Flow Generation Research Articles

Numerical simulation of supercritical flow in sudden contractions flumes

ABSTRACT In this research, the effect of sudden non-continuous contraction on the energy dissipation of supercritical flows was numerically investigated. This study focuses on energy dissipation in sudden contractions in supercritical flows. The numerical models were studied using FLOW-3D software and the random number generator (RNG) turbulence model. The laboratory tests were performed on sudden contractions of 10–15 cm and used shapes such as geometric trapezoidal and semicircular. Numerical simulations were carried out at a distance of 1.5 m from the supercritical flow generator gate, at a fixed opening of 2.6 cm, with the Froude number in the range of 2.5–7 and the relative contraction in the range of 8.9–9.73. This laboratory study found that as the Froude number of the upstream flow increases, the energy dissipation increases in the upstream (ΔE/E0) and downstream (ΔE/E1). For the 15 cm contraction, the results indicated that the energy loss compared with section A is 48.25% and compared with section B, it is 69.5% more than a free hydraulic jump in this channel. According to the conclusion, this value in trapezoidal constriction is 45.73 and 63.6% higher than in free hydraulic jump, respectively.

SC-AOF: A Sliding Camera and Asymmetric Optical-Flow-Based Blending Method for Image Stitching.

Parallax processing and structure preservation have long been important and challenging tasks in image stitching. In this paper, an image stitching method based on sliding camera to eliminate perspective deformation and asymmetric optical flow to solve parallax is proposed. By maintaining the viewpoint of two input images in the mosaic non-overlapping area and creating a virtual camera by interpolation in the overlapping area, the viewpoint is gradually transformed from one to another so as to complete the smooth transition of the two image viewpoints and reduce perspective deformation. Two coarsely aligned warped images are generated with the help of a global projection plane. After that, the optical flow propagation and gradient descent method are used to quickly calculate the bidirectional asymmetric optical flow between the two warped images, and the optical-flow-based method is used to further align the two warped images to reduce parallax. In the image blending, the softmax function and registration error are used to adjust the width of the blending area, further eliminating ghosting and reducing parallax. Finally, by comparing our method with APAP, AANAP, SPHP, SPW, TFT, and REW, it has been proven that our method can not only effectively solve perspective deformation, but also gives more natural transitions between images. At the same time, our method can robustly reduce local misalignment in various scenarios, with higher structural similarity index. A scoring method combining subjective and objective evaluations of perspective deformation, local alignment and runtime is defined and used to rate all methods, where our method ranks first.

Scalable concept drift adaptation for stream data mining

Stream data mining aims to handle the continuous and ongoing generation of data flows (e.g. weather, stock and traffic data), which often encounters concept drift as time progresses. Traditional offline algorithms struggle with learning from real-time data, making online algorithms more fitting for mining the stream data with dynamic concepts. Among families of the online learning algorithms, single pass stands out for its efficiency in processing one sample point at a time, and inspecting it only once at most. Currently, there exist online algorithms tailored for single pass over the stream data by converting the problems of classification into minimum enclosing ball. However, these methods mainly focus on expanding the ball to enclose the new data. An excessively large ball might overwrite data of the new concept, creating difficulty in triggering the model updating process. This paper proposes a new online single pass framework for stream data mining, namely Scalable Concept Drift Adaptation (SCDA), and presents three distinct online methods (SCDA-I, SCDA-II and SCDA-III) based on that framework. These methods dynamically adjust the ball by expanding or contracting when new sample points arrive, thereby effectively avoiding the issue of excessively large balls. To evaluate their performance, we conduct the experiments on 7 synthetic and 5 real-world benchmark datasets and compete with the state-of-the-arts. The experiments demonstrate the applicability and flexibility of the SCDA methods in stream data mining by comparing three aspects: predictive performance, memory usage and scalability of the ball. Among them, the SCDA-III method performs best in all these aspects.

One-step construction of light-responsive intelligent foam by the Hoffmeister effect and 2D black phosphorus: High stability and on-demand degradation

Stimulus-responsive liquid foams have gained much attention for use in various industrial applications. However, it remains challenging to construct such systems with integrated functionality of easy preparation, high stability, high foaming ability, and rapid on-demand degradation. Herein, by combining the Hofmeister effect and nanotechnology, a promising ultrastable and photoresponsive liquid foam was prepared that had a lifetime of several months and could be destroyed on demand in a few minutes. Specifically, the system was prepared by simply mixing a gelatine solution containing black phosphorus nanosheets (BPNs) and kosmotropic anions in the Hofmeister series with air in one step using only two syringes, and there were no chemical modifications or crosslinking agents required. The kosmotropic anions induced stronger hydrophobic interactions, bundling within molecular chains, and blockage of foam drainage channels, which significantly improved the foaming ability and the lifetime and mechanical properties of the foam. Moreover, rational structure design realized a promising on-demand degradation mechanism via a cascading “light trigger–heat generation–Marangoni flow generation” process occurring on the bubble surfaces. On this basis, the BPNs converted light into thermal energy, which induced Marangoni flow driven by surface tension gradients along the gas‒liquid interfaces, and the bubble film ruptured within seconds upon light illumination. The designed stimulus‒response systems combined stable, fast and repeatable processes without sacrificing the foaming abilities, thus providing a general way to control the stabilities of foams, bubbles and films.

Functional analysis of multi-scale fractures within a single fracture cluster in multi-horizontal wells

Defining the fracture function at each scale in the reservoir helps to analyze and optimize the thermal recovery properties of the reservoir. This study aims to reveal the functionalities of fractures at different scales by simulating one single fracture cluster coupled in multi-scale fractures. The geometric layout and parameter characteristics of the main fractures, branch fractures, and micro-fracture domain are investigated to speculate on their functions and influence on heat extraction performance. The results display that the main fractures and micro-fracture domain serve as the predominant channel for fluid flow. The branch fractures exert control over the flow transition from the main fractures to the micro-fracture domain, thereby influencing the generation of preferential flow. Micro-fracture domain is the primary way of fluid filtration loss. When the thickness of micro-fracture domain increased from 0 m to 20 m, the production flow rate increased from 2 kg/s to 4.2 kg/s, and the water loss ratio increased from 1 % to 4.9 %. However, expanding the micro-fracture domain can significantly enhance production flow rate and heat recovery rate at the expense of increased water loss ratio. Notably, preferential-flow-induced thermal breakthrough will not occur prematurely in this process. The permeability of branch fractures exerts the most substantial influence on the overall heat extraction, owing to its greatest impact on reservoir lifespan. These findings would provide valuable insights for optimizing fracturing morphology in multi-horizontal wells.

Entropy generation and heat transfer characteristics in MHD Casson fluid flow over a wedge with viscous dissipation and thermal radiation

AbstractThis investigation outlines the significance of MHD Falkner–Skan flow of non‐Newtonian fluid flow over a wedge. To study the non‐Newtonian flow, Casson fluid is taken. Additionally, this study explores heat and mass transport under the influence of viscous dissipation, Joule heating, and thermal radiation. This heat and mass transport investigation is carried out under the influence of thermal and concentration slip factors. Moreover, the entropy generation is also computed using the second law of thermodynamics. A set of nonlinear partial differential equations arises from the mathematical formulation of the problem. Similarity variables are then introduced to achieve a similarity solution. The leading differential equations are solved numerically using the Runge–Kutta‐4 method in conjunction with shooting techniques. Graphical representations are employed to demonstrate the physical significance of relevant parameters. The investigation presents and discusses the impact of various parameters on velocity, temperature, concentration and entropy profiles for three different positions of the wedge: stationary, forward‐moving, and backward‐moving. The main conclusions of the study are as follows: (1) Enhancing the magnetic parameter and wedge angle parameter leads to higher fluid velocity, (2) elevating both the Eckert and magnetic number results in a rapid escalation of fluid energy, (3) Skin friction coefficient increases gradually with an increase in the power law Falkner–Skan parameter.

Identification of the Storegga event offshore Shetland

The Shetland Islands (UK) are a seminal location for investigating palaeo-tsunami deposits. Onshore evidence suggests three tsunami have occurred during the Holocene: the Storegga tsunami ca. 8150 cal yr BP, the Garth tsunami ca. 5500 cal yr BP and the Dury Voe tsunami ca. 1500 cal yr BP. However, little research has been published on the impact of tsunami on the subtidal shelf where a large amount of North Sea hydrocarbon infrastructure is located. Here, we test the hypothesis that Holocene tsunami impacted shelf sediments, using radiocarbon dating and sedimentological characterization of cores recovered from the Fetlar Basin, offshore east Shetland. The cores contain distinct sand and shell lenses within a Holocene mud sequence, indicating a sudden change in hydrodynamic conditions. Radiocarbon dates bracketing the sand lenses overlap with the published dates for the Storegga event. Dates within the deposit are older (>9 cal. yr BP) which is consistent with reworking and redeposition of earlier sediments. Particle size analysis, ITRAX and MSCL data evidence increases in mean grain size, a reduction in sorting capacity, increased shell concentrations and peaks in associated elements (log(Ca/Fe), log(Ca/Ti) and Sr). These attributes indicate transport of allochthonous material from the inner shelf, and are typical of tsunami backwash-generated submarine debris flows. No evidence was found within the cores for any later Holocene tsunami, which may be due to either bioturbation, active currents, or lack of an initial deposit. The disturbance of sediments, and generation of a submarine debris flow within the Fetlar Basin by the Storegga event highlights the need to assess the potential impact of any future tsunami on planned and existing infrastructure at seabed. Erosion and deposition of allochthonous older marine sediment by the Storegga event also has consequence for interpretation of the coeval 8.2 ka cold event in marine sedimentary records in the tsunami affected region.

Solar PV and canal irrigation financing: Leveraging energy cash flow for sustainable agriculture

This research paper explores the innovative financing model for integrating Solar Photovoltaic (PV) systems with canal irrigation infrastructure. The focus is on utilizing energy cash flow generation to fund these sustainable projects. The study investigates the potential benefits, economic feasibility, and environmental impacts of this model, particularly in regions with extensive canal networks and high solar insolation. A specific case study of the Siret-Bărăgan irrigation canal in Romania, powered by floating photovoltaic systems, is analysed in detail. This study explores the feasibility and benefits of financing the Siret-Bărăgan irrigation canal in Romania through the integration of floating Photovoltaic (PV) systems. The project aims to address water scarcity, enhance agricultural productivity, and promote sustainable energy production. By leveraging green bond financing, the initiative proposes a financially viable and environmentally sustainable solution to Romania’s irrigation and energy challenges. The paper presents an in-depth analysis of the project’s technical, economic, and environmental aspects, underscoring its potential as a model for similar projects globally.

Aerodynamic analysis of vertical axis wind turbines at various turbulent levels: Insights from 3D LES simulations

This study provides novel insights into the aerodynamic performance of vertical axis wind turbines (VAWTs) in diverse turbulent environments using 3D large eddy simulations (LES). The research aims to understand how turbulence affects VAWT aerodynamics across different operational conditions, including varying wind speeds, tip speed ratios (TSRs), and turbulence intensities. Validation against wind tunnel test data from literature enhances the reliability of the findings. The study utilizes the consistent discrete random flow generation (CDRFG) technique to create homogeneous turbulence in the approaching flow. Through a detailed examination of the rotor aerodynamics and flow fields, critical insights are gained into the impact of turbulence on VAWT performance. The results highlight that local wind speed fluctuations influence the onset of dynamic stall, with turbulence significantly affecting lift forces, while having negligible effects on drag. Notably, fluctuations in the one-cycle power coefficient CP,sgl are primarily attributed to variations in lift. Furthermore, under turbulent conditions, substantial improvements in power performance are observed as wind speed increases from 5 m/s to 10 m/s, with minimal further enhancements at higher wind speeds. These findings contribute valuable insights for optimizing turbine design and operation, particularly in regions characterized by varying wind speeds and turbulence.

A critical transition of two-dimensional flow in toroidal geometry

We investigate two-dimensional (2-D) axisymmetric flow in toroidal geometry, with a focus on a transition between 2-D three-component flow and 2-D two-component flow. This latter flow state allows a self-organization of the system to a quiescent dynamics, characterized by long-living coherent structures. When these large-scale structures orient in the azimuthal direction, the radial transport is reduced. Such a transition, if it can be triggered in toroidally confined fusion plasmas, is beneficial for the generation of zonal flows and should consequently result in a flow field beneficial for confinement.

Dynamic response of a wind turbine wake subjected to surge and heave step motions under different inflow conditions

The development of floating offshore wind turbines poses new challenges since the floating platform introduces complex dynamics in the wind turbine wake. These wake dynamics are intricately tied to the advection velocity, referring to the velocity of the downstream propagation of the air flow, and used in the context of wind farm modelling. The present article investigates the far-wake dynamic response of a wind turbine model subjected to heave (up-down translation) and surge (fore-aft translation) step motions under two distinct inflow conditions. Wind tunnel experiments were conducted with hot-wires in a realistic turbulent inflow and a low shear and no ground effect inflow, achieved by varying the hub height of the wind turbine model in the atmospheric boundary layer developed in the test section. The results show that the dynamic response of the wake under the low shear and no ground effect inflow conditions aligns with a second-order system with the presence of undershoots and overshoots. In contrast, under realistic conditions, it appears like a first-order system with undershoots and overshoots less evident in most cases. Despite these variations the determined advection velocity remains roughly the same and consistent with the literature for both heave and surge step motions, regardless of the inflow conditions.

The evolution of cardiac function in patients with non-Hodgkin’s lymphoma under chemotherapy

In clinical practice, the treatment of non-Hodgkin’s lymphoma (NHL) often involves the combination of several chemotherapy agents, radiotherapy and immunotherapy. While these multimodal approaches improve the efficacy of pathology-specific treatment, they also increase the risk of cardiovascular complications, the most common of which is ventricular dysfunction induced by anti-tumor therapy. Aim of the study: Evaluation of the impact of anti-tumor treatment of NHL on the trajectory of left and right ventricular echocardiographic function. Materials and methods: 127 randomly selected patients from the hematology departments of the PSMI Institute of Oncology were included in the study. Patients were investigated during 3 visits by comprehensive echocardiography, the first visit was up to the onset of anti-tumoral treatment, the 2nd visit was 1 month after initiation and the 3rd visit at 6 months after the debut of chemotherapy. Results: During the anti-tumor treatment, a statistically significant decrease in left ventricular systolic indicators was attested by following parameters: left ventricular ejection fraction (LV EF), mean left ventricular S’, the ratio between the maximum velocity of the E wave and the flow propagation velocity (E/Vp), with an ANOVA p-value <0.001. Regarding the right ventricular systolic function, the indices reflected by TAPSE and S’ right ventricular free wall were reduced statistically significantly also (p ANOVA <0.001). The given analysis confirmed the impairment of ventricular relaxation throughout the treatment, the increase in left ventricular filling pressures, the ratio E/A and E/e’ showed a statisticallysignificant increase, parameters such as the deceleration time of the E wave, the relaxation isovolumetric time, the ratio e’/a’ did not register a statistically significant dynamic (p ANOVA = 0,897; 0,705 and 0,145 respectively). 6 months after the start of treatment, cardiac dysfunction associated with cancer therapy (CTRCD) was found in 18 patients (14,2%), 8 (6,3%) presented a moderate asymptomatic form, 7 (5,7%) had a mild asymptomatic form and 3 (2,4%) a symptomatic one.Conclusion: The left ventricular systolic function was statistically significantly reduced under the impact of the applied treatment, which was confirmed by the LV EF, the mean S’ value at the LV and the E/Vp ratio, the diastolic function having an impact through the E/A and E/e’ ratio. Regarding the function of the right ventricle, we attested statistically significant changes only in the longitudinal contraction parameters. CTRCD was confirmed in 18 patients.

Hydrodynamics of Meander Chute Cutoffs in Microtidal Mudflats

AbstractRiver cutoffs and oxbow lakes represent ubiquitous features in alluvial plains, shaped by unidirectional meandering flow. Extensive studies have been conducted on these features as their presence immediately decreases meander sinuosity and plays a significant role in the long‐term eco‐morphodynamic and sedimentary evolution of landscapes they carved in. In contrast, limited attention has been given to meander cutoffs formed in tidal environments by bidirectional currents, and the corresponding hydrodynamical processes within these features are poorly understood. Here, we present new, first‐handed hydroacoustic data collected through a series of fixed‐point and cross‐sectional flow measurements along a chute cutoff located in the microtidal Diaokou Mudflat, the Yellow River Delta, China. The investigated cutoff bend displays higher hydrologically active than the newly‐formed chute channel at low tide, whereas the chute channel gradually become the main conduit for tidal flow propagation with water stage increasing. Specifically, poorly‐developed flow separation zones are compensated by widespread secondary circulation cells that are more pronounced under the influence of turbulences and complex bedforms rather than channel curvatures. Unlike fluvial cutoffs, which tend to be hydrologically disconnected to parent channels by coarse‐grained bed sediment plugging near the entrances, our study case is characterized by the absence of plug bars and widespread bank slumps instead. Consequently, our results support earlier suggestions that tidal cutoffs seldom disconnect from parent channels due to frequent overbank events and flow confluences, which can keep cutoffs active by flushing away fine‐grained, cohesive sediments, especially in mudflat systems.

Performance and Navigation Behavior of using Teleportation in VR First-Person Shooter Games

Teleportation has been adopted as the preferred mode of navigation in many virtual reality (VR) experiences due to its ability to allow users to easily move beyond the limitations of the tracking space while minimizing the risk of inducing VR sickness. Teleportation instantly translates the user’s viewpoint to a user-selected destination and therefore eliminates any optical flow generation that could cause visual-vestibular conflict. Though teleportation is a discrete navigation method unique to the domain of VR, most VR experiences are modeled after 3D experiences found on desktop/console platforms that use continuous locomotion. How the use of teleportation affects the performance and navigation behavior of its users, especially in competitive first-person shooter environments is unknown, yet it could have a significant effect on gameplay design. We conducted a user study (n=21) that compares teleportation versus continuous locomotion using a VR first-person shooter game with other players being simulated using AI agents. We found significant differences in performance, navigation behavior, and how both locomotion methods are perceived by its users. Specifically, using teleportation, players traveled farther, but during combat were found to be more stationary and as a result got hit more frequently. These differences were profound and carry the potential to impact multiplayer games. We discuss possible strategies to balance gameplay.

A simple active fluid model unites cytokinesis, cell crawling, and axonal outgrowth.

Axonal outgrowth, cell crawling, and cytokinesis utilize actomyosin, microtubule-based motors, cytoskeletal dynamics, and substrate adhesions to produce traction forces and bulk cellular motion. While it has long been appreciated that growth cones resemble crawling cells and that the mechanisms that drive cytokinesis help power cell crawling, they are typically viewed as unique processes. To better understand the relationship between these modes of motility, here, we developed a unified active fluid model of cytokinesis, amoeboid migration, mesenchymal migration, neuronal migration, and axonal outgrowth in terms of cytoskeletal flow, adhesions, viscosity, and force generation. Using numerical modeling, we fit subcellular velocity profiles of the motions of cytoskeletal structures and docked organelles from previously published studies to infer underlying patterns of force generation and adhesion. Our results indicate that, during cytokinesis, there is a primary converge zone at the cleavage furrow that drives flow towards it; adhesions are symmetric across the cell, and as a result, cells are stationary. In mesenchymal, amoeboid, and neuronal migration, the site of the converge zone shifts, and differences in adhesion between the front and back of the cell drive crawling. During neuronal migration and axonal outgrowth, the primary convergence zone lies within the growth cone, which drives actin retrograde flow in the P-domain and bulk anterograde flow of the axonal shaft. They differ in that during neuronal migration, the cell body is weakly attached to the substrate and thus moves forward at the same velocity as the axon. In contrast, during axonal outgrowth, the cell body strongly adheres to the substrate and remains stationary, resulting in a decrease in flow velocity away from the growth cone. The simplicity with which cytokinesis, cell crawling, and axonal outgrowth can be modeled by varying coefficients in a simple model suggests a deep connection between them.

Lie group analysis and SQLM of entropy generation of MHD nonlinear radiative micropolar nanofluid flow with thermophoresis and Brownian motion

This study investigates the entropy generation in hydromagnetic mixed convection of a micropolar fluid flowing over a stretchable sheet, taking into account various influential factors such as nonlinear thermal radiation, Ohmic dissipation, uniform heat source/sink effects, chemical reaction, thermophoresis, and Brownian motion. The Spectral Quasilinearization Method (SQLM) is employed, which transforms nonlinear equations into a series of linearized ones, streamlining the solving process. Additionally, Lie group analysis is utilized to identify symmetries and derive similarity transformations crucial for converting partial differential equations into coupled ordinary differential equations, which are then solved numerically. A comprehensive sensitivity analysis is conducted on critical parameters, including the Darcy parameter, Biot number, Brinkman number, nonlinear convection parameter, and chemical reaction parameter. This analysis explores the impacts of these parameters on various flow profiles, such as velocity, temperature, microrotation, concentration, and entropy generation, enriching the depth and practical relevance of the findings. The results reveal that increasing the Brinkman and Reynolds numbers enhances entropy generation profiles while increasing the coupling parameter reduces them. The focus on entropy generation analysis provides valuable insights into energy utilization and system efficiency, particularly in micropolar fluid dynamics. Furthermore, the study underscores the practical implications of its findings by highlighting their relevance in evaluating the effectiveness of industrial processes, especially those related to energy conversion and heat transfer phenomena.

Effect of pressure pores size on hydrodynamic and hydroacoustic marine propeller performances under cavitating case

The numerical work presented in the paper investigates the effect of pressure pores on hydrodynamic and hydroacoustic performances. This research aims to reduce cavitation area and underwater noise by mitigating the tip vortex cavitation. Compared to the few studies devoted to the pressure pores technique, several configurations based on the E779A marine propeller have been tested by considering different azimuthal and radial step values, a wider pore region concentrated at the top of the blade, and several pore diameter values. In addition, a numerical simulation was started to verify the effectiveness of the theoretical models in detecting the effect of pressure pores on the acoustic propagation generated by the propellers tested. The numerical approaches combining cavitating flow and noise propagation are performed using a hybrid method, which solves the Ffowcs Williams-Hawkings (FW–H) equation. A validation of the numerical simulation is carried out for cavitating and non-cavitating cases. Open water performances, cavitation area, sound pressure levels, and thrust distributions are analysed for two cavitation numbers. σ= 1,763 and σ= 1,029. The obtained results reveal that the cavitation area decreases as the pressure pore radius increases, but a slight reduction in propulsive efficiency accompanies this. Particularly for the pores radius of 0,00264D, propeller efficiency loss doesn't exceed 2,6 % and 4,05 % for the two cavitation numbers investigated. Nevertheless, this configuration showed better acoustic performances with a diminution of 10 dB in overall sound pressure level compared to the propeller without pressure pores.

Strategies for multi-case physics-informed neural networks for tube flows: a study using 2D flow scenarios

Fluid dynamics computations for tube-like geometries are crucial in biomedical evaluations of vascular and airways fluid dynamics. Physics-Informed Neural Networks (PINNs) have emerged as a promising alternative to traditional computational fluid dynamics (CFD) methods. However, vanilla PINNs often demand longer training times than conventional CFD methods for each specific flow scenario, limiting their widespread use. To address this, multi-case PINN approach has been proposed, where varied geometry cases are parameterized and pre-trained on the PINN. This allows for quick generation of flow results in unseen geometries. In this study, we compare three network architectures to optimize the multi-case PINN through experiments on a series of idealized 2D stenotic tube flows. The evaluated architectures include the ‘Mixed Network’, treating case parameters as additional dimensions in the vanilla PINN architecture; the “Hypernetwork”, incorporating case parameters into a side network that computes weights in the main PINN network; and the “Modes” network, where case parameters input into a side network contribute to the final output via an inner product, similar to DeepONet. Results confirm the viability of the multi-case parametric PINN approach, with the Modes network exhibiting superior performance in terms of accuracy, convergence efficiency, and computational speed. To further enhance the multi-case PINN, we explored two strategies. First, incorporating coordinate parameters relevant to tube geometry, such as distance to wall and centerline distance, as inputs to PINN, significantly enhanced accuracy and reduced computational burden. Second, the addition of extra loss terms, enforcing zero derivatives of existing physics constraints in the PINN (similar to gPINN), improved the performance of the Mixed Network and Hypernetwork, but not that of the Modes network. In conclusion, our work identified strategies crucial for future scaling up to 3D, wider geometry ranges, and additional flow conditions, ultimately aiming towards clinical utility.

Thermo-hydraulic Investigation of a Heat Exchanger Tube Equipped with 3D-Printed Swirl Flow Generators

AbstractHeat transfer capabilities of the heat exchangers require enhancements to save energy and decrease their size. For this purpose, the swirl generators have been widely preferred. However, the swirler inserts have not reached their optimum shape. Thus, this study experimentally and numerically investigates the impact of novel 3D-printed swirler inserts with varying twist angles in the range of 0°–450° on the thermo-hydraulic performance of solar absorber tube heat exchangers under laminar flow (Re = 513–2054) condition. Friction factor, Nusselt number, and performance evaluation criterion (PEC) were used to assess heat exchanger performance, and related correlations are provided. Tangential velocity components were also used to explore fluid flow characteristics in local analysis. Numerical investigation was done by using computational fluid dynamics adopting Finite Volume Method in ANSYS Fluent. Results show that 3D-printed swirlers considerably increase heat transfer compared to plain tube. The swirler with a twist angle of 450° led to the maximum enhancements of nearly 217% in average Nusselt number and around 1630% in friction factor at Reynolds number of 2054. Overall, increasing Reynolds number enhanced Nusselt number. The highest PEC of 1.15 was observed at a Reynolds number of 1031 using the swirler with 150° twist angle. Flow near the swirler has higher tangential velocities, hence contributing to local Nusselt number enhancement up to 453.8% compared to plain tube when swirler with twist angle of 450° utilized. It is anticipated that findings of this study can guide further related research and increase the usage of swirlers in heat exchangers.

Computational framework for thermal transportation in radiative bio-convective micropolar nanomaterial flow over stretched sheet with entropy optimization

Entropy generation (EG) in bioconvective nanofluid flows is a phenomenon that occurs due to the presence of nanoparticles and microorganisms within fluid flows. EG leads to an increase in thermodynamic irreversibility within the system. Understanding and quantifying EG in nanofluid flows is essential to optimize heat transfer processes and design efficient systems. Current investigation aims to analyze the irreversibility of the magnetized bioconvective flow of non-Newtonian micropolar type nanofluid. Flow features are modeled considering flow by a Darcy Forchheimer permeable surface of a stretched sheet. Phenomenon of bioconvection in a micropolar fluid is considered to regulate the solid tiny particles. Magnetic field and permeability effects are accounted in momentum relation. Energy relation is constructed in the presence of Joule heating, internal fluid friction, and thermal radiation. Mass concentration equation is formulated by accounting Arrhenius kinetics and binary chemical reaction. Furthermore, the buoyancy effects of solid tiny particles are considered in thermal and concentration relations. Total entropy of the considered flow is modeled using the second thermodynamics law. System of dimensional equations representing the flow is obtained with the implementation of boundary layer approximations. The acquired system is altered into an ordinary one through transformations and then tackled by numerical scheme Runge-Kutta-Fehlberg method (RKF-45) in the Mathematica package. Behavior of velocity, thermal field, entropy production, mass concentration, motile density, and Bejan number versus sundry variables is investigated through plots. Skin friction, local heat, mass, and density rates are numerically examined. Thermal field upsurges and velocity field decays versus higher Hartmann number. Entropy generation improved versus higher Brinkman number, microorganisms diffusion variable, and temperature difference ratio variable.