Variation Of Angle Research Articles

Aerodynamic characteristics of the train under the stationary thunderstorm downburst wind

The aerodynamic characteristics of the train under the stationary thunderstorm downburst wind were studied. The thunderstorm downburst wind test device was employed to simulate the thunderstorm downburst wind field. Based on the rigid model pressure measurement tests, analyses were conducted on the influence of radial distance on the pressure coefficients on the train surface, the aerodynamic load coefficients of the train section, and the total force coefficients of the middle and head cars. On this basis, combined with the computational fluid dynamics model, further exploration was conducted on the characteristics of the mean pressure on the train surface and the flow field around the train at different radial distances under the stationary thunderstorm downburst wind. The research results show that the train's total aerodynamic coefficients fluctuate with the train's position. The non-uniform distribution of the lateral force coefficient for each train section is primarily caused by variations in the wind yaw angle along the train's longitudinal axis. Variations in the wind attack angle at different radial distances cause the total lateral force coefficient to change accordingly. When the radial distance r/Dj = 0.5, there is no significant vortex-shedding phenomenon in the flow field around the train. However, when radial distance r/Dj = 1 and 1.5, the leeward surface exhibits a regular vortex-shedding phenomenon. Vortex shedding starts at the junction of the leeward surface and the top surface, extending from the middle car along the train's longitudinal axis toward the front and rear.

Determination of the effects of size parameters and lean angle on Bovet-based Francis turbine runner performance

Abstract In global hydropower generation, the Francis turbine is widely used because of its ability to work efficiently in a wide range of conditions like varying head and flow rates. Turbine’s meridional profile can be developed using traditional design approaches, like the Bovet method which uses empirical relations based on hydrological factors, that can be refined through optimization. Runner performance evaluation considers factors such as efficiency, erosion resistance, resistance to cavitation, and many more. Adjusting design parameters can enhance a turbine’s performance at a particular site. In this paper, a Bovet-based Francis runner design was obtained for Damile Micro Hydro located at Pharping, Nepal and the effect of variation of size parameters and lean angle on the runner performance was investigated. Initially, In-house MATLAB codes were used to design 99 meridional profile of different sizes by changing the size parameters as indicated by Bovet method and numerical simulation was performed to select the best meridional profile based on efficiency. After obtaining best meridional profile, the effect of lean angle was studied by varying it from -10° to 10°. Among the 99 designs based on different sizes, the simulation results indicate that the maximum efficiency was found to be 92.3% whereas the minimum efficiency was found to be 87.84%. The corrected lean angle of -5° showed the maximum efficiency and better pressure distribution along the blade.

Experimental Study on the Effect of Flow Velocity and Slope on Stream Bank Stability (Part I)

The erosion of riverbanks is a significant and capricious national concern. The Al Muwahada channel in Iraq experiences instability in its banks, resulting in failure, retreat, and morphological alterations. These issues are mostly caused by factors such as the velocity of the flow, the angle of the slope, and type of soil. This study investigated the behavior of canal bank soil in response to erosion and variations in slope angle. Therefore, a physical model of a case study was established in the laboratory. Additionally, a slope angle of 26˚ is being utilized, which has not been previously studied in the laboratory. This angle will be tested with five different velocity values: 0.101 m/s, 0.116 m/s, 0.12 m/s, 0.13 m/s, and 0.135 m/s. The bank's deformation was measured for a period of 12 hours, which was divided into 4 equal intervals for each velocity. The study determined that a riverbank with a slope of 26˚ is more resistant to erosion when the velocity of the water is below 0.12 m/s. Velocities equal to or greater than 0.12 m/s have a substantial impact on the erosion of the riverbed. According to this study, a velocity of 0.12 m/s or higher leads to increased erosion of the riverbank. This is equivalent to a velocity of 0.804 m/s in the prototype channel. The section of the riverbank that has suffered the greatest damage due to erosion is the upper two-thirds. The used methodology supports global efforts to increase information about the behavior of river banks with unexplored rivers that have different flow velocities and bank slope angles. Doi: 10.28991/CEJ-2024-010-08-013 Full Text: PDF

Investigation of the effect of rectangular winglet angles on turbulent flow and heat transfer of water/Cu nanofluid in a three-dimensional channel

This numerical simulation studies a homogenous and single-phase nanofluid's turbulent flow and heat transfer behavior in a three-dimensional rectangular microchannel. This study's main purpose is to investigate the use of rectangular winglet angles on flow path and its effect on turbulent flow regime and heat transfer parameters. In the current study, the Reynolds number, winglet attack angle (θ), and twisted angle range (α) (or Pitch angle) from 3000 to 12000, 30°≤ θ ≤ 60°, and 15°≤α ≤ 45°, respectively. Also, Cu nanoparticles with volume fractions of 0–4% are used in water as the base fluid. Results of this study show that heat transfer and flow physics of cooling fluid are affected by the variations of attack angle and winglet twist, and the creation of secondary flows leads to the mixture and deviation of flow. A decrease in the attack angle of the winglet causes the creation of strong vortexes and an increase in Nusselt number and heat transfer. In all investigated situations, with the angle of attack constant, increasing the twist angle can improve the Nusselt number between 11 and 18 percent. Also, increasing the angle of attack of the winglet from 30 to 60° can reduce the Nusselt number by 4–8 percent. The results indicate that changing the winglet angle increases the friction coefficient, and at higher Reynolds numbers, this parameter decreases. Also, by increasing Reynolds number, the ratio of friction coefficient to Nusselt number reduces, leading to the decrease of performance evaluation criterion (PEC).

Terrestrial locomotion stability of undulating fin amphibious robots: Separated elastic fin rays and asynchronous control

To address the problem of poor postural stability in an undulating fin robot during terrestrial locomotion, this study proposes a novel design featuring separate elastic fin rays with an asynchronous control scheme for bilateral fin surfaces. In this scheme, the robotic fin ray structure and surface driving mode are innovatively designed to mitigate the pitch-angle instability caused by adverse factors, such as integral rigid fin rays and synchronized fin surfaces. Expanding on the ground dynamics model of the robot, this study examined the variation in the pitch angle of the robot body. In this study, an innovative design with separated elastic fin rays was proposed and their feasibility was validated through finite element simulations. In addition, a virtual simulation prototype of the robot was developed to verify the robot body stability under asynchronous fin surface control. The simulation results show that separate elastic fin rays and asynchronous control can effectively improve the postural stability of robots in terrestrial locomotion. In this study, a robot prototype was tested experimentally in various terrestrial environments. The experimental results indicate that equipping the robot with separated elastic fin rays and employing asynchronous motion control significantly enhances the motion postural stability across typical terrain conditions. The maximum pitch angle range can be reduced by 42.7–52.4%, providing new insights for the design of amphibious robots with undulating fins.

Effect of Calcination Temperature on the Structural, Morphological, and Magnetic Properties of Rare-Earth Orthoferrite NdFeO3 Nanoparticles Synthesized by the Sol-Gel Method

The sol-gel technique has been used to synthesize rare Earth orthoferrite NdFeO3 nanopowders. The present investigation examines how calcination temperatures affect the structural, morphological, and magnetic properties of NdFeO3 orthoferrites. X-ray diffraction studies indicate that there is no discernible difference in the observed structures with calcination temperatures other than the bond distances and bond angles. The surface morphology and field-emission scanning electron microscopy (FESEM) indicate that porosity of the samples is regulated by the physical shape of the tiny particles within them. Porosity is minimized as calcination temperature increases, showing a higher density that contributes to reducing leakage current features while improving the break-down strength. These variations are attributed to bond length and bond angle variation of the Fe-O. The photocatalytic activity of the NdFeO3 nonoparticles was assessed by photodegrading a number of organic dyes, including methyl orange (MO), rhodamine B (RhB), and methylene blue (MB). The product displays significant photocatalytic degradation of the dyes whenever exposed to visible light. Overall, this investigation aims to establish a relationship between the physical properties and microstructural parameters to provide valuable insights into the magnetic interactions present in the samples and the comprehensive behavior of NdFeO3 orthoferrites samples calcination at different calcination temperatures.

Influence of Solvent Polarity on the Conformer Ratio of Bicalutamide in Saturated Solutions: Insights from NOESY NMR Analysis and Quantum-Chemical Calculations.

The study presents a thorough and detailed analysis of bicalutamide's structural and conformational properties. Quantum chemical calculations were employed to explore the conformational properties of the molecule, identifying significant energy differences between conformers. Analysis revealed that hydrogen bonds stabilise the conformers, with notable variations in torsion angles. Conformers were classified into 'closed' and 'open' types based on the relative orientation of the cyclic fragments. NOE spectroscopy in different solvents (CDCl3 and DMSO-d6) was used to study the conformational preferences of the molecule. NOESY experiments provided the predominance of 'closed' conformers in non-polar solvents and a significant presence of 'open' conformers in polar solvents. The proportions of open conformers were 22.7 ± 3.7% in CDCl3 and 59.8 ± 6.2% in DMSO-d6, while closed conformers accounted for 77.3 ± 3.7% and 40.2 ± 6.2%, respectively. This comprehensive study underscores the solvent environment's impact on its structural behaviour. The findings significantly contribute to a deeper understanding of conformational dynamics, stimulating further exploration in drug development.

Detecting the Variations in the Phase Angle through the Fatigue Life of Asphalt Concrete under Environmental Influence

Detecting the Variations in the Phase Angle through the Fatigue Life of Asphalt Concrete under Environmental Influence

Study of adhesive wear mechanisms in asperity junctions based on phase field fracture method

Adhesive wear that is mostly induced by adhesion between asperities of rough surfaces in contact is one of the most common forms of wear of materials. However, the adhesive wear mechanisms are still not fully understood. In this work, the phase field fracture method that does not require any assumption on the crack path is used to explore the debris formation mechanism during asperity separation in adhesive wear. It is found that for ideal materials without defects the size of wear particles depends on the contact length. A small contact length leads to fracture at the junction and the formation of small wear particles. On the contrary, a large contact length will cause fracture in the bulk, resulting in large wear particles. Moreover, the angle of crack propagation decreases with increasing base angle of asperity and the ratio of the asperity height to the base edge width. The variation of fracture angle is mainly related to the ratio of asperity height to the base edge width that will influence the angle of the interaction force between asperities in the wear process. For materials with initial hole defect, the formation mechanism of wear particles will be little affected when the hole is rather small or far away from the junction. However, as the hole diameter further increases, the wear particles will change from large particles to small ones. And for materials with initial crack defect, the crack propagation always starts from the initial crack during adhesive wear. Moreover, for adhesive wear of materials with an initial crack at the bottom of asperity, fracture angle in the bulk is significantly positively correlated with the contact length and large wear particles are easy to form. However, during adhesive wear of asperity with the initial crack inside the bulk of asperity, small particles are more likely to form. This work contributes to further understanding of adhesive wear process.

Study of the contact angle and roughness effects on mercury intrusion porosimetry (MIP) analysis in natural/real carbonate rocks using massive pure minerals and synthetic carbonate rocks

Studying pore networks in rocks is critical for understanding reservoir properties, with mercury intrusion porosimetry (MIP) being a key laboratory method. MIP involves capillary intrusion of mercury, with intrusion pressure (P) related to capillary diameter (d) by the Washburn equation, incorporating mercury properties like contact angle (θ) and surface tension (γ). While a constant contact angle of 140° is typically assumed for MIP, it can vary based on rock mineralogy and surface roughness. This study aims to analyze how contact angle variations and surface roughness affect MIP analysis of carbonate rocks. Initially, contact angle data was obtained for calcite, dolomite, and quartz with varying roughness levels. Synthetic rocks were then constructed using these minerals. MIP was performed using the typical 140° contact angle and a calculated contact angle from the Cassie model, which considers surface composition fraction. Natural rock MIP analysis followed, with contact angles varying due to mineral composition and roughness. The study found higher contact angles than the standard 140°, affecting pore size distributions up to 30%. Natural rock pore network curves were adjusted based on synthetic rock data analysis. These findings emphasize the need for accurate contact angle selection in MIP for precise pore distribution analysis and contribute to the further study of carbonate rocks.

Treatment of Intrabony Defects with Non-Surgical Subgingival Debridement: A Radiographic Evaluation of Bone Gain Using an Experimental Digital Software "Bone Defect Analysis (BDA)".

Background: The aim of this study was to retrospectively evaluate the 3-year radiographic outcomes of periodontal intrabony defects treated with non-surgical subgingival therapy (NST), assessing radiographic bone gain (RBG) through experimental digital software, named "Bone Defect Analysis (BDA)". Methods: The study included 17 intrabony defects in 14 patients. BDA software (version 1) was used on radiographs to calculate RBG (in %) and variations in defect angle (in °) between baseline (T0) and 3-year follow-up (T1). Soft tissue conditions were registered, reporting bleeding on probing (BOP), probing pocket depth (PPD), and clinical attachment level (CAL). Defects were analyzed according to angles less (group A) or greater (group B) than 30°. Results: Nine and eight defects were, respectively, analyzed in groups A and B. Three years after treatment, an average RBG of 12.28% was found overall, with 13.25% and 10.11% for groups A and B, respectively (p = 0.28). Clinically, a mean CAL of 6.05 mm at T1 (from 10.94 mm at T0) was found, with 6.88 mm and 5.12 mm in groups A and B, respectively (p = 0.07). Conclusions: BDA software demonstrated predictability in the evaluation of bone variations after NST, revealing better clinical findings for intrabony defects with an initial smaller angle.

Bidirectional triple-band truly incident angle insensitive polarization converter using graphene-based transmissive metasurface for terahertz frequency

Abstract The design and response of a triple-band linear-to-circular polarization converter (LTCPC) in the terahertz frequency regime using a graphene-based transmission-type metasurface have been studied numerically and analytically. The unit cell of the converter is constructed using lossy silicon dioxide (SiO2) with a relative permittivity of 3.9 as the substrate. And two similar layers of graphene-based sub-wavelength structures are used at the top and bottom of it. Multiband linear to circular polarization conversion is achieved from 0.74 THz to 0.98 THz, 1.70 THz to 2.33 THz, and 4.06 THz to 5.19 THz, i.e., about 28 %, 31 %, and 24 % fractional bandwidths, respectively. As the same metasurface configuration is used at the top and bottom layers of the transmission-type unit cell, it can be used as a bidirectional polarization converter with identical responses from both sides. The geometrical optimization of the unit cell is done, and an equivalent lumped parameter circuit model is also proposed for the same, considering analogous responses. Tunability over the operating frequency is achieved by varying the chemical potential and relaxation time of graphene. Moreover, due to the ultrathin width and special types of identical configuration of the metasurfaces, the response of the system remains excellent over a wide range of incident angle variations up to 80° angle of incidence.

Modeling non-monotonic variation of plume angle with superheat index of flash boiling spray

There is an urgent need for modeling angles and widths of liquid jet with internal phase change, but existing semi-empirical models rely strongly on coefficient fitting and lack a thorough understanding of the additional phase-change physics. In the present work, we proposed a theoretical model to predict the non-monotonic variation of plume angle with the defined superheat index of flash boiling spray. Assuming that the plume angle is determined by the trajectories of tiny droplets in the perimeter of the spray, this model identifies the angle with the inverse tangent of the ratio of the streamwise and crosswise velocities of the tiny droplets. The streamwise velocity is determined by solving a one-dimensional two-phase flow within the channel, and the crosswise velocity is determined by modeling the burst of an equivalent bubble at the exit of the nozzle. Compared with the existing semi-empirical models, this model is free of fitting parameters, and it agrees well with the experimental data from a rectangular microchannel with discrepancies being sufficiently discussed. This model has the potential of being applied to modeling the plume angle of flash boiling sprays with different nozzle geometries in various atomization practices.

Coherent manipulation of bright and dark solitons of reflection and transmission pulses through sodium atomic medium

Abstract The coherent manipulation and control of bright and dark solitons through sodium atomic medium have been investigated in this manuscript. Dark soliton is reported for reflection and bright soliton is reported for transmission pulses with variation in position and driving field parameters through sodium atomic medium. Further the transmission pulse is periodic dark and bright solitonic behaviors and reflection pulse is periodic bright solitonic behavior with variation in the incident angle and Rabi frequency of the control field. Elliptical dark and bright solitons as well as breather types solitons are also investigated for reflection and transmission pulses. The dark soliton in reflection is due to slow light propagation and bright soliton is obtained due to fast light propagation of transmission through the medium. The modified results of the dark and bright solitons are useful for telecommunication and ultra-fast signal routing system.

Sea surface Fresnel reflections difference driven de-glint algorithm for airborne optical images.

This paper presents a glint correction algorithm for high spatial resolution optical remote sensing imagery captured by the ER-2 Airborne Visual Infrared Imaging Spectrometer (AVIRIS). The algorithm employs linear and differential techniques to mitigate sun glint and sky glint effects, encompassing statistical glint reflections resulting from variations in imaging angles within strips and inter-strip variations due to Fresnel reflectance disparities. It aims to diminish Fresnel reflectance diversity on water surfaces and mitigate the distortions induced by glint reflectance during spectral and ocean color inversion. A comparative analysis of spectral and ocean color information in AVIRIS images before and after correction reveals enhanced accuracy following the glint correction. By systematically addressing multiple glint reflections and their ramifications, this method offers a valuable framework for correcting water surface glint in diverse high spatial resolution optical imagery.

Aerodynamic Effects of Time-Varying Corrugations on Dragonfly Wings in Flapping Flight.

The aerodynamic effects of wing corrugation on insect flight have received widespread attention. However, there has hardly been any specific focus on dynamic changes to corrugation angle in the models. The flexible vein joints containing resilin in the wings of dragonflies and damselflies enable the longitudinal veins to rotate and thereby change the corrugation angles throughout flapping cycles. Therefore, a two-dimensional corrugated airfoil with time-varying corrugation angles is proposed and the aerodynamic performance is evaluated in terms of aerodynamic force, power and efficiency. The results indicate that the airfoil with time-varying corrugations outperforms the rigid one in terms of enhancing thrust and reducing power consumption. The aerodynamic performance of time-varying corrugated airfoils is optimal when the angle varies in a specific range, and an excessively large angle variation may have negative effects. In addition, excessive height or a negative leading edge of the corrugation can lead to a reduction in the thrust. A design concept for the 2D airfoil with time-varying corrugations is provided and the findings are of significance for enhancing the aerodynamic performance of biomimetic flexible flapping-wing vehicles.

Polarization Influence on Er3+-Doped Multi-Wavelength Brillouin Fiber Laser Based on Fiber Loop Mirror

Polarization influences on the performance of multi-wavelength Brillouin Er3+-doped fiber laser are investigated by adjusting the polarization controller (PC) in the fiber loop mirror (FLM), where the linear laser cavity is composed of a fiber-tailed mirror and an FLM, and the stimulated Brillouin scattering (SBS) and the Er3+-doped fiber amplification (EDFA) simultaneously serve as the cavity gain. We realized 1–7 Brillouin laser lines by increasing the 980 nm pump power. For the first-order Brillouin laser, the signal–noise ratio (SNR) and optical intensity present a sinusoidal envelope; the conversion efficiency changes significantly from 0.56465 dBm/mw to 0.44975 dBm/mw by adjusting the ring’s angle in the PC; the first-order SBS thresholds are 20.4 mw, 36.1 mw and 28.5 mw at different angles θ2 = 36°, 276° and 300°, respectively; flatness between the two Brillouin lasers change obviously from 2.863 dB to 41.801 dB with different ring angles; the second-order Brillouin laser is suppressed and disappears finally at Δθ2 = −64° to −84° and 106°~136° angle variation. For the fifth-order Brillouin laser, the highest-order Brillouin laser line is seriously suppressed until it disappears at some angle variations similarly. The powers and wavelength stabilities for one-, three- and seven-wavelength Brillouin fiber lasers were measured in 1 h, and the obtained Er3+-doped multi-wavelength Brillouin fiber laser (MWBFL) worked stably during that time, but the stabilities become worse with higher SBS orders.

Photocatalytic coatings with self-cleaning properties for indoor air treatment

In this work we have studied the photocatalytic and self-cleaning properties of TiO2 layers immobilized on polymeric panels, as passive elements for air treatment. In order to achieve easy scale-up technologies for the preparation of coatings, roller-coating technique was selected, comparing the results with those prepared by dip-coating. Composites were characterized by SAXRD, UV–Vis DRS spectroscopy, profilometry, N2 adsorption–desorption, SEM and AFM microscopy. The adherence of the coating was evaluated according the ASTM D3359 standard adhesive tape test. The photocatalytic properties of the materials were evaluated by the photodegradation of trichloroethylene or formaldehyde, as model volatile organic compounds, in the gas phase. The hydrophilic-hydrophobic properties were measured by studying the in-situ variation of the water contact angle with time and UV-A irradiation. Moreover, the self-cleaning properties were analyzed according to ISO 27448:2009 for oleic acid removal. Although coatings of approximately ca. 250 nm layer thickness can be prepared by both techniques, roller-coating allows the material deposition with a coral-like structure in a single and simple step. Surface roughness was promoted by roller process. The developed materials present high photocatalytic performance for the elimination of both model pollutants in the gas phase. Aging tests under outdoor conditions and Scotch tape test show the stability and resistance of the coatings. In-situ irradiation measurements show the superhydrophilic character of the coatings. Water contact angle lower than 10 ° after 300 min of UV-A irradiation was achieved for oleic acid removal. The combination of TiO2 nanoparticles with different crystal structures and sizes improves the photocatalytic performance. A correlation between the ability for pollutants degradation in gas phase and the self-cleaning properties (in-situ or oleic acid measurements) was determined.

Research on the Effect of Fracture Angle on Neutron Logging Results of Shale Gas Reservoirs

Fracture structures are important natural gas transport spaces in shale gas reservoirs, and their storage state in shale gas reservoirs seriously affects gas production and extraction efficiency. This work uses numerical modeling techniques to investigate the logging response law of the thermal and epithermal neutrons in the gas-containing fracture environment at various angles, applying neutron logging as a technical method. To increase the precision of the evaluation of the natural gas storage condition in shale gas reservoirs, the angle of the fractures’ neutron logging data is analyzed. It is found that even in an environment with the same porosity of the fractures, there are significant differences in the logging results due to the different angles of the fracture alignment: 1. the neutron counts in the high-angle (70–90°) fracture environment are 2.25 times higher than in the low-angle (0–20°), but the diffusion area of the neutrons is only 10.58% of that in the low-angle (0–20°); 2. in the neutron energy spectrum, neutron counts are spreading to the high-energy region (7–13 MeV) along with the increase in the angle of the fracture, and the feature is especially prominent in the approximately vertical (60–90°) fracture environment, which is an increase of 528.12% in comparison with the counts in the approximately horizontal angle (0–30°) environment. The main reason for these differences is the variation in the volume of the fracture within the source radiation. This volumetric difference results from the variation in fracture angles (even though the fracture porosity is the same). In view of the above phenomenon, this paper proposes the concept of “effective fracture volume”, which can intuitively reflect the degree of influence of fracture angle on neutron logging results. Further, based on the unique characteristics of shale gas reservoirs and neutrons, this paper provides important theoretical support for the modification of the porosity of the field operation, the evaluation of the physical characteristics of the gas endowment space, and the assessment.

Effects of soil spatial variability on the behaviour of the embankment supported with a combined retaining structure

In this study, the effects of soil spatial variability on the behaviour of the embankment supported with a combined retaining structure (CRS) were investigated. The numerical model of the CRS embankment was established and validated with the field data. An application programming interface (API) was developed to deal with the data exchanging issue between the numerical model and the spatial variability characterization model. Based on the verified numerical model and the API, the probabilistic analysis with 500 Monte Carlo simulations was automatically computed. Three influencing factors of the retained soil (the mean of the friction angle, the variation of the friction angle and the vertical correlation length of the random field) are analysed by parametric analysis. The results show that the vertical correlation length of the random field is most important in the earth pressure calculation process, while the mean of the friction angle is the factor with least impact. On the whole, the spatial variability of soil properties has minimal impact on the distribution and magnitude of earth pressure behind the retaining structure.