bluuebunny/crossref_metadata_2025 huggingface dataset:
Scientific and Technological Development in Russia Under Sanctions Pressure
Authors:   Institute of Economics RAS, Lenchuk E.B.
Published: September 2022

The article analyzes the limitations of scientific and technological development in Russia, arising under the sanctions pressure of Western countries. Particular attention is focused on the challenges that are created by the introduced technological restrictions in the research and development, scientific and technical cooperation, access to sources of scientific information, which create obstacles both for solving the problems of import substitution and for developing science at a competitive level. In this regard, the need for technological mobilization in Russia and the development of an appropriate scientific and technological policy are substantiated. A system of measures has been proposed to counteract sanctions pressure and build a further vector of development in the scientific and technological sphere and link it with the development of the real sector of the economy.
Reflectivity of Venus’s Dayside Disk During the 2020 Observation Campaign: Outcomes and Future Perspectives
Authors: Lee Yeon Joo , Muñoz Antonio García , Yamazaki Atsushi , Quémerais Eric , Mottola Stefano , Hellmich Stephan , Granzer Thomas , Bergond Gilles , Roth Martin , Gallego-Cano Eulalia , Chaufray Jean-Yves , Robidel Rozenn , Murakami Go , Masunaga Kei , Kaplan Murat , Erece Orhan , Hueso Ricardo , Kabáth Petr , Špoková Magdaléna , Sánchez-Lavega Agustín , Kim Myung-Jin , Mangano Valeria , Jessup Kandis-Lea , Widemann Thomas , Sugiyama Ko-ichiro , Watanabe Shigeto , Yamada Manabu , Satoh Takehiko , Nakamura Masato , Imai Masataka , Cabrera Juan
Published: September 2022

We performed a unique Venus observation campaign to measure the disk brightness of Venus over a broad range of wavelengths in 2020 August and September. The primary goal of the campaign was to investigate the absorption properties of the unknown absorber in the clouds. The secondary goal was to extract a disk mean SO2 gas abundance, whose absorption spectral feature is entangled with that of the unknown absorber at ultraviolet wavelengths. A total of three spacecraft and six ground-based telescopes participated in this campaign, covering the 52–1700 nm wavelength range. After careful evaluation of the observational data, we focused on the data sets acquired by four facilities. We accomplished our primary goal by analyzing the reflectivity spectrum of the Venus disk over the 283–800 nm wavelengths. Considerable absorption is present in the 350–450 nm range, for which we retrieved the corresponding optical depth of the unknown absorber. The result shows the consistent wavelength dependence of the relative optical depth with that at low latitudes, during the Venus flyby by MESSENGER in 2007, which was expected because the overall disk reflectivity is dominated by low latitudes. Last, we summarize the experience that we obtained during this first campaign, which should enable us to accomplish our second goal in future campaigns.
Beneficial effects of vitamin D in the management of untreated hyperlipidemia in diabetic patients in Erbil, Iraq
Authors: Khoshnaw Mohammed , Dizaye Kawa
Published: September 2022

Hyperlipidemia is highly prevalent among type 2 diabetes mellitus (T2DM) patients. As hyperlipidemia plays a major part in atherosclerosis development and progression, this occurrence is linked to a significantly raised risk of cardiovascular disease. This study aims to assess the effects of vitamin D supplementation on lipid parameters in T2DM patients with untreated hyperlipidemia. Thirty-five T2DM patients with hyperlipidemia and vitamin D deficiency were supplemented with vitamin D for three months. Serum 25-hydroxyvitamin D (25[OH]D), calcium, lipid parameters, atherogenic indices, glucose, and HbA1c were recorded before and after the intervention. After supplementation, there was a statistically significant reduction in VLDL-C and triglycerides. Triglycerides showed a significant negative correlation with 25(OH)D. Atherogenic indices and HDL-C also improved significantly. Vitamin D supplementation had beneficial effects on the lipid profile of T2DM patients with untreated hyperlipidemia and vitamin D deficiency. Thus, vitamin D could be a valuable adjuvant therapy for these patients.
Investigating the impact of gender-differences and spatial ability on learning from instructional animations
Authors: Gupta Ruchi , Marcus Nadine , Ayres Paul
Published: September 2022

Cette étude est consacrée à deux facteurs (genre ; habileté spatiale), dont la prise en compte pourrait expliquer les résultats mitigés souvent obtenus dans les recherches sur les animations pédagogiques. L’étude a comparé l’efficacité des animations pédagogiques sur les apprentissages en comparant trois conditions (animation ; animation + explication orale ; animation + gestuelle). 72 étudiants ont été assignés de manière aléatoire à l’une des trois conditions. L’animation montrait comment réaliser un pliage sur papier. Dans l’ensemble, la condition avec explication orale s’est avérée supérieure à la condition de gestuelle, qui était à elle-même supérieure à la condition d’animation toute seule. Cependant, ce résultat a été obtenu uniquement avec des femmes. Chez les hommes, aucune différence significative n’a été constatée entre les conditions. En outre, les femmes ont obtenu des scores plus élevés que les hommes, même s’il n’y avait pas de différences d’habileté spatiale. Une mesure appropriée de l’habileté spatiale, en tant que covariable, s’est avérée nécessaire pour identifier tous les effets. Si les données relatives au genre et à l’aptitude spatiale avaient été exclues des analyses, les résultats auraient été trompeurs et incomplets.
Evaluating the nonlinear relationship between nonfinancial corporate sector leverage and financial stability in the post crisis era
Authors: Du Ziqing , Li Yaru , Lv Guangming
Published: September 2022

This paper analyzes the relationship between the nonfinancial corporate sector leverage (NFCL) and financial stability in the post crisis era, revealing considerable heterogeneity across the level of financial intermediation (FI). First, we use the financial soundness indicators proposed by the IMF and the generalized dynamic factor model (GDFM) to measure the financial stability represented by the FSI of OECD countries. Second, in a panel quantile regression framework, we examine the effects of NFCL on FSI for different quantiles of FSI. The result shows that the impact of NFCL on financial stability at different levels is asymmetric, which reflects differences in the supply and demand of debt. Third, this paper further discusses the transmission mechanism of FI between NFCL and FSI based on the panel smooth transition regression model (PSTR). We find that the transmission channel of NFCL to financial stability depends on the level of financial intermediation, but with diverging magnitude for the different levels of FI.
Time-sequential graph adversarial learning for brain modularity community detection
Authors: Gong Changwei , Xue Bing , Jing Changhong , He Chun-Hui , Wu Guo-Cheng , Lei Baiying , Wang Shuqiang
Published: September 2022

Brain community detection is an efficient method to represent the communities of brain networks. However, time-variable functions of the brain and the intricate brain community structure impose a great challenge on it. In this paper, a time-sequential graph adversarial learning (TGAL) framework is proposed to detect brain communities and characterize the structure of communities from brain networks. In the framework, a novel time-sequential graph neural network is designed as an encoder to extract efficient graph representations by spatio-temporal attention mechanism. Since it is difficult to capture the community structure, the measurable modularity loss is used to optimize by maximizing the modularity of the community. In addition, the framework employs an adversarial scheme to guide the learning of representation. The effectiveness of our model is shown through experiments on the real-world brain network datasets, and the great performance of brain community detection demonstrates the advantage of the proposed framework.
SPREAD: An ensemble predictor based on DNA autoencoder framework for discriminating promoters in Pseudomonas aeruginosa
Authors: Zhou Shengming , Zheng Jia , Jia Cangzhi
Published: September 2022

Regulatory elements in DNA sequences, such as promoters, enhancers, terminators and so on, are essential for gene expression in physiological and pathological processes. A promoter is the specific DNA sequence that is located upstream of the coding gene and acts as the "switch" for gene transcriptional regulation. Lots of promoter predictors have been developed for different bacterial species, but only a few are designed for Pseudomonas aeruginosa, a widespread Gram-negative conditional pathogen in nature. In this work, an ensemble model named SPREAD is proposed for the recognition of promoters in Pseudomonas aeruginosa. In SPREAD, the DNA sequence autoencoder model LSTM is employed to extract potential sequence information, and the mean output probability value of CNN and RF is applied as the final prediction. Compared with G4PromFinder, the only state-of-the-art classifier for promoters in Pseudomonas aeruginosa, SPREAD improves the prediction performance significantly, with an accuracy of 0.98, recall of 0.98, precision of 0.98, specificity of 0.97 and F1-score of 0.98.
The Added Value of Integrating the Electronics Workbench Simulator in the Teaching of Electrical Concepts to Moroccan High School Students
Authors: Hamamous Adil , Benjelloun Nadia
Published: September 2022

In this paper, we are interested in the study of the use of the Electronics Workbench (EWB) simulator in the study of amplitude modulation and demodulation. We conducted a study with 50 Moroccan students in the second year of the scientific baccalaureate option physical sciences at the high school Abdellah Laroui of the city of Fez. Using the pre-test and post-test methodology with an experimental group (25 students) and a control group (25 students). The results of the two groups are analyzed using the student t-test. The results obtained in the post-test show that the average of the test administered to both groups, control (MG-Con) and experimental (MG-Exp), found a non-significant difference (MG-Exp - MG-Con = 15,36- 15,08 = 0,28 > 0. In addition, using interviews, we asked students and teachers to give their opinions on questions about the use of the Electronics Workbench (EWB) simulator in learning. The results obtained show that the laboratory experiments cannot replace the simulator (EWB) which can be used as an alternative pedagogical means to help students understand the concepts in electricity.
Applying Deep Learning and Computer Vision Techniques for an e-Sport and Smart Coaching System Using a Multiview Dataset: Case of Shotokan Karate
Authors: Ait-Bennacer Fatima-Ezzahra , Aaroud Abdessadek , Akodadi Khalid , Cherradi Bouchaib
Published: September 2022

Smart coaching and e-sport platforms have shown a great interest in the recent research studies. Through this study, we aim to globalize the practice of sport, especially Shotokan Karate, by connecting participants and coaches on an international scale through the integration of Artificial Intelligence techniques such as computer vision and deep learning, to give the possibility of carrying out national and international virtual training courses without logistical constraints. The proposed work aims to apply the latest action detection, action recognition, and action classification methods for different Karate movements using the LSTM and the ST-GCN algorithms and proposes these movements in 3D using Video Inference for Human Body Pose and Shape Estimation (VIBE). Our proper Multiview Dataset contains pose estimations of a set of basic movements captured by a karate Shotokan expert (6th DAN Black Belt) from three views (Front view, Left view, and Right view) using OpenPose and FastPose for human body keypoint detection. The current study sets out to detect, recognize, classify and score different participants' movements. We achieved greater than 96% recognition accuracy of this dataset using the LSTM algorithm, and 91.01% using the ST-GCN algorithm.
Formation of Programming Skills among Students of Scientific, Technical and Natural Science Areas of Training Using the Arduino Platform
Authors: Ďuriš Viliam , Vasileva Lidia , Chumarov Sergey , Lengyelfalusy Tomáš
Published: September 2022

The problem of improving the educational process of students of scientific, technical and natural science areas of training is one of the relevant aspects of modern pedagogical research. During training, it is necessary to apply new approaches, educational technologies and techniques in order to prepare graduates who are able to independently solve complex scientific, technical and engineering design tasks in the process of modern production. Programming is a universal tool for modeling objects and processes, as well as a powerful tool in developing the thinking of students of scientific, technical and natural science fields of training. The article discusses the issues of formation of programming skills of students based on the use of the Arduino platform. The professional standards are analyzed, the main contradictions of the existing system of training future bachelors in the field of radio electronics and control systems are revealed. The method of organizing effective programming training based on the use of the Arduino platform is presented. The criteria and indicators of the levels of competence formation are given. The results of an experiment on the implementation of the described methodology of teaching programming on the basis of the I.N. Ulyanov Chuvash State University are shown. Using the chi-square criterion, statistical processing of the results of a pedagogical experiment was performed, which convincingly proves that when using the Arduino platform, most students have reached high and advanced levels of programming skills formation.
Status Natural Compounds of Medicinal Plants, Herbs, and Spices
Authors: Butnariu Monica , Sharifi-Rad Javad
Published: September 2022

All life forms, including medicinal plants and herbs and spices (MPHSs), which are now known, are based on common natural organic compounds (NOCs) with similar biochemical properties. It has not been practically demonstrated that there is an alternative for obtaining the products of catabolism and anabolism reactions specific to biochemical metabolism. MPHSs produce an amazing variety of NOCs other than the known components of the main metabolism. Secondary compounds (SMs) are derived from the main classes, but are not essential for metabolism, hence their name as secondary or intermediate compounds of metabolism. They are NOCs that are not directly involved in the growth, development, or reproduction of organisms. Unlike primary metabolites, the lack of SMs does not lead to immediate death but rather to long-term impairment of the body, to the lack of more aesthetic properties, without any significant change in metabolism.
A Contribution of Spectrophotometric Methods to Medicinal Plant Taxonomy
Authors: Koçyiğit Mine , Geçimli Fethi , Bicak Bilge , Vatandaşlar Özge , Gunduz Serda Kecel
Published: September 2022

Plant taxonomy is the science that finds, identifies, describes, classifies, and names plants. It is one of the main branches of taxonomy (the science that finds, describes, classifies, and names living things). Plant taxonomy is closely allied to plant systematics, and there is no sharp boundary between the two. In practice, “plant systematics” involves relationships between plants and their evolution, especially at the higher levels, whereas “plant taxonomy” deals with the actual handling of plant specimens. The precise relationship between taxonomy and systematics, however, has changed along with the goals and methods employed. Many different methods are used in plant taxonomy. Morphological, anatomical, karyological, palynological, chemo-taxonomical, and molecular methods are used especially in medicinal plant taxonomy today. Spectrophotometric methods have just begun to be used in medicinal plant taxonomy. It is one of the most practical methods that can be used to reveal the differences among species without wasting time and money.
Numerical Analysis of Rotor Aeroacoustic Scattering Characteristics Considering Fuselage Aerodynamic Configuration Parameters
Authors:   Nanjing University of Aeronautics and Astronautics, Bao Weicheng , Chen Xi , Sun Dazhi , Zhao Qijun , Sun Dazgu
Published: September 2022

Based on the FW-H equations, the CFD method and the time domain equivalent source method (TDSEM), the rotor aeroacousitc scattering characteristics considering the fuselage aerodynamic configuration parameters are calculated and analyzed. First, a set of CFD/FW-H/TDESM hybrid analysis method for rotor/fuselage aeroacoustic characteristics is developed. The aeroacoustic characteristics of the UH-1H rotor in hover and a point acoustic source nearby a rigid sphere are calculated, and the employed numerical analysis method is validated through comparisons with reference data. Then, the aeroacoustic characteristics of the Bo-105 in hover (main rotor/fuselage) are analyzed, and the scattered noise is discussed in detail. Finally, the aeroacoustic characteristics of the AH-64 helicopter in forward flight is calculated. In addition, parameters, such as the distance between fuselage and rotor, are quantified, and some conclusions are obtained. The fuselage will influence the directivity of rotor noise, and an appropriate fuselage configuration will reduce the rotor noise at the azimuth of 250 degrees (1dB in the present case).
Trailing-Edge Noise Predictions of Rotorcraft Airfoils
Authors:   University of California Davis, Gill Hyunjune , Lee Seongkyu
Published: September 2022

This paper presents the effect of rotorcraft airfoils on turbulent boundary layer trailing-edge noise. Among the numerous airfoils available for rotocraft application, a total of eleven commonly used airfoils are selected and divided in three groups, and their corresponding trailing-edge noise is investigated. The compressible Reynolds Averaged Navier-Stokes (RANS) CFD simulation coupled with a semi-empirical wall pressure spectrum model and a physics-based far-field noise prediction theory is used to predict noise levels at varying angles of attack. In this paper, the CFD tools and the noise prediction model are first validated, and then the trailing-edge noise analyses for the eleven airfoils under the same compressible flow condition are presented. It is found that NACA 0012, VR-12, and SC-1094 R8 airfoils show low trailing-edge noise levels compared to other similar airfoils in each group. The noise characteristics from airfoils like NACA 0012 shows clear separation in the frequency range where the noise from the suction or pressure side is dominant at low and high frequencies, respectively. However, airfoils like VR-12 shows that the suction-side trailing-edge noise can still be important at high frequency at small angles of attack, thus producing a combined effect from both suction and pressure sides. Furthermore, a natural laminar flow airfoil is considered to investigate how the trailing-edge noise responds to the delayed transition locations. It is observed that the delayed transition locations reduce the low- and high frequency noise at a higher angle of attack.
Ground-based Acoustic Measurements of Small Multirotor Aircraft
Authors:   Pennsylvania State University, Konzel Nicholas , Greenwood Eric
Published: September 2022

Experimental procedures are developed for the measurement and characterization of noise from small multirotor aircraft. These procedures are applied to measure the noise of the Tarot X8. The acoustic characteristics of the Tarot X8 are evaluated for a number of level flight flyover conditions. Both tonal and broadband noise is found to be significant, but the relative importance depends on the angle of observation. Variability in noise is assessed both across repeated runs of the same condition and within a run using an array of microphones parallel to the flight track. Variability is found to increase as the distance between the microphone and aircraft increases. Variations within a run are significant (on the order of 2 dBA), but do not explain the greater variation (on the order of 5 dBA) in levels between runs.
Flyover Noise Comparison Between Joby Aircraft and Similar Aircraft
Authors:   Joby Aviation, Bain Jeremy , Goetchius Greg , Josephson David
Published: September 2022

Joby Aviation is developing a six propeller, all electric vertical takeoff and landing piloted air taxi aircraft. The aircraft is designed for high density operations near residences and workplaces, so it is imperative that the acoustic emissions of the aircraft are minimized for community acceptance. It is important to compare not just the absolute sound levels but also the sound quality with conventional aircraft already known to the public. To showcase the difference between the Joby aircraft and similarly sized aircraft for a level flyover condition, Joby arranged a flight demonstration with two conventional fixed-wing aircraft and three commercial helicopters. All the aircraft were flown at approximately 100 knots (51 m/s) and 1500 feet (457 m) above ground level within minutes of each other in the same location to minimize variability. They were measured with the same equipment and processing methods. The results show that the peak Joby aircraft sound pressure level was 10 to 19 dB(A) below the conventional aircraft. The conventional aircraft noise levels were above the peak Joby level for 43 to 54 seconds during the flyover. The Joby aircraft was measured at 13 to 22 EPNdB lower than the conventional aircraft. Close examination of the spectra showed that Joby aircraft has greatly reduced tonal and low frequency content. When substituting the low ambient noise during the flight test with a realistic urban outdoor cafe environment, the Joby aircraft is below the ambient at all frequencies during the direct f lyover which allows it to blend in with the ambient soundscape. The other conventional airplanes and helicopters exhibited large tones that rise above the cafe ambient for approximately one minute, and would impact a much larger area on the ground that is not directly under the flight path.
High Solidity, Low Tip-Speed Rotors for Reduced eVTOL Tonal Noise
Authors:   Rensselaer Polytechnic Institute, Gandhi Farhan , Pepe Justin , Smith Brendan
Published: September 2022

This paper reports on a computational study conducted on an 8 ft diameter, fixed-pitch eVTOL rotor to examine the potential of using increased solidity and reduced tip speed to reduce the radiated acoustic signature. The study is conducted for the rotor operating in hover and in vertical climb, and at disk loadings between 6-12 lb/ft2. Relative to a "nominal" rotor of solidity σ=0.0646 (with N=2 blades and a root chord, c=15.82 cm), two 3σ rotors (the 3σ3 rotor with N=3 and root chord of 2c, and the 3σ5 rotor with N=5 and root chord of 1.2c) operating at reduced tip speed are considered, as is a single 5σ rotor (with N=5 and root chord of 2c) operating at a further reduced tip speed. The high solidity, low tip-speed rotors showed significant reductions in in-plane noise, both in hover as well as vertical climb, and over the range of disk loadings considered. The noise reductions observed with the 3σ5 rotor were significantly greater than those obtained by the 3σ3 rotor (operating at the same tip speed), and very similar to those of the 5σ rotor (operating at a lower tip speed). But the rotor torque and power penalty for the 3σ5 rotor was considerably lower than that for the 5σ rotor. Overall, a high solidity in the range of 0.2 for eVTOL rotors is quite advantageous, but further increase to around 0.3 appears acoustically unnecessary while being aerodynamically detrimental. At a solidity of 3σ, going from 3 wider chord blades to 5 narrower chord blades was hugely influential for in-plane noise reduction. Of the configurations studied, the best (the 3σ5 rotor) showed 16-24 dB reductions in in-plane noise in hover, reducing to 14.5-20 dB at 5/ms climb rate, and 12.5-16 dB at 10 m/s climb rate, with larger reductions seen at lower disk loadings. Relative to the solidity-σ rotor, the 3σ rotors had a torque penalty of 41-44%, and power penalties ranging from 1.5-5% in hover, increasing to 7.5-10% at 10 m/s climb rate.
Transition Performance Of Tilt Propeller Aircraft
Authors:   Joby Aviation, Stoll Alex , Milkic Gregor
Published: September 2022

A simple model of the transition aerodynamics of Joby Aviation's electric tilt-propeller VTOL aircraft was developed by combining a surrogate model of CFD propeller solutions with semi-empirical models of airframe aerodynamics and interactional aerodynamics. The model was calibrated to match CFD results of the entire aircraft, as well as f light test results of the actual aircraft. Using this model, loads and power requirements across the range of shaft tilt angle and airspeed combinations for trimmed flight -- the "conversion corridor" often described in tiltrotor performance reports -- are analyzed, and resulting performance limitations are discussed. Additionally, a novel approach to transition flight is introduced in which the angle of attack and shaft angle are automatically determined by the flight controller, rather than manually controlled. Using the simple transition aerodynamics model, transition loads and power requirements with this control approach are discussed, and transition flight using this control approach is shown to allow for high performance given reasonable limitations.
Hoverfoil™ Design and Testing
Authors:   Levanta Tech LLC, Echols Kelly , Petersen Randall
Published: September 2022

The Hoverfoil™ is an engineered wing-in-ground effect airfoil that can maintain lift while at zero forward velocity. This is done by use of internally routed duct work that channels airflow through the airfoil to the underside, to create an area of high pressure on the bottom of the Hoverfoil™. The airfoil shape (excluding ductwork) utilized a NACA 8308 airfoil. A combination of computational fluid dynamic (CFD) models and 3D scale prototyping have been used to study the feasibility of the project. The CFD model has proven the initial idea as feasible, however the implementation of the scale prototype needs to overcome some barriers to complete testing.
Benefits of Dual Propellers for a Coaxial Helicopter
Authors:   Rensselaer Polytechnic Institute, Stillman Alexander , McKay Michael , Gandhi Farhan
Published: September 2022

A model of a coaxial helicopter with a rigid rotor system is modified to have dual side-mounted propellers. The aircraft is simulated in trim at different flight speeds to investigate the potential benefits of the dual propellers with regard to fault tolerance and yaw control authority. At low speed, the dual propellers impact on the main rotor system actuator failure ranges is analyzed, demonstrating an increase in the allowable trim range from 25-30% in the nominal platform to 50-60% with the dual propeller configuration. Relaxation of the stall constraint for the dual propellers expands the upper rotor maximum actuator limits to the maximum geometric limit, minimum actuator limits for the lower rotor are constrained by the upper rotor stall limits. Upper rotor minimum and lower rotor maximum actuator limits are determined by tip clearance restrictions. At mid speed, the dual propellers improve the yaw control power in the 50-100 kt range and allow for a Level 1 aggressive yaw response as defined in ADS-33E. At high speed, the dual propellers provide yaw control redundancy and allow for trim when the rudder is fully deflected for nearly the entire f light envelope.
Effects of Active Flow Control on Fan-In-Wing Aerodynamic Performance In Hover and Forward Flight
Authors:   University of Toledo, Sheng Chunhua , Zhao Qiuying
Published: September 2022

Aerodynamic performance of a fan-in-wing configuration in hover and forward flight is further investigated using an active flow control technique. The previous investigation has demonstrated the efficacy of active flow control to improve the aerodynamic performance of fan-in-wing device operating at a fixed rotational frequency. In the present study, the fan-in-wing device is numerically investigated at a fixed fan pitch angle operating at a series of rotational frequencies under two free stream conditions, one representing the device in hover (zero free stream velocity) and another representing the device in forward flight condition (non-zero free stream velocity). Effects of different active flow control strategies are assessed and compared with the baseline model in both hover and forward flight conditions.
High-fidelity Numerical Investigation of Complex Propeller Flows
Authors:   University of Glasgow, Zhang Tao , Higgins Ross , Barakos George
Published: September 2022

This paper presents high-fidelity numerical investigations of complex propeller flows using the HMB3 solver of Glasgow. The present study focused on the GATEUR AG25 rotor/propeller integration examined by ONERA. This study compares and evaluates various rotor modelling and turbulence modelling approaches for the simulation of isolated and isolated propellers. Simulations of the baseline isolated propulsors were first carried out and validated against experimental measurements. Simulations of the rotor/propeller integration were then carried out at lowspeed forward and also at hover. The results were compared with the isolated cases to highlight the performance changes due to the aerodynamic interactions. Effects of the forward speed were compared and discussed in detail. In hover, the aerodynamic interference was found to be considerably exacerbated. Elaborate comparisons were also performed between methods to bring out the gains and losses of different modelling options.
Computational Analysis of a Quiet Single-Main Rotor Helicopter for Air Taxi Operations
Authors:   NASA Ames Research Center, Diaz Patricia , Perez David , Yoon Seokkwan
Published: September 2022

A computational study has been done on NASA's quiet single-main rotor helicopter concept for urban air mobility using high-fidelity computational fluid dynamics, rotorcraft comprehensive analysis tools, and computational aeroacoustics. High-order accurate schemes, dual-time stepping, and the delayed detached-eddy simulation model have been employed. A loose-coupling approach between the flow solver and the rotorcraft comprehensive code is implemented toinclude vehicle trim and blade motions. Acoustic simulations based on the Ffowcs-Williams and Hawkings equations have been performed to compute the rotor noise. Different blade geometries and tip speeds are analyzed, and performance and acoustics results are compared. The vehicle has been simulated in hover and cruise, with flight conditions representative of an air taxi mission. The quiet single-main rotor helicopter is one of the conceptual designs intended to focus and guide NASA's research activities in support of aircraft development for vertical take-off and landing air taxi operations.
Uncertainty Quantification Approach for Rotorcraft Simulations
Authors:   U.S. Army, Jayaraman Buvana ,   Science & Technology Corporation, Khurana Manas , Wissink Andrew , Jain Rohit
Published: September 2022

The goal of this work is to quantify the uncertainty and sensitivity of freestream velocity and wind direction on wing download and rotor thrust predictions for the Joint Vertical Experiment (JVX) tiltrotor configuration in hover. Even light winds can have a significant impact on hover performance. Accordingly, an accurate representation of hover performance with uncertainties due to variability in atmospheric wind conditions needs to be understood. To support this effort, mid-fidelity simulations with a Reduced Order Aerodynamic Model in CREATETM-AV Helios is used to generate training and testing data for constructing the surrogate models. Uncertainty propagation is facilitated using a surrogate-based approach which integrates stochastic expansions based non-intrusive polynomial chaos method in the Dakota�environment. The first test case considers wind velocity and directions treated as epistemic uncertain variables. Post uncertainty analysis, parameter sensitivities are established using Sobol indices to rank the relative contribution of input parameters to the total uncertainty in download and thrust. Sensitivity analysis showed that the interaction of wind velocity and direction has the largest influence on download predictions. The second case includes collective as an uncertain input and additionally carries out a sensitivity analysis. Computed Sobol indices identified collective as the major contributor of uncertainty. Ultimately, uncertainty quantification procedure laid out in this work can facilitate informed design decisions based on quantifiable data that is formed using validated computational approaches integrated with established data science principles with statistical metrics.
High-fidelity Simulations of Rotors in Compact Configuration
Authors:   University of Stuttgart, Miesner Sebastian , Kessler Manuel , Kramer Ewald
Published: September 2022

High fidelity CFD simulations of seven rotors in compact configuration at three different flight scenarios are performed. The cases are hover, as well as 50 km/h and 100 km/h forward flight. For comparison each rotor is simulated isolated with the same RPM and pitch angle as in the configuration. Additionally, a bigger isolated rotor with the same area as the complete configuration is simulated. For the configuration as well as the bigger rotor a flight mechanic trim is performed using the flight mechanic tool VFAST. The CFD simulation is performed with FLOWer. In hover, only the center rotor showed a significant Figure of Merit (FM) drop of 16% compared to the isolated rotor. The thrust of the outer rotors is increased at the tip areas facing outwards, while the tip areas towards the center and the tip areas of the center rotor showed reduced thrust compared to the isolated rotor. The wake contraction at the outer rotors is increased compared to the bigger rotor. For the 50 km/h forward flight the efficiency of the front rotors is increased (10%-17%) and the rear ones decreased (11%-16%). In this case the wake is directly convected from the front rotors into the rear rotor planes and strong vortex interactions occur. For the 100 km/h case the efficiency gain of the front rotors is reduced to 3%-11% and the decrease to 5%-9%. Due to the higher pitch the wake of the rotors flows away from the rotor plane and the rotor-rotor interactions are reduced.
Helicopter Shipboard Operation: Effect of Atmospheric Boundary Layer on Turbulent Ship Airwake and Rotor Aerodynamic Loads
Authors:   Politecnico di Milano, Taymourtash Neda , Morelli Myles , Guardone Alberto , Quaranta Giuseppe
Published: September 2022

This paper studies the effect of two different boundary layer models on the airwake of the Simple Frigate Shape 1 and further on the unsteady aerodynamic loads of a scaled helicopter model operating inside the ship airwake. The unsteady airwake of the isolated SFS1 is computed in a time-accurate approach using the open-source SU2 solver, implementing two types of boundary conditions: a Uniform Flow (UF) and a steady Atmospheric Boundary Layer (ABL), where the reduction of the velocity due to the surface roughness is also considered. The simulations are performed in two wind conditions, including headwind and 30? from the port-side (R30). The airwake data are implemented into a multibody simulation of a scaled helicopter model, developed using the open-source multibody software MBDyn, based on the one-way coupling approach. Hover tests are performed at different positions with respect to the deck and the unsteady aerodynamic loads are compared in frequency domain. In addition to the increase of unsteadiness in the red wind compared to the headwind simulation, the results indicate that in both wind conditions, the unsteadiness is reduced with the presence of the steady ABL. Since the unsteady loads are expected to directly affect the pilot workload, the results highlight the importance of modelling a realistic boundary layer considering both steady and turbulent profiles.
Automated Inference of Vortex Core Physics of Hovering Rotor Wakes Using Machine Learning Techniques
Authors:   HPCMP CREATE, Abras Jennifer , Hariharan Nathan
Published: September 2022

Machine learning can significantly enhance the insights gained from large aerodynamic computational data sets. Specifically, 3D rotor wake computations produce detailed vortex structures, but typically, only a small fraction of the data is leveraged. A critical limiting factor is the time needed to process these large 3D data sets and infer the correct physics. The development of machine learning methods to process these data sets reduces the data processing burden on the analyst and also increases the volume of data that can be processed within a reasonable amount of time. Recent efforts in this area have resulted in the development of a novel machine learning-based vortex-core data extraction methodology. The present study demonstrates the application of this method to hovering rotor wakes to compare different blade tip geometries, ground effect, wake grid spacing, and collective changes and discusses the extracted vortex physics for each case.
A Combined Experimental and Computational Analysis of the Flow Field of a Coaxial Counter-rotating Rotor in Hover
Authors:   University of Texas at Austin, Mortimer Patrick ,   U.S. Army Combat Capabilities Development Command AvMC, Ho Jimmy ,   San Jose State University, Padthe Ashwani , Sirohi Jayant , Lopez Mark
Published: September 2022

The flow fields of a 2m-diameter two-bladed single rotor and a 2�2-bladed coaxial counter-rotating rotor were measured using Particle Image Velocimetry, and computed using a coupled RCAS-VVPM analysis. Time-resolved measurements were performed on the single rotor at 44/rev with at least 552 flow realizations per azimuth. Similar measurements were performed for the coaxial, counter-rotating rotor at 64/rev with at least 260 flow realizations per azimuth. The goal of this study was to compare the flow features of these rotor configurations and validate current numerical analyses. Overall, there was good correlation between the measurements and calculations for the single rotor configuration. Numerical computations captured the axial velocity distribution across the blade radius and rotor azimuth. The radial distributions of axial velocity revealed less agreement in the tip region due to differences in the tip vortex trajectories. The tip vortex positions extracted from the measurements revealed a radial displacement of delta r/R = 0.112 and an axial displacement of delta z/R = 0.230 over one rotor revolution. The numerical computations captured the radial position for the first blade passage, but over predicted the radial position after blade passage. The axial positions were under-predicted over the entire azimuthal range. Comparison for the coaxial, counter-rotating rotor configuration revealed a consistent over-prediction in both radial and azimuthal velocity profiles for all spatial locations investigated. The axial position of the tip vortex were captured well with slight under-prediction for the upper rotor. The radial tip vortex positions were over-predicted over the entire azimuthal range investigated. Further validation of the numerical model is required before it can be used to extract state-space inflow models for single and coaxial, counter-rotating rotors.
Improved Initial and Boundary Conditions for Hovering Rotor CFD Simulations
Authors:   Flexcompute Inc., Jia Feilin , Wang Qiqi , Spalart Philippe
Published: September 2022

The new flow fields originate in a 2012 paper by Spalart (Ref. 1), which addresses the far-field behavior induced by a momentum source, such as a hovering rotor or a static jet. This model incorporates entrainment into the turbulent far wake, and supersedes the time-honored model based on a sink field. In the present study, a new initial condition as well as boundary condition based on a modified version of the above far-field model are investigated by unsteady simulations of the XV-15 rotor in hovering flight condition at collective pitch angle ? = 10?. The idea is to inject an approximation to the rotor's wake under it. From our results, compared to the freestream initial condition, the far-field model based new initial condition can quickly establish the low-speed induced flow and achieve faster convergence of thrust and torque to statistically steady state. The chaotic starting vortex can be effectively flushed out by the new initial condition to prevent the oscillations of thrust due to blade-vortex interaction shown in the simulation from the freestream initial condition. Results of the modified far-field model as a far-field boundary condition to hovering f light in multiple reduced computational domains are also presented. Although the new boundary condition doesn't show evident speedup in convergence of thrust and torque, its wake can be developed much faster than the freestream boundary condition due to its prescribed velocity field at the boundary. This new initial and boundary condition could be beneficial to simulations of multi-rotor aircraft.
Numerical Simulations of the Adverse Effects of Rain on Airfoil and Rotor Aerodynamic Characteristics
Authors:   Georgia Institute of Technology, Gahlot Aishwerya ,   Siemens PLM Software, Eshcol Ritu ,   NASA Glenn Research Center, Kreeger Richard , Sankar Lakshmi
Published: September 2022

There is a significant interest in improving the performance of rotors under adverse operating conditions. However, there is a very limited understanding of the performance implications on 2D airfoils and rotor blades under adverse effects of rainfall. Furthermore, the fundamental physical phenomena causing the loss in performance are not clearly understood. In this study, low fidelity models are first developed to rapidly estimate the water layer formation on 2D airfoils and assess the resulting impact on lift and drag characteristics. The low fidelity simulations are also useful to obtain quick estimates of water layer thickness as a function of liquid water content and droplet diameter. Subsequently, computational fluid dynamics studies for 2D airfoils and a small-scale rotor in hover are done to obtain more accurate estimates of the effects of rain on airfoil performance and match test data where available. Higher-fidelity parametric studies for various airfoils were conducted by varying angles of attack, the liquid water content in the rain droplets, and the droplet diameters to capture trends in performance degradation. The resulting trends match the trends from the test data reasonably well. The higher fidelity airfoil loads are subsequently used within a classical combined blade element-momentum model (BEM) to assess the loss of performance attributable to rain for a small-scale rotor.
CFD Simulation of Flow Around ROBIN-Mod7 Fuselage with PSP Rotor Using an Immersed Boundary Method
Authors:   University of Sydney, Park Hee , Linton Daniel , Thornber Ben
Published: September 2022

Computational fluid dynamics simulations of the flow around the ROBIN-mod7 fuselage with PSP rotor are conducted using an immersed boundary method and an actuator surface model in OpenFOAM. The ROBIN-mod7 fuselage is represented by the immersed boundary method, while the unsteady rotor is modeled using the actuator surface model. The integration of the immersed boundary method and actuator surface model is straightforward; there is no fundamental reason to be conflicted with each other in both theory and practice. A comprehensive analysis of the generic helicopter configuration is carried out for the hovering flight condition; the isolated fuselage is simulated to provide its baseline aerodynamics, and the isolated rotor and rotor-fuselage cases are studied to measure the rotor performance in hover and the fuselage effect on the performance. The validation of each test case is conducted against both experimental measurements and computational data from the literature. The surface pressure data from the isolated fuselage case shows good agreement with the experimental measurements. Also, the rotor performance predicted on the isolated and installed rotors (rotor-fuselage) has excellent agreement with the reference data; in particular, the performance data on the installed rotor agrees with the experimental data better than the previous numerical study does. The fuselage effect has been analyzed by comparing the isolated rotor and rotor-fuselage data sets. The computational effort for different grid levels of each test case is provided. Overall, the results have demonstrated an equivalent level of accuracy compared to the previous high-fidelity simulation results at their fraction of setup and computational expenses.
A Realistic Rotorcraft Noise Footprint Computation for Low-Noise Trajectory Optimization
Authors:   Airbus Helicopters, Dieumegard Pierre ,   Universite de Toulouse, Cafierl Sonia , Guntzer Frederic , Caillet Julien
Published: September 2022

This paper introduces recent developments in the computation of rotorcraft noise footprint, implemented in an Airbus
Helicopters' internal software. The paper presents the main ingredients that have led to enhance the efficiency and
accuracy of such noise footprint computation. This includes taking into account both the particularities of turns in
noise emission and the influence of the wind on noise propagation. Furthermore, the software is able to assess a real
traffic environmental impact, since computations are done within a realistic 3D simulation environment, taking into
account both the curvature of the Earth and the topography of the ground. A variety of noise annoyance indicators
can be computed thanks to the coupling with demographic and background noise data. Such realistic noise footprint
computation is embedded in a tailored algorithmic scheme aiming at optimizing rotorcraft trajectories in such a way
that their associated noise footprint is minimized. The proposed optimization approach has been tested on multiple
real-world case studies, showing significant prospective noise reduction compared to reference trajectories.
Comments on “Identifying psychological antecedents and predictors of vaccine hesitancy through machine learning: A cross sectional study among chronic disease patients of deprived urban neighbourhood, India”
Authors: Mungmunpuntipantip Rujittika , Wiwanitkit Viroj
Published: September 2022

Dear Editor,
we read the publication by Rustagi et al. “Identifying psychological antecedents and predictors of vaccine hesitancy through machine learning: A cross sectional study among chronic disease patients of deprived urban neighbourhood, India" with a great interest...