Higher-order and length-scale statistics of velocity and temperature fluctuations in turbulent boundary layer along a heated vertical flat plate

Abedin, Mohammad Zoynal,Tsuji, Toshihiro,Kim, Nae-Hyun Elsevier 2017 The International journal of heat and fluid flow Vol.65 No.-

<P><B>Abstract</B></P> <P>Time-developing direct numerical simulation (DNS) was performed to clarify the higher-order turbulent behaviors in the thermally-driven boundary layers both in air and water along a heated vertical flat plate. The predicted statistics of the heat transfer rates and the higher-order turbulent behaviors such as skewness factors, flatness factors and spatial correlation coefficients of the velocity and temperature fluctuations in the natural-convection boundary layer correspond well with those obtained from experiments for space-developing flows. The numerical results reveal that the turbulent structures of the buoyancy-driven boundary layers are mainly controlled by the fluid motions in the outer region of the boundary layer, and these large-scale structures are strongly connected with the generation of turbulence in the thermally-driven boundary layers, in accordance with the actual observations for space-developing flows. Moreover, to specify the turbulence structures of the boundary layers, the cross-correlation coefficients and the characteristic length scales are examined for the velocity and thermal fields. Consequently, it is found that with a slight increase in freestream velocity, the cross-correlation coefficient for the Reynolds shear stress and turbulent heat flux increases for opposing flow and decreases for aiding flow, and the integral scales for the velocity and temperature fields become larger for opposing flow and smaller for aiding flow compared with those for the pure natural-convection boundary layer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Temporal DNS is done for thermally-driven boundary layer along a heated vertical flat plate. </LI> <LI> Turbulent structures are mainly controlled by fluid motions in the outer boundary layer. </LI> <LI> Large-scale structures are strongly connected with the generation of turbulence in the boundary layer. </LI> <LI> Cross-correlation coefficient for velocity and temperature fluctuations increases for opposing flow and decreases for aiding flow compared with the natural-convection boundary layer. </LI> <LI> Integral scales for velocity and temperature fields become larger for opposing flow and smaller for aiding flow compared with the natural-convection boundary layer. </LI> </UL> </P>

Evaluation of Submergence Tolerance in Landrace Rice Cultivars by Various Growth and Yield Parameters

Hasanul Abedin,Abdullah -Al Mamun,Abdul Baset Mia,Abdul Karim 한국작물학회 2019 Journal of crop science and biotechnology Vol.22 No.4

Flash flood causes a serious damage to rice crops in northern and eastern parts of Bangladesh almost every year. This study was designed to identify useful agronomic parameters for evaluation of submergence tolerance and to evaluate genotypes by multiple agronomic parameters for submergence tolerance at different growth stages. Twenty-one aman rice genotypes were tested against three submergence treatments viz. (i) no submergence or control, (ii) submerge at 10 days after transplanting (DAT), and (iii) submerge at 30 DAT. The experiment was laid out in a split plot design with three replications. The plants were completely submerged in the tanks for 14 days. Dry matter production, growth, yield, and yield components of rice were significantly reduced due to interaction effect of genotypes × submergence. Submergence at the early stage of growth (10 DAT) was more detrimental to plant growth than what happened at later stages (30 DAT). Wide genotypic differences in relative submergence tolerance based on grain and tiller numbers were identified. Grains and tiller numbers contributed most of the variation to seed yield among parameters investigated. When genotypes were ranked for submergence tolerance based on the means of multiple parameters, dramatic changes of submergence tolerance at early and later stages were observed in four genotypes; BRRI dhan33, Lalchikon, Achin and Sadamota were identified with a favorable combination of submergence tolerance. Cluster group ranking of genotypes based on multiple agronomic characters can be applied in submergence tolerance breeding to evaluate submergence tolerance and may have great advantage over conventional methods.

Root Development and Anti-Oxidative Response of Rice Genotypes under Polyethylene Glycol Induced Osmotic Stress

Juthy Abedin Nupur,Afsana Hannan,Md. Abir Ul Islam,G H M Sagor,Arif Hasan Khan Robin 한국육종학회 2020 Plant Breeding and Biotechnology Vol.8 No.2

Osmotic stress is a kind of stress which is directly or indirectly related to all other abiotic stresses. Four rice varietiesnamely Binadhan-11 (with SUB1 gene), BRRI dhan52 (with SUB1 gene), Binadhan-7 and BRRI dhan71 were used to study thevariation in root development and anti-oxidative response under osmotic stress conditions. Osmotic stress was induced by applyingpolyethylene glycol (4% PEG) in hydroponic solution. Treatment was given at the panicle initiation stage and leaf samples werecollected at fourteen days after treatment to estimate antioxidant response in terms of ascorbate (APX) and peroxidase (POD) enzymaticactivity. Roots were destructively harvested at 16 days after the stress imposition. The tested varieties showed significant differences inantioxidant responses under the stress condition such as high APX and POD in Binadhan-11 and BRRI dhan52. Significant injury at the4thleaf position (the youngest leaf was the reference) was observed at 8 and 12 days after the treatment. Number of live leaves, shootdry weight, density of second order lateral roots, number of phytomer (Pr) and total roots, number of roots at Pr2, main axis diameterat Pr1, main axis length at Pr1 varied significantly among the varieties × treatment combinations. Binadhan-11 and BRRI dhan52showed comparatively higher osmotic stress tolerance compared to the other two varieties without SUB1 gene, viz., Binadhan-7 andBRRI dhan71. The varieties BRRI dhan52, and Binadhan-11 showed greater capacity to withstand osmotic stress can be further used todevelop stress tolerant variety.

Liquid-phase Dehydration of 1-Phenylethanol to Styrene over an Acidic Resin Catalyst

Nazmul Abedin Khan,Jin-Soo Hwang,정성화 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.4

Dehydration of 1-phenylethanol to produce styrene has been studied in liquid phase with three solid acid catalysts such as H-ZSM-5, H-Y and Amberlyst-15. Amberlyst-15 shows the highest conversion and styrene yield, suggesting the applicability of a resin catalyst in the dehydration. The good performance of the Amberlyst-15 may be due to high acid concentration and ready diffusion of reactants and products. A possible reaction scheme (such as the formation of styrene from diphenylethylether) has also been suggested.

Facile Syntheses of Metal-organic Framework Cu3(BTC)2(H2O)3 under Ultrasound

Nazmul Abedin Khan,정성화 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.12

Cu-BTC[Cu3(BTC)2(H2O)3, BTC = 1,3,5-benzenetricarboxylate], one of the most well-known metal-organic framework materials (MOF), has been synthesized under atmospheric pressure and room temperature by using ultrasound. The Cu-BTC can be obtained in 1 min in the presence of DMF (N,N-dimethylformamide), suggesting the possibility of continuous production of Cu-BTC. Moreover, the surface area and pore volume show that the concentration of DMF is important for the synthesis of Cu-BTC having high porosity. The morphology and phase also depend on the concentration of DMF : Cu-BTC cannot be obtained at room temperature in the absence of DMF and aggregated Cu-BTC (with low surface area) is produced in the presence of high concentration of DMF. It seems that the deprotonation of benzenetricarboxylic acid by base (such as DMF) is inevitable for the room temperature syntheses.

Facile Syntheses of Metal-organic Framework Cu₃(BTC)₂(H₂O)₃ under Ultrasound

Khan, Nazmul Abedin,Jhung, Sung-Hwa Korean Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.12

Cu-BTC[$Cu_3(BTC)_2(H_2O)_3$, BTC = 1,3,5-benzenetricarboxylate], one of the most well-known metal-organic framework materials (MOF), has been synthesized under atmospheric pressure and room temperature by using ultrasound. The Cu-BTC can be obtained in 1 min in the presence of DMF (N,N-dimethylformamide), suggesting the possibility of continuous production of Cu-BTC. Moreover, the surface area and pore volume show that the concentration of DMF is important for the synthesis of Cu-BTC having high porosity. The morphology and phase also depend on the concentration of DMF : Cu-BTC cannot be obtained at room temperature in the absence of DMF and aggregated Cu-BTC (with low surface area) is produced in the presence of high concentration of DMF. It seems that the deprotonation of benzenetricarboxylic acid by base (such as DMF) is inevitable for the room temperature syntheses.

A Fog Based Agile Distribution of IoT Application(s) using Chef

Sarder Fakhrul Abedin,Md. Golam Rabiul Alam,Hyo Sung Kang,Seung Il Moon,Choong Seon Hong 한국정보과학회 2014 한국정보과학회 학술발표논문집 Vol.2014 No.12

The Month of the Year Effect on Dhaka Stock Exchange

Mohammad Zoynul Abedin,Guotai Chi,Meng Bin 보안공학연구지원센터 2015 International Journal of u- and e- Service, Scienc Vol.8 No.5

This study investigated the presence of month of the year (MOY) effect in Dhaka Stock Exchange (DSE), Bangladesh with the data from 2000 to 2012 of DSE all share index (DSI), DSE – 20 index (DSE – 20) and DSE general index (DGEN). DSE indexes were fluctuated more over the last couple of years and the only one previous study was conducted based on only DSI index as per our knowledge. The present study has made progress not only in relationship to documenting the month of year effect but also in highlighting potential explanations for its presence. Several hypotheses have been formulated; student’s t – statistics, ANOVA and dummy variable regression model were used in the study. The conclusion of all the findings is that the significant month of the year effect presents in DSE. So, investors can outperform the market and this is against in principle of market efficiency.

Challenges of Free App Advertisement Management in M2M-driven “Happy Internet”

Sarder Fakhrul Abedin,Rossi Kamal,Choong Seon Hong 한국정보과학회 2014 한국정보과학회 학술발표논문집 Vol.2014 No.6

An experimental study on accelerated fouling of aluminum oxide and ferric oxide particles in internally enhanced tubes

Mohammad Zoynal Abedin,NAE-HYUN KIM 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.12

This paper describes the results of accelerated particulate fouling tests performed on three enhanced tubes and a plain tube. The tests were performed using ferric oxide and aluminum oxide as foulant materials. Three enhanced tubes included 25 start, 10 start helically ribbed tubes and a ripple tube. Effects of the water velocity (0.9 to 1.8 m/s) and foulant concentration (750 to 2500 ppm) were investigated. At 750 ppm, the enhanced tubes fouled almost the same as the plain tube for the entire velocity range tested (0.9 to 1.8 m/s). The enhanced tube fouled faster than the plain tube for cases of high concentration combined with low velocities. Of the three enhanced tubes, the 25 start helically ribbed tube fouled faster than the ripple and the 10 start helically ribbed tubes. One thing to be noted is that the fouling concentrations used in the tests are significantly higher than would be expected in commercial heat exchangers. Also, the velocity range investigated is lower than would be expected in heat exchanger operation.