bluuebunny/crossref_metadata_2025 huggingface dataset:
Flow Field Simulations Over Reentry Modules at High Speed
Authors: Mehta R. C.
Published: December 2023

Reentry capsule configurations significantly differ from each other due to entry conditions and mission requirements. This paper describes numerical simulations of the viscous flow over the Beagle and the OREX (Orbital Reentry EXperiments) configurations for freestream Mach numbers in the range of 1.2 - 5.0. The flow fields over the reentry modules are obtained by solving time-dependent axisymmetric compressible laminar Navier-Stokes equations. The fluid mechanics equations are discretized in spatial coordinates employing a finite volume method, which reduces the governing equations to semi-discretized ordinary differential equations. Temporal integration is carried out using a two-stage Runge-Kutta time-stepping scheme. A local time-stepping is employed to get the steady state solution. The numerical simulation is performed on a single-block structured grid. The flow field features around the reentry capsules such as bow shock wave, sonic line, expansion fan and recirculation flow in the base-shell region are well captured by the present numerical computation. The effects of the geometrical parameters of the module, such as aspect ratio, frontal segment bluntness, fore body cone angle and shoulder rounding radius on the wake throat width, distance from the wake throat to the base of the model, flow departure angle and aerodynamic drag are analyzed using the numerically simulated flow field.
Nonlinear Vibration Characteristics of Point Supported Isotropic and Symmetrically Laminated Plates
Authors: Daripa Rupesh , Singha M. K.
Published: December 2023

Nonlinear free and forced vibration characteristics of composite square plates either supported at four corner points or point supported at the middle of its edges as well as corners are investigated here using different high precision plate bending finite elements. It is observed that, higher order interpolation polynomial for the transverse displacement helps the plate bending finite elements to converge for the linear vibration frequencies. However, convergence for large amplitude vibration problems depends on the interpolation polynomials for in-plane displacements as well as transverse displacement. In general, the hardening nonlinearity (i.e., the increase of nonlinear frequency with vibration amplitude) of point supported plates is less than those of immovable simply supported plates.
Comparative Study of Probabilistic Structural Safety Analysis of a Titanium Pressure Vessel
Authors: Bhattacharjee P. , Ramesh Kumar K. , Janardhan Reddy T.A
Published: December 2023

Structural Reliability (Safety Index) is a very important factor of any aerospace product. Until recently, a design was considered robust if all the variables that affected its life had been accounted for and brought under control. The meaning of robustness is shifting. Designer and engineers have traditionally handled variability with safety factors. Some safety factors are derived from observation and analysis, and many cases it used to be pure guesswork. In those cases, the bigger the guess, the bigger the risk, the bigger the safety factor, resulting over designed product. Safety factor cannot, by themselves, guarantee satisfactory performance and they do not provide sufficient information to achieve optimal use of available resources. In this paper pressure vessel made of titanium alloy is considered for structural reliability study. Structural Safety Index is evaluated using uncertainty. Various statistical methods like mean value and moment methods are discussed. Simulation techniques for evaluation of probability of failure are also discussed. Response surface methodology which helps in solving many complex structural problems has been used. Finally, comparative studies have been made for various techniques. These techniques will be useful for Reliability design evaluation.
Eddy Current Methodology for Nondestructive Assessment of Thickness of Silicon Carbide Coating on Carbon-Carbon Composites
Authors: S. Thirunavukkarasu  , B.P.C. Rao  , T. Jayakumar  , N. Narayanankutty  , P.V. Prabhakaran
Published: December 2023

Eddy current (EC) methodology has been developed for non-destructive assessment of thickness of Silicon carbide (SiC) coating on carbon-carbon (C/C) composite specimens. For coating, polymer precursor route has been employed and approximate coating thickness has been determined by weight gain method. EC probe signal amplitude has been measured before and after the coating. Despite scatter in the baseline data due to surface roughness on C/C specimens, EC methodology could identify undercoated (thickness <20 µm) specimens. A calibration graph has been established between EC signal amplitude and coating thickness (weight gain) to evaluate the performance of the EC methodology. The methodology has evaluated the coating thickness with error less than ±5 µm. Studies confirm that it is possible to assess the efficacy of coating process and to readily identify thinly coated regions using eddy current imaging.
Optimisation of Vacuum Brazing Conditions for Joining Stainless Steel 321 Sheets by Nickel Based Braze Foil for Regenerative Rocket Nozzle Applications by Taguchi Method
Authors: D.P. Sudhakar  , V. Vinodh Babu  , Abhay K. Jha  , M. Rajmohan  , A.E. Muthunayagam
Published: December 2023

This paper outlines the optimisation of vacuum brazing conditions for joining titanium stabilised Stainless Steel SS321 sheets by Ni-based braze alloy (Ni-Mn-Cr-Co-Si) as brazing filler metal (BFM) for two shelled rocket nozzle applications. This is a specialized brazing technique in which multiple parameters such as temperature, time, argon pressure in the furnace and vacuum level in the channels between the shells are to be precisely controlled in a complex furnace. Brazing temperature, holding time, surface pressure in terms of dead weight and vacuum levels were identified as parameters having significant effect on the bonding strength of a braze joint. Taguchi method was used as a statistical technique for design of experiments to optimise brazing conditions in terms of shear strength. L9(34 ) orthogonal array was designed for conducting the experiments with four parameters at three levels ie temperature (1190oC, 1230oC,1270oC), holding time (10min, 20min, 30min), surface pressure (100kPa, 150kPa, 200kPa) and vacuum level (0.133Pa, 1.33Pa, 13.3Pa). The optimised set of parameters ie temperature: 1230oC, time: 20min, pressure: 100kPa, vac. level: 1.33Pa has been arrived at by Taguchi method via statistical analysis through analysis of means (AVOM) and analysis of variances (ANOVA). Confirmatory test for optimised conditions agreed well with the Taguchi analysis. Also, extensive optical metallography and energy dispersion X-ray analysis across the joint were carried out to study the metallographic morphology across the joint. The fractured surfaces during lap shear tensile testing have also been studied under SEM.
Lightning Strikes on Metal and Composite Aircraft And Their Mitigation
Authors: R. Prabhakaran
Published: December 2023

In this paper, the history of aircraft accidents due to lightning strikes and the statistics of lightning strikes on commercial aircraft are briefly mentioned. The mechanism of interaction between lightning and aircraft is described. Lightning can be simulated in the laboratory. Lightning testing is based on identifying and reproducing the key elements of a typical lightning current waveform; and also on classifying the various parts of an aircraft into different lightning zones. The evolution of aircraft structural materials from wood to metal to composites is traced; some of the newer hybrid materials (‘fibre-metal laminates’) that combine the advantages of metals and composites are mentioned. The lightning mitigation measures implemented by the world’s two major aircraft manufacturers, Airbus and Boeing, are briefly described. Some of the nanomaterials proposed for enhancing the surface electrical conductivity of structural composites are reviewed.
Defect Trend Analysis for a Military Turbojet Engine: Case Studies
Authors: K.S. Jayasimha  , R.K. Mishra  , S.N. Mistry
Published: December 2023

Turbojet engines are currently used for military application under training and combat modes. Their operation at extreme conditions often unscheduled with need based throttle excursions lead to high cyclic stresses on engine components and unusual demands on line replaceable units and accessories. As a result, a number of engines are forced for premature withdrawal from service affecting the flight schedule of the operator. This present paper presents the trend analysis of various defects encountered in a military turbojet engine and its accessories. This analysis will help in identifying the probable causes of the defects, time of engine withdrawal and whether they are of reoccurring nature or isolated cases so that corrective action can be initiated to avoid such snags in future.
Numerical Exploration of Staged Hydrogen Combustion in A Strut Based Scramjet Combustor
Authors: Soumyajit Saha  , Debasis Chakraborty
Published: December 2023

Scramjet combustor with fuel injection from strut and wall is numerically simulated using three-dimensional Navier Stokes equations along with k - ε turbulence model. Turbulence - chemistry interaction is modeled through Eddy Dissipation Concept (EDC) based on infinitely fast rate kinetics. The simulations captured all the essential features of flow field for various combinations of fuel injections from the strut and the wall. The computed surface pressures match very well with the experimental values for both reacting and non-reacting cases. Performance parameters are evaluated from the computed flow variables. It was found that more fuel could be injected in the scramjet combustor through staged injection without inlet - combustor interaction.
Nonlinear Aerodynamic Modeling of Cascade Fins And Delta-Wing Aircraft Model
Authors: Rakesh Kumar  , Ajay Misra  , A.K. Ghosh
Published: December 2023

The paper presents the modeling of the nonlinear longitudinal aerodynamics associated with the cascade fins and scale-down model of a delta-wing aircraft at high angles of attack. The Kirchhoff’s steady-state stall model was used to model the stall characteristics and the Maximum Likelihood (ML) method was used to estimate the stall characteristic parameters. The cascade fin models with a rectangular and an airfoil (NACA-0012) cross-section were used to generate the variation of lift coefficient with angle of attack. The wind tunnel data pertaining to the cascade fin models were generated by varying the gap-to-chord ratios with and without end plates. The effect of end plates and the gap-to-chord ratio on the stall characteristics and the parameter estimation was analysed. The estimation results were compared to the reference results. In addition, the application of the Kirchhoffs steady-stall model to the scale-down model of a delta-wing aircraft has also been presented. The analysis pertaining to the cascade fins can be utilized as a basis for an initial design of cascade fins for guided missiles with desirable stall characteristics.
Comparison of Requirements for Composite Structures for Aircraft and Space Applications
Authors: S. Raju Ivatury , B. Elliott Kenny , W. Hampton Roy , F. Knight Norman , Aggarwal Jr., Pravin , P. Engelstad Stephen
Published: December 2023

In this paper, the aircraft and space vehicle requirements for composite structures are compared. It is a valuable exercise to study composite structural design approaches used in the airframe industry and to adopt methodology that is applicable for space vehicles. The missions, environments, analysis methods, analysis validation approaches, testing programs, build quantities, inspection, and maintenance procedures used by the airframe industry, in general, are not transferable to spaceflight hardware. Therefore, while the application of composite design approaches from aircraft and other industries is appealing, many aspects cannot be directly utilized. Nevertheless, experiences and research for composite aircraft structures may be of use in unexpected arenas as space exploration technology develops, and so continued technology exchanges are encouraged.
Strategies for Improving the Damage Tolerance of Future Composite Materials
Authors: Hogg P. J. , Potluri P.
Published: December 2023

Improving the damage tolerance of a composite is identified as a key goal for future developments. A change in emphasis is suggested with a move away from the philosophy of improving performance by increasing the resistance of the laminate to damage formation, which should be accompanied by attempts to control the nature of damage such that energy can be absorbed through cracking in a way that is not deleterious to the final properties of the structure.

Different strategies are proposed to achieve this, consisting of specific attempts to maximise the resistance of the laminate to damage growth by improving interlaminar toughness, GI (prop) or by introducing new architecture into the composite such that the nature of damage is modified. Examples are provided of the use of interlaminar veils, 3D textile forms and the use of specific fiber hybridisation to facilitate the improved resistance to crack propagation.
Non-Linear Structural Analysis of Shear Flexible FGM Beams
Authors: Sanjay Anandrao K. , Gupta R.K. , Ramachandran P. , Venkateswara Rao G.
Published: December 2023

Non-linear structural response of Functionally Graded Material (FGM) beams is studied using the finite element method. The deformations obtained using Euler-Bernoulli beam and Timoshenko beam theories are compared for different length to height ratios, volume fraction exponents and boundary conditions. The percentage errors in lateral deformations for neglecting the effects of shear flexibility are discussed in detail. Through thickness variation of the axial stress shows a shift in the neutral axis from the mid-thickness of beam for homogenous as well as FGM beams and for the boundary conditions considered. The range of volume fraction exponents for the practical design of FGM beams is suggested to avoid steep stress gradients.
UAV Design and Configuration Aerodynamics - An ADE Experience
Authors: Balachandran N.
Published: December 2023

UAVs are becoming an essential part of the modern defense forces world over in the recent years. They are widely used for surveillance, reconnaissance, target for missiles and combat. They are available in various weight classes from few kilograms to tons. Apart from design of aircraft, establishing an accurate aero data base for control law design for the aircraft is a main challenge in itself. Aeronautical Development Establishment (ADE) is involved in the design and development of many UAVs for the last 30 plus years and has experienced several challenging design and engineering problems. Over the years, various UAVs like Ulka, Sparrow, Lakshya, and Nishant for different mission requirements have been designed and developed. The evolution of design methodology in ADE and the present configuration design activities of UAVs and aircraft stores separation studies with a focus on CFD are discussed in this paper.
Flow Control in Serpentine Inlet Duct Using Vortex Generator Jets
Authors: Chandra Sushant , Keerthi M.C. , Kushari A. , Sullerey R.K.
Published: December 2023

The objective of the present research is to study the effectiveness of steady and pulsed vortex generator jets in reducing inlet flow distortion and in improving pressure recovery by effective secondary flow control in uniform inflow serpentine duct diffuser. The measurements were carried out at a test Reynolds number of 6.5 x 105 based on the diffuser inlet width. Serpentine duct diffuser consisted of two main portions, namely, a square to circular constant area transition duct followed by a circular diffusing duct. Investigations show that the flow in the serpentine diffusing duct suffers from stall on the inner wall and consequently the outflow at AIP has considerable flow distortion due to the combined effect of secondary flow and the inner wall stall. It is observed that the use of vortex generator jets, both in steady and pulsed modes, improve the performance substantially. The number of jets, location of jets, velocity ratios and the pulse frequency are some of the variables that are studied. The results obtained so far suggest that use of pulsed jet not only gives better performance but also reduces the amount of air that is needed to be injected through the jets in comparison to steady jets for similar velocity ratios.
Numerical Simulation of Underexpanded Sonic Jet
Authors: Dharavath Malsur , Chakraborty Debasis
Published: December 2023

Underexpanded sonic jet is numerically simulated using commercial CFD software. Three dimensional Navier Stokes equations alongwith two equation turbulence models are solved. Computed centerline distribution and profiles of various flow variables at various axial stations agree quantitatively with experimental results. The comparison of the flow variables computed with four different two equation models reveals that k - e and RNG k - e models perform very well in predicting both pressure and temperature throughout the flow filed; whereas SST and k - w models fail to predict the flow behavior beyond the first Mach disc.
Novel Approaches in Detail Design of Composite Structures: Case Studies
Authors: Senthil Nathan K. , Naik B.N. , Gaddikeri Kotresh M. , Varughese Byji
Published: December 2023

The detail design plays a vital role in the development of composite structures by exploiting the ability of composites for integral construction through cocuring technology. Detail design takes into account the requirements from stress, tooling, manufacturing and assembly to conceive the component. This paper addresses two case studies, wherein, the detail design of components in the wing of a transport aircraft was carried out using integral construction. The design was compared with the existing design on a prototype aircraft. The ingenuity of configuration led to several benefits associated with cocuring. In the first case, the wing tip structure was designed with fewer parts co-cured with reduced weight and part count thereby amounting to lesser tooling and manufacturing effort. In the other case, the flap track rib was designed by integrating two I-section ribs into one composite rib which led to increased stiffness and smooth diffusion of flap track loads into wing structure.
Aircraft Fuel Estimation by Least Square Technique
Authors: Shantha Kumar N. , Narayana Rao P. , Naidu V.P.S.
Published: December 2023

A least square estimation technique has been proposed for in-flight fuel estimation for a high performance combat aircraft. This paper presents the details of least square models for aircraft fuel estimation, the procedure for building the least square models and their fidelity to estimate the fuel quantity in the multiple internal fuel tanks of the aircraft from flight data. The performance of the fuel estimation by least square technique has been verified with 56 different post flight data with different maneuvers including probe failure cases and compared with lookup table based estimates, the technique currently being used on the aircraft. Few results of fuel quantity estimates are presented and discussed. Sensitivity of the least square model based fuel estimation technique to probe failures has been studied by simulating multiple probe failures in flight data.
Evaluation of Internal Flow Path of two Module Scramjet Combustor Through Sectional Measurement
Authors: Singh Kushal , Ashok Ponram R. , Hari Prasad B. , Bhattacharjee P.
Published: December 2023

The Internal flow path of a scramjet combustor consists a gradual varying cross sectional area along the combustor axis. The performance evaluation and prediction of combustor are based on Computational Fluid Dynamics (CFD) and Structural Analysis simulations which are carried out on a designed 3D CAD model. Due to manufacturing process constraints and assembly process there can be deviation in the hardware from the designed internal flow path of combustor. Thus it is necessary to determine the actual internal flow path of combustor, which in turn can be used for CFD and structural analysis simulations for better performance evaluation and predictions. The paper presents the methodology developed for evaluation of cross-sectional areas along the combustor axis and generation of 3D surface CAD model of actual internal flow path using CNC Coordinate Measuring Machine (CMM) and design CAD software. It also includes the methods adopted for CMM probe compensation while measuring slopes on the combustor surface and for the measurement of inaccessible surfaces by Ultrasonic Thickness Measuring Instrument.
CFD Analysis of Over-Expanded Flow in Convergent Divergent Nozzles
Authors: Thanusha M.T. , Rahul B.V. , Roy Swapneel , Khan A.A.
Published: December 2023

The classical one-dimensional inviscid theory does not reveal the complex flow features in an over-expanded nozzle accurately. The code Fluent has been used to simulate the viscous fluid (air) flow passing through three different 2-D Convergent-Divergent (C-D) nozzles for nozzle pressure ratios (NPR) corresponding to over-expanded flow. The steady state RANS equation with five different turbulence models has been simulated for turbulence model study. Two different types of boundary layer grids: grid1 (y+=1) and grid 2 (y+</sup=50) have been simulated. Shear Stress Transport k-w (SSTKW) turbulence model with grid 1 has been chosen for turbulence modeling. Both inviscid and viscous flows have been simulated. The converged solutions captured asymmetric lambda shock in all the three nozzles at higher NPRs for viscous flows. It also predicted aftershock and flow separation depending upon NPR. The shock wave angle of the incident and reflected shock generally reduces with increase in NPR for NPR£1.92. The thrust co-efficient of all the theoretical, predicted inviscid and predicted viscous solutions reduce with increase in NPR upto a certain value of NPR and then starts increasing. The predicted viscous results (shock structure, shock location, size of normal shock, aftershock and asymmetric lambda shocks) are close to the experiments in most of the cases. The aftershock phenomenon provides dual mode flow at the exit of the nozzle.
Numerical Simulation of Flow Field Over a Sharp-Tipped Double Cone at High Speed
Authors: Mehta R.C.
Published: December 2023

The flowfield over a sharp-tipped double cone axisymmetric configuration is carried out by solving time dependent axisymmetric laminar compressible Navier-Stokes equations for freestream Mach number range of 2.0 - 6.0. The fluid dynamics equations are discretized in spatial coordinates using integral formulation in conjunction with finite volume method which reduces the governing equations to semi-discretized ordinary differential equations. Temporal integration is performed employing multistage Runge-Kutta time-stepping scheme. A local time step is used to achieve steady-state solution. The numerical computation is carried out on a mono-block with structured grids. The flowfield features over the sharp-tipped double cone configuration such as conical shock wave, separation region, separation and reattachment shock wave and bow shock wave in the cone region, expansion fan, and recirculation flow in the base region are well captured at Mach number 3 and 6 which are identical to the Edney VI type shock interaction. The velocity vector, Mach contours plots and variations of surface pressure coefficient along the sharp-tipped double cone configuration are analyzed at various Mach numbers. The fore-body aerodynamic drag is calculated employing computed pressure distribution. The paper presents the influence of the freestream Mach number on the flows with shock interactions over the sharp-tipped double cone geometry.
Secondary Flow in Rotating Ducts
Authors: Sumanth  Krishna , Govardhan M.
Published: December 2023

A simulation study is performed on laminar flow of an incompressible viscous fluid through rotating ducts. The ducts considered were rectangular straight, rectangular curved and circular curved. Simulations were carried out at two Reynolds numbers, three rotation numbers and five radii of curvature. Secondary flow is induced due to the rotation as well as the curvature of the duct independently, and this can be observed by the presence of double vortex in the bend region and in the downstream region of the rotating duct. Secondary flow creates unwanted losses in the flow. In the present study, the variation of the losses is estimated by plotting the secondary flow kinetic energy and the total pressure loss coefficient for different radii of curvature and rotation speeds. It was observed that both the coefficients increase rapidly in the curved region. The total pressure loss coefficient keeps increasing along the length, while the secondary kinetic energy coefficient decreases after peaking in the curved portion and converges to a constant value. This flow phenomenon, especially in turbines and rotating coolant channels are of practical interest in such applications as heat exchangers, rotors of electrical machinery, cooling channels of gas turbine rotor blades. Therefore it is important to understand the underlying physics, which could help in the design of turbomachines and in optimizing heat transfer rate in the relevant applications.
Development and Modal Analysis of Bioinspired CNT/EPOXY Nanocomposite MAV Flapping Wings
Authors: Kumar David , Goyal Tigmanshu , Kumar V. S , Mohite P.M. , Kamle Sudhir , Verma Vivek
Published: December 2023

The aim of the present work is the development and modal analysis of hummingbird inspired MAV flapping wings. Carbon nanotubes (CNTs)/epoxy nanocomposite is chosen as the material for wing fabrication. The nanocomposite has been developed and characterized using dynamic mechanical analyzer for its dynamic viscoelastic properties. Wing designing is done by obtaining the data points from 2D full-flexed giant hummingbird wing image using digitizer. The fabrication of wings is done using molding manufacturing technique. Wing mold is made out of Perspex sheet using laser engraving machine. Modal analysis has been performed in air/normal environment and vacuum chamber. The results are used for determining the repeatability of wing manufacturing technique, too. A 3D model of wing is used for computational modal analysis using commercial finite element software ANSYS. The results from experiments and ANSYS simulations are compared and found in good agreement with each other.
Reflector Design for Simulating Varying Heat Flux on Nose Cap of a Re-entry Module
Authors: C. Varghese Rony , Sundar B. , Chacko M. J.
Published: December 2023

For thermo-structural tests of a nose cap for a re-entry module accurate simulation of time and space varying heat flux is essential for generating the actual temperature gradients as expected in flight. Temperature gradient simulations along with simulated structural loads are essential for testing the structural integrity of the C-C nose cap.

Contoured reflectors are essential for obtaining spatial distribution of incident heat flux. For realizing the reflector for thermo-structural testing, it is important to design radiation reflectors that will generate required heat flux envelope along the nose cap geometry. Reflector design for simulating varying heat flux on re-entry nose cap has been carried out by estimating view factor between nose cap and for different geometries of reflector.

Design could be accomplished by making use of view factor algebra. Elemental heat flux values were validated with literature data and methodology for reflector heat flux design was validated against test data. With single flat reflectors and multiple flat reflectors, the required spatial variation of incident radiative heat flux could be realized efficiently. View factor variation is compared with heat flux variation along the nose cap. It is recommended practice to have multiple reflectors for simulating required varying heat flux on the nose cap due to better flexibility.
Forced Vibration Study of Carbon Nanotubes Using Non-Local Elasticity and Timoshenko Beam Theories
Authors: Pradhan S. C.
Published: December 2023

Forced vibrations of the single wall carbon nanotubes (SWCNTs) using the non-local elasticity theory and Timoshenko beam theory is studied. Governing equations for the vibration response of the carbon nanotubes are derived employing Eringen’s nonlocal elasticity theory. Analysis is carried out for both EulerBernoulli beam theory and Timoshenko beam theory. Present forced vibration results for Euler-Bernoulli are in good agreement with those reported in literature. Effects of (i) nonlocal parameter (ii) length of the carbon nanotube and (iii) modes of vibration on the vibration response of the carbon nanotubes are investigated. The effect of nonlocal parameter on the vibration response are significant for small size carbon nanotube and higher modes of vibration.
Reliability Assessment of Functionally Graded Material Under Thermal Loading
Authors: Pradhan S.C. , Viswanath  , Chaturvedi S.K.
Published: December 2023

In this paper, the reliability index of the stainless steel and alumina Functionally Graded Beam (FGB) subjected to various boundary conditions and changes in temperature is studied. A FGB of known dimensions with material properties graded according to power law distribution is considered. Effects of boundary conditions, material grading and temperature on the reliability index of the beam are studied under various loading conditions. In order to evaluate the reliability index of the beam, First Order Reliability Method II (FORM-II) is employed. The code written in MATLAB pertaining to the proposed approach is validated with an isotropic beam problem whose results are available in literature. With an objective to formulate a relationship between reliability index and various parameters to assist designing under constraints, an attempt is made to study and derive a relationship of reliability index as a function of power law index, temperature and boundary conditions. Explicit expressions of analytical correlation to some specific problems under different boundary conditions and temperature are deduced to demonstrate the usefulness of the correlation.
Controlling Dynamic Stall With an Active Flexible Wall
Authors: Mangla Niranjan L. , Sinha Sumon K.
Published: December 2023

A low energy active flexible wall transducer has been used to interact with unsteady separating boundary layers over a pitching NACA 0012 airfoil, at a Mach Number of 0.1, Reynolds Number around 6 E 05 and reduced frequencies around 0.1. The transducer consisted of an array of thin strip shaped high and low electrodes covered with an aluminized Mylar membrane. An electric excitation was given to two adjacent strips generating vibrations of the membrane of around 0.01 μm amplitude over the actuated strips. The pressures were measured along the central chord axis using a pressure scanner. The electric excitation of the transducer at a frequency corresponding to Strouhal Number (based on strip spacing and local free stream velocity) of approximately 1 delayed the onset of dynamic stall by 2°. The maximum actuation power consumption was 1 W for 30 cm of actuated length in the span wise direction.
Smoothened Absolute Kinematic Position Estimation Of Leo Satellite Using Gps Observables
Authors: Ganjoo Ishita , Kumar Vinod Kumar
Published: December 2023

In this paper, our objective is to use the navigation signals (pseudorange and carrier phase measurements) from GPS to kinematically estimate the absolute position of a low Earth orbit satellite and its receiver clock biases. GPS observables can estimate the precise position of a satellite in near real time. The GPS satellite navigation file is downloaded from Scripps Orbit and Permanent Array Centre (SOPAC) website for starting epoch of 01-01-2016 00:00 UT. The observables are then generated for a Low-Earth-Orbit (LEO) satellite at an altitude of 901.4 km. The absolute position is estimated using pseudorange measurements. The accuracies obtained are (5.68 8.04 6.17) m in ECEF frame. This estimated absolute position is then smoothened with the time-differenced carrier phase measurements. The Kalman filter gains are computed in near real time. The smoothened accuracies obtained are (2.24 2.60 2.6982) m in ECEF frame, thus showing improved estimated absolute position accuracy.
Strength Prediction and Damage Assessment of Laminated Composite Plates With Rectangular/Square Cutout Using Finite Element Method
Authors: Lakshminarayana A. , Vijayakumar R. , Krishnamohana Rao G.
Published: December 2023

The progressive failure analysis of symmetrically laminated rectangular composite plate [0/+45/-45/90]2s with square/rectangular cutout under uniform uniaxial compression loading is carried out using finite element method. Hashins failure criterion is used to predict the failure of lamina. A parametric study has been carried out to study the influence of square/rectangular cutout size, cutout orientation and plate thickness on the ultimate failure load of laminated composite plate under uni-axial compression loading. Ultimate failure loads were computed for six different laminate configurations [0/+45/-45/90]2s, [75/-60/30/-15]2s, [0/90]4s, [-45/45]4s, [15/-75]4s, [30/-60]4s. It is observed that the laminate stacking sequence, plate thickness , cutout size and cutout orientation has substantial influence on the ultimate failure load of notched composite plates.
Grid Free Euler Flow Solver With Cuda Computing
Authors: P.V.R.R. Bhogendra Rao  , K. Anandhanarayanan  , R. Krishnamurthy  , Debasis Chakraborty
Published: December 2023

Graphics Accelerators are increasingly used for general purpose high performance computing applications as they provide a low cost solution to high performance computing requirements. Intel also came out with a performance accelerator that offers a similar solution. However, the existing application software needs to be restructured to suit to the accelerator paradigm. Master-slave software architecture has been employed to enable two-dimensional and threedimensional grid-free Euler flow solvers in GPGPU computing platforms. Results showing significant improvement in the performance are presented in this paper. Convergence histories and aerodynamic forces obtained from GPGPU computing are compared with that of sequential computing results.
Mass-Flow Simulation in Air-Intake Models at Subsonic Mach Numbers Using Diffuser of Wind Tunnel As Passive Ejector
Authors: G.K Suryanarayana  , M. Bikshapathi  , Y. Gireesh  , P.R. Gopinath  , S. Suresh Kumar  , D.B. Singh  , Buddhadeb Nath  , N. Karthik  , N. Srinivasan
Published: December 2023

In order to ensure adequate mass-flow rate at low Mach numbers through air-intake models in a blow-down wind tunnel, the diffuser of the wind tunnel was used as a passive ejector. The ejector action was accomplished by interconnecting the exit plane of the intake model to a low-pressure region downstream of the choked second throat of the tunnel. Due to the reduced back-pressure, there was a significant acceleration of the entry flow, as indicated by nearly doubling of the inlet velocity. Measurements indicate that for an aircraft air-intake model, as well as a submerged air-intake model, the maximum mass flow rate achievable through the control plug was accomplished even at the lowest Mach number of 0.30, obviating the need for using an active ejector system.
Numerical Simulation of Flow over an Airport During A Low-level Wind Shear Event
Authors: Arshad Shameem C. , Saravanakumar J. , Venkatesh T.N.
Published: December 2023

In this paper we present the flow features of a severe low-level wind shear event near an airport simulated using a high-resolution numerical weather prediction model. The open-source model Weather Research and Forecasting (WRF) was used for the numerical simulations. Our initial analysis shows the ability of the model in capturing the possibility of the wind shear event.
Failure Mode Effect Analysis of Composites Prepreg Manufacturing Process for Airworthiness Certification - A Case Study
Authors: Kosgi Amarnath , Giri S. N. , Raghunath A. R.
Published: December 2023

Airworthiness certification of aircraft structures requires a holistic approach ranging from material manufacturing process to design evaluation of airframe components. Present day airframe structures find greater applications of composite materials owing to their extraordinary mechanical properties on pro rata weight basis. In case of polymer based composites, the prepreg form of material is preferred for several applications due to matrix efficiency (high fiber-to-volume ratio) and ease of application. As part of composite material certification, the design audit of composite prepreg manufacturing process is carried out to assess the possible failure scenarios. Manufacturing Process Design and Control plays a significant role in satisfactory realization of composite parts right from raw material stage. Process variability/ scatter can lead to large variation in performance of the final product and thus stringent control of process parameters is essential to achieve aero-grade composite structures. This study provides basic understanding of composite prepreg manufacturing process and application of FMEA as a process design tool to detect and assess potential failures with an aim to devise preventive measures for improved process control. The complete process of manufacturing prepregs is divided into three stages viz.: Fabric weaving, Resin formulation and Prepregging operation. FMEA principles are used to identify the predominantly vulnerable operations and to quantify the inherent risk associated. Risk Priority Numbers (RPN) are evaluated for various operations in these three stages. Based on process technology and engineering expertise, suitable corrective and preventive measures are offered according to the potential risk factors and failure types. Emphasis is to prioritize the efforts and attention towards major preventive measures by targeting the least number of factors causing the maximum impact for failures (Pareto principle). Present study substantiates the significance of trained personnel, proper documentation of operating procedures and work instructions along with contamination control as critical factors in eliminating failures in composite prepreg manufacturing process.
Computational Evaluation of Rotor Alone Noise
Authors: Venkatesan Rahul
Published: December 2023

Transonic 2-Dimensional flow past the rotor was simulated to predict the pressure variation past the rotor through the CFD software ANSYS-Fluent. The mesh generated was found to have a direct impact on capturing the shock and effect of change in the angle of attack through the flow past the rotating blades were found to vary the strength of the passage shock between the blades. The effect of blade geometry on the fan noise radiated near field and far field were investigated. Through the effect of grid refinement, change of chord length and thickness the noise generated by the rotor was found to reduce considerably to an extent. The effect of blade geometry on the fan noise was also studied. The results were in good agreement with the available data from the literature which was evident from the N-waveform.
Determination of Time Constant of Temperature Sensors and its Application in Aero Gas Turbine Engines
Authors: George Benny , Muthuveerappan N.
Published: December 2023

Temperature sensors are widely used in aero gas turbine engines for measurement of air and gas temperature at various locations starting from inlet of fan to exhaust gas from the nozzle. Thermocouples are one of the most widely used sensors for the above purpose. Time constant of thermocouple is a key parameter in the selection of sensor for a particular application. Even though time constant is available for standard stand alone thermocouple configurations, it varies widely based on many physical parameters and inlet flow conditions inside a gas turbine engine. Experimental determination of time constant of stand alone thermocouples with step input is carried out for various thermocouple configurations and a Fibre Bragg Grating sensor using a dry block calibrator with hot air as medium. Two different methods are used to determine the time constant of thermocouple sensors. Further determination of time constant of thermocouple assembled in a rake and tested in real time situation in aero gas turbine engine is carried out. A comparative study reveals that many parameters are involved which influence the value of time constant under different input conditions. Finally the selection of sensors is carried out based on the measurement requirements.
Indian Space Reforms : Providing Added Thrust through Enhanced Partnership with the Private Sector
Authors: Guruprasad B.R.
Published: December 2023

No Abstract.
Trajectory Analysis of a Solid Fuel Ramjet Propelling an Artillery Shell
Authors: Velari Yogeshkumar , Ramakrishna P. A.
Published: December 2023

This paper intends to estimate the possible range of a 155 mm artillery shell propelled using a ramjet in a fuel-rich propellant configuration. It also intends to obtain an optimum design of ramjet to maximize the range. A six degree of freedom trajectory simulation was developed to obtain the trajectories of the shell with a ramjet, which dynamically evaluates the off-design performance of the ramjet during the flight. A fuel-rich propellant was taken from literature for evaluating the performance of the ramjet. Various trajectories of shell were obtained at different initial thrusts and A/F ratios and with a constant combustion efficiency of 0.95. Results showed that with a 39-calibre gun, the range enhancement of around 105% compared to the current range of 24 km was obtained with a 155 mm artillery shell without any base bleed unit. This was achieved for the ramjet providing thrust equal to 1.2 times the drag at sea level with an initial A/F ratio of 11.
Numerical Simulation and Characterization of Swirl Fluid Motion through Cylindrical Chambers
Authors: Karthika A.S. , Suneesh S.S. , Anil Lal S. , Jayachandran T.
Published: December 2023

Axisymmetric solution of radial, axial and tangential components of velocity of flow through a cylindrical chamber with an inflow containing swirl and outflowis investigated numerically using Finite Volume Method. An in-house developed computer code for solving the three components of velocity and pressure is developed and validated using experimental data available from literature on the problem of axial vortex breakdown of confined flow in a cylinder due to rotation of one of the end walls. The code uses a staggered approach and fractional step projection method for decoupling the velocity and pressure. The convection and diffusion terms are approximated using a second-order accurate central difference scheme. This paper discusses the characteristics features of flow such as mixing streams, streams of fluid flowing close to the solid walls (cooling streams), swirl motion and development of flow structures.
ROLE OF TREMOR SYNDROME IN DIFFERENTIAL DIAGNOSTICS OF DISEASES
Authors: Agaeva N.Z. , Hasanov R.L.
Published: December 2023

The aim of the study was to examine the clinical features of the tremor syndrome. 72 patients with Parkinson's disease and 26 patients with essential tremor were examined. Disease diagnosis is based on the 2017 Movement Disorder Society (MDS) criteria. Along with standard neurological examination and neuroimaging, clinical features of tremor were studied in patients. It was found that in 35% of cases with Parkinson's disease and essential tremor, the syndrome manifests itself in a combined form. Thus, the patients showed a combination of resting tremor, postural tremor and kinetic tremor. This creates certain difficulties. Therefore, in the presence of a combined manifestation of tremor, the determination of his leading type, its dynamic observation and the detection of other neurological syndromes accompanying tremor can help in the diagnosis of the disease.
THE ROLE OF PREDICTIVE MARKERS IN THE DEVELOPMENT OF HIV ENCEPHALOPATHY IN CHILDREN
Authors: Saidkhodjaeva S.N.
Published: December 2023

This article presented the clinical-neurological and immunological examination results of 260 children with HIV-encephalopathy (HIVE) of various severity. All children included in the study studied the activity of HIV replication in mononuclear and other indicators that are candidates for the role of a predictive marker of the course of HIVE. Furthermore, the relationship between these indicators and the severity of HIVE was also studied. In addition, the study evaluated the activity of Il-6, IL-10, TNF-α, C-reactive protein, C3, C4 complement components and the predictor significance of various parameters of systemic inflammation in the aspect of the development of symptomatic HIVE.
The Value System of Unevenness
Authors: Öllös László
Published: December 2023

Unevenness has become a moral category. It is something to be protected and preserved. The moral essence of unevenness is the assertion that certain elements of underdevelopment are more valuable than a state of development. However, the masters of semi-detachment have another challenge to meet. Its believers must also separate their societies from each other. Towards their Eastern conquerors they try to present themselves as more Eastern (i.e., more communist more pro-Russian). If the conqueror is Western (e.g., National Socialist Germany) then they endeavor to present themselves as more pro-German than their neighbors, and in joining the democratic West they try to present themselves as more Western, consciously pushing back their neighbors. Moreover, if they approach the East and the West at the same time, they argue both ways simultaneously. This attitude also motivates the specific role of nationalism in our region. In our case, the role of national identity is not only the same as it used to be in the most developed parts of Europe, but here in Central Europe it has also had to justify the unevenness of state and society.