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: Turbulence & Mach number. The organization has 404 authors who have published 420 publications receiving 4183 citations. The organization is also known as: DRDL.

Missile materials—Current status and challenges

Abstract: Missile Development Programme has provided focal thrust to indigenous materials and components. Materials have been selected on the basis of their high strength to weight ratio, good corrosion resistance, high fracture toughness, easy fabricability and reliable quality. Alloys of magnesium, aluminium, titanium and maraging steel are extensively used for airframe and propulsion systems. Polymer materials and carbon-carbon composites are major nonmetallic materials. Development of high purity electronic materials like silicon, indium, phosphorus, Cu clad materials, photo resists and epoxies are very important for the programme. The paper covers the requirements and challenge areas of research, and calls for consortium approach involving academic institutions. R and D laboratories and industries to ensure self reliance.

Practical Design of Flight Control Systems: Some Problems and their Solutions

Abstract: The flight control system design, though quite satisfactory on paper, many times gives surprises during the actual flight. This is due to unanticipated behaviour of the vehicle structure or the aerodynamic characteristics, or the higher-order dynamics and nonlinearities, etc. The paper describes few such cases in which problems were faced and their solutions found, and which gave satisfactory performance subsequently

Numerical Simulation of a Hypersonic Air Intake

Abstract: Numerical simulations were carried out to study the unsteady flow in an intake of hypersonic air-breathing vehicle. Unsteady RANS simulations were performed to examine started flow of the intake when cowl surface is parallel to the ramp surface. Though started, the flow was unsteady due to flow separation bubbles inside intake. Intake with larger cowl opening at which intake unstarted was also simulated. Simulations indicated unstarted flow, with large pressure oscillations. The numerically simulation results match reasonably well with experimental data. Calculated unstarting Mach number was found to be 3.0-3.2 in comparison of wind tunnel data of 3.6 for the same cowl opening angle. Defence Science Journal, Vol. 65, No. 3, May 2015, pp.189-195, DOI: http://dx.doi.org/10.14429/dsj.65.8254

Effect of laser glazing on the thermo-mechanical properties of plasma-sprayed LaTi2Al9O19 thermal barrier coatings

Abstract: Conventional duplex (DL) and functionally graded (FG) LaTi2Al9O19 (LTA) coatings were deposited over C263 nickel alloy by air plasma spray (APS) and compared with subsequent laser glazing processes. The effect of laser glazing on adhesion strength and thermal barrier performance was investigated. The thermal barrier effect was measured using the temperature difference technique involving infrared (IR) rapid heater and the adhesion strength was measured using the scratch tester. The surface morphology and microstructure were analyzed by optical microscopy (OM), Scanning Electron Microscope (SEM) and 3D profilometer. Based on the experimental results, the laser glazing showed a remarkable temperature drop after IR rapid heating. The changes in porosity and grain refinement make more contributions to the temperature drop of the laser-glazed coatings than that of as-sprayed coatings. The temperature drop is about 110°C for laser-glazed LTA FG coating after 100 s of IR flash, while the drop in DL as-sp...

Effect of Liquid Injection on Acoustic Field Induced from Supersonic Flow Past Cavities

Abstract: This paper describes an experimental investigation of the effect of transverse liquid injection (distilled water) on the acoustic field generated by confined supersonic flow past a cavity. The effect of cavity depth in the absence/ presence of liquid injection on the acoustic field is studied. In the presence of liquid injection, the effects of injection pressure and injection location on the acoustic field are investigated. The dependence of suppression/amplification of the acoustic amplitudes (compared with the absence of injection) on the injection condition and cavity depths is ascertained. In general, liquid injection in the presence of cavity resulted in higher amplitudes. Even square cavities that did not exhibit oscillations in the absence of injection generated significant acoustic amplitudes in the presence of liquid injection at high injection pressures. Phase-locked schlieren imaging was performed to sequence the fluid-dynamic events. Schlieren images indicate the interaction of the shock wave generated by the flow past the liquid jet and the oblique shock generated at the cavity-leading edge. The schlieren images show that the amplitude increase observed for higher injection pressures for a range of cavity depths is accompanied by an unsteady normal shock ahead of the cavity-leading edge (which does not span the entire width of the test model, but is located locally in front of the liquid jet).