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Global spectral analysis for convection-diffusion-reaction equation in one and two-dimensions: Effects of numerical anti-diffusion and dispersion
No full textConvection-diffusion-reaction (CDR) equation plays a central role in many disciplines of engineering, science and finances. As a consequence, importance of analysis of numerical methods for the accurate solution of CDR equation has motivated the present research. We have used the global spectral analysis to characterize all the three important physical processes in terms of the non-dimensional numerical parameters, namely, the non-dimensional wavenumber (kh); Courant-Friedrich-Lewy (CFL) number, ; the Peclet number (Pe) and the Damkohler number (Da). For the purpose of illustration, we have focused on two space-time discretization schemes known for accuracy and robustness. The basic properties relate to numerical issues arising for the numerical amplification factor, numerical diffusion coefficient, numerical phase speed and numerical group velocity. With the help of model one-dimensional (1D) and two-dimensional (2D) CDR equations, we have reported the numerical property charts for the cases: (i) When all the processes of convection, diffusion and reaction are of same order, with critical numerical behaviour enforcing low values of Da for the 1D CDR equation studied here. (ii) The 2D CDR equation considered is diffusion-reaction dominated, and as a consequence, this enforces Da to be larger. We have thoroughly analyzed these cases to identify the essential roles of anti-diffusion on the critical and Pe values, which in turn decides admissible space and time steps to be used with the discretization schemes. The property charts have been used to calibrate the analysis with two model equations, one of which has an exact solution for a 1D CDR equation, and the second case for the 2D CDR equation has numerical solution available in the literature. These cases help to identify the importance of such analysis in explaining the utility of the choice one can exercise in fixing the numerical parameters. This also identifies and explains some hitherto unknown numerical problems for CDR equation and their alleviation techniques
Design and Analysis of an Agriculture Solar Panel Support Structure with Tilting Mechanisms.
No full textThe requirements for solar water pumping system in the agriculture are increased day by day. The performance of the solar electrical power generating system entirely depends on the structural stability of the supporting system. In this paper, an eight-panel solar supporting system is designed and analyzed for its structural efficiency for the high wind loads. The finite-element-based structural analysis is performed using the software package for different tilt positions through tilting mechanism used for everyday application and for the seasonal variation of the sun rays’ direction. Quadrilateral and triangular beam elements are used for the mesh generation of the support structure, and the CBUSH and RBE2 are used to model the bolt joints. The wind load is applied as pressure, and the self-weight of the solar panel is applied as a lumped mass and transferred to the main structure through rigid element. The static analysis is performed for the wind loads for the three tilting positions. The results are conforming that the main structural stresses and deformations are within the limits
Co-fired anode-supported solid oxide fuel cell for internal reforming of hydrocarbon fuel.
No full textHydrocarbon-based solid oxide fuel cell (SOFC) is being projected as one of the possible alternatives to conventional internal combustion engines. However, the conventional Ni–YSZ anode is prone to carburization in the presence of hydrocarbon fuels. In the present study, an optimized Ni–Cu-based anode composition (Ni0.9–Cu0.1–YSZ0.95–GDC0.05) has been evolved based on accelerated carburization studies and phase analysis by X-ray diffractometry and X-ray photoelectron spectroscopy. The electrochemical parameters have been derived for the optimized anode composition, and its exchange current density is estimated to be 76.3 mA cm−2 at 780 °C. The main advantage of the optimized anode is its suitability for co-firing with the electrolyte. Using the optimized anode composition, anode-supported SOFC single cells (ASCs) have been fabricated and their electrical and electrochemical performances have been evaluated and compared with conventional ASC. The anode-supported co-cast SOFC with the optimized anode composition exhibits a power density of 436 mW cm−2 at 850 °C and 0.5 V with methane as fuel
Rudimentary emulation of covert feathers on low-ar wings for poststall lift enhancement.
No full textCovert feathers, a group of feathers on the upper surface of bird wings, are one of birds’ features that aid them in
flight at high angles of attack, making them more maneuverable. In a previous study, the authors found that a
rudimentary emulation of this feature (termed a self-adaptive flap) enhances the poststall lift characteristics of low-aspect-ratio flat-plate wings at Re � 100;000. This enhancement, however, was found to vary with the different
chordwise locations of the flap and across different planforms. In a continued effort to understand this further,
two-dimensional particle image velocimetry investigation was carried out in the midspan plane of the low-aspect-ratio
wings. For the varying-span elliptical wings, the results reveal that the flap/shear layer interaction promotes
reattachment of the separated shear layer via increased entrainment. This reattachment location varies for the
different chordwise location of the flap, resulting in a different extent of the separation bubble and bubble-induced
camber, which in turn is responsible for different poststall lift enhancement. On the other hand, for the rectangular
wing, the flap promotes large-scale vortex formation. The formation and shedding cycle of large-scale vortices has a
significant impact on the mean-body forces because of which the time-averaged poststall lift is enhanced
Citrate combustion synthesized Al-doped CaCu3Ti4O12 quadruple perovskite: synthesis, characterization and multifunctional properties
No full textThe facile synthesis of the Al-doped CaCu3Ti4O12 quadruple perovskite, a well-known and vastly studied material for various technological applications, using the modified citrate combustion route along with structural, microstructural, and X-ray photoelectron spectroscopic (XPS) characterization and magnetic, dielectric and electrical properties has been investigated and reported here. The possible applications of the material as a Schottky barrier diode (SBD) in optoelectronic devices and as a catalyst in methanol steam reforming (MSR) reaction for hydrogen generation, hitherto unreported in the open literature, have also been explored. The compound is crystallized in the cubic body centered Im[3 with combining macron] space group and the particle size is found to be in nanodimension with rather narrow size distribution. The enhanced resistivity could be attributed to the grain boundary effect, and consequently, it exhibits better performance as a SBD compared to the undoped sample. Desired cationic composition with expected valence states within the probe range is confirmed by XPS analysis. A better catalytic activity towards MSR is noticed for the Al-doped CaCu3Ti4O12 compared to the undoped composition. These new findings, namely MSR activity and applicability in the Schottky device, have highlighted further the multifunctional nature of the material in energy related issues and would thus be of interest to the materials community searching for functional materials
Rankine vortex formation during draining: A new twin port suppression strategy.
No full textThis paper reveals the results of a study of vortex air core formation (Rankine vortex) when a rotated liquid (water) column in a cylindrical vessel is drained through two ports located at equal eccentricity (e) at the vessel base (diameter, d1and d2) simultaneously; d1is fixed whereas d2 is varied. Just before draining, a rotation (n rpm) is provided to the liquid column in controlled conditions. As draining progresses, when the liquid level reaches certain height called critical height (hc), initially a surface dip forms which further develops in to a vortex extending down till the drain port. Results show that critical height increases as the fluid rotation rate increases at the lowest eccentricity. But, at higher eccentricities, hc, exhibits more or less an increasing decreasing trend in most of the cases studied. Critical height is observed to be minimum for the largest value of d2 (equal to d1) irrespective of the values of the speed of fluid rotation, liquid initial height and port eccentricity. To particularly note, at the highest eccentricity, vortex formation is found to be completely suppressed for all values of port diameter (d2) and initial fluid rotation (n) as indicated by the near-zero critical height values. The tangential velocity measurements using Particle Image Velocimetry are also reported. PIV results obtained for certain cases with induced fluid rotation (normal draining and faster draining) correlate well with the changes in the efflux (axial) velocity (deduced analytically) in these cases studied. The tangential velocity along radial direction obtained (PIV) also indicated the type of vortex formed in normal and faster draining cases. Video visualization of vortex formation carried out reveals that, vortex air core switching takes place between the drain ports maintaining an arched or curvilinear surface profile apart from demonstrating the nature of outlet flow discharge. All the vortex air core formation studies so far carried out were invariably with single drain port except the preliminary novel study by the same author group and the present study is a detailed extension of that novel study
Effect of incident microwave frequency on curing process of polymer matrix composites
No full textMicrowave assisted curing of aerospace and structural polymer matrix composites depends on several factors such as dielectric properties of the curing substrate, type of tooling used, thickness of the composite part, kind of applicator chosen and so on but one of the most important factors is the frequency of radiation used for the purpose of curing. Majority of the work reported on microwave curing of polymer composites is restricted to the commonly utilized frequency of 2450 MHz, whereas 915 MHz frequency is extensively employed chiefly for food processing and wood drying applications. This paper evaluates the potential of 915 MHz frequency for curing polymer matrix composites.
2 mm thick glass-epoxy composite laminates were prepared using bi-directional glass fiber reinforced epoxy resin system. These composites were then cured in three different ways: microwave curing with 915 MHz as incident microwave frequency; microwave curing with 2450 MHz as incident microwave frequency and conventional thermal (oven) curing. Comparison between microwave and thermal cure process times as well as energy consumption revealed the significant time and energy savings realized by microwave curing. Further, mutual comparison of the cured laminates was drawn in terms of attainment of lamination quality, glass transition temperature and mechanical properties. The results obtained showed that the 915 MHz microwave cured laminate had superior inter-laminar shear strength (ILSS) and flexural strength as compared to 2450 MHz microwave cured and thermally cured laminates. This, in essence, implies that incident microwave frequency plays a crucial role in designing cure process parameters for polymer matrix composites
Interaction of convective organization with monsoon precipitation, atmosphere, surface and sea: The 2016 INCOMPASS field campaign in India
No full textThe INCOMPASS field campaign combines airborne and ground measurements of the 2016 Indian monsoon, towards the ultimate goal of better predicting monsoon rainfall. The monsoon supplies the majority of water in South Asia, but forecasting from days to the season ahead is limited by large, rapidly developing errors in model parametrizations. The lack of detailed observations prevents thorough understanding of the monsoon circulation and its interaction with the land surface: a process governed by boundary-layer and convective-cloud dynamics. INCOMPASS used the UK Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 aircraft for the first project of this scale in India, to accrue almost 100 h of observations in June and July 2016. Flights from Lucknow in the northern plains sampled the dramatic contrast in surface and boundarylayer structures between dry desert air in the west and the humid environment over the northern Bay of Bengal. These flights were repeated in pre-monsoon and monsoon conditions. Flights from a second base at Bengaluru in southern India measured atmospheric contrasts from the Arabian Sea, over the Western Ghats mountains, to the rain shadow of southeast India and the south Bay of Bengal. Flight planning was aided by forecasts from bespoke 4 km convection-permitting limitedarea models at the Met Office and India's NCMRWF. On the ground, INCOMPASS installed eddycovariance flux towers on a range of surface types, to provide detailed measurements of surface fluxes and their modulation by diurnal and seasonal cycles. These data will be used to better quantify the impacts of the atmosphere on the land surface, and vice versa. INCOMPASS also installed ground instrumentation supersites at Kanpur and Bhubaneswar. Here we motivate and describe the INCOMPASS field campaign. We use examples from two flights to illustrate contrasts in atmospheric structure, in particular the retreating mid-level dry intrusion during the monsoon onset
Solid particle erosion and corrosion resistance performance of nanolayered multilayered Ti/TiN and TiAl/TiAlN coatings deposited on Ti6Al4V substrates
No full textSolid particle erosion by air born dust particles and corrosion by humid air and sea salt cause severe damage to the gas turbine blades and wind turbines. Combination of erosion and corrosion accelerates the damage process compared to the individual effects. The damage leads to the economic loss, pollution and low safety. In order to protect these components, ultra-thin multilayered erosion and corrosion resistant Ti/TiN and TiAl/TiAlN coatings with stress absorbing layers were developed on Ti6Al4V substrates using un-balanced magnetron sputtering process. Erosion resistance of Ti/TiN and TiAl/TiAlN coatings was tested according to the ASTM-G76-13 standards at four different impinging angles: 90°, 60°, 45° and 30°. Erosion tests were conducted at 400 °C with increasing erodent velocity (30 to 90 m/s) using alumina and silica erodent particles. Average erosion resistance of Ti/TiN and TiAl/TiAlN coatings was significantly higher than Ti6Al4V substrate. Corrosion resistance of the coatings was found to be almost one order better than Ti6Al4V substrate in 3.5% NaCl solution. Morphology and spectroscopic analysis of the erosion scars were studied using field emission scanning electron microscopy and micro-Raman spectroscopy, respectively. Chemical stability of TiAl/TiAlN was found to be better than Ti/TiN in 3.5% NaCl solution
Influence of heat treatment on near-threshold fatigue crack growth behavior of high strength aluminum alloy 7010.
No full textIn this study, aluminum alloy 7010 was subjected to three different ageing treatments i.e., peak ageing (T6), over ageing (T7451) and retrogression and re-ageing (RRA) to study the influence of precipitate microstructure on the fatigue crack growth rate (FCGR) behavior. The microstructural modifications were studied by using TEM to examine the change in size and morphology of the precipitates. The size of the precipitates in the matrix range from 16–20 nm in T7451, 5–6 nm in RRA and 2–3 nm in T6 alloys, respectively. The FCGR tests were performed on standard compact tension (CT) specimens as per ASTM E647 standard in a computer controlled servo-hydraulic test machine with applied stress ratio, R = 0.1 and loading frequency of 10 Hz. The crack growth was measured by adopting compliance technique using a CMOD gauge attached to the CT specimen. The fatigue crack growth rate was higher in T7451 and lowest in RRA treated alloy. The RRA treated alloy showed higher ∆Kth compared to T7451 and T6 treated alloys. The measured ∆Kth was 11.1, 10.3 and 5.7 MPam½ in RRA, T6 and T7451 alloys, respectively. In the near-threshold regime, the RRA treated alloy exhibited nearly 2–3 times reduction in the crack growth rate compared to the T6 alloy. The growth rate in the RRA alloy was one order lower than that of the T7451 condition. The surface roughness of RRA treated alloy was more pronounced. The reduction in FCGR observed in RRA alloy was correlated to partial crack closure due to tortuous crack path and partially due to increased spacing between the matrix precipitates. The reduction in near-threshold FCGR and increase in ∆Kth is expected to benefit the damage tolerant capability of the aircraft structural components under service loads