Search Results (820)

Microchannel liquid cooling technology, characterized by high heat-transfer efficiency, represents an effective solution for thermal management in high heat-flux density electronic devices. Existing research has mainly focused on optimizing the structural design of microchannel heat sinks, while neglecting the specific effects of inlet manifold configurations on their heat transfer and flow performance. To obtain more systematic data on microchannel heat transfer performance and internal velocity distribution, this study designed microchannels with single-inlet and triple-inlet configurations. A microchannel cooling performance testing platform was established, and visualization experiments of the internal flow field in straight microchannels were conducted using a particle image velocimetry (PIV) system. The velocity distribution uniformity and heat transfer performance were compared between single-inlet and triple-inlet microchannels with varying channel spacings. The results show that under the same flow conditions, the triple-inlet splitter structure yields a more uniform flow distribution, a lower peak temperature for the heat source chip, and improved heat transfer performance, with its pressure drop reduced to 11.1–26.6% of that of the single-inlet configuration. Furthermore, smaller channel spacings yield improved heat-transfer efficiency in microchannels. Full article

Introduction: Acute coronary syndrome (ACS), encompassing unstable angina, NSTEMI, and STEMI, is a major cause of morbidity and mortality worldwide. Novel inflammatory and nutritional biomarkers may provide incremental value for risk stratification beyond conventional predictors. This work sought to determine whether the Pan-Immune-Inflammatory Value (PIV) and the Hemoglobin-Albumin-Lymphocyte-Platelet (HALP) score could serve as independent prognostic indicators in individuals presenting with acute coronary syndrome. Methods: A retrospective multicenter study included ACS patients hospitalized between January 2020 and May 2024. Demographics, clinical data, and laboratory results were collected. PIV was calculated as follows: neutrophils × platelets × monocytes/lymphocytes. HALP score was calculated as follows: hemoglobin × albumin × lymphocytes/platelets. Correlations with clinical parameters and mortality prediction were analyzed. Results: A total of 1134 patients (mean age 62 ± 12 years) were included. PIV showed positive correlations with WBC (Rho = 0.574), troponin (Rho = 0.381), and CRP (Rho = 0.295), and negative correlations with HDL (Rho = –0.101) and ejection fraction (Rho = –0.316) (all p < 0.01). PIV independently predicted mortality with a cut-off ≥1074.2 (AUC = 0.619, sensitivity 45%, specificity 79.9%). HALP score negatively correlated with age, troponin, CRP, and ICU stay, and predicted mortality with a cut-off ≤3.58 (AUC = 0.722, sensitivity 53.8%, specificity 82%). Comparative ROC analysis showed that HALP demonstrated superior discriminative ability for mortality prediction compared with PIV. Conclusions: PIV and HALP score are independent prognostic markers in ACS, reflecting inflammatory burden and nutritional status. Their integration into clinical workflows may enhance risk stratification and support individualized management strategies. Given their simplicity and universal availability, PIV and HALP may serve as practical adjunctive tools to established risk scores, enabling early identification of high-risk ACS patients at the time of admission. Full article

Particle Image Velocimetry (PIV) often utilizes a cross-correlation method to determine how far particles have moved between two captured images. The most common methods for vector estimation use computationally exhaustive cross-correlation functions across the interrogation window and an exhaustive search to find the maximum correlation position. This paper proposes a novel method to vector generation in which a preprocessing blur is applied to the two image before performing a cross-correlation for only nine points. These nine points are used to approximate the original cross-correlation surface as a second-order polynomial surface that can be solved analytically to find the optima point. Three iterations of the process are used for each location converging to a precise optimum. This method is very accurate on computer-generated PIV images and solves the entire vector field faster than the original basic method at any image size. However, the success is limited to in silico PIV data and cannot produce coherent vector fields when applied to experimental data captured on a supra-aortic bypass PIV experiment. This method may find applications in other domains where the input data is closer to the perfect computer-generated particle data. Full article

We investigate the flow over a breached dam through combined measurements and numerical simulations, revealing key topological features of the mean flow, including separation and stagnation surfaces, attached vortices, secondary currents, and boundary layer development. PIV measurements of velocities are complemented with simulations with the interFoam solver of OpenFOAM-v2106 (URANS with k-ω SST closure model and rough-wall corrections). We show the development of the boundary layer over the crest, influenced by the breach crest wall curvature and strong lateral flow convergence. Three-dimensional separation is observed in the plunging pool. Two different attached vortices develop along the bottom and side walls of the breach, where underscouring is known to be strong. The first is associated with an adverse pressure gradient while the second results from the flow curvature imposed by the evolving geometry of the plunging pool. A counter rotating vortex pair is observed in the flow exiting the dam breach channel. We discuss the significance of these structures for hydraulic erosion and underscouring. We also provide recommendations for CFD modeling of dam breaches. Full article

Background: Predicting natural conception following surgical treatment remains a clinical challenge for endometriosis, a chronic inflammatory condition often associated with infertility. This study aimed to determine if simple, low-cost inflammatory biomarkers, such as NLR, dNLR, LMR, PLR, SIRI, PIV, and SII calculated from routine preoperative blood tests are associated with spontaneous pregnancy in women with endometriosis-related infertility after laparoscopic surgery. Methods: A retrospective analysis was conducted on 78 women between the ages of 18 and 48 who underwent standardized laparoscopic surgery and were monitored for up to 18 months. Results: The pregnancy group had significantly lower NLR, dNLR, PLR, SIRI, and especially SII values than the non-pregnancy group. Among the evaluated markers, SII, NLR, and dNLR demonstrated the highest discriminative ability for spontaneous conception. In regression analyses, lower values of NLR and dNLR were associated with higher odds of spontaneous pregnancy. Conclusions: These findings suggest a correlation between preoperative inflammatory status and postoperative reproductive outcomes in women with endometriosis. Full article

This study conducted laboratory model tests, integrated with Particle Image Velocimetry (PIV) technology, to investigate the evolution of the uplift bearing capacity of an under-reamed anchor group subjected to cyclic loading. The tests considered various working conditions, including different spacing ratios (S/D = 4, 5, 6, where S was the center-to-center spacing and D was the diameter of the under-reamed body), varying cyclic amplitude ratios (λ = 0.3, 0.5, 0.6, 0.7, 0.8) and different cycle times (M = 1, 5, 10, 30). PIV was utilized to observe the displacement field of the surrounding soil, revealing the group effect of the anchors and the variation in their uplift capacity under diverse cyclic amplitudes and cyclic times. The results indicated that the load–displacement curves could be delineated into three distinct stages: elastic, elastoplastic, and plastic. Notably, the group effect primarily initiated during the elastoplastic stage and developed significantly within the plastic stage. The cyclic amplitude ratio was identified as a key factor influencing the uplift capacity. Furthermore, compared to results from single pull-out tests, both the vertical displacement of the surrounding soil and the shear strength of the sidewall adjacent to the under-reamed body decreased following cyclic loading. Finally, the influence of the cyclic times depended on the occurrence of anchor failure; in the absence of failure, the anchor maintained satisfactory performance even after multiple cycles. Full article

This paper presents an experimental investigation of unsteady phenomena in shock wave/boundary-layer interaction on natural laminar flow airfoils at transonic speeds. Two airfoils of different relative thickness were studied over a Mach number range of M = 0.62–0.72 using high-speed schlieren visualization, unsteady pressure transducers, and Particle Image Velocimetry (PIV). Two distinct self-sustained periodical oscillation modes were identified. The first mode is a low-frequency oscillation analogous to classical turbulent buffet. The second modes are higher-frequency phenomena linked to oscillations of the laminar separation bubble. A key finding is a novel periodical oscillation regime, which accompanies the first/second mode, and represents laminar-turbulent transition point detaches from the normal shock wave, generating a new shock wave. The results show that the domiN/At mode and its characteristics depend strongly on the airfoil geometry, Mach number, and angle of attack, indicating a more complex transonic buffet behaviour in the presence of extensive laminar flow. Full article

Mixing processes in stirred tanks are widely applied across various industries, but still offer significant potential for optimization. A promising strategy is the use of double-stage impeller setups instead of conventional single impellers. While multi-impeller configurations are common in tall vessels, their benefits for standard tanks with a height-to-diameter ratio of 1 are largely unexplored. This study systematically investigates the flow fields of single, identical, and mixed double-stage configurations of a Rushton turbine, a pitched-blade turbine, and a retreat curve impeller. To ensure balanced power input in mixed configurations, a refined method for harmonizing specific power via impeller diameter adjustment is proposed. Stereo particle image velocimetry is applied to visualize flow fields, supported by refractive-index matching to enable measurements in a dished-bottom tank. The results reveal substantial flow deficiencies in single-impeller setups. In contrast, double-impeller setups generate novel and significantly improved velocity fields that offer clear advantages and demonstrate strong potential to enhance process efficiency across various mixing applications. These findings provide new experimental insights into the characteristics of dual impellers and form a valuable basis for the design and scale-up of stirred tanks, contributing to more efficient, reliable, and sustainable mixing processes. Full article

Mobile air cleaners have emerged as a practical solution for reducing indoor aerosol concentrations, particularly in the absence of HVAC systems. Their efficiency is typically assessed under standardised conditions, but how turbulence influences the effective air exchange rate indoors is not well understood. In this study, we present a systematic investigation of the impact of enhanced turbulence on aerosol decay in two room sizes (50 m³ and 200 m³) using a mobile air cleaner combined with different fan configurations. Particle counter measurements were conducted simultaneously with particle image velocimetry ($PIV$), enabling direct comparison of air exchange rates and flow field properties. Our results show that specific fan arrangements significantly modify turbulent kinetic energy ($TKE$) distributions and, in turn, alter the effective air exchange rate. In the smaller room, configurations generating higher $TKE$ brought the measured exchange rates closer to theoretical predictions, while in large rooms other arrangements led to noticeable deviations. We anticipate that these findings provide a reference framework for understanding the role of turbulence in indoor air cleaning performance, with implications for optimizing the operation and placement of mobile air cleaners in practical environments. Full article

This study investigates the aerodynamics of Romanian engineer Aurel Persu’s car through wind tunnel experiments involving force measurements, Particle Image Velocimetry (PIV), and CFD simulations. Tests using scale models revealed significant flow separation behind the cabin. The measured drag coefficient is C_D = 0.364 at 33 m/s, showing moderate sensitivity to Reynolds number. CFD simulations using the unsteady STAR CCM+ solver with a k-ω SST turbulence model produced a slightly lower drag coefficient (C_D = 0.353) due to delayed separation. The good agreement between experimental and numerical results validates the modeling approach and highlights aerodynamic limitations around the front and roof. Despite these limitations, the model achieved aerodynamic performance that was exceptional for its time and remained competitive with mainstream production vehicles well into the latter half of the 20th century. Full article

The COVID-19 pandemic and subsequent non-pharmaceutical interventions (NPIs) significantly disrupted the epidemiology of pediatric respiratory viruses. This study compared infection patterns among 3658 hospitalized children in South Korea during the pandemic (2020–2022) and the post-emergency phase (2023–2024), following the relaxation of mandatory NPIs. Of 4419 eligible tests, the most frequently detected viruses overall were rhinovirus/enterovirus (HRV/HEV) (27.9%), influenza (14.5%), and respiratory syncytial virus (RSV, 11.9%). The post-emergency phase was marked by a dramatic surge in influenza virus (IFV), which surged dramatically (5.5% → 28.2%), and a more than two-fold increase in adenovirus (ADV) (5.7% → 12.5%) (p < 0.001). (p < 0.001). Conversely, parainfluenza virus (PIV) detection rates declined significantly (15.4% → 11.3%, p < 0.001). Demographically, post-emergency phase patients were significantly older (mean 4.9 vs. 3.5 years) and experienced a shorter hospital stays (3.2 vs. 4.3 days) (p < 0.001). Crucially, age-specific susceptibility shifts were evident. IFV rebounded across all pediatric ages but spiked severely in school-aged children and adolescents, while HRV/HEV demonstrated a clear proportional shift towards older age groups. These results demonstrate a substantial reconfiguration of the pediatric respiratory landscape, necessitating age-stratified surveillance and flexible public health strategies to mitigate the future infectious disease burden. Full article

This study investigates the flow around Kline-Fogleman (KF) airfoils using Particle Image Velocimetry (PIV) in a wind tunnel at Reynolds number Re = 6.8 × 10⁴. Three configurations are tested: a clean NACA 0015 airfoil and two modified versions with a step on either the pressure or suction side. Velocity fields are used to calculate lift via the Kutta-Joukowski theorem. Results show that the KF airfoil with a step on the pressure side achieves a 14.8% higher maximum lift coefficient and delayed stall. In contrast, placing the step on the suction side reduces maximum lift by 4%. The KF airfoil with pressure-side step shows potential for low Reynolds number applications where higher lift and larger stall angles are required. Full article

Background/Objectives: Rosacea increasingly appears to involve systemic immune and metabolic disturbances rather than isolated cutaneous inflammation. To evaluate inflammatory, platelet, and oxidative–metabolic biomarkers in rosacea and explore their interrelations. Methods: 90 patients with rosacea and 90 healthy controls were evaluated for hematologic inflammatory indices—neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), systemic immune–inflammation index (SII), pan-immune–inflammation value (PIV), mean platelet volume (MPV), and C-reactive protein (CRP)—along with oxidative–metabolic regulators including sirtuin 1 (SIRT1), sirtuin 3 (SIRT3), visfatin, and irisin. Logistic regression and receiver operating characteristic (ROC) analyses were used to identify independent predictors of rosacea, while inter-marker associations were evaluated using Spearman’s rank correlation. Results: Rosacea patients showed higher NLR, PLR, SII, PIV, MPV, CRP, and LDL cholesterol (p < 0.05) and lower SIRT1, SIRT3, visfatin, and irisin (p < 0.01). MPV independently predicted rosacea (OR = 7.24; AUC = 0.827), whereas SIRT1 inversely correlated with disease risk. SIRT1, SIRT3, and visfatin showed inverse correlations with HbA1c and waist-to-height ratio, while fasting glucose and HOMA-IR remained within normal ranges. Conclusions: Rosacea exhibits dual systemic activation, an inflammatory–platelet and an oxidative–metabolic axis bridging immune dysregulation, mitochondrial stress, and vascular dysfunction. Recognition of these pathways highlights the potential of redox-targeted and metabolic interventions beyond symptomatic treatment. Full article

This paper investigates the rotational lift production of translating and rotating wings within a small insect’s Reynolds number range. Using the Reynolds number 1200 of a bumblebee, three wing section profiles were studied: a circular cylinder model as a reference for a blunt body for which the well-known Magnus effect will occur, a flat plate model as a reference for a sharp body for which the Kramer effect will occur, and finally, an elliptical cylinder model as a transition case. Direct force measurement and particle image velocimetry (PIV) experiments were performed to measure the lift produced and the surrounding flow velocity, and the Kutta–Joukowski theorem was applied to analyze the PIV results. The Kutta–Joukowski theorem gives the relationship between lift and circulation on a body moving at constant speed in a real fluid with some constant density. The experimental results were analyzed and verified by comparing them to the computational results. In general, there is reasonable agreement between the experimental and computational results, confirming that the Magnus effect is observed for the circular cylinder model and no Kramer effect is observed for the flat plate model. The elliptical cylinder model does not appear to be blunt enough for the Magnus effect to occur, and it is not sharp enough for the Kramer effect to occur. Full article

Understanding wake interactions between multiple tidal stream turbines is essential for optimizing the performance and layout of tidal energy farms. This study investigates the hydrodynamic behavior of two horizontal-axis tidal turbines arranged in tandem under simplified inflow conditions, where the incoming flow was dominated by the streamwise velocity component without imposed external disturbances. Wake measurements were conducted in a large circulating water tunnel using a mobile, submerged particle image velocimetry (PIV) system capable of long-range, high-resolution measurements. Performance tests showed that the downstream turbine experienced a decrease of approximately 9% in maximum power coefficient compared to the upstream turbine due to reduced inflow velocity and increased turbulence generated by the upstream wake. Phase-averaged PIV results revealed the detailed evolution of velocity deficit, turbulence intensity, turbulent kinetic energy, and tip vortex structures. The tip vortices shed from the upstream turbine persisted over a long downstream distance, remaining coherent up to 10D and merging with those generated by the downstream turbine. These merged vortex structures produced elevated turbulence and complex flow patterns that significantly influenced the downstream turbine’s operating conditions. The results provide experimentally validated insight into turbine-to-turbine wake interactions and highlight the need for high-fidelity wake data to support array optimization and numerical model development for tidal stream turbine array. Full article