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.

Quasi-One-Dimensional Modeling of Internal Ballistics and Axial Acoustics in Solid Rocket Motors

Abstract: An unsteady quasi-one-dimensional flow solver for simulating internal ballistics and axial acoustic fluctuations in solid rocket motors is presented in this paper. Higher-order numerical solutions of quasi-one-dimensional governing equations are prone to numerical oscillations due to the nonconservative form of the governing equations and the nonsmooth axial variations of the cross-sectional area. Adding artificial dissipation to a central scheme is found to be inadequate for suppression of such oscillations, and so a simple low dissipation shock-capturing scheme (named SLAU2) is used instead. The inherent numerical dissipation of this scheme is helpful in the proper capturing of steep-fronted acoustic waves (that develop at the onset of triggered instabilities) without undesirable numerical damping of the acoustic waves. Using the new solver, a procedure for computing characteristic frequencies, corresponding mode shapes, and damping rates is proposed and validated for a motor with a cylindrical grain ge...

Design of non-contact transduction based pressure sensor using Tunneling magnetoresistive (TMR) principle

Abstract: A pressure sensor with non-contact transduction which measures deflection of diaphragm due to applied pressure, using tunneling magnetoresistive (TMR) principle is aimed to meet the requirements of pressure measurement in harsh environments. In commonly used strain gauge type of pressure sensor, strain depends not only on pressure but also on media temperature which induces more error or burnout strain gauges at high temperature. A novel non-contact measurement principle to detect diaphragm deflection is proposed that allows to overcome these limitations. For this purpose, Samarium Cobalt magnet and TMR sensor are used. As transduction is non-contact, this method is useful to measure pressure of hot gas produced by combustion of short duration. This paper presents the design of pressure sensor using TMR principle and its evaluation supported by the simulated test results. Further scope of work towards improvement of accuracy and confidence on pressure measurement has been concluded to aid sensor design in future.

IR Image Simulation

Abstract: Image tracking algorithms, particularly, pixel level based frame to frame correlation techniques need realistic dynamic scene sequences in order to evaluate their performance and to know whether the algorithms are converging or not. The cost effective way of obtaining these images is only by means of understanding the various constituents of the system, their relationship through a mathematical model and then simulating the required scenario. This paper describes such a scheme - IR Image Simulation (IRIS) when both the target and the sensor are in motion. Details of mathematical model of a tank like target are mentioned in this paper. Development of software packages for simulating background, receiver optics, atmosphere etc., are realized based on the mathematical models which are taken from the open literature. A methodology for real time usage of this system is also briefly mentioned in this paper. Examples of computer simulated images are also presented.

Aerodynamic characteristics of generic flight vehicle configuration from shock tunnel tests

Abstract: A generic flight vehicle configuration has been designed as a possible candidate for hypersonic flight. Aerodynamic force coefficients over the test model configuration for different angles of attack are measured using a three-component accelerometer force balance system. Experiments are conducted in HST2 shock tunnel facility of IISc at an enthalpy of 2 MJ/kg and nominal Mach number of 6. This data will be useful for validating numerical results obtained by CFD techniques.

Estimation of the Grain Size Number and Microstructure Analysis of AA6061 Alloy Flow Formed Tubes

Abstract: Flow forming process is a chipless metal forming process used for the production of high accuracy axi-symmetrical cylindrical components. During this process there is an increase in tube length and decrease in thickness without any change in internal diameter. Generally forming is performed with a single roller or three rollers over a rotating mandrel and the present work is with three roller setup. The work material is plastically deformed in the radial direction by compression due the rollers and made to flow in an axial direction and the thickness reduction is achieved with single pass. The AA6061 aluminum alloy, usually used in defense components is considered for flow forming. The mechanical properties of this alloy are dependent on the rate at which the alloy is heated and quenched. Solution treatment has been carried out at 400 °C for 2 h followed by quenching in water. Microstructure of the finished product has been studied by using SEM and grain size is estimated for different reduction ratios and stagger distance using the intercept method.