R, Arun Kumar

Accurate prediction of material properties is essential in structural engineering design to ensure reliability and safety. Traditional approaches often rely on Gaussian distributions to model material variability. However, our research reveals limitations with Gaussian assumptions, particularly when covariance parameters exceed certain thresholds, leading to physically unrealistic negative values for material properties. To overcome these limitations, we investigate an alternative approach using lognormal distributions for material property modeling. Through Monte Carlo simulations employing Cholesky decomposition, we compare the performance of lognormal distributions with Gaussian counterparts. Our findings demonstrate that lognormal distributions offer a viable alternative, providing more accurate representations of material variability while maintaining computational efficiency. Furthermore, we utilize finite element method (FEM) data from Monte Carlo simulations to predict beam deflection using deep neural networks (DNNs). Leveraging inverse modeling techniques, we showcase the ability to predict elastic modulus from beam deflection data under both normal and lognormal distribution assumptions. By integrating lognormal modeling and inverse modeling techniques into structural analysis, we enhance the realism and accuracy of predictions, thereby improving reliability in engineering design. This paper discusses the implications of our findings and emphasizes the importance of considering alternative probability distributions for material property modeling in structural engineering applications.

The inclined impinging jets owing to higher efficiency are widely used to disperse concentrated and transient heat loads. The temperature and heat transfer characteristics of jet cooling vertical hot plate at different inclinations are experimentally investigated. Experiments are performed to investigate the area average heat transfer over a flat surface of 600 × 300 mm2 placed at different location (z) of 3−20 d from the jet. The investigation is employed for Reynolds number based on hydraulic diameter of 11.5 mm ranging from 10,000 to 75,000. The orientation of the jet varies from 15° to 75°. The study aims to investigate the influence of jet orientation at different area locations on the surface from the point of impingement. The effect in stagnation region with different jet tilt is investigated. The area average temperature variation and characteristic temperature contours with increasing surface area and inclination is delineated. The characteristics of heat transfer on the surface’s periphery are studied. Heat transfer increases by 40% at lower tilt angle as the jet is displaced from 20 to 6 d, whereas the maximum average Nu occurs at higher inclination. The available Nusselt numbers in inclined jet are compared with present experimental results. A new empirical correlation is developed for a complete range of z/d, Re and large radial span.

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This study explores the flow physics and mixing characteristics produced by the interaction of two transversally injected jets along the spanwise direction with a supersonic crossflow using experimental and numerical techniques. Results show that smaller interjet spacing reduces the crossflow entrainment from the top into the interjet region, while wider spacing facilitates greater entrainment. The investigation further reveals that the gap created by the two injected jets allows the crossflow to decelerate and then accelerate to a higher supersonic Mach number as it flows along the interjet region. Investigation of the shock structures revealed that in the case of smaller interjet spacing, the strong part of the two bow shocks created by the transverse jets interacts with each other, whereas with large interjet spacing, the weak part of the two bow shock waves interacts. This leads to a larger local pressure jump in the interjet spacing with a smaller injector gap than the larger one. Various streamwise vortices, such as horseshoe and counter-rotating vortex pairs (CVPs), are seen to form for spanwise tandem injection in crossflow. The interaction of such vortices is seen to be significant in the case with smaller injector spacing compared to the larger one. The oil flow visualization reveals the formation of a herringbone-shaped separation region in the wake of the jets, and the size of this separation zone diminishes with the reduction in injector spacing. The mixing characteristics investigated using Mie scattering and computations reveal that with an increase in injector spacing, the mixing efficiency increases.

This study investigates the fluid dynamics and mixing characteristics of an oscillating sonic jet injected into a supersonic cross flow of Mach 2.1 using experimental and computational techniques. The oscillating jet is produced by a novel fluidic oscillator, which consists of a primary rectangular duct that expands into an outer duct with sudden expansion. Control jets are injected in the lateral direction from the side walls of the sudden expansion in an out-of-phase manner to oscillate the injected jet in the spanwise direction of the crossflow. Experimental and numerical investigations based on wall static pressure and mass fraction fluctuations, respectively, revealed that the injected jet oscillation frequency matches the control jet frequency. The iso-surface of lambda-2 criterion showed the presence of various dominant vortex structures, such as counter-rotating vortex pairs, horseshoe vortex, sidewall vortices, and trailing vortices. Helicity contour plots showed that the streamwise vortices oscillate in the spanwise direction with the control strategy and promote the spread of the injected jet in the spanwise direction. The spatiotemporal reconstruction (z-t plot) of the density gradients at a particular streamwise location revealed that the bow shock produced by the interaction of the injected jet and the crossflow oscillates with the actuation of the control strategy. The power spectral density of the z-t plot revealed that the shock wave oscillation frequency matches the control jet frequency. The oscillating jet produced by the control strategy showed significant mixing enhancement in supersonic crossflow compared to a simple rectangular injection.

The study focused on examining the area-averaged heat transfer characteristics of an air jet impinging on a concave surface. The experiments involved varying the Reynolds number (Re) within the range of 10,000 to 75,000, while adjusting the jet-to-plate distance from 3 to 20 times the jet diameter (d). The experimental setup included a jet with a diameter of 11.5 mm, and concave surfaces with curvature radii of 218 mm (Curvature ratio (Cr) = 0.026) and 281 mm (Cr = 0.021) were used. A detailed investigation was conducted using Infrared Thermography to measure the average Heat Transfer Coefficient (HTC) of jet impingement on these concave surfaces. The aim was to assess the impact of surface curvature on heat transfer at different locations from the impingement point. Additionally, the research compared the heat transfer effects in circular and square impingement regions that were identical in radial span and area ratios. It was observed that the area-averaged Nusselt number (Nu) generally increased with a higher Re and a lower jet-to-plate distance ratio (z/d). A maximum average Nu increase is observed for Cr = 0.026 when the mass flow rate is from 10,000 to 75,000. Increasing the curvature is an effective approach to provide localized cooling. A correlation comparison was also conducted, and a new empirical correlation has been proposed. This correlation works effectively across various ranges of Re, z/d, Cr, and radial position (r/d) with a deviation of less than ± 11%. Graphical Abstract: (Figure presented.)

Early diagnoses of Alzheimer's disease (AD) and pancreatic cancer (PC) are crucially important for the start of prognosis seeking the curing and saving of human lives. The present investigation aims to computational design materials having high selectivity towards the detection AD and PC biomarkers. Density functional theory (DFT) is explored to investigate the selective adsorption of pristine and metal-doped β12-borophene towards the volatile organic compounds (VOCs), related to AD or PC and well-known to exist in the exhaled breath of patients. Six VOCs were considered in our study; namely, (i) Three AD VOCs: 2,3-Dimethylheptane (2,3-DMH), Butylatehydroxytoluene (BHT), and Pivalic Acid (PVA); and (ii) Three PC VOCs: 2-pentanone (2p-none), 4-ethyl-1–2dimethyl benzene (4E-1,2-DMB), and n-nonanol (n-nonal). Pristine β12-borophene demonstrated selective adsorptions towards the six VOCs compared to the interfering air molecules (N2, O2, CO2, H2O) with adsorption energies at order [-0.85, -0.45] eV compared to [-0.20, -0.10], respectively. To enhance further the adsorption energies of VOCs and consequently the selectivity, the embedment of metal atoms in the small pores of β12-borophene monolayer has been explored. It is found that small-sized atoms such as alkali metal (Li) can be stably accommodated and yield large dipole moments to enhance the van der Waals interactions. For instance, using single-atom catalyst (SAC) of Li, the adsorption energies with VOCs were enhanced to become of magnitudes at order of 1.0 – 1.6 eV. While the magnetic state was maintained robust paramagnetic, the strong interactions with VOCs affected the recovery time to become huge. The SAC-Li doped β12-borophene can be proposed as candidate material for a platform of disposable nano biosensor with high sensor response to detect AD and PC biomarkers and consequently to contribute to the early diagnosis of these hazardous diseases. PACS Numbers: 31.15.E-, 68.43.-h, 68.43.Fg, 82.33.Pt, 87.15.Aa, 87.15.Kg, 87.19.Xx, 87.19.xj © 2025 Elsevier B.V.

Numerical simulations were performed to investigate the thermal and aerodynamic characteristics of an annular jet impinging on a concave surface using the Realizable k-ε model. The study examined the significance of the blockage ratio (BR) from 0.3 to 0.7 and the jet exit Reynolds number (Re) from 5000 to 35000. The investigation uses an annular jet with a 10 mm outer diameter impinging on a concave surface with 150 mm radii. Three specific dimensionless distances from the nozzle exit to the target surface (z/do) were considered: z/do = 0.5 (initial merging zone), z/do = 3 (intermediate merging zone), and z/do = 6 (fully merged zone). Furthermore, the annular jet’s performance was compared to that of a conventional circular jet under analogous conditions. At small separation distances, a pair of counter-rotating vortices formed downstream of the jet outlet, inducing a reverse flow that extended to the heated surface. Vortices and flow reversals were also identified at intermediate separation distances. At large separation distances, the flow reattached to the domain axis, resembling a circular jet. The local Nusselt number (Nu) increases as the Reynolds number increases and the blockage ratio decreases. With increasing BR, the difference between the primary and secondary Nu peaks reduces. Additionally, the average Nu and turbulent kinetic energy increase with an increase in Re.

A solar ejector technology-based system that combines refrigeration and desalination was investigated for the present study. The proposed model combined a conventional ejector refrigeration system with a desalination unit to examine its ability to achieve cooling as well as produce clean water. An analytical model of the ejector was developed using 1D compressible flow equations based on mass, momentum, and energy conservation. The output from the ejector was then fed to a 1D heat exchanger model to compute the clean water production. The analytical model was implemented using the Matlab platform. A 2D axisymmetric numerical simulation of the ejector system was also performed to comprehend the internal flow structures. It has been observed that the entrainment ratio, which is the ratio of the vapor refrigerant’s mass flow rate to the motive steam’s mass flow rate, falls as the stagnation temperature of the motive steam increases. It was noted that the coefficient of performance (COP) rises as the evaporator temperature rises, but it is seen to decline with the rise in generator temperature. The amount of desalinated water that can be produced with the system was also explored. It was observed that the production of desalinated water increased proportionally with the rise in generator temperature. At a generator temperature of 140◦ C, the system obtained clean water at a rate of about 2.9 g/s, which corresponds to a 24.5% mass flow rate of the input steam.

The flow boiling process in helical coils is investigated experimentally to analyze the effects of the orientation of the helical coil on the local heat transfer distribution, pressure drop and critical heat flux. The literature review suggests that little information is available on the influence of the orientation on the heat transfer distribution, pressure drop and critical flux during flow boiling in helical coils. Experiments are performed on horizontal and vertical helical coils with R123 as the working medium. SS-304 tubes of 5.5 mm and 7.5 mm diameter with a coil diameter of 150 mm are chosen in this study. Non-intrusive thermal imaging technique is used to measure the wall temperature. The differential pressure transmitter is used to measure the pressure drop across the test section. The two-phase pressure drop is not affected significantly by the orientation of the helical coils. The wall temperature, heat transfer distribution and the critical heat flux are affected by the orientation of the helical coil. The local and average heat transfer coefficient is higher in vertical oriented helical coils than the horizontal oriented helical coils. The value of heat flux at the burnout is higher in vertical orientation compared to horizontal orientation in both the coils.