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Computational and Experimental Study for Reducing Forebody Wake Effect by Proper Designing of a Slit cut Square Parachute used for Sonobuoy Drop
Get PDFThis paper discusses the design of a square parachute based on classical approach, computational analysis and experimentation. This parachute will be used to drop directional sonobuoy on the sea to locate and classify the submarines. Design improvements are brought out by providing slits into a solid square canopy of parachute to bring in more stability and minimum drift during descend. Specifically, the effect of upstream sonobuoy, RANS model, suspension line length, canopy size and slit size in flow structure were considered. The predicted drag coefficients obtained from CFD for square canopy with slit-cuts compared with the results of wind tunnel experiment and found that the increase in the suspension-line length and/or of the surface area of the parachute canopy helps in better stability and results in the minimum drag loss
System Reliability Estimation of Divert Attitude Control System of a Launch Vehicle using Bayesian Networks
Get PDFDivert attitude and control system (DACS) is a one-shot system and provides attitude correction and translation of the Launch vehicle. DACS consists of many flight critical sub systems which are arranged in a series configuration. The traditional Reliability block diagram and Fault tree diagram methods are unsuitable for reliability modelling, when considering uncertainty among the components and system. Bayesian network is the natural choice to model dependencies among the components and system. DACS being one shot system, it is very expensive and time consuming to test more number of systems during the design and development. Hence the data is drawn from component level, subsystem level and expert opinion is used for reliability estimation. In this paper, Bayesian network modelling of DAC system was carried out for estimating the reliability using multi-level data. An algorithm is developed for computation of Conditional probabilities in Bayesian network. Posterior probability distribution of components is calculated using Markov Chain Monte Carlo (MCMC) simulations and results are compared with Junction tree based exact inference algorithm. MATLAB code is developed to estimate the reliability of DAC system
Engineering Method of Prediction of Plume Path of Air Launched Missile
Get PDFSeparation dynamics study of an air-launched missile is a paramount task for ensuring the safety of launch aircraft. The study should certify that there is absolute absence of any physical interference of missile with the aircraft at any circumstance. It is also important to ensure that the interference of rocket motor plume of hot-launched missile does not have any significant effect on the structure, on board electronic components and sensitive parts of the aircraft. The plume ingestion into the aircraft intake is a critical problem which endangers the safety of the aircraft. Therefore, the prediction of plume path of hot-launched missile is a significant part of separation dynamics study. An engineering approach based on a particle tracking method was followed in predicting the plume path in the present work. Further, the method is modified using reverse particle tracking method to make it more efficient. The method is applied in predicting plume path for an air-to air-missile and is found that this approach gives reasonably accurate plume path with minimum computational requirements
Rolling Moment of Slender Body at High Incidence for Air to Air Missile Rocket Applications
Get PDFMeasurements of moments were carried out on a slender body having a pointed forebody at lower velocities. The slender body had an ogive nose shape and an overall length to diameter ratio of 16. The angle of incidence was varied from low to moderate angles of attack in the pitch plane. The main objective of the present investigation was to measure the rolling moments on the slender body with and without the control technique. The side force was reduced using a rectangular cross-sectioned ringplaced suitably on the body, however, the slender body was found to experience rolling moments which may be catastrophic
Performance Improvement of Electro Optic Search and Track System for Maritime Surveillance
Get PDFSurveillance of maritime domain is absolutely vital to ensure an appropriate response against any adverse situation relating to maritime safety or security. Electro-optic search and track (EOST) system plays a vital role by providing independent search and track of potential targets in marine environment. EOST provides real-time images of objects with details, required to neutralise threats. At long range, detection and tracking capability of EOST degrades due to uncertainty in target signatures under cluttered scenario. Image quality can be improved by using suitable sensors and enhancement using the target/background signature knowledge. Robust tracking of object can be achieved by optimising the performance parameters of tracker. In the present work, improvement in the performance of EOST subsystems such as sensor, video processor and video tracker are discussed. To improve EOST performance in terms of detection and tracking, sensor selection criterion and various real time image processing techniques and their selection criteria for maritime applications have been also discussed. Resultant improvement in the quality of image recorded under marine environment has been presented
Modelling and Simulation of Cognitive Electronic Attack under the Condition of System of systems Combat
Get PDFFrom the height of system-of-systems combat and operational perspective, the operations of cognitive electronic warfare (CEW) was analysed, and its main process and links were described. Secondly, the jamming effectiveness evaluation (JEE) model of cognitive electronic attack (CEA) operations was established based on the interference side, in which the change of threat degree was used as the measure index of jamming effectiveness. Then, based on the Q-learning model, an intelligent countermeasure strategy generation (ICSG) model was established, and the main steps in the model were given. Finally, on the basis the JEE model and the ICSG model, the simulation experiment was carried out for CEA operations. The result showed that combining the JEE model with the ICSG model can express the main process of the operations of CEW, as well as proved the validity of these models
Location Size and Orientation Effect of Semi elliptical Surface Crack on the Fracture of a Type 3 Composite Pressure Vessel using J integral Method
Get PDFIn this study, structural design and analysis of a type-3 composite over wrapped pressure vessel used in a military satellite propulsion system is presented. The aim is to design a composite tank lighter than all metal fuel tanks having the same volume. Moreover, necessary design stages have been revealed for similar composite over wrapped pressure vessels. ANSYS® is used to perform the stress-strain analysis of both metal and composite parts, to determine the optimum winding angle, tank Autofrettage and fracture characteristic for the metal liner considering the crack morphology. Tsai-Hill, Tsai-Wu and Hashin theories have been implemented to investigate the various failure modes of the composite vessel. Location, size and orientation angle of semi-elliptical surface crack has a pronounced effect on fracture characteristic of the liner. In fracture investigation J-integral method is used. It is foreseen that even in the most critical crack, the crack will not propagate and there will be no burst in the tank for proposed loading conditions. Numerical results are good agreement with the experimental results
Study of Vibration Behaviour of Stiffened Polymer Composite Shells for Underwater Structural Applications
Get PDFThis paper presents vibration behavior of ring stiffened polymer composite thick shells used for underwater structures. Filament wound shells stiffened with internal and external rings and with hemispherical ends were tested for vibration in air and water in free-free boundary condition using roving hammer and fixed response method. Modal testing of the shells was performed under hydrostatic loading in a custom designed buckling tester for determining natural frequency at higher sea depths. Accelerometer was mounted on the inner surface of the shell. It was excited using a plumbob, rope and pulley arrangement. Experimental results were validated by modal analysis using Hyperworks and ANSYS. Vibration behavior in water was simulated by Fluid structure interaction approach. Experimental first natural frequency in water was lesser than that in air. With increase in hydrostatic pressure, the shell showed moderate variation in natural frequency. The experimental and numerical results of natural frequency and mode shapes were in good agreement with each other. Natural frequencies were lower in long and thick shells
Numerical Study of the Effect of Wing Position on Autonomous Underwater Glider
Get PDF Autonomous underwater gliders are a class of underwater vehicles that transit without the help of a conventional propeller. The vehicle uses a buoyancy engine to vary its buoyancy and with the help of the wings attached executes its motion. The hydrodynamic characteristics of the vehicle affect the longitudinal and turning motion. This paper discusses the effect of the wing’s position on the vehicle’s lift and drag characteristics. Computational fluid dynamics (CFD) tool is used to estimate the lift, drag, and pitching moment coefficients of the vehicle. The numerical methodology is validated using flow over NACA0012 wing results for low Reynolds numbers, and the results of CFD are discussed for possible application in estimation of glider motion
Creep Response of Rotating Composite Discs having Exponential Hyperbolic Linear and Constant Thickness Profiles
Get PDFThe study compares the steady state creep response of rotating Al-SiC discs having constant, linear, hyperbolic and exponential thickness with different thickness profiles. All the discs are assumed to have equal volume with the same average thickness. The creep behaviour of the disc material is described by threshold stress based law while the yielding is assumed to follow Tresca criterion. The variable thickness disc is observed to have superior creep response, expressed in terms of stresses and strain rates, to a constant thickness disc. Amongst variable thickness discs, the creep response is observed to be superior for linear thickness disc, when the inner thickness of all the discs is kept the same. However, for the same outer thickness, the disc having hyperbolic thickness profile exhibits the best creep response