Circular Flow Research Articles

The Cyclical Dynamics of National Income: Understanding the Circular Flow of Income

The Cyclical Dynamics of National Income: Understanding the Circular Flow of Income

The Cyclical Dynamics of National Income: Understanding the Circular Flow of Income in the Philippines

The Cyclical Dynamics of National Income: Understanding the Circular Flow of Income in the Philippines

Flow instabilities in circular Couette flow of wormlike micelle solutions with a reentrant flow curve

In this work, we numerically investigate flow instabilities of inertialess circular Couette flow of dilute wormlike micelle solutions. Using the reformulated reactive rod model (RRM-R) (Hommel and Graham, 2021), which treats micelles as rigid Brownian rods undergoing reversible scission and fusion in flow, we study the development and behavior of both vorticity banding and finger-like instabilities. In particular, we focus on solutions that exhibit reentrant constitutive curves, in which there exists some region where the shear stress, τ, has a multivalued relation to shear rate, γ̇. We find that the radial dependence of the shear stress in circular Couette flow allows for solutions in which parts of the domain lie in the region of the flow curve where ∂τ/∂γ̇>0, while others lie in the region where ∂τ/∂γ̇<0; this mixed behavior can lead to complex flow instabilities that manifest as finger-like structures of elongated and anisotropically-oriented micelles. In 3D simulations we find that the initial instability is 2D in origin, and 3D finger-like structures arise through the axial instability of 2D sheets. Finally, we show that the RRM-R can capture vorticity banding in narrow-gap circular Couette flow and that vorticity bands are linearly stable to perturbations.

Heat transfer characteristics of PCM slurry using ammonium alum and propylene glycol

For latent heat transportation at temperatures higher than room temperature, a phase change material slurry using ammonium alum, propylene glycol (PG), polyvinyl alcohol (PVA), cationic surfactant, and sodium salicylic acid was proposed. The slurry's phase change characteristics changed with the fraction of PG. In this study, we first confirmed whether PVA and surfactants affected the slurry's phase-change characteristics and viscosity. The results showed that the phase-change characteristics were unaffected, but the viscosity changed to that of a non-Newtonian fluid. Owing to these characteristics, the PVA/surfactant demonstrated a drag-reduction effect in the flow characteristic measurement in a circular pipe flow. However, the drag reduction effects decreased when the PG fraction was large. Using these slurries, heat transfer measurements were performed using a double-tube heat exchanger with an 8-mm inner tube diameter. The samples in the inner tubes were cooled with water. It was observed that the latent heat of ammonium alum enhanced heat transfer and a model of the heat transfer characteristics using the modified Prandtl number was proposed. Finally, the heat transportation efficiency was examined, and it was determined that efficient heat transportation using ammonium alum was feasible under certain PG fraction and flow velocity conditions.

Synergy of green energy technologies through critical materials circularity

Synergies between technology flows is essential to balance the consumption of their related critical materials and promote a sustainable green economy transition. Using dynamics modelling, a comprehensive analysis of silicon flows applied in green energy technologies such as photovoltaic (PV) solar panels and lithium-ion batteries (LiBs) is provided. The results show that appropriate allocation of the circular flows of different silicon grades can become an effective global solution for saving material, energy and water as well as mitigating greenhouse gas (GHG) emissions. About 15 % of required global silicon could be provided by secondary production from end-of-life green energy technologies by 2030. Recovering metallurgical, solar and electronic grades of silicon from global end-of-life PVs compared to its primary production will lead to savings of 3.5 billion GJ of energy, 3.1 million m3 of water and over 65 Mt CO2 eq of GHG emissions globally by 2030. Also, synergies between material flows from PVs waste to advance LiBs production aims to save around 38 M GJ of energy and 0.01 million m3 of water and mitigate 4 Mt CO2 eq of GHG emissions through secondary production practices by 2030. The findings outline a systematic solution for environmental sustainability of recycling by suggesting optimized integrated material flows of recovery of 50 % metallurgical, 25 % solar and 25 % electric grades of silicon from global end-of-life PVs.

Bridging the Implementation Gap between Pomace Waste and Large-Scale Baker’s Yeast Production

The objectives set in the European Green Deal constitute the starting point of this review, which then focuses on the current implementation gap between agro-industrial wastes as resources for large-scale bioprocesses (e.g., baker’s yeast, bioethanol, citric acid, and amino acids). This review highlights the current lack of sustainability of the post-harvest processing of grapes and apples. In light of the European Green Deal, industrial biotechnology often lacks sustainability as well. We reviewed the recent progress reported in the literature to enhance the valorization of grape and apple pomace and the current failure to implement this research in technical processes. Nevertheless, selected recent papers show new perspectives to bridge this gap by establishing close collaborations between academic teams and industrial partners. As a final outcome, for the first time, we drew a circular flow diagram that connects agriculture post-harvest transformation with the industrial biotechnology and other industries through the substantial valorization of apple and grape pomace into renewable energy (solid biofuels) and sugar extracts as feedstock for large-scale bioprocesses (production of baker’s yeast industry, citric acid, bioethanol and amino acids). Finally, we discussed the requirements needed to achieve the successful bridging of the implementation gap between academic research and industrial innovation.

Dynamics and dispersion of inertial particles in circular cylinder wake flows: A two-way coupled Eulerian–Lagrangian approach

In this paper, the motion of inertial particles in three-dimensional (3D) unsteady cylindrical wake flow is investigated by a two-way coupled Eulerian–Lagrangian approach. At different flow Reynolds numbers (Re), the corresponding striking dynamic property and dispersion mechanism of four particle classes have been studied, with inertia parameterized by means of Stokes number (Sk). It is found that inertial particles with lower Stokes number are expelled from vortex cores, and coherent voids encompass the local Kármán vortex cells. As Stokes number increases, a low velocity particle channel could be formed, which almost coincides with the results in the literature. Moreover, with the increase of Reynolds number, numerous irregular coherent voids are observed in the cylinder wake, and the high-speed particles follow the fluid flow closely when they are contained in the vortices. Although the centrifugal force of Kármán vortex cells significantly affects the dynamics of inertial particles, the fluid flow modulation is believed to be responsible for the distinctive particle dispersion patterns in the vortex streets. For particles with medium inertia, the two-way coupled modulation weakens the centrifugal effect of vortex structures on the particles. This trend declines with the increase of Reynolds number, and vanishes with light particles, while both two-way coupled modulation and the centrifugal effect of vortex structures are almost equally effective with heavy particles. The investigations contribute to a better understanding of the particle-laden flows in practical applications, which will benefit the optimized design of certain machinery and equipment for the industry.

Navigating uncertainty: exploring electricity demand dynamics in Swedish industrial sectors amid global shocks and instability

This study aims to provide insights into the factors shaping electricity demand in Swedish industrial sectors using the nonlinear version of the autoregressive distributed lag model (NARDL). This approach captures the complex short- and long-run relationships between uncertainty and electric power use in Swedish industrial sectors. The results reveal sector-specific responses to uncertainties and asymmetries in electricity use patterns. By examining the entire industrial sector in Sweden, this approach uncovers underlying issues and hidden patterns, while also providing insights into the functioning and behaviour of industrial systems. The rapid electrification and new green industrialisation initiatives in Sweden, coupled with the integration of a circular economy, underscore the importance of understanding the dynamics of electricity use in the face of uncertain shocks. This knowledge is vital for ensuring, amongst other things, grid stability, mitigating the need for costly peaking capacity, and identifying potential challenges in the interconnection of energy and material circular flows.

Lean-circular maturity model (LCMM) for companies' self-assessment in terms of process, product and life cycle thinking

Rapidly diagnosing the status of resource efficiency and waste generation throughout the entire value chain is considered one of the key future advancements towards achieving more sustainable production. This study aimed to develop and implement a self-assessment tool to assist companies in decision-making processes for establishing circular flows based on the principles of Lean Manufacturing (LM) and Circular Economy (CE). The self-assessment tool employed a maturity model comprising several stages, which were designed through a combination of design science research and scenario planning. The Lean-Circular Maturity Model (LCMM) consisted of maturity levels ranging from 0 to 4, assessing strategies such as Resource Efficiency, Energy Management, Water and Wastewater Management, Materials and Solid Waste Management, and Chemicals and Emissions Management. The model was applied to nine companies varying in sector, size, region, and nationality. Their engagement in LM, and CE, differed, as did their strategy maturity metrics. Primary sector companies showed higher maturity in water-waste and chemical-emissions management. Larger enterprises focused on these strategies, with nuances based on region. The main findings indicated that 66% of the companies sought cleaner alternatives prior to mapping their production processes, which could lead to errors in planning and prioritizing improvement actions. Furthermore, 61% of the companies lacked sufficient training and employee awareness regarding the efficient utilization of resources. The absence of comprehensive actions to manage the life cycle of products throughout the value chain emerged as the primary barrier identified. To address these gaps, the LCMM offers a set of tailored recommendations for each company to enhance processes, products, and the value chain based on the final score obtained from utilizing the LCMM self-assessment tool.

Design and Structural Optimization of Electrically Controlled Throttle Valve Core for Stratified Injection

In order to solve the problems of poor regulation of throttling pressure drop and excessive viscous friction in electrically controlled throttle valves in stratified injection, a new valve core structure that can efficiently regulate pressure drop and reduce viscous friction is designed. An effective valve core simulation model is established, and the model is divided into grids for fluid dynamics simulation. The pressure drop and shear rate of three commonly used valve and throttle structures are compared comprehensively based on the simulation results. The optimal circular arc flow channel structure is selected, and the influence of the length of the circular arc structure on the shear rate is simulated. Compared with 20mm, 25mm and 30mm, the best effect was obtained when the valve joint length is 30mm.The experimental results show that the average viscosity of the optimized valve core is less than 11%, which reduces the viscosity loss.which provided theoretical support for the optimization of layered injection tool.

Investigation of the cooling performance of a double-layer liquid-cooled plate with circular arc-shaped flow channels for thermal management of light-emitting diodes

Since the integration and heat flux of high-power light-emitting diodes (LEDs) are continuously increasing in response to the rising demand for illumination, high-power LEDs require a sophisticated thermal management system to ensure stable operation and prolonged service life. In the present work, a double-layer liquid-cooled plate with circular arc-shaped flow channels was developed. Circular arc-shaped flow channels may help the fluid flow against the channels' wall more effectively by preventing the development of eddy and impact flow and minimizing flow resistance. Combining it with the double-layer design may conduct cooling in the hot spot area twice as effectively. Numerical analysis and experimentation were conducted to explore the hydraulic properties and cooling performance of the plate, and the LED chips' arrangement schemes were examined. Water and ethylene glycol solutions with varying mass concentrations are utilized as the working fluids. The pin temperatures and illumination characteristics of LED chips were assessed after being cooled using the created plate at various flow rates. The results demonstrate the advantages of the proposed liquid-cooled plate's flow characteristics and cooling capability. After cooling, the LED chips' pin temperatures may be kept below 50 °C. When the flow rate was increased from 0.03 L/min to 0.18 L/min and the operating power of the LEDs was 300 W, the luminous intensity of the chips rose by 1440–1680 lx. Based on the temperature of the surrounding environment, the appropriate working fluid should be employed in practical applications. Furthermore, when the j/f coefficient is large, less pump work is needed, and the plate cools more effectively. It satisfies the need for a lightweight cooling system because the produced liquid-cooled plate weighs only 200 g.

Circular flow number of Goldberg snarks

A circular nowhere-zero r-flow on a bridgeless graph G is an orientation of the edges and an assignment of real values from [1,r−1] to the edges in such a way that the sum of incoming values equals the sum of outgoing values for every vertex. The circular flow number of G is the infimum over all values r such that G admits a circular nowhere-zero r-flow. We prove that the circular flow number of Goldberg snark G2k+1 is 4+1/(k+1), proving a conjecture of Goedgebeur, Mattiolo, and Mazzuoccolo.

The effect of a reversed circular jet impingement on A bifacial module PVT collector energy performance

Photovoltaic thermal (PVT) technologies have a significant downside in addition to their numerous advantages. PVT technologies are constrained by the fact that its photovoltaic module gains heat due to exposure to solar irradiance, which reduces the photovoltaic efficiency. Jet impingement is one of the most effective methods to cool a photovoltaic module. An indoor experiment using a solar simulator was conducted on a bifacial PVT solar collector cooled by a reversed circular flow jet impingement (RCFJI) to evaluate the energy performance of the PVT collector. The study was conducted under a constant solar irradiance of 900W/m2 and flowrate (mass) ranging from 0.01 to 0.14 kg/s. Three bifacial modules with 0.22, 0.33, and 0.66 packing factors were mounted 25 mm above the RCFJI for cooling. The 0.66 packing factor module recorded the highest photovoltaic efficiency of 10.91 % at 0.14 kg/s flowrate (mass). Meanwhile, the 0.22 and 0.33 packing factors recorded a photovoltaic efficiency of 4.50 % and 6.45 %, respectively. The highest thermal efficiency recorded under the same operating condition was 61.43 %, using a 0.66 packing factor. Overall, the highest combined photovoltaic thermal (PVT) efficiency for 0.22, 0.33, and 0.66 was 56.62 %, 61.88 %, and 72.35 %, respectively.

Research on the Environmental and Economic Repercussions and Policy of Electric Cars

The primary policies nowadays in effect are either zeroing in on the work of popularizing and enhancing EV manufacturing incidence, setting an un-negotiable quota for firms to compromise on that leaves them no leeway, or just issuance of waivers and subsidies. Given that charging takes an inordinate amount of time that most find fazing, as a self-explanatory result, the government ought to inject a prudently weighed amount of expenditure into the circular flow of income as one of many workable fiscal policies and bidding their time for the multiplier effect to play out. For example, the provision and installment of charging points need to be ramped up in each engaged polities to broker an appropriate EVs-chargers ratio. Therefore, the government should dispose of manufacturers to rev up production. That way, convenience inducement is conducive to more uptake of prime EVs customers. Additionally, a stipulation must be choreographed concerning the uniformity in the topology of all the necessary appurtenances incorporated in a charger to warrant the utilization of all possible chargers irrespective of their manufacturer, as the denial of access to charging points surely would repel practitioners inquisitiveness.

SUSTAINABILITY OF SUGARCANE BAGASSE AS NATURAL FIBRE COMPOSITE PRODUCTS IN YIWU COMMUNITIES: A CONCEPTUAL FRAMEWORK

Global warming, white pollution, ecological degradation and other environmental and resource issues have become the focus of attention in all areas of society today, and sustainable development is no longer a slogan. Design practitioners are committed to developing new visions and approaches. The application of materials is an important part of realising a circular economy. Sugar cane is the world's number one sugar crop and the second largest bioenergy crop, while bagasse is one of the most produced agricultural wastes in the world. This study is located in the hometown of brown sugar in China - Yiwu City, Zhejiang Province. The research objective is to develop the design and application of bagasse fibre composites in the brown sugar industry of Yiwu using waste bagasse materials as a starting point. The aim is to use design to drive the circular flow of waste resources, extend the economic chain of the brown sugar industry, and help build a local ecological civilisation and sustainable economic development. The researcher used theoretical framework, qualitative research and data analysis as research methods. In this study, the theoretical framework of sustainable development of the brown sugar industry in Yiwu is proposed, and the circular path diagram of the brown sugar industry ecological park. With theory guiding practice, and successfully developed bagasse paper material and bagasse bioplastic material and applied them in the field of lamps and brown sugar product packaging.

Modulation of wake evolution, separation, and radiated noise by a cylinder with porous media cladding

In this paper, the effects of porous media parameters on circular cylinder wake flow and radiation noise are investigated using large eddy simulations and Ffowcs Williams–Hawkings acoustic analogy. We performed three-dimensional numerical simulations for flow around the cylinder coated with a porous layer of different pores per inch in a subcritical flow regime (ReD=4.7×104) to explore the control mechanism of porous media on wake and radiation noise. The results show that the application of porous media significantly alters the separation pattern behind the cylinder and stabilizes the shear layer detached from the cylinder. The existence of porous layers leads to the transformation of chaotic and irregular vortex structures into more orderly vortices. Moreover, this study also reveals that the cylinder coated with high pore density can provide the desired noise reduction. The analysis of vortex sound theory indicates that porous media reduces the interaction area and magnitude of the positive and negative Lamb vector divergences, which is beneficial for drag reduction and noise attenuation. In addition, the comparison of sound pressure contours shows that the application of porous media does not change the radiation mode of noise, but the porous media with high pore density helps to decrease the generation of noise and intensity of the sound source.

Identification and Minimization of Waste with the Application of Lean Manufacturing in the Cireng Production Process at PT Brecxelle Berkah Uniti

Based on the results of observations and the 7 waste questionnaires at PT Brecxelle Berkah Uniti production, it was found that the waste of defects occurs such as cireng are shapeless, destroyed, and do not pass through the metal detector machine. Waste of waiting occurs during the cooling process, when starting the engine, and waiting for the pressing process. Waste of transportation occurs due to circular and non-consecutive process flows. This research aims to minimize production time and increase production result by simulating the cireng production process of PT Brecxelle Berkah Uniti using the Lean Manufacturing and System Simulation method. Based on the simulation results with the proposed improvements, the results obtained from the simulation were that the total production lead time was reduced by 10,97 minutes from 40.45 minutes to 29,48 minutes. The NVA and NNVA time on FVSM also decreased by 10.81 minutes from the activity time on CVSM. Based on the simulation results, production results increased by 80% after the proposed improvements, from 4,671,945 pcs per month to 8.429.679 pcs per month.

Effects of solidification on flow dynamics: A novel comprehension of defects formation in laser penetration welding

The laser penetration welding for medium-thickness plates struggles with unstable molten pool behavior and a limited processing window, often leading to welding defects including spatters, depressions, and especially humps. In this study, forming processes of the defects were observed by using a high-speed camera, and forming mechanism of the defects were then analyzed in detail by simultaneously considering the influences of force and solidification. It was clear that the mass loss caused by spattering during the heating phase contributed to the depression, which was consistent with the existing knowledge. However, the formation mechanism of humps concluded in this study was different to the present understanding. Apart from the influences of force, the effects of solidification on molten pools and humps were analyzed. Under the specific conditions, middle part of molten pool solidified rapidly, causing localized necking, and disrupting the circular flow of the molten metal. As a result, molten metal once flowed downward due to the gravity and temperature can no longer refill to the upper part again, leading to the accumulation of molten metal at lower part and ultimately the formation of humps. These findings offered a fresh perspective on the formation of hump, provided valuable guidance for enhancing the quality and efficiency of thick-plate laser welding.

Heat transfer enhancement using combined microchannel with vertical rectangular micro fins

This paper focuses on the numerical optimisation of a combined hybrid microchannel heat sink with rectangular solid fins. The axial length and volume are fixed, and external structure is allowed to vary. The simulation was performed on an elemental unit cell of the microchannel heat sink . The purpose of the optimisation is to discover an optimal geometric arrangement in internal and external configurations that minimises peak temperature in the microchannel heat sink. A high-density uniform heat flux of 250 W/cm2 is assumed to be dissipated on the bottom wall of the unit cell by microelectronics circuit boards devices. Computational fluid dynamic code was used to discretized the fluid domain and solve a set of governing equations. The influence of hydraulic diameter, external structural shape and fluid velocity on peak temperature and global thermal resistance, is discussed. Coolant or water of Reynolds number range 400 to 500 in a forced convection laminar flow is introduced through the inlet of the computational domain to remove the heat at the bottom of the rectangular block microchannel. The results show that when the fluid velocity is increased from 9.8 to 12.3 m/s across the axial length of the micro heat sink, more heat is removed from the bottom of the combined heat sink. The results revealed that the pump power increased by 37.1% in combined microchannels with fins and from by 27.2% in finless micro heat sink. The result of the study is validated with what is documented in open literature for a traditional micro heat sink with circular flow channel and the trends agree.

Analytic solutions for quasi-3D seepage in a shallow unconfined aquifer as a plane composed of a transpiration-inducing park and its hydraulically commingled exterior

Strack’s (1984, 2017) analysis of infiltration from a pond into a shallow aquifer, with a generated groundwater mound, is modified for steady phreatic groundwater flows in perched aquifers, typical for arid/hyperarid environments, with a zone of intensive transpiration and induced groundwater trough. The interior of an urban phreatophytic park is an n-polygon (in an aerial view), which degenerates into a circle at n→∞. Transpiration acts as an areal groundwater sink. The water table drawdown is hydrologically symmetric with Strack’s drawup. In the exterior of the park, the ground surface is phyto-sterile (e.g. a desert in Arabia or a paved megapolis) and evapotranspiration from the water table there is ignored. The travel (residence) time of advected marked particles along the flowpaths (streamlines) towards the park and under it are analytically evaluated. In terms of the Dupuit-Forchheimer model of a vertically averaged hydraulic head, the Strack potential obeys the Laplace and Poisson equations in polygon’s exterior and interior (correspondingly), with a hydraulic commingling along the park boundary. The tracer particles start their topologically converging journey from a remote circular zone of contamination (e.g. sewage from urban septic tanks recharging the water table). Porosity, hydraulic conductivity of the aquifer, evapotranspiration rate and a piezometric head in a remote observational well are given. For a circular park flow is 1-D radial. In the park exterior, the Schwarz-Christoffel formula maps conformally the physical domain (an infinite trigon) onto a half-strip in the complex potential plane. Strack’s potential is expressed via hypergeometric functions, whose parameters depend on n. The flow net is reconstructed with the help of the stream function. For a triangular park interior, there is no stream function and the Saint-Venant solution to the Poisson equation is engaged to find the water table, hydraulic gradients, and discharge streamlines. The total dewatered volume and groundwater storage under the water table and “gross travel time” are evaluated for circular parks. Implications for ecohydrology of parks and desert oases in the Gulf countries and intuitive isoperimetric problems are discussed.