bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Bearing Characteristics on Frequency Ratio of Rotor System
Authors: Maharathi B.B.
Published: December 2023

Bearing characteristics play a major role for dynamical analysis of rotor-disk system. The dynamic characteristics include such as, critical speed, dynamic response, perfect balancing, threshold speed of instability 6n4 selection of optimum as well as stable bearings for rotor dynamics. This work highlights the comparison of stability characteristics of any rotor-disk model mounted on various kinds of hydrodynamic journal bearings with different length/diameter ratios. The bearings which are considered in this work are; the two-axial groove bearing, the four-axial groove bearing, the elliptical bearing, the two lobe bearing, the three-Lobe bearing and the off-set cylindrical journal bearing with 0.5 and 1.0 as its Length to diameter ratio. From the analysis is observed that the off-set cylindrical journal bearing is more stabLe than other bearings for any rotor model within the operating speed range. A three disks-rotor-bearing model mounted on different hydrodynamic journal bearings has been used for its dynamical analysis by using transfer matrix method based on continuous system model.
UAVs - The Indian Road Map for Development
Authors: Limaye Malathi
Published: December 2023

The last century saw the birth of the 'First Engine Powered heavier than air' aircraft flight by the Wright Brothers' and within fifty years air power became the key to supremacy in the war game. Today the focus has shifted to include 'Unmanned Aerial Vehicles'(UAVs). UAVs range from the 100 gram Micro-UAV to the High Altitude, Long Endurance and Unmanned Combat aircraft. Primary roles even today are 'Intelligence, Surveillance and Reconnaissance' (ISR) but 'Combat UAVs' are expected to come into operation within l5 to 20years. UAVs conceived originally as desirable low cost, 'eyes-in-the sky' are today key assets in the military tool kit. The paper focuses on some of the issues and technology challenges associated with UAVs and provides a glimpse into the DRDO road map for development of UAVs.
Flow Field Over Boat-Tail Region of Heat Shield of a Typical Launch Vehicle at Mach 2
Authors: Srinivasan K. , Chattopadhyay Sandip , Raveendran P.G. , Unnikrishnan C. , Murugan B.
Published: December 2023

Boat-tailed heat shields offer a higher payload volume but lead to flow separation and associated effects. In the present paper an attempt is made to find out the effect of boat-tail angle on the over all flow field with special emphasis on acoustic load near the boat-tail region. Experiments and CFD routes are used to investigate the flow field. Experiments consist of steady and unsteady pressure measurements and flow visualisation through schlieren and oil flow. CFD simulations are also carried out for the wind tunnel conditions. Results indicate that fluctuating pressure co-efficient increases with flow separation, peaks at reattachment point and reduces further downstream. An Increase in boat-tail angle from 20" to 30" leads to about I2Vo increase in acoustic load-s. All these studies were carried out at a Mach number of 2 and a Reynolds number of 4 x t}o based on model length.
Vortex-Resonant Sound Interaction in a Duct Containing an Orifice
Authors: Karthik B. , Venkateswarlu N. , Kowsik B.V.R. , Chakravarthy S.R. , Sujith R.I. , Tulapurkara E.G.
Published: December 2023

This paper reports the results of a set of experiments involving the passage of flow through a constriction - a single orifice - located in the middle of a duct. Geometric variations during testing include the length of the duct, orifice size, and orifice thickness. Acoustic oscillations in the duct were measured by systematically varying the flow rate for each. combination of geometric variables. Hot wire measurements were performed, in the region downstream of the orifice, under select conditions. The results indicate the excitation of clearly audible, discrete sharp tones of high amplitude that abruptly shift frequencies as the flow rate is increased within a certain range. The excited frequencies are related to fairly high harmonics of the natural acoustic modes of the duct. Simultaneous measurements from the hot wire and the microphone show the same frequency. This suggests the prevalence of a "lock-on" type of phenomena as reported earlier with two orifices. The effect of increase in the orifice diameter is to decrease the range of frequencies when the sharp tones are heard. Some evidence is presented that suggests the critical role played by the thickness of the orifice in exciting these sharp tones.
Finite Element Analysis of a Beam With Active Constrained Layer Damping (ACLD) Treatment+
Authors: Langote Pankaj K. , Seshu P.
Published: December 2023

Active Constrained Layer Damping (ACLD) treatments with active piezoelectric materials and passive Visco-Elastic Materials (VEMs) combine the advantages of both conventional Active Damping (AD) and Passive Constrained Layer Damping (PCLD) treatments. A beam Finite Element (FE) model has been developed for the beam partially covered with ACLD treatments on both sides of beam. For modeling the frequency dependent damping behavior of the VEM, the Golla-Hughes-McTavish (GHM) model has been used. In all, four systems have been studied viz., bare beam, beam-piezo (AD), beam-VEM (PCLD), and beam-VEM-piezo (ACLD). A set of experiments has been conducted on all the systems. A very good match between theoretical and experimental predictions, in terms of free vibration response as well as closed loop feedback controlled dynamic response, has been established.
Experimental Studies on Atmospheric Pressure Glow Discharge For Drag Reduction and Microwave Invisibility
Authors: Srivastava A.K. , Prasad G. , Kumar Vinay , Chawdhuri M.B. , Prakash Ram
Published: December 2023

Absorption and reflection of microwaves from plasma with electron density gradients and reduction of frictional drag force on moving aircrafts are the important issues of atmospheric pressure plasma applications. For these purposes several thermal and non-thermal plasma sources have been developed that work near atmospheric pressure. The characterization of these plasmas has also been done by many researchers using mostly spectroscopic techniques. The Langmuir probe diagnostic, inspite of its theoretical limitation at high collisional regime, has also been reported in many experiments to characterize high-pressure plasmas. We are reporting the comparison of two diagnostic techniques i.e. Langmuir probe and emission spectroscopy for atmospheric pressure glow discharge plasma in helium. For the measurement of plasma parameters, ramped probe I-V characteristics curves were used for probe diagnostics and line intensity ratios were used for spectroscopic diagnostics. An attempt has been made to crosscheck the measurements using different techniques for their validation. The variation of the plasma parameters i.e. electron density and temperature with external tunable parameters viz. applied voltage and frequency is also investigated to find the scaling of plasma parameters with external controls. Estimated electron density is ~1011 cm -3 and electron temperature is ~10 eV. Measured plasma parameters indicate suitability of the plasma which can be exploited for microwave invisibility.
Role of Computational Fluid Dynamics in the Design of Aerospace Configurations
Authors: Chakrabartty S. K.
Published: December 2023

Computational Fluid Dynamics (CFD), a mature discipline now, can contribute considerably to the design, analysis and development of engineering systems involving fluid flows. Visualization of flow-field, surface load distribution and various aerodynamic forces and moments are the criteria for basic design of aerospace configurations. CFD complements experimental and theoretical fluid dynamics by providing an alternative and cost effective means to simulate real flow phenomena. The main advantage lies in its ability to cut down the number of wind-tunnel tests leading to reduction in the design cycle time and design cost. After a brief introduction to CFD, the role played by the modern CFD tools developed at the Computational and Theoretical Fluid Dynamics Division of National Aerospace Laboratories, Bangalore in the design and analysis of Aerospace configurations will be discussed here.
Cfd Tools as Applied to Indian Combat Aircraft Configuration-an Experience
Authors: Singh K.P.
Published: December 2023

Computational Fluid Dynamics (CFD) tools are extensively used by aircraft industries all over the world in design and development of airplanes, with emphasis on reducing both the cost and design cycle time. This paper deals with the use of CFD tools at Aeronautical Development Agency (ADA) in design and development of Indian combat aircraft. The applications include: (1) evaluation of incremental changes in aerodynamic configuration, (2) wave drag evaluation, (3) aerodynamic loads, (4) flow field around air data sensor locations, (5) Euler calculation for coupled internal and external flow field, and (6) viscous computation of high angles of attack flows. In the initial design phase, codes based on the potential theory were used for wing design and fuselage shape optimization. Later indigenously developed Euler and Navier-Stokes codes were employed for the various applications. This paper brings out the strength and weakness of CFD as experienced at ADA and its comparison with the Wind Tunnel and Flight Data.
Advances in Aerial Image Exploitation
Authors: Majumdar Jharna
Published: December 2023

The availability of low cost sensors, high bandwidth communication links and the growing popularity of Unmanned Aerial Reconnaissance Platforms like UAVs have resulted in dramatic new opportunities to conduct remote battlefield surveillance and reconnaissance missions from relatively safe Ground Control Stations. The sensors used in UAV explore the visible, infrared and microwave regions of the spectrum and the images are produced optically, electronically or by film. Aerial Image Exploitation is an innovative image utilization program that uses multi sensor, multi resolution and multi spectral imagery obtained from Aerial Reconnaissance Platform for the purpose of Extraction, Exploitation, Dissemination and Interpretation of Imagery Intelligence. Research in aerial image exploitation is focused to provide a total solution of the problem by combining both hardware and software at the system and subsystem level. Major operational goal of image exploitation technology is to extract the vital intelligence from a large storehouse of available imagery by filtering those which are most likely to produce valuable findings, to combine classical image/signal processing techniques with technologies available in other fields and to use specialized hardware wherever required. The first part of the paper describes the Ground Image Exploitation System and Imagery Intelligence Exploitation System being developed in ADE. The second part of the paper describes some of the basic and advanced research work being carried out in ADE, which is the backbone that lead to the development of these systems. Some of the areas discussed in this paper are adaptive preprocessing of imagery, image mosaicing, terrain classification and high-resolution reconstruction of target region.
Green Engine Technologies for Small Gas Turbines
Authors: Sampath Sam , Moustapha Hany , Girard Gaetan , Cooper Colin
Published: December 2023

The small gas turbines industry has witnessed a big leap in technology over the past two decades. This period was mainly characterized by a rapid development of advanced three-dimensional tools assisted by a yearly doubling of computer capacity. Validated design tools were integrated into the design system throughout the whole engine. Concurrent engineering combined with integrated product teams and a substantial reduction in testing has resulted in a reduction, of an engine design and development time, from five to three years. Further reduction to two years is possible with emphasis on technology readiness both in engineering and manufacturing. Technology strategy for the next millennium will focus on cost reduction breakthroughs, and rapid technology deployment into engines. Environmental issues such as noise and emissions reduction and elimination of hazardous waste will take more importance, particularly with more stringent regulations. This paper addresses Green engine technology developments in modern gas turbine engines.
Evolution of Airframe Materials for Russian Fighters
Authors: Kale Shirish , Biswas Kanchan
Published: December 2023

Fighter aircraft make extensive use of materials such as Steels, Aluminum alloys, Magnesium alloys, Titanium alloys and composites for construction of airframe. It has been seen that many of the airframe materials used in Russian fighters are common. But attempt has been made to introduce progressively superior quality alloy grades in the later version of aircraft. A comprehensive study (1) is thus made to identify the important structural member of the airframe and its materials in different generations of the Russian fighters to highlight the ways lighter and superior alloys replaced steels. This paper describes the application of various aerospace materials used from the evolution of old generation Russian combat fighters to latest Russian fighters. Effort have been made to analyse and explain the change of some of the grades within the domain of these Russian fighters and use of superior structural materials (western and Russian origin) to old age aircraft to enhance the performance. It also discusses the percentage weight change of various types of materials used in the construction of Russian fighter aircrafts under operation in India. Main objective of this study which is discussed here, to keep aware the operators as well as manufacturer’s of Russian aircrafts within India to exchange these Russian materials during rationalization, substitution, indigenization and at a times of short supply or non-availability of these grades based on their merits.
Life Cycle Cost of a Six Ton Helicopter
Authors: Satpathy N. , Murari Krishna
Published: December 2023

The operating cost of a helicopter basically comprises of Direct operating cost and fixed operating cost. Direct operating cost are those costs that are related directly to the hourly operation of the helicopter. These are cost of fuel, lubricants, maintenance, overhaul, replacement of parts for the Airframe and engine. The fixed operating costs are those related directly to crew cost, insurance cost, depreciation, Hangar rentals, landing charges etc., This paper gives a method to calculate the direct and fixed operating cost for a 6 ton class civil helicopter. Realistic assumptions are made in the calculation taking into account prevailing rates wherever applicable. This cost is compared with the operating cost of various other presently flying helicopters of same category. Although operating cost of fixed wing levels can not be achieved, helicopter operators can economically compete in the short haul transportation markets where VTOL capabilities offer unique advantage. Operating cost can be reduced by Technology improvement, low cost design philosophy and progressive business policy.
Experimental and Numerical Prediction of Surface Crack Growth in Fatigue in a Finite Width Plate
Authors: Patel S. K. , Dattaguru B. , Ramachandra K.
Published: December 2023

In the thick components such as gas turbine disks, the cracks usually manifest in the form of part-through or embedded elliptical cracks. The shape of surface crack varies during the crack propagation and significantly affects the fatigue life predictions of the surface cracked components. In present work, crack propagation of semi-elliptical cracks in a finite width specimen of a gas turbine material subjected to fatigue load has been studied experimentally and numerically. The numerical simulation was accomplished by first extending the applicability of available stress intensity factor empirical equation for semi-elliptical cracks to finite width solid. Using this empirical equation for stress intensity factor, the effect of change in the crack shape on the crack propagation life is simulated by numerical models. Also, in order to include the effect of crack closure in the numerical prediction of growth of surface cracks, a ratio of crack closure factor between depth and surface locations of a semi-elliptical crack was obtained by experiments. The experimental observations were used in correlating the numerical predictions for crack shape progression and crack propagation life.
Development of Mathematical Model of a Generic RLV for Reentry Mission Simulation
Authors: Joshi Ashok , Sivan K.
Published: December 2023

This paper presents the nonlinear models for simulating the atmospheric reentry dynamics of a generic Reusable Launch Vehicle (RLV). The six degrees-of-freedom flight dynamics is modeled with the overall objective of minimum number of constraints without increasing the complexity of equations. This requirement leads to the definition and use of a number of frames of reference for describing different aspects of the dynamics of the RLV. In this context, the inertial reference frame is used for translation motion, while body frame and wind frame are used to describe the forces acting on the RLV. Further, quaternion representation is used for vehicle attitude motion in order to avoid computational singularities in respective kinematic model equations. The vehicle complex aerodynamic characteristics are modeled using the coefficient approach in order to simplify interpretation of available data while the propulsion system model takes into account the atmospheric conditions. The vehicle subsystem models of sensors, navigation system and actuators are also included. The operating environment models viz., Earth’s atmosphere, Earth’s shape and gravitational acceleration are also modeled appropriately. The model presented is for a generic RLV and has the potential for application to RLVs of widely different configurations.
Damage Tolerance Evaluation of Wing Bottom Skin Panel of an Aircraft
Authors: Iyer Nagesh R. , Murthy A. Rama Chandra , Rajasankar J. , Palani G.S.
Published: December 2023

This paper presents the details of damage tolerance evaluation of a Wing Bottom Skin Panel (WBSP) of an aircraft. Finite element analysis (FEA) of an integrally stiffened WBSP has been conducted to identify the probable location for crack initiation and the same has been confirmed by conducting experiments. Linear elastic fracture mechanics (LEFM) principles have been used for computation of stress intensity factor (SIF). Static results obtained from FEA and experiments are found to compare well. SIF has been computed for different crack lengths in mode I under intact-stiffener condition by using displacement extrapolation and strain energy release rate (SERR) techniques. SIF has also been computed for the same crack lengths under broken stiffener and unstiffened conditions. A comparison between the residual strength predicted under intact-stiffener, broken stiffener and unstiffened conditions clearly indicates the efficacy of the stiffener in arresting the crack propagation.
Generic Components based Expert System Shell for Avionics Applications
Authors: Santhi seela R. , Janarthanan S.
Published: December 2023

This paper focuses on the construction of a Generic Components Based Expert System Shell for various avionics applications. Traditional Expert Systems have been constructed using a single monolithic software program for a specific application. In traditional/commercial Expert System, either the Knowledgebase is hard-coded into the program or the linking of the Expert System modules with the knowledge bases takes place during compilation time. These commercial Expert Systems can’t be used for complex applications where multiple knowledge bases have to be handled at run time, because the coupling of any particular knowledge base needs either the alteration of program code and/or recompilation. Secondly all these commercial Expert Systems are working in interactive mode during the inference process. To overcome these problems, ADE (Aeronautical Development Establishment) is currently involved in the design and development of a complex competent shell i.e. A Generic Components Based Expert System Shell for Avionics applications. This shell works in automatic mode and the system engineer can easily configure these generic components into a domain-oriented solution for any complex application including applications where multiple knowledge bases are handled. In this paper, we are discussing the role and generic nature of this shell along with its components and how they are configured as a domain-oriented solution for different kinds of applications at ADE.
Tracking of Multiple Targets Using Interactive Multiple Model and Data Association Filter
Authors: Kashyap Sudesh K. , Naidu V.P.S. , Singh Jatinder , Girija G. , Raol J.R.
Published: December 2023

Tracking of multiple targets using interactive multiple model and data association filter has been developed on PC MA TLAB. The performance of the algorithm is evaluated in terms of estimated and measured tracks in presence of clutter, mode probability, standard deviation, root mean square position error and with varieties of simulated scenarios. Sensitivity of the algorithm to the choice of tracking models and process noise covariance values has been studied. This algorithm has also been evaluated for multi sensor multi target scenario using fusion technique. It was observed that interactive multiple model probabilistic data association filter gives a realistic confidence in the estimates during maneuvers and lower RSSPE during the non-maneuvering phase of the targets.
Effectiveness of Discrete Piezo-patch Locations in Clamped-simply Supported Plates
Authors: Joshi Ashok , Khot S. M.
Published: December 2023

Present study investigates the problem of determining the control effectiveness of piezoelectric patches for controlling vibration in higher modes of clamped-simply supported plates. A modal analysis approach is used to identify high average strain (or curvature) locations, as desired patch locations and represented in the form of geometrical parameters. The 9-patch configuration is used and modal analysis of integrated structure is carried out, which clearly shows that the initial patch configuration yields better effectiveness for square plates. In case of rectangular plates, the above strategy provides mixed results for the patch distribution effectiveness, for the modes considered here. Next, a concept of ‘stretching’ the patch distribution is applied for improving the effectiveness of the patch distribution and a Fig. of Merit (FOM), based on modal strains, is defined for quantifying the effectiveness. The results show that particular patch distribution geometry is suitable only for a specific group of modes. In view of this, a combined Fig. of Merit, based on the concept of modal weights, is also introduced, which has the potential to help in determining a suitable patch distribution through a formal optimization methodology. The control effectiveness comparison study of the initial and stretched patch configuration of plates also supports the quantification of control effectiveness of patch configuration through the FOM.
An Experimental Study on the Upstream and Downstream Influences of Rectangular Cavities
Authors: Mukhopadhyay Suparna , Chaudhry K. K.
Published: December 2023

Experiments have been conducted on the separated and reattached flows of tunnel wall cavities along with relatively thick approaching boundary layers in incompressible flows. For very shallow cavities, approaching boundary layer thickness affects the base pressure whereas for deep cavities, its effect is minimal. In shallow cavities, the maximum pressure occurs slightly below the shoulder of downstream wall. In deep cavities the vortical flow will have sharp curvature of streamlines at the rear shoulder showing a higher static pressure.
Exploration and Utilization of Moon
Authors: Abdul Kalam A.P.J.
Published: December 2023

No Abstract
Supersonic Plug Nozzle Conception and Comparison to the MLN Configuration
Authors: Zebbiche Toufik , Youbi Zine Eddine
Published: December 2023

A method to design the contour and conception of a plug nozzle of arbitrary shape, but specified exit flow conditions is presented. Severals shapes can be obtained for exit Mach number by changing the specific heats ratio. The characteristics of the nozzle in terms of length, weight and pressure force exerted on the wall are compared to the Minimum Length Nozzle and found to be better. Our field of study is limited to the supersonic mode to not to have the dissociation of the molecules. The design method is based on the use of the Prandtl Meyer function of a perfect gas. The flow is not axial at the throat, which may be advantageous for many propulsion applications. The performance benefits of the plug nozzle compared to the Minimum Length Nozzle are also presented.
Pilot Command Implementation in Aircrafts: A New Approach Based on Dynamic Inversion
Authors: Padhi Radhakant
Published: December 2023

A new approach based on dynamic inversion is proposed in this paper for implementing pilot commands in an aircrafts. The command inputs from the pilot are assumed to be (i) the normal acceleration and forward velocity commands in the longitudinal mode and (ii) roll rate, height and forward velocity commands in the lateral mode. A major difference here is that the second derivatives of the velocities along body y and z directions are assumed to be zero, as opposed to the first derivatives (which is used in many published literature). The new approach leads to a significant reduction of tuning parameters in the control design process, which is a major advantage. Detailed derivations of the modified approach are presented with respect to the generic aircraft dynamics model available in [16]. Extensive Six-DOF simulation studies show that, besides the above advantage, the new approach leads to two other additional advantages; namely reduced oscillatory response and reduced control magnitude. In a comparison study with an existing method using the Six-DOF model for Boeing 747 (with the numerical data available in [16]), numerical results clearly show the improved performance of this new approach. Furthermore, in lateral mode a technique for obtaining a corresponding roll rate command from the desired bank angle command is also implemented. Comparison results show improved performance of the new approach with this modification as well.
Piezoelectric Based Adaptive Wing for Flow Control
Authors: Sathyamoorthy S. , Raja S. , Joseph Stanley A.
Published: December 2023

An attempt is made to develop a piezoelectric based adaptive wing concept that can be used in Micro Air Vehicle (MAV) and Unmanned Air Vehicle (UAV) applications. Laminar boundary layer separation is considered to be a significant problem in low Reynolds number vehicles like MAV. Recently, periodic excitation has gained much interest in the control of flow separation through energizing the boundary layer. In the present study, a piezoelectric bimorph actuator has been used to develop a mechanism that will deflect or vibrate a segment of the wing to produce the required thickness variation and achieve flow control. A Finite Element model of the adaptive wing is developed in ANSYS and numerical results are compared with experiments. A five percent increase in the camber has resulted in 4.39 percent additional lift at higher angles of attack.
Off Design Performance Analysis of a Turbo Shaft Engine
Authors: Giridhar Kumar D. , Mustafa P.V. , Vijaya Kumar Reddy K.
Published: December 2023

The off-design performance of a gas turbine engine is strongly influenced by the characteristics of individual components. It involves the interplay of a large number of variables and would require a detailed computer code. In this paper, an effort is made to predict the influence of performance characteristics of individual components on the off-design performance of the engine. For this purpose, a computer code is developed with necessary iterations and convergence criteria. Parameters are estimated with respect to speeds ranging from 39500 rpm to 50500 rpm for a typical turbo-shaft engine with free power turbine. The effect of altitude on these parameters up to 6 km is also studied. Variation of specific heat and enthalpy with respect to temperature and fuel to air ratio is considered to estimate the performance calculations more accurately and to simulate a real engine behavior as close as possible.
An Improved Finite Element Model to Study Stress Concentration Around an Elliptical Cutout in Pressure Vessel: Validation : Part-I
Authors: Kumar R. Vijaya , Ramamurthy G. , Rao K.M. , Lakshminarayana H.V.
Published: December 2023

A finite element model to the analysis of thin shell structures with cutouts/inclusions is developed based on shear deformation theory. An eight-noded isoparametric shell element is considered with six degrees of freedom at each node. A convergence study is under taken to arrive at a suitable finite element mesh. The loading conditions include uniform tension, uniform pressure. The finite element results presented in this work are shown to be in good agreement with available analytical and experimental data and the direction for future work is also given.
Stress Separation in Digital Photoelasticity Part A - Photoelastic Data Unwrapping and Smoothing
Authors: M. Ramji  , K. Ramesh
Published: December 2023

The advent of digital photoelasticity saw the development of various techniques to get photoelastic data of isoclinics and isochromatics at every pixel in the domain. Unlike in other interferometric techniques, in photoelasticity one gets phase data of two quantities and their mutual dependence and interaction affect their evaluation. For stress separation studies, one requires both isochromatics and isoclinics accurately free of any kinks in the domain. With this in view, a robust approach is evolved to get these parameters. Initially wrapped isoclinics are obtained using a plane polariscope based phase shifting technique. These are unwrapped by a quality guided approach. However, the result has several kinks due to isochromatic-isoclinic interaction. An outlier smoothing algorithm is proposed for getting a smooth variation of the isoclinics. Six-step phase shifting method using a circular polariscope is used for determining the isochromatic data. The smoothed isoclinic values obtained are used in isochromatic calculation to get isochromatic phasemap free of ambiguities. This phasemap is also unwrapped by a quality guided approach and smoothed by the outlier algorithm. These methodologies are validated for two benchmark problems of a disk under diametral compression and a ring subjected to internal pressure. The models are subjected to moderate loads showing a high level of isochromatic-isoclinic interaction.
Experimental Studies on the Vibration Control of Epoxy Clay Nanocomposites
Authors: M. Ramesh Kumar  , J. Chandradass  , R. Velmurugan
Published: December 2023

Fabrication of nanocomposites for different-clay (alumino-silicate) concentrations (1, 3, 5 and 10 wt%) with the matrix (epoxy) is done by using shear mixer. This paper presents the experimental study of free vibration and damping characteristics. The work also involves vibration control of nanocomposite laminates by reinforcing organically modified montmorillonite clay in the epoxy matrix by resin casting technique. Theoretical study is also carried out to study the vibration and damping characteristics of epoxy clay nanocomposites. Dynamic result shows that the second phase nanoscale dispersion in the matrix significantly enhances the internal damping of nanocomposites. This work also presents the active vibration control of nanocomposite beams. Piezoelectric patches are bonded on the surface of beam and control algorithms are applied to the system. Feed forward (open loop) control algorithms are used to control the vibration. Maximum control is obtained for sample with 3 wt.%OC.
Quality Assisted Three Fringe Photoelasticity for Autonomous Evaluation of Total Fringe Order
Authors: K. Ashokan  , K. Ramesh
Published: December 2023

Three fringe photoelasticity (TFP) is a technique for determining the total fringe order from a single colour isochromatic fringe field. In TFP, the total fringe order is obtained by comparing the colour of the unknown photoelastic fringe pattern with a calibration specimen. Comparison is conventionally done by minimising the colour difference error. This leads to incorrect evaluation of fringe order in some regions showing itself as noise when these values are plotted as an image. In this paper, a new autonomous quality based approach is developed to identify and remove this noise. The method is explained by evaluating the total fringe order for the problem of a disc under diametral compression. The application of this methodology is demonstrated by solving two other example problems.
Experimental Investigation of Flexural Behavior of Sandwich Beams With a Puf Core and Embedded Rigid Inserts
Authors: Ramesh S. Sharma  , V.P. Raghupathy
Published: December 2023

This investigation is concerned with the experimental investigation of strength and stiffness of sandwich panels with rigid inclusions (inserts) embedded in a PUF core. Four point and Three point flexural tests were conducted on number of sandwich specimens fabricated by woven glass cloth FRP as facings, polyurethane foam as core with epoxy resin as bonding medium between core and the facings. The strength and stiffness estimated in this investigation with rigid inserts revealed that the use of inserts improves the stiffness and load bearing capacity of the panels. Inserts that are connected to the face sheets and extended through the depth of the core were considered. This investigation has confirmed the importance of experiments in the field of sandwich constructions with rigid inclusions which can effectively replace other conventional sandwich constructions which are currently in use.
Cfd Analysis in Coaxial Injector of a Cryogenic Rocket Engine And Evaluation of Atomisation Characteristics Using Simulant Fluids
Authors: S. Sujith  , S. Sujith  , N.V. Mahalakshmi
Published: December 2023

A Study of atomisation and mixing of 2-phase propellants using simulant fluids injected from a coaxial injector of an operating cryogenic rocket engine is carried out and presented along with the CFD analysis of flow within it. The original injector jet (Jet 3) designed, modeled and analysed has swirl for LOX (water) alone with GH2 (air) having no swirl. Injector jet having inner casing and outer sleeve is modeled using I-DEAS software and analysed for inner core fluid domain (liquid) and annular fluid (air) domain. Results of flow analysis inside jet revealed asymmetric nature of air flow at exit due to the air fluid domain itself is not axisymmetry in the original jet. This non-axisymmetry of 2-phase fluids at the exit of injector jet will obviously affect the characteristics of atomisation and mixing of fluids. Data obtained from atomization experiments done on this jet using stimulant fluids (water in LOX side and air in GH2 side) such as particle distribution and Sauter Mean Diameter (SMD), fairly matches with the predictions made using CFX software and associated codes which enabled to evaluate the analysis software. Further, the air flow at exit has been made axisymmetric by modifying the air passage in the injector jet (Jet 3 Mod) and the effect of this modification on atomisation and mixing of 2-phase fluids is predicted using the CFX software. In combustion better efficiency with less instability is to be attained. For meeting both simultaneously articles size distribution after injection has to be neither very finer nor coarse. Comparison of predicted data on atomisation revealed that the modified Jet (Jet 3 Mod) is relatively better to give stable combustion with higher performance.
Identification of Aeroelastic Quasi-Steady Effects Through Flex Factor
Authors: Jatinder Singh  , Basappa  , Rohit Kumar
Published: December 2023

Rigid body modeling for estimation of aerodynamic derivatives from the flight responses of a flexible aircraft does not yield the true stability and control parameters of the aircraft, as the estimated derivatives absorb the aeroelastic effects present in the data. The analytical expressions for computing the rigid body derivatives from the flight-estimated values require knowledge of aircraft modal mass and generalized elastic deflections which is not always available. This paper considers a simplified approach based on quasi-steady representation of aeroelastic effects to identify the rigid body parameters from the flexible aircraft responses. Results show that, by combining data at several flight conditions, system identification method can be applied to separate the rigid body derivatives and the dynamic pressure dependent quasi-steady effects caused by structural deformation.
Vibration Analysis of Thin Circular Disc Interacting With A Fluid in Cylindrical Container
Authors: S.K. Mangal  , Ajay Kumar Sood
Published: December 2023

In this paper, vibration analysis of a thin circular disc interacting with a fluid in cylindrical container is carried out. It has been done systematically by carrying our mathematical modeling and subsequently validated by ANSYS software. The author has first determined natural frequencies and mode shapes for a thin circular disc alone and then for fluid contained by a cylindrical vessel alone. The author had then found natural frequencies and mode shapes for coupled case of thin circular disc interacting with a fluid contained by the cylindrical container. The same had been validated by ANSYS software. It is found that natural frequencies of coupled vibrations are different than that of the frequency of disc or fluid taken separately. In order to study the correct failure pattern of the coupled vibration system, it, thus, becomes a necessity to study coupled vibration analysis
Near Real Time Estimation of Nonlinear Aerodynamics
Authors: C. Kamali  , A.A. Pashilkar
Published: December 2023

This paper describes a novel technique for near real time estimation of non-linear aerodynamic coefficient dependencies on one or more independent variables. It is important from the point of view of updating the aerodynamic database of six DOF simulations subsequent to flight test. The technique is validated using the six DOF simulated data. The novelty about this technique is the combined utilization of linear interpolation and recursive least squares estimation to capture nonlinear functional dependencies that makes it suitable for multidimensional near real time estimation. The technique is preceded by data compatibility check using Extended Kalman filter.
Novel Method for Coarse Alignment of Strapdown Ins On Oscillatory Base
Authors: Verma Vidya Sagar , Sitara Brajnish , Ramesh Kumar B. , Chandrasekhar R.S. , Satheesh Reddy G.
Published: December 2023

Novel Analytic Coarse Alignment Method is presented for Strapdown Inertial Navigation Systems (SDINS) alignment on oscillatory base. Oscillatory base alignment is conducted by building two vectors derived from gravity and angular velocity information provided by the strapdown INS under oscillatory motion and comparing them with similar vectors built using the local level reference frame information. The theory and algorithms are detailed in the paper and several simulation test results are compiled for various kinds of oscillatory motion.The proposed algorithm could be used for sea based INS applications.
Trends in Aeronautical Flight Test Telemetry
Authors: Mayer Gerhard , Chalfant Timothy
Published: December 2023

Based on Action Item 1.5 and the relevant investigations and studies, the World Radio communication Conference (WRC 2007) decided upon new additional frequency spectrum allocations for Aeronautical Mobile Telemetry (AMT).

Four new frequency bands in the range from 4400 to 6700 MHz have been allocated to the Aeronautical Mobile Service (AMS) on a co-primary basis, limited to AMT for flight testing by aircraft stations. The range from 5091 to 5150 MHz may be used worldwide, allowing the implication of wide band telemetry links and helping the international cooperation and standardization in flight test missions.

After reviewing the resolutions COM 4/2 and COM 4/7 of the WRC 2007 it is realized that C-Band becomes an attractive band for AMT. Components and systems for either new state-of-the-art equipment or for the upgrade of existing systems (in L-or S-Band) are already in work. One area of concern requiring an up front evaluation is tracking algorithms and mechanical tracking systems that operate specifically in C-Band. Future planning to greater utilize this band is presented.
The Terprom® Digital Terrain System (DTS)
Authors: Cowie M. , Wilkinson N.
Published: December 2023

Developed specifically for tactical military aircraft operations, TERPROM® is the world leading Digital Terrain System, offering a range of capabilities that can provide both safety and tactical benefits to the aircraft. The system is an established and well-proven product that has been in production since 1991. To date it has been selected by fourteen Nations worldwide for use on numerous platforms. The number of military aircraft equipped with TERPROM® is now over 5000 and growing.
TERPROM® provides the following functions: Terrain Referenced Navigation (TRN), Predictive Ground Collision Avoidance System (PGCAS), Advanced Terrain Avoidance Cueing (ATAC), Obstruction and Wires Warning and Cueing (OWWC), Database Terrain Following (DBTF), Air to Ground Ranging Functions, Terrain Awareness Display (TAD). At the core of the system is the Terrain Referenced Navigation (TRN) capability which navigates by combining aircraft navigation data (e.g. inertial and, or GPS) and radar altimeter measurements of height above ground level (AGI), with terrain heights alms from the stored map data, to produce a navigation solution referenced to the terrain map data. This navigation solution then allows the other TERPROM® functions to use the map data to provide their safety and tactical capabilities. Three variants of TERPROM® have been developed to satisfy the airborne platform market: - Fast Jet, Military Transport, Helicopter.  TERPROM® is a living product that has and continues to receive significant internal investment to increase its capability, functionality and performance to support future opportunities. Current areas of development include: Use of higher resolution map data which will increase the performance of TERPROM® and offer enhanced capability to platforms flying nap of the earth, enhanced capability in urban areas and could also reduce any platform reliance on GPS. Integration with active forward looking sensors to provide additional information to the Navigation, Situational Awareness and Ranging functions and also to provide new capabilities such as real time mapping of unmapped terrain features and obstructions.
Muffler Systems for Aircraft Noise Reduction
Authors: M.G. Prasad  , B. Rajavel
Published: December 2023

Noise reduction is considered to be one of the major challenges in aircraft industry, since beginning of bi-plane era to recent advanced fast jet aircraft era. In general, aircraft noise can be classified into two categories i.e. aircraft interior (cabin noise) and exterior noise. Some of the typical structure borne and air borne noise sources for both interior and exterior noise are engine, cabin conditioning system, fuselage, landing gear, canopy and wings etc. Over the years, the structure borne noise has been effectively reduced by means of active and passive control of aircraft structures. The airborne noise source is aerodynamic in nature and has broad band frequency content. This can be effectively reduced by preventing the formation of turbulence or wake. For the past few decades mufflers have been used in aircraft industry to reduce the noise generated by propulsion system and cabin conditioning system. This paper gives an overview of noise in aircraft, the application of mufflers used in the general aircraft industry and also how effectively the muffler systems can be designed by taking into account the source and termination conditions.
State of Art Enhanced Fatigue Meter Adaptable across Aircrafts
Authors: Jayanthi J. , Nanda Manju , Dhage Shamsundar , Arjun T.S.
Published: December 2023

This paper discusses the novel design and development of the state of art fatigue meter for the fighter aircrafts. The unique features of the enhanced fatigue meter (eFM) are its capability to be configured for critical parameters, adaptable across different aircrafts and flexible for using internal or external accelerometer. The combat aircrafts carry out a lot of maneuvers while flying. While doing so, these aircrafts experience large range of variations in the accelerations due to gravity i.e. G-variations. This sudden and large change in acceleration due to gravity, as a function of time forms the fatigue loading on the airframe. This fluctuating loading causes fatigue damage to be accumulated in the aircraft structure. Over a period of time, the accumulated fatigue damage leads to development of crack and breakdown of the structure. In order to monitor and keep track of the g-loads experienced by the aircraft and to predict the remaining service life of the aircraft, a system that measures the g-loads encountered by the aircraft every time it flies is essential. The relevant g-load spectrum of the aircraft can be derived from these recorded data.
Effects of Firm Size and Capital Structure on Firm Value (Empirical Study of Telecommunication Companies Listed on the Indonesia Stock Exchange for 2018-2021)
Authors: Mahirah Annisaa , Uzliawati Lia , Soleha Nurhayati
Published: December 2023

Purpose - The purpose of this study is to determine the effect of firm size and capital structure on firm value using data from telecommunication companies listed on the Indonesia Stock Exchange in 2018-2021.

Design/methodology/approach - The method used is quantitative research with secondary data from 16 companies. The sample was taken using the purposive sampling method. This study used a multiple linear regression.

Finding - According to the research findings, (1) firm size has a significant positive impact and (2) capital structure does not. In this research model, the value of determination (R squared) is 0.110 or 11%. The calculated F value is 3.202 > 3.175 and the sig F value is 0.049 < 0.05.

Originality -