bluuebunny/crossref_metadata_2025 huggingface dataset:
Triangular Mechanical Structure of the Proximal Femur
Authors: Xu Gaoxiang , Li Jiantao , Xu Cheng , Xiong Dou , Li Hua , Wang Daofeng , Zhang Wupeng , Zhang Hao , Zhang Licheng , Tang Peifu
Published: September 2022

Objective

The mechanical high modulus structure of the proximal femur could guide clinical surgical treatment and instrument design of proximal femoral fractures. The purpose of this study is to analyze and verify the mechanical structure of the proximal femur.

Methods

A total of 375 patients with intertrochanteric fractures were imaged using computed tomography (CT) scans. Patients were grouped according to age and sex. Cortical and medullary cavity parameters (cortical thickness [CTh], cortical mean density [CM], upper‐lower diameter length [ULL], and medial‐lateral diameter length [MLL]) were measured at eight planes. Six proximal femoral finite element models of different sexes and ages were constructed. To verify the measurement results, Abaqus was used to implement the force load to describe the von Mises stress distribution, and the maximum von Mises stress values of each wall of the proximal femur were compared.

Results

The CTh values of the lower and upper walls were higher than those of the anterior and posterior walls of the femoral neck (p < 0.05). The CM values of the lower and upper walls were higher than those of the anterior and posterior walls of the subcephalic and middle femoral neck (p < 0.05). The ULL value gradually increased from the subcephalic region to the bottom (p < 0.05). The CTh and CM values of the medial and lateral walls were higher than those of the anterior and posterior walls in the femoral trochanteric region (p < 0.05). The MLL value decreased gradually from the plane 20 mm above the upper edge to that 20 mm below the vertex of the femoral lesser trochanter (p < 0.05). The von Mises stress was concentrated on the upper and lower walls of the femoral neck and on the medial and lateral walls of the femoral trochanteric region. The maximum von Mises stress values of the upper and lower walls were higher than those of the anterior and posterior walls of the femoral neck. The maximum von Mises stress values of the medial and lateral walls were higher than those of the anterior and posterior walls in the femoral trochanteric region, except for the plane 20 mm above the upper edge of the femoral lesser trochanter.

Conclusion

The bone mass of the proximal femur presented a triangular high‐modulus distribution, which bore the main stress of the proximal femur. The triangular mechanical structure provides a guideline for the surgical strategy and instrument design of the proximal femur.
Hydrocolloid dressing for the treatment of severe diaper dermatitis
Authors: Giacaman Aniza , Boix‐Vilanova Julián , Martín‐Santiago Ana
Published: September 2022

Diaper dermatitis is a common dermatosis that usually responds to adequate hygiene and topical treatment, but can be a therapeutic challenge. Continuous exposure to feces and urine can cause extensive erosions and pain. The use of hydrocolloid dressings may be helpful in keeping the skin isolated from stool and urine, reducing pain, and enabling skin lesions to heal. We explain an easy technique, utilizing stoma powder and a hydrocolloid dressing, for parents to apply at home.
Drug‐induced crystalluria attributable to tosufloxacin in children
Authors: Atsumi Yukari , Yamanaka Haruka , Shimozawa Katsuyoshi , Yamanaka Junko , Uryu Hideko , Mizukami Ayumi , Shichino Hiroyuki
Published: September 2022

Background

Drug‐induced crystalluria is reportedly caused by a large number of drugs. Tosufloxacin (TFLX), a second‐generation fluoroquinolone antibiotic, is reported to cause kidney injury and crystalluria. We retrospectively analyzed patients with crystalluria caused by TFLX to clarify the clinical course of TFLX‐induced crystalluria in children.

Methods

This study was designed as a retrospective case series using the database of the National Center for Global Medicine covering the period from January 1, 2020 to March 31, 2021. We enrolled pediatric patients aged 15 years or younger with crystalluria attributable to TFLX treated in our pediatric department and collected clinical data.

Results

Thirteen patients were diagnosed with crystalluria attributable to TFLX. The median age of the patients at diagnosis was 4.0 years (range, 0.8–15 years; interquartile range = 1.2–8.8 years), and five patients (38%) were male. Six patients (46%) had gastrointestinal symptoms such as vomiting and abdominal pain, and 12 patients (92%) had decreased oral intake. The median time to diagnosis after TFLX administration was 4 days (range, 2–7 days; interquartile range = 3–6 days). All patients received TFLX at the appropriate dose. Two patients (17%) were diagnosed with acute kidney injury, and both had gastrointestinal symptoms such as vomiting and abdominal pain.

Conclusions

Crystalluria induced by TFLX occurred despite administration of the appropriate dose of TFLX. Physicians should recognize crystalluria and renal injury attributable to TFLX. It may be possible to prevent renal injury by discontinuing drug therapy.
The post‐ovulatory rise in progesterone is lower and the persistence of oestrous behaviour longer during the first compared with the second cycle of the breeding season in mares
Authors: Newcombe John R. , Wilsher Sandra , Cuervo‐Arango Juan
Published: September 2022

Mares are seasonally polyoestrous breeders. Therefore, the first ovulation of the season, following winter anoestrus, is the only cycle in which mares ovulate without the presence of an old CL from the previous cycle. The objective of this study was to compare the length of oestrous behaviour, and plasma progesterone concentrations during the early post‐ovulatory period between mares after the first and second ovulation of the breeding season. Overall, 38 mares and 167 oestrous periods were used in the study. From those, 11 mares were used during the first and subsequent oestrous period to measure and compare the post‐ovulatory rise in progesterone concentration, whereas all the mares were used to compare the length of the post‐ovulatory oestrous behaviour between the first and subsequent cycles of the breeding season. The persistence of the post‐ovulatory oestrus was longer (p < .001) following the first ovulation of the year (median of 52 h) compared with the subsequent ovulations (median of 36 h for second and later ovulations groups; n = 38 mares). The progesterone concentration at any of the four 8 h‐intervals analysed (28, 36, 76 and 84 h post‐ovulation) was lower (p < .01) following the first versus the second ovulation of the year. By 36 h post‐ovulation the progesterone concentration of mares at the second ovulation of the year had passed the threshold of 2 ng/ml (2.1 ± 0.33 ng/ml), whereas in the first cycle it was 1.2 ± 0.13 ng/ml. In conclusion, mares had lower progesterone concentrations in their peripheral circulation and longer persistence of oestrous behaviour following the first ovulation of the year compared with the second and subsequent ovulatory periods of the breeding season.
Hemostatic function of cold‐stored platelets in a thrombocytopenic rabbit bleeding model
Authors: Nogawa Masayuki , Watanabe Naohide , Koike Toshiyasu , Fukuda Kanae , Ishiguro Mariko , Fujino Hitomi , Hirayama Junichi , Shiba Masayuki , Handa Makoto , Mori Takehiko , Okamoto Shinichiro , Miyata Shigeki , Satake Masahiro
Published: September 2022

Background

Transfusion of cold‐stored platelet concentrates (CS‐PCs) appears effective in massively bleeding patients. However, few studies have evaluated their in vivo hemostatic function in severe thrombocytopenia.

Study Design and Methods

The in vivo function of plasma‐depleted human PCs was evaluated in rabbits with a blocked reticuloendothelial system and busulfan‐induced thrombocytopenia. On day 1, a human apheresis PC was processed in a platelet additive solution (PAS‐PC) and split evenly for cold or room temperature storage (RTS). On days 3, 6, or 9, RTS‐ or CS‐PAS‐PCs were transfused (4.0 × 109 platelets/kg) after plasma depletion into two to four rabbits that developed adequate thrombocytopenia (<25 × 109/L). Ear bleeding time was measured by two incisions in small veins. The hemostatic rate was defined as the percentage of rabbits achieving bleeding cessation within 600 s at either incision. The experiment was repeated using five different PCs on each storage day.

Results

The mean pre‐transfusion rabbit platelet count was 8.6 ± 5.2 × 109/L. The hemostatic rates with RTS‐ and CS‐PAS‐PCs were both 100% on day 3, 93 ± 15% and 73 ± 15% on day 6 (p = .07), and 65 ± 36% and 73 ± 37% on day 9 (p = .27), respectively, with no statistical differences. Total platelet counts were significantly lower after CS‐PAS‐PC than RTS‐PAS‐PC transfusion on all days (e.g., 58.7 ± 5.7 vs. 42.4 ± 14.7 × 109/L, p = .0007, day 9), and did not reach 50 × 109/L in several experiments. Platelet count increments correlated significantly with hemostatic efficacy for CS‐PAS‐PC transfusion only.

Discussion

CS‐PAS‐PCs might achieve similar hemostasis as RTS‐PAS‐PCs in thrombocytopenic patients with mild bleeding. Hemostatic efficacy could be improved by transfusing more CS‐PAS‐PCs.
Uncertainty Quantification and Sensitivity Analysis of Semi-Mechanistic Models for Sand Erosion in Elbows for Single and Multiphase Flows
Authors: Vieira Ronald E. , Shirazi Siamack A.
Published: September 2022

An accurate prediction of erosion in pipe fittings is a key aspect in the design process and during real-time control strategies of fluid transport facilities. Along with CFD simulations, semi-mechanistic models are commonly used for this purpose. These models predict erosion rates in a large variety of flow conditions with reasonable agreement with existing data, but no tool is available to quantify the uncertainty of these models. In addition, due to the error in measuring the input data, an uncertainty quantification tool is also needed for model validation. In this work, uncertainty quantification and sensitivity analysis are performed to quantify the level of confidence in predictions of one-dimensional mechanistic models for erosion in elbows considering single-phase and multi-phase flow regimes. A method is proposed for this purpose accounting for the effect of several variables on erosion predictions, such as fluid flow rates, geometry, solid and fluid properties. Monte Carlo simulations were used for the uncertainty quantification while two approaches for the sensitivity analysis (the screening and variance-based methods) were used to identify which variables the predictions are most sensitive to. The most critical input parameters in terms of uncertainty are rigorously identified case by case. The prediction intervals for erosion in elbows for different gas-liquid flow patterns in vertical flow are obtained from knowledge of the measurement error in the variables provided to the model. The model predictions are also compared to experiments while accounting for uncertainty. The results of this work give new insights regarding the degree of uncertainties in predictions of erosion rates in single and multiphase flows, providing an important tool for future experimental validations of erosion models.
Jet Erosion of Particle Beds: Projecting Critical Suspension Velocities From Effective Clearing / Cleaning Radii
Authors: Pease Leonard F. , Bamberger Judith Ann , Minette Michael J.
Published: September 2022

Here we explore the relationship between effective cleaning/clearing radii, ECR, and critical suspension velocities, Ucs. Although one set of physics controls both the radial extent of erosion (i.e., the ECR) and the velocity needed to erode from the center of jet impingement to any given location (i.e., Ucs, typically defined from nozzle center to the vessel center), the relationship between these two remains unexplored quantitatively for nominally non-cohesive solids. Here we advance the model of Kuhn, et al., (PNNL-22816, 2013) as described by Pease, et al. (FEDSM2017-69444, 2017) to evaluate the relationship between the effective clearing/cleaning radius and the nozzle velocity on flat surfaces including flat bottomed vessels. Two governing dimensionless groups are identified. We present both a closed form analytical but transcendental solution and a non-iterative approximation modeled after the Serghides approximation of Colebrook’s nonlinear equation for both ECR versus nozzle velocity and Ucs. Comparison of the model to data from flume testing on a flat surface finds reasonable agreement.
A Method for Numerical Evaluation of Singular Integrals in Curved Hexahedra and With High-Order Source Functions
Authors: Gharakhani Adrin , Stock Mark J.
Published: September 2022

A method is developed for evaluating the 3-D Biot-Savart singular integral for the velocity field induced by arbitrarily high-order (discontinuous) vorticity in arbitrarily high-order curved hexahedral elements. The proposed method uses Duffy’s coordinate transformation and singularity removal strategy, which, through a set of transformations, accommodates accurate evaluation of the transformed volume integrals using standard adaptive cubature techniques. In this paper, the new method is formulated in detail, followed by a series of benchmark tests demonstrating the convergence properties of the singular volume integral as a function of the discretization order of the vorticity (source) field.
Effect of the Macroscale on the Dynamics of a Slender Flexible Cylinder in Cross-Flow
Authors: Condo Felipe , Silva-Leon Jorge , Cioncolini Andrea
Published: September 2022

This paper studies how the turbulence intensity and macroscale generated by a passive grid located at different distances from a slender flexible cylinder (L/D = 120) affect its dynamics. The turbulence in the flow is the normalized deviation of the flow velocity, and it is important because it is related to the flow velocity variability. The macroscale length measures the size of the eddies in a flow (largest eddy size) and is related to the energy contained in the large eddies. Here we compute it using the power spectrum of the velocity at low frequencies. This helped us examine whether the size of an eddy would affect the flapping motion of the filament.

To manipulate the macroscale, a passive grid was placed at five different upstream locations with respect to the cylinder. Two high-speed cameras recorded the motion in the top and front plane while the cylinder was exposed to different wind speeds, which were increased in gradual steps.

We analyze the linear relationship of the motion in the vertical and horizontal planes. Furthermore, non-linear analysis of the data is used to determine the onset of the motion and determine whether it is a quasi-periodic or chaotic motion. The results show that the turbulence macroscale modification affects the critical velocity for the onset of the flapping motion. While the turbulence shifts the onset of the motion to the lower flow speeds, the motion exhibits less clear quasi-periodic behavior than in the case where there is no grid. The bifurcation diagrams show how the dimensionless amplitude in the vertical plane does not change for different macroscale lengths, while the motion in the horizontal plane does. Based on the analysis, turbulence does not seem to be related to the vertical plane motion, while the horizontal motion shows to be more chaotic, possibly a turbulent buffeting.
Study on Measurement Accuracy of State Parameters in Leakage Process of Supercritical CO2 Pipeline
Authors: Guo Xiaolu , Fan Zhichao , Xu Shuangqing , Wang Yunfeng , Yu Shuai
Published: September 2022

The carbon capture, transportation and storage (CCS) technology is an important option to achieve carbon emission reduction. Supercritical CO2 pipeline as its intermediate link, in order to prevent pipeline fracture propagation, human injury and transportation medium loss caused by leakage, it is necessary to establish a highly accurate on-line leakage monitoring technology. At present, the law of pressure and temperature response in supercritical CO2 pipeline leakage is not well understood, and the mechanism of pressure and temperature coupling mutation in the propagation of decompression wave is still unclear. Based on the experimental data of pipeline leakage, combined with theoretical analysis and numerical simulation, this paper studies the sudden change mechanism of pressure and temperature at the moment of leakage, analyzes the attenuation law of sudden drop rebound amplitude of pressure and temperature during the propagation of decompression wave, studies the influence of velocity error, dynamic error and other errors on sensor measurement, and puts forward an improved method of high-precision state parameter measurement.
Research on Fluid Dynamics and Thermal Characteristics in Hydraulic Valves by Thermal-Fluid-Solid Coupling Method
Authors: Nie Jia-xi , Lin Zhen-hao , Hao Jiao-shan , Jiang Yong-bing , Jin Zhi-jiang , Qian Jin-yuan
Published: September 2022

Hydraulic valve is used as an important hydraulic component, playing a vital role in fluid power transmission and control systems. When the phenomenon of sticking of valve core occurs, it may seriously decrease the accuracy and sensitivity of the hydraulic valve. Micro-deformation is one of the most common faults causing the valve core sticking, which is due to the thermal load. Therefore, studying the mechanism of valve core sticking caused by thermal fluid is of great significance. In this paper, the fluid dynamics in hydraulic valves and the temperature characteristics of valve core are analyzed based on the thermal-fluid-solid coupling method. Results show that the jet angle (θ) will decrease with the increase of opening degree (k), and the maximum velocity and temperature increase with the increase of the opening degree. By loading the temperature field into the thermal analysis as a boundary condition, it shows that the temperature of the U-throttle groove increases with the increase of the opening degree. In addition, with the increase of opening degree, the maximum thermal deformation increases and the contact pressure between valve core and valve body also increases. This work has a certain reference value for researching and improving the phenomenon of valve core stuck in hydraulic valve.
Development and Experimental Study of Ultra-High Pressure Abrasive Water Cutting Equipment for Deep-Sea Sunken Ship
Authors: Chen Zhengwen , Ren Qile , Su Jinxin , Wang Yongqiang , Xue Shengxiong , Han Caihong
Published: September 2022

Cutting and breaking the sunken ship in the deep-sea environment is an important step of salvage. Especially for the deep-sea sunken ship loaded with fuel and liquid dangerous chemicals, safe and efficient cutting and opening is the primary process to remove the dangerous liquid from the sunken ship. This paper expounded technical scheme of ultra-high pressure pre-mixed abrasive water cutting steel plate for 6000 meters deep-sea sunken ship, and introduced the development of 140MPa ultra-high pressure abrasive water cutting equipment integrated into the seabed. The key technologies of ultra-high pressure seawater pump working underwater and seawater lubricated bearing were discussed. The structure and control technology of abrasive mixing valve was analyzed. The cutting head device used together with ROV (remote operated vehicle) robot was also developed. Through the underwater cutting experiment simulated in pool and actual underwater cutting experiment on the seabed, the results shown that this equipment and parameter working conditions fully meet the requirements of sunken ship salvage engineering in deep-sea environment.
Development of Droplet Erosion Testing Facility
Authors: Anderson Keldon , Karimi Soroor , Shirazi Siamack
Published: September 2022

Liquid droplet erosion is a phenomenon that exists when liquid impacts a surface at a relatively high velocity that generates enough force to cause surface damage. This erosion has been ignored in early wind turbine designs due to their rotational speed being below the erosion threshold. However, the introduction to large-scale designs and offshore applications has shifted that focus. The knowledge of leading-edge protection has extended the lifespan of turbine operations by delaying the onset of damage caused by this erosion. Research into water droplet erosion is relatively new in comparison to other fields for erosion and turbine design. The goal of this paper is to develop an experimental facility to increase the available data for droplet erosion under standardized and repeatable conditions. The facility can test a variety of sample types at velocities up to 100 m/s in an artificial rain field. Testing will be conducted on metallic and non-metallic samples to measure mass loss caused by erosion. The facility is composed of cinderblock walls, a metal-framed roof, and a polycarbonate door for easy access and viewing of the test chamber. Rain field production is achieved via a peristaltic pump distributing water over ten needles that are mounted around the perimeter of the testing area. The needles are calibrated for flowrate and liquid droplet size produced for testing to match the desired rain intensity. Testing parameters include liquid type and conditions, droplet size and frequency, material type, rotation velocity, and specimen impact angle. Each specimen’s mass will be monitored to compare mass loss to the impact angle conditions. Test results will be compiled to generate a model for future erosion prediction and analysis for turbine material design and selection.
Improvement of the Clogging Behaviour of a Wastewater Impeller by the Use of an Inlet Guide Fin
Authors: Steffen Matthias , Thamsen Paul Uwe
Published: September 2022

The presented paper deals with the further development of a clogging-affine impeller with the support of optical high-speed video recordings. Development towards a “guide fin” for improved clogging behaviour is presented in 3 configurations. For configuration 1, functional tests are performed which failed at all operating points, even at light textile load. Evaluation of high-speed videos led to the conclusion that the hub shape is responsible for the initiation of a clogging process. To prevent this initiation, in configuration 2 the hub area is provided with a “guide stick” and a cone positioned on the axis of rotation which deflects incoming textiles to a larger diameter and thus away from the hub. The reperformed functional tests showed a significant improvement of clogging behaviour, especially with light and medium textile loads. However, reconsideration of the high-speed videos showed that the design of the guide stick is unsuitable for higher textile loads. This led to further development of the guide fin (configuration 3), whose reperformed functional tests revealed an impeller that was free of clogging in 11 of 12 test scenarios. It can be shown that the use of an optical access provides the possibility to identify and document the beginning of a clogging event in order to derive specific design modifications that can improve the clogging behaviour of a wastewater impeller.

The presented paper focusses on the clogging behaviour caused by the impeller. Further influencing factors, e.g. the volute, are not considered here.
Physics-Informed Long-Short Term Memory Neural Network Performance on Holloman High-Speed Test Track Sled Study
Authors: Pérez José , Baez Rafael , Terrazas Jose , Rodríguez Arturo , Villanueva Daniel , Fuentes Olac , Kumar Vinod , Paez Brandon , Cruz Abdiel
Published: September 2022

Physics Informed Neural Networks (PINNs) incorporate known physics equations into a network to reduce training time and increase accuracy. Traditional PINNs approaches are based on dense networks that do not consider the fact that simulations are a type of sequential data. Long-Short Term Memory (LSTM) networks are a modified version of Recurrent Neural Networks (RNNs) which are used to analyze sequential datasets. We propose a Physics Informed LSTM network that leverages the power of LSTMs for sequential datasets that also incorporates the governing physics equations of 2D incompressible Navier-Stokes fluid to analyze fluid flow around a stationary geometry resembling the water braking mechanism at the Holloman High-Speed Test Track. Currently, simulation data to analyze the fluid flow of the braking mechanism is generated through ANSYS and is costly, taking several days to generate a single simulation. By incorporating physics equations, our proposed Physics-Informed LSTM network was able to predict the last 20% of a simulation given the first 80% within a small margin of error in a shorter amount of time than a non-informed LSTM. This demonstrates the potential that physics-informed networks that leverage sequential information may have at speeding up computational fluid dynamics simulations and serves as a first step towards adapting PINNs for more advanced network architectures.
Atmospheric Turbulence Intermittency Effects on Remote Sensing Laser Propagation
Authors: Rodriguez Arturo , Gudimetla V. S. Rao , Adansi Richard , Terrazas Jose , Corral Vicente , Harris Christopher , Kumar Vinod , Baez Rafael , Paez Brandon
Published: September 2022

Scientists and researchers employed Gaussian media turbulence phase screens to find a clear view pocket in the fluid flow control space to enhance remote sensing capabilities, such as AFRL Maui Optical Supercomputing Site (AMOS), in the past two-decade. Some studies have found that fluid flow does not always behave in a Gaussian form; in atmospheric irregular fluid flow events, the turbulence exhibits intermittency. A recent study indicated that the intermittency in the fluid flow had correlated to the Fried parameter and generalized to a log-normal statistical distribution. Refractive Index Structure-Function is an essential parameter of interest to understand the intermittency in fluid flow phenomenon. Concluding that, to simulate phase screens with intermittency, the Refractive Index Structure Function must be changed depending on conditions for fluid flow intermittent data set, consequently changing the Fried Parameter to irregular behavior. Comparisons on this assumption will be addressed and implemented in this paper with new phase screens to enhance AMOS capabilities in intermittent events found in atmospheric turbulence. This study has compared advantages and disadvantages between generalizations and expensive numerical simulations to determine the tradeoffs between computational cost versus accuracy in numerical calculations of remote sensing laser propagation.
A CFD Study on the Effects of Sand Particle Size on Erosion of an Elbow
Authors: Haider Ghulam , Sedrez Thiana , Shirazi Siamack A.
Published: September 2022

During production operations from oil and gas condensate wells, sand particles also travel with the raw petroleum products. These sand particles impact the walls of transportation infrastructure and erode the wall thickness. This continuous degradation of wall thickness can result in leakages which has severe implications for production and safety. These sand particles can be of various sizes such as 300, 75, and 25 microns. Most of the studies on this phenomenon of solid-particle erosion focus on bigger particles such as 300-microns. Similarly, sand management techniques such as sand screens and gravel packs are used to control sand are specifically designed for bigger particles. However, recently the aging reservoirs are shedding small particles. These small particles can pass through these controls. Furthermore, small particles can block a portion of the sand screen, causing high velocities in other sections which can cause erosion of the sand screen openings allowing larger particles to pass through which in turn cause more erosion. Furthermore, these small particles are highly susceptible to turbulent regions of flow and can cause severe erosion in these regions. Hence, it is critically important to understand the effect of particle size on erosion behavior such as the location of maximum erosion, particle trajectories followed by various sized particles, and locations of maximum erosion. This study investigates the effect of particle size on erosion. Small particle erosion is more severe in gas-dominated multiphase flows such as annular and mist flows than liquid-dominated bubbly and slug flows. A 90-degree standard elbow is used in the analysis because of its high erosion vulnerability and its importance in pipeline applications. This is because the flow changes direction in this kind of geometry which has complex implications for erosion. Furthermore, the effects of particle size on erosion ratio and its distribution in pipe bends are discussed. The CFD results of larger particles agree better with experimental data than for smaller particles utilizing existing erosion models.
A Study of Second Moment Closure Modeling for Stratified Wakes Using DNS Ensembles
Authors: Jain Naman , Huang Xinyi , Yang Xiang , Kunz Robert
Published: September 2022

Buoyant wakes are widely encountered in ocean environment and undersea vehicle flows. These are typically characterized by high Reynolds (Re) and Froude (Fr) numbers, so turbulence resolving CFD models of such flows, i.e., Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES), require significant computational resources. Therefore, Reynolds-Averaged Navier-Stokes (RANS) based models are attractive for these configurations, but their performance hinges on numerous modeling assumptions. The inherently complex dynamics of stratified systems render eddy-viscosity-based modeling inappropriate. RANS Second-Moment Closure (SMC) based modeling is more suitable for such complex systems because they account for flow anisotropy by solving the transport equations of important second-moment terms. For stratified flows, turbulent density fluctuations and their auto- and velocity cross-correlations are dynamically important. Accordingly, at the SMC level of modeling, eleven transport equations are solved, and a range of sub-models are implemented for diffusion, pressure strain and scrambling, and dissipation, in the Reynolds stress, density flux, variance, and dissipation transport equations.

In this work, we study the stratified wakes of axisymmetric towed bodies using SMC and DNS. Sub-models in the SMC are evaluated in terms of how well their exact Reynolds averaged form impact the accuracy of the full RANS closure. An ensemble average of 100 DNS realizations is conducted to obtain converged higher-order statistics for direct comparison. For a stratified towed wake at Re = 10000 and Fr = 2, RANS successfully captures the peak mean defect velocity and wake width evolution when accurate initial conditions are provided from DNS. However, RANS over-predicts the wake height, and turbulent kinetic and potential energies, and exhibits larger amplitude oscillations and slower decay rates. Also, RANS predicts a near isotropic decay of normal Reynolds stresses in contrast to the anisotropic decay returned by DNS. The DNS data also provide important physics and modeling insights related to the inaccuracy of the dissipation rate isotropy assumption, and the non-negligible size of pressure-diffusion terms. These results lead to several important recommendations for SMC modeling improvement.
Clogging Behavior of Different Impeller Types of Sewage Pumps at Speed Variation
Authors: Müller Enrico , Pensler Thomas , Thamsen Paul Uwe
Published: September 2022

Nonwoven wet wipes are the most hazardous substances that cause clogging of sewage pumps, due to the increasing amount of wet wipes in sewer systems. The clogging of sewage pumps causes a considerable additional economic expense every year, which can be avoided by well-functioning sewage pumps. An additional problem to be considered is the reduced water consumption, which increases the concentration with the increased use of wet wipes in the wastewater. With demand-driven pumping of wastewater due to large diurnal fluctuations, pumps are speed-controlled as the price of frequency converters decreases.

The current advice when speed variation in wastewater pumps are used, affects the minimum velocity in the pipes. The study investigates how speed influences the clogging phenomena of wastewater pumps. The pumps have been approved at a test stand in a laboratory that is designed for functional tests on wastewater pumps. During the test the operating behavior is logged and indicates how clogging influences the pumping performance. Those tests have been done for a long-time performance test, in which the wastewater is pumped in a loop for 60 Minutes.

During the test procedure the clogging is observed with a high speed camera, so that the clogging on the impeller can be visualized. This helps to understand the clogging and self-cleaning ability of impellers better. The behavior of the susceptibility to clogging of the wastewater pumps was very different. The type of impeller as well the speed are the most influencing characteristics that influence clogging.
CFD Simulation of Hurricane Force Wind and Its Impacts on Residential Buildings
Authors: Siaka Ghalib , Zhang Ning
Published: September 2022

The landfall of hurricane Laura and Delta during the 2020 hurricane season cost the Southwest Louisiana Area (SWLA) $19 billion and $2.9 billion in damage respectively. Since then, the need to use computational fluid dynamics to study hurricane effects on buildings to reduce damage costs is more alarming. In this research, common residential building designs will be put under different levels of hurricane size winds and barometric pressure conditions from different directions through CFD simulations. The effect of the roof shape, size, and placement on the pressure, shear stress, and eddies acting on the roof will be studied since they are the major causes of roof damage on a building during a hurricane. The objective of this research is to identify the areas of a building’s roof most vulnerable to damage during a hurricane, to ensure reinforcements to prevent future damage. Higher category hurricanes are more likely to cause roof damage due to the lower barometric pressure and higher Reynold’s number characteristics the possess. In the CFD simulation, a Steady and Unsteady Reynolds Averaged Navier-Stokes (RANS) turbulence model will be used. Also, a Large Eddy Simulation (LES) turbulence model will be used to study the flow structure in the domain.
Effect of Microfiber Length on Microfiber Motion in Human Nasal Airways
Authors: Li J. , Ma J. , Tu J. Y. , Tian L. , Ahmadi G.
Published: September 2022

Respiratory inhalation of elongated mineral particles has been a significant concern for humans due to the adverse health consequences. In recent years, the increased usage of carbon nanofiber and carbon nanotubes in high-performance engineered materials has raised renewed concerns. However, studies on this subject are still limited, and many aspects of the respiratory deposition of elongated microfibers are not fully understood. In this study, simulations of the transport and deposition of elongated microfibers in a realistic human nasal cavity model were performed. A constant breathing rate of 15 L/min under laminar flow conditions was assumed, and the airflow field was evaluated using the ANSYS FLUENT™ 19.2. Motions of the elongated ellipsoid were simulated using the coupled translational and rotational governing equations, accounting for the hydrodynamic drag and torque, shear-induced lift, and gravitational sedimentation utilizing an in-house microfiber code incorporated in the ANSYS FLUENT™ UDF (user Defined Function). Sample single microfiber trajectories were presented and analyzed to provide insight into their motions. In addition, the microfiber deposition due to microfiber lengths, rotation, and interaction with the local flow stream, were investigated.
Fluid Velocity Sensing at Extreme Altitude or Low Density Environments
Authors: Papadopoulos George , Bivolaru Daniel , Murphy Andrew , Siu Spencer
Published: September 2022

Methods to measure wind speed and direction range from simple hot-wire / hot-film anemometers to sophisticated sonic and laser/image-based instrumentation. While these can work well on the ground and to low altitudes, there are challenges in implementation for high altitude measurements at the 20 km and above range, where a near space environment exists. The low pressure, low density environment does not support the conditions needed for all known measurement methods to generate an engineering value for the full velocity vector at the cm/s accuracy and resolution needed to allow for high altitude balloon or platform trajectory correction. The National Oceanic and Atmospheric Administration (NOAA) regularly reports relative wind conditions to the 60 kft (18 km) level. Above this level operators are left to modeling and simulation of the stratified air to determine prevailing wind conditions that can be used to provide trajectory control via altitude changes. An in-situ, on-board sensor that can measure all three components of velocity with resolution and accuracy in the cm/s range can take out the uncertainty that is involved in the software-based approach, and together with other navigation aids, complete a trajectory solution for high altitude platforms and science balloons that will help them extend their mission envelope to greatly benefit operational effectiveness. The development of a novel wind speed sensor solution that can operate at the high altitudes of interest and meet resolution requirements is described. The sensor solution can also be applied in other low density environments to measure flow velocity, as well as, harsh environments that may be challenging for other velocity measurement methods. The paper also includes discussion on the design and fabrication of a special high altitude closed vessel with an integrated wind tunnel, capable of generating wind at altitudes more than 45 km, used in the current project for experimental validation, but could also support future sensor calibration efforts.
A Micro-Scale Computational Investigation on the Effects of Leaf Hair on PM2.5 Deposition
Authors: Boontanom Jedhathai (Vicky) , Tafti Danesh K.
Published: September 2022

According to the United Nations, 55% of the world’s population currently lives in urban areas and which is projected to increase to 67% by 2050. Trees and green spaces are effective strategies for mitigating urban pollution. This study develops a framework to investigate the impact of trichome morphology and wind speed on the deposition of 0.3 μm and 1.0 μm particles at the micro-scale. Representative trichome diameters, D = 5 and 20 μm are investigated by varying their height, H, between 100 to 600 μm with packing density of 5 and 15 mm−2. The results show that trichome diameter, density, and wind speed have a favorable impact on deposition velocity. Compared to a smooth leaf, the presence of the thicker 20 μm hairs increases the deposition velocity by 1.5–4 times, whereas, the presence of short 5 μm trichomes reduces the deposition by 15–45%. Increasing trichome height to diameter ratio from H/D = 20 to 30 shows benefits for the thinner trichomes but lowers the deposition for the densely packed thicker trichomes. Less aerosol deposition is also observed when the particle diameter increases from 0.3 μm to 1.0 μm. Within the scope of this study, the complex interplay between these various traits, is captured via a non-dimensional ratio Rhp to model the aerosol deposition on the leaf surface. The results offer valuable insight into the effects of trichome morphology on pollutant deposition in isolation from other environmental and macro-factors.
Is it Turbulent or Laminar? Convolutional Neural Network Predictions
Authors: Dudu Nicholas , Rodriguez Arturo , Kotteda V. M. Krushnarao , Terrazas Jose , Villanueva Daniel , Chijioke Clinton , Baez Rafael , Paez Brandon , Kumar Vinod
Published: September 2022

Laminar flow has been characterized for its smooth and linear behavior concerning its flow. When a non-linearity is introduced, the flow becomes turbulent. Visually it is possible to distinguish between laminar and turbulent flow by identifying areas in the flow that become chaotic or non-smooth. We used a Convolutional Neural Network (CNN) trained on labeled laminar and turbulent images to automate the process. This form of machine learning is called supervised machine learning. The training data set is labeled for the neural network to identify distinguishing parameters that make them different. In this study, we take simulated contours from a flow past cylinder simulation, train it, and test it to see how effective the CNN is at distinguishing between the laminar and turbulent flow.
Shock System Dynamics of a Morphing Bump Over a Flat Plate
Authors: Hamada Ahmed A. , Margha Lubna , AbdelRahman Mohamed M. , Guaily Amr
Published: September 2022

The shock wave boundary layer interaction (SW-BLI) phenomenon over transonic and supersonic airfoils captured the attention of aerospace engineers, due to its disastrous effect on the aerodynamic performance of these vehicles. Thus, the scientific community numerically and experimentally investigated several active and passive flow control elements to reduce the effect of the phenomenon, such as vortex generator, cavity, and bump. They focused on designing and optimizing the shape and location of the bump control element. However, the transit movement of the bump from the state of a clean airfoil to the state of an airfoil with a bump needs more investigation, especially the dynamics of the shock system. Thus, it is preferred to start with simple geometry, such as a flat plate, to fully understand the flow behavior with a morphing bump. In this paper, the shock dynamics due to the movement of a bump over a flat plate flying at supersonic speed are numerically investigated. The bump is located at the impingement position of the shock wave and is moved at different speeds. This study determines the suitable speed that achieves the minimum entropy change, which is the representation parameter of the transition period. The two-dimensional unsteady Navier-Stokes equations are solved using OpenFOAM to simulate the flow field variables, while the motion of the bump is tracked using the Arbitrary Lagrangian-Eulerian (ALE) technique. The results show that a spatial lag on the shock system from the steady-state solution occurs due to the movement of the bump. Further, the spatial lag increases with the increase in the bump’s speed. This causes a high increase in the flow parameters and consequently the total entropy changes on the bump surface. Generally, it is common to move the bump over the longest possible time to approximate a quasi-steady flow during the motion. However, this causes a deviation in the flow parameters between the final time of transition and the steady-state case of bump existence. Thus, it is concluded that the optimal non-dimensional time for a morphing bump in a supersonic flow of Mach number of 2.9 is 2, which is different than the longest time of 10.
Study of Couette-Taylor-Poiseuille Flow With a Wavy Internal Cylinder Surface at Low Taylor and Axial Reynolds Numbers
Authors: Gaied Lamia , Berrich Emna , Aloui Fethi
Published: September 2022

The flow models of a Taylor-Couette-Poiseuille flow with a wavy interior surface have been studied at low axial Reynolds numbers (Reax less than or equal to 32) and Taylor numbers (Ta less than or equal to 606). Two types of surfaces were operated; smooth and wavy. The surface of the wavy cylinder has 18 identical axial waves, which are arranged periodically. The Taylor-Couette system is characterized by an average inner and outer cylinder radius ratio of 0.9, an average gap between the two concentric cylinders of 10mm and an aspect ratio equal to 45, corresponding to the dimensionless height of these cylinders.

The spatiotemporal flow representation was provided quantitatively and qualitatively by exploiting flow visualizations and simultaneous measurements of the components of the wall shear rate. An axial flow imposed on the base flow not only modifies the conditions for the appearance of instabilities, but also the vortex structure of vortices. It can have a stabilizing effect for a regime flow and a destabilizing effect for another, i.e., the transition to Taylor vortices occurred at higher or lower Taylor numbers. In such destabilizing cases, the vortices are either folded or stretched or overlapped or completely destructed.

As a function of the axial Reynolds and Taylor numbers, helices appear, develop and wind in the same direction as the base flow or in the opposite direction. It has been observed that the shear stress of the wall strongly depends on the nature of the surface in contact with the flow, on Ta and Re.
Phototactic Behavior of Micro-Swimmers: Light Effects on Cell Swimming in Oscillating Flow
Authors: Pashmi Elnaz , Peerhossaini Hassan , Jarrahi Mojtaba
Published: September 2022

In this investigation, the phototactic behavior of the swimmer alga Chlamydomonas reinhardtii was studied in oscillatory flows. Two light-emitting diodes (LED) were placed next to one of the lateral walls of a long PDMS microchannel of rectangular cross-section (width = 500 μm, height = 85 μm) which was enclosed in a dark box. Oscillating flow of algal suspension was generated using a pressure-driven control system. Both low and high concentrations of the cells were considered. The short- and long-term effects of light exposure on the cells swimming, and the influence of amplitude and frequency of flow oscillation in the presence of light stimulus were determined.

It was shown that if the period of flow oscillation is shorter than the response time of the cells to a light stimulus (about 1 second), the cells cannot react immediately to the light and thus, the increase in the percentage of cells population showing a negative phototaxis (Nup) occurs later compared to the cases where the oscillation period is long enough (low frequencies). Moreover, it was shown that a smaller oscillation amplitude results in a sharper and earlier increase in Nup since the cells are less affected by the flow advection and respond more efficiently to the light stimulus.

Regarding the long-term effects of light exposure, it was shown that the phototactic behavior of the cells is a function of time, in both low and high concentrated suspensions; however, this evolution with time depends on the concentration. Over a cycle of light exposure on the dilute suspensions, Nup increases in the beginning of the cycle until reaching a peak; then it decreases to the initial value indicating that the effect of light is no longer perceptible by the cells.
Numerical Simulation on Application of Airfoil Cross-Section Rod of Pantograph
Authors: Zhang Mohan , Yin Bo , Yang Guowei
Published: September 2022

Pantograph is a kind of structure composed of many rods parts. Due to its complex structure, the drag of pantograph is relatively high in the drag of the whole high speed train. In order to reduce the aerodynamic drag, many scholars put forward methods such as adding a deflector and installing a baffle plate on the roof of the train, but these methods have little effect on improving the lift force of the pantograph. Regarding this situation, this paper applies airfoil section (naca0012) to the panhead section of the pantograph strips. Knuckle-downstream and knuckle-upstream operating conditions with three running speeds (300km/h, 350km/h and 400km/h) are considered. The drag and lift forces are compared with those of regular pantograph strip in order to confirm the improvement of aerodynamic performance. It indicated that the optimized panhead pantograph has a better performance in drag and lift forces under all the conditions except the lift force rises 14 percent at knuckle-upstream.