Mixed Flow Research Articles

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.

Evaluating the mixed convection flow of Casson fluid from the semi-infinite vertical plate with radiation absorption effect

This study examines a steady laminar Casson fluid flow induced by a semi-infinite vertical plate under the impact of the Darcy-Forchheimer relation and thermal radiation. The features of mixed convection, cross-diffusion, radiation absorption, heat generation, chemical reactions and viscous dissipation are also considered to explain the transport phenomenon. The resultant system of equations, concerned with the problem under consideration, is transformed into a group of non-linear ordinary differential equations (ODEs) by means of similarity variables. The bvp4c method, an instrument popular for its numerical accomplishments, is utilized to solve this problem. The effect of flow parameters on heat transfer, concentration and velocity is evaluated via diagrams. To validate our code, we have compared the present outcomes to the prevenient literature, and stable consent has been detected. Moreover, the friction coefficient Cfx, Nusselt number Nux, and Sherwood number Shx are also computed to assess velocity gradient, efficiency of heat transfer and mass transfer process, respec-tively.

Temperature-dependent density effects on oscillatory mixed convective flow across a non-conducting horizontal circular cylinder embedded in a porous medium

Temperature-dependent density and aligned magnetic field influence on mixed thermal convection heat and current density aspects over a non-conducting porous circular horizontal cylinder is the novelty of this investigation. The magnetic effects over the surface are minimal but maximum away from the surface. The density of the fluid is assumed as an exponential variable of temperature to record the heat and current density rates. The pertinent form of partial differential equations is designed using suitable dimensionless quantities. The computational outputs of fluid velocity, magnetic fields and temperature variations are drafted using fluctuating-stokes quantities. The primitive quantities are utilised to make similar and asymptotic programs in FORTRAN for geometrical and numerical outcomes. The transient and oscillating behaviour of gradient values is sketched by using steady results in the oscillating formula. The finite difference methodology is applied to examine the physical properties with the Gaussian elimination matrix scheme. Effects of buoyant force ( λ ), Prandtl (Pr), magnetic force ( ξ ), density factor ( m ) and MHD Prandtl factor ( γ ) on the thermal behaviour of magneto-hydrodynamic analysis are applied. Results are explored around three angles π / 6 , π / 3 , π of the cylinder. Increasing magnitude in fluid velocity is deduced with high amplitude as porosity, buoyant and density parameters are enhanced.

Validation through internal flow physics of response surface methodology optimized mixed flow pump as turbine

In order to determine the optimal working efficiency of mixed flow pumps as turbine (MF-PAT) under a design condition of 10m3kw, this study takes the number of blades, blade wrap angle, impeller outer diameter, and impeller inlet width as design variables. Based on the center combination design method, experimental scheme design is carried out, and the head, shaft power, and efficiency of the turbine are used as evaluation indicators. A response surface model is constructed for optimization analysis, and the optimal geometric parameter combination of the impeller for MF-PAT is determined. For MF-PAT with forward-curved blade impeller in this paper, the optimal parameter combination is recommended as blade number Z = 6, blade wrap angle α = 47°, impeller outer diameter D2 = 140 mm and impeller inlet width b2 = 34 mm. The results show that compared with the original scheme, its efficiency has increased by 7.8 %. The established response surface model can reflect the relationship between evaluation indicators and design variables, and can be used for optimizing the geometric parameters of MF-PAT impellers. It can effectively enhance the blade's constraint ability on liquid flow, reduce hydraulic losses, and improve the performance of MF-PAT. Apply the ns-ds methodology for this and future mixed flow optimized pumps as turbines.

The effects of communication topology on mixed traffic flow: modelling and analysis

This paper aims to evaluate the combined impact of the communication topology (CT) and vehicular spatial distribution (SD) on mixed traffic of human-driven vehicles (HDVs) and connected and autonomous vehicles (CAVs). A generalized car-following (CF) model is presented to capture mixed traffic dynamics, integrating the effects of the CT, human reaction time, information delay and the optimal velocity changes with memory. Then, the linear stable condition of the model is derived using the perturbation method. Finally, extensive simulations are conducted under different CTs (i.e., multiple-predecessor leader following (MPLF) topology, predecessor following (PF) topology, and predecessor-leader following (PLF) topology) and six kinds of SDs. The results reveal that the MPLF topology demonstrates the best steady performance (i.e., stability) and dynamic performance (i.e., smoothness), and that the SD where CAVs are concentrated at the front of the traffic flow shows superior dynamic performance.

Parametric influences on flow, heat transfer, and nutrient transport in the knee joint cavity, a numerical approach

A novel aspect of this study is the investigation of the impact of temperature-dependent Arrhenius reactions and metabolic heat generation on the overall heat transfer within a knee joint cavity. This is a unique contribution where the interaction between thermal effects and metabolic activity is shown to influence the transport of nutrients and the removal of waste products. For the first time, the study also aims to examine the influence of key non-dimensional numbers on the characteristics of mixed convection flow, providing new insights into the dominant physical mechanisms at play. An innovative feature of the model is the incorporation of a non-linear reaction term to address the balance between protein synthesis and degradation. By integrating both thermal and biochemical dynamics, this approach offers a comprehensive analysis of protein aggregation in the knee joint, with potential implications for understanding and treating joint diseases, particularly those related to the health of synovial fluid and cartilage, such as osteoarthritis. The findings have the potential to inform the development of improved therapeutic strategies for managing these conditions. In the context of knee joint cavity dynamics, a low Cauchy number Ca plays a crucial role in ensuring steady and laminar flow, which reduces inertia and ensures that the continuity equation is satisfied. This laminar nature of the flow is essential for maintaining stable synovial fluid movement within the cavity, which aids in the smooth transport of nutrients and waste products. Additionally, higher Peclet number Pe values indicate an increased dominance of convective transport over diffusion, thereby enhancing the supply of essential nutrients to cartilage and bone, while also facilitating the removal of waste products and inflammatory mediators. This efficient convective transport mechanism is vital for the overall health of the joint and for mitigating inflammation. Furthermore, the Zeldovich number β significantly influences the temperature sensitivity of the Arrhenius reaction term within the cavity, where higher values reflect increased reactivity to temperature changes. This temperature dependence impacts metabolic heat generation and protein dynamics, further influencing the biochemical processes that occur within the joint. Collectively, these non-dimensional parameters highlight key aspects of synovial fluid dynamics, nutrient transport, and biochemical reactions that are essential to the functioning and health of the knee joint.

Analysis of fluid forces impacting on the impeller of a mixed flow blood pump with computational fluid dynamics.

This study presents four different impeller designs to compare hydrodynamic forces. Numerical simulation studies are performed via computational fluid dynamics to specify and investigate the hydraulic forces impacting the impeller of the mixed-flow blood pump with a volute. The design point of this pump is that the flow rate is 5 L/min, the rotational speed is 8000 rpm, and the manometric head is 100 mmHg. The designed impellers are placed in the same volute and simulation studies are performed with the same mesh size (17.3 million cells) of the pumps. The simulation studies have been conducted in setting 1050 kg/m3 blood density, 35 cP fluid viscosity, and SST-kω turbulence model. Additionally, this study examines the changes in hydraulic forces and hydraulic efficiency with fluid viscosity. As a result of experimental simulation studies, the highest hydraulic efficiencies of 40.87% and 39.5% are achieved in the case of the shaftless-grooveless and shafted-grooveless impeller, respectively. The maximum axial forces are obtained from the pump with the shaftless-grooveless impeller. Whereas radial forces, maximum values are calculated in the pump with the shaftless-outer groove impeller for all flow rates. Finally, the wall shear stresses, which are important for blood pump designs, are evaluated and the maximum value of 227 Pa is observed in the pump impeller with a shaftless-grooved.

MHD Mixed Convection Boundary Layer Casson Nanofluid Flow over an Exponential Stretching Sheet

This paper investigates the effects of radiation, internal heat source and magnetohydrodynamics (MHD) on the mixed convective boundary layer flow of a Casson nanofluid within a porous medium that is saturated and subject to an exponentially stretching sheet. The nanofluid model incorporates Brownian motion and thermophoresis, and the Darcy model is employed for the porous medium. By applying an appropriate similarity transformation, the nonlinear governing boundary layer equations are converted into a set of nonlinear coupled ordinary differential equations. These equations are then solved numerically using the Hermite wavelet method, with simulations conducted through the MATHEMATICA programming language. The analysis covers various aspects including temperature distribution, velocity, solute concentration and several engineering parameters such as skin friction coefficients, the Nusselt number (rate of heat transfer) and the Sherwood number (rate of mass transfer), all evaluated based on dimensionless physical parameters. The results indicate that elevated radiation intensifies temperatures and leads to thicker thermal boundary layers. As the Casson parameter increases, both the velocity and the momentum boundary layer become narrower. Additionally, a more pronounced chemical reaction rate reduces the thickness of the solutal boundary layer. The accuracy and reliability of the numerical Hermite wavelet method are validated through a comparative analysis with previous studies, demonstrating excellent concordance and confirming the robustness of the computational approach.

A novel relaxed modified pipe hydrodynamic model for mixed flow simulation

In this study, we propose a novel modified pipe hydrodynamic model with a partial relaxation approach and develop a corresponding numerical algorithm within the framework of the finite volume method for its computation to enable robust, accurate, and comprehensive pipe modeling. The proposed numerical model provides some key improvements compared to existing numerical schemes for simulating mixed pipe flows: (1) it is capable of preserving both moving- and stationary-water steady states, and (2) it effectively reduces post-bore oscillations while maintaining second-order accuracy in the non-pressurized regime for unsteady pipe flows. Such improvements have been verified against theoretical and experimental data through tests involving both smooth and sharp-gradient steady and unsteady flows across various regimes in straight and locally bent circular pipes, which are fundamental elements of stormwater drainage, sewage networks, and industrial process pipelines. The proposed pipe flow model can be further improved regarding post-pore stability by utilizing specific post-bore oscillation suppression techniques, and it can be integrated into a practical hydraulic modeling tool for pipeline networks in future work.

Effects of electric and magnetic fields in magnetic mixing in electroosmotic flows

In this paper, mixing efficiency in electroosmotic flow is numerically simulated at the electric double layer region in the presence of a magnetic field. An incompressible and laminar model is adopted to numerically solve the governing equations involving the magnetic field, electric potential fields, concentration distribution for positive and negative ions (Nernst–Planck), and species concentration. To validate the numerical study, an ideal electroosmotic flow with charged walls is simulated and the results are compared with the analytical solution. For the case with a Reynolds number of 0.02, microchannel length of 40 μm, the results show that by applying a magnetic field, the mixing efficiency along the microchannel length increases from 60.5% to 79.67%. It is found that the existence of a magnetic field in the electric double layer has a significant impact on pressure distribution along the microchannel wall, however, its effects on the electric fields (internal and external), the distribution of positive and negative ions, and the net electrical charge density are marginal. In addition, the presence of magnetic field creates two relatively large vortices inside the microchannel. The outcomes of the present study will help to improve mixing efficiency in micro-devices with applications in micro-analysis systems and lab-on-a-chip instruments.

Radial Mixing in Steady and Accelerating Pipe Flows

Radial Mixing in Steady and Accelerating Pipe Flows

Development of a 3D Printed Chemiluminescence Smartphone Detector for High Performance Liquid Chromatography

A novel chemiluminescence detector for high-performance liquid chromatography (HPLC) was designed that incorporates a smartphone as photodetector, signal processor, and data storage unit. All detector components, including flow cell, flow cell holder, mixers, and housing, were fabricated by 3D printing and integration of the smartphone and 3D printed components provides a portable, low-cost, and user-friendly device. The detector was applied in the determination of carbamazepine using HPLC through a chemiluminescence reaction with tris(2,2′-bipyridyl)ruthenium(II) and cerium sulfate. Design and fabrication of the flow cell using two fabrication methods—3D printing and laser cutting—along with the integration of a mixer and the optimization of smartphone parameters were investigated. To expand the applicability of the detector for other analytes and different chemiluminescence reactions, detection of three piperazine derivatives by reaction with tris(2,2′-bipyridyl)ruthenium(II) and four phenethylamine compounds via reaction with acidic potassium permanganate reagent was studied. The linear dynamic range, limit of detection, and limit of quantification of the detector for the determination of carbamazepine were measured as 3.0–30.0 mg/L, 1.0 mg/L, and 3.0 mg/L, respectively, using the Samsung S20 smartphone device. Intraday and interday precision was evaluated for carbamazepine, with relative standard deviation (RSD) values for intraday precision ranging from 1.7% to 6.2% (n = 3) and interday precision RSD values ranging from 3.2% to 4.8% (n = 9).

Laser ablation ignition modes in a cavity-based supersonic combustor

A numerical and experimental study was conducted to investigate the Laser Ablation (LA) ignition mode in an ethylene-fueled supersonic combustor with a cavity flameholder. The experiments were operated under a Mach number 2.92 supersonic inflow, with stagnation pressure of 2.4 MPa and stagnation temperature of 1600 K. Reynolds-averaged Navier-Stokes simulations were conducted to characterize the mixing process and flow field structure. This study identified four distinct LA ignition modes. Under the specified condition, laser ablation in zero and negative defocusing states manifested two distinct ignition modes termed Laser Ablation Direct Ignition (LADI) mode and Laser Ablation Re-Ignition (LARI) mode, correspondingly. LA ignition in a local small cavity, created by depressing the flow field regulator, could facilitate the ignition mode transforming from LARI mode to Laser Ablation Transition Ignition (LATI) mode. On the other hand, the elevation of the flow field regulator effectively inhibited the forward propagation of the initial flame kernel and reduced the dissipation of LA plasma, further enhancing the LADI mode. Based on these characteristics, the LADI mode was subdivided into strong (LADI-S) and weak (LADI-W) modes. Facilitating the transition of ignition modes through alterations in the local flow field could contribute to attaining a more effective and stable LA ignition.

Bioconvection across a revolving sphere under the influence of bilateral chemical reactions with temperature- and space- dependent heat generation

This paper discusses the time-dependent mixed convection flow of nanofluids (Al2O3-water) due to a stagnation-point over a rotating sphere in the presence of motile microorganisms. The suspension is considered to be electro-conducting and Joule heating impacts are not neglected. Exponential behaviors are considered for the included heat generation and chemical reaction influences. Besides, the non-linear radiation flux takes place in the flow area. Computational analyses are introduced for the problem formulations after converting them to similar forms. From the major results, the exponential heat generation enhances the temperature distributions while the exponential behaviors of the chemical reaction have negative influences on the nanoparticle concentration. Also, the skin friction coefficients in x− and z−directions get higher values when the rotational and the mixed convection parameters are rising. Further, the thermal scenario diminishes with increasing nanoparticle diameter, however the thermal radiation factor and the ratio between the liquid and the nanolayer conductivity significantly enhance the thermal characteristics of the water-based Al2O3 nanofluid. The findings offer practical information that might be applied to improve system performance in a number of fields, which could involve fluid mechanics, pharmaceutical technology, and thermal management, among others.

Numerical Study of Double-Diffusive Mixed Convection Flow in Channel with Hybrid Nanofluid in Porous Medium

Numerical Study of Double-Diffusive Mixed Convection Flow in Channel with Hybrid Nanofluid in Porous Medium

Systematic analysis of mixing and segregation patterns of binary mixtures in fluidised beds for multi-functional processes

Fluidized beds are increasingly used in renewable energy and chemical production due to their versatility in handling different solids for multi-functional industrial applications. The diversity in size and density of solid particles impacts fluidization, influencing mixing and segregation behaviours critical for optimizing chemical processes and reactor design. This study investigates the expansion and segregation behaviours of mixed Geldart group powders in binary systems, simulating polydispersed beds with different materials and catalysts. By applying a modified Cheung equation and an adapted Gibilaro-Rowe model, the study analyzes segregation behaviours of Geldart Group A and B materials at varying mixing rates and gas flow velocities. Results show a good match between experimental data and model predictions. Using novel non-invasive X-ray imaging, the study provides real-time analysis of mixing and segregation at different fluidization regimes and temperatures. These findings aid in designing and optimizing advanced thermochemical conversion technologies, enhancing process efficiency and resilience.

Combustion performance of an evaporative flameholder under subsonic-supersonic mixing inflow

The combustion process in rocket-assisted subsonic ramjet engines represents a key advancement in integrated aerospace propulsion, particularly for embedded rocket-based systems. These engines offer the potential to improve combustion performance at altitudes of 25–35 km. However, the significant temperature and velocity differentials between the rocket jet and the subsonic ramjet flow restrict heat and mass transfer. Investigating the relationship between combustion performance and inlet parameters under subsonic-supersonic mixing conditions offers a promising approach to enhancing thrust performance. This study introduces subsonic and supersonic airflow mixing via a flat-plate shear layer in a rectangular channel, with an evaporative flameholder placed centrally to assess combustion. Results reveal that combustion efficiency decreases as the equivalence ratio exceeds 0.2, while the static temperature ratio has minimal impact on efficiency but strongly influences the maximum flame stabilization limit. As the temperature ratio increases from 1.30 to 1.80, the flame limit narrows from 1.656 to 0.237. Higher pressure ratios initially enhance combustion efficiency and flame coverage but eventually cause a decrease. The flame limit broadens from 0.900 to 1.626 as the pressure ratio increases from 1.12 to 1.50. While Mach number changes have little effect on efficiency, the flame limit exhibits an initial rise followed by a drop. Novel findings include an asymmetrical flame pattern and a “Z” shaped outlet temperature distribution, contributing to optimized combustion strategies for combined-cycle engines.

Research on oil-water mixed-phase flow measurement method based on heat transfer method

Oil-water two-phase flow at oilfield wellheads is a common occurrence in distribution. This paper proposes using a heat transfer method to accurately measure and monitor the total fluid volume at the wellhead. To achieve this, thermal sensors of types PT1000 and PT20, which are suitable for measuring oil-water mixed flow, are first designed. The feasibility and linearity of the sensors are simulated and calculated. Secondly, the heat transfer coefficient is computed using experimental methods and a functional relationship between the heat transfer coefficient and the flow rate is derived. Finally, the calculated results demonstrate the feasibility of using the heat transfer method to measure oil-water two-phase flow. If the water-liquid ratio (WLR) is known, the flow rate can be calculated through the functional relationship between the heat transfer coefficient and the flow rate. This method can improve the accuracy of estimating the flow rate.

Investigation of Cross‐Sectional Characteristics of Internal Meshing Screw Mixing Flow Field for Dough Paste

ABSTRACTThe internal meshing screw mixer, driven by extensional rheology, demonstrates excellent mixing efficiency for high‐viscosity materials while minimizing fiber damage. This study developed a computational model for the mixing process of high‐viscosity fluids based on the motion equations of the internal meshing screw. The model was validated through experiments involving the mixing of corn syrup, flour and water. The results reveal the flow field's cross‐sectional streamlines and confirm the presence of chaotic mixing states at the system interface through horseshoe mapping and the existence of hyperbolic points. By comparing the extensional and shear rates, as well as analyzing the distribution of mixing indices, this paper establishes that the primary mixing mechanism within the cross‐section is extensional force, highlighting the role of the internal meshing screw as a mixer dominated by extensional flow fields. We investigate the variations in fluid velocity, velocity uniformity index, extensional rate, shear rate, and mixing index over time under different conditions of eccentricity, rotor radius, and rotational speed. The findings indicate that while eccentricity has a limited impact on average velocity, it significantly enhances velocity disturbances and increases the ratio of extensional effects within the fluid domain. In contrast, rotor radius and speed lead to a linear increase in average velocity but have little effect on velocity disturbances and the extensional effects in the fluid domain. This study provides valuable insights into how various cross‐sectional parameters influence the flow field of the internal meshing screw mixing process, offering crucial support for its application in mixing high‐viscosity non‐Newtonian fluids within the food industry.

A Study of Mixed Non-Motorized Traffic Flow Characteristics and Capacity Based on Multi-Source Video Data.

Mixed non-motorized traffic is largely unaffected by motor vehicle congestion, offering high accessibility and convenience, and thus serving as a primary mode of "last-mile" transportation in urban areas. To advance stochastic capacity estimation methods and provide reliable assessments of non-motorized roadway capacity, this study proposes a stochastic capacity estimation model based on power spectral analysis. The model treats discrete traffic flow data as a time-series signal and employs a stochastic signal parameter model to fit stochastic traffic flow patterns. Initially, UAVs and video cameras are used to capture videos of mixed non-motorized traffic flow. The video data were processed with an image detection algorithm based on the YOLO convolutional neural network and a video tracking algorithm using the DeepSORT multi-target tracking model, extracting data on traffic flow, density, speed, and rider characteristics. Then, the autocorrelation and partial autocorrelation functions of the signal are employed to distinguish among four classical stochastic signal parameter models. The model parameters are optimized by minimizing the AIC information criterion to identify the model with optimal fit. The fitted parametric models are analyzed by transforming them from the time domain to the frequency domain, and the power spectrum estimation model is then calculated. The experimental results show that the stochastic capacity model yields a pure EV capacity of 2060-3297 bikes/(h·m) and a pure bicycle capacity of 1538-2460 bikes/(h·m). The density-flow model calculates a pure EV capacity of 2349-2897 bikes/(h·m) and a pure bicycle capacity of 1753-2173 bikes/(h·m). The minimal difference between these estimates validates the effectiveness of the proposed model. These findings hold practical significance in addressing urban road congestion.