located on the bottom surface of a rectangular channel and are influenced by oscillation of the upper surface. Finite element simulations are carried out at several Reynolds numbers in the laminar flow regime for two different cases of oscillation by cosine and step loads with various periods and amplitudes. It is observed that oscillation of the channel surface alters the direction of the pressure gradient and causes backflow and several vortices along the channel. It also leads to the thermal boundary layer disturbance and flow acceleration on the heat sources and consequently intensifies the heat transfer. Results indicate that reducing the period of the oscillations improves the flow mixing and thus increases the heat transfer rate to an optimum value. Further decrease in the period has a reverse effect on the heat transfer enhancement. Maximum heat transfer enhancement of 223.4 %, 162.2 %, 137.8 %, and 150.5 % are obtained for Reynolds numbers of 200, 600, 1000, and 1400, respectively. It is worth mentioning that the heat transfer enhancement is achieved at the expense of a considerable pressure drop increase. The overall performance factor implies that the heat transfer enhancement dominates the pressure drop increase only at low amplitudes and periods of oscillations. Comparison between the cosine and step loads reveals that the cosine and step forces exhibit better heat transfer performance at low and high periods, respectively.

Levenberg–Marquardt back-propagation algorithm for a developing unsteady hybrid nanofluid mixed convective flow across a revolving sphere: irreversibility analysis

Levenberg–Marquardt back-propagation algorithm for a developing unsteady hybrid nanofluid mixed convective flow across a revolving sphere: irreversibility analysis

The Impact of Variable Viscosity and Variable Thermal Conductivity on the Mixed Convective Flow of Casson Nanofluid in a Channel with Chemical Reaction

A theoretical analysis has been conducted on the mixed convective Casson nanofluid flow in a vertical channel that contains a first-order chemical reaction. The energy equation takes into account the combined effects of variable viscosity and variable thermal conductivity and the viscous dissipation. Nanofluids have different nanoparticles such as Aluminum oxide (), Copper (), Silver (), Titanium oxide () and Iron oxide () are suspended nanoparticles in water () and Ethylene Glycol () as base fluids. The governing equations are solved by perturbation method analytically like the momentum, energy, and diffusion equations, semi-numerically using differential transform method and numerically using BVP5C method. The obtained numerical values are agreed well for all the three methods and is shown in tabular form. For each of the several governing factors, the contours of velocity, temperature, and concentration are shown graphically. Additionally, data is tabulated for skin friction, Nusselt number. The results found that the silver nanoparticles enhance the thermal conductivity considerably in the flow. The variable viscosity regulates the flow while the variable thermal conductivity suppresses the flow.

Numerical computations of magnetohydrodynamic mixed convective flow of Casson nanofluid in an open-ended cavity formed by earthquake-induced faults

Numerical computations of magnetohydrodynamic mixed convective flow of Casson nanofluid in an open-ended cavity formed by earthquake-induced faults

Outlining the impact of electro-osmotic force and mixed convection flow of EMHD nanofluid flow on the stretched cylinder: a computational layout

Abstract This research has focused on studying the electro-magneto-hydrodynamic (EMHD) nanofluid flow over a stretched cylinder in the presence of electro-osmotic force and mixed convection. This inquiry shows a novel approach through the use of thermophoresis and Brownian motion and nanofluid is comprised of water and copper nanoparticles. Similarity transformations simplified the mathematical model and produced nonlinear ordinary differential equations with suitable boundary conditions, which the MAPLE-21 software numerically solved using the RK-4 shooting criteria. Tables and graphs have been used to illustrate the impact of the key flow factors on Electric potential profiles, velocity profiles, temperature outlines, and concentration distribution. Following the physical deliveries, we have calculated the Sherwood number, Nusselt number, and skin friction. The electro-osmotic parameter diminishes the electric potential profiles and a dual effect occurs for the curvature parameter. The Nusselt number declined by 5.91 % for the electro-osmotic parameter but the Sherwood number enhanced by 30.7 % at a rate. The practical applications of this model shed light on thermal management in electronics and nuclear reactors, plasma physics, various chemical processes, filtration, separation, and fuel cells, as well as the manipulation of biological fluids in lubrication or medical devices.

Real-time executable platoon formation approach using hierarchical cooperative motion planning framework

While connected and automated vehicle (CAV) platooning holds promise for enhancing traffic efficiency and reducing energy consumption, we still lack efficient algorithms for guiding the local movements of CAVs to form a platoon on a road due to significant computational and control challenges. This study addresses this gap by designing a real-time executable Hierarchical and Recursive Platoon Formation (HR-PF) framework tailored to mixed flow traffic conditions that encompass both Human-Driven Vehicles (HDV) and CAVs. The HR-PF framework comprises three hierarchical mathematical models (modules) designed to optimize platoon formation while considering both macroscopic traffic conditions and microscopic traffic safety. Module-I formulates a mixed integer quadratic program to determine the timing, location, and state of platoon formation. It is further extended to a mixed integer nonlinear program so that we can also select the optimal size of the target platoon. Module-II designs a Hybrid State-Lattice Motion planner to generate optimal trajectory references for CAVs to approach the target platoon state, ensuring microscopic traffic safety. Module-III develops longitudinal and lateral controllers to enable CAVs to track trajectory references accurately. These models function recursively at varying frequencies to balance mathematical rigor with practical application. Numerical experiments demonstrate that HR-PF facilitates efficient platoon formation in real-time across diverse traffic scenarios and road geometries while sustaining traffic efficiency. Furthermore, the performance of platoon formation is affected by surrounding traffic density and CAV penetrations, with prompt formation observed under LOS C and D traffic environments and slightly more traffic impacts under LOS E and F. These findings provide robust support for exploring advanced platoon formation and platooning strategies for CAVs under complicated traffic environments.

Unsteady Flow Mechanism of Corner Separation Control Using Blade End Slots in a Highly Loaded Compressor Cascade

Abstract Blade end slots has been proved to be an effective method to suppress the corner separation, thereby improving the aerodynamic performance of compressor. The unsteady effects of blade end slots affiliated with a highly-loaded compressor cascade on corner separation control are investigated based on delayed detached eddy simulation under the Mach number of 0.59. The corner separation vortex structures between the datum blade and the end slotted blade are compared. The vortex topologies are markedly reorganized and suppressed by the blade end slots. Unsteady flow behaviors of separation vortex and the corresponding dynamic mechanisms are analyzed in both time and frequency domains. The interaction of the self-adaptive jet flow from the blade end slots to the corner separation flow results in smaller-scale vortices in the blade end region with a higher characteristic frequency. Consequently, the unsteady effects caused by corner separation vortices are significantly reduced in range and intensity through the enhancement of flow mixing and the rapid dissipation of corner separation vortices into larger-scale lower-frequency features. Furthermore, spatiotemporal features and dynamics of corner separation flow with blade end slot control are investigated using the enhanced dynamic mode decomposition method. Results show that the dominant unsteady flow behavior develops with better stability, and the intermittency of low-frequency and large-scale behavior is reduced via the blade end slot control.

Analysis of irregular heat source/sink of a stagnation-point flow toward a vertical plate induced by spherical hybrid nanofluids

Heat transfer technology is quickly increasing as a result of the demand for well-organised heating and cooling systems (HGS and CGS) in the necessary chemical, automotive, and aerospace sectors. Thus, the current study aims to observe mixed convective flow of a Williamson fluid near the stagnation point in the presence of hybrid nanoparticles (Al2O3 and Cu) across a vertical flat plate with the Hall effect. The water-based alumina (Al2O3) and copper (Cu) nanoparticles that have been convectively heated are evaluated for their suitability in industry. The primary equations are non-dimensionalized employing the relevant similarity factors before being solved numerically by the bvp4c solver in MATLAB software. We examine the impacts of several pertinent parameters on transverse and axial velocities, drag force, temperature, and heat transfer. In the case of opposing flow, two different outputs are obtained, whereas just one is procured in the case of assisting flow. The impact of Lorentz force can also be used to alter the flow and physical properties of heat transfer.

Capacity modeling for mixed traffic with connected automated vehicles on minor roads at priority intersections

ABSTRACT As connectivity technology advances, connected automated vehicles (CAVs), connected vehicles (CVs), and regular vehicles (RVs) form mixed traffic traffic at priority intersections. This paper presents an analytical capacity model to evaluate the impacts of such mixed flow on minor roads. We define two platoon types based on the leading vehicle: CAV-led and CV/RV-led platoons. Assuming headway distribution on the major roads follows the M3 distribution, we derive probabilities of these platoons passing through the intersection during a single time gap on a major road. According to the expected probabilities of different vehicle types, the probabilities of these two types of platoon configurations are obtained. Based on this, we establish a mixed traffic capacity model. The capacity model’s effectiveness is validated through numerical experiments. The results demonstrate that the proposed model can analyze the impacts of key factors on mixed traffic capacity, including CAV penetration rate, CV proportion, traffic volume on major roads, and vehicle headway. HIGHLIGHTS Propose an analytical capacity model for mixed traffic on minor roads at priority intersections. Conduct numerical experiments to validate the effectiveness of the proposed mixed traffic capacity model. The proposed model can be applied to evaluate the capacity impacts of connected automated vehicle penetration rate, connected vehicle proportion, traffic volume on major roads, and vehicle headway at priority intersections.

Experimental and simulation study of pounding tuned mass damper on jumper flow induced vibration

Subsea jumpers carrying gas-liquid mixed flows can experience flow-induced vibration (FIV), potentially shortening their service life. The pounding tuned mass damper (PTMD), impact at the viscoelastic boundary can be used to dissipate energy. This paper focuses on a rigid m-shaped jumper to evaluate the specific damping effects of PTMD on the jumper under gas-liquid flow. Three PTMD configurations with significant damping effects are tailored based on the natural frequency of the jumper. Vibration tests are carried out to assess the damping effectiveness of each configuration, and the most effective PTMD is selected. Subsequently, the damping efficacy of PTMD on FIV within the jumper under varying flow conditions is investigated using both experimental methods and numerical simulations (VOF and FIS model). The results show that PTMD has obvious damping effects on free vibration and the main frequency and high-frequency jumper vibrations caused by FIV. Subsequent to the installation of PTMD, a substantial reduction in displacement has been observed across all components of the jumper. The suspension span exhibits the most pronounced decrease, exceeding 60%, while the displacement at the elbow joint is reduced by over 40%.

Analytical Investigation on Flow Reversal in a Fully Developed Steady Mixed Convection Flow With Boundary Condition of the Third Kind

ABSTRACTThis work presents exact solutions to analyze the effect of the Biot number on mixed convection flow in a vertical channel with asymmetric heating and flow reversal. The equations governing flow formation and temperature distributions are offered with convective boundary conditions. Closed‐form solutions for temperature, velocity, and skin friction are found and simulated graphically.

Developing a jam-absorption strategy for mixed traffic flow at signalized intersections using deep reinforcement learning

ABSTRACT Jam-absorption driving (JAD) can effectively prevent the generation and propagation of traffic oscillation. To alleviate the traffic congestion in the signalized intersection with mixed traffic flow, including human driving vehicles (HDVs) and connected and automated vehicles (CAVs), this study provides a jam-absorption driving strategy based on the traffic delay prediction of the mixed platoon under traffic congestion. An online traffic congestion prediction method with the objective of JAD is proposed and focuses on the leaving state of the trajectory to achieve fast capture of congestion features. Then, with real-time status and prediction information, we develop a Jam-absorption driving strategy based on a deep reinforcement learning (DRL) model to improve adaptability to the mixed traffic environment. The results show that this strategy can suppress more than 70% of traffic oscillations with excellent execution efficiency, improving traffic safety and efficiency.

Numerical study of an electrically conducting nanofluid flow past a vertical stretching Riga plate

The heat and mass transfer through electrically conducting and mixed convective nanofluid flow across an elongating Riga plate is studied. Riga plate is an electromagnetic sheet, in which electrodes are assembled alternatively. The arrangement of Riga plate produces electromagnetic behavior in the fluid flow. In the current analysis, the influence of Arrhenius activation energy, viscous dissipation and heat source/sink over the surface of Riga sheet is considered. The heat and mass transfer are examined by convective boundary conditions and nanoparticles (NPs) zero-mass flux. The Brownian motion and thermophoretic diffusion of fluid molecules are applied via Buongiorno's approach. Von Karman's similarity approach is implemented to reset the modeled equations into the dimensionless form of ordinary differential equations (ODEs). The system of ordinary differential equations is solved numerically via PCM (parametric continuation method). The fluid velocity, temperature field, and concentration gradients are analyzed by varying various flow parameters and graphically portrayed. The numerical results are validated by comparing them with the published studies. It can be resolved form the results that the flow rate decilnes with the effect of power index m, whereas enhances with the consequence of Hartmann number. The significance of thermophoresis term augments the temperature curve of the fluid.