bluuebunny/crossref_metadata_2025 huggingface dataset:
Elastic Response of Lifting Type Reentry Vehicles under Closed Loop Control
Authors: Joshi Ashok , Mujumdar Prasanna M , Chari G. R. R.
Published: December 2023

Present paper discusses the modeling, dynamics and closed loop aeroservoelastic analysis of a typical lifting type reentry vehicle. A linear aeroservoelastic formulation for a lifting type reentry vehicle is presented, which is based on the reduced order modeling approach, using the principle of superposition. The aeroservoelastic problem is formulated in the time domain by converting frequency domain unsteady aerodynamic loads, using pure lag-pole based rational function approximation. Second order actuator and third order sensor models are included in the closed loop control architecture, that uses full state feedback pole placement technique (for level-1 flying qualities) to arrive at control gains. The study brings out the effect of closed loop command on the elastic response of a typical lifting type reentry vehicle.
Response Studies of a Tethered Aerostat Balloon Subjected to Initial Disturbances
Authors: Kumar Ajit , Ghosh A.K. , Sati S.C.
Published: December 2023

This paper presents response studies for a tethered aerostat balloon subjected to initial disturbances. The linearized small perturbations equations of motion have been decoupled into longitudinal and lateral-directional movements. First of all, trim conditions are estimated for a typical operating wind speed and then equations of motion are converted to state-space form. Eigenvalues and eigenvectors are then evaluated for the characteristic matrix. The differential equations are then solved using eigenvalues and eigenvectors approach. The initial disturbances are then applied first in isolation and then in combination. The results are presented for a reference aerostat balloon in the form of plots of responses of longitudinal and lateral motion variables with time. The plots reveal useful information which may be used for finalization of operating parameters for aerostat balloon to generate required response characteristics.
Thermal Postbuckling of Heated Uniform Columns Considering Green Nonlinearity: A Novel Liner Finite Element Formulation
Authors: Venkateswara Rao G. , Kartikeyan T.V. , Durga Rao K. , Manzoor Hussain M.
Published: December 2023

Thermal postbuckling behavior of uniform, heated columns is presented, by using a novel linear Finite Element (FE) formulation. In this investigation, the general Green axial nonlinear strain- displacement relation is used, instead of the popularly used simpler von-Karman nonlinearity, which is a subset of Green nonlinearity. In the earlier complex nonlinear FE formulations, time consuming iterative or step-by-step methods are used to obtain the solution for thermal postbuckling. In the novel FE formulation, normally used FES , for performing linear buckling analysis, is proposed to obtain thermal postbuckling loads. The nodal degrees of freedom are deflection and its first derivative with respect to the axial coordinate. The geometric nonlinearity is incorporated through the tensile loads induced, with axially restrained ends of the column, due to large deflections. The effectiveness of the novel FE formulation is demonstrated, from the numerical results obtained, in terms of the ratio of thermal postbuckling to buckling loads, for specified reference deflection and slenderness ratios, of the columns with different boundary conditions. The numerical results reveal some interesting phenomena of thermal postbuckling behavior of columns.
Mid Frequency Structure-Borne Noise Modeling in a Trimmed Automotive Vehicle
Authors: Prasanth S. , Nanjundaradhya N.V. , Sharma Ramesh S
Published: December 2023

Finite Element Method (FEM) and the Statistical Energy Analysis (SEA) are standard methods in the automotive industry for the prediction of vibrational and acoustical response of vehicles. The FE method, based on a deterministic description of the dynamics is typically used for structure-borne and air-borne problems and is usually limited to below 250 Hz. The method becomes prohibitively expensive in terms of computational costs with increasing frequency as more Degrees-of-Freedom (DOF) are required to correctly represent the dynamic response of the structure. Additionally, the dynamic response becomes sensitive to small perturbations in the model, thus defeating the purpose of a deterministic modeling method. SEA is a statistical method widely applied in automotive industry for air-borne problems at frequencies higher than 300 Hz. The method is highly efficient for the design and optimization of sound packages facing airborne sources, but it lacks accuracy when dealing with structure-borne sources in the mid frequency range. However, both methods are not capable of handling the so called "mid frequency problem", where both short and long wavelength components are present in the same system. A Hybrid method has been recently proposed that rigorously couples SEA and FEM. In this work, the HybridFE-SEA method has been used to create fast/efficient model of structure-borne noise in a fully trimmed vehicle from 200Hz to 1 kHz. This paper first describes simple guidelines used to partition the vehicle into stiff components described with FE and modally dense components described with SEA. It is also demonstrated how detailed local FE models can be used to improve SEA descriptions of car panels and couplings. After review of the Hybrid FE-SEA models of a full vehicle that were built, sample experimental validation results of interior Sound Pressure Levels and panel vibration are shown for both bare and fully trimmed vehicle configurations.
Effect of Inlet Vane Angle of a Partial Vane Diffuser on the Performance and Flow Filed of a Centrifugal Compressor
Authors: Anish S. , Sitaram N.
Published: December 2023

The paper presents experimental results on the effect of inlet vane angle on the performance and flow field of Partial Vane Diffuser (PVD) of a low speed centrifugal compressor. Performance tests are conducted for eight configurations of PVDs. From these tests, an optimum configuration with 5° increase in inlet angle of partial diffuser vanes on shroud (PVDHS5) is selected for further measurements i.e. static pressure on the diffuser hub and shroud and diffuser passage flow field at four flow coefficients. From passage flow measurements flow parameters are obtained within the diffuser flow passage. Flow parameters are axially averaged and their contours are presented. Radial variation of these flow parameters is also presented. PVDHS5 gives 2.3% increase in peak energy coefficient and 4.9% increase in efficiency compared to that of vane less diffuser. The flow at the exit of PVDHS5 is more uniform.
A Note on Single Impulse Approach for Trajectory Correction
Authors: Sarsar R.B. , Naik S.D. , Arlulkar P.V.
Published: December 2023

Trajectory correction in the terminal phase of artillery projectile is studied using single impulse. The point of implementation of impulse on the trajectory and magnitude of impulse is obtained for desired correction. The flight path angle at point of implementation of impulse for given target position is evaluated and analysed by two point boundary value problem.
Human Factors, Analysis Tools and Methods for Development of Reliable Aircraft Design
Authors: Hebbar Archana , Pashilkar Abhay A
Published: December 2023

This paper provides an overview of different tools and methods that are capable of addressing human factors issues during an aircraft design programme. The huge amount of literature available is classified into a comprehensive birds eye view of the field. This is described in the form of taxonomy. Methods to determine the root cause of an airline incident/accident are discussed with application of Human Factors Analysis Classification System framework to few commercial airline accidents. Tools for identifying probability of human error in a task scenario are examined and a promising method for human error prediction is illustrated for a typical landing scenario. Also, different workload assessment methodologies are described in brief along with their strengths and limitations. Finally, a novel aircraft/component design methodology is proposed with human performance modelling tools that shall reduce the design life cycle and the inherent cost involved. In a nutshell, this paper basically discusses on how to design an aircraft that can reduce the incidents attributable to human factors.
Indian Interplanetary Missions - A Technology Perspective
Authors: Kiran Kumar A.S.
Published: December 2023

The successful insertion of the Indian Mars Orbiter Mission in September 2014 in its maiden attempt along with the preceding Chandrayaan-1 mission has provided a huge boost to the global perception of Indias technological prowess. This technological achievement is built upon the decades of ISRO’s experience in mission design, launch and operation of earth observation and communication spacecraft. The main driving factors for the Indian efforts in the direction of lunar and interplanetary missions were the optimal utilization of an existing launch system (PSLV) to achieve minimum energy orbit placement around the Moon and Mars with an innovative, highly elliptic orbit. An exposition of the mission planning, payload design, strategy and the technological features along with the differences with respect to the earth-or-biting missions is presented.
Experimental and Numerical Study of Pulse Detonation Engine with Ethylene as a Fuel
Authors: Srihari P. , Mallesh M. A. , Sai Krishna Prasad G. , Charyulu B.V.N. , Ezhil Shakti M. , Reddy D. N.
Published: December 2023

This paper presents an insight on the study of transient, compressible, intermittent pulsed detonation engine with one-step overall reaction model to reduce the computational complexity in detonation simulations. Investigations are done on flow field conditions developing inside the tube with the usage of irreversible one-step chemical reactions for detonations. In the present simulations one and two-dimensional axisymmetric tubes are considered for the investigation. Studies are also performed with different grid sizes which influence the prediction of Von-Neumann spike, CJ Pressure and detonation velocity. Numerical studies are conducted using 66mm diameter tube and compared with the literature values. The simulation result from the single-step reaction model agrees well with the previous published literature of multi-step reaction models. The present studies shows that one-step overall reaction model is sufficient to predict the flow properties with reasonable accuracy. Experiments are conducted in a 25mm dia. tube with Ethylene/Air mixtures. The reactants are premixed and injected into the detonation tube using solenoid valves. The equivalence ratio of the fuel/oxidizer mixture and the length of the detonation tube are varied to understand their effects on detonation parameters. Finally the results from the present numerical study are compared and validated using NASA CEA and experiments.
A Numerical Unsteady Analysis of a Plunging Wing
Authors: Vasanth Kumar G. , Mukherjee Rinku
Published: December 2023

Numerical simulation of unsteady motion of wing through undisturbed fluid is formulated using Unsteady Vortex Lattice Method. A free-wake algorithm is developed using a fourth order Adam-Bashforth technique. Rankine vortex model is used to avoid numerical singularities and wake decay algorithm is used to model the viscous dissipation of the shed wake. The resulting MN x MN equations are solved for unknown Γwing using LU decomposition, where M and N are number of divisions of the wing along chord and span respectively. The aerodynamic coefficient of lift, CL, induced drag, CDi , distribution of circulation, Γ and wake geometry are calculated for unsteady plunging motion. Effect of cross-flow is studied. The results are found to be in good agreement with available literature.
Ground Vibration Test Based Flutter Prediction for a Combat Aircraft
Authors: Shanthini G. , Pankaj A.C. , Manjuprasad M. , Dhandabani V. , Hemalatha E. , Vaidyanathan R.V.
Published: December 2023

This paper compares the flutter characteristics of a combat aircraft predicted using experimental modal parameters from ground vibration tests with the results obtained by flight flutter tests. An equivalent finite element model representing the test points in ground vibration tests has been developed and further refined to obtain a finite element model with fine mesh encompassing the entire lifting surface areas. Infinite plate interpolation scheme has been used to extrapolate the eigenvectors for the refined model. A Direct Matrix Abstraction Program (DMAP) written in NASTRAN replaces the generated mass normalized eigenvalues and vectors of the refined model from a dynamic analysis in NASTRAN, with the experimentally obtained eigenvalues and extrapolated eigenvectors. Flutter analysis has been carried out with the replaced experimental modal parameters in subsonic, transonic and supersonic regimes using flutter modules in NASTRAN and ZAERO software. The results obtained using this procedure have been compared with the flight flutter test results. The dispersion in the damping and frequency results obtained from computations and the flight flutter tests were within acceptable limits showing a good correlation.
Numerical Exploration of Low Altitude Rocket Plume in Aircraft Vicinity
Authors: Dharavath Malsur , Manna P. , Chakraborty Debasis
Published: December 2023

Low altitude plume of a solid rocket motor is numerically explored. The effects of free stream Mach number, altitude and presence of launch platform wing on plume shape are studied. Three-dimensional Reynolds Averaged Navier-Stokes (RANS) equations along with k-ε turbulence model and species transport equations are solved using commercial CFD software CFX-11. Thermochemical parameters (Mach number, pressure, temperature and propellant hot gas mass fraction) are analysed to characterize the plume. Mixing layer boundaries, its thickness and the attainment of self-similarity are evaluated to study the plume structure. With the increase of free stream Mach number, the computed plume diameter reduces. Centerline pressure, temperature and radial expansion of the plumes increases with the increase in altitude. Plume is found to be elongated and narrowed with relatively warm core region due to the presence of platform wing.
Studies on Performance Deterioration of a Low Bypass Turbofan Engine in Service
Authors: Mishra R. K. , Prakash L. , Srinivasan K. , Saravanan M.
Published: December 2023

The performance deterioration of a low bypass turbofan engine is analyzed to find out its causes. The performance parameters are compared with their limitations for a specific throttle setting. Dirt buildup, soot deposit, de-twisting of turbine blades, malfunction of atomizers and fuel system accessories are found to degrade the engine health and performance before the intended service period. Periodic compressor wash and engine maintenance, cleaning or replacement of fuel filters and good assembly practices are found beneficial in addressing the issues and retaining the engine performance.
Conjugate Heat Transfer Analysis of Scramjet Combustor
Authors: Bhandarkar Anand , Dharavath Malsur , Manna P. , Chakraborty Debasis
Published: December 2023

Conjugate Heat Transfer (CHT) simulation with reacting flow in scramjet combustor is performed. Three dimensional RANS equations with k-ω turbulence model, EDM combustion model for fluid domain and energy equation in the solid domain are solved simultaneously using commercial CFD software. The SCHOLAR scramjet combustor experiment is taken as a test case of validation. The computed flow properties match reasonably well with experimental data and other numerical simulations. Near fuel injection locations, computed surface temperatures over predict experimental data due to use of fast chemistry for combustion modeling. In the downstream, at the diverging section of the combustor, computations under predict the surface temperature. Use of natural convection boundary condition is found to have marginal effect in the surface temperature history of the scramjet combustor. Temperature dependent material properties are found to have significant effect in the distribution of temperature across the combustor wall.
Wing Aerodynamic Optimization in the Presence of Interacting Canard at Subsonic and Supersonic Speeds
Authors: Gupta S.C.
Published: December 2023

Effort is made to minimize the drag subject to lift constraint. The wing and canard interacting planform is considered to study the effect of canard presence towards optimization of wing. The aerodynamic efficiency of optimized wing is worked out for off-design values of angles of attack and compared with the wing alone case. Subsonic and supersonic flow conditions are handled through panel methods. Results are presented for wing alone and canard-wing combination for subsonic and supersonic flows. Substantial drag reduction is seen possible for subsonic Mach numbers. The off-design aerodynamic efficiency of canard-wing combination is seen to be superior as compared to wing alone case. The program is executed on a 2.4 GHz laptop using gfortran compiler that is built in the fedora operating system. Fedora12 double precision 64 bit is used for this work. Alternatively, Ubuntu operating system can also be utilized. Fedora and Ubuntu both are Linux based.
Numerical Study of Supersonic Flow Past a Cylindrical Afterbody
Authors: Das Pratik , De Ashoke
Published: December 2023

The near wake of a cylindrical afterbody aligned with a uniform Mach 2.46 flow has been numerically investigated using Reynolds-Averaged Navier-Stokes equations (k-epsilon two equation model) and Large Eddy Simulation (dynamic sub-grid scale eddy viscosity model). Mean flow field properties obtained from numerical simulations, such as axial velocity, pressure on the base surface has been compared with the experimental results. It has been found that k-epsilon model fails to predict the flow properties in the recirculation region where better agreement has been observed between the data obtained from LES and measurements. Data obtained from LES has been further analyzed to investigate the turbulent flow field in the wake region. Parameters like turbulent kinetic energy and primary Reynolds stress have been calculated and compared with the results obtained from an experiment in order to achieve a better understanding of the role of turbulence in the flow field.
Experimental Investigation of Aerospace Grade Composites Porosity Laminates Under Hygro-Thermal Environment Condition
Authors: Ramesh Kumar M. , Karuppannan D. , Sundaram Ramesh , Ghosh Anup
Published: December 2023

The effect of porosity has been studied by developing different levels of porosity laminates through a new autoclave based manufacturing technique known as Diverse Cure System (DCS). Further assessment of porosity levels by mechanical characterization (Inter-laminar Shear Strength), microscopic studies and acid digestion method have been achieved in Carbon Fiber Epoxy laminates. Correlations are obtained on the different levels for porosity laminates of two different thicknesses. ILSS test results are compared with the literature results. Assessment of porosity effect on ILSS is performed at room temperature and environmentally conditioned specimens. Strength degradation of 20 to 30% has been noticed on porosity laminates. Hygro-thermal specimens are tested at room temperature, elevated temperature and hot wet condition. A large reduction in the range of 45 to 53% in ILSS has been noticed on the moisture conditioned specimens tested at elevated temperature of 150°C.
Effect of Adjacent Blade Oscillation on the Forces on A Blade of a Compressor Cascade
Authors: Keerthi M. C. , Kushari Abhijit
Published: December 2023

The current trend of aircraft engines is one towards attaining high isentropic efficiency while minimizing its weight. This leads to a state where the blades are highly loaded and consequently susceptible to vibrations. High cycle fatigue caused as a result of such self-excited flutter or forced vibration due to defects in the air stream are detrimental to the engine. An understanding of the onset of instabilities is essential to predict their occurrences to avoid a catastrophic failure during operation or costly redesign during the development phase. The critical parameters in turbomachine aeroelasticity are the reduced frequency and the interblade phase angle. The damping of the system is known to be a function of the phase difference between the blade forces and the blade motion. In the present study, a linear cascade of five blades is considered to understand the effect of harmonically varying boundary conditions. The second and fourth blades of the cascade are subjected to torsional oscillation by an external mechanism. The third blade, considered as the reference, is stationary and instrumented. The unsteady pressure along the reference blade surface is measured simultaneously with the loads acting on the blade. The unsteady pressures are measured using a multi-sensor pressure scanner by multiplexing and the loads are measured using a five-channel strain gage balance. The blade displacement is determined from the integrated accelerometer signal mounted on an oscillating blade. The experiments are conducted at a low-subsonic speed and multiple oscillation frequencies. The cascade is set at zero incidence and four stagger angles. The effect of inter-blade phase angle is included as the oscillation of the walls adjacent to the reference blade. The phase difference between the harmonic motion of the neighboring walls and the pressure and load signals on the reference blade is related to the damping characteristics of the reference blade. The variation in damping is studied for the range of blade motion phase difference angles and reduced frequencies. The effect of the phase difference between the oscillating blades is seen to strongly affect the damping characteristics of the reference airfoil.
Investigation of Fin Buffet Characteristics of a Developmental Combat Aircraft Through Wind Tunnel Experiments
Authors: Kumaraswamy A. , Vaidyanathan R. V. , Kamesh J. V. , Hemalatha E.
Published: December 2023

Airframe buffet is an important dynamic problem associated with combat aircraft flight, especially in the high Angle-of-Attack (AoA) regime. Occurrence of buffet due to flow separation at high angles of attack needs to be structurally cleared and a buffet boundary needs to be established. The methodology adopted to clear the aircraft from buffet during high AoA flight testing of a developmental light combat aircraft is focused in this article. Experimental unsteady pressure data from low speed wind tunnel tests conducted on a scaled down (1:10) model and airframe especially fin vibration data measured from flight tests formed the basis for this methodology. The reference spectrum has been formulated through unsteady pressures measured using pressure transducers mounted on the fin of the wind tunnel model. This spectrum (scaled up to 1:1) i.e. pressure Power Spectral Density (PSD) excitation was used as an input to the FE model of aircraft fin mounted on the rear fuselage. Buffeting response predicted in terms of acceleration PSD on the fin and rudder have been compared with the flight measured acceleration PSD data to validate the numerical model. The validated model is used to predict loads to clear the aircraft for further flight envelope expansion at high AoA.
Flash Memory Technology for Space Application - An Approach
Authors: Varna Prabhakara , Yellampalli Siva
Published: December 2023

Recently, flash memory technology has been considered for space application. This paper provides an approach for induction of the flash memory based mass data storage system to space program. It also, provides the studies and experiments that have been carried out in recent past to understand and characterize the behavior of flash memory in space environment. Further, it provides the design aspects which need to be addressed when dealing with flash memory for space environment, as identified by domain experts
Determination of Whole Field Strain in Composite Reflector Using Photogrammetry
Authors: Prabhakar Vivek , Renji K. , Behara Raghunatha
Published: December 2023

Conventional strain measurement techniques cannot be used to obtain the strains in composite reflectors under thermal environment. Though photogrammetry can be used to measure the deformations it cannot provide information on strains. In this work a methodology is developed to determine the strains from the displacements obtained from photogrammetry coordinate measurement. The strains are determined by applying equilibrium conditions and not from the gradient of the displacements. The results are verified using simulated data as well as experiment. It is demonstrated for a composite reflector of a typical spacecraft when subjected to thermal load. The methodology developed in this work helps in obtaining the strain distribution without using expensive digital image correlation equipment. This methodology can be used on wide variety of applications like inflatable structures, flexible structures etc., where strain gauge measurements are not possible to be carried out.
Full Scale Bend Test of a Multi Stage Aerospace Vehicle
Authors: Gopikrishna R. , Karthiek K. , Varadanam M. , Venkateswara Rao B. , Anjaneyulu P. S. R.
Published: December 2023

Evaluation of structural integrity of a missile involves sectional and full scale tests. Tests are carried out for transportation, articulation and aerodynamic loads. Uniqueness of carrying full scale bend test of a multi stage aerospace vehicle lies in the qualification of not only structural integrity of different sections but also the joints. Empty missile structure forms the testing frame. A bending moment envelope is simulated using a combination of upward and downward loads. Design and realization of open configuration test rig frames in order to simulate the necessary boundary conditions was executed. The output measurements for the test are strains, deflections and joint rotation constants. Linear Variable Displacement Transducers (LVDTs) measures the deflections normal to the missile axis and help in mapping of the deflection pattern along the length of the missile. CODs (Crack Opening Devices), developed in-house, are used to measure the joint openings during the bend test. The measured Joint Rotation Constants (JRCs) are in-turn used as input to refine the Finite Element (FE) model, thereby improvising the accuracy of the predicted results from the FE model.
Flow Field Simulation Tool of Solid Propulsion Control Systems for Missile Applications
Authors: Sudhakara Reddy A.V. , Padhi R. , Karunanidhi S. , Reddy D.N.
Published: December 2023

In order to achieve hit-to-kill miss distances against manoeuvrable ballistic missile targets, future generation missiles calls for fast response non-conventional propulsion control systems during terminal homing period in high-endo to exo-atmosphere regions augmenting aero control. Based on advances in thrust modulation controlling throat area in solid propulsion pintle motor, control systems are developed for missile Divert and Attitude Control Systems (DACS) applications using multiple nozzles in pitch/yaw directions connected to common gas generator. Control thrust vector for lateral and attitude corrections is generated with proportional distribution of total thrust in pitch/yaw directions through real time thrust modulation of pintle nozzles

Towards development of propulsion control systems based on solid propulsion, prototype systems: Thrust Controlled Motor (TCM) and Divert Thruster Flight Propulsion Control System (DTFPCS) are developed to demonstrate thrust modulation/ control thrust vector generation in solid propulsion and finalize unified controller for various missile control applications. Design & development process of prototype systems calls for flow field simulation tool for parametric design analysis/optimization and generate performance maps/control parameters based on detailed flow distributions. Present paper presents flow field simulation tools with Steady Flow Field (SFF) model and Dynamic Flow Field (DFF) model integrating dynamics of pintle movement with steady flow solver. Parametric analysis of geometrical profiles of pintle/throat regions and effect of pintle speed on system response are presented for system design optimization. Performance maps and controller maps of prototype systems are generated based on flow field distributions for nozzle thrust modulation. Simulated results are compared with open loop hot tests and unified controller parameters are updated for control thrust vector generation. Finally flow field distributions of DTFPCS operating modes: neutral-thrust and lateral-thrust are presented demonstrating the utility of simulation tool in design analysis and system development. Present simulation tool is critical in system design optimization and unified controller development for various flight control applications with minimum number of developmental tests. Further work of integrating propellant grain geometry variation during motor hot tests, with flow field model is in progress to predict control system performance for various missile control applications.
Continuous Descent Approaches Against Modified Timing Requirements : A Design Study
Authors: Blesson John , Subba Reddy B.
Published: December 2023

In order to meet the challenges of growing air traffic, many research activities have been initiated to come up with more efficient and safe flight operations including Trajectory Based Operations. One of the initiatives has been to control Time-of-Arrival during enroute descend phase of flight. The design studies presented in this paper investigate possibility of making minor adjustments using thrust control at near idle position to avoid final altitude errors. Nominal altitude time trajectories coupled with its boundaries using thrust control are adopted for the purpose. To synchronize with ground based Decision support Tools, message set requirements for Aircraft Intent, as proposed by Boeing, have been addressed. Simulation results on the flight path trajectories and typical case studies for changing the time of arrival are presented to validate the approach. Possible areas for further studies are highlighted.
Supersonic Flow Separation in Front of a Forward-Facing Step
Authors: Murugan Jayaprakash N. , Govardhan Raghuraman N.
Published: December 2023

A detailed experimental study has been done to understand the Shock Wave-Boundary Layer Interaction (SWBLI) over a Forward-Facing Step (FFS) of height (h) in a Mach 2.5 flow using Particle Image Velocimetry (PIV). In addition to PIV, unsteady wall pressure measurements, high-speed schlieren and surface oil flow visualization have been studied. Flow separation using surface oil flow visualization was observed around 4.1 step heights upstream of the step face. Shock motions extracted from the schlieren image sequence shows a peak frequency of approximately 1000 Hz, which corresponds to the dominant (low) frequency at which the shock oscillates; this being two orders in magnitude smaller than the characteristics frequency of the incoming boundary layer. Also, spectra of the unsteady wall pressure data shows that the shock oscillates with a peak frequency of approximately 1000 Hz. The effect of shock location (xs) from instantaneous velocity PIV fields in the cross-stream plane due to an upstream influence parameter (line-averaged boundary layer streamwise velocity, ul) and a downstream parameter (separation bubble or recirculation region area, A) is studied. Instantaneous cross-stream PIV measurements show significant variations of the separation shock location, incoming boundary layer velocity fluctuations and recirculation region. Besides, conditionally averaged velocity field based on incoming boundary layer streamwise velocity fluctuations and separation bubble area in the cross-stream plane shows that the shock location (xs) is correlated to the size of the separation bubble and not to boundary layer velocity fluctuations.
Isoparametric Finite Element Method to Generate Structured Grid for Numerical Flow Simulation
Authors: Mehta R. C.
Published: December 2023

Eight-nodded quadrilateral finite element is used to generate structured grid for a numerical simulation. The computational domain is sub-divided into number of quadrilateral regions that display the geometry of each sub-domain. The inner and the outer boundaries of the computational domain are described in terms of the surface coordinates. An algebraic homotopy procedure is used to generate grid clustering in order to resolve boundary layer. The structured grid is linked with the flow solver based on finite volume of space discretiztion scheme with multi-stage Runge-Kutta time stepping technique. Examples are illustrated to demonstrate the grid generation procedure and data processing for a forward facing aero-disc spike attached to a hemispherical blunt body at Mach 6 and over a heat shield of a satellite launch vehicle at Mach 0.8 at an angle of attack 5 deg. The present grid generation method is convenient for checking the grid independence test by varying the stretching factor. The quadrilateral grid generated by finite element, vector plot of velocity and contour plots of the computed flow field data are easily drawn with the help of MATLAB.
Study on Non-linear Contact Stress and Prognosis Analysis of Lug Joints With Misfits
Authors: L. Chikmath  , B. Dattaguru
Published: December 2023

Components of aircraft and other large scale structures are generally made in parts in order to facilitate easy manufacturing, assembly and dis-assembly. Lug joints with fasteners are preferred in several aerospace applications where their purpose is to connect primary load carrying members. Study on structural integrity of these types of joints becomes mandatory from the safety point of view. This requires in-depth understanding of science and technology of Structural Health Monitoring (SHM) at these joints. Analysis presented here deals with the critical locations of interference and clearance fit lug joints which continuously operate under fatigue loading. Both interference and clearance fits exhibit non-linear contact-stress variation above certain load level and this effect needs to be addressed for both fatigue and monotonic loading. The maximum Pull or Push loads causes high stress concentrations at critical locations along the pin-hole interface. With continuous usage of the component, crack like damages initiate at these locations and they grow till failure of the component. The non-linear prognosis analysis is carried out to generate the data required for SHM at any stage which can be used to estimate remaining life of the component.
Aero Elastic Analysis of Aero Spiked Body in a Supersonic Flow Field Using Experiment and Simulations
Authors: Shravya Manda  , P. Prasanna  , A. Kamalesh  , G. Jagadeesh  , P. Theerthamalai
Published: December 2023

The focus of this work is to study the structural response of an aero spiked body in a supersonic flow field of M 2.5 and at zero angle of attack. Fluid-Structure interaction simulations and wind tunnel testing have been carried out on the model for the above condition. 2-way coupled Fluid-Structure Interaction simulations have been carried out to study the aero elastic effect of the aero spike material. The wind tunnel testing for the select condition has been carried out at zero angle of attack for steel spike. The pressure measurement on the flat face cylinder from testing has been compared with that of the simulation data and presented here. Detailed analysis of aero spike deflections, stresses and induced forces due to the shock wave field have been discussed here in detail.
Green Aero Engines
Authors: Abc
Published: December 2023

no abstract
Effectiveness of KS Elements for Satellite Orbit Predictions With Earth’s Gravity and Drag Force
Authors: T.R. Saritha Kumari  , M. Xavier James Raj
Published: December 2023

This study is meant for understanding the efficiency of KS regular equations for satellite orbit prediction. The analysis is mainly concentrated on Low-Earth satellite orbit, where the forces due to non spherical nature of the Earth and atmospheric drag, plays important role. The classical Newtonian equations of motions for which solutions are unstable, cannot be used for long term prediction of orbit. Hence, in literature many transformations have emerged to stabilize the equations of motion either to reduce the accumulation of local numerical errors or allowing to use a large integration step sizes, or both in the transformed space. KS transformation introduced by Kustaanheimo and Stiefel, regularize the nonlinear equation of motion to linear differential equations of a harmonic oscillator of constant frequency. In this paper a detailed analysis on KS differential equations is carried out by including perturbations of Earth’s gravity and atmospheric drag for orbit predictions. The recurrence relations of associated Legendre polynomial and its derivatives are used for including higher order Earth’s gravity terms. To know the effectiveness of the theory, results are compared with the orbit of the actual space object, CZ-2D R/B, for 7 days duration. The comparison shows that the KS theory is one of the best theories for orbit predictions available at present.
Design and Analysis of an Intelligent Fire Detection System For Cargo Compartment of Aircraft
Authors: D.K. Chaturvedi  , Manik Chandra Singh
Published: December 2023

The fire detection system and fire warning are design features of an aircraft. The fire detection system protects the aircraft and passengers in case of actual fire during flight. But spurious fire warning during flight creates a panic situation in flight crews and passengers. The conventional fire alarm system of an aircraft is triggered by false signal. The artificial neural network has capability of fault tolerance and robust in nature. Its performance is dependent on its training, which is done on the real time data collected from the aircraft. Neural network based fire detection system provides real time surveillance, monitoring and automatic alarm. An intelligent fire detection system is developed based on artificial neural network in MATLAB using three inputs such as temperature, smoke density and CO concentration. This information helps in determining the probability of three representative of fire condition which is Fire, smoke and No fire. The simulated test results show that the identification error rates are very less. This greatly reduces leak check rates and false alarms. The neural network based fire detection system uses a variety of sensor data and improves the ability of system to adapt and accurately predict fires. It sends early alarm when the fire/smoke occurs and helps to reduce the spurious fire warning.
Computational Studies of Insect-Sized Flapping Wings In Inclined Stroke Plane Under the Influence Of Temporally Varying Shear Inflow
Authors: Manabendra M. De  , J.S. Mathur  , S. Vengadesan
Published: December 2023

2D computational studies on the effects of temporally varying shear inflow condition on forces generated by an insect-sized flapping wing in the inclined stroke plane have been carried out for Re = 150. Temporally varying shear inflow condition was represented by a combination of a mean wind speed term, a temporally fluctuating velocity term and a spatial velocity gradient term. The mathematical form followed the expression UG Uw = U∞ Uw +    Ug Uw    sin    2π fg fw t    ±    Vgrad Uw    y. Here, UG is the gusty inflow velocity in m/s, U∞ is mean free stream velocity in m/s, Ug is the amplitude of the temporally sinusoidal velocity fluctuation in m/s, Vgrad is the linear velocity gradient along the Y-axis in m/s per m, Uw is the root mean square average of the flapping cycle velocity of the wing in m/s, fg is the frequency of the temporally sinusoidal velocity fluctuation in Hz, fw is the wing’s flapping frequency in Hz, y is dimension along Y-axis in m and t is time in second. For the present studies Ug/Uw = 1 and fg/fw = 0.1 were chosen. Five cases with linear velocity gradient ratio along the Y-axis, Vgrad/Uw = ± 5, ± 2.5 and 0 were considered. Findings were analyzed by plots of instantaneous and cycle-averaged force coefficients, phase space plots, global recurrence plots and windowed recurrence quantification analysis. Numerical investigations revealed that negative Vgrad/Uw induced a considerable increase in vertical force and marginal decrease in the horizontal force. Positive Vgrad/Uw induced a marginal increment in horizontal force but caused a substantial decrement in vertical force.
PSLV: The Versatile Workhorse Launch Vehicle of India
Authors: Guruprasad B.R. , Mayilvaganan M.
Published: December 2023

Polar Satellite Launch Vehicle (PSLV), the maiden operational launch vehicle of India, has emerged as a very reliable and versatile launch vehicle by successfully launching satellites, both Indian and foreign, into a variety of orbits around the earth. Though India has subsequently developed two succeeding generation of launch vehicles - GSLV Mark II and GSLV Mark III - of higher capability, complexity and efficiency, nevertheless they have not acquired the conspicuous attention of the country as well as the outside world as PSLV has, through its numerous multifarious achievements. Despite its uncommon design of alternating solid and liquid stages, the robustness of the four stage PSLV design has been repeatedly proved by its successes as well as the resilience of the vehicle to quickly recover from rare failures. Besides launching a record number of 104 satellites in a single mission, PSLV has many other achievements to its credit including the launch of satellites into polar Sun Synchronous, Geosynchronous Transfer and sub-Geosynchronous Transfer Orbits as well as Low Earth Orbits of moderate and very low inclinations. This paper discusses several important aspects of PSLV including its lineage, development, configuration and improvements as well as its heritage, past contribution and future prospects on the occasion of its recent success in launching 31 satellites from India and eight other countries into two different orbits on November 29, 2018.
Validation of Paras3d Rans Pressure Data with Flight Results Over a Wing-body Rlv Configuration at Supersonic High Angle of Attack Conditions
Authors: Vidhya G , Manokaran K. , Babu C. , Das Dipankar , Patil M.M. , Ashok V. , Rasheed Haroon
Published: December 2023

Winged Reusable Launch Vehicle - Technology Demonstrator (RLV-TD) was successfully flight tested by Indian Space Research Organisation (ISRO). One of the main objectives of this Hypersonic Experiment (HEX) mission is to validate the aerodynamic design and ground based aerodynamic data generation procedure. In this paper, comparison of flight data and CFD estimated pressure coefficient (Cp) over fuselage, wing, vertical tail and rudder are presented at supersonic Mach number and high angle of attack conditions. PARAS3D RANS solver is able to capture the trends as measured in flight. In general, PARAS3D CFD over predicted the compression on windward side and under predicted leeward expansion as compared to flight measurement. In general, CFD predicts Cp close to flight measured value, except over a port in the vertical tail.
Numerical Simulation of Hydrogen-air Turbulent Diffusion Flame
Authors: Mahendhran M.
Published: December 2023

The hydrogen-air turbulent diffusion flame - DLR H3 (benchmark test case at the International workshop on Measurement and computation of turbulent non-premixed flames, Naples, July 1996) [http://www.sandia.gov/TNF/1stWorkshop/TNF1.html], is numerically modeled using commercial CFD software CFD++. For simplicity, a 5 degree sector of the domain is considered. Good comparison is obtained for the non-dimensional quantities reported in the literature [Cheng T.-C., Fruechtel G., Neuber A., Lipp F., Hassel E. P. and Janicka J., 1995, "Experimental data base for numerical simulations of turbulent diffusion flames," Forschung im Ingenieurwesen, 61 (6), pp. 165-171].
Application of Weighted Least Squares Meshless Method to Incompressible Flows
Authors: Arora Konark
Published: December 2023

Meshless methods have been successfully applied to solve a large number of inviscid and viscous compressible flows in both two and three dimensional flow fields. However, the conventional methods of solution for compressible flow equations cannot be applied to incompressible flow equations. This is due to the basic difference in the nature of the pressure variable in the compressible and incompressible flows. Pressure acts as a thermodynamic variable in case of compressible flows and can be easily updated by using the equation of state. In contrast, in case of incompressible flows, the pressure is merely responsible for enforcing the incompressibility constraint and hence cannot be updated by the equation of state. This has led to the development of numerical methods based on Helmholtz Decomposition to solve for the fluid flows in the incompressible flow regimes. Here, we have applied weighted least squares meshless method to solve for the flows in the incompressible flow regime using the projection method based on Helmholtz Decomposition. The standard test cases of two dimensional lid driven cavity flow at Reynolds numbers of 100, 400 and 1000 have been solved using the weighted least squares meshless method. A good match between the results of the test case using the meshless methods and conventional CFD methods for the solution of the incompressible flows has been obtained.
Cfd Analysis to Investigate the Effect of Leaned Rotor On the Performance of Transonic Axial Flow Compressor Stage
Authors: M Akash , Shobhavathy M.T. , Ajith Kumar R.
Published: December 2023

This paper describes the numerical study carried out to understand the impact of combination of forward and backward leaned rotor on the overall performance of a transonic axial flow research compressor of CSIR National Aerospace Laboratories (NAL), Bangalore. The analyses were carried out using commercial Computational Fluid Dynamics (CFD) solver Ansys-CFX. Initially CFD analysis was carried out for the baseline rotor configuration and validated the results with the experimental data. Then, three new configurations of combined Leaned rotors were modeled from the radially stacked baseline rotor by changing the circumferential curvature of original stacking line using three control points located at 0%, 50% and 100% of the blade span. Analyses were carried out for all the three configurations of modified geometries and the results were compared with the baseline configuration. The results revealed many interesting aspects which will be very useful for better understanding of the blade curvature effects on the shock and secondary losses within the transonic rotor. The discussions on the effect of combination of forward and backward leaned rotor and the consequent developments on the overall performance of the compressor are presented in detail in this paper.
Estimation of Turbulent Heat Transfer Rates for Flow Over Buildings Using Openfoam
Authors: Veena K. , Parammasivam K.M. , Venkatesh T.N.
Published: December 2023

Formation of Urban Heat Islands is one of the serious issues faced by the cities in India. Due to anthropogenic activities there are abnormal variations in temperature both in day and night in cities as compared to rural areas. When we consider the governing equations the heating coefficients present, which depend on the buildings and local flow, can accelerate or decelerate the effect of temperature in the urban areas. In this paper the coefficient called eddy diffusivity of heat and its influence around high-rise buildings is analyzed using Computational Fluid Dynamics simulations with the OpenFOAM software package.