A. G. Marathe

Numerical studies of infrared signature levels of complete aircraft

This paper begins with an outline of the procedure for predicting the infrared signature emissions from the airframe, engine casing, and the plume, and their attenuation by the intervening atmosphere. These emissions are contrasted against the background, to obtain the infrared signature levels. The infrared detector’s — noise equivalent flux density, is proposed as an operational constraint on the flight envelope. The shift of this newly imposed constraint on the flight envelope for several engine-operating conditions, and for turbojet and turbofan engines is studied. The signature levels from the casing and plume, of a turbofan and equivalent turbojet engine, are compared at different operating points on the flight envelope. Result in the form of a polar plot of infrared signature level variation with aspect is also examined for low flying missions. The results are analysed to direct stealth design and operation.

Some Studies on Hydrogen-Oxygen Diffusion Flame

The opposed-jet diffusion flame has been considered with four step reaction kinetics for hydrogenoxygen system. The studies have revealed that the flame broadening reduces and maximum temperature increases as pressure increases. The relative importance of different reaction steps have been brought out in different regions (unstable, near extinction and equilibrium). The present studies have also led to the deduction of the oveall reaction rate constants of an equivalent single step reaction using matching of a certain overall set of parameters for four step reaction scheme and equivalent single step reaction.

Computations of laminar and turbulent mixed convection in a driven cavity using pseudo-compressibility approach

Abstract A driven cavity, for two different thermal boundary conditions, has been chosen as a test case to establish the suitability of pseudo-compressibility algorithm for mixed convection flow problems for both laminar and turbulent flow situations. Here shear stress transport eddy viscosity model has been modified to include the buoyancy effects. The flow is computed inside the cavity under the influence of varying buoyancy and inertia forces. The computed results demonstrate the ability of the pseudo-compressibility approach and shear stress transport model to solve complex heat transfer problems.

Analysis of performance of a hot gas injection thrust vector control system

The complex three-dimensional flowfield produced by secondary injection of hot gases in a rocket nozzle for thrust vector control is analyzed by solving unsteady three-dimensional Euler equations with appropriate boundary conditions. Various system performance parameters like secondary jet amplification factor and axial thrust augmentation are deduced by integrating the nozzle wall pressure distributions obtained as part of the flowfield solution and compared with measurements taken in actual static tests. The agreement is good within the practical range of secondary injectant flow rates for thrust vector control applications.

FINITE ELEMENT STUDY ON THE ROLE OF CONVECTION IN LASER SURFACE MELTING

The surface-tension-driven convection in laser melting has been simulated by the Galerkin finite element method. The governing laminar, axisymmetric convection equations are solved in a sequential manner by an explicit projection method. The numerical results show a strong dependence of the flow pattern on the value of the temperature coefficient of surface tension

3D-Duct Design Using Variable Fidelity Method

(\sigma_T)

Finite element solution of surface-tension driven flows in laser surface-melting

. Results are presented for a range of

Role of surface tension driven convection in pulsed laser melting and solidification

\sigma_T

Effect of Geometric Parameters on the Performance of Single Expansion Ramp Nozzle

values typical in steel,

Starting in Hypersonic Intakes

-10^{-4}lσ_Tl+10^{-4} N/mK