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Abdus Samad
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Abdus Samad
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Abdus Samad
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Samad, A.
Samad, Abdus
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15 results
Now showing 1 - 10 of 15
- PublicationNumerical optimization of wells turbine for wave energy extraction(01-01-2017)
;Halder, Paresh ;Rhee, Shin HyungThe present work focuses multi-objective optimization of blade sweep for a Wells turbine. The blade-sweep parameters at the mid and the tip sections are selected as design variables. The peak-torque coefficient and the corresponding efficiency are the objective functions, which are maximized. The numerical analysis has been carried out by solving 3D RANS equations based on k-w SST turbulence model. Nine design points are selected within a design space and the simulations are run. Based on the computational results, surrogate-based weighted average models are constructed and the population based multi-objective evolutionary algorithm gave Pareto optimal solutions. The peak-torque coefficient and the corresponding efficiency are enhanced, and the results are analysed using CFD simulations. Two extreme designs in the Pareto solutions show that the peak-torque-coefficient is increased by 28.28% and the corresponding efficiency is decreased by 13.5%. A detailed flow analysis shows the separation phenomena change the turbine performance. - PublicationEffect of microcylinder and d-cylinder at the leading edge of a wells turbine harvesting wave energy(01-01-2021)
;Sadees, P. ;Kumar, P. MadhanWells 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%. - PublicationThe effect of midplane guide vanes in a biplane wells turbine(01-05-2019)
;Das, Tapas K.Guide vanes (GVs) improve the performance of a turbine in terms of efficiency, torque, or operating range. In this work, a concept of different orientations of GVs in between a two-row biplane wells turbine (BWT) was introduced and analyzed for the performance improvement. The fluid flow was simulated numerically with a commercial software ANSYS CFX 16.1. The Reynolds-averaged Navier-Stokes equations with the k-Ï ‰ turbulence closure model were solved for different designs and flow conditions. For the base model, the results from simulation and experiments are in close agreement. Among the designs considered, the configuration, where the blades are in one line (zero circumferential angle between blades of two plane) and the midplane guide vane has concave side to the leading edge of the blade, performed relatively better. However, the performance was still less compared to the base model. The reason behind the reduction in performance from the base model is attributed to the blockage of flow and the change of flow path occurring due to the presence of the midplane GVs. The flow analysis of different cases and the comparison with the base model are presented in the current study. - PublicationPerformance improvement of a Wells turbine through an automated optimization technique(01-12-2022)
;Das, Tapas K. ;Kerikous, Emeel ;Venkatesan, Nithya ;Janiga, Gabor ;Thevenin, DominiqueThe present article reports optimization of the performance of a Wells turbine, which is an axial turbine utilized for wave energy conversion, through a computational fluid dynamics (CFD) based automated optimization technique. The in-house optimization library OPAL++ was coupled to a commercial CFD solver to get the Pareto front defining the relationships between two objectives. Four different geometric parameters of the turbine with ring-type endplate were used, and the objectives were to maximize the torque coefficient and simultaneously minimize the pressure drop coefficient. From the Pareto front, two designs (G1 and G2) were chosen for further analysis. G1 improved the peak torque-coefficient by more than 120 % and delayed the stall point from φ = 0.225 to φ = 0.3, while the peak efficiency dropped. Whereas, G2 improved the peak efficiency by 9.1 %, but the peak torque coefficient was reduced by about 50 %. The main contribution of the study is to develop an optimum Wells turbine geometry through the coupling of CFD and automated optimization algorithm - first of its kind applied to a Wells turbine with endplate. A detailed flow analysis, the influence of the endplate, and a comparison of the optimized geometries are presented. - PublicationExperimental and Numerical Investigation of the Performance of a Centrifugal Pump When Pumping Water and Light Crude Oil(01-11-2017)
;Siddique, M. Hamid ;Bellary, Sayed Ahmed Imran; ;Kim, Jin HyukChoi, Young SeokIn the oil and gas industry, crude oil is frequently transported and centrifugal pumps are used extensively. The pump impeller works under both design and off-design conditions in the applications, and the flow pattern deviates from the ideal case because of viscosity and density changes. An experimental as well as a numerical study was conducted to study the performance of a pump delivering water and light crude oil under design and off-design conditions. A 3D steady incompressible flow in the centrifugal pump was simulated by solving the Reynolds-averaged Navier–Stokes equations and SST turbulence model. At a low flow rate, extensive reverse flow occurs at the inlet of the impeller in the case of water, whereas the opposite was found for light crude oil. Recirculation was observed in the impeller flow passage for both water and the crude oil, but this diminished at higher flow rates. - PublicationEffect of stall fence on the performance of an axial turbine for wave energy conversion(01-01-2019)
;Das, Tapas K.Wells turbine is one type of axial turbine exclusively used for wave energy conversion in Oscillating Water Column type wave energy conversion device. It is a bi-directional turbine which can rotate in one direction irrespective of the direction of airflow. One of the main disadvantages of this turbine is the stall phenomenon, where the torque, as well as efficiency, drops drastically at a particular angle of attack. The postponement of stall can be achieved by installing fences along the chord of the blade at a distance from the hub. In the present work, a numerical analysis of Wells turbine with the stall fence is carried out using commercial CFD tool ANSYS. The performance characteristics of the turbine are investigated for different number of stall fences at different distances along the span of the blade. A detail flow analysis is presented to explain the effect of the stall fence on this particular turbine. - PublicationOptimization of Gap-to-Chord Ratio of Wells Turbine with Guide Vanes for Wave Energy Conversion(01-01-2021)
;Varghese, F. A.Wells turbine (WT) used for harnessing wave energy has narrow operating range and poor starting characteristics. To enhance its starting and running characteristics, guide vanes (GV) are installed upstream and downstream of the rotor. This paper studies the effect of the gap-to-chord (G/ lr) ratio of the WT GV on the turbine performance numerically. The work incorporates validation of the numerical simulations with experimental results and application of optimization techniques to find the optimal G/ lr ratio. A range for G/ lr ratio is suitably selected for the analysis and metamodel based on Kriging algorithm is developed. Following this, the optimization algorithm of screening is utilized to find the optimal conditions to achieve the objective function. - PublicationA concept of cascading of a fluidic diode for an OWC wave energy converter(01-01-2021)
;Hithaish, Doddamani; Takao, ManabuA fluidic diode (FD) cascading concept was proposed and analyzed to determine the effect on the oscillating water column (OWC) wave energy converter performance. The FD, coupled with a twin-turbine, can improve energy conversion. The performance of the FD is given by the diodicity, which is the ratio of pressure drops. In this paper, the concept of cascading of FD is numerically investigated by solving the three-dimensional Reynolds Averaged Navier Stokes (RANS) equations. The commercial computational fluid dynamics (CFD) tool ANSYS FLUENT 16.1 is used for the present investigation. The present study showed that the cascading increased pressure drops in both directions, which reduces the diodicity compared to the base model. The performance of the twin turbine with cascade FD underperformed than the twin-turbine without FD model. - PublicationPerformance Analysis of an Air Turbine for Ocean Energy Extraction Using CFD Technique(01-06-2019)
;Thandayutham, Karthikeyan; ;Salam, A. ;Baruah, D.Dudhgaonkar, P. V.The oscillating water column, which has a pneumatic section, can convert wave energy to air pressure, and thus, it rotates the turbine. The system has an inherent weakness of having low efficiency. Typically, the small Wells or axial turbines without any modifications have an efficiency of less than 40% under good sea wave condition which is a drawback and considered as less efficient to extract energy from the oceans. In this paper, the performance of the turbine is studied and analyzed by a computational fluid dynamics technique. ANSYS commercial code is used to discretize the mass, momentum, energy equations, and the turbine efficiency was evaluated. Different guide vane angles and turbine diameters were considered for the simulations. The modified turbines are simulated to operate in various rotational speeds which are similar to an actual working of oscillating water column. This helps to find a suitable operational range for the proposed turbine for energy extraction. It was found that the bigger turbines are expected to produce relatively higher efficiencies at lower speeds and lower pressures. - PublicationOptimization of a horizontal axis marine current turbine via surrogate models(01-06-2019)
;Thandayutham, Karthikeyan ;Avital, E. J. ;Venkatesan, NithyaFlow through a scaled horizontal axis marine current turbine was numerically simulated after validation and the turbine design was optimized. The computational fluid dynamics (CFD) code Ansys-CFX 16.1 for numerical modeling, an in- house blade element momentum (BEM) code for analytical modeling and an in- house surrogate-based optimization (SBO) code were used to find an optimal turbine design. The blade-pitch angle (θ) and the number of rotor blades (NR) were taken as design variables. A single objective optimization approach was utilized in the present work. The defined objective function was the turbine's power coefficient (CP). A 3x3 full-factorial sampling technique was used to define the sample space. This sampling technique gave different turbine designs, which were further evaluated for the objective function by solving the Reynolds-Averaged Navier-Stokes equations (RANS). Finally, the SBO technique with search algorithm produced an optimal design. It is found that the optimal design has improved the objective function by 26.5%. This article presents the solution approach, analysis of the turbine flow field and the predictability of various surrogate based techniques.