Aerodynamic Shape Optimisation of a Camber Morphing Airfoil and Noise Estimation

In order to decrease the emitted airframe noise by a two-dimensional high-lift configuration during take-off and landing performance, a morphing airfoil has been designed through a shape design optimisation procedure starting from a baseline airfoil (NLR 7301), with the aim of emulating a high-lift configuration in terms of aerodynamic performance. A methodology has been implemented to accomplish such aerodynamic improvements by means of the compressible steady RANS equations at a certain angle of attack, with the objective of maximising its lift coefficient up to equivalent values regarding the high-lift configuration, whilst respecting the imposed structural constraints to guarantee a realistic optimised design. For such purposes, a gradient-based optimisation through the discrete adjoint method has been undertaken. Once the optimised airfoil is achieved, unsteady simulations have been carried out to obtain surface pressure distributions along a certain time-span to later serve as the input data for the aeroacoustic prediction framework, based on the Farassat 1A formulation, where the subsequent results for both configurations are post-processed to allow for a comparative analysis. Conclusively, the morphing airfoil has proven to be advantageous in terms of aeroacoustics, in which the noise has been reduced with respect to the conventional high-lift configuration for a comparable lift coefficient, despite being hampered by a significant drag coefficient increase due to stall on the morphing airfoil’s trailing edge.

An Urban Flooding Index for Unsupervised Inundated Urban Area Detection Using Sentinel-1 Polarimetric SAR Images

Urban flooding causes a variation in radar return from urban areas. However, such variation has not been thoroughly examined for different polarizations because of the lack of polarimetric SAR (PolSAR) images and ground truth data simultaneously collected over flooded urban areas. This condition hinders not only the understanding of the effect mechanism of urban flooding under different polarizations but also the development of advanced methods that could improve the accuracy of inundated urban area detection. Using Sentinel-1 PolSAR and Jilin-1 high-resolution optical images acquired on the same day over flooded urban areas in Golestan, Iran, this study investigated the characteristics and mechanisms of the radar return changes induced by urban flooding under different polarizations and proposed a new method for unsupervised inundated urban area detection. This study found that urban flooding caused a backscattering coefficient increase (BCI) and interferometric coherence decrease (ICD) in VV and VH polarizations. Furthermore, VV polarization was more sensitive to the BCI and ICD than VH polarization. In light of these findings, the ratio between the BCI and ICD was defined as an urban flooding index (UFI), and the UFI in VV polarization was used for the unsupervised detection of flooded urban areas. The overall accuracy, detection accuracy, and false alarm rate attained by the UFI-based method were 96.93%, 91.09%, and 0.95%, respectively. Compared with the conventional unsupervised method based on the ICD and that based on the fusion of backscattering coefficients and interferometric coherences (FBI), the UFI-based method achieved higher overall accuracy. The performance of VV was evaluated and compared to that of VH in the flooded urban area detection using the UFI-, ICD-, and FBI-based methods, respectively. VV polarization produced higher overall accuracy than VH polarization in all the methods, especially in the UFI-based method. By using VV instead of VH polarization, the UFI-based method improved the detection accuracy by 38.16%. These results indicated that the UFI-based method improved flooded urban area detection by synergizing the BCI and ICD in VV polarization.

Lanthanum Diffusion in Fluorapatite at 400 °C, 50 MPa and 4–16 wt %

Apatite is an important carrier of rare earth elements (REEs) and phosphorite is a potential REEs resource. However, the influence of hydrothermal fluids on the migration and enrichment of REE in apatite remains controversial. The experimental study of the interaction between REE-bearing fluid and apatite is one of the essential ways to understand the chemical behavior of rare earth elements in apatite. In this study, we conducted the fluid–mineral reaction experimental study (at 400 °C, 50 MPa and 4–16 wt %) between high lanthanum (La) content hydrothermal solution and low REE content to reveal the influence of different salinities on the diffusion of rare earth elements in fluorapatite. Based on in situ geochemical analyses of experimental products, we show that the diffusion coefficients of La in fluorapatite are between 3.24 × 10−15 and 5.88 × 10−15 m2/s. The salinity of the fluid has a great influence on the diffusion coefficient, with the increase of salinity, the diffusion coefficient increase.

Drag coefficients of air rifle pellets with wide range of geometries

Air rifle and air pistol target shooting are included in major intentional and national sports competitions and are also highly popular sport pastimes. Published scientific studies of pellet drag are very rare, in contrast to a large number of scientific studies published on aerodynamic drag of sports balls and other sports projectiles. Measurements are presented of the drag coefficients for 31 air rifle pellets of mainly 4.5 mm (0.177 in) calibre having a wide range of geometries. The drag coefficient measurements were made with a low-turbulence open wind tunnel at flow velocity of 200 m/s (Mach and Reynolds numbers 0.57 and 56,000 for 4.5 mm pellets). The detailed geometry of some pellets was altered systematically in order to improve understanding of how pellet geometry affects drag coefficient. The drag coefficient for the 31 pellets varied widely from 0.36 to 0.78, and it was influenced substantially by the curvature of the flow separating from the pellet head rim. Large curvatures delayed flow re-attachment onto the pellet tail, thereby lowering pellet base pressure and increasing the value of drag coefficient. Pellets with hemi-spherical or ogive-shaped noses generally had lower values of drag coefficient than pellets with other nose shapes. The presence of the pellet tail was beneficial by providing a surface onto which the flow detaching from the pellet rim could re-attach. However, for minimisation of drag coefficient, the pellet tail had to be of a certain optimum length which depended on the shape of the pellet nose. Small differences in pellet geometry had significant influence on the value of drag coefficient. Increase in air velocity from 120 to 200 m/s had small influence on the value of drag coefficient for three common sports pellets having flat, conical and dome-shaped noses.

Convolution Neural Network Architectures for Motor Imagery EEG Signal Classification

This paper has made a survey on motor imagery EEG signals and different classifiers to analyze them. Resolution for medical images like CT, MRI can be improved using deep sense CNN and improved resolution technology. Drowsiness of a student can be analyzed using deep CNN and it helps in teaching, assessment of the student. The authors have proposed 1D-CNN with 2 layers and 3 layers architecture to classify EEG signal for eyes open and eyes closed conditions. Various activation functions and combinations are tried for 2-layer 1D-CNN. Similarly, various loss models are applied in compile model to check the CNN performance. Simulation is carried out using Python 2.7 and 1D-CNN with 3 layers show better performance as it increases number of training parameters by increasing number of layers in the architecture. Accuracy and kappa coefficient increase whereas hamming loss and logloss decreases by increasing number of layers in CNN architecture.

CFD Investigation of A New Elliptical-Bladed Multistage Savonius Rotors

The Savonius-conventional wind turbine is a class of wind turbines designed with a vertical axis. It has a good starting capacity and an insensitivity to wind direction. It works relatively at low wind speed in an easy installation. Savonius wind turbine faces major drawbacks, including some of the low efficiency and high negative torque created by the returning blade. Many attempts have been undertaken to optimize the blade’s shape to increase the performance of these wind turbines. The vertical axis is still under development. The elliptical-blades with a cut angle equal 47.50° have recently shown enhanced performance. In this study, we investigate the effect of Elliptical-bladed multistage Savonius Rotors (rotor aspect ratio, stage aspect ratio) on the performance by means of numerical simulation. The results obtained by comparison of one, two, and three-stage rotors indicate that the maximum power coefficient increase with a number of the stages (for the rotors with similar RAR of 0.7). Moreover, for the rotors with similar SAR of 0.7, the two stages have the highest performance than others.©2020. CBIORE-IJRED. All rights reserved

Numerical Analysis of the Aerodynamic Characteristics of NACA-4312 Airfoil

The aim of the work is to investigate the aerodynamic characteristics such as lift coefficient, drag coefficient, pressure distribution over a surface of an airfoil of NACA-4312. A commercial software ANSYS Fluent was used for these numerical simulations to calculate the aerodynamic characteristics of 2-D NACA-4312 airfoil at different angles of attack (α) at fixed Reynolds number (Re), equal to 5×10^5 . These simulations were solved using two different turbulence models, one was the Standard k-ε model with enhanced wall treatment and other was the SST k-ω model. Numerical results demonstrate that both models can produce similar results with little deviations. It was observed that both lift and drag coefficient increase at higher angles of attack, however lift coefficient starts to reduce at α =13° which is known as stalling condition. Numerical results also show that flow separations start at rare edge when the angle of attack is higher than 13° due to the reduction of lift coefficient.

INVESTIGATION OF TEMPERATURE OF BRAKE PADS WITH DIFFERENT EXTENT OF WEAR IN FRICTIONAL BRAKING

The issue of railway rolling stock brake pad heating is examined under frictional braking within a freight car with unilateral push, equipped with castiron brake pads. Foreign and domestic experience of studies of heat cycles caused by friction has been examined, mechanism of heat release in the contact zone between a pad and wheel during braking with consideration of a heat flow distribution coefficient is described, mathematical modeling choice as a way to refine temperature measurements in the process of experimental studies is grounded, the results of estimated determination of the thermal flow affecting the pad in braking of a loaded freight car weighing 93 ts with 5 ts push upon the axle from 60 km/h to full stop are shown. Dynamics of thermal energy change emitting in frictional braking with consideration of wheel rotation decelerating speed and friction coefficient increase is emulated. Finite element models of pads with even wear, wedgelike wear and with no wear having geometry of relevant engineering drawings are described. The results of investigation of heating of brake pads with different wear types in the process of braking until full stop are given.