Indian Institute of Technology Hyderabad (IITH) is a premier institute of science and technology established in 2008. IITH has been consistently ranked in the&nbsp;<a href="https://iith.ac.in/reports/" rel="noopener noreferrer">top 10 institutes</a>&nbsp;in India for Engineering&nbsp;<a href="https://www.nirfindia.org/2021/EngineeringRanking.html" rel="noopener noreferrer" target="_blank">according to NIRF</a>&nbsp;making it one of the most coveted schools for science and technology in the country.

IITH offers&nbsp;<a href="https://iith.ac.in/academics/under-graduate/">undergraduate programs</a>&nbsp;in all the classical engineering disciplines, applied sciences, design, as well as several modern interdisciplinary areas. Students are given a flexibility to explore a broad set of areas, and potentially pursue a minor or double major in a discipline that is not their own. Students who wish to seek a deeper understanding of their own discipline are strongly encouraged to get involved in cutting-edge research with the help of a faculty to mentor them, and earn an Honors in their own field.

The very foundation of IIT Hyderabad is based on&nbsp;<a href="https://iith.ac.in/research/">research and innovation</a>. The vibrant research culture is evident from the number of patents and publications that IITH produces consistently every year. IITH offers&nbsp;<a href="https://iith.ac.in/academics/programmes-offered/">graduate programs</a>&nbsp;at both a masters, and a doctoral level, in several diverse areas. There are separate programs for technology, design, science, and liberal arts. The&nbsp;<a href="https://iith.ac.in/academics/post-graduate/">MTech program</a>&nbsp;is offered in various modes and durations to cater to the ever-growing need of postgraduate level professionals in the country.

IITH encourages and supports&nbsp;<a href="https://iic-iith.netlify.app/index.html" rel="noopener noreferrer" target="_blank">innovation and entrepreneurship</a>&nbsp;at every stage. The minor program in entrepreneurship is open to all students of IITH, and many of the courses are offered by industrialists who are entrepreneurs themselves. There are various&nbsp;<a href="https://iith.ac.in/research/centres-incubators/">innovation centers and incubators</a>&nbsp;that promote entrepreneurship and help mentor young innovators. IITH has been very successful in building tie-ups with leading academic institutions around the globe.

IITH enjoys a very special relationship with Japanese universities and industries that goes beyond academic and research collaborations. In fact, some of the iconic buildings in IITH campus will carry the signature of Japanese architecture.

IITH creates a unique holistic ecosystem for education that offers interactive learning, a very flexible academic structure, cutting-edge research, strong industry collaboration, and entrepreneurship. This is an environment which enables students and faculty to translate their dreams into realities.

IIT Hyderabad

The hydrodynamic instabilities in the shear layer of fuel jet leads to transition of gas jet diffusion flames even when the injector flow is laminar. The current study investigates the transition process and identifies the dominant effect of buoyancy on the transitional flame structure. A highspeed digital imaging system was integrated with the rainbow Schlieren apparatus to visualize hydrogen jet diffusion flames in quiescent air at image acquisition rate of 2000 frames per second and exposure time of 23 μs. The flame visualization revealed that the well known buoyancy driven instability is accompanied with secondary roll up vortices on the flame surface, with similarity in structure to the Kelvin Helmholtz instability. The frequency spectra analysis revealed that the flicker, typical of laminar flames, also occurs in transitional flames. The fuel jet also oscillates at the flame flicker frequency caused by the bulging and squeezing effect of buoyancy driven outer vortical structures. The fuel jet oscillations lead to intermittency in the breakpoint length. The period oscillations are sustained even in the turbulent fuel jet and flame regions downstream of the breakpoint.

Department of Mechanical and Aerospace Engineering

World University root node

5th US Combustion Meeting 2007

Role of buoyancy on instabilities in transitional gas jet diffusion flames

Transitional jet diffusion flames provide the link between dynamics of laminar and turbulent flames. In this study, instabilities and their interaction with the flow structure are explored in a transitional jet diffusion flame, with focus on isolating buoyancy effects. Experiments are conducted in hydrogen flames with fuel jet Reynolds number of up to 2,200 and average jet velocity of up to 54 m/s. Since the fuel jet is laminar at the injector exit, the transition from laminar to turbulent flame occurs by the hydrodynamic instabilities in the shear layer of fuel jet. The instabilities and the flow structures are visualized and quantified by the rainbow schlieren deflectometry technique coupled with a high-speed imaging system. The schlieren images acquired at 2,000 frames per second allowed exposure time of 23 μs with spatial resolution of 0.4 mm. Results identify a hitherto unknown secondary instability in the flame surface, provide explanation for the observed intermittency in the breakpoint length, show coherent vortical structures downstream of the flame breakpoint, and illustrate gradual breakdown of coherent structures into small-scale random structures in the far field turbulent region. © 2007 Springer Science+Business Media B.V.

Flow, Turbulence and Combustion

Role of buoyancy on instabilities and structure of transitional gas jet diffusion flames

The solid angle (Ω) subtended by the hot power-plant surfaces of a typical fighter aircraft, on the detector of an infrared (IR) guided missile, is analytically obtained. The use of the parallel rays projection method simplifies the incorporation of the effect of the optical blocking by engine surfaces, on Ω-subtended. This methodology enables the evaluation of the relative contribution of the IR signature from well-resolved distributed sources, and is important for imaging infrared detection studies. The complex 3D surface of a rear fuselage is projected onto an equivalent planar area normal to the viewing aspect, which would give the same fl-subtended. © 2007 Optical Society of America.

Applied Optics

Analytical estimation of solid angle subtended by complex well-resolved surfaces for infrared detection studies

The present study deals with the development and application of micron resolution rainbow schlieren deflectometry (μ-schlieren) apparatus to obtain whole field scalar measurements in micro-fluidic systems. The μ-schlieren system utilizes a 150 W halogen light source, achromatic lenses, and a CCD camera together with a camera lens, 2x lens-extender and extension tubes. The schlieren images obtained from the μ-schlieren system are analyzed using in-house post processing software to provide quantitative scalar measurements with spatial resolution down to 8 μm. The technique is first applied to measure the concentration field of a non-reacting helium-air jet with tube diameter of 1100 μm. Next, temperature measurements in a hydrogen jet diffusion flame from 30 μm diameter tube are presented to demonstrate the capability of the system in measuring reacting flows. The data presented in this study are the highest spatially resolved schlieren measurements published to date.

Collection of Technical Papers - 45th AIAA Aerospace Sciences Meeting

Quantitative scalar measurements in micro jets and flames

In the past, the rainbow schlieren deflectometry technique has been employed to obtain scalar measurements in non-reacting and reacting laminar steady or unsteady flows. The technique has been limited to laminar flows because the path integrated beam deflection angle data must be de-convulated to obtain the local flow properties. In this study, a cross beam approach, whereby two orthogonal beams are employed is explored for statistical measurements in turbulent flows. The theoretical framework of the cross beam correlation technique requiring assumptions of homogeneous and isotropic turbulence is presented. The workability of the technique is verified using numerical simulations of an unsteady laminar helium-air jet.

Collection of Technical Papers - 44th AIAA Aerospace Sciences Meeting

Crossbeam rainbow schlieren deflectometry technique for scalar measurements in turbulent flows

This paper analyzes the main contributors of infrared (IR) signature in a typical aircraft on a low-altitude mission. Various computational models are used to predict IR radiation from the aircraft. The bands within IR spectrum in which aircraft are susceptible to a typical IR-guided surface-to-air and air-to-air missile, for typical cases of tactical relevance, are identified. Lock-on range for aircraft against a typical missile is also computed. The feasibility of a low-altitude mission against a ground-based IR-guided threat is analyzed. The technique of emissivity optimization of aircraft rear fuselage skin, for reducing its infrared signature, is introduced and compared with other IR signature suppression techniques. The effectiveness of this technique in enlarging the safe flight envelope of aircraft, with respect to threat from heat-seeking missiles, for both surface-to-air and air-to-air missiles, is demonstrated. It is found that earthshine reflected off the aircraft surface plays a crucial role in the effectiveness of this technique against a surface-to-air missile (SAM) in 8-12 μm band. Copyright © 2005 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Journal of Aircraft

Infrared signatures of low-flying aircraft and their rear fuselage skin's emissivity optimization

The temperature distribution of the exposed rear fuselage of fighter aircraft, which is necessary for estimating passively emitted infrared signature levels, is predicted. Hot combustion gases flowing through the gas-turbine engine and aerodynamic heating of the rear fuselage at high freestream Mach numbers are the two heat sources. Turbulent forced convection and radiation are the dominant heat-transfer modes, and hence two thermal models are developed: only turbulent forced convection, and combined turbulent forced convection and radiation. Variation in transport and thermophysical properties of fluids is also modeled. Gas-dynamic equations are used to obtain local flow parameters, considering the role of friction, heat transfer, and area variation. A radiation-shape-factor analysis for the complete layout is presented that accounts for mutual, partial, or complete visibility of emitter and receiver elements. A closed-form solution for shape factors between ring elements is derived for the annulus. The error in temperature estimation by neglecting parameters such as aerodynamic heating, variation in transport, and thermophysical and local-flow properties of fluid is found to be significant. We conclude with a discussion of the role of altitude and flight Mach number.