Articles written in Sadhana

    • Controlling chaotic dynamics of periodically forced spheroids in simple shear flow: Results for an example of a potential application

      C V Anil Kumar T R Ramamohan

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      Recently, we studied the technologically important problem of periodically forced spheroids in simple shear flow and demonstrated the existence of chaotic parametric regimes. Our results indicated a strong dependence of the solutions obtained on the aspect ratio of the spheroids, which can be used to separate particles from a suspension. In this paper we demonstrate that controlling the chaotic dynamics of periodically forced particles by a suitably engineered novel control technique, which needs little information about the system and is easy to implement, leads to the possibility of better separation. Utilizing the flexibility of controlling chaotic dynamics in a desired orbit irrespective of initial state, we show that it is theoretically possible to separate particles much more efficiently than otherwise from a suspension of particles having different shapes but similar sizes especially for particles of aspect ratiore>1.0. The strong dependence of the controlled orbit on the aspect ratio of the particles may have many applications such as in the development of computer-controlled intelligent rheology. The results suggest that control of chaos as discussed in this work may also have many applications.

    • AI-based adaptive control and design of autopilot system for nonlinear UAV

      Anil Kumar Yadav Prerna Gaur

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      The objective of this paper is to design an autopilot system for unmanned aerial vehicle (UAV) to control the speed and altitude using electronic throttle control system (ETCS) and elevator, respectively. A DC servo motor is used for designing of ETCS to control the throttle position for appropriate amount of air mass flow. Artificial Intelligence (AI)-based controllers such as fuzzy logic PD, fuzzy logic PD + I, self-tuning fuzzy logic PID (STF-PID) controller and fuzzy logic-based sliding mode adaptive controller (FLSMAC) are designed for stable autopilot system and are compared with conventional PI controller. The target of throttle, speed and altitude controls are to achieve a wide range of air speed, improved energy efficiency and fuel economy with reduced pollutant emission. The energy efficiency using specific energy rate per velocity of UAV is also presented in this paper.

    • Partial index replicated and distributed scheme for full-text search on wireless broadcast

      Vikas Goel Anil Kumar Ahlawat M N Gupta

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      Information indexing is an extremely useful solution for wireless broadcast channels, because of its energy efficiency. Full text search on the wireless broadcast stream is another popular type of information dissemination access. This research paper discusses indexing schemes for full text search information, using two levels of structure B+ tree and inverted list. The partial replication in the B+ tree indexing scheme is proposed to extend the existing full text search indexing scheme. In the proposed work, the index information of B+ tree has been cut to reduce access time and tuning time: metrics for evaluating indexing schemes. The replication in B+ tree may be done up to a certain level of the indexed informat+ion (Data). Evaluation and analysis of the proposed indexing scheme show an excellent improvement over existing indexing schemes.

    • Auxiliary subsystems of a General-Purpose IGBT Stack for high-performance laboratory power converters


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      A PWM converter is the prime component in many power electronic applications such as static UPS, electric motor drives, power quality conditioners and renewable-energy-based power generation systems. While there are a number of computer simulation tools available today for studying power electronic systems,the value added by the experience of building a power converter and controlling it to function as desired is unparalleled. A student, in the process, not only understands power electronic concepts better, but also gains insights into other essential engineering aspects of auxiliary subsystems such as start-up, sensing, protection, circuit layout design, mechanical arrangement and system integration. Higher levels of protection features are critical for the converters used in a laboratory environment, as advanced protection schemes could prevent unanticipated failures occurring during the course of research. This paper presents a laboratory-built General-Purpose IGBT Stack (GPIS), which facilitates students to practically realize different power converter topologies. Essential subsystems for a complete power converter system is presented covering details of semiconductor device driving, sensing circuit, protection mechanism, system start-up, relaying and critical PCB layout design, followed by a brief comparison to commercially available IGBT stacks. The results show the high performance that can be obtained by the GPIS converter.

    • Design and comparative study of discrete and module-based IGBT power converters


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      This paper discusses concepts of a 20 kVA power converter design and key differences between discrete IGBT and module-based design approaches. Module-based power converters have been typically employed in academic and research institutes for power levels of 10 kVA and more. However, with advancement in IGBT technologies and the growing need to minimize system size and weight, designs based on discrete devices are now an attractive alternative for such power levels. A simple procedure is presented for power converter design that includes power loss evaluation, heat-sink thermal characterization, thermal model of overall system and sizing of DC link capacitor. Using the same, a state-of-the-art discrete device and modulebased power converters are designed. A comparison is subsequently made, where it is shown that discrete approach yields a compact and economic design up to a power level of 20 kVA. A key objective of this work is to lay emphasis on laboratory design of power converters. This enables a graduate level student to build a converter from start and in the process gain insights into the underlying engineering design aspects.

    • Numerical investigation of single bubble dynamics in liquid sodium pool


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      The single gas bubble rise dynamics in liquid sodium/sodium-potassium alloy (NaK) pool due to entrainment of argon cover gas/non-condensable fission gas (xenon) have received considerable attention in the safe operation of Sodium-cooled Fast Reactor (SFR). Numerical simulation of single bubble dynamics in liquid sodium/NaK pool is an essential intermediate step for the evaluation of rise velocity and shape changes, which are of utmost importance in areas of reactor safety concerned with source term evaluation and cover gas purification. The interFoam solver of OpenFOAM package is used to evaluate inert gas bubble rise dynamics in stagnant liquid metal pool of sodium and NaK. The governing equations are discretized and solved using the Volume of Fluid (VOF) based solver available in OpenFOAM with appropriate initial and boundary conditions.The VOF module of the solver is validated against numerical benchmark data and experimental results available in literature. The bubble dynamics in liquid sodium/NaK pool are studied in terms of trajectory, shape and risevelocity for diameters ranging from 10 to 20 mm, domain aspect ratios and for different gas-liquid systems. The study shows that the bubble rise velocity increases with diameter for liquid sodium systems. The rise behavior ofsingle inert gas bubble in liquid water and sodium pool are compared. The study supports the use of air-water system as a simulant for studying bubble dynamics in liquid sodium systems as suggested by other researchers. The study is very useful and forms an intermediate step towards the development of an OpenFOAM basedcomputational framework to analyze heat and mass transfer from single bubble rising in liquid sodium pool for reactor safety studies.

    • Performance monitoring of wind turbines using advanced statistical methods


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      Estimation of wind power generation for grid interface helps in calculation of the annual energy production, which maintains the balance between electricity production and its consumption. For this purpose, accurate wind speed forecasting plays an important role. In this paper, linear statistical predictive models such asautoregressive integrated moving average (ARIMA), generalized autoregressive score (GAS) model and a GAS model with exogenous variable x (GASX) have been applied for accurate wind speed forecasting. Along with this, a non-linear statistical predictive modelling technique called non-linear GASX (NLGASX) has been proposed and applied to model non-linear time-series data. Furthermore, the proposed NLGASX model is optimized using modelling techniques based on neural networks, namely Sigmoid, TANH, Softmax and RELU. The proposed optimized NLGASX model performs far better as compared with other models. Wind speed is also used as an input to wind power curve model for predicting the wind power. According to the predicted wind power the annual energy has been calculated.

    • Optimal Assembly Sequence generation through computational approach


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      Optimal assembly sequence (OAS) is always an interesting aspect for an industrial engineer to minimize assembly time and cost, which gives number of assembly levels and sequence of assembly operations. An assembly sequence with more number of parallel possible stable sub-assemblies significantly reduces theoverall assembly time for large scale products. Finding such optimal sequences from huge set of all assembly sequences (SAAS) is challenging due to involvement of multiple assembly feasibility validation criteria namely; assembly coherence, geometric feasibility, part stability and mechanical feasibility. In this paper, an efficient computational method is proposed to generate optimal assembly sequences. The method considers extended assembly stability relations to identify stable sub-assemblies for parallel execution. The method is proven ingenerating optimal solutions for any given product effectively. The method is well discussed and compared with prominent computational methods with suitable product illustrations.

    • Impact of pile foundations adjacent to tunnels in sandy stratum


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      In recent years, with rapid urbanization and construction of underground pipeline facilities for the transmission of electricity, supply of water, sewage disposal or provision of facilities like telephone lines, gas pipe lines, etc., it is highly probable to encounter an existing pipeline system in the vicinity of a proposed foundation of a structure. Hence, design and construction of new foundation structure near the existing subsurface pipeline system is imperative and should be addressed for keeping either a minimum safe clearance between tunnel/buried pipe and pile without compromising the capacity of pile or estimating the reducedcapacity due to existing nearby pipeline or tunnel, which is an important aspect in the analysis and design of pile foundation. Present study demonstrates a model and numerical study of the behaviour of a single pile in the vicinity of existing tunnel/buried pipe in a cohesionless soil. During experimental work, a small scale pile model was tested for its load–settlement behaviour without and with the existence of buried PVC pipe modelled as a tunnel in the vicinity near the shaft. The complete experimental set-up consisted of a steel box filled with sand attwo different relative density values and vertical concentric load was applied on the model pile through a hydraulic jack and reaction frame arrangement connected with a proving ring. Results of pile loading test have been provided, which demonstrate the tunnel–pile interaction problem effect on the pile capacity, and it was also numerically verified using commercially available finite-element tool. With due verification, parametric study is performed, through finite-element analysis, by varying the range of input parameters such as unit weight, internal friction angle, diameter of pile and elastic modulus of pile material to the soil modulus ratio. Based on the results of numerical analysis in terms of load–settlement curves, it is noted that there is 15–20% reduction in the pile capacity of a single pile to be installed in cohesionless soil in the vicinity of the existing buried pipe ortunnel, which depends on the geometries of the pile and tunnel construction, properties of the in situ soil and zones of influence due to relative stiffness of soil and pipe materials.

    • Selection of teak sawdust polypropylene composite’s composition for outdoor applications using TOPSIS analysis


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      Selection of a material for their end use in engineering applications depends on the properties of materials. In this paper, physical and mechanical properties of teak sawdust-polypropylene composite are evaluated and most suitable composition for outdoor applications have been determined by using TOPSIStechnique of optimization. Virgin and recycled polypropylene are mixed with teak sawdust to fabricate the composite with and without maleated polypropylene (MAPP) using compression molding method. TOPSIS technique of optimization involves prioritizing the performance indicators. Important properties such as tensile strength, flexural strength, impact strength, hardness, melt flow index, water absorption and thickness of swell are selected for the study. The composition 50% recycled polypropylene, 45% wood sawdust and 5% MAPP byweight is found to be most suitable for outdoor applications

    • Optimized hybrid learning for multi disease prediction enabled by lion with butterfly optimization algorithm


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      As there is a rapid growth in healthcare systems and biomedical data. Machine learning algorithms are utilized in many researches for predicting the risk of the diseases. The major intuition of the present paper is to plan for a novel methodology for multi-disease prediction using deep learning. The overall prediction methodology involves several steps such as ‘‘(a) Data Acquisition, (b) Optimal Feature selection, (c) Statistical eature Extraction, and (d) prediction’’. In the initial step, the medical datasets of diverse diseases is gathered from multiple benchmark sources. Further, the optimal feature selection is applied to the available set of attributes. This is accomplished by hybridizing two meta-heuristic algorithms such as Lion Algorithm (LA), and Butterfly Optimization Algorithm (BOA). In these prediction algorithms, the hidden neuron count of NN andDBN is finely tuned or optimized by the same hybrid Lion-based BOA (L-BOA). The experimental evaluation of various medical datasets validates that the prediction rate of the developed model outperforms several traditional methods.

    • Investigations on the interaction of surface radiation and turbulent natural convection in enclosures with multiple positions of source and sink


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      A numerical investigation is performed for heat transfer phenomena occurring in enclosures with different aspect ratios, emissivities and Rayleigh numbers. Interaction of surface radiation and turbulent natural convection of differentially heated enclosures with different positions of heat source and sink has been assessed systematically. The mass, momentum and energy equations have been solved in two-dimensional cartesian coordinates. The turbulence has been modeled using k - ε model. The simulations have been performed on rectangular enclosures with different aspect ratios (0.5, 1, 1.5 and 2) filled with air having Prandtl number 0.7. Surface to Surface radiation model has been incorporated to study the effect of surface radiation on the heat transfer characteristics. The results have been presented in terms of Nusselt number, isotherms and streamlines for various cases. It is concluded that the results can provide insight when designing enclosures for complex engineering applications involving turbulent conditions.

    • A multi-layered disassembly sequence planning method to support decision making in de-manufacturing


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      End of Life (EoL) products management through crude recycling methods and direct shredding causes severe threat to environment by different kinds of pollution. The environmental benefits such as reduced CO2 emissions observed through recycling are mitigated by the direct release of toxic gases. De-manufacturing through systematic disassembly operations can reduce environmental damage but it requires more input cost to work within the threshold limit value (TLV). Complete disassembly sequence planning (CDSP) methods are not given importance in de-manufacturing objectives, which produce non-optimalsolutions. The objective of present work is to produce an optimal solution to extract valuable materials from the EoL products while separating the toxic elements within TLV. A multi-layered method has been proposed that consists of five different layers, namely data input layer, application layer, modification layer, implementation layer and performance layer. It requires product bill of materials (BOM) and disassembly attributes such as liaison, geometric feasibility and stability as input from the user and generates an optimal solution bysuggesting permissible operations to work within TLV. The proposed method has been applied on a case study and workability at producing practically feasible optimal solution has been confirmed. The effectiveness in working has been evaluated by comparing to the existing DSP methods. The proposed method can be used as a tool to achieve maximum profits through systematic disassembly operations within TLV by supplying essential information.

    • Thermodynamic analysis of sensible heat storage based double pass hybrid solar air heater with and without reflector


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      Solar air heater or solar heating system is a very useful solar thermal product used for multiple purposes such as drying, space heating, desalination, and various industrial applications for low temperature. In this communication, a comprehensive study on the energy-exergy analysis of sensible heat storage based on double pass solar air heater with and without the reflector. System is manufactured with locally available materials. Heat storage material (Metco material and aluminium scrap mixture) was used under the bottom layer.Three cases of experiments were planned, namely natural mode (case 1), double pass solar heater (case 2) and double pass solar air heater with reflector (case 3). Case 3 shows the superior thermal performance as compared to case 1 and 2. The outlet temperature varies from 36 to 60°C; 35 to 58.20°C and 38.5° to 73.2°C in Cases 1, 2 and 3, respectively. This was mainly due to the application of the reflector. It provided additional input energy to the solar air heater.

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