Defence Research and Development Laboratory

About: Defence Research and Development Laboratory is a facility organization based out in Hyderabad, India. It is known for research contribution in the topics: Mach number & Turbulence. The organization has 404 authors who have published 420 publications receiving 4183 citations. The organization is also known as: DRDL.

Numerical Flow Visualization of a Single Expansion Ramp Nozzle with Hypersonic External Flow

Abstract: Numerical simulation of scramjet asymmetric nozzle flow is carried out to visualize and investigate the effects of interaction between engine exhaust and hypersonic external flow. The Single Expansion Ramp Nozzle (SERN) configuration studied here consists of flat ramp and a cowl with different combinations of ramp angle and cowl geometry. Using PARAS 3D, simulations are performed for a free stream Mach number of 6.5 that constitutes the external flow around the vehicle. Appropriate specific heats ratio has been simulated for the jet and free stream flow. External shock wave due to jet plume interaction with free stream flow, the internal barrel shock wave and the shear layer emanating from the cowl trailing edge and sidewalls are well captured. Wall static pressure distribution on the nozzle ramp for different nozzle expansion angles has been computed for both with and without side fence. Axial thrust and normal force have been evaluated by integrating the wall static pressure. Effect of cowl length variation and side fence on the SERN performance has also been studied and found to be quite significant. Based on this study, an optimum ramp angle at which the SERN generates maximum axial thrust is obtained. SERN angle of 20o was found to be optimum when the flight axis coincides with nozzle axis.

Surface characteristics of titanium with rotary EDM

Abstract: Experimental investigations have been carried out on electro-discharge machining of titanium in respect of surface finish, out-of-roundness and overcut using rotating copper-tungsten tool electrode. An attempt has also been made to compare the results with stationary electrode.

Mathematical Modelling of Rotating Single-walled Carbon Nanotubes used in Nanoscale Rotational Actuators

Abstract: In this study, a rotating single-walled carbon nanotube (SWCNT) is modelled as an Euler-Bernoulli beam using the non-local/non-classical continuum mechanics. These rotating SWCNTs are used in nanoscale rotational actuators. The mathematical model has been used to study the wave behaviour in rotating SWCNTs. The governingpartial differential equation for a uniform rotating beam is derived incorporating the non-local scale effects. The spatial variation in centrifugal force has been modelled in an average sense. Even though this averaging seems to be a crude approximation, one can use this as a powerful model in analysing the wave dispersion characteristics ofthe rotating CNTs. Spectrum and dispersion curves as a function of rotating speed and non-local scaling parameter were obtained. It has been shown that the dispersive flexural wave tends to behave non-dispersively at very high rotation speeds. The numerical results have been simulated for a rotating SWCNT as a waveguide. Defence Science Journal, 2011, 61(4), pp.317-324 , DOI:http://dx.doi.org/10.14429/dsj.61.1091