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.

Evaluation of structural integrity of tactical missile ceramic radomes under combined thermal and structural loads

Abstract: Radome is a thermo-structural member used in tactical missiles and houses the avionic systems like seeker. It is subjected to severe thermal as well as structural loads during the flight. The material of the radome is chosen such that it is transparent electromagnetic radiation. The ceramic radome is attached to the metallic bulkhead with high temperature glue. In the present manuscript, the experimental evaluation methodology implemented for evaluation of the structural integrity of the ceramic radome under combined thermal and structural loads is presented. Initially axial load, to simulate the resultant drag force and a distributed lateral load, to simulate the bending moment, are applied via a pre-casted contoured Teflon mock sections, up to proof load and then time varying temperature is applied. The time-varying temperature profile is applied via a closed loop control based on PID and the heating environment is created using short wave infra-red radiation. Exhaustive instrumentation is used in the experiments. Detailed results are also presented in the manuscript up to the structural failure.

Effect of Geometric Parameters on the Aerodynamic Characteristics of Grid-Fin Cells at Supersonic Speeds

Abstract: *† Grid fins are an efficient means of aerodynamic control surfaces, where hinge moment requirement is low and marginal increase in drag is acceptable. Many theoretical, computational and experimental studies have been carried out on specific configurations. In the present study, the flow field inside individual grid fin cells has been studied. Effect of some geometrical design parameters like depth-to-height ratio, thickness-to-height ratio, web leading edge angle and cell width-to-height ratio has been investigated for cubical cells. The results indicate that above certain depth-to-height ratio, called critical depth-to-height ratio, the local normal force becomes negative. The critical depth-to-height ratio a) increase with increase in Mach number b) reduces with increase in angle of attack and c) reduces with increase in thickness. Different width-toheight ratio has been studied keeping the cross sectional area same. Increase in widthto-height ratio increases the normal force for a given depth due to higher area facing the flow, but the maximum normal force remains same due to reduction in critical depth.

Effect of Mach Number on Shock Oscillations in Supersonic Diffusers

Abstract: Unsteady characteristics of shock wave oscillations are one of the most prevalent phenomena occurring in a supersonic diffuser. In such oscillations, significant boundary layer separation leads to a highly unsteady flow field resulting in inlet instability, aircraft buffeting, and aero-structure fatigue. From an engineering point of view, this phenomenon can have a significant impact on performance of supersonic diffusers operating near critical mass flow because of the complex interaction between the boundary layer and many shock waves. This includes a shock-wave/turbulent boundary-layer interaction (SBLI) followed by a subsonic region with an adverse pressure gradient and rapidly thickening boundary layer.

Nonlocal thermodynamic response of a rod

Abstract: Thermally induced behavior of a rod under the influence of a moving heat source is studied in the present work. The thermal behavior is modeled using the non-Fourier heat conduction model and the elastodynamic behavior of the rod is modeled using the nonlocal continuum mechanics. Laplace transformation and Riemann-sum approximation methods are used in the mathematical formulations. Based on the temperature history, the thermally induced nonlocal deformation and nonlocal stress behavior of the rod are studied. The influences of nonlocal scale parameter and speed of the heat source are studied in detail. The results presented in this work are helpful in the design of nanoscale welding, grinding, metal cutting devices, etc., that make use of the thermodynamic behavior within the nanoscale rod.