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Kumar D.A.,Government Arts College | Venugopalan S.R.,Aeronautical Development Agency
International Journal of Advanced Intelligence Paradigms | Year: 2017

Increased use of computer networks, internet and online transactions pose higher risk of intrusions and protecting the information from the hackers/intruders is a new area in computers and network security. The major factors which affect intrusion detection are the system's detection rate and time required to detect intrusions. Many researchers have focused in this area and have used data mining techniques for detecting the intrusions. This paper proposes to classify the dataset initially based on 'protocol type' feature and the performance improvements over traditional way of considering the full data without initial classification. This paper does not advocate any techniques or algorithms, but establishes the fact that by splitting the dataset on Protocol Type feature enhances performance with respect to detection rate and time to build model for intrusion detection. In this study, the well-known KDD Cup 99 intrusion dataset has been tested with the proposed approach. The computational study reveals that the initial classification based on protocol type' attribute increases the performance with respect to rate of detection and time to build model. © 2017 Inderscience Enterprises Ltd.

Chennu R.,Aeronautical Development Agency
International Journal of Numerical Methods for Heat and Fluid Flow | Year: 2016

Purpose - The purpose of this paper is to carry out numerical modeling of single-blow transient analysis using FLUENT porous media model for estimation of heat transfer and pressure drop characteristics of offset and wavy fins. Design/methodology/approach - A computational fluid dynamics program FLUENT has been used to predict the design data in terms of j and f factors for plate-fin heat exchanger wavy and offset strip fins, which are widely used in aerospace applications. Findings - The suitable design data in terms of Colburn j and Fanning friction f factors is generated and presented correlations for wavy fins covering the laminar, transition and turbulent flow regimes. Originality/value - The correlations for the friction factor f and Colburn factor j have been found to be good by comparing with other references. The correlations can be used by the heat exchanger designers and can reduce the number of tests and modification of the prototype to a minimum for similar applications and types of fins. © Emerald Group Publishing Limited.

Chennu R.,Aeronautical Development Agency | Paturu P.,National Institute of Technology Warangal
International Journal of Numerical Methods for Heat and Fluid Flow | Year: 2011

Purpose - In aerospace applications, due to the severe limitations on the weight and space envelope, it is mandatory to use high performance compact heat exchangers (CHEs) for enhancing the heat transfer rate. The most popularly used ones in CHEs are the plain fins, offset strip fins (OSFs), louvered fins and wavy fins. Amongst these fin types, wavy and offset fins assume a lot of importance due to their enhanced thermo-hydraulic performance. The purpose of this paper is to investigate the influence of geometrical fin parameters, in addition to Reynolds number, on the thermo-hydraulic performance of OSFs. Design/methodology/approach - A computational fluid dynamics approach is used to conduct a number of numerical experiments for determination of thermo-hydraulic performance of OSFs considering the various geometrical parameters, which are generally used in the aerospace industry. These investigations include the study of flow pattern for laminar, transition and turbulent regions. Studies are conducted with different fin geometries and comparisons are made with available data in open literature. Finally, the generalized correlations are developed for OSFs taking all geometrical parameters into account for the entire range of operations of the aerospace industry covering laminar, transition and turbulent regions. In addition, the effects of various geometrical parameters are presented as parametric studies. Findings - Thermo-hydraulic design of CHEs is strongly dependent upon the predicted/measured dimensionless performance (Colburn factor "j" and Fanning friction "f" vs Reynolds number Re) of heat transfer surfaces. Several types of OSFs used in the compact plate-fin heat exchangers are analyzed numerically. Research limitations/implications - The present numerical analysis is carried out for "air" media and hence these results may not be accurate for other fluids with large variations of Prandtl numbers. Practical implications - In open literature, these fins are generally evaluated as a function of Reynolds number experimentally, which are expensive. However, their performance will also depend to some extent on geometrical parameters such as fin thickness, fin spacing, offset fin length and fin height. Originality/value - This numerical estimation can reduce the number of tests/experiments to a minimum for similar applications. © Emerald Group Publishing Limited.

Sheik Ismail L.,Aeronautical Development Agency | Velraj R.,Anna University | Ranganayakulu C.,Aeronautical Development Agency
Renewable and Sustainable Energy Reviews | Year: 2010

Renewable energy sources like solar energy, wind energy, etc. are profusely available without any limitation. Heat exchanger is a device to transfer the energy from one fluid to other fluid for many applications in buildings, industries and automotives. The optimum design of heat exchanger for minimum pumping power (i.e., minimum pressure drop) and efficient heat transfer is a great challenge in terms of energy savings point of view. This review focuses on the research and developments of compact offset and wavy plate-fin heat exchangers. The review is summarized under three major sections. They are offset fin characteristics, wavy fin characteristics and non-uniformity of the inlet fluid flow. The various research aspects relating to internal single phase flow studied in offset and wavy fins by the researchers are compared and summarized. Further, the works done on the non-uniformity of this fluid flow at the inlet of the compact heat exchangers are addressed and the methods available to minimize these effects are compared. © 2009.

Angappan M.,Aeronautical Development Agency | Sampath V.,Indian Institute of Technology Madras | Ashok B.,Aeronautical Development Agency | Deepkumar V.P.,Aeronautical Development Agency
Materials and Design | Year: 2011

The influence of retrogression and re-aging treatment (RRA) on short transverse tensile properties of 7010 aluminium alloy extrusions was studied. The short transverse ductility of extrusions, which was much lower in the T6 condition, was improved to the optimum level after retrogression and re-aging treatment. It is found that short transverse ductility is influenced by the nature of precipitate particles located along the grain boundary. It is observed that coarsening of the grain boundary precipitates and its copper enrichment that occurs during RRA are found to be the factors responsible for improvement in stress corrosion cracking (SCC) resistance. The optimum retrogression and re-aging schedule is established that gives rise to the best combination of strength, ductility and SCC resistance. © 2011 Elsevier Ltd.

Varuvel A.G.,Aeronautical Development Agency
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2015

Loss of control of aircraft is one of the catastrophic safety critical events in the aerospace domain, which results usually into risks of loss of human lives and/or environmental hazards. Triggering of this undesired event could be at any level of hardware and/or software in the digital fly-by-wire fighter aircraft. The contributing factors for this undesirable event and the interrelationships among the basic events are to be carefully accounted, while estimating the loss of control of the fighter aircraft, probabilistically. Components which have the potential to cause failures are required to be treated carefully, by properly considering the failure modes of those components. This paper brings out, the data driven methodology to estimate the probability of control of the aircraft considering all the interdependent components along with the associated failure modes, which have the potential to trigger the occurrence of the undesired event-‘Loss of Control of Aircraft’. The approach presented here would serve as a guideline for estimating the PLOC of any types of aircraft. © Springer International Publishing Switzerland 2015.

Ranganayakulu C.,Aeronautical Development Agency | Kabelac S.,Leibniz University of Hanover
Journal of Heat Transfer | Year: 2015

This paper presents experimental results on boiling heat transfer of R134a in a compact plate fin heat exchanger. The exchanger is made of aluminum and has high density offset fins (30 fins/in.). Such heat exchangers are widely used in air separation industry and aerospace applications because of their high compactness and low weight. The test heat exchanger is attached to a vapor cycle refrigeration basic module to study the effects of boiling phenomena and its influence on performance as there is limited information available for this type of fins. This in turn allows for discussion on boiling mechanism of R134a inside the fins using the water circuit on the other side of the test heat exchanger. The water side single phase heat transfer coefficient (Colburn j factor) is calculated using the cfd tool fluent and validated with available open literature. The results are presented for heat fluxes up to 5500 W/m2 and mass fluxes up to 20 kg/(m2s) with water side flow rate varying from 0.033 to 0.17 kg/s for water temperatures of 10, 15, 20, 25, and 30 °C. Copyright © 2015 by ASME.

Srinivasan P.,Aeronautical Development Agency | Joshi A.,Indian Institute of Technology Bombay
AIAA Modeling and Simulation Technologies Conference, 2016 | Year: 2016

The accurate prediction of analytical estimates of servoelastic responses aids greatly in planning an optimal test matrix and reducing actual aircraft test efforts. The present study focuses on achieving improved test-analysis correlation of servoelastic response predictions using optimization methods. Zones for parameter updation are chosen based on test-analysis deviations of modal data and error localization techniques. Multiple optimization functions are set up to simultaneously cover different servoelastic response transfer functions, different modes as well as different aircraft configurations. Critical factors influencing servoelastic response are taken as decision variables and two different sets of multi-objective functions are used, along with genetic algorithms, for carrying out the optimization study. The first set is based on enhanced frequency domain assurance criteria, while the second set is based on test-analysis deviations of peak modal gain amplitudes and natural frequencies. The improvement in servoelastic response predictions using these two methods is presented for a generic flexible aircraft model. These methods are further exemplified and compared by computing servoelastic responses for three different stores mounted under the inboard wing station of the aircraft. Dynamic characteristics of the stores considered in this paper, vary within a range of 15%. It is seen that both methods result in required improvement in servoelastic response predictions. However, the second method is computationally less intensive, though the updation is more local. © 2016 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Sutrakar V.K.,Aeronautical Development Establishment | Sutrakar V.K.,Aeronautical Development Agency
Journal of Physics Condensed Matter | Year: 2014

In this paper, atomistic modeling of L10-TiAl nanowire has been performed utilizing the Embedded Atom Method (EAM) potential under strain-controlled cyclic loading. A nanowire oriented along the <100> axis with a cross-sectional dimension (D) of ∼80 Å with a Length-to-width (L/D) ratio of 10.0 has been considered. Strain-controlled cyclic loading at room temperature has been performed by oscillating the nanowire length dimension sinusoidal with a specific amplitude and period. Tension-compression cyclic loading was employed with zero mean strain. Cyclic loading with percentage strains (%ε) of one to five percent have been considered. It has been observed that the cyclic stress in the nanowire continues to fluctuate during the initial loading cycles. However, once the nanowire becomes stable, a smooth variation of stresses with varying strain has been observed. The cause of initial fluctuations in the nanowire has been studied by varying (a) the amount of load (strain) applied, (b) the nanowire structure during cyclic loading, and (c) the rate at which the load has been applied. It has been identified that the rate of loading could be used for controlling the initial fluctuations of nanowire. Finally, a method for the calculation of cyclic stress versus cyclic strain for nanowires has been proposed. A cyclic stress versus cyclic strain curve has been plotted for a given L/D = 10 and a period of 10 ps. Results show that the TiAl nanowire is having 3/2 times higher stiffness in tension as compared to compression at a given strain under cyclic loading. © 2014 IOP Publishing Ltd.

Ranganayakulu C.,Aeronautical Development Agency | Luo X.,Leibniz University of Hanover | Kabelac S.,Leibniz University of Hanover
Applied Thermal Engineering | Year: 2016

A single-blow transient test technique is employed to measure the Colburn j factor versus Reynolds number characteristics of high efficiency compact heat exchanger surfaces having offset and wavy fins. Using the experimental data, the NTU values are estimated for 5 types of fins. The measured data is evaluated using the maximum slope method to obtain the corresponding heat transfer coefficient in terms of Colburn j factor, and then is compared with the available correlations of theoretical steady state CFD model. In this analysis, the effects of non-adiabatic side walls and longitudinal heat conduction on the exit fluid temperature response and NTU values are discussed. The test core pressure drops are also measured, and the pressure drop components of entrance, acceleration, core friction and exit losses are compared with the CFD results. © 2016.

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