National Aerospace Laboratories

About: National Aerospace Laboratories is a facility organization based out in Bengaluru, India. It is known for research contribution in the topics: Coating & Corrosion. The organization has 1838 authors who have published 2349 publications receiving 36888 citations.

Silver as a dopant and as a constituent in AsAgTe glasses: mean atomic volume and Tg

Abstract: The variations of the mean atomic volume, V , the glass transition temperature, T g , and the activation energy for glass transition, E t , with composition have been reported for (As 2 Te 3 ) 1 − x Ag x and (As 2 Te 3 )(Ag 2 Te) glasses; the glasses were prepared by a two-stage melt-quenching method. For the (As 2 Te 3 ) 1− x Ag x glasses, changes in the nature of dependences of V , T g and E t occur at the composition with Ag content of 1 atomic per cent (at.%). Analysis of these results indicates that, for Ag contents ≤ 1 at.%, Ag particles are uniformly dispersed in the network of the As 2 Te 3 glass, without affecting either the short range or the medium range order of the parent glass. For Ag contents ≥ 3.5 at.%, Ag forms AgTe bonds, and the observed variation of the properties can be explained by assuming the resulting three component glasses to be homogeneous mixtures of (As 2 Te 3 ) and (Ag 2 Te) units.

Interaction of convective organization with monsoon precipitation, atmosphere, surface and sea: The 2016 INCOMPASS field campaign in India

Abstract: The 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 boundary‐layer 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 limited‐area models at the Met Office and India's NCMRWF. On the ground, INCOMPASS installed eddy‐covariance 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.

Description of the F-16XL Geometry and Computational Grids Used in CAWAPI

Abstract: The objective of the Cranked-Arrow Wing Aerodynamics Project International (CAWAPI) was to allow a comprehensive validation of Computational Fluid Dynamics methods against the CAWAP flight database. A major part of this work involved the generation of high-quality computational grids. Prior to the grid generation an IGES file containing the air-tight geometry of the F-16XL aircraft was generated by a cooperation of the CAWAPI partners. Based on this geometry description both structured and unstructured grids have been generated. The baseline structured (multi-block) grid (and a family of derived grids) has been generated by the National Aerospace Laboratory NLR. Although the algorithms used by NLR had become available just before CAWAPI and thus only a limited experience with their application to such a complex configuration had been gained, a grid of good quality was generated well within four weeks. This time compared favourably with that required to produce the unstructured grids in CAWAPI. The baseline all-tetrahedral and hybrid unstructured grids has been generated at NASA Langley Research Center and the USAFA, respectively. To provide more geometrical resolution, trimmed unstructured grids have been generated at EADS-MAS, the UTSimCenter, Boeing Phantom Works and KTH/FOI. All grids generated within the framework of CAWAPI will be discussed in the article. Both results obtained on the structured grids and the unstructured grids showed a significant improvement in agreement with flight test data in comparison with those obtained on the structured multi-block grid used during CAWAP.

Straightforward inversion of vertical electrical sounding data

Abstract: A straightforward inversion scheme (SIS) has been developed to interpret vertical electrical sounding data. This scheme does not require quasi-linearization of the inverse resistivity problem and thereby dispenses with the iterative process and the necessity of guessing the number of layers and their resistivities and thicknesses. The entire solution domain is divided into uniform thickness layers, whose scale must be judiciously selected for the desired resolution. The apparent resistivity formula can now be posed as an underdetermined matrix equation whose minimum norm solution is downward continued to obtain the reflection coefficients which, in turn, yield the vertical resistivity distribution. A recurrence relation has been developed especially for this purpose. In general, when data are expected to be noisy, a regressed minimum norm solution is used. Exhaustive tests of the algorithm have established its numerical efficiency. Results of six typical synthetic models, representing diverse geological conditions, as well as results of two field examples are included to demonstrate this claim.

Bending Behavior of Hybrid-Actuated Piezoelectric Sandwich Beams

Abstract: The finite element analysis is presented for hybrid-actuated piezoelectric sandwich beam structures. The hybrid actuation is modelled by incorporating a transversely polarized, d31-based extension actuation lamina and an axially polarized, d15-based shear actuation lamina. Further the bending behavior of sandwich beams are evaluated for various boundary conditions with segmented actuators. The active stiffening effect is assessed through bending deflection behavior. The extension and shear actuators are collocated as well as non-collocated along the length of beam to see the combined actuation effort. It is observed that for the clamped-free case, the actuation effect is augmented with collocated actuators; however this trend is not followed in the other cases. Interestingly, the non-collocated actuators show better cumulative actuation effort for different boundary conditions except in the hinged-hinged case, where shear actuation appears to be predominant. As extension and shear actuations have distinctive features, both can be employed in a non-collocated fashion for better control action.