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.

Integration of scientific data and formulae in an object-oriented knowledge-based system

Abstract: An object-oriented knowledge based system has been developed to store and manipulate scientific knowledge in the form of data and formulae encountered in conventional textbooks on science and engineering. The formulae are input in the same form as they are written in, in terms of the well known symbols used by engineers and scientists. The system interprets the symbols as representing scientific quantities and links them with the underlying data and methods in the knowledge base. By linking data about scientific quantities with one or more appropriate formulae, it is shown that the knowledge base can be used for simple problem solving. The development of the system on a Sun Sparcstation was facilitated by the use of an object-oriented environment, Objectworks C++.

In Flight Radome Error Compensation through Simulated Test Data

Abstract: This work deals with Algorithm for In Flight Radome Error Compensation with simulated data of radome test result for both In Plane Error and Cross Plane Error which are obtained as function of kinematic look angles. The se data are generally stored in On -Board Computer of either Interceptor or Seeker for compensation. Accurate information of kinematic look angles is required for proper interpolation of stored data. Measured gimbal angles lag kinematic gimbal angles throug h track loop time constant, which can be time varying depending on noise content and tracking accuracy of measured sight line rate. In this paper, measured gimbal angles are utilized for computation of radome errors from look up table for compensation. Ear lier results suggest that compensation within track loop yields better performance compared to compensation outside track loop. In this paper it is shown that, performance of homing loop for outside track loop compensation when computed radome errors are m odified by a suitable filter, is quite close to performance with radome error compensation inside track loop. This makes Interceptor system more reliable because in the event of any breakage of radome, spare one can fit in and corresponding test data can b e easily inserted in Interceptor OBC for accurate compensation rather than tampering sensitive software of Seeker OBC for inside track loop compensation. Suitable formulae are also derived for radome errors in 3 -D engagement scenario comprising both In -Pla ne and Cross Plane Errors. Additional results are also derived showing how In Plane and Cross Plane Error characteristics of radome covering its full engagement geometry obtained by experiment can be utilized for on -board compensation. In all these results , realistic simulated seeker noise profile, gimbal angle noise are utilized to claim for practical feasibility of this work.

Ritz finite element approach to nonlinear vibrations of a Timoshenko beam

Abstract: The Ritz finite element approach is used to study the nonlinear free vibrations of a beam considering shear deformation and rotary inertia effects. The governing nonlinear equations are derived using Lagrange equations at the point of reversal of motion. The nonlinear strain-displacement relations include the curvature terms based on three-dimensional incremental deformations, as used in Trefftz theory. A simple and efficient beam element, with three independent degrees-of-freedom at each node, and with linear polynomial distributions within the element, is made use of. The reduced integration technique is adopted on the shear related matrix to eliminate spurious constraints occurring when exact integration is used for the same in the case of slender beams. The governing equations are solved using a direct iteration scheme. Numerical results are presented in the form of tables for hinged-hinged immovable beam. When the present results are compared with the available ones wherever possible, good agreement is in general, found.

Validation of three-dimensional simulation of Flow through Hypersonic air-breathing engine

Abstract: The flow path of a conceptual hypersonic air-breathing scramjet engine integrated with the vehicle (without combustion) has been simulated numerically using ANSYS CFX software with the SST turbulence model. The computations were performed for the free stream Mach number of 6 and angle-of-attack of 5°. A strong separation bubble was observed on the bodyside wall in the internal compression region where the reflected cowl shock impinges on body which in turn increases the static pressure substantially. The external-internal flow field of the hypersonic mixed compression intake, shock-boundary layer interactions, and the shock-shock interactions present in the internal compression region have qualitatively been obtained and analysed. The variation of centreline pressure along the bodyside wall close to the symmetry plane obtained from numerical simulation centreline has been compared with the experimentally measured data. It has been observed that the computed wall pressure matches fairly well with the measured values in the external ramp compression region, internal compression region and in the combustion chamber. The flow patterns and the pressure variations near the middle wall and the fuel injecting strut locations have also been analysed. Defence Science Journal, Vol. 65, No. 4, July 2015, pp. 272-278, DOI: http://dx.doi.org/10.14429/dsj.65.6979