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Performance studies on an oscillating water column employing a Savonius rotor

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Science China(Technological Sciences) 2011年第7期54卷 1674-1679页

作者： Sandeep K PATEL Krishnil RAm m.rafiuddin ahmed Young-Ho LEE Division of mechanical Engineering the University of the South Pacific Division of mechanical and Information Engineering Korea Maritime University Busan Republic of Korea

A new oscillating water column (OWC) design is proposed in this study to incorporate a simpler Savonius type turbine. Conventional OWC devices employ a bi-directional turbine such as a Wells or an Impulse turbine to extract energy from the air. The disadvantages of the Wells turbine include its inability to self start and stalling. The Savonius turbine is much cheaper and is an effective option at low Reynolds numbers. In the current rectangular OWC device, unlike the circular OWC, the width of entry of the capture chamber can be increased without being influenced by the diameter at the turbine section. To improve its primary capture efficiency, the front and rear walls of the OWC are inclined to minimize reflection. The Savonius rotor characteristics are studied with respect to the change in frequency of the incoming waves. The rotor rpm is sensitive to wave period and primary conversion efficiency while changes in depth only affect the rotor rpm at lower frequencies. The Savonius rotor shows promising results and can be incorporated into large scale OWC devices to reduce costs of the turbine component of the system.

关键词： wave energy Savonius rotor oscillating water column inclined chamber

Studies on a low Reynolds number airfoil for small wind turbine applications

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Science China(Technological Sciences) 2011年第7期54卷 1684-1688页

作者： Joji WATA mohammed FAIZAL Boniface TALU Lesia VANAWALU Puamau SOTIA m.rafiuddin ahmed Division of mechanical Engineering University of the South Pacific

In contrast to large horizontal axis wind turbines (HAWTs) that are located in areas dictated by optimum wind conditions, small wind turbines are required for producing power without necessarily the best wind conditions. A low Reynolds number airfoil was designed after testing a number of low Reynolds number airfoils and then making one of our own; it was tested for use in small HAWTs. Studies using XFOIL and wind tunnel experiments were performed on the new airfoil at various Reynolds numbers. The pressure distribution, C p , the lift and drag coefficients, C L and C D , were studied for varying angles of attack, α. It is found that the airfoil can achieve very good aerodynamic characteristics at different Reynolds numbers and can be used as an efficient airfoil in small HAWTs.

关键词： low Reynolds number airfoil small wind turbines pressure distribution coefficient of lift coefficient of drag

Nanosecond pulse and dual-wavelength Q-switched 1.5 μm fiber laser using mAX phase Cr2TiAlC2 saturable absorber

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Optoelectronics Letters 2025年第1期21卷 7-12页

作者： ahmed Shakir AL-HITI Hiba HASSAN Department of Electrical Engineering Faculty of Engineering University of Anbar Department of Laser and Optoelectronics Engineering University of Technology-Iraq

We demonstrated a new type of mAX phase material, chromium titanium aluminum carbide（Cr2TiAlC2） polymer film, to generate a passively Q-switched erbium-doped fiber laser（EDFL）. The film thickness was measured to be around 45 μm, which was fabricated using the embedding method with polyvinyl alcohol（PVA） polymer as hoster. The saturable absorber（SA） film demonstrates a dual-wavelength passively Q-switched EDFL which operates at 1 531 nm and 1 560.19 nm, respectively. The Q-switching pulse duration could be varied from 2.46 μs to 770 ns, while the repetition rate varied from 92.76 kHz to 106.6 kHz with an increasing input pumping range from 154 mW to 300 mW. The maximum output power and pulse energy of 15.05 mW and 141.18 nJ were obtained at the maximum input power of 300 mW, respectively.

关键词： Saturable absorbers

Dynamic Interaction Analysis of Coupled Axial-Torsional-Lateral mechanical Vibrations in Rotary Drilling Systems

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Structural Durability & Health monitoring 2025年第1期19卷 77-103页

作者： Sabrina meddah Sid ahmed Tadjer Abdelhakim Idir Kong Fah Tee mohamed Zinelabidine Doghmane madjid Kidouche Applied Automation Laboratory Faculty of Hydrocarbons and ChemistryUniversity of BoumerdesBoumerdes35000Algeria Institute of Electrical and Electronic Engineering(IGEE) University of BoumerdesBoumerdes35000Algeria Laboratory of the Electrification of Industrial Enterprises University of BoumerdesBoumerdes35000Algeria Electrical Engineering Department Mohamed Boudiaf University of M’silaM’sila28000Algeria Department of Civil and Environmental Engineering King Fahd University of Petroleum&MineralsDhahran31261Saudi Arabia Interdisciplinary Research Center for Construction and Building materials King Fahd University of Petroleum&Minerals(KFUPM)Dhahran31261Saudi Arabia

maintaining the integrity and longevity of structures is essential in many industries,such as aerospace,nuclear,and *** achieve the cost-effectiveness of large-scale systems in petroleum drilling,a strong emphasis on structural durability and monitoring is *** study focuses on the mechanical vibrations that occur in rotary drilling systems,which have a substantial impact on the structural integrity of drilling *** study speciﬁcally investigates axial,torsional,and lateral vibrations,which might lead to negative consequences such as bit-bounce,chaotic whirling,and high-frequency *** events not only hinder the efﬁciency of drilling but also lead to exhaustion and harm to the system’s components since they are difﬁcult to be detected and controlled in real *** study investigates the dynamic interactions of these vibrations,speciﬁcally in their high-frequency modes,usingﬁeld data obtained from measurement while ***ﬁndings have demonstrated the effect of strong coupling between the high-frequency modes of these vibrations on drilling sys-tem *** obtained results highlight the importance of considering the interconnected impacts of these vibrations when designing and implementing robust control ***,integrating these compo-nents can increase the durability of drill bits and drill strings,as well as improve the ability to monitor and detect ***,by exploiting theseﬁndings,the assessment of structural resilience in rotary drilling systems can be ***,the study demonstrates the capacity of structural health monitoring to improve the quality,dependability,and efﬁciency of rotary drilling systems in the petroleum industry.

关键词： Rotary drilling systems mechanical vibrations structural durability dynamic interaction analysis ﬁeld data analysis

Effect of front guide nozzle shape on the flow characteristics in an augmentation channel of a direct drive turbine for wave power generation

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Science China(Technological Sciences) 2010年第1期53卷 46-51页

作者： Deepak PRASAD mohammed Asid ZULLAH mohammed rafiuddin ahmed Young-Ho LEE Graduate School Korea Maritime University1 Dongsam-dong Youngdo-kuBusan606-791Republic of Korea Division of mechanical Engineering University of the South PacificPrivate Mail BagLaucala CampusSuvaFiji Islands Division of mechanical & Information Engineering Korea Maritime University1 Dongsam-dong Youngdo-kuBusan606-791Republic of Korea

There is an increasing interest in cross flow turbines(also known as Banki turbines) for small and low head applications because of their simple structure as well as low capital and maintenance *** present work aims at implementing the direct drive turbine(DDT) of cross flow type for wave power generation.A numerical wave tank was used to simulate the waves and after obtaining the desired wave properties;the augmentation channel plus the front guide nozzle and rear chamber were integrated to the numerical wave *** waves in the numerical wave tank were generated by a piston type wave maker which was located at the wave tank *** inlet which was modeled as a plate wall moved sinusoidally with the general function x = asinω *** augmentation channel consisted of a front nozzle,rear nozzle and an internal fluid region which represented the turbine *** front and rear nozzles were geometrically the *** different front guide nozzle configurations were studied:a standard guide nozzle which was originally attached to the augmentation channel and two other front guide nozzles of different *** purpose of this study is to observe how the front guide nozzle shape influences the flow downstream,mainly in the augmenta-tion channel,water power and the first stage energy *** analysis was performed using a commercial CFD code *** results of the flow in the augmentation channel for the three front guide nozzles are presented in this paper.

关键词： numerical wave tank wave power augmentation channel direct drive turbine water power

Performance analysis of a wave energy converter using numerical simulation technique

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Science China(Technological Sciences) 2010年第1期53卷 13-18页

作者： mohammed Asid ZULLAH Deepak PRASAD mohammed rafiuddin ahmed Young-Ho LEE Graduate School Korea Maritime University Dongsam-dong Youngdo-kuBusan 606-791Republic of Korea Division of mechanical Engineering University of the South PacificPrivate Mail BagLaucala CampusSuvaFiji Islands Division of mechanical & Information Engineering Korea Maritime UniversityDongsam-dong Youngdo-kuBusan 606-791Republic of Korea

A general purpose viscous flow solver Ansys CFX was used to study a Savonius type wave energy converter in a 3D numerical viscous wave *** paper presents the results of a computational fluid dynamics(CFD) analysis of the effect of blade configuration on the performance of two Savonius rotors for wave energy extraction.A piston-type wave generator was incorporated in the computational domain to generate the desired incident waves.A complete OWC system with a 3-bladed Savonius rotor was modeled in a three dimensional numerical wave tank and the hydrodynamic conversion efficiency was *** flow over the rotors was assumed to be two-dimensional(2D),viscous,turbulent and *** CFX code was used with a solver of the coupled conservation equations of mass,momentum and energy,with an implicit time scheme and with the adoption of the hexahedral mesh and the moving mesh techniques in areas of moving *** was modeled with the k-e *** results indicated that the developed models are suitable to analyze the water flows both in the chamber and in the *** the turbine,the numerical results of pressure and torque were compared for the two cases.

关键词： wave energy Ansys CFX code Savonius rotor numerical simulation torque efficiency

Energy Efficiency of a Solar Green Building Using Bio-Sourced materials for Indoor Temperature and Humidity Optimization

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Energy Engineering 2025年第1期122卷 41-62页

作者： Soumiamounir Youssef maaloufa Abdelhamid Khabbazi Elinamohd Husini Nurul SyalaAbdul Latip YakubuAminuDodo Rime ELHarrouni minaAmazal Asma Souidi malika Atigui ahmed Aharoune National School of Architecture Agadir New Complex Ibn ZohrAgadirBP 20732Morocco EmDD CERNE2DUniversity of Mohammed V in RabatEst SaleSaleBP 227Morocco Thermodynamics and Energetics Laboratory Faculty of ScienceIbn Zohr UniversityAgadirBP 8106Morocco Faculty of Built Environment University Sains Islam MalaysiaNilaiBP 71800Malaysia Architectural Engineering Department Najran UniversityNajranBP 1988Saudi Arabia The Centre of Scientific and Engineering Research Najran UniversityNajranBP 1988Saudi Arabia Euro-mediterranean School of Architecture Design and UrbanismEuro-Mediterranean University of FezFezBP 51Morocco

A clean environment with low carbon emissions is the goal of research on the development of green and sustainable buildings that use bio-sourced materials in conjunction with solar energy to create more sustainable *** is particularly true in Africa,where there aren’t many studies on the *** current study suggests a 90 m^(2) model of a sustainable building in a dry climate that is movable to address the issue of housing in remote areas,ensures comfort in harsh weather conditions,uses solar renewable resources—which are plentiful in Africa—uses biosourced materials,and examines how these materials relate to temperature and humidity control while emitting minimal carbon *** order to solve the topic under consideration,the work is split into two sections:numerical and experimental *** TRNSYS and Revit,the suggested prototype building is examined numerically to examine the impact of orientation,envelope composition made of bio-sourced materials,and carbon *** a hygrothermal investigation,experiments are conducted to evaluate this prototype’s ***,an examination of the photovoltaic system’s production,consumption,and several scenarios used tomaximize battery life is included in the *** the biosourcedmaterial achieves a thermal transmittance of 0.15(W.m^(-2).K^(-1)),the results demonstrate an intriguing finding in terms of *** value satisfies the requirements of passive building,energy autonomy of the dwelling,and injection in-network with an annual value of 15,757 ***,compared to the literature,the heating needs ratio is 6.38(kWh/m^(2).an)and the cooling needs ratio is 49(kWh/m^(2).an),both of which are good *** to international norms,the inside temperature doesn’t go above 26℃,and the humidity level is within a comfortable range.

关键词： Bio-sourced materials energy sustainability green architecture built environment

Experimental studies on the flow characteristics in an inclined bend-free OWC device

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Journal of Ocean Engineering and Science 2016年第1期1卷 77-83页

作者： Krishnil Ravinesh Ram mohammed rafiuddin ahmed mohammed Asid Zullah Young-Ho Lee Division of mechanical Engineering The University of the South PacificSuvaFiji Division of mechanical and Energy System Engineering Korean Maritime and Ocean UniversityBusanRepublic of Korea

A bend-free rectangular cross-section OWC device was designed and constructed for studying the effect of inclination on the flow characteristics inside the *** inclination is meant to reduce reflection of waves and induce higher velocities in the turbine *** measurements were made in a wave channel where the OWC device was *** S-type Pitot tube was used to measure dynamic pressure of air in the turbine section at several *** Image Velocimetry(PIV)was also done to study the flow of both air and water in the OWC *** order to focus solely on primary energy capture,no turbine was installed in the OWC *** dynamic pressure readings were analysed for suction and compression *** volume fluctuations inside the capture chamber were also recorded and compared for different *** result was an increase in the velocity of air flowing in the capture chamber and hence a rise in the kinetic energy available to the *** was found from experimental studies that as the angle of inclination reduced,the velocity of air in the turbine section *** lower angles also caused higher run-up and larger volume of water into the capture chamber.

关键词： Oscillating water column Particle Image Velocimetry Wave energy.

Boundary layer flow of maxwell fluid due to torsional motion of cylinder: modeling and simulation

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Applied mathematics and mechanics(English Edition) 2020年第4期41卷 667-680页

作者： m.KHAN A.ahmed J.ahmed Department of mathematics Quaid-i-Azam UniversityIslamabad 44000Pakistan Department of Basic Sciences University of Engineering and TechnologyTaxila 47050Pakistan

This paper investigates the boundary layer flow of the maxwell fluid around a stretchable horizontal rotating cylinder under the influence of a transverse magnetic *** constitutive flow equations for the current physical problem are modeled and analyzed for the first time in the *** torsional motion of the cylinder is considered with the constant azimuthal velocity *** partial differential equations(PDEs)governing the torsional motion of the maxwell fluid together with energy transport are simplified with the boundary layer *** current analysis is valid only for a certain range of the positive Reynolds ***,for very large Reynolds numbers,the flow becomes ***,the governing similarity equations are simplified through suitable transformations for the analysis of the large Reynolds *** numerical simulations for the flow,heat,and mass transport phenomena are carried out in view of the bvp4c scheme in *** outcomes reveal that the velocity decays exponentially faster and reduces for higher values of the Reynolds numbers and the flow penetrates shallower into the free stream *** is also noted that the phenomenon of stress relaxation,described by the Deborah number,causes to decline the flow fields and enhance the thermal and solutal energy transport during the fluid *** penetration depth decreases for the transport of heat and mass in the fluid with the higher Reynolds *** excellent validation of the numerical results is assured through tabular data with the existing literature.

关键词： torsional motion maxwell fluid magnetic field stretchable rotating cylinder bvp4c scheme