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Structure of Periodic Flows through a Channel with a Suddenly Expanded and Contracted Part

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Open Journal of Fluid Dynamics 2023年第S1期13卷 232-249页

作者： Takuya Masuda Toshio Tagawa miah md. ashraful alam Yasutaka Hayamizu Department of Integrated Engineering National Institute of Technology Yonago College Tottori Japan Department of Aeronautics and Astronautics Tokyo Metropolitan University Tokyo Japan Department of Mechanical Engineering for Transportation Faculty of Engineering Osaka Sangyo University Osaka Japan

With respect to flows in a two-dimensional sudden expansion and contraction channel having a pair of cavities, numerical simulation was performed by imposing inlet/outlet boundary conditions giving a velocity distribution to the inlet. Periodic flows have been reproduced, which have a discrete spectrum about frequency. A fundamental wave occupies most part of the disturbance components, but higher harmonic waves are also included. The disturbance is excited by Kelvin-Helmholtz instability in a cavity section, where only the fundamental wave is generated. A wavenumber is regulated by a channel length under a periodic boundary condition, but there is no restriction in a main flow direction under the inlet/outlet boundary conditions, and therefore, some wavenumbers can occur. Therefore, an arbitrary frequency component of disturbance is a synthesized wave composed of various wave numbers. There are two kinds of components constituting this synthesized wave: a maximum of a velocity distribution is near a wall and in the center of the channel, which are called as wall mode and central mode in linear stability analysis of the plane Poiseuille flow. The synthesized wave composed of some modes shows a tendency to lower wavenumbers at the center of the channel.

关键词： Frequency Spectrum Harmonic Wave Number Phase Velocity Superposition Eigenfunction Profile

A Study on Fluidic Diode for Wave Energy Conversion-Effect of Bypass Geometry on the Turbine Performance

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Open Journal of Fluid Dynamics 2020年第3期10卷 270-278页

作者： Keito Matsumoto Manabu Takao Shinya Okuhara miah md. ashraful alam Yoichi Kinoue National Institute of Technology Matsue College Matsue Japan Institute of Ocean Energy Saga University Saga Japan

A twin-impulse turbine for bi-directional flow has been developed for wave energy converter. However, the previous studies elucidated that the mean efficiency of the twin turbine is much lower than that of the impulse turbine for a unidirectional flow because a portion of airflow passes through the reverse flow turbine whose efficiency is very low. Therefore, a fluidic diode was adopted in the twin-impulse turbine in order to reduce the air flow through the reverse flow turbine. In this study, the rectification effect of the fluidic diode was investigated where a bypass is introduced into a blunt body. A computational fluid dynamics (CFD) analysis was conducted to investigate the effect of fluidic diodes on the turbine performance. In this analysis, RANS equations were used as the governing equations and the standard k-ε model was used as the turbulence model. The computational domain is composed of a circular tube and fluidic diode, and the domain meshed with an approximately 1.5 million mesh elements. As a result, it was found that the rectification effect of the fluidic diode is enhanced by installing a blunt body with a bypass hole of 5° taper angle.

关键词： Fluidic Diode Wave Energy Conversion Twin-Impulse Turbine CFD Analysis

Supersonic Moist Air Jet Impingements on Flat Surface

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Journal of Thermal Science 2010年第1期19卷 51-59页

作者： alam miah md.ashraful MATSUO Shigeru SETOGUCHI Toshiaki Graduate School of Science & Engineering Saga University1Honjo-machiSaga-shiSaga 840-8502Japan Department of Mechanical Engineering Saga University1Honjo-machiSaga-shiSaga 840-8502Japan Institute of Ocean Energy Saga University1Honjo-machiSaga-shiSaga 840-8502Japan

Pronounced aeroacoustic resonances are exhibited in the flow field where a jet emerges from an orifice or a nozzle and impinges on a solid surface. One instance where such resonances are produced is in a high speed jet impingement, such as in the space launch vehicle systems, jet-engine exhaust impingement, and in the short take-off and vertical landing （STOVE） aircraft, etc. A highly unsteady flowfield leading to a drastic increase of noise level with very high dynamic pressure and thermal loads are noticed on nearby surfaces results dramatic lift loss, severe ground erosion and hot gas ingestion to the inlet in the jet engines. This highly unsteady behavior of the im- pinging jets is due to a feedback loop between the fluid and acoustic fields. In actual jet flow, the working gas may contain condensable gas such as steam or moist air. In these cases, the non-equilibrium condensation may occur at the region between nozzle exit and an object. The jet flow with non-equilibrium condensation may be quite different from that without condensation. Therefore, in this study, the effect of the non-equilibrium condensation of moist air on the axisymmetric under-expanded supersonic impinging jet on a vertical flat plate was investigated numerically.

关键词： compressible flow supersonic impinging non-equilibrium condensation oscillation

Effect of Non-Equilibrium Condensation of Moist Air on Unsteady Behaviour of Shock Waves around a Circular Arc Blade

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Journal of Thermal Science 2007年第2期16卷 134-139页

作者： Shigeru MATSUO Kenbu TERAMOTO miah md.ashraful alam Toshiaki SETOGUCHI Heuy Dong KIM Shen YU Department of Mechanical Engineering Saga University1Honjo-machiSaga-shiSaga 840-8502Japan Department of Mechanical Engineering Khulna University of Engineering & TechnologyKhulna-9203Bangladesh School of Mechanical Engineering Andong National University388Songchun-dongAndong 760749Korea Institute of Engineering Thermophysics Chinese Academy of SciencesP.O.Box 2706Beijing 100080China

The unsteady phenomena in the transonic flow around airfoils are observed in the flow field of fan, compressor blades and butterfly valves, and this often causes serious problems such as the aeroacoustic noise, the vibration. In the transonic or supersonic flow where vapour is contained in the main flow, the rapid expansion of the flow may give rise to a non-equilibrium condensation. However, the effect of non-equilibrium condensation on the transonic internal flows around the airfoil has not yet been clarified satisfactorily. In the present study, the effect of non-equilibrium condensation of moist air on the self-excited shock wave oscillation on a circular arc blade was investigated numerically. The results showed that in the case with non-equilibrium condensation, frequencies of the flow oscillation became smaller than those without the non-equilibrium condensation.

关键词： compressible flow transonic flow shock wave oscillation non-equilibrium condensation simulation

Design and Optimization of Photonic Crystal Fiber Based Sensor for Gas Condensate and Air Pollution Monitoring

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Photonic Sensors 2017年第3期7卷 234-245页

作者： md. Ibadul ISLAM Kawsar AHMED Shuvo SEN Sawrab CHOWDHURY Bikash Kumar PAUL md. Shadidul ISLAM Mohammad Badrul alam miah Sayed ASADUZZAMAN Department of Information and Communication Technology (ICT) Mawlana Bhashani Science and Technology University Santosh Tangail 1902 Bangladesh Group of Bio-photomatix Tangail 1902 Bangladesh Department of Software Engineering (SWE) Daffodil International University Sukrabad Dhaka 1207 Bangladesh

In this paper, a hexagonal shape photonic crystal fiber （H-PCF） has been proposed as a gas sensor of which both micro-structured core and cladding are organized by circular air cavities. The reported H-PCF has a single layer circular core which is surrounded by a five-layer hexagonal cladding. The overall pretending process of the H-PCF is completed by using a full vectorial finite element method （FEM） with perfectly matched layer （PML） boundary condition. All geometrical parameters like diameters and pitches of both core and cladding regions have fluctuated with an optimized structure. After completing the numerical analysis, it is clearly visualized that the proposed H-PCF exhibits high sensitivity with low confinement loss. The investigated results reveal the relative sensitivity of 56.65% and confinement loss of 2.31×10^-5 dB/m at the 1.33%tm wavelength. Moreover, effective area, nonlinearity, and V-parameter of the suggested PCF are also briefly described.

关键词： Relative sensitivity confinement loss gas sensor effective area nonlinearity and photonic crystal fiber

Options and Opportunities for Energy Management in Malaysian Grid Systems-Putrajaya as a Case Study

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Journal of Electronic Science and Technology 2018年第4期16卷 316-324页

作者： Aravind CV Umashankar Subramaniam md.Shahrukh Adnan Khan md. Ibrahim Ibne alam School of Engineering Taylor’s University Subang Jaya 47500 Malaysia Department of Energy and Power Electronics VIT University Vellore 632014 India University of Asia Pacific Dhaka 1205 Bangladesh

This paper presents an opportunity for energy management with an integrated photovoltaic and wind farm for the energy and economic aspects of the commercial area located in Putrajaya. The energy economy accession conforming to the wind speed, temperature, solar irradiation, and energy consumption on a daily basis is taken into consideration. Design analysis is done through the industry standard numerical tool. From the result analysis, the recommended ratio of renewable share minimizing stress to the electric grid is proposed. According to the solutions obtained from the numerical design tool, photovoltaic is recommended to be more energy efficient and economically viable in comparison of the fully crowded wind farm. From the proposed solutions, the photovoltaic is able to provide 51% of the energy consumed and it costs RM 0.365 per kW/h.

关键词： Cost grid Homer Pro photovoltaic park wind turbine farm

Removal of phenol by activated carbons prepared from palm oil mill effluent sludge

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Journal of Environmental Sciences 2006年第3期18卷 446-452页

作者： md. Zahangir alam Suleyman A. MUYIBI Mariatul F. MANSOR Radziah WAHID Bioenvironmental Engineering Research Unit Department of Biotechnology Enginee ring Faculty of Engineering International Islamic University Malaysia Jalan G ombak 53100 Kuala Lumpur Malaysia.

The study was attempted to produce activated carbons from palm oil mill effluent （POME） sludge. The adsorption capacity of the activated carbons produced was evaluated in aqueous solution of phenol. Two types of activation were followed, namely, thermal activation at 300, 500 and 800%, and physical activation at 150% （boiling treatment）. A control （raw POME sludge） was used to compare the adsorption capacity of the activated carbons produced. The results indicated that the activation temperature of 800℃ showed maximum absorption capacity by the activated carbon （POME 800） in aqueous solution of phenol. Batch adsorption studies showed an equilibrium time of 6 h for the activated carbon of POME 800. It was observed that the adsorption capacity was higher at lower values ofpH （2--3） and higher value of initial concentration of phenol （200--300 mg/L）, The equilibrium data were fitted by the Langmuir and Freundlich adsorption isotherms. The adsorption of phenol onto the activated carbon POME 800 was studied in terms of pseudo-first and second order kinetics to predict the rate constant and equilibrium capacity with the effect of initial phenol concentrations. The rate of adsorption was found to be better correlation for the pseudo-second order kinetics compared to the first order kinetics.

关键词： activated carbon adsorption palm oil mill effluent (POME) sludge phenol

Activated carbons derived from oil palm empty-fruit bunches: Application to environmental problems

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Journal of Environmental Sciences 2007年第1期19卷 103-108页

作者： md. Zahangir alam Suleyman A. MUYIBI Mariatul F. MANSOR Radziah WAHID Bioenvironmental Engineering Research Unit Department of Biotechnology Engineering Faculty of EngineeringInternational Islamic University MalaysiaJalan Gombak53100 Kuala LumpurMalaysia.

Activated carbons derived from oil palm empty fruit bunches （EFB） were investigated to find the suitability of its application for removal of phenol in aqueous solution through adsorption process, Two types of activation namely; thermal activation at 300, 500 and 800℃and physical activation at 150℃ （boiling treatment） were used for the production of the activated carbons. A control （untreated EFB） was used to compare the adsorption capacity of the activated carbons produced from these processes. The results indicated that the activated carbon derived at the temperature of 800℃ showed maximum absorption capacity in the aqueous solution of phenol. Batch adsorption studies showed an equilibrium time of 6 h for the activated carbon at 800℃. It was observed that the adsorption capacity was higher at lower values of pH （2-3） and higher value of initial concentration of phenol （200-300 mg/L）. The equilibrium data fitted better with the Freundlich adsorption isotherm compared to the Langmuir. Kinetic studies of phenol adsorption onto activated carbons were also studied to evaluate the adsorption rate. The estimated cost for production of activated carbon from EFB was shown in lower price （USD 0.50/kg of activated carbon） compared the activated carbon from other sources and processes.

关键词： activated carbon adsorption lignocellulosic empty fruit bunches phenolic compound solid waste management

Turning Trash into Treasure: Developing an Intelligent Bin for Plastic Bottle Recycling

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Journal of Social Computing 2024年第1期5卷 1-14页

作者： Sirajam Munira Niloy Paul md.ashraful alam md.Mahmudur Rahman M.Shamim Kaiser Institute of Information Technology Jahangirnagar UniversityDhaka 1342Bangladesh

Plastic pollution has emerged as a major global concern due to its enduring nature and limited recycling *** response to this critical challenge,this paper presents a novel approach utilizing a Detection-Based Reward System(DBRS)alongside an innovative business model to promote effective plastic waste management,reduce plastic waste accumulation in the nature,and uphold environmental *** the YOLOv5 algorithm for its exceptional accuracy,speed,and open-source availability,plastic bottle detection becomes a pivotal aspect of this *** seamlessly enroll in the system,triggering an automated detection process that computes reward points corresponding to their deposited plastic *** reward points are meticulously stored within a centralized *** its operational facets,this comprehensive system encompasses a robust business model,strategically poised to capture widespread engagement with waste disposal practices,thereby contributing to the realization of Sustainable Development Goals(SDGs)geared towards fostering a healthier ***,the DBRS attains cutting-edge performance in plastic bottle detection,boasting an impressive mean Average Precision(mAP)of 0.973,underscoring its efficacy in tackling plastic pollution.

关键词： smart environment reward system YOLOv5 deep learning business model