Scramjet Intake Aerodynamic Studies Using Sharp Interface Immersed Boundary Method

In this present article, the use of a throttling device in the form of movable flap to study scramjet inlet unstart has been investigated numerically. The flap has been employed as an effort to simulate the rise in combustor pressure of the scramjet. Computational analysis for freestream Mach number and freestream pressure of and respectively, have been performed by a two-dimensional compressible CFD in-house Finite volume solver for perfect gas. Convective fluxes have been evaluated using AUSM scheme.Inviscidflow has been assumed for all the simulations. Particular point of interest in these simulations is the application of Immersed Boundary Method along the wall boundaries,enabling the use of structured grid for complex geometries. The results demarcate the starting condition of the inlet based on the flap throttling values. Comparative results in the form of Mach number and pressure contours are presented for different flap positions. The use of Immersed Boundary Method has been successfully displayed bysimulating a movable flap

High Strain Rate Modeling of CFRP Composite Under Compressive Loading

An in-depth understanding of how carbon fiber-reinforced plastics (CFRP) respond to intense strain rates is essential, particularly in non-linear deformation and dynamic loading situations. The researchers undertook a computational study to examine the behavior of CFRP composites when exposed to high strain rates under compressive loading. Specifically, they employed Split Hopkinson Pressure Bar models for cohesive interfacial simulations, continuum shell analysis, and laminated composites oriented at 0° at a strain rate equivalent to 900 s-1. The Finite Element model utilized a custom Hashin damage model and a vectorized user material (VUMAT) sub-routine to identify degradation damage within the CFRP composite model. The quasi-isotropic composite demonstrated a significant enhancement in dynamic strength compared to static values, attributed to its intense sensitivity to strain. As confirmed by experimental test results, numerical simulations accurately predicted stress (σ)-strain (ε) and strain rate (ἐ) curves. Additionally, it was observed that the relationship between damage behavior varied depending on the element type used

Optimized Mosaic Method for Accurate Measurement of Soot Concentration Indirect Method

Global air pollution poses health risks. Soot is a major contributor to warming and pollution. Measuring soot is key to mitigating emissions. This study proposes an empirical method using markers to indirectly gauge soot levels. The Mosaic method was tested against conventional techniques with over 50 samples. This method utilizes markers to collect impurities in the air, employing the µ/m³, m(g), and the newly devised Mosaic method. All results underwent standard statistical processing, enabling a comparison between the new method (Mosaic) and conventional techniques used

Understanding of MILD Combustion Characteristics of NH3 Air Flames in N2 And H2O Steam Diluted Environment at Atmospheric Pressure

Ammonia is becoming increasingly popular as a carbon-neutral fuel with zero carbon dioxide emissions. However, a significant hurdle lies in its combustion, which leads to substantial emissions of NOx. The current research involves conducting a chemical kinetic investigation to examine the characteristics of Intense Low oxygen Dilution (MILD) or Moderate combustion in ammonia (NH3)/air flames. This study is carried out under specific conditions, such as oxygen concentrations ranging from 11to 23%, premixed reactant temperatures between 1300 and 1700 K, and a pressure of one atmosphere. The study focuses on investigating the combustion characteristics of MILD using dilution with H2O and N2.With the rise in the inlet temperature of the premixed reactant, the peak temperature of the flame also rises. Moreover, flames diluted with H2O exhibit lower peak temperatures compared to flames diluted with N2.Flames diluted with H2O result in lower NOx emissions compared to flames diluted with N2. Additionally, for N2diluted flames, the exit NOx emissions rise as the oxygen concentration increases.Despite this, NOx emissions from H2Odiluted flames demonstrate non-monotonic behaviour.This means that the exit NOx increases initially as the oxygen concentration reaches 21%, but then begins to decrease. In contrast to N2and H2Odiluted flames exhibits a wider regime of no-ignition.Moreover, the rise in peak temperature in H2Odiluted flames is less apparent than in N2diluted flames, corresponding to broader ranges MILD combustion ranges.Furthermore, to attain MILD combustion in H2O diluted flames at a specific O2 concentration, the temperature of reactant needs to be higher than that required for N2diluted flames. &nbsp

Numerical Study on Mixing Characteristics of Circular and Non Circular Jets

The study of non-circular jet flows has become important due to their various applications such as aircraft exhaust, combustion chambers and injectors. The goal of present paper is to examine the impact of elliptical, square, and triangular shaped orifices on the mixing characteristics of a free jet with Mach number 0.8. Numerical simulations using an SST K-ω two-equation turbulence model were conducted with a Reynolds number of 3.46×105 for all cases. The mean velocity, decay rate, half-velocity width, spread rate, and turbulence intensity of the jet were analysed. The results showed that the triangular orifice provided the best mixing efficiency, with a shorter jet core length. The decay rate was found to be lowest for the square jet and highest for the triangular jet, which matches with the previous research. The asymmetric jets experienced two axis-switching points, while the square jet experienced a 450 rotation of its axes but no axis-switching. The core region had lower turbulence levels, while the highest turbulence levels were in the shear layer

Modelling of Human Factors in Aviation Maintenance Using HFACS ME Human Factors Analysis and Classification System Maintenance Extension and Bayesian Network

Aircraft maintenance is a complex task involving a skilled human workforce, spare parts, and various other resources. Human factors are an inherent element of the human workforce. Human factors analysis, therefore, becomes an essential aspect of aviation maintenance. Human factors have been identified and classified using various methods in existing literature. However, there is a gap in the study of the interdependency of critical human factors including subfactors, and measuring them effectively to reduce incidents and accidents. This research work proposed a novel approach for human factors modeling using human factors analysis and classification system maintenance extension (HFACS-ME), and bayesian network (BN). Inadequate maintenance processes, inadequate documentation, inadequate supervision, Judgement decision, and attention memory were identified as some of the critical human factors in aircraft maintenance. These critical human factors were further analysed and divided into subfactors. The main contribution of the present research work is the methodology of developing a dependency model of the human factors and subfactors to analyse their measured effects on aircraft maintenance. The proposed BN model demonstrated the estimation of the probability of effective maintenance by considering the critical human factors with available facilities, and resources in an aviation maintenance setup

Investigations on Penta Band High Isolation MIMO Antenna for 5G NR Bands and HIPERLAN Applications Using TCMA

The present article proposes a penta band Multiple Input Multiple Output (MIMO) antenna for 5G New Radio (NR) bands and HIPERLAN applications using Characteristic Mode Analysis (CMA). The design is obtained and optimised in step-by-step procedure using novel CMA approach and by perturbing the conventional rectangular structure with slots on the patch (left and right sides) and the ground plane (wide slot + narrow slots) for enhancing the isolation at multi bands. The MIMO configuration has a total dimension of 0.58 l0 × 0.35 l0 × 0.01 l0 mm3 with an optimum element separation of 0.05 l0 (l0 is the lowest frequency operating wavelength). Multiband resonance is produced at 2.2, 4.2, 7.2, 16, 17.5 GHz. The radiating elements can excite various characteristic modes that support wider bandwidth. The -10 dB impedance bandwidth at working region are 0.2, 0.2, 0.38, 3.6, 2 GHz respectively. The suggested design yields a gain of 2.1, 5.7, 3.5, 3.5, 5.2 dBi and consistent radiation patterns at the working frequencies. The analysis of the diversity performance considers the Diversity Gain (DG) and Envelope Correlation Coefficient (ECC), whose values are near 9.9 dB and 0, respectively. Additionally, the assessed parameters are the CCL and TARC. The structure prototype has been developed, and the observed findings are highly coherent with the simulated results, making it appropriate for use in 5G NR bands, HIPERLAN, and IoT applications

RAZOR A Lightweight Block Cipher for Security in IoT

Rapid technological developments prompted a need to do everything from anywhere and that is growing due to modern lifestyle. The Internet of Things (IoT) technology is helping to provide the solutions by inter-connecting the smart devices. Lightweight block ciphers are deployed to enable the security in such devices. In this paper, a new lightweight block cipher RAZOR is proposed that is based on a hybrid design technique. The round function of RAZOR is designed by mixing the Feistel and substitution permutation network techniques. The rotation and XOR based diffusion function is applied on 32-bit input with 8 branches and branch number 7 to optimize the security. The strength of RAZOR is proved against differential, linear, and impossible differential attacks. The number of active S-boxes in any 5-round differential characteristic of RAZOR is 21 in comparison to the 10, 6, 4, 7, and 6 for PRESENT, Rectangle, LBlock, GIFT, and SCENERY respectively. RAZOR provides better security than the existing lightweight designs. The average throughput of 1.47 mega bytes per second to encrypt the large files makes it a better choice for software oriented IoT applications

Analysis of the Brownian Motion Approach for Ballistic Resistance Evaluation Using the Maximum Likelihood Inference

Armor technologists’ improvement of protection systems led to the design of complex systems. Given the risk factor on human life, increasing requirements on the ballistic resistance evaluation are imposed. Consequently, an increased effort is dedicated to estimating the perforation probability curve as a function of the bullet impact velocity. The main limitation of methods that fits a normal law to perforation velocities is their purely statistical character. A Brownian-based approach that couples the system response variability and physics was proposed using the Chi-square and Kolmogorov-Smirnov criterion function for model parameters estimation. One major limitation of this inference approach is the large experimental database required for its execution. The contribution of this paper is the introduction of the maximum likelihood inference for parameters estimation of the Brownian-based approach. The agreement between the obtained results and the experimental ones confirms the appropriateness of the likelihood inference to solve the studied problem. Moreover, the estimations uncertainty was analyzed and compared to the existing method ones. It was observed that the proposed model reduces the confidence intervals on key velocity estimations. Accordingly, the present work encourages the adoption of this proposed methodology in a laboratory context with a restrained sample size