| 1. |
- Ghai, Viney, 1989, et al.
(författare)
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Experimental investigation of single spark μ-EDM using electrodes fabricated with μ-turning process
- 2024
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Ingår i: Sadhana - Academy Proceedings in Engineering Sciences. - 0256-2499. ; 49:2
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Tidskriftsartikel (refereegranskat)abstract
- Micro electrical discharge machining (μ-EDM) stands out as a widely employed non-traditional machining process with diverse applications in microfluidics, electronics, medical, aeronautics, and the automotive industry. This study is dedicated to the exploration of the single spark μ-EDM process utilizing a titanium tool electrode fabricated using a μm-turning process. Intriguingly, it is established that achieving a single spark necessitates a minimum tool diameter of 8 μm. Further, the effect of critical parameters such as voltage and capacitance on material removal rate (MRR), tool wear rate (TWR), as well as the shape and size of the resultant craters is investigated. A 7 μm tool electrode when subjected to a voltage of 100 V and a capacitance of 33 pF manifests a remarkably refined surface finish, demonstrating controlled erosion on the workpiece surface. The study also indicates that MRR and TWR vary exponentially with supplied discharge energy. This comprehensive analysis not only identifies optimal conditions for μm turning during tool fabrication but also elucidates the prerequisites for generating a controlled single spark during workpiece erosion. In essence, the findings presented here contribute valuable insights to the advancement of precision μ-EDM processes.
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| 2. |
- Goyal, Rahul, et al.
(författare)
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Transient pressure measurements at part load operating condition of a high head model Francis turbine
- 2016
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Ingår i: Sadhana (Bangalore). - : Springer Science and Business Media LLC. - 0256-2499 .- 0973-7677. ; 41:11, s. 1311-1320
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Tidskriftsartikel (refereegranskat)abstract
- Hydraulic turbines are operating at part load conditions depending on availability of hydraulic energy or to meet the grid requirements. The turbine experiences more fatigue during the part load operating conditions due to flow phenomena such as vortex breakdown in the draft tube and flow instability in the runner. The present paper focuses on the investigation of a high head model Francis turbine operating at 50% load. Pressure measurements have been carried out experimentally on a model Francis turbine. Total six pressure sensors were mounted inside the turbine and other two pressure sensors were mounted at the turbine inlet pipe. It is observed that the turbine experiences significant pressure fluctuations at the vaneless space and the runner. Moreover, a standing wave is observed between the pressure tank outlet and the turbine inlet. Analysis of the data acquired by the pressure sensors mounted in the draft tube showed the presence of vortex breakdown co-rotating with the runner. The detailed analysis showed the rotating and plunging components of the vortex breakdown. The influence of the rotating component was observed in the entire hydraulic circuit including distributor and turbine inlet but not the plunging one
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| 3. |
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| 4. |
- Parasuram, I. V. L. N., et al.
(författare)
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Investigating wake structures in flow past oscillating cylinder using proper orthogonal decomposition
- 2024
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Ingår i: Sadhana (Bangalore). - : Springer Nature. - 0256-2499 .- 0973-7677. ; 49:1
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Tidskriftsartikel (refereegranskat)abstract
- The present study investigates unsteady wake dynamics in flow past an oscillating cylinder. A two-dimensional computational analysis is undertaken for flow past a sinusoidally oscillating cylinder. Operating parameters like Reynolds number, forcing frequency, amplitude, and wavelength are systematically varied, and their effect on wake dynamics is investigated. Lift and drag coefficients are plotted with cylinder position to characterize the flow. The flow field is analyzed using Proper Orthogonal Decomposition (POD). POD mode shapes and Power Spectral Density (PSD) plots characterize the flow response to cylinder oscillations. The effect of frequency ratio is examined in achieving synchronized vortex shedding. Previous studies focus on two extremes- the cylinder is either stationary or oscillating with perfect phase-locking. Flow past an oscillating cylinder where Karman and forcing frequencies compete for dominance is rarely reported. This paper considers such a scenario and demonstrates how POD can identify coherent structures, their significance, and associated frequencies. Further, non-symmetric vortex shedding, which is not a common observation, is captured and discussed. Large amplitude and large wavelength regimes are investigated, which remained unexplored in previous research. Coherent structures associated with those regimes are identified.
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| 5. |
- Sukumaran Nair, A., et al.
(författare)
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TaskMUSTER : a comprehensive analysis of task parameters for mixed criticality automotive systems
- 2022
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Ingår i: Sadhana (Bangalore). - : Springer. - 0256-2499 .- 0973-7677. ; 47:1
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Tidskriftsartikel (refereegranskat)abstract
- Automotive computing platforms are becoming complex and steadily being transformed into mixed criticality systems (MCS) with connectivity to the user, infrastructure and other vehicles. Due to the safety critical and real time nature of such systems, this transition emphasizes careful selection of task models, task scheduling mechanisms and software development practices to ensure predictability. Though there exists a wealth of research results on MCS, often the non-uniform descriptions and non-comprehensive nature of task parameters become hindrances to the designers and researchers, thus limiting their wider applicability. In this context, we carry out a comprehensive analysis of task parameters for MCS and propose a task parameter aggregator called TaskMUSTER with focus on automotive domain, specifically on the controlling domain software applications like power steering, brake systems and power train. TaskMSUTER aims to provide a unified view of various task model parameters in terms of important attributes related to resource & communication, energy, fault-tolerance, mode change, OS overheads and parallel processing. This work also provides Backus-Naur form grammar and railroad diagram of TaskMUSTER. The usability analysis of TaskMUSTER and comparisons with well-known task model propositions are carried out using an automotive wake-up controller task set. The results justify the suitability of TaskMUSTER for designing safety certifiable automotive MCS. Overall, TaskMUSTER acts as a comprehensive and design friendly handbook for researchers and designers in the mixed criticality automotive controlling domain.
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