bluuebunny/crossref_metadata_2025 huggingface dataset:
Contourite on the Limpopo Corridor, Mozambique margin: Long‐term evolution, facies distribution and Plio‐Quaternary processes
Authors: Babonneau Nathalie , Raisson François , Genêt Adrien , Lopes Ugo , Fierens Ruth , Miramontes Elda , Révillon Sidonie , Rabineau Marina , Droz Laurence , Belleney Deborah , Moulin Maryline , Aslanian Daniel
Published: September 2022

Bottom currents are key processes that contribute to the shaping of submarine slopes, with the redistribution of sediments in contourite systems. Despite numerous recent studies on contourite systems, the complexity and diversity of these sedimentary systems are still not fully understood and often underestimated. Their understanding requires comprehensive works integrating all scales from seismic architecture to microfacies. This paper focuses on a contouritic ridge located between 2000 m and 2500 m water depth on the Mozambique margin. Bathymetry, seismic data and piston cores collected during the PAMELA‐MOZ3 cruise allow a multi‐scale study from large depositional geometries to sedimentary facies. At the seismic scale, the contouritic ridge shows three stages of evolution with: (i) initiation and development of the drift/moat system; (ii) an intermediate stage with successive incisions and aggradations; and (iii) moat infill and drift erosion during the Plio‐Quaternary. Plio‐Quaternary deposits are composed of hemipelagic, turbiditic and contouritic facies filling the moat. Coarse‐grained contouritic facies, dominated by planktonic foraminifera, are identified on the western flank of the ridge between the moat infill and the erosional area at the top of the ridge. They consist of condensed deposits, with sedimentation rate about 0.3 cm/ka, indicating a strong and stable bottom current that winnows away the fine‐grained component. This facies could be present more generally in an intermediate position between erosion and depositional areas in contourite systems. At present, the contourite system is located at the transition depth between North Atlantic Deep Water and Antarctic Intermediate Water. Trajectories of bottom currents are complex and interact with sporadic turbidity currents and anti‐clockwise eddies that participate in reshaping the sea floor morphology. Although Plio‐Quaternary depositional geometries indicate the end of drift/moat development, the moat filling and drift erosion are also related to bottom currents and constitute atypical contouritic sedimentation.
Characterization of the novel HLA‐B*35:547 allele detected in a potential hematopoietic stem cell donor
Authors: Ananeva Anastasiia , Nizamov Shamil , Shagimardanova Elena
Published: September 2022

The novel HLA‐B*35:547 allele was characterized using next generation sequencing technology.
The detection of four novel HLA‐A alleles: HLA‐A*31:01:48, ‐A*31:210, ‐A*31:211 and ‐A*33:03:54
Authors: Ananeva Anastasiia , Gulnaz Akhmetshina , Sergeeva Iuliia , Shagimardanova Elena
Published: September 2022

Four novel HLA‐A alleles HLA‐A*31:01:48, ‐A*31:210, ‐A*31:211 and ‐A*33:03:54 alleles detected during routine next generation sequencing.
Assessment of polymicrobial interactions in bacterial isolates from transfused platelet units associated with sepsis
Authors: Kerantzas Christopher A. , Merwede Jacob , Snyder Edward L. , Hendrickson Jeanne E. , Tormey Christopher A. , Kazmierczak Barbara I. , Peaper David R.
Published: September 2022

Background

In 2019 the Centers for Disease Control and Prevention (CDC) reported a series of 4 transfusion reactions that resulted from contamination of apheresis platelet products. Products involved in all 4 cases were contaminated with Acinetobacter calcoaceticus‐baumannii complex (ACBC) and in 3 products Staphylococcus saprophyticus was found as well. CDC investigation found that bacterial isolates from the cases were genetically related and suggested a common source of contamination. The contamination of blood products with ACBC is rare and polymicrobial contamination of blood products even less common. ACBC and S. saprophyticus have been observed to adhere to one another and sediment out of suspension in vitro, a process referred to as coaggregation, and we hypothesized that there was an interaction between the strains from these cases that contributed to their co‐contamination of blood products.

Study design and methods

To test the hypothesis of bacterial interaction, we performed coaggregation experiments and observed the growth characteristics of ACBC and S. saprophyticus strains recovered from contaminated blood products involved in a subset of the CDC cases.

Results

An increase in S. saprophyticus CFU concentration was observed after several days of co‐culture with ACBC in LB and plasma; however, no other findings suggested coaggregation or augmentative growth interaction between the bacterial strains.

Conclusion

Ultimately, an interaction between ACBC and S. saprophyticus that could help explain their co‐occurrence and growth in contaminated platelet units was not found; however future studies of potential interactions may be warranted.
Surgical complications following sentinel lymph node biopsy guided by γ‐probe and methylene blue in 113 tumour‐bearing dogs
Authors: Chiti Lavinia Elena , Gariboldi Elisa Maria , Ferrari Roberta , Luconi Ester , Boracchi Patrizia , De Zani Donatella , Zani Davide , Manfredi Martina , Spediacci Carlotta , Grieco Valeria , Giudice Chiara , Recordati Camilla , Ferrari Francesco , Stefanello Damiano
Published: September 2022

Sentinel lymph node biopsy (SLNB) is an accepted veterinary surgical procedure given the impact of early detection of nodal metastases on staging of several canine malignancies. This study aims at reporting the incidence and risk factors for surgical complications of SLNB in tumour‐bearing dogs. A total of 113 client‐owned dogs that underwent tumour excision and SLNB guided by γ‐probing and blue dye were retrospectively enrolled. Recorded variables included: signalment, location and number of extirpated lymphocenters and nodes, time for SLNB, histopathological status of excised nodes. Incidence of SLNB complications was calculated. They were classified as minor and major based on severity and required treatment, and as short‐term (0–30 days) and long‐term (31–90 days). Univariate analysis with generalized linear model with binomial error estimated the association between variables and incidence of SLNB complications. Significance was set at 5%. Median overall time for SLNB was 25 min. Surgeons excised one node in 38% of dogs and multiple nodes in 62% of cases, belonging to one (62%) or multiple (38%) lymphocenters. Metastases were detected in 45% of nodes. No intraoperative complications occurred. The overall incidence of postoperative complications of SLNB was 21,24%, the majority of which (91.67%) were minor. Only increasing dogs' weight was associated with an increased incidence of SLNB complications (p = .00976). Sentinel lymphadenectomy was associated with a relatively low incidence of complications, most of which were self‐limiting. The low morbidity and previously reported impact on staging of SLNB justify its implementation to collect data for prognostic studies.
Motoneuron excitability dysfunction in ALS: Pseudo‐mystery or authentic conundrum?
Authors: Elbasiouny Sherif M.
Published: September 2022

In amyotrophic lateral sclerosis (ALS), abnormalities in motoneuronal excitability are seen in early pathogenesis and throughout disease progression. Fully understanding motoneuron excitability dysfunction may lead to more effective treatments. Yet decades of research have not produced consensus on the nature, role or underlying mechanisms of motoneuron excitability dysfunction in ALS. For example, contrary to Ca excitotoxicity theory, predictions of motoneuronal hyper‐excitability, normal and hypo‐excitability have also been seen at various disease stages and in multiple ALS lines. Accordingly, motoneuron excitability dysfunction in ALS is a disputed topic in the field. Specifically, the form (hyper, hypo or unchanged) and what role excitability dysfunction plays in the disease (pathogenic or downstream of other pathologies; neuroprotective or detrimental) are currently unclear. Although several motoneuron properties that determine cellular excitability change in the disease, some of these changes are pro‐excitable, whereas others are anti‐excitable, making dynamic fluctuations in overall ‘net’ excitability highly probable. Because various studies assess excitability via differing methods and at differing disease stages, the conflicting reports in the literature are not surprising. Hence, the overarching process of excitability degradation and motoneuron degeneration is not fully understood. Consequently, the discrepancies on motoneuron excitability dysfunction in the literature represent a substantial barrier to our understanding of the disease. Emerging studies suggest that biological variables, variations in experimental protocols, issues of rigor and sampling/analysis strategies are key factors that may underlie conflicting data in the literature. This review highlights potential confounding factors for researchers to consider and also offers ideas on avoiding pitfalls and improving robustness of data.

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How to Test the Operation and Monitoring of Critical Wastewater Infrastructure in a Laboratory Environment
Authors: Tilcher David Konstantin , Bölter Christopher , Mühlefeldt Max , Thamsen Paul Uwe
Published: September 2022

Increasing urbanization and the effects of climate change pose new challenges to our wastewater systems. One way to meet these challenges is to develop new control approaches. However, testing these approaches in real infrastructure is not easy: since wastewater systems are critical infrastructure, trouble-free operation is essential and renders the testing of new approaches as high-risk propositions.

Against this background, the idea of building a pumping station arose, allowing for operations in a laboratory environment and the testing of various control methods. At the same time, a digital twin was developed for the pumping station, creating a virtual image that is as close to reality as possible. The virtual image enables new control methods to be tested and their potential to be investigated in a time-efficient manner without the need for costly conversion measures.

Finally, coupling virtual and real pumping stations opens the possibility to test prediction-based control systems that simulate operating modes, based on a forecast and applicable quasi-simultaneously at the real pumping station.

The research results obtained in this way can be used as a basis for implementing new control methods in real infrastructure and as a demonstrator for potential interested parties (e.g. sewage network operators).
Study on the Entrainment Behaviors of the Droplet Jet Between Plates Considering the Hydrophobicity of the Plate
Authors: Wang Guanghang , Huang Jian , Wang Jingzhu , Wang Yiwei
Published: September 2022

A high-speed jet is formed when a pulse force acts on a concave interface of the liquid, which is due to the focus of the momentum on the center of curvature of the interface. We also found that there are fascinating jets in the experiments with a pulse acceleration imposed on the convex liquid interface while the arrangement is limited between two parallel panels. The mechanism of the convex interface jets is analyzed experimentally and numerically in this paper. A droplet with a diameter of approximately 12 mm is generated between two 0.8-mm spacing parallel plates coated with hydrophobic materials. A pulsed laser is focused at the center of the droplet through a convex lens to generate pulsed bubbles so that the movement of the interface is accelerated. The evolution of the liquid jets is observed by high-speed photography. A high-precision numerical method of the interface is established based on the volume of fluid method (VOF) and large eddy simulation (LES), which is enabled to capture the gas-liquid interface and small-scale flow structures exactly. An intriguing jet close to the plate is observed while the concave interface only forms that near the centerline. A charming entrainment phenomenon captured in the development of the jets, is mainly related to the big difference (Δθ) in contact angles between two plates, with a phase diagram given in the present work. Finally, a discussion responding to the influence of different contact angles on the tip velocity of a jet is done, concluding that the jet velocity increases gradually with the enlargement of Δθ to some extent. In addition, the hydrophobic plate, which is regarded as a mirrored plane and reflects the momentum of the fluid, plays a significant role in the formation of hydrophobic jets as well. Our findings offer a new understanding both of the formation of jets and surface cleaning.
Diffuser Vane Slit Width Optimization Using Simple Prediction Method of Diffuser Rotating Stall Onset in a Centrifugal Pump
Authors: Takao Shunya , Nakayama Sota , Konno Shinichi , Fujishima Yasushi , Ejiri Shinichiro , Miyabe Masahiro
Published: September 2022

The objective of this study is suppressing the diffuser rotating stall (DRS) for wide range from larger flow rate to shut off without reducing the maximum efficiency. Another objective is to confirm the effectiveness of the optimized diffuser vane slit by experiments and to clarify the mechanism of the DRS suppression by analyzing the flow in the vicinity of the slit, based on the Unsteady Reynolds-Averaged Navier-Stokes (URANS) calculation results.

As a result of a multi-objective optimization for the diffuser vane slit, the slit width, W = 9mm was comprehensively determined. As for the pump performance test, the diffuser with the optimized vane slit showed the stable head-flow performance curve compared to the diffuser with the original vane. It was clarified that the DRS onset flow rate of optimized shape shifted lower than original shape. As a result, the flow rate of the DRS onset could be shifted to the lower flow rate by 12%, and the operating range could be widened, though the pump efficiency decreased by 2.7% at the design flow rate.
Validation of Low and High-Fidelity Turbulence Models for Prediction of Turbulent Heat Transfer in Low Prandtl Number Flows Under Buoyant and Separated Flow Conditions
Authors: El Mellouki Mohammed , Bhushan Shanti , Pilmaier Chris , Walters D. K. , Gorman Michael , Hollrah Brent , Hassan Y. A. , Merzari Elia , Obabko Aleksandr , Dzodzo M. B.
Published: September 2022

The objective of this study is to assess the predictive capabilities of low and high-fidelity turbulence models for low-Prflows. For this purpose, predictions by two-equation (k-ε) Reynolds-Averaged Navier Stokes (RANS), partially-averaged Navier Stokes (PANS) hybrid RANS/Large Eddy Simulation (LES), and DSM, WALE, filtered LES models are compared for four different test cases, namely vertical channel flow, vertical backward facing step, flow over a rod bundle and heat transfer in ascending and descending flow through a pipe with a constant wall heat flux. The test cases involve a range of complex flow conditions including separation/reattachment and aiding and opposing buoyant forcing (Re ranging from 640 to 40K; Ri ranging from −0.65 to 0.65) for water (Pr = 0.71) and liquid metals (Pr = 0.00585 to 0.025) flows. The validation study demonstrates that turbulence models are 4% more accurate for higher Prflows that for low-Pr flows; 6% more accurate for forced convective conditions than for flows involving mixed convective conditions; and predict aiding buoyant flow conditions better than the opposing buoyant flow conditions. Overall, LES performed the best and provided averaged error of 6% followed by 10% by PANS and RANS showed the largest error of 14%.
Design Optimization of Laser-Induced Bubble for Highly Efficient Generation of Microjets
Authors: Ishikawa Tatsumasa , Nishida Hiroyuki , Tagawa Yoshiyuki
Published: September 2022

A device generating high-speed microjets from a liquid-filled microtube with laser-induced bubbles gets attention due to possibility of various engineering applications. In this study, we optimized the placement and bubble size of the laser-induced bubbles to maximize the efficiency of microjet generation. In the optimization, we use the Covariance Matrix Adaptation Evolution Strategy, which is one of the evolutionary algorithms. And a compressible multiphase flow solver based on the 5-equation model is used to evaluate the solution. Furthermore, data mining techniques using correlation analysis and dimensionality reduction algorithms are applied for extracting features related to the efficiency of microjet generation. Our result shows that it is effective to generate a laser-induced bubble near the tube wall. In addition, it is found that smaller volume and lower energy bubbles can provide efficient microjet generation. These results from the optimization and data mining are important for producing high-speed jets at low energy.
Research on Effects of Tunnel Buffer Structures on the Aerodynamic Force of the Pantograph
Authors: Cheng Jionghao , Guo Dilong , Yang Guowei , Ji Zhanling , Chen Dawei
Published: September 2022

The pantograph subjected to sudden changes of the airflow while a high-speed train passes through the entrance and the exit of tunnels and the aerodynamic force acted on the pantograph fluctuate significantly, which can result in bad influence to the current characteristics of the pantograph. Aimed at studying the effect of buffer structures on such issue, the aerodynamic force of pantograph while passing through a tunnel with buffer structures, including bell mouth hoods, oblique hoods, and constant cross section (with the same cross section area to main tunnel) hoods were simulated by utilizing CFD software. The object of this study is a full-scale CRH380A train model composed of three groups with the CED400 pantograph model. The IDDES turbulence model combined the technique of overset grid is adopted in the computation. The results indicate that both the aerodynamic drag and lift fluctuation of the pantograph are reduced at the entrance and the exit of a tunnel with the bell mouth or side opening buffer structures, especially at the exit of the tunnel, the amplitude of lift force fluctuation can decrease to a quarter of the value in condition of conventional tunnels, the oblique hoods buffering structure has no obvious alleviation effects on the aerodynamic force fluctuations.
Inferring Unsteady Wake Flow Fields From Partial Data by Physics-Informed Neural Networks
Authors: Yan Chang , Ju Shengjun , Guo Dilong , Yang Guowei , Yao Shuanbao
Published: September 2022

Massive differential numerical computations are necessary in Computational Fluid Dynamics. In addition, the experimental results are generally noisy. Consequently, traditional methods cannot get unsteady flow fields immediately and precisely. In this research, the inferences of unsteady wake flow fields at different Reynolds numbers by Physics-Informed Neural Networks (PINNs) are studied. Unlike typical neural networks whose loss function consists of Mean Square Error only, the loss function of PINNs consists of Mean Square Error and the sum of squares of residuals of the flow governing equations. The flow governing equations are introduced to the neural networks as a regularization of the loss function. The existence of regular term reduces the dependence on labeled data during training. Then the PINNs is trained with very little labeled data (5% of the full field). After being trained, the PINNs show excellent performance in inferring the unsteady wake flow fields. When the Reynolds number is 1e2, the Mean Absolute Error (MAE) of the reconstructed velocity field is on the order of 1e−4. Meanwhile, the MAE increases with the increase of Reynolds number. In addition, even if the random noise of the training set is introduced up to 20%, the result is still acceptable, which demonstrates the great anti-noise ability of physics-informed neural networks.
Time-Resolved Measurements for the Detection of Clogging Mechanisms
Authors: Beck David , Brokhausen Florian , Thamsen Paul Uwe
Published: September 2022

The effects of clogging in pumps are manifold and change over time. This is demonstrated with time-resolved observations of the operating data on a test rig at the chair of fluid system dynamics of the Technische Universität Berlin. On the test rig, the head, flow, power consumption and efficiency of different pumps operating with artificial wastewater are recorded.

In the data, different clogging behavior reflect in the operating parameters. There are three major clogging-induced characteristics to be differentiated in the time-resolved measurements. For some aggregates there is a rapid drop in the hydraulic parameters right from the start due to initial clogging, with following stagnating performance. This is showcased on a semi-open two-channel impeller, where efficiency drops by 40 % at the very beginning of the measurement and subsequently stagnates. In other cases, like demonstrated here on a closed two-channel impeller, the operating parameters decline continuously over the entire measurement period due to increasing clogging. In the showcased example, the efficiency drops by over 40% in the first six minutes of the measurement due to initial clogging and keeps declining till the end for another 6%. Lastly, there are cases where self-cleansing mechanisms are identified. It is further shown that this phenomenon also highly varies in its timing and hydraulic effects.

Finally, it is concluded that all operating parameters must be monitored to generate sufficient knowledge about the clogging behavior of a given aggregate. Additionally, longer observation times are necessary to sufficiently identify effects like the self-cleansing of an impeller.
Experimental and Numerical Study on Solid Particle Erosion of Standard Elbows in Dispersed-Bubble Flow
Authors: Bilal F. S. , Othayq M. M. , Sedrez T. A. , Shirazi S. A.
Published: September 2022

Solid particle erosion is an important subject when it comes to pipelines carrying solid particles in mining and oil and gas operations when sand production occurs. For that, to predict erosion that occurs and to maintain equipment integrity, the erosion phenomenon has been widely investigated over recent years. For pipelines carrying multiphase (gas-liquid-sand) flows, solid particle erosion is affected by superficial gas and liquid velocities, particle size and shape, and flow regime. This work aims to investigate the effect on the erosion of two multiphase cases with similar mixture velocity but different superficial gas and liquid velocities in 2-inch (50.8 mm) standard (r/D = 1.5) elbows. Flow visualization experiments were conducted to observe the flow regime. The cases considered are dispersed-bubble flow and churn flow based on the predicted flow pattern maps. However, flow visualization studies indicated that the flow regime is dispersed-bubble flows for both cases. Also, paint removal tests were conducted using an acrylic box painted with black paint to study the erosion pattern. In addition, CFD simulations were performed to compare the erosion patterns and the location of the maximum erosion with the paint removal patterns obtained with the paint removal tests. The location of the maximum erosion and erosion patterns agrees with the paint removal tests. However, the CFD simulations showed different erosion magnitudes even though the mixture velocity is equal; one case showed higher erosion by a factor of 2.5 as compared to the other.
Experimental Investigation in Turbulent Shear Mixing Layer at Supercritical Condition
Authors: Lim Chang Hyeon , Johnston Stephen R. , Ranjan Devesh
Published: September 2022

With limitations of traditional power cycles on their operating temperature ranges and max efficiencies, the research community has shifted the attention to usage of supercritical fluids as the main working fluid of power cycles. Among the supercritical fluids, supercritical carbon dioxide (sCO2) is considered as the most promising candidate for its relatively low critical point, low cost, and availability. The main merit of using sCO2 is its high density near the fluid’s critical point, which reduces the required compression power. This leads to decrease in the volume of turbomachinery and increase in the overall cycle efficiency. However, non-linear property variations and mixing of different supercritical regimes in close proximity to the critical point pose great risks for cycles taking the full advantage of these benefits. The non-linear property variations close to the critical point provide a challenge in developing a multiphysics model, which can serve as a backbone for simulating more advanced geometries of sCO2 power cycle processes.

To understand the physical phenomena of property variations and mixing of supercritical fluids at differing conditions, a classical shear layer experiment is performed in a high-pressure test chamber with supporting closed-loop cycle facilities. Experiments are conducted under various fluid density and velocity ratios at multiple isobars to understand if classical mixing theories and hydrodynamics follow the same trend in supercritical conditions. Specifically, turbulent flow characteristics and the growth parameters are captured through density gradients between two channels using Schlieren visualization. The qualitative results show that the mixing interfacial features follow the classical mixing growth rate theories despite nonlinear fluid property variations. Dissipative nature of the supercritical fluids contributes to resemblance of gas-gas mixing and presents decrease in mixing intensity as inlet conditions deviate away from the critical point.
Optimizing VCC Air Conditioner Systems in Arid Climates: A Dubai Residence As Case Study
Authors: Abdalla Ahmad , Islam Md. , Al Alili Ali , Alhassan Saeed , Qureshi O. A. , Rodriguez-Ubinas Edwin
Published: September 2022

Given the extreme hot and humid ambient conditions of UAE, it comes no surprise that the demand for air conditioning would increase rapidly. In the UAE, roughly 90% of the electricity is consumed by the building sector. In that sector, air conditioners (A/Cs) consume about 80% of the total annual house electricity. The fact that performance of A/Cs decreases as the ambient temperature increases. Additional challenge to optimize energy consumption is that in hot and humid regions A/C units are simultaneously required to control the temperature and humidity. Thus, oversized A/C units are usually used which increases the energy consumption and affect indoor thermal comfort. This study aimed to analyze the implementation of the ASHRAE standard in a residence in Dubai. Transient System Simulation (TRNSYS) program is selected to study a detailed analysis of a residential building implementing ASHRAE building standards. The goal is to reach to an indoor temperature of 22.5°C and a 50% relative humidity according to ASHRAE standards. The values obtained from running the simulation over all the zones can now be used in order to size the A/C system. The maximum required load for all zones is 59.6 kW, however after applying the optimization method it was reduced by 4,5% to reach 56.9kW.
Study of Thixotropic Behavior of Non-Newtonian Fluids in Tool-Joints of Oil Wells
Authors: Gholami Ardeshir , Mansoori Zohreh , Saffar Avval Majid , Ahmadi Goodarz
Published: September 2022

The prediction of frictional pressure loss in many oil wells drillings is of the utmost importance. Most studies in this area are concerned with fluid flow in pipes and annulus to predict friction losses. However, studies on the tool-joint effect in frictional pressure estimations were limited to only a few experimental and theoretical studies on water-based power-law and Herschel-Bulkley drilling muds. Tool-joint is the piece that connects two drill strings. The tool joint plays an important role in extending the drill pipe, and its effect on pressure losses cannot be ignored. In addition, the drilling muds must have certain qualities such as providing formation integrity, transporting the cuttings from bit to surface, drilling pipe lubrication and heat transfer, and low-pressure loss to perform as a qualified and effective drilling fluid. Therefore, drilling muds have become more complex and expensive. For this reason, oil-based viscoplastic drilling muds are being used in more drilling operations. These drilling muds almost always also show a thixotropic behavior which is the key point of this study.

This paper studied the behavior of fluid flows and frictional pressure losses in weld-on tool-joints of different grades using CFD simulations. The simulations were conducted for a drilling fluid with viscoplastic (similar to the Herschel-Bulkley model) and thixotropic behavior. The characteristics of fluid flows in tool joints under different thermal boundary conditions were studied. Moreover, the different thixotropic behavior models and various thixotropic boundary conditions were compared to select the most fitting model. The results showed that tool joints significantly affect the frictional pressure loss in the annulus. The study also provided an accurate pressure loss prediction for the flow of oil-based viscoplastic muds passing through the tool-joint geometry. Furthermore, using the thixotropic behavior of the Moore-Cheng model for the drilling mud, the transient processes of the beginning of the drilling operations were investigated.
Generation Mechanism of High-Frequency Sound Induced by Supersonic Jet Impinging on Flat Plate
Authors: Suzuki Hiromasa , Endo Masaki , Sakakibara Yoko
Published: September 2022

The underexpanded jet is well known as one of the supersonic jets, and it is formed when the pressure ratio across a convergent nozzle from which the jet is exhausted is more than the critical value. The underexpanded jet has a characteristic barrel-shaped cellular structure. When the underexpanded jet impinges on a flat plate, a detached shock wave called “plate shock” is formed in front of the flat plate. Such flow fields are utilized in industrial applications such as laser processing and tempered glass manufacturing processes. The impinging jet oscillates and induces the high frequency sound called “screech tone”. The present study focused on the screech tone generated from the underexpanded jet impinging on the flat plate and aimed to examine a relation between the high-frequency sound and the jet structure. In the experiment, the jet impinged on a flat plate or a mesh, and the flow characteristics of each case were compared. The pressure ratio was kept constant at 3.0 and the distance between the nozzle and the object being impinged by the jet was changed. Visualization of the flow field and acoustic measurement were carried out under each condition. As a result, integral multiples of the fundamental frequency in the impingement on the mesh agreed with the frequency of the screech tone generated in the impingement on the flat plate. Since the screech tone frequency is based on the feedback loop between the nozzle and the flat plate, this agreement indicates the screech tone is caused by the agreement of the harmonic frequency of the feedback loop between the nozzle and the plate shock with that between the nozzle and the flat plate.
Vortex Identification in Large Eddy Simulations Under the Lattice Boltzmann Framework With a Smagorinsky Subgrid Model
Authors: Jaber Khodr , Essel Ebenezer Ekow , Sullivan Pierre
Published: September 2022

The recent emergence of turbulence modeling strategies under the Lattice Boltzmann Method (LBM) framework has opened the door towards highly efficient numerical solutions for the governing fluids equations with potential application to industry. Advantages of the LBM over traditional Navier-Stokes (NS) based methods include its straightforward parallelization and its ability to recover flow dynamics without explicit treatment for pressure. In the present work, Large Eddy Simulation within a Lattice Boltzmann framework is used to study a lid-driven cavity. In particular, a Smagorinsky subgrid scale model is chosen for the unresolved scales within a single-relaxation-time LBM. Simulations are performed in three dimensions at a Reynolds number of 105. One-dimensional energy spectra are computed and the range of energy scales in the numerical solutions are inspected to ensure that turbulence has been captured. Isosurfaces of various vortex identification criteria are examined and compared to the vorticity magnitude and pressure minima.
Photosynthetic Micro-Swimmers in Oscillating Flow
Authors: Pashmi Elnaz , Peerhossaini Hassan , Jarrahi Mojtaba
Published: September 2022

Swimming and transport of the photosynthetic alga Chlamydomonas reinhardtii in steady and oscillatory shear flows were investigated. Sinusoidal flow of algal suspension was generated in the microchannels using a microfluidic pressure-driven controller. The oscillating flow was expressed as Q (t) = A. sin (ωt) where Q (t), t, A, and ω, represent the instantaneous flow rate, time, amplitude and angular frequency of the oscillating flow, respectively. The different amplitudes considered in the study were A = 0.075, 0.15, 0.22, 0.3 and 0.5 μl/min. Maximum mean velocities corresponding to this range of amplitudes varies between 14.7 μm/s and 392 μm/s depending on the microchannel used in the experiment. At each amplitude, four frequencies were applied: f = 0.5, 1, 2 and 3.3 Hz. The motion of algal cells was recorded and their trajectories in the flow were analyzed. It was shown that the dynamics of cells in the steady flow varies from a random motion to a zigzag motion depending on the flow shear rate. At low shear rates, the average value of the angle (α) between the cell trajectory and flow stream was 40°, and a zigzag motion of the cells was observed between the lateral walls. However, at higher flow shear rates, the mean value of this angle was about 10° with a smaller distribution range (0° < α < 30°) compared to the low shear regime (10° < α < 70°). When the flow condition was turned to a sinusoidal flow, two strong symmetric peaks appeared close to ± 90° in the probability distribution of α. The visualizations of cell trajectories showed that the cells swim perpendicular to the flow direction in wavy-form trajectories such that regardless of the oscillation conditions, their average vertical velocity (Vy) is equal to their motility (130 μm/s).
Ventilation System Performance on the Removal of Respiratory Droplets Emitted During Speaking
Authors: Masoomi Morteza Ali , Salmanzadeh Mazyar , Ahmadi Goodarz
Published: September 2022

The SARS-CoV-2 infection pandemic has led to significant loss of lives and worldwide economic disruption. The leading cause of transmission of infectious respiratory diseases is through aerosolized mucous and salivary droplets containing the virus emitted into the environment through respiratory activities. Depending on their initial size, the droplets evaporate or fall to the ground due to gravitational sedimentation. When a droplet evaporates, the droplet nucleus containing all the viruses in the original droplet remains airborne in the environment for a long duration of time. The ventilation system significantly affects the dispersion and removal of particles from the environment. Therefore, poorly ventilated indoor environments increase the risk of disease transmission. The present study modeled a ventilated small office space with two mannequins sitting across a table. It was assumed that one of the mannequins was speaking and emitting small droplets. Then the effect of the ventilation system on the droplets’ transport and dispersion was simulated. In particular, the performance of the displacement and mixing ventilation systems on particle dispersion and deposition in the room were evaluated and compared. These simulations were performed using the computational fluid dynamics (CFD) approach with Ansys-Fluent software. The Eulerian approach was used to simulate the airflow field in the room, and the Lagrangian trajectory analysis approach was used for the droplets. Experimental data of the thermal plume above the mannequin’s head were used to validate the airflow simulation results. The results showed that the displacement ventilation system has better performance (almost three times more) in removing particles from the environment than the mixing ventilation system.
Dynamic Transition From Mach to Regular Reflection Over a Moving Wedge
Authors: Margha Lubna , Hamada Ahmed A. , Eltaweel Ahmed
Published: September 2022

The design of supersonic and hypersonic air-breathing vehicles is influenced by the transition between the Mach Reflection (MR) and Regular Reflection (RR) phenomena. The purpose of this study is to investigate the dynamic transition of unsteady supersonic flow from MR to RR over a two-dimensional wedge numerically. The trailing edge of the wedge moves downstream along the x-direction with a velocity, V(t) at a free-stream Mach number of. An unsteady compressible inviscid flow solver is used to simulate the phenomenon. Further, the Arbitrary Lagrangian-Eulerian (ALE) technique is applied to deform the mesh during the wedge motion. The dynamic transition from MR to RR is defined by two criteria, the sonic and the Von-Neumann. Moreover, the lag in the dynamic transition from the steady-state condition is studied using various reduced frequencies, κ, in the range of [0.1–2]. The lag effect in the shock system is remarkable at the high values of the reduced frequency, κ = 1.5 and 2.0. Furthermore, because the shock is bent upstream during the fast motion of the wedge, the transition from MR to RR happens below the Dual Solution Domain (DSD).
Numerical Simulation of Anti-Icing Effect With Dielectric Barrier Discharge Plasma Actuators on a Surface of an Airfoil
Authors: Rodrigues F. , Abdollahzadeh M. , Bagherighajari F. , Páscoa J.
Published: September 2022

Ice accumulation is a big issue for both aeronautical and wind power industries. In an attempt to optimize the aerodynamic performance and prevent the ice accumulation in different components of aircraft and wind turbines, plasma actuators started to be studied as devices that allow to perform simultaneously flow control and ice accretion prevention. Considering the use of plasma actuators for flow control and ice prevention, in the current work numerical simulations were performed in order to investigate the anti-icing ability of dielectric barrier discharge (DBD) plasma actuators applied on a NACA 0012 airfoil. In a first stage, DBD plasma actuators were fabricated and experimentally tested in order to estimate the heat flux produced by these devices during their operation. An innovative calorimetric method, developed in our lab, was implemented in order to estimate the thermal power transferred by these devices to an adjacent flow. In this technique the actuators are placed inside a calorimeter with the shape of a pipe with a constant airflow rate. When the actuator is operated the heat dissipated from the plasma discharge is transferred to adjacent flow and the temperature of the flow is monitored at the outlet. By using the fundamental calorimetric law, the heat flux from the actuator to the adjacent air can be estimated. In a second phase, an airfoil NACA 0012 with multi-DBD plasma actuators was studied in favorable conditions for ice accretion. The accumulation of ice on the airfoil surface was analyzed for the condition with and without the thermal effect created by the DBD plasma actuators. The heat effect produced by the DBD devices was simulated considering the heat flux obtained on the calorimetric experiments. The results showed that plasma actuators allow to induce significant thermal effects that can be used for performing anti-icing and deicing functions. These simple electronic devices can be used to reduce the icing zone near the airfoil and improve its aerodynamic characteristics.
Optimization of an Elliptical Fairing in the Wake of a D-Shaped Bluff Body
Authors: Amaya Luis , Loubimov George , Kinzel Michael
Published: September 2022

Although streamlined geometries are well studied in the context of direct exposure to a flow, when they are in the wake of a bluff body the aerodynamic performance is less understood. In these scenarios complexities arise such as interactions with vortices that lead alter the aerodynamics. Such unsteady nature changes optimal streamlining in a bluff body wake. For this reason, this study will explore variations of an elliptical body at several points in the wake of a D-tube shaped object. The goal is to outline a general characterization of such a case to facilitate in designing for and understanding situations with bluff body wakes.
Incremental Sheet Forming of the WKU Big Red Mascot
Authors: Rezasoltani Asghar , Crocker Matthew , Rice Jeremy , Black Avery
Published: September 2022

The robotic incremental sheet forming process, including the CAD design, programming, and robotic manufacturing, as performed to form the school’s Big Red Mascot shape on a flat 30″ × 30″, gauge 26, AL 3003 sheet is explained in this research. This paper explains the technics used in the design, programming, and manufacturing processes to avoid or minimize typical ISF manufacturing problems such as spring-back effect, pillow effect, orange peel effect, and maximum wall angles.

The quality of the forming process was investigated visually and by measuring the surface quality and geometric accuracy using a surface tester machine and a 3D scanner. The novelty of the work is the ISF manufacturing of the complex Big Red shape compared to the simple shapes reported in other research, as well as the experimental and measurement setup used in this research.
Performance Prediction of Resistance Spot Welding Joints Using a Modified GTN Model
Authors: Wen Weiling , Banu Mihaela
Published: September 2022

Nowadays Al-steel joints are increasingly used in the lightweight automobile structure to meet the requirement of energy saving and CO2 emission reduction. Among various joining technologies proposed to join dissimilar material, resistance spot welding (RSW) stands out since the operation speed is fast, no extra material is needed and it is easy to be automated in mass production. Determining the joint load bearing capacity is one important task in the further application of this technology. Traditionally, it is obtained by performing some fractured tests, such as lap-shear test, coach peel test, cross tension test, by extracting and then analyzing the mechanical performance parameters including maximum load and failure energy from the force-and-displacement (F-D) curves. However, this method is time consuming and finite element simulation provides a much more efficient solution. Therefore, this work aimed at developing an experimentally validated performance model of Al-steel RSW joint. An aluminum alloy (AA6022) and a hot-dip galvanized high strength low alloy steel (HDG HSLA340), both of which are widely used in automotive industry, were joined by a unique RSW process proposed by General Motors in lap-shear configuration. To predict the joint fracture, a modified Gurson-Tvergaard-Needleman (GTN) model was applied. Finally, this performance model was validated experimentally and proved to be capable of predicting the maximum load and failure energy accurately.
Proof of Authenticity Statistics From Multiple Perceptual Hash Comparisons: A Case Study
Authors: Maasberg Michele , Butler Leslie G. , Birch Brendan , Trailer Maia
Published: September 2022

The COVID-19 global pandemic created an optimal environment for counterfeiters to exploit vulnerabilities in the manufacturing industry. The decentralized and global nature of additive manufacturing (AM) systems created new attack vectors for counterfeiting due to ease of compromise of product and process information. To solve this challenge, innovative technologies and scientifically reliable methods for predicting authenticity are in great demand. In this work, a framework for differentiating between authentic and counterfeit AM automotive and aerospace components is proposed. Extant literature was reviewed and current anti-counterfeit technologies analyzed, informing the basis of the framework. The process was validated with a castle nut printed via selective laser-melting of a stainless steel M18 castle nut slightly modified with a Cantor dust fractal. The castle nut was then inspected with 225 and 450 kV X-ray tomography to assess the fidelity of fractal structure. A model trust anchor image sequence was developed and analyzed with a perceptual hash, Hamming distance computations, distribution functions, and null hypothesis for proof of authenticity. For authentic parts, a blockchain was updated with provenance. Future work will explore wider implementation with the goal of reducing prevalence of counterfeit parts in AM manufacturing systems.
Simulating Residual Stress at Critical Features of Straightened Hollow Transmission Shafts
Authors: Chodubski Michael
Published: September 2022

Simulating plastic deformation of a material with a strength gradient from surface to center is not a standard industry practice. Although separate engineering groups have capabilities to perform thermal-structural or operational load analysis, neither have combined nor is focused on integrating effects from heat treatment and straightening operations. The objective of this research is to develop a simulation model to predict axial residual stress at radial holes in a carburized hollow transmission shaft. Abaqus CAE coupled with DANTE Heat Treatment kinetics software will be utilized to simulate the evolution of thermal and mechanical properties of different carburized shaft designs to determine the resulting residual stress at key features. Simulation data shows that the case and core layers react differently to features when a shaft has a bending or straightening load applied. Generally, shafts with smaller radial holes and a farther loading source exhibited compressive axial residual stresses at the case layer with lower average core tensile residual stresses while the shafts with larger radial hole diameters began with tensile stresses at the case following thru higher average core tensile stresses. The radial hole diameter and location only affected the case layer while all three studied features; hole diameter, location, and chamfer size, had significance on the core residual stress. This goes to show that the case and core layers are more complicated than previously thought. Future work should investigate further into how the core residual stresses play a role in fatigue failures.
Selective Laser Melting of Crack-Free Ti-48Al-2Cr-2Nb Alloy: Improved Manufacturability by Powder Surface Modification Using Graphene Oxide
Authors: Zhang Xing , Li Dian , Zheng Yufeng , Liao Yiliang
Published: September 2022

Intermetallic γ-TiAl based alloys have been developed for high-temperature lightweight applications in aerospace and automotive industries. However, their fabrication via selective laser melting (SLM) remains a great challenge due to the severe cracking issue and unsatisfied mechanical properties. In this study, we present a novel manufacturing strategy to significantly improve the printability of a Ti-48Al-2Cr-2Nb (Ti-4822, at.%) alloy for SLM by powder surface modification. Specially, graphene oxide (GO) sheets were decorated onto the metallic powder surface via the electrostatic adsorption process. Results indicated that crack-free samples could be fabricated by adding 0.1–0.5 wt.% GO during SLM experiments. The microstructure as affected by GO addition was characterized by backscatter electron imaging and electron backscatter diffraction, showing that the dual-phase (α2 + γ) cellular structure was refined at both grain and sub-grain scales. Further characterization by a three-dimensional focused ion beam-scanning electron microscopy tomography demonstrated the increased volume fraction of γ phase and the reduced porosity with GO addition. Finally, the surface strength of as-fabricated Ti-4822 was evaluated by microhardness test, demonstrating a maximal enhancement of 21.9% when modified using 0.3 wt.% GO. We envision that the proposed manufacturing strategy has provided new perspectives for the design and production of high-performance γ-TiAl based alloys via SLM.