Mixed Flow Research Articles

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.

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.

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).

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

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

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

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

Исследование характеристик комбинированных устройств глубокого охлаждения дымовых газов на водогрейных котлах системы ЖКХ

One of the ways to increase the efficiency of hot water boilers of the housing and communal services system is the deep cooling of combustion products to temperatures below the dew point temperature. Currently, there are a number of studies on the use of condensation economizers and air heaters of various types to solve this problem. The use of such devices makes it possible to reduce the temperature of combustion products and, thus, increase the heat utilization coefficient, reduce fuel consumption. The use of combined flue gas cooling devices seems particularly promising, but the parameters of their operation have not yet been studied. In this regard, the development and study of the parameters of such devices are relevant. Using the techniques to design heat exchangers, a set of thermal calculations has been performed to study the characteristics of a combined deep cooling system for combustion products after a hot water boiler of the housing and communal services system, represented by an air heater and a condensation economizer. It is considered that one part of the flue gases after the air heater is sent to the economizer, and the other part goes through the bypass, bypassing the economizer, and then meets the combustion products coming out of it. The distribution of the combustion product flow before the economizer is based on the need to ensure the temperature of the mixed flow after the economizer at 70 °C. For the most common hot water boiler in the housing and communal services system of the TVG-8M type, the authors have been established the dependence of the heat transfer coefficients, the surface area of the heat exchangers and other parameters of the deep cooling system of the exhaust gases on the set value of the temperature of the combustion products after the air heater. It has been established that the proposed scheme of a combined deep cooling system for combustion products makes it possible to improve the technical and economic performance of the boiler by reducing fuel consumption. It is proved that the smoke temperature after the air heater for this type of the boiler should not be very low (not lower than 115–130 °C), since it dramatically increases the heat flow with a decrease in the average logarithmic temperature difference and leads to an increase not only in the temperature of the heated air, but also in the surface area of the air heater.

Novel Fluidic Oscillator Evaluation Considering Dimensional Modifications

Although flow mixing and cooling can be greatly enhanced when considering the use of fluidic oscillators (FOs), they are more commonly employed in active flow control (AFC) applications where the injected pulsating flow interacts with the boundary layer, usually in order to delay its separation. In fact, prior to any FO implementation in a given application, it is essential to study the range of frequencies and amplitudes it can generate as a function of the incoming mass flow and its dimensions. This is what is being performed in the present manuscript for a rather novel FO configuration. A numerical study of a standard three-dimensional (3D) FO configuration, and also using a two-dimensional (2D) approach, is initially presented. After comparing the 3D and the 2D results and analyzing the main differences, we modified some of the internal dimensions of the FO in order to evaluate the variation in its dynamic performance. The present results clarify which internal dimensional modifications are more effective in generating larger output frequencies and velocity field variations. Care is taken to analyze the origin of self-sustained oscillations. This paper links, for the first time, the origin of the pressure force oscillations at the feedback channel’s outlet, with the interaction of the mixing chamber central jet and the reverse feedback channel flow at the mixing chamber’s converging walls. A novel equation relating the FO outlet mass flow frequency with the time-averaged FC reverse flow is presented and discussed. In fact, the present study needs to be seen as the continuation of a former one, recently published by authors, where the effects of several Reynolds numbers as well as some different internal dimensions were considered.

A DATA DRIVEN METHOD FOR THE DERIVATION OF EXPLICIT ALGEBRAIC REYNOLDS STRESS MODELS APPLIED TO THE WAKE LOSSES OF LOW-PRESSURE TURBINE CASCADES

Abstract This paper introduces and validates a data-driven approach to improve the prediction of linear eddy viscosity models (LEVMs). The general approach is adopted in order to improve the wake mixing of low-pressure turbine (LPT) cascades. The approach follows the rationale applied in the derivation of explicit algebraic Reynolds stress models (EARSMs) by including additional second-order tensors in the Boussinesq assumption. The unknown scalar functions that determine the contributions of each second-order tensor to the Reynolds stresses are approximated as polynomials. A metamodel-assisted multi-objective optimization determines the value of each of the polynomial coefficients by minimizing the difference between the result of the EARSM simulation and reference data provided by a high fidelity large eddy simulation (LES). In this study, tailor made EARSMs are calibrated to improve the prediction of the kinetic energy loss distribution in the wake of the T106C LPT cascade. We investigated the influence of each polynomial coefficient of the EARSM on the results. The models generated by the approach reduced the deviations in total kinetic energy loss between the LES reference solution and the baseline model by approximately 70%. The turbulent quantities are analyzed to identify the physical correlations between the model inputs and the improvement. The transferability of the models to unseen test cases was assessed using the MTU-T161 LPT cascade. In summary, the suggested approach was able to generate tailor made EARSM models that reduce the deviations between RANS and LES for the mixing of turbulent wake flows.

Numerical computations of MHD mixed convection flow of Bingham fluid in a porous square chamber with a wavy cylinder

This work examines the behavior of Bingham fluids in porous media under magnetohydrodynamic (MHD) conditions, addressing a significant issue in fluid dynamics and heat transport. The authors study mixed convection in a porous square chamber with twisted cylinders using COMSOL Multiphysics and finite element techniques. Compared to other research, this one offers a more complicated and realistic model since it integrates Bingham fluid flow and MHD effects in a porous chamber with wavy cylinders. Plotting of streamlines, isotherms, and Nusselt numbers is done for several parameters: Numbers Reynolds (1, 5, 10, 50), Hartmann (0, 25, 50, 100), Bingham (0, 1, 5, 10), Darcy (10−4, 10−3, 10−2, 10−1), and Grashof (102,103,104,105) are among those assigned numbers. According to findings, larger Bn values promote thermal stratification and decrease flow mobility, which results in dominating conductive heat transmission. The nusselt number falls with Ha and Bn but rises with Re, Da, and Gr. The study aims to provide useful insights into several industrial disciplines, such as nuclear power plant architecture and petroleum engineering, by enhancing heat transfer in non-Newtonian fluids under magnetic fields. It also boosts the efficiency of chemical reactors and filters. Based on our findings, for lower Re = 1, the lowest value of Numean is 2.602, while at Re = 50, its values rise to 6.425.

Phase transition in heterogeneous macro continuum model integrating the jerk effect with the mixed traffic flow involving human driving and ADAS vehicles

Vehicles equipped with advanced driving assistance systems (ADAS) can acquire information about preceding and following vehicles, which will have an undeniable impact on the phase transition of traffic flow. Therefore, we establish a new heterogeneous continuum model of traffic flow considering the jerk effect mixed with human driving (HD) and ADAS vehicles. The neutral stability condition associated with the permeability of ADAS vehicle is inferred via stability analysis. According to simulation, shock wave occurs, implying that our model can emerge correct wave propagation trend. Moreover, the simulation of density evolution and flow changes also suggests that an increase in ADAS vehicle penetration and jerk effect can enhance traffic system stability and reduce energy consumption.

Exploring nanoparticle dynamics in binary chemical reactions within magnetized porous media: a computational analysis

Artificial Neural Networks are incredibly efficient at handling complicated and nonlinear mathematical problems, making them very useful for tackling these challenges. Artificial neural networks offer a special computational architecture that is extremely valuable in disciplines like biotechnology, biological computing, and computational fluid dynamics. The present work investigates the applicability of back-propagation artificial neural networks in conjunction with the Levenberg-Marquardt algorithm for evaluating heat transmission in hybrid nanofluids. This work focuses on the computational analysis of a MgO + GO/EG hybrid nanofluid’s steady mixed convection flow over an exponentially stretched sheet, considering multiple slip boundary conditions, thermal conductivity, heat generation, and thermal radiation. A nonlinear system of ordinary differential equations is produced from the basic associated partial differential system by performing the proper exponential similarities modifications. For generating benchmark datasets, the resulting ordinary differential equations are processed employing the bvp4c method. Considering benchmark datasets set aside for training (70%), testing (15%), and validation (15%), the Levenberg-Marquardt algorithm, which employs back-propagation in artificial neural networks, is implemented. The accuracy of the suggested strategy for handling nonlinear problems is verified utilizing mean squared error, error histograms, and regression analysis, which are all used to evaluate the methodology. Outstanding agreement is seen when ANN outputs are compared to numerical results. The flow properties, including temperature, velocity, and concentration profiles, are shown graphically and numerically. For practical purposes, it is therefore essential to analyze the flow and heat transfer in hybrid nanofluids over exponentially extending and shrinking surfaces under mixed convection and heat source scenarios. Hybrid nanofluid problems have a wide range of practical and industrial applications, such as medication delivery, manufacturing, microelectronics, nuclear plant cooling, and marine engineering.

Mixed Convection Flow of a Viscous Dissipative and Heat Generating/Absorbing Fluid Through a Slit Microchannel

This paper is aimed at investigating the consequences of viscous dissipation and super-hydrophobicity on a magnetized mixed convection flow of an electrically conducting fluid across an up facing microchannel influenced by a transverse magnetic field. The plates were alternatively heated and incorporated with heat source/sink effect. The modeled governing equations have been obtained using a semi-analytical (regular perturbation) method. Various line graphs have been plotted to demonstrate the behavior of key parameter dictating the flow. It was found out that the thermal gradient and fluid velocity are significantly enhanced for mounting values of mixed convection Gre, Brickman number Br, Darcy porous number K and heat source S parameters in the superhydrophobic microchannel for constant pressure gradient Г. On the other hand, the velocity deteriorates for increasing levels of magnetic field M and heat sink S factors. Further, the comparison of this present analysis with previously published literature for limiting cases when Г=S=0 and Gre=1 showcased an excellent concurrence, thereby confirming the accuracy and validity of this present investigation. The findings from this research will find relevance in engineering, technological and industrial processes such as for solar collectors, nuclear reactors cooled during emergency shutdown, nuclear power plants, gas turbines and the various propulsion devices for aircraft, missiles, satellites and space vehicles.

Enhancement of carbon nanotubes/kerosene nanofluids on mixed convective heat transfer in rectangular enclosures

With the objective of understanding how the mixed convective and the geometrical parameters together influence the nanofluid behavior (enhancement or deterioration) and finding the best configuration of the moving walls for engineering purposes, this paper investigates the single lid-driven mixed convective flow of carbon nanotubes/kerosene nanofluids confined in vertical and horizontal cavities with non-uniform boundary conditions applied to the vertical walls. The findings of this paper can provide crucial conclusions into the behavior and optimization of nanofluids in mixed convective flows in enclosed systems for engineering applications. The system of the governing equations is tackled by a validated in-house code, where we compared the code accuracy with previous experimental and numerical works. The governing parameters are -50 ≤ Pe ≤ 50, 0.5 ≤ A ≤ 4, and 0 ≤ φ ≤ 3%. The effective nanofluid properties are calculated using special experimental models. The outcomes revealed that the carbon nanotube effect on heat transfer depends on the aspect ratio. The greater the aspect ratio, the more pronounced the negative impact of the nanotube concentration where Nusselt number is reduced by 4.49% and 16.17% for φ = 0.01 and 0.03, respectively, in the case of Pe = 0 and A = 4. The Peclet number also has a significant impact on the heat transfer, especially for higher aspect ratios, and diminishes the critical aspect ratio where the nanofluid's behavior changes. An augmentation in the aspect ratio and Peclet number brings about an augmentation in the Nusselt number. Additionally, the Peclet number can reverse the conjugated effect of carbon nanotube volume fraction and aspect ratio on nanofluid enhancement. When Pe = 50 in C1, heat transfer rate is 1.75% and 1.11% enhanced for φ = 0.01 and 0.03, respectively, and A = 4. Moving horizontal walls exhibits higher heat transfer enhancement compared to vertical ones.

Safety evaluation for mixed traffic flow of CAVs with different automation and connection levels

With the development of connected communication and automated driving technologies, connected automated vehicles (CAVs) are expected to gradually replace human-driven vehicles (HDVs), owing to their significant safety advantages. However, widespread adoption of CAVs will still require a considerable amount of time due to constraints such as technological development, legal regulations, and social acceptance. During the transitional period of CAVs’ proliferation, road traffic will comprise vehicles with different levels of connection and automation. These vehicles will differ in technology regarding communication, perception, decision-making, and other aspects, potentially posing severe challenges to mixed traffic flow safety. To address this issue, this paper proposes a mixed traffic flow model from both automation and connection perspectives to consider time delay and communication degradation. Four safety evaluation metrics are employed, and three-speed scenarios are set to investigate the influence of connection levels, automation levels, and their combined effects on mixed traffic flow safety. The result shows that (1) low automation enhances traffic safety in a non-connected environment, whereas medium and high automation decreases traffic safety. Conversely, in a connected environment, the role of automation levels exhibits the opposite pattern. (2) non-connected vehicles enhance traffic safety in a low-automated environment, while connected vehicles diminish it. However, connection level effects are reversed in medium and highly automated environments. (3) In connected and automated environments, traffic safety is increased by non-connected and low-automated vehicles, connected and medium automated vehicles, and connected and highly automated vehicles. However, other vehicle configurations decrease traffic safety. (4) Across various scenarios, the integration of connection and high automation proves beneficial for reducing traffic collision risks and improving traffic safety. In summary, this study provides theoretical support for managing and controlling mixed traffic flow with different automation and connection levels in the future.

Hall effect on mixed convection MHD flow of nanofluid with clean, copper and Ag water through a vertical rotating channel

AbstractThis article aims to investigate the hall current consequences on the transfer of clean water containing silver in addition to copper nanoparticles suspended nanofluids through vertical rotating channel. Boussinesq approximation is taken into consideration. Exact analytical solutions of governing equations subject to physical boundary conditions are obtained using the techniques of non‐dimensionalization. The impacts of Grashof number, radiation parameter, Prandlt number, frequency parameter, magnetic parameter, Hall parameter, parameter of rotation and its effects on primary as well as secondary velocity and temperature profiles are presented graphically. We analyze the Hall effects and mixed convection in magnetohydrodynamic (MHD) flow of nanofluids through a vertical rotating channel, based on extensive research and applications. An analytical approach is used to derive the exact solution to this problem. A comparative study for silver and copper nanoparticles is made. A tabular solution for impacts of said parameters on convection rate and skin friction coefficient is also presented. This study is applicable for geophysical dynamics and engineering applications.

A Lane Change Model Considering the Stability of Cooperative Adaptive Cruise Control Platoon Fleet

In this article, lane change models for mixed traffic flow under cooperative adaptive cruise control (CACC) platoon formation are established. The analysis begins by examining the impact of lane changes on traffic flow stability. The influences of various factors such as lane change locations, timing, and the current traffic state on stability are discussed. In this analysis, it is assumed that the lane change location and the entry position in the adjacent lane have already been selected, without considering the specific intention behind the lane change. The speeds of the involved vehicles are adjusted based on an existing lane change model, and various conditions are analyzed for traffic flow disturbances, including duration, shock amplitude, and driving delays. Numerical calculations are provided to illustrate these effects. Additionally, traffic flow stability is factored into the lane change decision-making process. By incorporating disturbances to the fleet into the lane change income model, both a lane change intention model and a lane change execution model are constructed. These models are then compared with a model that does not account for stability, leading to the corresponding conclusions.