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.

Assessment of droplet breakup models in high-speed cross-flow

Abstract: The breakup process in quiescent atmosphere and high-speed cross-flow is numerically simulated. Three-dimensional RANS equations with the K-ε turbulence model are solved using commercial CFD software. Different droplet breakup models, namely, TAB, ETAB, Ritz-Diwakar, and KH-RT models are studied to assess their predictive capability in characterizing spray in high-speed cross-flow. The validation test cases include liquid injection into quiescent atmosphere, and subsonic and supersonic cross-flow. Computed droplet velocity, droplet size, and spray penetration are compared with the experimental/numerical data available in the literature. For diesel injection in quiescent atmosphere, computed spray penetration matches reasonably well with the experimental data. For subsonic cross-flow, although the penetration height is underpredicted, SMD distribution and particle velocity match reasonably well with the experimental data. The ETAB model captures the SMD values at different locations and velocities better with experimental data in comparison to the TAB model. For the supersonic cross-flow case, penetration height and SMD have a good match with the experimental data. The Stokes drag model performs better than the high-Mach and dynamic drag models. Droplet drag law for supersonic flow needs to be revised to have better predictive capability of spray characteristics in high-speed flow.

A Novel CFD Method to Estimate Heat Transfer Coefficient for High Speed Flows

Abstract: Accurate prediction of surface temperature of high speed aerospace vehicle is very necessary for the selection of material and determination of wall thickness. For aerothermal characterisation of any high speed vehicle in its full trajectory, it requires number of detailed computational fluid dynamics (CFD) calculations with different isothermal calculations. From the detailed CFD calculations for different flow conditions and geometries, it is observed that heat transfer coefficients scale with the difference of adiabatic wall temperature and skin temperature. A simple ‘isothermal method’, is proposed to calculate heat flux data with only two CFD simulations one on adiabatic condition and other on isothermal condition. The proposed methodology is validated for number of high speed test cases involving external aerodynamic heating as well as high speed combusting flow. The computed heat fluxes and surface temperatures matches well with experimental and flight measured values.

Flexural stress analysis of uniform slender functionally graded material beams using non-linear finite element method

Abstract: Functionally graded material (FGM) typically consists of two constituent materials combined together with a particular distribution. A non-linear flexural stress analysis of through-thickness functionally graded uniform slender beam, subjected to a uniformly distributed load, is studied using the versatile finite element method based on Euler–Bernoulli beam hypothesis. The von-Karman strain–displacement relations are used to account for geometric non-linearity. Simply supported and clamped FGM beams with axially immovable ends are considered. Governing non-linear equations are obtained using the principle of virtual work. Numerical results are provided to show the effect of boundary conditions and volume fraction exponent on the non-linear structural behaviour, in terms of the strains and stresses, of the FGM beams, for the first time. A shift in the neutral axis, from the mid-thickness of the beam, is observed due to the large transverse deflections, for the homogenous as well as the FGM beams. The throu...

Numerical Exploration of Solid Rocket Motor Blast Tube Flow Field

Abstract: The blast tube flowfield of a solid rocket motor is explored numerically by solving 3-D RANS equations with SST Turbulence model using a commercial computational fluid dynamics (CFD) software CFX-10. Parametric studies are carried out to find out the effect of the blast tube diameter on the total pressure loss in the rocket motor. It is observed that the total pressure loss in the rocket motor is less than 4 per cent and the blast tube is contributing less than 1 per cent. It is also found out that higher the blast tube diameter, the lesser the drop in the total pressure. Blast tube geometry is not found to contribute significantly in the overall thrust and specific impulse in the rocket motor. Defence Science Journal, 2013, 63(6), pp.616 -621 , DOI:http://dx.doi.org/10.14429/dsj.63.5763

Corrosion properties of cryorolled aa2219 friction stir welded joints using different tool pin profiles

Abstract: The purpose of this paper is to present the corrosion behavior of the Cryorolled (CR) material and its Friction Stir Welded joints. Due to the thermal cycles of Friction Stir Welding (FSW) process, the corrosion behavior of the material gets affected. Here, the cryorolling process was carried out on AA2219 alloy and CR material was joined by FSW process using four different pin tool profiles such as cylindrical, threaded cylindrical, square and hexagonal pin. The FSW joints were analyzed by corrosion resistance with the help of potentiodynamic polarization test with 3.5% NaCl solution. From the analysis, it is found that CR AA2219 material exhibits good corrosion resistance compared to the base AA2219 material, and also a hexagonal pin profile FSW joint exhibits high corrosion resistance. Among the weld joints created by four different tools, the lowest corrosion resistance was found in the cylindrical pin tool FSW welds. Further, the corroded samples were investigated through metallurgical investigations...