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.

The eduction of structures from flow imagery using wavelets Part I. The mixing layer

Abstract: Using two-dimensional Mexican hat wavelets, digitized imagery from the flow visualization pictures of a mixing layer by Brown and Roshko have been analysed. The objective of the present study is to “calibrate” the proposed wavelet technique for educing structures in a flow whose large-scale organization is well established. It is found that, with appropriate thresholds on wavelet-transform coefficients, considerable insight into the structure of the flow at different scales can be obtained. In particular, the analysis reveals that the small-scale structure within the large-scale vortices is approximately homogeneous, and has characteristic scales that do not vary significantly with downstream distance.

Damping Characteristics of Epoxy-Reinforced Composite with Multiwall Carbon Nanotubes

Abstract: In the current work, the damping characteristics of epoxy-reinforced composite with multiwall carbon nanotubes (MWNTs) have been investigated. The effect of reinforcement weight percentage and the influence of carbon nanotube (CNT) sizes on the damping are examined. The frequency dependent damping behavior of nanocomposites has been evaluated. A nearly 85% increase in loss modulus is observed for nanocomposites reinforced with CNTs of high specific surface area (SSA) against 53% with CNTs of lower aspect ratio and SSA at 0.75% filler percentage. Hence, it is evident that CNTs with a high aspect ratio and SSA are very effective in improving the damping behavior of polymer composites. An increase in storage modulus of about 10% is noticed at 0.5% CNT filler percentage followed by a marginal reduction at 0.75%, which clearly indicates that the percentage of reinforcement plays a major role in enhancing the stiffness properties. Interestingly, the CNT nanocomposites have been found to exhibit better damping c...

Comparative Study of Recessed and Non-recessed Swirl Coaxial Injectors

Abstract: The combustion characteristics of swirl-coaxial injectors with LOX/hydrogen were experimentally evaluated. Cold flow tests with water/nitrogen gas showed the known self-pulsating flow with swirl-coaxial injectors with recessed LOX post Combustion tests with single element combustors were conducted at chamber pressures of 2.6 MPa and 3.5 MPa, thrusts of 850 N and 500 N, and an oxidant to fuel ratio of 4.0 to 8.0. Combustion performance, chamber pressure distribution, and heat load on the chamber wall for each injector were measured and analyzed. The results indicated that the combustion performance was mainly limited by the vaporization efficiency in the shear-coaxial injector and by the mixing efficiency in the swirl-coaxial injectors. A significant increase of heat load on the chamber wall was observed with recessed swirl-coaxial injectors, and in some cases, the occurrence of unstable combustion was also observed.