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.

Computational Study of Transverse Slot Injection in Supersonic Flow

Abstract: The knowledge of transverse sonic injection flow field is very important for the design of scramjet combustor. Three dimensional Reynolds-Averaged Navier Stokes equations alongwith turbulence models are solved to find the effect of transverse sonic slot injection into a supersonic flow. Grid sensitivity of the results is studied for various structured grids. Simulations with different turbulence models (i.e., k-e, k-ω, SST-kω, and RNG-ke) reveals that RNG-ke turbulence model better predicts the flow features. Computational fluid dynamics predicted wall pressure distribution for various injection pressures matches well with experimental data. The extent of upstream separated region increases with the increase of the injection pressure. The increase of slot width makes the interaction between transverse jet and free stream more intense and causes more spreading and penetration of injectant in the downstream region.

Influence of Aircraft Flow Field on the Longitudinal Stability of a Missile

Abstract: An air-to-air missile launched from a fighter aircraft needs to be stable at launch to enable safe separation from the aircraft, and less stable in the terminal phase of its flight to become highly maneuverable to intercept the targets. A study has been carried out to estimate the effect of the aircraft flow field on the longitudinal stability of the missile using an in-house developed 3-D grid-free Euler solver. Initially, the missiles are placed in the captive location in the launcher of the aircraft. One of the missiles is then moved to various pre-determined locations ahead of the wing of the aircraft, keeping the other missile at the captive location. The centre of pressure and stability margin of the missile is determined at these locations. It is observed that the presence of aircraft has a substantial effect on the longitudinal stability of the missile. The centre of pressure of the missile is seen to move aft as it leaves the launcher. As the missile moves, the centre of pressure reaches a maximum aft position and then moves forward till it reaches a position where the missile is free from the influence of the aircraft. It is observed that as the missile moves away from the region of strong influence of the aircraft, its aerodynamic characteristics approach asymptotically to that of the isolated missile.Defence Science Journal, 2013, 63(3), pp.242-248, DOI:http://dx.doi.org/10.14429/dsj.63.2099

Non-destructive evaluation of delaminations and voids in axis-symmetric cfrp shells: Part A scope and limitation of tangential x-ray radiography

Abstract: Publisher Summary This chapter presents an axis-symmetric cfrp shell of specific dimensions. Axis-symmetric composite structures are widely used in aerospace applications. Among the common processing defects, delaminations and voids happen to be most predominant. It is well known that an ideal two dimensional defect of zero thickness like delamination cannot be detected by X-ray radiography. Delamination is defined as a defect whose thickness is small compared to its other dimensions. As the thickness tends to increase and becomes comparable with its planer dimensions, the defect turns into a void. However, even detectability and relative comparison of defects by application of this technique need to be accepted with some amount of caution. The crux of the problem reveals the fact that every single X-ray beam propagating through the component happens to have a different path length, depending on the component geometry and also on the source component-film configuration. Systematic investigations on X-ray radiography of carbon-fibre-reinforced composites are attempted in recent years by a few workers. The workers advocated half-value-layer approach for establishing appropriate energy levels for composite radiography. Though selection of 5EHVL appears to be the most common, 2EHVL, 4EHVL, and 6EHVL exposures were tried out, given the additional complexity of the darkening background and varying component-film distance in tangential radiography.