Now showing 1 - 10 of 43
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    Compact Wave Powered Desalination Unit
    (01-01-2022)
    Rajagopalan, Krishnakumar
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    Cross, Patrick
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    Ulm, Nicholas
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    Ravikumar, Suchithra
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    Das, Tapas
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    Prabhu, Mahendra
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    The paper highlights the collaborative research between University of Hawaii and the Indian Institute of Technology, Madras, to move forward the design of a compact wave powered desalination unit. Detailed hydrodynamic optimization is undertaken to optimize the weight, volume and overall performance of the unit. A fully coupled hydrodynamics/filtration model, developed with WEC-Sim software enables quick estimation of desalinated water and brine discharge in frequently observed seas. Several design considerations, that arose during the design stage are presented in this paper. We conclude with estimation of performance-desalinated water and brine discharge-in frequently observed ocean conditions.
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    OPTIMIZING POWER OUTPUT OF A WAVE ENERGY CONVERTER BY EMPLOYING SUPERPOSED HYDRODYNAMIC MODEL
    (01-01-2021)
    Kathyayani, Nandakumar
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    Optimization of wave energy converters (WECs) through robust controls is mandatory to maximize the energy absorption in the face of sea waves’ stochastic nature. Single optimization criterion predicted by linear models is rendered ambiguous when modulated by viscous forces, dominant at the controlled conditions. An efficient hydrodynamic model capable of identifying suitable parameters for nonlinear controller design is desirable but missing. Hence, this paper proposes a superposed hydrodynamic model (SPHM) to optimize the power output of a scaled-down point absorber WEC. Two variants of SPHM are considered to evaluate the differences between linear and nonlinear viscous models. Optimization is guided by a non-predictive latch control strategy. The model is numerically solved using the fourth Runge-Kutta method to obtain the time domain response of buoy. The nonlinear SPHM reveals a new optimization parameter based on the maximum velocity criterion. At off-resonant states, the controller enhances the system power by eleven times.
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    Publication
    Surface curvature effects on performance of a laboratory scale tidal turbine
    (01-01-2018)
    Ai, Kaiming
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    Avital, Eldad
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    Shen, Xiang
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    Venkatesan, Nithya
    This paper presents numerical study of the surface curvature effects on the performance of a 3D lab scale tidal turbine (E387) using Eppler 387 airfoil. The prescribed surface curvature distribution blade design method is used to remove the surface curvature discontinuity of E387 turbine and the redesigned turbine is denoted as A7 turbine. The two turbines are analysed using in-house BEM code and CFD RANS. The performance of E3787 turbine obtained from BEM and RANS match well with the experimental results from reported literature. The A7 turbine has mildly better performance at low tip speed ratio (1-4.25) at which the blade is partly or fully stalled.
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    Numerical analysis of fluid flow through an electrical submersible pump for handling viscous liquid
    (01-01-2016)
    Siddique, Md Hamid
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    Manayilthodiyil, Sanoop
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    Husain, Afzal
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    Kenyery, Frank
    Generally, artificial lifts to pump crude oil having a high viscosity from wellbores using an electrical submersible pump (ESP) are not efficient. The present study consists of a numerical approach to understand the effect of fluid viscosity and surface roughness of the flow passage on the performance of an ESP. A three-dimensional numerical analysis was carried out using Reynolds-averaged Navier-Stokes equations at different off-design conditions. The standard k-ϵ turbulence model was used for the steady incompressible flow. Water and crude oils having different viscosities were used as working fluids and numerical analyses were made by varying surface roughness of the flow passage. Although there was a sharp drop in the efficiency with the increase in surface roughness, but the combined effect of viscosity and surface roughness showed an increase in efficiency up to a certain fluid viscosity.
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    Publication
    Effect of microcylinder and d-cylinder at the leading edge of a wells turbine harvesting wave energy
    (01-01-2021)
    Sadees, P.
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    Kumar, P. Madhan
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    Wells turbine is a self-rectifying axial flow reaction turbine used to harvest energy from the ocean waves. It suffers from a premature stall at higher flow rates. The present study discusses a comparative performance analysis with a turbine-blade leading-edge (LE) microcylinder (LEM) and D-cylinder (LED). The space between the LE and the cylinder was fixed as 1.5% of chord length (c). The sizes of the cylinder were varied from 0.5% to 0.75% of the chord. The unstructured tetrahedral mesh elements were used to discretize the computational flow domain that consists of a single blade passage with periodic boundary conditions. The Reynolds-Averaged Navier-Stokes equations with the k-? shear stress transport (SST) turbulence equations were solved in a commercial CFD code Ansys CFX 18.1. The flow was considered incompressible. The present numerical study was compared with available open literature. The modified rotor blades showed a significant performance enhancement compared to the reference turbine. The peak efficiency was improved by 11.29% at a particular flow coefficient in 0.5%c radius LED-turbine. The presence of the cylinders delayed the flow separation and enhanced the operating range up to 11.11%.
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    Design and optimization of a marine current turbine: Effects of pitch angle and twist distribution
    (01-01-2019)
    Karthikeyan, T.
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    A 3 blade, 800 mm marine current turbine with 25° blade-pitch angle was numerically validated and modified to improve the turbine’s power coefficient using CFD and surrogate based optimization techniques. The pitch angle was varied from 15° to 30°. The twist distribution was varied along the blade span by an increment and decrement method. The twist was varied by a maximum of 95% increment/decrement with respect to its actual twist distribution. The combinations of all these designs were fed into in-house optimization code to find the optimal design point. A 13% increase in the power coefficient is reported.
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    Exit blade angle and roughness effect on centrifugal pump performance
    (01-01-2013)
    Bellary, Sayed Ahmed Imran
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    Exit blade angle and impeller surface roughness has a significant effect on the performance of a centrifugal pump impeller handling different viscosity fluids. In this paper, a three-dimensional flow simulation using Reynolds averaged Navier Stokes (RANS) equations for the performance analysis of the impeller is reported. The analysis using water and viscous liquids has been accomplished for different flow conditions, exit blade angle and roughness values. Standard k-ε two equation model is used for the turbulent closure of steady incompressible flow. The investigation shows that the blade exit angle has influence on the head, shaft power and efficiency of the impeller for different liquids. Rise in head, increase in shaft power and decrease in hydraulic efficiency have been observed with increasing roughness. Copyright © 2013 by ASME.
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    Experimental study of Wells turbine with multiparameter modification for wave energy conversion
    (01-01-2021)
    Kumar, Amit
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    Das, Tapas K.
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    In this article, a Wells turbine geometry is created with the modification of multiple geometric parameters, i.e., blade sweep/skew, endplate, casing groove, and guide vane. The experiment of a bidirectional turbine is conducted at the wave and fluid engineering laboratory, IIT Madras. The preliminary objective of the study is to measure the starting characteristics and corresponding flow velocity, revolution per minute (rpm), differential pressure of higher and lower pressure sides of the turbine. The output parameters are measured at different cycle times and the stroke length of a piston-cylinder combination, which simulates different wave conditions. After starting the Wells turbine, rotational and axial speeds increase for some time. After that, it will fluctuate between a specific range, and pressure is prepositional to the airflow rate. The wave energy can be converted into pneumatic energy with the help of wave energy converting(WEC) devices, i.e., oscillating water column(OWC) that can be further converted into mechanical energy and then into electrical energy with some appropriate devices. In this article, an experimental analysis of the turbine geometry is reported.
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    Design of a point absorber wave energy converter for an indian coast
    (06-05-2022)
    Kumar, Prashant
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    Singh, Devesh
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    Paul, Akshoy Ranjan
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    Ocean waves are considered as a potential unharnessed renewable resource being 800 times denser than wind. India has a wide coastal area of nearly 7500 km, providing a huge potential for harnessing ocean wave energy. The article aims to present the parametric optimization of a point absorber wave energy converter (PAWEC) for a location near Ennore port of India. Indian offshore condition such as significant wave height, period, and amplitude was reviewed for their minimum, maximum, and average values for several years. Hydrodynamic coefficients such as Froude-Krylov force, radiation damping, added mass, diffraction, excitation and response amplitude operator are optimized through geometric optimization of PAWEC's float. In hydrodynamic response analysis, only heaving motion is considered and all motion is neglected for the study. Regular wave is only considered for this study. Output parameters such as structure velocity and structure response are studied for the mentioned geometry. Power-take-off (PTO) device is simulated for maximum efficiency and the float velocity response is observed. Monthly variation in the mean absorbed power and efficiency of Point absorber is calculated with respect to ocean power.
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    Effect of guide vane angle on wells turbine performance
    (01-01-2014)
    Halder, Paresh
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    Wells turbines are used in oscillating water column wave energy system and the turbine has a stagger angle of 90o. Numerical analysis is performed to analyze the performance of the turbine in the present work. A commercial code ANSYSCFX ® v14.0 was used for the simulations at different flow coefficient, different angles and a constant rotational speed. The turbulence model was k-ω SST. Higher guide vane angle produced higher efficiency of the turbine and the efficiency (enhanced) change was contributed because of the vortex formation in different locations in the flow passage or near the blade surface.