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Wave Energy Harvesting Turbine: Effect of Hub-To-Tip Profile Modification
P. Madhan Kumar,Paresh Halder,Abdus Samad,Shin Hyung Rhee 한국유체기계학회 2018 International journal of fluid machinery and syste Vol.11 No.1
The present paper investigates the leading edge (LE) undulations of a Wells turbine blade through numerical analysis. The aspiration for this modification came from humpback whales, which have uneven protrusions at the LE of their pectoral flippers. The flippers help whales to maneuver during swimming. The work is performed by using three-dimensional steady, incompressible Reynolds Averaged Navier-Stokes (RANS) equations with turbulent closer model. The LE of the turbine blades is modified with undulations of three different amplitudes: 1mm, 2.5mm, and 4mm. The results show that the undulation changes the turbine performance. The amplitude 2.5mm gives the peak performance. The comparison between blades with different amplitudes and the reference blade has been discussed throughout this study.
Wave Energy Harvesting Turbine: Effect of Hub-To-Tip Profile Modification
Kumar, P. Madhan,Halder, Paresh,Samad, Abdus,Rhee, Shin Hyung Korean Society for Fluid machinery 2018 International journal of fluid machinery and syste Vol.11 No.1
The present paper investigates the leading edge (LE) undulations of a Wells turbine blade through numerical analysis. The aspiration for this modification came from humpback whales, which have uneven protrusions at the LE of their pectoral flippers. The flippers help whales to maneuver during swimming. The work is performed by using three-dimensional steady, incompressible Reynolds Averaged Navier-Stokes (RANS) equations with turbulent closer model. The LE of the turbine blades is modified with undulations of three different amplitudes: 1mm, 2.5mm, and 4mm. The results show that the undulation changes the turbine performance. The amplitude 2.5mm gives the peak performance. The comparison between blades with different amplitudes and the reference blade has been discussed throughout this study.
Synthesis and Electrical Characterization of Lead‑Free Electronic Material: Bi(Co2/3Nb1/3)O3
S. Halder,S. Bhuyan1,R. N. P. Choudhary 한국전기전자재료학회 2019 Transactions on Electrical and Electronic Material Vol.20 No.1
A lead-free electronic compound with chemical composition Bi(Co2/3Nb1/3)O3 has been synthesized via classical solid state reaction based ceramic technology. The structure of the compound as well as the frequency and temperature field dependent resistive, conductive and dielectric properties of the specimen have been examined. The room temperature X-ray diffraction analysis exhibits the formation of the sample in orthorhombic crystal symmetry. The observed dielectric constant and tangent loss characteristics substantiate the prepared compound as a dielectric. The impedance spectra confirms the presence of negative temperature coefficient of resistance behaviour, grain and grain boundary effect in the fabricated compound. The compound modulus spectrum shows that the temperature dependent conductivity relaxation phenomenon is of nonexponential-type. The illustrated important characteristics props up the material for different device applications.
S. Das,S. Sanyal,P. Halder,A. Varma,Y. Ravi Kumar,S. Mandal 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.8
In this study, the oxidation response of a T91 steel in dry air environment has been investigated by performing cyclic oxidationtests at 873, 973 and 1073 K for a total duration of 1000 h with intermediate intervals. The temperature range for thisstudy is chosen to be higher than the operating temperature range of the alloy to accelerate the oxidation kinetics. Developinga comprehensive understanding of the mechanisms and kinetics involved at such accelerated oxidation environmentswould help to formulate better strategies for countering oxidation related failure events. The results of this study showedthat the oxidation rate is greatly influenced by temperature as well as exposure time, and follows a near-parabolic rate law. Characterization of the oxide scales revealed formation of dual oxide layers where the inner layer is primarily rich in Feand Cr, and the outer layer in Fe only. At 1073 K, formation of cracks can be observed in the oxide scales after 24 h, whichbecame more severe after 1000 h. The oxidation kinetics, when fitted to an Arrhenius type equation, can be associated withactivation energy (Q) and parabolic rate constant (kp) values. The Q values lie within 104–109 kJ/mol, whereas the kp valuesincrease with temperature due to increase in the reaction rate. The kinetic equation developed based on the Q and kp valuescan be used to predict the thickness (inner, outer and overall) of the oxide scales in T91 steel at any temperature and timewithin the studied ranges.
Palash Das,Sanjay Kumar Jana,Nripendra N. Halder,S. Mallik,S. S. Mahato,A. K. Panda,Peter P. Chow,Dhrubes Biswas 대한금속·재료학회 2018 ELECTRONIC MATERIALS LETTERS Vol.14 No.6
In this letter, a standard deviation based optimization technique has been applied on High Resolution X-ray Diff raction symmetricand asymmetric scan results to accurately determine the Aluminum molar fraction and lattice relaxation of MolecularBeam Epitaxy grown compositionally graded Aluminum Gallium Nitride (AlGaN)/Aluminum Nitride/Gallium Nitride(GaN) heterostructures. Mathews–Blakeslee critical thickness model has been applied in an alternative way to determinethe partially relaxed AlGaN epilayer thicknesses. The coupling coeffi cient determination has been presented in a diff erentperspective involving sample tilt method by off set between the asymmetric planes of GaN and AlGaN. Sample tilt is furtherincreased to determine mosaic tilt ranging between 0.01° and 0.1°.