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.

Numerical Investigation on Effect of Inlet Dump Angle on Ramjet Combustor Performance

Abstract: Ramjet combustion is a highly complex phenomenon involving simultaneous momentum, heat and mass transport processes. It involves a variety of complexities such as high temperature variation, intricate flame chemistry and liquid – gas phase coupling, which are formidably challenging for a complete theoretical analysis. The governing equations with appropriate boundary conditions for flow in a ramjet dump combustor with two side inlets 90 apart are solved using the flow simulation software FLUENT. Standard k H equations based on generalized Boussinesq eddy viscosity concept are employed for the prediction of turbulent flow features. The gas phase heat and mass transfer have been modelled by Eulerian approach, while Lagrangian formulation is used for tracking the fuel particles. In liquid phase modelling, the momentum, energy and species balances are carried out by treating the droplet as a lumped system. Probability Density Function (PDF) approach is employed to describe the turbulent fluctuations in the mixture fraction. Predictions of temperature inside a ramjet combustor were compared with the limited experimental data available and these were found to match reasonably well. A detailed study has been carried out on the baseline combustor geometry under consideration for air inlet dump angles of 30,45 and 60 and the results are discussed in this paper.

Numerical Simulation of Non-Equilibrium Plasma Discharge for High Speed Flow Control

Abstract: Numerical simulation of hypersonic flow control using plasma discharge technique is carried out using an in-house developed code CERANS-TCNEQ. The study is aimed at demonstrating a proof of concept futuristic aerodynamic flow control device. The Kashiwa Hypersonic and High Temperature wind tunnel study of plasma discharge over a flat plate had been considered for numerical investigation. The 7-species, 18-reaction thermo-chemical non-equilibrium, two-temperature air-chemistry model due Park is used to model the weakly ionized flow. Plasma discharge is modeled as Joule heating source terms in both the translation-rotational and vibrational energy equations. Comparison of results for plasma discharge at Mach 7 over a flat plate with the reference data reveals that the present study is able to mimic the exact physics of complex flow such as formation of oblique shock wave ahead of the plasma discharge region with a resultant rise in surface pressure and vibrational temperature up to 7000 K demonstrating the use of non-equilibrium plasma discharge for flow control at hypersonic speeds.

Development and Validation of a Grid-Free Viscous Solver

Abstract: N UMERICAL simulation of the flowfield of a practical configuration poses severe difficulty due to complex gridgeneration procedures. A Cartesian grid with near-wall extruded grids [1], chimera or overset grids [2], grid-free methods [3], and a combination of the aforementioned methods [4] is used to solve flow past complex configurations. The grid-free methods operate on a distribution of points in the domain and require a set of supporting nodes around each point to evaluate the spatial derivatives of the governing fluid equations. The point distribution can be obtained from structured, unstructured, Cartesian, hybrid, or overlapped meshes, or a randomdistribution of points. In recent years, quite a few grid-free methods were proposed in the field of compressible fluid flow. Among them, the least-squares kinetic upwind method developed by Deshpande et al. [5] has received much attention of researchers and been applied to number of complex flight vehicle configurations. Recently, the method was successfully applied to a store separation dynamics problem using a chimera cloud of points [6]. Batina [7] developed a gridlessmethod that used the least-squares method with the unbiased support of points for the discretization of spatial derivatives. Artificial viscosity is used to stabilize the solutions and applied to inviscid and laminar flows. Lohner et al. [8] developed a finite point method, in which an upwind scheme was used to stabilize the solutions, and applied it to inviscid compressible flows. In the finite point method, the direction of upwinding is based on coefficients of the least-squares discretization, which is purely geometric. In recent years, the grid-freemethod has been successfully applied to simulate turbulent flow past complex flight vehicle configurations [9,10]. These methods used either overset grids or extruded layers of points near the wall, along with Cartesian grids in the offbody region, to get the distribution of points; and neighbors are obtained using search algorithms guided by grid information, which is therefore known as the semimeshless method. Lohner et al. [8] developed the advancing point generationmethod to generate a cloud of points, and the neighbors of those points were obtained using a local Delaunay triangulation. The applications, so far, are limited to subsonic and transonic flows. In the present work, a grid-free Euler and Navier–Stokes (GEANS) solver has been developed using a gridless method [7] with upwind fluxes for flow stabilization, and it has been validated for hypersonic flows at higher angles of attack. One of the main drawbacks of the grid-free methods is the lack of conservation. Katz and Jameson [11] enforced conservation by modifying weights in the least-squares discretization. However, such modified weights may become negative for certain distribution of points that leads to nonpositive solutions. Chiu et al. [12] proposed a method of generating meshless coefficients with conservation constraints at the discrete level; however, thismethodwas complex to implement for three-dimensional (3-D) problems with an anisotropic distribution of points. In the present work, high-speed flows are simulated without enforcing the conservation property. A detail experimental results [13] for an all-body hypersonic aircraft is available for comparison of aerodynamic forces and moments in addition to local flowfields. The flowfield around the geometry is very complex, which involves strong compressions in the windward side and strong expansions in the leeward side, with flow separation and vortices at a hypersonic Mach number. Furthermore, highaspect-ratio grid cells are required to resolve the very fine details of the flowfield. The simulation of such flowfields requires a robust flow solver that can handle both strong oblique shock wave and high expansion regions, as well as be accurate enough to resolve the boundary layer. Therefore, the aforementioned configuration is considered for validating the grid-free Euler and Navier–Stokes solver [14] at hypersonic speed and the results are compared with the experimental values. The geometry considered for validations in the present work is simpler and amenable for generation of simple structured grids. Therefore, structured grids are generated around the body to get a distribution of points and supporting nodes are obtained using the structured grid adjacency relation.

Design and development of Propulsion System for Antitank Guided Missile

Abstract: A Propulsion system is designed and developed for the third generation antitank guided missile (ATGM). It consists of a separate booster and sustainer. Booster is ahead of sustainer, having four nozzles canted to the missile axis. Sustainer discharges through a supersonic blast tube. Low smoke, high energy nitramine propellant for this propulsion system developed by the High Energy Materials Research Laboratory (HEMRL), Pune, has been successfully flight-tested. The booster grain is tube-in-tube configuration with end inhibition and the sustainer grain is of end burning configuration. High strength aluminium alloy, HE-15, is used for rocket motor components. Glass-phenolic composite ablative material is used for thermal protection of motors and high density graphite is used for nozzle throats. The design considerations and approach, including grain configuration, nozzle, and ignitersare briefly discussed. The propulsion system has been extensively tested in static tests and in flights, establishing the satisfactory performance of the system.

Numerical Analysis of Integrated Liquid Ramjet Engine

Abstract: The numerical simulation of an integrated, liquid-fuelled ramjet engine comprising supersonicair intake, subsonic combustor and a convergent-divergent nozzle has been carried out and theresults are discussed in this paper. These results include cold flow studies, heat addition in thecombustor and full engine analysis with coupled simulation of supersonic air-intake andcombustion chamber along with the nozzle. Overall ramjet operation depends on the performanceof the air intake and the combustion chamber. The coupling phenomena are very dominant andperformance of air intake is affected vastly by the combustor operation and vice versa. In thispaper, a numerical analysis of integrated liquid ramjet engine considering coupling phenomenabetween various sub-systems viz., air intake, combustor and nozzle has been reported.