Parallel Flow Research Articles (Page 1)

Background: Atherosclerosis occurs preferentially in regions of disturbed or low fluid shear stress (FSS), whereas physiological laminar FSS protects against disease by suppressing endothelial inflammation. Pro- vs anti-inflammatory programs are associated with glycolysis vs mitochondrial metabolism, respectively. Endothelial cells (ECs) sensing FSS from blood flow regulates these responses, but the underlying mechanisms are poorly understood. The transcription factor Forkhead box protein O1 (FOXO1) is known to regulate endothelial metabolism, yet its role in FSS-regulated endothelial inflammation remains largely unclear. Methods: In vitro, ECs were subjected to defined flow patterns using a parallel plate flow chamber. Immunofluorescence, RNA sequencing, and biochemical assays were used to evaluate FOXO1 localization, gene expression, and post-translational modifications. In vivo experiments used FOXO1 floxed mice crossed with Bmx-CreERT2 for artery ECs-specific FOXO1 knockout. Hyperlipidemia was induced via injection of PCSK9 adeno-associated virus and high-cholesterol/high-fat diet (HCHFD) to assess atherosclerosis. Results: Oscillatory FSS and inflammatory cytokines induce, whereas physiological FSS inhibits FOXO1 nuclear translocation. RNA sequencing revealed that FOXO1 depletion in ECs upregulates the protective flow-responsive transcription factors KLF2/4 and reduces oscillatory FSS-induced inflammatory genes. Inhibition of FOXO1 nuclear translocation by physiological FSS is mediated via a KLF2-CDK2 pathway, with the latter phosphorylating FOXO1 at S249. Artery ECs-specific deletion of FOXO1 significantly reduces atherosclerotic plaques formation in hyperlipidemic mice. Inhibition of glycolysis attenuates OSS-induced FOXO1 nucleus translocation, suggesting metabolic regulation. Notably, treatment with lactate promotes FOXO1 nuclear localization and lactylation, which is mediated by a lactyltransferase AARS1 (Alanyl-tRNA synthetase). Conclusions: These findings identify FOXO1 as a key mediator linking atheroprone flow and endothelial inflammation via lactate-driven nuclear translocation and lactylation, promoting atherosclerosis. Conversely, physiological FSS suppresses FOXO1 via KLF2-CDK2 signaling. These complementary pathways suggest potential new therapeutic targets for treating atherosclerotic cardiovascular disease.

A single bout of exercise improves muscle insulin sensitivity for up to 48 hours via AMPK. Limb ischemia activates AMPK in muscle, and subsequent reperfusion enhances insulin-stimulated vasodilation, potentially eliciting a more pronounced exercise effect with reduced workload. We investigated the combined effect of upper leg intermittent ischemia/reperfusion (IIR) and continuous knee-extension exercise on muscle insulin sensitivity regulation. We found that IIR exercise potentiated AMPK activation and muscle insulin sensitivity. The potentiating effect of IIR exercise on muscle insulin sensitivity was associated with increased insulin-stimulated blood flow in parallel with enhanced phosphorylation of endothelial nitric oxide synthase. Metabolomics analyses demonstrated a suppression of muscle medium-chain acylcarnitines during IIR exercise, which correlated with insulin sensitivity and was consistent with findings in isolated rat muscle treated with decanoyl-l-carnitine. Collectively, combining IIR with low- to moderate-intensity exercise may represent a promising intervention to effectively enhance muscle insulin sensitivity. This approach could offer potential for mitigating muscle insulin resistance in clinical settings and among individuals with lower physical activity levels.

This study explores the formation dynamics of Boger (or near-Boger) and Newtonian droplets with matched shear viscosities in a flow-focusing microchannel. The viscoelastic dispersed phases—200 and 400 ppm polyacrylamide in aqueous glycerol—exhibited near-constant viscosities of 104 and 126 mPa s, respectively. The continuous phase was a surfactant-laden Newtonian transformer oil (30 mPa s). By isolating elasticity from other non-Newtonian effects, we demonstrate its pronounced influence on droplet generation, even at low Capillary numbers (on the order of 10−4 to 10−3). Four distinct breakup regimes were identified: Parallel flow (PF), Dripping (D), Jetting (J), and the viscoelastic-specific beads-on-a-string (BOAS) structures. Elasticity notably suppresses the dripping regime while expanding the jetting domain, where BOAS structures emerge. Regime maps reveal that jetting broadens with increased continuous-phase flow rate (Qc) and contracts with higher dispersed-phase flow rate (Qd). Elasticity also transforms the satellite-droplet formation mechanism. Instead of shedding tiny droplets, the stabilized filament breaks into large secondary droplets comparable to the primary ones. This stabilizing effect is quantitatively confirmed by a threefold increase in normalized jet breakup length. Overall, this research demonstrates that the final fracture morphology is governed by the Elastocapillary number (Ec), which quantifies the competition between stabilizing elastic stresses and destabilizing capillary forces. This provides a predictive framework for understanding and controlling the droplet generation process in complex non-Newtonian multiphase systems.

In this work, a Lorentz collision operator is implemented in the NLT code. This module uses the 4th order accurate finite-difference scheme and a correction algorithm, which suppresses the spurious diffusion and ensures the numerical conservation properties, respectively. Neoclassical parallel electrical conductivity and neoclassical ion thermal conductivity cases are tested, and the simulation results agree well with the theory. Finally, the formation of the parallel return flow through the ambipolar radial electric field and the collisional relaxation to the rigid-body toroidal rotation are further investigated.

Parallel Flow Velocity Shear Kelvin-Helmholtz Instability with Latitude Variation of Magnetic Field and Inhomogeneous DC Electric Field in Jovian Magnetosphere

The wall properties of cerebral aneurysms, whether thin or thick, cannot be determined using conventional imaging techniques. We previously reported that two parameters, wall shear stress vector direction variation (WSSDV) and oscillatory shear index (OSI), may predict the wall-thinning areas of cerebral aneurysm walls in computational fluid dynamics (CFD) analysis. In this study, we evaluated the positive predictive value (PPV) of these parameters in detecting thin-walled regions (TIWRs) and thick-walled regions (TKWRs) by performing preoperative CFD analysis and proposed that distinct flow patterns determine aneurysm wall thinning or thickening. A total of 42 microsurgical clipping surgeries for unruptured intracranial aneurysms (UIAs) were performed at our hospital between January 2019 and August 2022 without any deterioration of the modified Rankin scale in all patients. We identified 39 actual TIWRs (aTIWRs) in the intraoperative photographs of the aneurysms among 46 expected TIWRs (eTIWRs) of the color maps (PPV: 85%; 95% CI 0.72-0.92), 23 actual TKWRs (aTKWRs) among 29 expected TKWRs (eTKWRs, PPV: 79%; 95% CI 0.62-0.90) on the WSSDV color maps, whereas the OSI color map revealed 39 aTIWRs among 46 eTIWRs (PPV: 85%; 95% CI 0.72-0.92) and 30 aTKWRs among 45 eTKWRs (PPV: 67%; 95% CI, 0.52-0.79). Spearman's rank correlation analysis revealed a strong correlation between the WSSDV and OSI (Spearman's ρ = 0.849, 95% CI 0.73-0.92, p < 0.001). These two parameters reflected the degree of wall shear stress vector change during the cardiac cycle. Parallel or divergent flows may cause aneurysm wall thinning, whereas rotational or convergent flows may cause wall thickening.

In this paper, the heat exchange processes between a cold (oil) and a highly heated (water) heat carrier in a“tube-in-tube” type heat exchanger with a parallel flow scheme are studied using semi-empirical turbulencemodels: k-ω SST, k-ε, and Transition SST. The analysis of the obtained results showed that the k-ω SSTturbulence model was more preferable for the calculation of a heat exchanger with a sufficiently small tubediameter, because of the effect of the boundary layer in the tube. This turbulence model more pronouncedlyreproduces the laminar-turbulent transition, which is carried out in these processes, where the viscosity of oilstrongly depends on temperature. Finite difference and finite volume methods were chosen for numericalmodelling and calculation of heat exchange processes. The calculations were carried out on the basis ofComputational Fluid Dynamics, using the Ansys Fluent. The RANS equations closed by means of thegamma-Retheta turbulence model, which takes into account the laminar-turbulent transition and the k-ω SSTmodel equations, were used for numerical modelling of coolant hydrodynamics. Based on the proposedturbulence model, the distributions of hydrodynamic and thermal parameters and similarity criteria (Re, Pr,Nu) of the process along the length of the tube are obtained.

Introduction. The BPMN standard system (notation) is widely used in business process modeling. However, it is not expressive enough to represent technical and production mechanisms. BPMN poorly describes parallel flows with strict resource constraints, insufficiently supports modeling of physical parameters and technological conditions. These and other shortcomings worsen the analysis of performance and reliability, reduce the applicability of models for optimization and verification. The objective of the presented work is to create a method that uses an alternative notation and thus limits the impact of the listed shortcomings of BPMN in modeling production processes.Materials and Methods. The basis of the new solution was a comparison of BPMN and the notation for the system “node – function – object” (NFO). The elements of the diagrams were the intersections of some connections (nodes). They contained functional elements (functions, processes), which in some cases also had the characteristics of a substance (objects). A comparative analysis of the normative systems of BPMN and NFO showed the possibility of mutual transformation of diagrams. The processes were visualized using the CASE (Computer Aided Software Engineering) tool NFO-toolkit and the Stormbpmn program according to the BPMN rules. The NFO diagram was described in the XPDL2 language.Results. Six sequential operations have been developed for converting a NFO diagram into BPMN, and four — for the reverse transformation. The scheme of component production is shown in the context and decomposition, from the requirement for the development of the workflow to the issuance of products. Decompositions of the NFO elements “Injection Molding Machine”, “Master” and “Development Department” are presented, each of which corresponds to a decomposition of the same-name track of the BPMN notation pool. It has been proven that converting a BPMN diagram to a NFO improves the description of the process as a whole and to any degree of detail. The NFO approach does not refer to the graphical notation system of BPMN, which increases labor costs and the risk of simulation errors. The XPDL language describes processes, connectors, splitters, relationships, external entities, and other elements of NFO diagrams.Discussion. The main advantages of NFO notation over the BPMN approach are: easier procedure for creating models and their better visualization. A simple graphic set of NFO reduces simulation time and increases its accuracy. The NFO approach is focused on taking into account information and material connections. This means that it is possible to conduct functional cost CASE analysis, which is impossible using the BPMN method. The XPDL language is suitable for describing elements of NFO diagrams, and the solution can be Russified.Conclusion. Content redundancy and other shortcomings of the BPMN notation are eliminated through using a more universal and convenient notation — NFO. The research results will contribute to the development of the theory and practice of graphanalytic modeling of production processes, and simplify the procedure for their development and automation.

Insulated Gate Bipolar Transistor (IGBT) modules are a frequently used switching and power control element in power electronics. A significant amount of heat is released due to conduction and switching losses inside the module. To ensure the efficient and long-term operation of the IGBT, the heat generated must be cooled effectively. Forced liquid cooled cold plates are widely used for high power density modules. In this study, a cold plate is designed for liquid cooling of three PrimePack3 IGBTs used in an industrial motor drive. Straight, staggered pin and oblique fin structures are applied to the cooling channels of the cold plate with a parallel flow configuration. The numerical model of the cold plate is developed and analyzed using a CFD software. The effects of fin structures on liquid cooling performance are compared and discussed in detail. The thermal resistance values for the staggered pin and oblique fin structures exhibit reductions of 46.5% and 60.1%, respectively, compared to the straight fin configuration.

The durability of proton exchange membrane fuel cells (PEMFCs) under large load variation at rapid startup is critical for commercialization. Experimental and numerical results indicate that the five-channel serpentine flow field (FSFF) design exhibited the optimal large load variation capability at rapid startup and more effective performance degradation mitigation. Therefore, experimental investigations are conducted on the performance degradation and membrane electrode assembly deterioration of PEMFCs with parallel flow field (PFF) and FSFF designs under rapid dynamic loads (20,000 cycles, 2 s load transients to 3000mA cm-2). The results demonstrate that the multi-channel FSFF with better gas distribution uniformity and water removal capability significantly mitigates voltage degradation (9.11% vs 20.77% for PFF), reducing both cathode charge transfer resistance and electrochemical surface area degradation. Spatial degradation analysis reveals severe catalyst layer (CL) thinning in outlet regions for both configurations, but FSFF exhibits better degradation mitigation: cathode CL thickness reduction in the outlet region is lower than PFF, accompanied by reduced Pt particle size evolution and agglomeration. These findings highlight the critical role of flow field design in optimizing dynamic durability under large load variation at rapid startup.

Abstract Additive manufacturing has transformed thermal management by enabling the production of complex, optimized geometries that conventional manufacturing methods cannot achieve. This study investigates the single-phase convective heat transfer performance of gyroid triply periodic minimal surface (TPMS) lattice structures with functional porosity. TPMS structures provide high surface area to volume ratios and are amenable to 3D printing. A gyroid numerical model was created and validated against an existing experimental study with a similar feature size to the investigated geometries. The TPMS structure has a periodic width of 1.6 mm, a length of 10 mm, and a height of 4 mm, with a functional porosity ranging from 0.5 to 0.8, decreasing with distance from the heated surface. Three different flow configurations were examined for an inlet fluid temperature of 70 °C. The inlet velocities range from 0.01 to 1.2 m/s, corresponding to a Reynolds number range of 10–900 with a heat flux of 50 W/cm2 applied at the base. AmpCool® AC-110 dielectric fluid (Prandtl number 59.5) was used as the coolant. Thermal performance and friction characteristics were studied for the three flow orientations. The parallel flow configuration was identified as the most efficient for heat removal. A detailed analysis of the numerical results highlights the underlying physics behind the thermal performance differences among the flow configurations.

Predicting radionuclide behavior in deep geological repositories using graph convolutional long short-term memory.

This paper presents a semi-analytical method, referred to as the linear-velocity-profile fast field program (LFFP), for predicting two-dimensional sound fields in ambient parallel mean flows. The proposed method incorporates the linear velocity layering method into the fundamental framework of fast field program (FFP) to achieve reduced computational costs and enhanced precision, particularly under high-velocity gradient conditions. The accuracy of LFFP is validated through a two-dimensional jet case by comparison with the linearized Euler equation in frequency-domain. In shear flow cases, results obtained from various combinations of Mach number difference and shear layer thickness suggest that the reason for the higher precision of LFFP, compared to traditional FFP, primarily arises from its consideration of the second velocity gradient term in the Pridmore-Brown operator within each single layer. To systematically and mathematically explain this observation, residual analysis is introduced. Furthermore, based on the residual analysis, the multi-staircase layering model is subsequently developed to improve computational efficiency and adapt to sound field calculations in environments with multiple vertically variable ambient quantities.

Multi-objective optimization of parallel flow immersion cooling battery thermal management system with flow guide plates based on artificial neural network

Parallel flow cooling in hybrid PV/T systems: A computational investigation of air and water integration

The present study investigates passive microdroplet generation in a T-junction microchannel using microscopic observations, microscale particle image velocimetry (Micro-PIV) visualization, and lattice Boltzmann simulations. The key flow regimes, i.e., dripping, threading, and parallel flow, are characterized by analyzing the balance between hydrodynamic forces and surface tension, revealing the critical role of the flow rate ratio of the continuous to dispersed fluids in regime transitions. Micro-PIV visualizes velocity fields and vortex structures during droplet formation, while a lattice Boltzmann model with wetting boundary conditions captures interface deformation and flow dynamics, showing good agreement with experiments in the dripping and threading regimes but discrepancies in the parallel flow regime due to neglected surface roughness. The present experimental results highlight non-monotonic trends in the maximum head interface and breakup positions of the dispersed fluid under various flow rates, reflecting the competition between the squeezing and shearing forces of the continuous fluid and the hydrodynamic and surface tension forces of the dispersed fluid. Quantitative analysis shows that the droplet size increases with the flow rate of continuous fluid but decreases with the flow rate of dispersed fluid, while generation frequency rises monotonically with the flow rate of dispersed fluid. The dimensionless droplet length correlates with the flow rate ratio, enabling tunable control over droplet size and flow regimes. This work enhances understanding of T-junction microdroplet generation mechanisms, offering insights for applications in precision biology, material fabrication, and drug delivery.

LPG fuel supply systems are increasingly important for improving energy efficiency and reducing carbon emissions in the shipping industry. The primary objective of this research is to investigate the heat transfer phenomena to enhance the thermal performance of double-pipe heat exchangers (DPHEs) in LPG fuel supply systems. This study investigates the heat transfer performance of a glycol–steam double-pipe heat exchanger (DPHE) within an LPG fuel supply system under varying operating conditions. A computational model and methodology were developed and validated by comparing the numerical results with experimental data obtained from commissioning tests. Additionally, the effects of turbulence models and parametric variations were evaluated by analyzing the glycol–water mixing ratio and flow direction—both of which are critical operational parameters for DPHE systems. Numerical validation against the commissioning data showed a deviation of ±2% under parallel-flow conditions, confirming the reliability of the proposed model. With respect to the glycol–water mixing ratio and flow configuration, thermal conductance (UA) decreased by approximately 11% in parallel flow and 13% in counter flow for every 20% increase in glycol concentration. Furthermore, parallel flow exhibited approximately 0.6% higher outlet temperatures than counter flow, indicating superior heat transfer efficiency under parallel-flow conditions. Finally, the heat transfer behavior of the DPHE was further examined by considering the effects of geometric characteristics, pipe material, and fluid properties. This study offers significant contributions to the engineering design of double-pipe heat exchanger systems for LPG fuel supply applications.

This research examines the optimized integration of Bi₂Te₃-based thermoelectric generators (TEGs) in Ocean Thermal Energy Conversion (OTEC) systems, evaluating their performance via detailed numerical analysis. We conducted finite element simulations using COMSOL Multiphysics to analyze thermoelectric generators (TEGs) placed between a warm surface and cold deep seawater channels under different operational conditions. The research examined parallel and counter flow configurations at Reynolds numbers between 3987 and 73,800, with channel heights varying from 0.002 to 0.072 m. Results indicate that Reynolds numbers above 12,000 ensure stable heat supply to TEGs, resulting in a consistent output power of 3.01 W. The optimal net power of 1.45 W was attained at a channel height of 0.002 m, attributed to reduced pump power consumption. A comparative analysis of Bi₂Te₃-based material combinations demonstrated that improved electrical and decreased thermal conductivity notably enhanced system performance. This study offers essential insights for improving the design and implementation of TEG-OTEC systems, especially in offshore contexts where operational efficiency and system durability are critical, thereby contributing to the advancement of sustainable ocean energy technologies.

We investigate the interplay between ion temperature gradient (ITG) and parallel velocity gradient (PVG) instabilities in cylindrical geometry using a Water-bag model and 5D gyrokinetic simulations with a modified version of the GYSELA code. The Water-bag model provides an analytical dispersion relation, which is compared to linear gyrokinetic simulations. Strong agreement is found between predicted and simulated growth rates and real frequencies, validating GYSELA's applicability to cylindrical systems. The comparison also highlights key parametric dependencies on instability thresholds, including the effects of density profiles, temperature gradients, and velocity shear. Notably, weak temperature gradients are found to stabilize PVG modes, whereas strong temperature gradients tend to destabilize them. Additionally, parallel flow shear is shown to enhance ITG-PVG hybrid modes. These properties are likely to impact the turbulent regime.

This study focuses on the design and numerical simulation of a 1500 Gs industrial-grade superconducting cusp magnet applied to a 300 mm Czochralski (CZ) crystal growth process. A two-dimensional (2D) global - three-dimensional (3D) local model is established, along with large eddy simulation (LES) with a standard Smagorinsky turbulence model in melt flow to analyze the influence of zero Gauss plane (ZGP) positions on melt flow, heat transfer, and oxygen concentration distribution. The results indicate that adjusting the ZGP position significantly alters the melt flow structure, temperature distribution, and impurity transport mechanisms. A small temperature gradient is found in cases that ZGP is 100–150 mm below the free surface due to the flow parallel to heat transfer direction, which enhances heat transfer from crucible to crystal. The velocity and temperature oscillations beneath the crystallization region are significantly reduced as ZGP shifts away from freesurface. Furthermore, oxygen concentration distribution does not follow a direct correlation with ZGP height but is instead influenced by the melt flow pathways. At ZGP = −100 and −150 mm, a portion of the melt bypasses the free surface, limiting oxygen evaporation and leading to increased impurity retention. Notably, the cusp magnetic field (CMF) model in this work integrates actual superconducting coil designs with industrial parameters (geometry, material properties, and currents), bridging idealized models and industrial practice. This approach enables precise evaluation of magnetic field effects on crystal growth, guiding defect suppression and oxygen control in production. The physics-informed design framework enhances manufacturing predictability by aligning simulations with operational realities.