Flow State Research Articles

Acceleration of the complex reacting flow simulation with a generalizable neural network based on meta-learning

A chemical decoupled method is proposed in this paper. To accelerate the complex reacting flow simulation, the chemistry and flow computation is decoupled by a Neural Network (NN). A chemical kinetics database including 2,106,496 flow states and corresponding reacting source terms has been generated. Nevertheless, the data presents imbalance and spans a wide range of magnitudes, which challenges the NN training. The normalization method, NN’s construction, and performance evaluation indicators are optimized to address this challenge. Another problem is that different processes, such as transport or reaction, dominate different flow regions. This phenomenon requires the NN sufficient generalization to accurately map the complex reactions and flow states, even when the dominant process is different. The generalization of the NN is improved through the meta-learning strategy, the residual connection, and the inter-layer sine normalization. The effect of these enhancements is tested by noisy data and simulations with different turbulence model and boundary conditions. The method has been demonstrated in a supersonic combustion simulation with 16 species and 137 reactions. The maximum mean square relative error between the simulation with NN and the traditional simulation is 13.59 %. The calculation time is reduced from 6415.989 min (about 4.456 days) of the traditional simulation to 1983.576 min (about 1.377 days) of the simulation with NN. This method has application potential in accelerating the complex reacting flow simulation.

Study on tensile properties of copper/graphene/2D-SiC composite materials: A molecular dynamics simulation

Van der Waals heterostructures composed of graphene and 2D-SiC generally exhibit outstanding electrical and mechanical properties. However, these structures are prone to brittle failure during damage, which greatly limits their application in practical engineering. Conversely, copper-based composite materials have been discovered to significantly enhance material toughness. Therefore, a novel copper/graphene/2D-SiC composite material is designed and molecular dynamics simulation is performed to investigate its mechanical properties under uniaxial tension. The results show that these composite materials possess the advantages of both high strength and toughness due to the heterostructure layer and the copper layer. Further analysis of the deformation mechanism of the copper layer indicates that it is mainly attributed to short-range atomic slip and the generation of Shockley partial dislocations. The heterostructure layer can partially impede the propagation of dislocations, enhancing the overall tensile strength of the composite materials. After the copper layer enters the plastic flow state, the variation of bond lengths and bond angles suggests that the heterostructure layer bears the tensile load, and the 2D-SiC layer is more prone to fracture due to higher stiffness compared to the graphene layer. Additionally, the influence of temperature and strain rate on the tensile properties is investigated. It is observed that increasing temperature could gradually reduce the tensile strength of the composite materials while the strain rate, within a certain range, has little effect.

Flow Training Program: Mindfulness, Decision Making, and Mental Well-Being of Young and Adult Elite Handball Athletes.

This study aimed to analyze the effect of a flow training program based on mindfulness applied to young and adult elite handball athletes. A quantitative, quasi-experimental, descriptive data analysis approach was carried out. The sample included 105 athletes (51 female and 54 male). The athletes were divided into two groups: (i) experimental (n = 53) and (ii) control (n = 52). The results of the repeated ANOVA indicated that the experimental group achieved significant improvements compared to the control group in decision making (n2p = 0.086), mental well-being (n2p = 0.045), dispositional flow state (n2p = 0.103), non-judgment (n2p = 0.040), refocusing (n2p = 0.052), and mindful traits in daily life (n2p = 0.058). A Pearson analysis demonstrated a positive correlation between dispositional flow state and mindfulness in sport and mental well-being. The correlation analysis also showed an inverse correlation between decision making and sense of control and mindful traits in daily life. The findings revealed that the program can be effective in decision making, mental well-being, dispositional flow state, mindfulness in sport, and mindful traits in daily lives of athletes.

Nature relatedness, flow experience, and environmental behaviors in nature-based leisure activities.

Through nature-based leisure activities, spending time in nature offers opportunities to reduce stress, relax the mind, and enhance feelings of well-being. Being aware of the benefits provided by these activities increases the nature relatedness, and during the time spent in nature, it enables experiencing positive and satisfying moments by entering into a state of flow. The concepts of nature-relatedness and flow experience represent psychological experiences and characteristics that play an important role in enhancing psychological well-being and life quality. Based on structural equation models, the relationships among nature-relatedness, flow experience, and environmental behaviors were investigated. Data were collected from 379 individuals (212 male, 167 female) who regularly engage in nature-based leisure activities such as cycling, hiking, and fishing. The participants were predominantly male (55.9%) and aged 45 years and over (53.3%). The nature-relatedness significantly influences flow experience (R 2 = 0.505, p < 0.01), environmental behavior (R 2 = 0.108, p < 0.01), environmental sensitivity (R 2 = 0.137, p < 0.01), and communication with nature (R 2 = 0.200, p < 0.01). Specifically, nature-relatedness directly enhanced environmental sensitivity (0.494 total effect), environmental behavior (0.604 total effect), and communication with nature (0.599 total effect) and did so both directly and indirectly through the mediation of flow experience. A higher level of nature-relatedness can lead to a stronger flow experience, which in turn can increase positive. environmental behavior, environmental sensitivity, and communication with nature.

Enhanced flow and heat transfer of aviation kerosene in porous media microchannels

The increasing turbine inlet temperature of the aero-engine requires higher heat transfer capability of the thermal management system. To improve the compactness of the air–fuel heat exchanger in the aero-engine, the heat transfer capability of kerosene can be enhanced by using porous media with a larger surface area per unit. Enhancement of supercritical RP-3 aviation kerosene heat transfer in microchannels by a porous structure and optimization of the structure to reduce pressure loss were investigated through experiments and numerical simulations. It is found that porous structures increase the heat transfer area by more than double, change the flow state, destroy the boundary layer structure, and produce more vortex and secondary flow. At the same time, the kerosene reaches the supercritical state earlier. These factors collaborate to enhance heat transfer with a local Nusselt number approximately six times. Filling the porous structure in the part where the flow has not been sufficiently developed is the main factor of heat transfer enhancement. The flow of the hexagonal shape is more uniform, and its heat transfer capability is better. Using alternating rotating porous microchannels can increase the local convective heat transfer coefficient by 18.6 %. And the optimized design of a partially filled porous microchannel can reduce the pressure loss by 40.7 %.

The effects of shared leadership perceived by soccer players on teamwork execution and flow state: Applying the IMO framework

The purpose of this study is to investigate how shared leadership, as perceived by players within a soccer team, influences teamwork execution and the state of flow. To achieve the objectives of this study, a purposive sampling method was employed, and soccer players registered with the Korea Football Association were selected as the research participants. Subsequently, data were collected using self-report surveys on shared leadership, teamwork execution, and flow state. Data from 415 participants were utilized for analysis, and data analysis was conducted using the SPSS 26.0 and AMOS 21.0 programs. Shared leadership was found to have a positive association with teamwork execution and the state of flow. Furthermore, the mediating effect of teamwork execution in the relationship between shared leadership and the state of flow was found to be significant. The results of this study emphasize the influence of leadership that is shared among team members rather than the effectiveness of individual leadership.

Patients with Acute Lower Limb Ischemia Continue to Have Significant Morbidity and Mortality

The treatment of acute lower limb ischemia (ALLI) has evolved over the last several decades with the availability of several new treatment modalities. This study was undertaken to evaluate the contemporary presentation and outcomes of ALLI patients. We retrospectively analyzed data from a prospectively collected database of all patients who presented to our tertiary referral hospital with acute ischemia of the lower extremity between May 2016 and October 2020. The cause of death was obtained from the Michigan State Death Registry. During the study period, 233 patients (251 lower limbs) were evaluated for ALLI. Seventy-three percent had thrombotic occlusion, 24% had embolic occlusion, and 3% due to a low flow state. Rutherford classification of ischemia severity was 7%, 49%, 40%, and 4% for Rutherford grade I, IIA, IIB, and III, respectively. Five percent underwent primary amputations, and 6% received medical therapy only. The mean length of stay was 11±9days. Nineteen percent of patients were readmitted within 30days of discharge. At 30days postoperatively, mortality was 9% and limb loss was 19%. On multivariate analysis, 1 or no vessel runoff to the foot postoperatively was associated with higher 30-day limb loss. Patients with no run-off vessels postoperatively had significantly higher 30-day mortality. Cardiovascular complications accounted for most deaths (48%). At 1-year postoperatively, mortality and limb loss reached 17% and 34%, respectively. Despite advances in treatment modalities and cardiovascular care, patients presenting with ALLI continue to have high mortality, limb loss, and readmission rates at 30days.

Effects of Immersive Straight Catheterization Virtual Reality Simulation on Skills, Confidence, and Flow State in Nursing Students.

Core nursing procedures are essential for nursing students to master because of their high frequency in nursing practice. However, the experience of performing procedures in actual hospital settings decreased during the coronavirus disease 2019 pandemic, necessitating the development of various contents to supplement procedural training. This study investigated the effects of a straight catheterization program utilizing an immersive virtual reality simulation on nursing students' procedural performance, self-confidence, and immersion. The study employed a nonequivalent control group pretest-posttest design with 29 participants in the experimental group and 25 in the control group. The experimental group received training through a computer-based immersive virtual reality program installed in a virtual reality hospital, with three weekly sessions over 3 weeks. The control group underwent straight catheterization using manikin models. The research findings validated that virtual reality-based straight catheterization education significantly improved students' procedural skills, self-confidence, and flow state. Therefore, limited practical training can be effectively supplemented by immersive virtual reality programs.

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.

Critical transitions on a route to chaos of natural convection on a heated horizontal circular surface

The transition route and bifurcations of the buoyant flows developing on a heated horizontal circular surface are elaborated using direct numerical simulations and direct stability analysis. A series of bifurcations, as a function of Rayleigh numbers ( $Ra$ ) ranging from $10^6$ to $6.0\times 10^7$ , are found on the route to chaos of the flows at $Pr=7$ . When $Ra&lt;1.0\times 10^3$ , the buoyant flows above the heated horizontal surface are dominated by conduction, because of which the distinct thermal boundary layer and plume are not present. At $Ra=1.1\times 10^6$ , a Hopf bifurcation occurs, resulting in the flow transition from a steady state to a periodic puffing state. As $Ra$ increases further, the flow enters a periodic rotating state at $Ra=1.9\times 10^6$ , which is a unique state that was rarely discussed in the literature. These critical transitions, leaving from a steady state and subsequently entering a series of periodic states (puffing, rotating, flapping and period-doubling) and finally leading to chaos, are diagnosed using two-dimensional Fourier transforms. Moreover, direct stability analysis is conducted by introducing random numerical perturbations into the boundary condition of the surface heating. We find that when the state of a flow is in the vicinity of critical values (e.g. $Ra=2.0\times 10^6$ ), the flow is conditionally unstable to perturbations, and it can bifurcate from the rotating state to the flapping state in advance. However, for relatively stable flow states, such as at $Ra=1.5\times 10^6$ , the flow remains in its periodic puffing state even though it is being perturbed.

Forgetting ourselves in flow: an active inference account of flow states and how we experience ourselves within them.

Flow has been described as a state of optimal performance, experienced universally across a broad range of domains: from art to athletics, gaming to writing. However, its phenomenal characteristics can, at first glance, be puzzling. Firstly, individuals in flow supposedly report a loss of self-awareness, even though they perform in a manner which seems to evince their agency and skill. Secondly, flow states are felt to be effortless, despite the prerequisite complexity of the tasks that engender them. In this paper, we unpick these features of flow, as well as others, through the active inference framework, which posits that action and perception are forms of active Bayesian inference directed at sustained self-organisation; i.e., the minimisation of variational free energy. We propose that the phenomenology of flow is rooted in the deployment of high precision weight over (i) the expected sensory consequences of action and (ii) beliefs about how action will sequentially unfold. This computational mechanism thus draws the embodied cognitive system to minimise the ensuing (i.e., expected) free energy through the exploitation of the pragmatic affordances at hand. Furthermore, given the challenging dynamics the flow-inducing situation presents, attention must be wholly focussed on the unfolding task whilst counterfactual planning is restricted, leading to the attested loss of the sense of self-as-object. This involves the inhibition of both the sense of self as a temporally extended object and higher-order, meta-cognitive forms of self-conceptualisation. Nevertheless, we stress that self-awareness is not entirely lost in flow. Rather, it is pre-reflective and bodily. Our approach to bodily-action-centred phenomenology can be applied to similar facets of seemingly agentive experience beyond canonical flow states, providing insights into the mechanisms of so-called selfless experiences, embodied expertise and wellbeing.

Towards autistic flow theory: A non‐pathologising conceptual approach

AbstractFlow states are heightened moments of concentration, motivation and enjoyment, leading to total absorption in the present moment. A striking parallel exists between flow states and phenomenological accounts of autistic daily life. We analyse the components of flow theory alongside autistic autobiographical accounts to explore similarities and differences, in doing so moving toward an understanding of autistic flow theory. We highlight the considerations and opportunities this may hold for future autism research, in particular the advantage that this offers a non‐pathologising approach to researching autism, one which helps to explain contextualised behaviour (i.e., alignment between the situation and what is happening in one's mind). Drawing on autistic autobiographical accounts, we outline four principles: (1) autistic people are uniquely placed to discover and manage flow; (2) autistic flow may qualitatively diverge from traditional models of flow; (3) difficulties maintaining and exiting flow for autistic people highlight a need to examine transitions into and out of flow; and, (4) internal and external constraints to flow highlight there is unrealised autistic potential yet to be discovered. The implications of an autistic flow theory are discussed in terms of how it can impact (a) our conceptual understanding of autism providing alternative explanations to previously researched phenomena, and (b) how we build enabling environments for autistic people that allow flow to flourish across educational practice, wellbeing and research contexts.

FSI Modeling and simulation analysis of superimposed valves in flow state of hydraulic shock absorbers*

Abstract This study, through rigorous bench testing, has identified the pivotal parameters influencing the oil flow state within the shock absorber. Based on the Reynolds number parameter model, a reduced parameter model was established, incorporating the number of holes in the throttle valve, their diameters, and the diameters of the piston and piston rod as fundamental parameters. To ensure the model’s precision, this study developed high-accuracy solid and fluid finite element models, defined specific time steps for both laminar and turbulent flows along with their respective numerical methods, and executed a detailed Fluid-Structure Interaction (FSI) finite element simulation analysis. The findings indicate that fluid-structure interaction simulation accurately captures the shock absorber oil’s flow states across laminar, transitional, and turbulent phases, identifying the maximum Reynolds number position, with the simulation’s velocity-specific results aligning closely with the parameter model, showing a maximum deviation of 22%, a minimum of 2%, and an overall average error of 9.1%.

Relationship between the Characteristics of e-Commerce Live Streaming and Purchase Intentions: Moderating Effect of Hedonistic Shopping Value

E-commerce live streaming has experienced a significant and rapid increase in recent years, establishing itself as a vital catalyst for the growth of the e-commerce business. This research delves into the influence of e-commerce live streaming attributes, namely, authenticity, interactivity, and entertainment, on consumers' purchase intentions. It is based on the Stimulus‒Organism‒Response (SOR) theory and focuses on customer flow experience and hedonic shopping value. To evaluate the study model, the authors gathered survey data from 360 live streaming e-commerce customers and used structural equation modeling. The results indicate that client purchase intentions in e-commerce live streaming are positively influenced by authenticity, interactivity, and entertainment. Authenticity, entertainment, and interaction all contribute to enhancing consumers' flow experience in e-commerce live streaming, with interactivity being the most influential factor. The phenomenon of flow experience has a beneficial impact on the purchasing intentions of clients engaged in e-commerce live streaming. The flow experience serves as an intermediary between the characteristics of e-commerce live streaming and consumers' intentions to make purchases. Hedonic shopping value affects the relationship between the flow experience and the customer's intention to make a purchase. Put simply, when customers have a strong perception of the pleasure they derive from shopping, their intention to make purchases becomes more profound when they are influenced by the state of flow. This study not only contributes to the body of knowledge regarding the correlation between the attributes of e-commerce live streaming and consumer receptiveness, but it also provides businesses and platforms that utilize e-commerce live streaming with actionable recommendations. By improving the content design of live streaming features in e-commerce, customer engagement and immersion are significantly enhanced, establishing a foundation for increasing consumer purchase intention. Doi: 10.28991/ESJ-2024-08-03-018 Full Text: PDF

Optimization of Cavitation Performance of High-Speed Centrifugal Pump Based on the Meta-Model of optimal Prognosis

Abstract Using a specific type of high-speed centrifugal pump as an example, this study conducted a parameterized optimization design on geometric parameters of the impeller’s flow path. A response sample space was generated with the flow path geometric parameters as input and pressure increment and cavitation volume as output. Based on the Meta-Model of optimal Prognosis, the optimal surrogate model was fitted, and a global sensitivity analysis was conducted. The results indicated that the impeller’s inlet edge parameter and mid-curve parameter had a significant impact on the pressure increment and cavitation volume of the pump. Using a genetic algorithm, the optimal flow path geometric parameters were obtained, and numerical simulation methods were applied to verify the obtained parameters. The results showed that after optimization, the pressure coefficient of the centrifugal pump increased by 0.035, and the cavitation performance improved by 22.28%. The impeller cavitation area and void volume were significantly reduced, and the flow path pressure distribution and flow state were improved.

Investigation on formation mechanism of cavitation channel vortex in the runner of Francis turbine

Abstract Cavitation channel vortices generally cause flow state more complex in the runner, leading to the work efficiency is reduced and the cavitation erosion on flow components is enhanced. In this paper, simulation of cavitation flow is carried out for a Francis turbine model, and the evolution of vortices in the runner during cavitation development is analyzed under partial load conditions. The results show that cavitation has a great influence on the morphology and distribution of attached vortices between blades, trailing vortices at the outlet edge of the blades, and vortex near the cone in the runner. With the gradual development of cavitation, the invasion effect of vortex rope in draft tube on the runner is enhanced, and the vortex near runner cone is gradually connected as a whole. Under the effect of the downstream reverse pressure gradient in local low-pressure area, the flow separation area gradually expands to the blade and upstream, and more singular points evolve on flow separation lines, which leads to more trailing vortices at the outlet of the blade and cavitation channel vortices are formed in serious cavitation stage.

Education for Sustainability Through Field Activities and Game-Based Tasks

Abstract There is a consensus that the content of education for sustainability should be integrated into the curriculum, engaging students in activities that promote awareness and practice of sustainability. To achieve this goal, it is essential to adopt a student-centered approach that involves creative, stimulating, and challenging activities. This research reports a case study in which 8th grade students had the opportunity to develop these types of activities. Field activities were conducted on a local river combined with a game-based task focused on the role of benthic macroinvertebrates in ecosystems. These activities enabled collaborative learning and the social construction of knowledge, which are pivotal for more sustainable education. It should be noted that students learned how to collect, observe, describe, organize, and classify species to make inferences about water quality. The main issue we intended to address was how to improve and integrate scientific activities into the students’ curriculum to foster a more sustainable education. The specific research questions were put forward: a) Do the implemented activities instigate collaboration for a more sustainable education? b) Do the implemented activities increase scientific curiosity and develop critical thinking and attitudes? c) Do the implemented activities increase students’ knowledge concerning aquatic resources, such as benthic invertebrates? The results confirmed the important role of student-centred activities, in this particular case fieldwork and game-based tasks, in the development of knowledge and scientific thinking skills, which could be scaffolded through feedback, rewards and flow states. This study provides a more holistic perception of local river ecosystems, their role in improving environmental attitudes, and promoting a more sustainable science education.

Examining the Feasibility of a Mindfulness Flow Program for the Hong Kong Archers

Mindfulness-based interventions have gained popularity among elite athletes, but their effectiveness in enhancing archery performance has been inconsistent. This study examined the feasibility of a 12-week mindfulness flow program (MFP) specifically designed for the archers and assessed the effect of the MFP on shooting performance. Twelve members of the Hong Kong Archery Team voluntarily participated in the present study. Their shooting performance, anxiety, mindfulness, and flow state were assessed before and after the MFP intervention. The results showed that the MFP was highly feasible, with 100% attendance. The athletes highly enjoyed the MFP sessions (mean rating: 7.9/10). Improved shooting performance, increased mindfulness, and flow state levels, and reduced anxiety were also observed after the intervention. These findings suggest a positive reception from and potential benefits for athletes. However, it is suggested to conduct additional research using randomized controlled trials to explore the program’s effects and applicability in enhancing sports performance.

Changes in the Remaining Iliac Artery According to Retrograde Flow after Aorto-Femoral Bypass in Abdominal Aortic Aneurysms

Considering a patient's anatomy and vascular conditions, aorto-femoral bypass is a treatment approach for the open repair of abdominal aortic aneurysms. This study aimed at evaluating changes in the remnant iliac artery and their correlation with the preservation state of retrograde flow from femoral anastomosis. Of 221 patients who underwent abdominal aortic aneurysm surgery between 2007 and 2022 in Pusan National University Hospital, 29 patients who underwent aorto-femoral bypass were included in this retrospective cohort study. Of these patients, 21 underwent aortobifemoral bypass and 8 underwent aortoiliac-and-femoral bypass. The change in size of the iliac artery from preoperative to postoperative and whether this difference in size depended on the status of postoperative retrograde flow were investigated. Additionally, factors affecting overall mortality and ischemic complications were identified. The median duration from operation to the last follow-up was 2069.5days (about 5.7years). The average age of the patients was 78.1years, and the proportion of males was 75.9%. In cases of disappearance of postoperative retrograde flow from the femoral anastomosis, the postoperative iliac artery size was significantly reduced compared to its preoperative size (18.4±18.9mm vs. 13.2±7.9mm, respectively; P=0.04). The group with maintained retrograde flow had significantly larger residual common iliac artery size than the group with disappearance of flow. (20.0±28.0mm vs. 14.6±8.5mm, respectively; P=0.02). Disappearance of retrograde flow was a significant factor in the iliac artery size reduction after surgery (odds ratio, 2.5; 95% confidence interval, 1.9-5.3; P=0.02). Three patients with maintained retrograde flow (18.8%) required intervention owing to an increase in the size of the iliac artery. The factors that significantly influenced overall death as analyzed by Cox proportional hazard regression were chronic obstructive pulmonary disease (hazard ratio, 36.8; 95% confidence interval, 1.6-870.0; P=0.03), peripheral arterial occlusive disease (hazard ratio, 12.7; 95% confidence interval, 1.4-115.8; P=0.02), and disappearance of retrograde flow (hazard ratio, 8.7; 95% confidence interval, 1.2-63.9; P=0.03). Among the open repair methods for abdominal aortic aneurysms, if retrograde flow was not maintained through femoral anastomosis when aorto-femoral bypass was performed, the size of the remaining iliac artery decreased. However, loss of retrograde flow increased long-term mortality. When aorto-femoral bypass is performed, regular imaging follow-up is necessary at appropriate intervals to check the remnant iliac artery and retrograde flow.

Economic analysis of offsite and onsite 3D construction printing techniques for low-rise buildings: A comparative value stream assessment

In comparison with traditional construction, 3D construction printing (3DCP) has the potential to be cost-effective due to its shorter supply chain and higher level of automation. Previous studies suggested that offsite 3DCP can be more capital-intensive than onsite 3DCP. Thus, there is a need for comprehensive research on the comparative economic analysis of offsite and onsite 3DCP techniques. Therefore, this study aims to investigate the overall construction cost of both techniques. In this regard, the Value stream assessment technique has been used to map the current state of the material flow from the supplier to the construction site. For the detailed cost analysis, mathematical models have been developed that consider transportation, warehousing, setup installation, printing, onsite assembly, and environmental costs based on the current state of Value stream mapping (VSM). The feasibility and practicality of the developed models have been validated through real-time case studies. Results from the cost breakdown analysis and cost based VSM show that offsite 3D printing leads to higher construction costs due to the significant contribution of warehousing costs for pre-printed components and the cost of assembling them. Cost based value stream assessment depicts that offsite and onsite 3DCP have a significant amount of non-value added cost (284.26 €/tonne and 199.05 €/tonne, respectively) and offer more space for process improvement. However, sensitivity analysis revealed that offsite 3DCP has the potential to reduce the transportation cost for small-scale projects involving low volume (<130 tonnes) of construction materials. Onsite 3D printing can be a feasible option for relatively larger projects due to its lower transportation, warehousing and construction costs. The findings of this research offer the construction industry a strategic roadmap to achieve cost-effectiveness and efficiency in construction practices.