bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Investigation of Confinement Effect on Supersonic Turbulent Flow Past Backward Facing Step With And Without Transverse Injection
Authors: Manna P. , Chakraborty Debasis
Published: December 2023

Effect of confinement has been investigated numerically for supersonic turbulent flow past backward facing step in a nonreacting scramjet combustor. Flow structure downstream of the backward facing step has been studied by considering various configurations with different combustor heights as well as unconfined flow. Staged transverse sonic injectors with different combustor heights are also considered to find out the effect of confinement on the penetration, spreading and other flow features in the flow field. Three dimensional Navier Stokes equations along with k-ε turbulence model are solved using a commercial CFD software. The simulation captures all essential features of the flow. Good comparisons of various flow profiles have been obtained between experimental and computed values. Although confinement creates complicated shock reflections in the combustor, the length of the recirculation bubble behind the backward facing step remains almost constant. For the injection case, the recirculation region is extended upto the bow shock arising upstream of the injector and two recirculation bubble is seen between the backward facing step and the injector.
Numerical Study of Benchmark Experiments of Supersonic Compressor Cascades
Authors: Sriram A.T. , Mathew Joseph
Published: December 2023

Benchmark cases of turbulent supersonic flow through compressor cascades were computed using a modern upwind scheme (Roe with MUSCL pre-processing), with the k-ω turbulence model, and the classical MacCormack method. The test cases derive from experiments through ARL SL 19 blade cascades at Detroit Diesel Allison (DDA) at the design Mach number, and at an off-design condition from ONERA. A verification of the codes was obtained by computing an inviscid flow through a wedge cascade at similar conditions. Predictions are in very good agreement for the DDA test case for the blade surface pressure distributions. Cleaner solutions were obtained using the Roe scheme. The MacCormack solution exhibits oscillations corresponding to oscillations of the shock-induced separating boundary layer on the pressure surface near the trailing edge. Wake flow Mach number distributions were very well predicted, but not flow angle distributions. Predictions are less accurate for the ONERA test case which was at a slightly higher Mach number and which moves shock locations sufficiently to cause a more sensitive response from the suction surface boundary layer.
Formulation of a Computational Aeroelastic Model to Predict Trim and Response of a Helicopter Rotor System
Authors: Laxman V. , Venkatesan C.
Published: December 2023

Comparison of theoretical and experimental data (flight test data) reveals that still there is a gap between theory and experiment. Some of the observed phenomenon in flight test may be due to the nonlinearities associated with the aeroelastic problems and this paper attempts to develop a theoretical formulation including the geometrical nonlinearities associated with structural modeling and the aerodynamic nonlinearities associated with dynamic stall. In this paper, the consolidated set of equations representing blade dynamics, rotor inflow and sectional aerodynamics are presented. The iterative computational solution technique developed for trim and response analysis is described and a systematic study is undertaken to analyse the influence of various aerodynamic models, representing rotor inflow and sectional loads, on the helicopter trim and aeroelastic response of the rotor blades. It is also shown that the structural coupling due to blade pretwist significantly influences the rotor blade response and loads compared to an untwisted rotor blade.
Bending Vibration and Buckling Analysis Of Nonhomogeneous Nanotubes Using Nonlocal Elasticity Theory and Gdq Method
Authors: Phadikar J. K. , Pradhan S.C.
Published: December 2023

In this paper structural analysis of nonhomogeneous nanotubes has been carried out using nonlocal elasticity theory. Governing differential equations of nonhomogeneous nanotubes are derived. Nonlocal theory of elasticity has been employed to include the scale effect of the nanotubes. Nonlocal parameter, elastic modulus, density and diameter of the cross sections are assumed to be functions of spatial coordinates. General Differential Quadrature (GDQ) method has been employed to solve the governing differential equations of the nanotubes. Various boundary conditions have been applied to the nanotubes. Present results considering nonlocal theory are in good agreement with the results available in the literature. Effect of various geometrical and material parameters on the structural response of the nonhomogeneous nanotubes has been investigated. Present results of the nonhomogeneous nanotubes are useful in the design of the nanotubes.
An Approach for Quick Method of Estimating Passenger And Aircraft Demand for Feeder Air Services in India
Authors: Kodanda B.
Published: December 2023

The recent and the proposed entry of new airlines both in the ‘no-frills’ and in the "full service" categories has completely changed the aviation scenario in India. Obviously this explosive increase in capacity will have a profound effect on the economy of the airlines both in the short term as well as in the long-term period. A growth of over 25% per annum in passenger traffic may not be sustainable for long; thus galloping increase in capacity may result in mergers and strategic alliances of airlines on one side and closing down of some of the airlines on the other side. A point, which is to be noted is that, most of the new entrants also operate in the major trunk routes and serve the metros and the major cities. What appears to have not been tapped is the equally large potential in the regional and short haul sectors, which serve major, and small city pairs and also act as feeders to the major hubs.Realizing the importance of this, the government in its new civil aviation policy has given thrust to regional/ short-haul air travel. In this paper, an attempt is made to review the hierarchy of airline networks in India with respect to trunk, major and feeder routes. The air passenger traffic carried in terms of revenue passenger kilometers (RPK) is compared with upper class rail traffic. The present status of feeder airline services in India is outlined. It is pertinent to study the passenger traffic demand in these feeder routes as compared to upper class rail traffic as some percentage of upper class rail passengers are willing to shift to air travel due to marginal difference between airfare and upper class rail fare and time factor. The future RPKs are forecasted based on the actual RPKs data and the estimated RPKs of earlier market survey. A suitable aircraft size for airline operations in these feeder routes is arrived at based on existing air traffic data by a simplified approach from the basic principles of airline business. A macroscopic measure is used to determine the aircraft demand by assuming average block speed and utilization for each aircraft type. A sensitivity analysis was carried out for various levels of traffic growth keeping in view the sharp increase of air travel in recent years and further growth in air traffic fuelled by feeder sector as the hinterland opens up industry, services and tourism.
Dynamic Stability of an Asymmetric Sandwich Beam Resting on a Paternak Foundation
Authors: Dash P.R. , Maharathi B.B. , Ray K.
Published: December 2023

The parametric dynamic stability of a pinned-pinned asymmetric sandwich beam resting on a Pasternak foundation with viscoelastic core, subjected to an axial pulsating load is investigated. The effects of thickness ratio of two elastic layers (h31), elastic modulus ratio(E3/E1), the ratio of modulus of the shear layer of Pasternak foundation to the Youngs modulus of elastic layer (Gs/E1), the ratio of length of the beam to the thickness of the elastic layer (lh1), the ratio of in phase shear modulus of the viscoelastic core to the Youngs modulus of the elastic layer (G2/E1), the ratio of thickness of Pasternak foundation to the length of beam (δ/l), coreloss factor (η) the ratio of thickness of viscoelastic layer to that of elastic layer (h21) on the non-dimensional static buckling load are considered. In addition to these the effects of the above parameters on the regions of parametric instability have been studied.
Non-local Analyses of Tapered Beams
Authors: Pradhan S.C. , Sarkar A.
Published: December 2023

In the present article bending, vibration and buckling analyses of a tapered beam using Eringen non-local elasticity theory is being carried out. The associated governing differential equations are solved employing Rayleigh-Ritz method. Both Euler-Bernoulli and Timoshenko beam theories are considered in the analyses. Present results are in good agreement with those reported in literature. Non-local analyses for tapered beam with simply supported - simply supported (SS) , clamped - simply supported (CS) and clamped - free (CF) boundary conditions are conducted and discussed. It is observed that the maximum deflection increases with increase in non-local parameter value for SS and CS boundary conditions. Further, vibration frequency and critical buckling load decrease with increase in non-local parameter value for SS and CS boundary conditions. Non-local parameter effect on deflection, frequency and buckling load for CF supports is found to be opposite in nature to that of SS and CS supports. In case of thick beams non-local structural response is observed to be sensitive to length to thickness ratio.
Grid Based Construction of a Composite Micro Air Vehicle Airframe
Authors: Thulasi Durai D. , Viswamurthy S. R. , Balasubramani S. , Rohit C. , Dayananda G. N.
Published: December 2023

The development of a light-weight composite Micro Air Vehicle (MAV) airframe incorporating a novel foam grid based design into Glass prepreg composites is presented. Various combinations of advanced materials are judiciously utilized in different structural configurations to realize diverse requirements in the airframe. Advanced manufacturing techniques such as rapid prototyping, water jet cutting and autoclave curing ensure accurate conformance to the complex contour as well as precise tailored distribution of structural mass. The foam grid based design approach using Glass composites ensures low mass, provides stiffness in multiple directions, imparts crashworthy features and eliminates the problem of electrical leakages. Good correlation between analysis and static test measurement of wing deformation is found. Various issues in the development of a lightweight MAV airframe pertaining to design, tooling, fabrication, testing and analysis are discussed.
Signal Wrap-Around Free Spectral Element Formulation For Multiply Connected Finite 1-D Waveguides
Authors: M.V.V.S. Murthy  , S. Gopalakrishnan  , P.S. Nair
Published: December 2023

This paper presents a novel spectral element formulation based on Numerical Laplace Transforms for the wave propagation of multiply connected finite 1-D waveguides, based on the first order shear deformation theory. The present formulation overcomes the severe short-comings of Fourier transform based spectral element formulation which has serious problems associated with the signal wrap-around while analysing finite domain structures. The real part of the Laplace variable which provides damping to the wavenumber solution, is characterized by Wilcox and Wedepohl approaches. The effect of this damping alters the wave dispersion and introduces certain interesting phenomenon that is not seen in the undamped waveguides. Problems involving wave propagation analysis are solved on finite multiply connected waveguides of varied complexity to demonstrate the efficiency of the formulated element. In most of the examples, the presence of signal wrap-around in Fourier domain based spectral element is brought out. With this approach, any large structural network, consisting of 2-D either metallic or composite finite length waveguides, under high frequency impact loading can be analyzed with very low computational cost.
Study on Extending Range of Artillery Rocket Using Control Surfaces
Authors: R.B. Sarsar  , S.D. Naik  , R.J. Mukhedkar
Published: December 2023

Extension of range of artillery rocket using gliding technique is very effective way. Extension in the range is achieved by control surfaces without adding any extra charge. Controls are applied after completion of launch phase and trajectory is controlled by canards or flat tail control fins. Contribution in this work is to find the optimum time to initiate the controls during the flight so as to get maximum range. Analysis has been carried out using six degree of freedom equations of motion.
Effects of Cutout Location on Postbuckling Responses And Failure Characteristics of Composite Laminate
Authors: Dinesh Kumar  , S.B. Singh
Published: December 2023

The objective of the present investigation is to study effects of locations of various shaped (i.e., circular, square and diamond) cutouts on stability and failure characteristics of simply-supported, axially-compressed quasi-isotropic laminate, (+45/-45/0/90)2s using finite element method. The FEM formulation is based on first order shear deformation theory wherein von Karman’s assumptions are used to incorporate geometric nonlinearity. The 3-D Tsai-Hill criterion is used to predict the failure of a lamina, while the onset of delamination is predicted by the interlaminar failure criterion. It is observed that the location of cutout has a significant effect on buckling and postbuckling strength of the laminate. It is also noted that the laminate with cutout centered at a distance greater than or equal to 0.75b (where, b is the width of the square laminate) from the loaded edge has negligible effect on buckling strength of the laminate.
Numerical Flowfield Visualization Over Heat Shield Of Satellite Launch Vehicle at Mach 0.8 - 3.0
Authors: R. C. Mehta
Published: December 2023

The paper presents a numerical flowfield visualization over a typical payload shroud of a satellite launch vehicle at Mach number range of 0.80 -3.0 and Reynolds number range of 33 x 106 - 46 x 106 /m. The numerical simulation over the bulbous heat shield is carried out by solving time-dependent compressible axisymmetric turbulent Reynolds-averaged NavierStokes equations. The closure of these equations is obtained employing the Baldwin-Lomax turbulence model. A three-stage Runge-Kutta time-stepping scheme has been used in conjunction with finite-volume discretization of the computational domain. The flowfield features over the bulbous heat shield have been analyzed from the velocity vector and the density contour plots. Flow separation on the payload shroud due to the normal shock wave is observed at Mach number 0.80 and 0.90. The normal shock movement on the heat shield is simulated for various transonic Mach number. A recirculation zone of flowfield is formed in the boat-tail region of the heat shield. The vorticity formation ahead of the heat shield moves close to the heat shield with the increasing transonic Mach number, which is observed in the density contours plots of the flowfield. Shock stand-off distance at the supersonic speed is calculated and compared with asymptotic formula of Frank and Zierep. They are found in good agreement.
Computational Study of Supersonic Flow Over a Flat Plate With Protrusion
Authors: Vikram Deshpande  , Sanjeev Sanghi  , Brijesh Eshpuniyani
Published: December 2023

Motivated by a developmental approach of using micro-actuated surface protrusions to control/maneuver slender bodies in supersonic flight, this paper presents a detailed study of a two dimensional laminar supersonic flow over a flat plate with a surface protrusion. The flow field is computed by solving the Navier-Stokes equations using the finite difference method with the particle velocity upwinding scheme (PVUS) for spatial discretization, and the explicit Mac Cormack scheme for temporal integration. A range of free stream Mach numbers (2.0 - 4.5), Reynolds numbers (1000 - 100000) and protrusion heights (0.866% to 8.66% of the characteristic length) has been considered for a thorough parametric study. The parametric study indicates that the oblique shock structure and strength are influenced by all the variables to varying extents. However, the shock location is substantially altered by the protrusion height, Reynolds number, and protrusion shape, while the influence of Mach number is only marginal. An increase in the protrusion height results in an increased wall pressure as well as increased separation lengths on both sides of the protrusion. In contrast, an increase in Mach number increases the wall pressure, but moves the separation point marginally towards the protrusion. Increase in Reynolds number and protrusion bluffness (triangular → trapezoidal → rectangular) increases separation lengths on both sides of the protrusion. In addition to taking a close look at the flow physics, particularly in the protrusion vicinity, considerable attention has also been devoted to important design parameters such as wall pressure, skin friction and the overall normal and tangential force coefficients.
Liquid Propulsion Systems in ISRO - Evolution and Perspective
Authors: Ramakrishnan S.
Published: December 2023

The Liquid Propulsion Systems Centre (LPSC) which was formally constituted as a lead Centre for advanced propulsion systems development in ISRO on 1st June 1987 celebrates Silver Jubilee during 2012. LPSC has the mandate of supporting both the Launch Vehicle and Spacecraft programmes of ISRO. Starting with small Liquid Propellant Control Thrusters and Reaction Control/SITVC system development for SLV-3, today the activities of LPSC have grown many fold and encompasses integration and delivery of Liquid Propellant Booster Stages, Cryogenic Upper Stages and total Spacecraft Propulsion systems. Indigenization and production of Vikas Engine, realisation of Cryogenic Upper Stage for GSLV and the development of 200kN thrust Cryogenic Engine for GSLV-MkIII are some of the challenging assignments handled by LPSC which is also gearing up for the 2000kN thrust Lox-Kerosene Semi-Cryo Engine development. It has been a remarkable span of twenty five years of intense learning and accomplishment.

In this article, based on the AR & DB Satish Dhawan Memorial lecture delivered in June 2012 for Aeronautical Society of India, the evolution of Liquid Propulsion Systems development in ISRO and their increasing role in the current Indian Launch Vehicle programmes as well as the Spacecraft missions viz. IRS, GSAT, Chandrayan etc is described. The new initiatives in advanced propulsion systems such as Electric Propulsion for satellites and 2000kN thrust Semi-cryo engine development for future ISRO launch vehicles are also outlined.
Endurance Life Estimation of Aircraft Compact Heat Exchanger
Authors: Bhaskar A.C. , Palanikumar M. , Ranganayakulu C. , Paul Vizhian S.
Published: December 2023

Heat Exchangers are used in various engineering systems to transfer heat from a hot fluid to cold fluid across an impermeable wall. The necessity of increased heat transfer surface area has resulted in the development of Compact Heat Exchangers (CHE). Due to their compactness, high performances and less weight, CHE is used for aerospace applications. CHE used in combat aircrafts experience arduous and extreme working conditions during their operation. Before its integration with aircraft, CHEs are required to be tested for performance and qualified for airworthiness by evaluating its endurance life. This paper provides the details of the facility established to experimentally evaluate the endurance life. A computational analysis was carried out to estimate the endurance life with respect to fatigue effects using Finite Element Analysis to calculate stress distribution due to pressure and temperature in CHE during maximum and minimum operating conditions. This was then utilized to calculate fatigue life of CHE. The results were compared with experimental data and it is understood that fatigue alone does not determine the endurance life and there are other parameters that significantly influence the life of CHE.
Progressive Failure Analysis of Composite Overwrapped Pressure Vessel
Authors: Vijayakumar R. , Lakshminarayana H.V.
Published: December 2023

Stress and progressive failure analysis (First Ply Failure to Last Ply Failure) of a composite overwrapped pressure vessel (COPV) with an aluminum liner using the finite element method (FEM) in general and commercial finite element analysis (FEA) software ANSYS in particular is presented in this paper. Ply failure prediction is based on failure criteria implemented in ANSYS software. The first-ply failure (FPF) does not necessarily imply the total failure of a laminate. After FPF, the laminate stiffness is reduced consistent with identified ply failure mode. The strength of the composite laminate is evaluated again to see if it could carry additional load. This ply-by-ply analysis progresses, until the ultimate strength is reached. In the present study the methodology is validated using benchmarks and applied to a filament wound fibre reinforced plastic composite pressure vessel with an aluminum liner. Significant results are presented and critically assessed. Directions for further work in this field are identified.
Trends in Simulation Technologies for Aircraft Design
Authors: Pashilkar Abhay A.
Published: December 2023

The developments in flight simulation since its inception are reviewed and the latest trends in the use of modeling and simulation for design of flying vehicles are presented. Mathematical model based system development is now universally recognized as a cost effective way to bring new design concepts into reality. The efforts made at CSIR-NAL in this regard over the years are also described in brief. The design of systems which require scenario based evaluation like the flight control system and avionics benefit from the use of a reconfigurable simulator developed concurrently with the aircraft. A reconfigurable simulator allows for rapid prototyping of the systems during the design phase in an integrated environment. Ideas for the implementation of Systems Engineering concepts in new and existing aircraft programs using mathematical models are discussed.
Reliability Analysis of a Turboshaft Engine
Authors: Lakshmi C. , Raghupathy R. , John Simon K. , Mistry S. N.
Published: December 2023

This paper brings out estimation of Average Service Life (ASL) and Mean Life of a turboshaft engine powering a single engined helicopter. This has been carried out through reliability analysis over defect investigation, repair and overhaul data for a period of 5 years. The implication of ASL and Mean life are deliberated. Critical areas for availability improvement for different operators are also highlighted in the paper.
Defect Trend Analysis for a Low Bypass Turbofan Engine
Authors: Prakash L. , Mishra R. K. , Mistry S. N. , Srinivasan K.
Published: December 2023

Various defects reported during service of a military low bypass turbofan engine over a period are highlighted and their trend is presented in this paper. Causes of these defects are investigated and remedial measures are incorporated to address these issues. Proper maintenance of the engines at engine factory and at operational base as well as strict adherence to the operational limitations will help in reducing the defects maintaining high reliability and safety.
Science, Engineering, Industry and Markets*
Authors: Rajan Y. S.
Published: December 2023

The lecture brings out the distinct aspects of Science, Engineering, Industry and Markets in the contemporary context. It also emphasizes the need to look through their linkages well in advance, if the benefits are to be derived for the economy and society. That in turn will enhance support for science.
Analysis of Functionally Graded Plates and Shells: Stress, Buckling and Free Vibration
Authors: Singh Monslin Sugirtha , Thangaratnam Kari
Published: December 2023

Finite element formulation for Functionally Graded Material (FGM) thin shells subjected to Thermal and Mechanical loads are presented. The power law distribution model is assumed for the composition of the FGM material along the thickness. A software program "COMSAP" has been developed using Semiloof shell element formulation and validation checks are carried out using the results available in the related literature. Results for stress, buckling and vibration analysis of functionally graded shells are reported.
Inception of Casing Wall Flow Instabilities and Downstream Flow Evolution in Subsonic Axial Compressor Rotors At High Rotor Stagger Angles
Authors: Ramakrishna P.V. , Govardhan M.
Published: December 2023

Two critical aspects of the casing wall flow structure in a subsonic axial flow compressor are studied in this paper: flow mechanism leading to stalling at different stagger angle configurations; and the effect of tip leakage flows on these flow phenomena. In some of the previous works, casing wall flow instabilities similar to the ones discussed in the present paper were reported, typically for high stagger angle rotor designs. However under what conditions flow tends to take such shapes were not discussed in detail. This work attempts to address this through a detailed numerical study on unswept and forward swept rotors, for different stagger angle settings, and for varied levels of rotor tip gaps. Three candidate rotors (unswept, 20° true swept, 20° axially swept) are studied with three tip clearances (0.0%, 0.7%, and 2.7% of the blade chord) for three stagger angle changes (0°, +3° and +5°). Stagger angle is found to have significant effect on suction surface flow separations. Tip clearance is observed to be critical on the inception of casing wall flow instabilities, especially at higher stagger angles. Hub endwall flow structure and the downstream flow evolution are also discussed in the paper.
Processing and Friction Properties Evaluation of Multilayer CU Matrix Hybrid Composite Brake Pads for a Trainer Aircraft
Authors: Ram Prabhu T. , Kale S. S. , Yajnapal  , Vaishaki N.
Published: December 2023

We have developed three types of multi layer Cu matrix composite brake pads, namely, Copper-silica-BN, Copper-Si3N4-graphite, and Copper-mullite-MoS2 to solve the problem of static torque, friction coefficient in the upgraded version of Trainer aircraft. These composite brake pads were tested in a full scale brake dynamometer and static torque testing unit at ARDC, HAL. Our results shows that the braking requirements of static torque (~ 204 Kgfm), friction coefficient (~0.3-0.45) were very well met in the multilayer Copper-mullite-MoS2 composite brake pads. The role of MoS2 and Mullite in improving static torque, friction coefficient and stabilizing frictional properties in this composite brake pads were explained in detail.
Numerical Simulations of Supersonic Exhaust Diffuser At Various Operating Conditions
Authors: Mehta R.C. , Natarajan G.
Published: December 2023

A numerical study was carried out to determine starting characteristics of a straight cylindrical supersonic exhaust diffuser of a high altitude simulation of high expansion rocket nozzle. The starting conditions of the supersonic exhaust diffuser are numerically simulated for contour nozzle of exit-to-throat area ratio of 21.77, diffuser diameter-to-nozzle throat area ratio of 23.36, and diffuser length-to-diameter ratio of 15. The evacuation performances of supersonic exhaust diffuser at various operating conditions are investigated with help of the Mach contour plots. The Mach variations along the centre line and wall of the diffuser indicate the location of the shock and flow characteristics. Validation of numerical simulation is carried out with experimental data and shows a good agreement between them. Flowfield inside the straight cylinder supersonic exhaust diffuser is presented out for stagnation to ambient pressure ratio of 5.5 - 28. The nozzle is started at the stagnation to ambient pressure ratio of about 17. The straight cylindrical supersonic exhaust diffuser is started at the stagnation pressure to ambient pressure ratio of about 21. The numerical simulations of the flowfield are able to capture the flows filled in the diffuser and the shock system is fully established in the duct.
Runway Capacity Studies for Major Indian Airports
Authors: Lathasree P. , Pashilkar Abhay A.
Published: December 2023

The two principal measures of performance of Air Traffic management (ATM) systems are Capacity and Delay. Significant growth in Indian air traffic is causing congestions and hence delays in the en-route airspace and at airports. The main reason for the delay at airports is insufficient capacity in terms of facilities such as runways, taxiways or gates to accommodate peak period demands. The delays at airports would cause inconvenience to the passengers, airliners and the airport authorities. The airport runway capacity information will be useful to manage demand and minimize the delay. Prediction of runway capacity aids in developing strategies for efficient air traffic management. This paper presents the airport runway capacity studies carried out using Time Space diagrams for major Indian Airports.
Pyroshock Isolator for Spacecraft Applications
Authors: Ravi Kiran N.K. , Patnaik M.N.M. , Shankar Narayan S.
Published: December 2023

Pyroshock produced by pyrotechnic devices are the most severe shock experienced by spacecraft and its components. In spacecraft pyro devices are used for deployment appendages and mounted on spacecraft with critical electronic equipments placed in their near field and mid field. Attenuation of the pyroshock levels transmitted to these equipments is attempted by providing passive isolator at the base of the pyro devices. The isolator material for spacecraft application is to be space qualified and the isolator dynamics to be uncoupled from spacecraft modes to survive launch loads. The isolator stiffness is arrived based on load characterisation tests done on the damper material and the isolator configuration is adaptable for mounting on spacecraft with restrictions in size, mass etc. Design of the isolator is done based on stiffness to achieve the isolation at high frequencies as well as to survive the launch loads. The shock attenuation of the order of 20 dB at high frequencies is achieved.
Effect of Turbulence Model and Spray Parameters on Kerosene Fuelled Scramjet Combustor
Authors: Dharavath Malsur , Manna P. , Chakraborty Debasis
Published: December 2023

Numerical simulations are carried out for scramjet combustor with fuel injector struts to evaluate its performance for ground test conditions. Simulations were carried out for non-reacting and reacting flow with equivalence ratio of 1.0. CFD predicted top wall pressure compared reasonably well with experimental results except the upstream (ahead of the fuel injection) regions of the combustor where CFD has predicted higher values compared to the measured values. Effect of various spray distribution and turbulence models on wall pressure distribution and performance of the combustor studied. SST-kw turbulence model has predicted close to experimental data at upstream of combustion compared to k-e, k-w turbulence models. The net calculated combustion efficiency and achieved thrust at exit of combustor are 3% and 2.7% respectively higher in k-w compared to SST-kw though total pressure recovery in all three cases are almost similar.
Swift Assessment of Flexible Elements of High Speed Flexible Couplings for Aircraft Transmission Systems
Authors: Nagesh S. , Junaid Basha A. M. , Dinesh Singh Thakur
Published: December 2023

The High Speed Flexible Coupling (HSFC) known as Power Take-Off shaft (PTO) is used in combat aircraft for connecting engine gearbox with accessory gearbox to transmit power and to accommodate larger misalignments. The HSFC utilizes series of metallic contoured plates as flexible elements. The development of a HSFC shaft assembly involves high cost and time process. Any failure of the HSFC during flight operation will deprive the secondary power system mainly used for controlling the single engine fighter aircraft. To develop the reliable HSFC with minimum developmental cost and time, an innovative approach termed as Swift Assessment of Flexible Elements (SAFE) for the development of HSFC is evolved. A case study of a typical high speed flexible coupling developed using this approach is presented With the SAFE approach, sufficient level of flexibility in design modification, trim down product development cycle time and cost were realized.
Guidance of Flight Path in TMA During Landing - A Design Study
Authors: Roshini M. , Subba Reddy B.
Published: December 2023

Air traffic has grown over the last few decades and is increasing further to a state where many airports and especially big hubs are reaching their limits of capacity. Hence many research activities were initiated to come up with more efficient and safe flight operations including Flight Path Boundary approach for controlling Time-of-Arrival in the terminal area. The design studies presented in this paper investigate a simplified representation of an intermediate flight path in the Vertical Situation Display for meeting the Time-of-Arrival requirements. A guidance law for maintaining constant EAS during descent has been evolved to adjust the thrust based on variation of air data measurements. Simulation results for typical case studies are presented to validate the approach. Possible areas for further extension are highlighted.
Effect of Double Impulse Trajectory Transfer from Earth to Mars Mission
Authors: Xavier James Raj M. , Mutyalarao M.
Published: December 2023

The interplanetary mission from Earth to Mars takes at minimum energy launch opportunity with a single impulse transfer. Due to some unavoidable circumstances, if the launch takes at a later date, other than the minimum energy launch opportunity then the energy requirement increases. Also if the terminal states, approach the condition of opposition, the energy requirements rapidly increase and become infeasible too, resulting in restrictions on the launch window. This is due to the relative inclinations of the two planets. To overcome this situation, the possibility of applying an intermediatory impulse between the two terminals, named as double or two impulse transfers is considered. This paper gives the necessary details for the double impulse transfer and draw attention to its advantages.
Aero-Propulsive Characterization of a Flight Vehicle with Two Side-Jets
Authors: Balasubramanian R. , Dayal Jessy Prabhu , Krishnamurthy R. , Chakraborty Debasis
Published: December 2023

Numerical simulations were carried out to study the aero-propulsive characteristics of a flight vehicle using in-house developed Reynolds Averaged Navier-Stokes code CERANS. The analyses involved subsonic external flow with inclined supersonic dual sustainer jets at various angles of attack, roll orientations and side slip. The control characteristics of the configuration are evaluated for the flow with and without sustainer jets. Numerical simulations indicated that the jet plume exhausting out of the scarf sustainer nozzle grazed and clung to the airframe for a considerable downstream distance causing serious damage to the airframe. This numerical study led to an important design change of the sustainer nozzle shape from ‘scarf’ to ‘conical’ which alleviated plume interference problem with the airframe.
Thermal Postbuckling of Heated Columns of Variable Cross-Section - A Simple Intuitive Formulation
Authors: Venkateshwarlu N. , Kishen Kumar Reddy T. , Akella Suresh , Venkateswara Rao G.
Published: December 2023

The thermal postbuckling of heated slender columns of variable cross-section (tapered columns) is evaluated by a simple intuitive formulation, when compared to the poplar Rayleigh-Ritz method. The intuitive formulation requires only two parameters, namely, the mechanical equivalent of the thermal buckling load parameter and the constant tensile load parameter induced in the column, due to moderately large deflections, when the ends of the column are fixed axially. The thermal buckling load parameter of tapered columns is obtained from the Rayleigh-Ritz method. The symmetric boundary conditions, like hinged-hinged and clamped-clamped conditions, are considered for the tapered columns, which are consistent with the symmetry of the tapered column. The ratio of thermal postbuckling to buckling loads obtained from the simple intuitive formulation, varying with the taper and central deflection ratios, are presented for hinged-hinged and clamped-clamped tapered columns, which match very well with those obtained by Rayleigh-Ritz method, which is a validation of the simple intuitive formulation.
Computational Investigation of Effect of Tip Clearance in an Annular Turbine Rotor Impulse Cascade
Authors: Goutham Kumar K. , Sitaram N.
Published: December 2023

This paper describes three dimensional computational investigations of the effect of the tip clearance on the secondary and tip clearance flows in an annular turbine rotor cascade with non uniform inlet flow. In the actual turbine, the flow at inlet of the rotor is non uniform due to radial pressure gradient acting from the hub to casing. To provide non uniformity at the rotor cascade inlet, an annular nozzle cascade is provided at the upstream. The studies are carried out with the help of a commercially available CFD package. The studies have been carried out for four values of clearance, i.e. 0%, 1%, 3% and 5% of chord. Detailed comparison of the leakage flow direction, pressure gradient, and leakage vortex size, losses, location and interaction with other flow features is carried out. The results are presented in terms of static pressure coefficient distribution on the blade surfaces and total pressure loss coefficient contours in the passage. Spanwise distributions of the circumferentially averaged loss coefficient and flow angle are presented. The extent of losses in the circumferential direction is increased with the increase in the height of the tip clearance but reduced in the spanwise direction. The mass averaged loss coefficient increases rapidly from 0.24 at zero clearance to 0.42 at 1% tip clearance. As the tip clearance is further increased, the losses increase slowly (0.54 at 3% tip clearance to 0.58 at 5% tip clearance). The mass averaged flow angle decreases from 66.3° at zero clearance to 63.7° at 1% clearance to 60.1° at 3% clearance and to 57.3° at 5% clearance.
Orbit Predictions Using KS Elements With Earth’s Flattening
Authors: Saritha Kumari T. R. , Xavier James Raj M.
Published: December 2023

Predicting the orbit of a satellite is a fundamental requirement in many areas of aerospace, such as mission planning, satellite geodesy, re-entry prediction, maneuver planning, collision avoidance, formation flying, etc. For near-Earth orbits, the forces due to the non spherical nature of the Earth and atmospheric drag plays an important role and are mainly responsible to bring the satellite back to the Earth. Thus inclusion of the effect of these perturbing forces becomes important for precise orbit computation of near-Earth orbits. Many transformations have emerged in the literature to stabilize the equations of motion either to reduce the accumulation of local numerical errors or allowing the use of large integration step sizes, or both in the transformed space. One such transformation is known as KS transformation by Kustaanheimo and Stiefel [1], who regularized the nonlinear Kepler equation of motion and reduced it into linear differential equations of a harmonic oscillator of constant frequency. In this paper a detailed analysis is carried out for orbit prediction using KS differential equations by including the non spherical gravitational potential of the Earth as the perturbing force. Earths zonal and tesseral harmonics, which produce bands of constant deviation from the spherical field along lines of latitude and longitude, are included to precisely model the Earth’s gravitational potential. Higher order Earth’s flattening terms are included by utilizing the recurrence relations of associated Legendre polynomial and its derivatives. To know the effectiveness of the theory, the results are compared with the real IRS-1A satellite data and the results of other existing solutions for a long duration of nearly a month time. The comparison shows that the KS method provides one of the most and accurate techniques for orbit prediction available at present.
Development of Hud Symbology for Enhanced Vision System
Authors: Kashyap Sudesh K.
Published: December 2023

Head-up display is one of the important sub-systems of aircraft avionics suite for enhancing pilot situational awareness for smooth and safe gate-to-gate operations especially during take-off, approach and landing phases of flight. The Head-up display consist of generic and advanced sets of symbologies mainly categorized as i) conformal: such as local horizon, airport/runway, highway-in-the-sky, pitch ladder, etc and ii) non-conformal: airspeed, altitude, heading, roll, horizontal situation indicator etc. These symbologies can be combined or overlaid with more advanced systems such as Enhanced vision system/synthetic vision system to increase pilot situational awareness in case of poor weather conditions/ degraded visual environment. This paper presents development of generic and enhanced vision system specific Head-up display symbologies based on Gulfstream G450 Head-up display standard and its integration with in-house developed Enhanced synthetic vision system flight simulator.
Numerical Predictions of Soot Formation in Kerosene/Air Jet Diffusion Flame
Authors: Saini Rohit , De Ashoke
Published: December 2023

Soot volume fraction in a turbulent diffusion flame burning kerosene/air is simulated using steady flamelet approach. The soot inception model based on the formation rate of three and two ring aromatics is used, which further accounts for inception, coagulation, surface growth, and oxidation processes. The Favre-averaged governing equations of mass, momentum, and energy are solved in conjunction with k-? turbulence model in ANSYS-FLUENT. The fairly detailed reaction mechanism for kerosene/air is coupled to the turbulent flow field by steady laminar flamelet approach, while the soot is calculated using Moss-Brookes model. The predictions are found to match well with the measurements where no significant effects are observed with the inclusion of higher order hydrocarbon as precursors and surface growth.
Look Up Table Method for Five Hole Probe Data Reduction
Authors: Sitaram N. , Suresh M. , Kumar Satyansh , Dileep Chandran P. M. , Prasad B. V. S. S. S.
Published: December 2023

A lookup method for extracting flow field information from five hole probe measurements is presented. The look up table method consists of two step interpolation. In the first step, the calibration space is divided into a large number of small intervals of yaw and pitch coefficients (0.1, 0.05 or 0.01) and the required quantities are interpolated using local cubic spline interpolation technique. The interpolated values are stored in a large square matrix. In the second step, the measured values of yaw and pitch coefficients are used to determine yaw and pitch angles by linear interpolation. Same procedure is used to determine total and static pressure coefficients. Additional data taken during the calibration is used for validating lookup table method and spline interpolation method. The errors from the look up table method, particularly with the interval of 0.01 are about the same or lower than those obtained from the spline interpolation method. The computational times for lookup table method are found to be lower than that for the spline interpolation method. The lookup table method seems to be attractive when a large amount of five hole probe data is to be processed and in cases where online data processing is required.
An Integrated Mutation Analysis Tool (Imat) For Simulink Models and Their Ideal Implementation
Authors: Nanda Manju , Jayanthi J. , Madhan V. , Nayak Sameer
Published: December 2023

Mutation analysis is proving to be an effective approach in detecting the design flaws for safety system designs such as flight control systems or the stall warning systems. The drawback of these analyses is that they are time-consuming and difficult-to-use. This paper discusses about the mutation tool, IMAT, developed in-house for detecting the design flaws of safety critical systems designed in SIMULINK. The IMAT tool is developed as a plug-in to the SIMULINK tool suite and enhances the performance of the model-based development of safety critical systems. Some of the unique features of the tool are ease-of-use, portable, scalable, userfriendly and easy to analyse the reports.
A More Accurate Systems Modelling and Simulation Framework in Design and Optimization of A System During the Conceptual Phase
Authors: Shanmuganathan Hariram
Published: December 2023

Modelling and simulation of complex mechanical systems involving multi-simulation environment, with great accuracy is essential as part of the conceptual design phase of a system under design. The co-simulation between system level model with various subsystems based on Model Based Design (MBD) and component level model is a perfect example. These mathematical models have distinct features such as the type of differential equations used to represent its physics, boundary conditions etc. In this study we use MBD methodology to develop a simulation model that can drive product development and optimization of mechanical systems. We also incorporate a 3-D Computational Fluid Dynamics (CFD) model as one of its subsystem into the System Level (SL) model architecture. This is done by creating a co-simulation interface between these two different modelling environments and exchange boundary conditions via a specific interface. The interaction between multi-domain models through system simulation together with the detailed fluid flow and thermal analysis of the component through CFD is finally explained. Finally, the dynamic behaviour of the complete system and its temporal and spatial scales is shown to be captured in more detail.
Formation Flying Recognition With Dual Layer Interval Type 2 Fuzzy Logic
Authors: Shrinivasan Lakshmi , Raol J. R.
Published: December 2023

Formation flying of aircrafts is critical in aviation especially in combat situations. The existing type 1 fuzzy logic system (T1FLS) used for formation-flight recognition, though very useful and successful may exhibit some inaccuracy in presence of uncertainties and/or noise. To overcome this and to design robust real time systems, this paper introduces an interval type 2 fuzzy logic system for decision fusion (IT2FLSDeF) for formation recognition. The performance of the proposed decision system is evaluated under ideal and realistic conditions. The results indicate that better performance of compared to its type 1 counterpart for the cases studied is achieved.
Heat Transfer and Friction Correlations for R134a With Offset Strip Fin Surface
Authors: Amaranatha Raju M. , Ranganayakulu C. , Ashok Babu T. P.
Published: December 2023

Single phase heat transfer analysis of R134a refrigerant (liquid phase) has been carried out using Computational Fluid Dynamics (CFD) approach for offset strip fin. Colburn j factor and Fanning friction factor are predicted for offset strip fin. The correlations are developed at Reynolds number range of 100-15000. The effect of fin geometry (fin spacing, fin height, fin thickness and lance length) on the enhanced heat transfer and pressure drops were investigated. Colburn j factor and fanning friction factor f, correlations have proposed in terms Re and geometry parameters (h/s, t/s, t/l) for liquid refrigerant R134a in the present study. Two separate correlations have proposed for the low and high Re regions i.e. Between Re of 100-1000 and Re of 1000-15000. The numerical results are validated with experimental results, results are found in good agreement with experimental results. Variation is found less than 5%.