bluuebunny/crossref_metadata_2025 huggingface dataset:
Maximum mouth opening in patients with cleft lip and palate or craniofacial anomalies compared with non‐affected controls: A cross‐sectional study
Authors: Campbell Richard , Trego Brigitte , Gosnell Elizabeth S. , Fenchel Matthew , Cully Jennifer L. , Wang Jue
Published: September 2024

Background

There are limited published data on maximum mouth opening (MMO) for children with cleft lip or palate (CLP) or craniofacial anomalies (CFA).

Aim

To report MMO of patients with CLP or CFA compared with non‐affected controls.

Design

Retrospective cross‐sectional review of electronic medical and dental records. Patients with CLP or CFA with recorded MMO, height, and weight were included and compared with a non‐affected control individuals seen during orthodontic screening. Outcome measures included MMO, recorded in millimeters of inter‐incisal distance, age, height, weight, and sex.

Results

Patients with CLP or CFA (n = 376) were matched by age and body mass standardized index (BMIz) to the non‐affected pool (n = 376). The affected group had a MMO of 43.14 mm (±7.1 mm) compared with the control group MMO of 48.01 mm (±7.6 mm) with a statistically significant difference of −4.86 mm (p < .0001). Specifically, MMO of the unilateral cleft group is 4.26 mm smaller than that of non‐affected controls (p < .0001). MMO of the bilateral cleft group is 3.65 mm smaller than that of non‐affected controls (p = 0.0063).

Conclusions

MMO for patients with CLP was significantly smaller as compared to non‐affected controls. This study helps establish MMO values for children with CLP and CFA.
Outcomes of partial pulpotomy in permanent molars of children with irreversible pulpitis: A prospective cohort study
Authors: Zheng Jiajia , Ding Meili , Zhang Shanshan , Ren Yulan , Wen Quan
Published: September 2024

Background

Vital pulp therapy is gaining traction in dental practice, especially for young patients.

Aim

To evaluate the outcomes of partial pulpotomy in permanent molars of children diagnosed with irreversible pulpitis (IP) using iRoot BP Plus.

Design

A total of 94 permanent molars in 88 patients, aged 6–15 years, with symptoms of IP, were treated with partial pulpotomy, using iRoot BP Plus as the pulp capping agent. The treated teeth underwent clinical and radiographic assessments at 1, 6, 12, 18, and 24 months postoperative. The outcomes were determined based on clinical and radiographic criteria by calibrated examiners.

Results

The success rates were 98.4% (63/64), 93.2% (41/44), and 89.7% (26/29) at the 6‐month, 12‐month, and 24‐month follow‐up. By the end of this study, the median follow‐up period was 15.1 months, and the estimated survival rate was 95.2% at 24 months. Gender, root maturity, and number of missing walls had no significant effect on success rates. Six molars were failed, and root canal therapy (RCT) was applied.

Conclusions

Partial pulpotomy for permanent molars with IP in young patients using iRoot BP Plus as pulp capping material achieved high success. This method presents a viable alternative to apexification and RCT for treating vital, inflamed molars with IP in children.
Early sleep apnea treatment in stroke (eSATIS) – a multicentre, randomised controlled, rater‐blinded, clinical trial: The association of post‐stroke cognition with sleep‐disordered breathing and its treatment
Authors: Filchenko Irina , Duss Simone B. , Salzmann Saskia , Brill Anne‐Kathrin , Korostovtseva Lyudmila , Amelina Valeria , Baillieul Sébastien , Bernasconi Corrado , Schmidt Markus H. , Bassetti Claudio L. A.
Published: September 2024

Sleep‐disordered breathing (SDB) is linked to cognitive dysfunction. Although SDB is common in stroke patients, the impact of SDB and its early treatment on cognitive functioning after stroke remains poorly investigated. Therefore, we explored the association between SDB and post‐stroke cognitive functioning, including the impact of early SDB treatment with adaptive servo‐ventilation (ASV) on cognitive recovery from acute event to 3 months post‐stroke. We used data from two studies, which included ischaemic stroke patients (n = 131) and no‐stroke controls (n = 37) without SDB (apnea–hypopnea index, AHI <5/h) and with SDB (AHI≥20/h). Cognitive functioning was assessed within 7 days and 3 months post‐stroke in stroke patients, or at study inclusion in no‐stroke control group, respectively. Stroke patients with SDB were randomized to ASV treatment (ASV+) or usual care (ASV‐). Linear regression adjusted for main confounders assessed the impact of SDB and its treatment on cognitive recovery. The intention‐to‐treat analysis did not show significant associations of SDB ASV+ (n = 30) versus SDB ASV‐ (n = 29) with cognitive recovery. In an exploratory subanalysis, compliant SDB ASV+ (n = 14) versus SDB ASV‐ showed improvements with ASV in visual memory and cognitive flexibility. Combining the stroke and non‐stroke datasets, SDB (n = 85) versus no‐SDB (n = 83) was associated with deficits in visual memory and response inhibition independently of stroke. SDB ASV‐ versus no‐SDB (n = 51) was associated with less improvement in visual memory. There was no substantial evidence for benefits of intention‐to‐treat ASV on cognitive recovery. Exploratory analysis indicated that compliant ASV treatment could benefit visual memory and cognitive flexibility, whereas untreated SDB could contribute to a poor recovery of visual memory.
REM sleep without atonia and neurocognitive function in isolated REM sleep behaviour disorder: Cross‐sectional and longitudinal study
Authors: Kang Sukhoon , Hong Jung Kyung , Kim Chan‐Hyung , Kim Ji Soo , Yoon In‐Young
Published: September 2024

This study investigated the relationship between rapid eye movement sleep without atonia and cognitive profiles in individuals diagnosed with isolated rapid eye movement sleep behaviour disorder, assesssing both cross‐sectional associations and their link to phenoconversion in a longitudinal follow‐up. Participants underwent video‐polysomnography, neurological examination, neuropsychological tests and structured interviews to confirm isolated rapid eye movement sleep behaviour disorder. Rapid eye movement sleep without atonia was manually scored using the Montreal method, and participants were categorized into either high or low electromyography activity groups, based on their tonic and phasic electromyography activities. The cross‐sectional study included 250 patients with isolated rapid eye movement sleep behaviour disorder, revealing that those with high tonic electromyography activity exhibited significantly lower scores in the constructional praxis recall than those with low tonic electromyography activity (p = 0.002). In the longitudinal study, 79 participants (63 isolated rapid eye movement sleep behaviour disorder and 16 phenoconversion), tracked for at least 5 years, demonstrated that high tonic electromyography activity (odds ratio: 6.14; 95% confidence interval: 1.23–30.60; p = 0.027) and lower performance on the Trail Making Test A (odds ratio: 0.23; 95% confidence interval: 0.11–0.70; p = 0.007) were associated with future phenoconversion. These results confirm the link between tonic electromyography activity and neurodegeneration in isolated rapid eye movement sleep behaviour disorder. Combining rapid eye movement sleep without atonia assessment with cognitive evaluation could serve as an early predictive marker for phenoconversion in clinical settings.
Native arbuscular mycorrhizal fungi drive ecophysiology through phenotypic integration and functional plasticity under the Sonoran desert conditions
Authors: Jiménez Alberto , Gutiérrez Aldo , Orozco Antonio , Vargas Georgina , Morales Idaly , Sánchez Esteban , Muñoz Ezequiel , Soto Francisco , Martínez‐Téllez Miguel Ángel , Esqueda Martín
Published: September 2024

Knowledge is scarce to what extent environmental drivers and native symbiotic fungi in soil induce abrupt (short‐term), systemic (multiple traits), or specific (a subset of traits) shifts in C3 plants' ecophysiological/mycorrhizal responses. We cultivated an emblematic native C3 species (Capsicum annuum var. glabriusculum, “Chiltepín”) to look at how the extreme heat of the Sonoran desert, sunlight regimes (low = 2, intermediate = 15, high = 46 mol m2 d−1) and density of native arbuscular mycorrhizal fungi in soil (low AMF = 1% v/v, high AMF = 100% v/v), drive shifts on mycorrhizal responses through multiple functional traits (106 traits). The warming thresholds were relentlessly harsh even under intensive shade (e.g. superheat maximum thresholds reached ranged between 47–63°C), and several pivotal traits were synergistically driven by AMF (e.g. photosynthetic capacity, biomass gain/allometry, and mycorrhizal colonization traits); whereas concurrently, sunlight regimes promoted most (76%) alterations in functional acclimation traits in the short‐term and opposite directions (e.g. survival, phenology, photosynthetic, carbon/nitrogen economy). Multidimensional reduction analysis suggests that the AMF promotes a synergistic impact on plants' phenotypic integration and functional plasticity in response to sunlight regimes; however, complex relationships among traits suggest that phenotypic variation determines the robustness degree of ecophysiological/mycorrhizal phenotypes between/within environments. Photosynthetic canopy surface expansion, Rubisco activity, photosynthetic nitrogen allocation, carbon gain, and differential colonization traits could be central to plants' overall ecophysiological/mycorrhizal fitness strengthening. In conclusion, we found evidence that a strong combined effect among environmental factors in which AMF are key effectors could drive important trade‐offs on plants' ecophysiological/mycorrhizal fitness in the short term.
On the modulus of continuity of solutions to nonlocal parabolic equations
Authors: Liao Naian
Published: September 2024

A general modulus of continuity is quantified for locally bounded, local, weak solutions to nonlocal parabolic equations, under a minimal tail condition. Hölder modulus of continuity is then deduced under a slightly stronger tail condition. These regularity estimates are demonstrated under the framework of nonlocal ‐Laplacian with measurable kernels.
Tools, techniques, methods, and processes for the detection and mitigation of fraudulent or erroneous data in evidence synthesis: a scoping review protocol
Authors: Barker Timothy Hugh , McBride Grace McKenzie , Ross-White Amanda , Pollock Danielle , Stern Cindy , Hasanoff Sabira , Kanukula Raju , Dias Mafalda , Scott Anna , Aromataris Edoardo , Whitehorn Ashley , Stone Jennifer , Shamseer Larissa , Palmieri Patrick , Klugar Miloslav , Munn Zachary
Published: September 2024

Objective:

This scoping review aims to identify, catalogue, and characterize previously reported tools, techniques, methods, and processes that have been recommended or used by evidence synthesizers to detect fraudulent or erroneous data and mitigate its impact.

Introduction:

Decision-making for policy and practice should always be underpinned by the best available evidence—typically peer-reviewed scientific literature. Evidence synthesis literature should be collated and organized using the appropriate evidence synthesis methodology, best exemplified by the role systematic reviews play in evidence-based health care. However, with the rise of “predatory journals,” fraudulent or erroneous data may be invading this literature, which may negatively affect evidence syntheses that use this data. This, in turn, may compromise decision-making processes.

Inclusion criteria:

This review will include peer-reviewed articles, commentaries, books, and editorials that describe at least 1 tool, technique, method, or process with the explicit purpose of identifying or mitigating the impact of fraudulent or erroneous data for any evidence synthesis, in any topic area. Manuals, handbooks, and guidance from major organizations, universities, and libraries will also be considered.

Methods:

This review will be conducted using the JBI methodology for scoping reviews and reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR). Databases and relevant organizational websites will be searched for eligible studies. Title and abstract, and subsequently full-text screening will be conducted in duplicate using Covidence. Data from identified full texts will be extracted using a pre-determined checklist, while the findings will be summarized descriptively and presented in tables.

This scoping review protocol was registered in Open Science Framework:

https://osf.io/u8yrn.
3D-CFD Analysis of Axial Thrust in an Unshrouded Impeller With a Balance Piston for Liquid Hydrogen Turbopumps
Authors: Sakai Kento , Kobayashi Yamato , Yoshida Shota , Kawasaki Satoshi , Miyagawa Kazuyoshi
Published: September 2024

Rocket pumps mainly use the Balance Piston (BP) system as an axial thrust self-balancing system for their large thrust. Although the BP system is statically stable, this system becomes unstable under some dynamic conditions. Therefore, some theoretical research has been previously conducted and identified its cause as fluid compressibility. However, their results used theoretical analysis, and very few examples examined the effect of fluid compressibility on three-dimensional unsteady fluid forces.

In this study, we performed a compressible CFD analysis in a liquid hydrogen turbopump with unshrouded impellers and compared the results with those of an incompressible analysis. Through the comparison, we investigated the influence of the fluid compressibility of liquid hydrogen on the pump’s axial characteristics.

According to the compressible CFD results, we found a significant decrease in fluid density in tip clearance due to the vortex from tip leakage flow occurring local temperature increase. In the BP system, because of the pressure loss and temperature rise associated with passage through the orifices, fluid density changed approximately 10% in the downstream of the BP chamber compared to the impeller inlet.

The unsteady-state calculation simulating forced axial vibration revealed that a lower damping coefficient, higher stiffness coefficient, and lower damping ratio were calculated in the compressible analysis than in the incompressible analysis. These findings were because No. 1 orifice loss of the BP system associated with forced vibration changed fluid density and static pressure in the compressible analysis, which resulted in changing the mass flow response into the BP system.
Design and Simulation of an SCO2 Opposing Piston Polygon Expansion Engine
Authors: Mitri Frederick B. , Anderson Kevin R.
Published: September 2024

The expansion engine described herein is designed to operate on a waste heat driven Rankine cycle utilizing super critical carbon dioxide (SCO2) as the working fluid. The end use for this system is as a means of recapturing waste heat generated in the power production process. In this capacity, the system will utilize leftover waste heat to generate more usable power, thereby increasing the efficiency of the power plant at which it is installed. The polygon engine opposed piston expander design was chosen due to its higher possible power output when compared to more typical layouts. The SCO2 power cycle was chosen due to the high efficiency of supercritical power cycles. The system presented herein was found to have a power to weight ratio of 1.979 HP/lbm with a maximum output power of 190 HP at about 1000 RPM and roughly 970 lbf-ft of torque. The optimum valve timing was found to consist of an intake opening angle of 2.5°, an intake closure angle of 110°, an exhaust opening angle of 170°, and an exhaust closure angle of 360°. The existing cycle states with inlet at 200 °C/20 MPa/258.82 kg/m3 and outlet at 163 °C/12.7 MPa/176.78 kg/m3 were found to be ideal. Furthermore, the existing piston design consisting of a 3-inch piston with a 2-inch stroke was also found to be acceptable.
Impact of Blade Design on Static Pressure Recovery of Rotor-Only Low-Pressure Axial Fans
Authors: Witte Hauke , Bode Christoph
Published: September 2024

In a broad range of applications, low-pressure axial fans are installed without outlet guide vanes and are discharging a swirling flow directly into a free environment. Considering the radial momentum balance, a static pressure recovery between a measurement plane immediately downstream of the fan trailing edge and a point in the free atmosphere far downstream of the fan can take place. When using the total-static efficiency computed with the ambient pressure as a metric, it is directly impacted by this pressure recovery in the fan discharge. In this paper, several fans with varying linear work distribution are designed and numerically investigated to quantify the impact of the pressure recovery on the total-static efficiency. Since in the discharge of such fans, free shear layers are the key aerodynamic feature for which standard RANS-eddy-viscosity simulations are known to be lacking accuracy, DDES simulations are performed. A non-zonal RANS/LES hybrid approach based upon the k-ω-SST eddy viscosity model and the γ transition model was used. The numerical investigation has shown that the pressure recovery has a significant impact on the total-static efficiency and can be influenced by the vortex design. Taking the pressure recovery into account, the optimal vortex design in terms of total-static efficiency shifts away from the low dynamic pressure vortex designs, which are usually aspired to minimize the exit loss.
Recovery of OxPure 612C-50 Coconut Carbon Particles Using Bump Arrays
Authors: Minette Michael J. , Burns Carolyn A. , Law Catrin A. , Addleman R. Shane , Bamberger Judith Ann , Serkowski Jason , Pease Leonard F.
Published: September 2024

Displacement arrays are useful for separating particles from carrier fluids such as blood cells and inorganics such as sand. The arrays of offset posts allow smaller particles to flow in the streamlines and cause larger particles to move around the posts migrating to one side. Migrating increases the particle concentration in one direction and depletes the particle concentration in the other direction. This allows particle separation to occur.

Experiments to separate large OxPure1 612C-50 coconut carbon particles in Newtonian slurries were conducted using bump arrays. The mesofluidic system uses an array of staggered posts as configured in a bump array for Newtonian slurry conditions. The results of these separation experiments are described. This information could be applied in gold recovery settings that use counter current cyanide processing.
Turbulence-Controlled Evolution of Particle Patterns on the Interface of Large Deformable Drops in Channel Flow
Authors: Marchioli Cristian , Hajisharifi Arash , Soldati Alfredo
Published: September 2024

The capture of small particles at the interface of large deformable drops and the subsequent evolution of particle surface distribution in turbulent flow are investigated. Direct numerical simulation of turbulence, phase field modeling of the drop interface dynamics and Lagrangian particle tracking are used. Realistic distribution of particles is ensured by excluded-volume interactions, i.e. by enforcing particle collisions. Particles are initially dispersed in the carrier flow and are driven in time towards the surface of the drops by jet-like turbulent fluid motions. Once captured by the interfacial forces, particles disperse on the surface. Excluded-volume interactions bring particles into long-term trapping regions of vanishing surface velocity divergence, where high-concentration particle clusters are formed. These regions correlate well with portions of the interface characterized by higher-than-mean curvature, indicating that modifications of the surface tension induced by the presence of tiny particles will be stronger in the highly-convex regions of the interface.
Rotor-Stator Interaction and Vortex Rope in the Reversible Pump-Turbine at Off-Design Conditions in Turbine Mode
Authors: Rode Bhushan R. , Kumar Arun
Published: September 2024

The reversible pump-turbine (RPT) operates at off-design operating conditions to balance the electricity grid due to the high penetration of variable and intermittent solar and wind energy. During these operating conditions, hydraulic instabilities such as rotor-stator interaction (RSI) and vortex rope in the draft tube give rise to pressure fluctuations in the vaneless space (VS) between the guide vanes and runner, and the draft tube, respectively. Therefore, the RPT may experience fatigue and vibration, further causing the vibration in the local components of the powerhouse. A reduced-scale high-head RPT model, and the SST k-ω turbulence model was used to carry out numerical calculations under the present study. The guide vane opening of 10°, 14°, 18.06° (best efficiency point), and 24° were performed and analyzed. The RSI phenomenon occurs in the VS due to the interaction of guide vane and runner. The vortex rope in the draft tube, due to the flow separation in the runner channels, was observed.
An Experimental Study of Pulsatile Flow and Structural Dynamics in a Thin-Walled Collapsible Vessel
Authors: Chowdhury Sifat K. , Zhang Yan
Published: September 2024

Many physiological fluid transport phenomena exemplify the complex fluid-structure interaction in collapsible tubes. For example, microgravity during space travel associates physiological challenges, as it alters hydrostatic and transmural pressures, causing irregular blood flow and venous thrombosis in veins. To further our understanding of the collapsible tube behavior under both steady and pulsatile flow conditions, an experimental study was presented in this paper. The study employed quantitative analysis of structural deformation and flow fields using image analysis and Particle Image Velocimetry (PIV) measurements. The results suggest that the tube wall deformation followed Shapiro’s tube law under static condition and conformed under steady flow condition. However, as Re increased above 1150, self-excited oscillations occurred in an irregular pattern within specific ranges of negative transmural pressures. These oscillations became stronger and more regular as Re further increases, with frequency increasing as transmural pressure became more negative. With pulsatile flow inputs, negative transmural pressures also led to periodic self-excited oscillations during each cycles, particularly towards the end of systolic phases. Flow limitation effects were observed, with self-excited oscillations enhancing peak flow rates under strongly negative transmural pressures. The study suggests that self-excited oscillations could be triggered by either steady flow and pulsatile flow inputs within optimal transmural pressure ranges. In pulsatile flows, a negative transmural pressure aids in maintaining positive pressure gradients, acting similarly to valves to prevent flow reversal.
Evaluation of Computational Fluid Dynamics Modeling for Erosion in Elbow With a Large-Scale Erosion Database
Authors: Zhang Jun , Li Jamie (Yijie) , Karimi Soroor , Shirazi Siamack
Published: September 2024

Computational Fluid Dynamics has been widely used in various engineering applications. Solid particle erosion of material is a multi-physics problem that requires a great deal of expertise to simulate and predict. Evaluation of the CFD models available is critical to formulate the correct CFD settings to perform the task of adequately and accurately predicting erosion and uncertainties from the CFD models. Collecting high quality erosion data is also very challenging, which has been the objective of Erosion/Corrosion Research Center at The University of Tulsa over the past decades. Continuous efforts have resulted in a large number of reliable data collected which can be used for validating different CFD models. The data is collected with high accuracy fixed mounted and temperature compensated ultrasonic transducers that will not interfere with flow and particle regimes inside the elbow. Air and water is used as the carrier fluids. The sand concentration is monitored to guarantee consistent diluted particle-laden flow condition. Experiments are repeated for validity.

With data available, CFD models are established to predict erosion for all the collected cases which is the first trial ever to evaluate the robustness of applying CFD to predict erosion under various flow and particle conditions. The significance of the work underlies that obtaining an overall impression of how accuracy is CFD modeling for predicting erosion and a calibrated CFD framework for CFD-based erosion prediction can be derived from numerous practices in the process. The study uses RANS models for turbulence modeling and one-way particle tracking under engineering application context. The effect of global mesh size is examined to reach the best practice for representing erosion results. All the results from CFD are compared to data and have shown that CFD models with delicate calibration can predict erosion accurately, which provides a valuable tool for engineering design and prediction under complex conditions.
Investigations of a Half-Stepped Cylinder in a Turbulent Boundary Layer
Authors: Moffit Ryan , Rahai Hamid
Published: September 2024

Experimental investigations of a single half-stepped cylinder and a half-stepped cylinder sheet placed on a flat plate inside a turbulent boundary layer at zero pressure gradient have been performed. The goal of the study was to investigate whether a half-stepped cylinder could be used to control the low-speed streaks similar to riblets in reducing turbulent shear stress. The half-cylinder diameter (d) was 2 mm and the step-spacing (s) was 1.5 mm. The width (w) of the cylinder between the steps was 2 mm. The structure of the bump and valley repeated itself the entire length of the cylinder. The single cylinder row or sheet was placed in the spanwise direction where the bump round leading edge was facing the incoming axial flow. The flat plate had 7 rows of staggered round pegs at the leading edge to ensure a fully developed turbulent boundary layer at the cylinder’s location. The experiments were performed at 10 m/sec. in the closed-circuit CSULB-Boing low-speed wind tunnel. The ratio of the cylinder’s radius to the local boundary layer thickness (r/δ0) was 4% and the Reynolds number based on flat plate length was 5.8 × 105. An estimate of the skin friction coefficient was made using the Clauser chart and turbulence measurements were made using a hot wire anemometer. Results showed that, with the stepped cylinder in place, the local skin friction coefficient drops downstream of the half-stepped cylinder with the maximum drops exceeding 12% and 35% respectively for the single row and cylinder sheet at x/d = 13 and then gradually recovers to the corresponding value for an unperturbed flat plate at x/d = 26. At x/d = 13 and further downstream the spanwise variations of the boundary layer parameters behind the stepped cylinder were insignificant. Above the stepped cylinder, the turbulence intensity is reduced, however, in the near wake downstream, there is an increase in axial turbulence intensity attributed to the wake of the cylinder.
Digitalization of Test-Rigs for Model Acceptance Testing of Hydraulic Machines: Gaussian-Process Based Digital-Twin of a Turbine on a Hydraulic Test-Rig for Later Efficiency-Analysis and Test-Automation
Authors: Stolz Michael C. , Reiterer Stefan H. , Reiterer Daniel R. , Schaffernak Gerhard , Guggenberger Mark
Published: September 2024

Systematic measuring of hydraulic machine’s performance data at hydraulic model test-rigs involves comprehensive expert knowledge of the test-rig-engineer and is time consuming, as the multi-dimensional operation space must be explored manually. Expertise is needed for taking into account specific performance limits of test-rig equipment, model turbine, storage pumps or pump-turbines as well as some hysteresis of the setup due to flow separation and dealing with quite operation point dependent gains between controlled parameters and measured quantities. In order to free valuable manpower from the burden of shiftwork, the measurement procedure is subject to automation. But testing new automation concepts involves safety critical or expensive tests and consumes valuable time at test-rig too.

To develop and validate new automation concepts offline, we present a hybrid data-driven modelling approach to create a digital twin of the combined setup of a hydraulic turbine on a hydraulic test-rig. Special attention is paid that the modelling approach is consistent with existing mathematical relations governed by either physical models or norms. The presented approach allows separation of test-rig and hydraulic model machine under test and by this enables offline-validation of automation concepts on different combinations of test-rigs and hydraulic model machines. The modelling approach is demonstrated performing cross-validation using recorded measurement data.
Numerical Investigation of a Vertical-Axis Wind Turbine Using a Three-Dimensional Panel Method
Authors: Nicola Yannick , Thümmler René , Kassera Volker , Böhle Martin
Published: September 2024

Vertical-axis wind turbines (VAWTs) have their rotor blades oriented vertically around a central axis of rotation. Unlike horizontal axis wind turbines (HAWTs), they do not require a mechanism to orient their blades into the wind, enabling them to capture wind from any direction. The absence of this directional adjustments makes VAWTs easier to install and to maintain. Furthermore, VAWTs can operate at a lower rotational speed, resulting in reduced noise emissions. This is one advantage making them more suitable for urban environments. The present paper discusses the procedure for calculating the aerodynamic loads on VAWTs using a three-dimensional panel method. Panel methods are based on potential theory and consider incompressible, non-viscous, irrotational flows. However, they do not account for flow separation effects but due to their fast computation time, they are primarily used for the initial aerodynamic design, such as the design of wind turbines. The paper first introduces the theoretical foundations of the numerical panel method, followed by an explanation of its application to vertical-axis wind turbines. By incorporating a rigid body motion, the rotation of the blades can be considered. Furthermore, to accurately reproduce the aerodynamics on the blades, a wake roll-up algorithm for the wingtips is utilized. The study focuses on a three-bladed vertical-axis wind turbine with NACA 0021 airfoils. For comparative purposes, transient numerical 2D simulations based on Computational Fluid Dynamics (CFD) were performed, using the OpenFOAM software. For the CFD simulations, the two-equation k-ϵ turbulence model was used. In order to minimize the effects of the VAWTs start-up process, multiple revolutions were examined in the simulations. The results obtained from the panel method and the CFD are compared, considering variations in forces and the rotor torque over the last revolution. The paper concludes by assessing the agreement between the results obtained from both methods and suggests how the panel method can be further developed with regard to accuracy and efficiency.
Sparse Reduced-Order Modeling of a Hovering Hawkmoth’s Wake
Authors: Lionetti Seth , Hedrick Tyson L. , Li Chengyu
Published: September 2024

As insects fly, their wings generate complex wake structures that play a crucial role in their aerodynamic force production. This study focuses on utilizing reduced order modeling techniques to gain valuable insights into the fluid dynamic principles underlying insect flight. Specifically, we used an immersed-boundary-method-based computational fluid dynamics (CFD) solver to simulate a hovering hawkmoth’s wake, and then identified the most energetic modes of the wake using proper orthogonal decomposition (POD). Furthermore, we employed a sparse identification of nonlinear dynamics (SINDy) approach to find a simple reduced order model that relates the most energetic POD modes. Through this process, we formulated multiple different models incorporating varying numbers of POD modes. To compare the accuracy of these models, we utilized a force survey method to estimate the aerodynamic forces produced by the hawkmoth’s wings. This force survey method uses an impulse-based approach to calculate the aerodynamic lift and drag based solely on the velocity and vorticity information provided by the model. By comparing the estimated aerodynamic force with the actual force production calculated by the CFD solver, we were able to find the simplest model that still provides an accurate representation of the complex wake produced by the hovering hawkmoth wings. We also evaluated the stability and accuracy of this model as the number of flapping cycles increases with time. The reduced order modeling of insect flight has important implications for the design and control of bio-inspired micro-aerial vehicles. In addition, it holds the potential to reduce the computational cost associated with high-fidelity CFD simulations of complex flows.
Optimizing Ventilation Strategy for Enhanced Airborne Disease Control in the Intensive Care Unit
Authors: Amininan Koorosh , Salmanzadeh Mazyar , Ahmadi Goodarz
Published: September 2024

Humans have been struggling with various infectious diseases that can spread through the air. Plague, SARS, smallpox, and influenza epidemics are a few examples of serious concerns. At the end of 2019, a new acute respiratory disease caused by the SARS-CoV-2 virus started the COVID-19 global pandemic. Recent studies have emphasized the importance of breathing and talking in the spread of airborne diseases. In this study, the chance of cross-infection in an Intensive Care Unit (ICU) in a hospital was studied numerically under different air distribution system strategies. We assumed 1 μm droplets, which carry viruses, were released from the patient’s mouth during speaking and breathing. The simulated environment was a segment of a hospital’s intensive care unit (ICU) with two nurses and two patients. Eulerian and Lagrangian approaches were used to simulate droplet movement using ANSYS-FLUENT software. The study examined two ventilation strategies, all operating at a similar ventilation rate of 12 ACH but distinguished by different inlet and outlet configurations. The purpose of the study was to understand the distribution of particles in this environment at 300-second intervals. Validation of the computational model included a comparative analysis of simulated velocity flows over a single heated humanoid manikin’s head with the experimental data. The results showed that having a downward vertical inlet airflow and air exhaust register at the top of the patient bed has the most effective droplet removal strategy.
Bubble Dynamics in Accelerating Flow Through Axisymmetric Nozzle
Authors: Shepard Thomas , Law Deify , Cunningham Connor , Churchill Will , Selvamani Arun Sriniwas , Robles Emmanuel Fernandez
Published: September 2024

A gas bubble traveling in a liquid flow through a convergent nozzle will experience a rapidly decreasing pressure on the leading edge of the bubble. Thus, the bubble will dynamically deform while passing through the nozzle showing an elongation of the front of the bubble. This work reports on experimental studies with high-speed imaging in a refractive index matched axisymmetric nozzle and complementary volume of fluid numerical simulations conducted via ANSYS Fluent. In these studies, an individual bubble is tracked as it flows downward approaching and then passing through the nozzle. A digital image processing algorithm is used to obtain quantitative information about the bubbles from high-speed images. Experimental results are provided that detail the bubble leading and trailing edge trajectory and bubble deformation. Under certain conditions the bubble deformation can lead to the bubble pinching apart near the leading edge, a phenomenon that was found in both the experiments and simulations. Simulation results are compared with experimental data and additionally provide information on the time-varying exit void fraction and exit velocity as the bubble accelerates through the contraction. This study examines two different bubble diameters and two different liquid flow rates to identify their role in the deforming bubble dynamics.
A Comparison Between a New Blade Design Model for Side Channel Pumps and Standard Side Channel Pump Blade Design in Terms of Performance and Flow Topology
Authors: Fleder Annika , Hassert Frank , Böhle Martin
Published: September 2024

Side channel pumps are low specific speed pumps with high head and low flows. The ability to process high amounts of gas in the fluid as well as the self-priming makes them a perfect match for oil and gas applications. In recent years, more attention is paid to side channel pumps especially due to their benefits in LNG (liquid natural gas) applications, e.g. as fuel pump to fulfill the increasing emission limits of cargo vessels by dual fuel or LNG propulsion.

To increase the performance of side channel pumps by increasing head and efficiency, the blade shape is investigated more in detail. Common side channel pump impeller blades have a triangular or straight cross section.

Based on earlier investigations on the flow phenomena in side channel pumps we are able to adapt the shape of the blades to the flow angle inside the pump, resulting in a new impeller blade design with a curved cross section.

As the flow angle differs from inner to outer diameter and from pressure to suction side of the blade, the blade shape was optimized to maintain the flow rate of the best efficiency point.

The new design is investigated in numerical simulation with ANSYS CFX and measurements on a water test rig at the manufacturer. A comparison with former measurements and simulations of traditional designs highlights the benefits of the new design by describing the internal flow.
Experimental and Numerical Investigations of Deformation in the Impeller of a Boiler Feed Pump at Design and Off-Design Conditions
Authors: Baum Andreas , Schneider Andreas , Knapp Axel , Grunenberg Matthias , Böhle Martin
Published: September 2024

Pump impellers have to be designed from two separate points of view. From a hydraulic aspect the impeller has to fulfill the specified operating conditions for flow rate, head at the speed of rotation. Additionally, from the structural point of view, the impeller must be capable to resist mechanical loads. To fulfill nowadays requirements of flexible operating conditions, the mechanical design becomes more crucial, because of increased loads at part-load operation. Consequently, trustworthy information about deformation and stress are mandatory.

The present paper deals with the comparison of mechanical deformation of a pump impeller at design and off-design operation. The full loading on the impeller caused by fluid pressure and centrifugal forces is considered in experimental and numerical investigations. Therefore, an experimental model pump, representing a repeating stage of a multistage boiler feed pump has been developed. Besides performance values, transient pressure and strain measurements at the back side of the impeller rear shroud are evaluated. For the strain measurements, strain gauges are used in Wheatstone bridges to evaluate transient data. For numerical simulations a one-way coupled Fluid Structure Interaction (FSI) model has been used. Transient Computational Fluid Dynamics (CFD) simulations have been performed for the complete model pump. For the turbulence modeling Menter’s SST model was used. In subsequent quasi-stationary Finite Elements (FE) simulations, the pressure loading on the impeller is taken from the CFD simulations for one impeller revolution.
Evaluating the Role of Ejector Nozzle Angle Deviation on the Performance of an Industrial Stack Ejector System
Authors: Ghateii Mohammad Hosein , Darbandi Masoud , Jalali Ramin , Schneider Gerry E.
Published: September 2024

Stack ejectors are considered as an essential component in numerous industries, serving as a pivotal mechanism for efficiently eliminating flue gas by inducing a draft. This research delves into the intricacies of stack ejector design and performance, emphasizing evaluating the consequences of deviations in ejector nozzle angles on flue gas flow. Within the stack ejector system, an air fan propels air into the stack to encourage flue gas to exit. The correct design and alignment of the ejector nozzle are paramount in maximizing flue gas flow. The computational fluid dynamics (CFD) simulations were carried out to gauge the impact of deviations in the ejector nozzle angle on flue gas flow. The results revealed that the deviations of 2, 4, and 6 degrees in the ejector nozzle angle would reduce the flue gas flow by 25%, 50%, and 60%, respectively. These findings underscore the substantial influence of ejector nozzle variations on flue gas flow within the stack ejector system. By comprehending the ramifications of nozzle angle deviation, engineers can enhance the design and alignment of stack ejectors to elevate their performances and overall efficiencies within their industrial setups.
Application of POD and DMD to Study Flow in Porous Media
Authors: Basnet Piyush , Durgesh Vibhav
Published: September 2024

Fluid flows in porous media exhibit diverse spatially and temporally complex structures arising from intricate interactions between fluid motion and solid interfaces/flow paths. While numerous experimental studies have aimed to quantify these complex flow structures, recent technological advancements have facilitated the widespread adoption of data-driven analysis approaches. These approaches offer invaluable insights into flow physics and can also be used for low-order modeling. The two primary objectives of this study are to apply Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) to velocity flow field data to predict the flow phenomena, develop low-order models, and apply DMD onflow visualization Planar Laser-Induced Fluorescence (PLIF) data to identify the temporal evolution of flow structures for recirculation region in porous media. An in-house refractive index-matched flow loop system was designed for the experiments, where a gear pump was used for fluid circulation, and a syringe pump was used for dye injection. The Reynolds numbers (Re) and the average porosity for the experiment were 42 and 0.39. Irregularly shaped 3 mm Tetrafluoroethylene hexafluoropropylene vinylidene fluoride (THV) beads were used as the porous media. 2D-PIV measurements were made at the center plane of the models to obtain a velocity flow field, which revealed a recirculation region. Applying POD in the PIV dataset, the energy distribution in the first twenty-five POD modes revealed key insights at Re. First twenty-five POD modes captured 74% of the recirculation region’s total energy. DMD provided dynamic insights into the velocity flow field, including frequency and growth rate associated with the frequencies in the recirculation region. Dominant frequencies were obtained using DMD, which were related to the occurrence of vortex in velocity flow field data. Low-order models were created using twenty-five POD modes and three DMD with modes with mean flow mode. The reconstructed velocity flow field data was compared with PIV velocity flow field data, resulting in an average Root Mean Square Error (RMSE) of 0.06% for POD across all regions and 1.37% for DMD low-order models for the recirculation region. Additionally, PLIF measurements using Rhodamine-B dye were used for flow visualization in the recirculation region. PLIF data offered qualitative information complementary to PIV. DMD results from flow visualization provided information about the flow dynamics of dye at Re = 42 in the recirculation region. The frequencies associated with the growth rate closer to zero in the frequency trend could capture the diffusion of dye, and the remaining frequencies captured the advection of dye. In conclusion, this study highlights the applicability of POD and DMD in unraveling the intricate dynamics of fluid flow in porous media, paving the way for future advancements in understanding and modeling these complex systems.
Expansion Ratio and the Heat Transfer Characteristics of Suddenly Expanding Viscoplastic Flows
Authors: Hammad Khaled J.
Published: September 2024

The impact of the expansion ratio on heat transfer from Bingham viscoplastic non-Newtonian flows through axisymmetric sudden expansions has been studied numerically by solving the mass, momentum, and energy conservation equations. Two expansion ratios 1:5 and 1:2 have been investigated. The expansion ratio has a dramatic impact on the reattachment length, in the case of Newtonian flows, and the recirculation intensity, in the case of Newtonian and viscoplastic non-Newtonian flows. In general, a more intense recirculation is associated with higher expansion ratios. The non-dimensional yield stress, i.e., yield number, is found to have a significant impact on the flow and heat transfer behavior. The relative recirculation intensity substantially diminishes with the yield number for both expansion ratios. For a given Reynolds number, increasing the yield number, results in transitioning from a recirculating to a non-recirculating viscoplastic flow regime downstream of the expansion plane. Substantial heat transfer enhancement exists downstream the expansion. A single wall heat transfer peak is observed for Newtonian and non-separating viscoplastic flows, immediately downstream of the reattachment point and corner unyielded region, respectively. However, two local peaks are observed in the case of recirculating viscoplastic flow fields. The first is close to the center of the weak corner vortex and the second is downstream of the stagnant impingement region. Peak heat transfer rates were found to substantially increase with the yield number, Prandtl number, and, to a lesser extent, with the expansion ratio.
Validating the Nonlinear Slip Boundary Conditions for Water TIP3P Using Molecular Dynamics Simulations
Authors: Islam Hafizul , Thalakkottor Joseph John
Published: September 2024

Studying the movement of fluid requires some assumptions about how fluid flows (the boundary condition) at the solid-fluid interface. The boundary condition, commonly known as the no-slip condition, states that fluid elements adjacent to a surface assume its velocity. Despite its remarkable success in replicating the characteristics of many flow types, this condition can produce unusual or singular behavior when applied to the spreading of a fluid on a solid substrate, corner flow, and forcing molten polymers out of a narrow tube. Maxwell and Navier’s slip model resolved these difficulties by allowing finite slip at liquid-solid interfaces. However, these phenomenological models cannot provide a universal perception of momentum transfer at liquid-solid interfaces. Thompson and Troian showed that for high shear rates, the slip is no longer a constant rather, it is a function of the shear rate. This was further extended by Thalakkottor and Mohseni, who showed slip length is more generally a function of the principal strain rate. Both these models were validated using molecular dynamics simulations of a monoatomic liquid similar to liquid Argon, which is rarely encountered in real-world applications. In this study, we simulate water instead, using the TIP3P model. Three different liquid-solid interfaces with varying degrees of hydrophobicity are studied. The study demonstrates that the nonlinear slip model, especially Thompson and Troian’s slip model, is valid for water flows as well.