检索结果-南通市图书馆

The Two-Dimensional Supersonic Flow and mixing with a Perpendicular Injection in a Scramjet Combustor

Journal of Thermal Science 2003年第4期12卷 371-380页

作者： mohammad Ali S. Ahmed a.k.m. sadrul islam Department of mechanical Engineering Bangladesh University of Engineering and Technology (BUET) Dhaka-1000 Bangladesh.Department of Mechanical Engineering Bangladesh University of Engineering and Technology (BUET) Dhaka-1000 Bangladesh.Department of Mechanical Engineering Bangladesh University of Engineering and Technology (BUET) Dhaka-1000 Bangladesh.

A numerical investigation has been performed on supersonic mixing of hydrogen with air in a Scramjet (Supersonic Combustion Ramjet) combustor and its flame holding capability by solving Two-Dimensional full Navier-Stokes equations. The main flow is air entering through a finite width of inlet and gaseous hydrogen is injected perpendicularly from the side wall. An explicit Harten-Yee Non-mUSCL modified-flux-type TVD scheme has been used to solve the system of equations, and a zero-equation algebraic turbulence model to calculate the eddy viscosity coefficient. In this study the enhancement of mixing and good flame holding capability of a supersonic combustor have been investigated by varying the distance of injector position from left boundary keeping constant the backward-facing step height and other calculation parameters. The results show that the configuration for small distance of injector position has high mixing efficiency but the upstream recirculation can not evolved properly which is an important factor for flame holding capability. On the other hand, the configuration for very long distance has lower mixing efficiency due to lower gradient of hydrogen mass concentration on the top of injector caused by the expansion of side jet in both upstream and downstream of injector. For moderate distance of injector position, large and elongated upstream recirculation can evolve which might be activated as a good flame holder.

关键词： scramjet engine TVD scheme finite width of inlet supersonic mixing parallel air stream flame holding.

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Numerical Prediction of Fluid Flow and Heat Transfer in a Wavy Pipe

引用

Journal of Thermal Science 2001年第2期10卷 133-138,147页

作者： Shohel mahmud a.k.m. sadrul islam Prodip kumar Das Department of mechanical Engineering, Bangladesh University of Engineering & Technology, BUET, Dhaka-1000, Bangladesh Department of mechanical Engineering Bangladesh University of Engineering & Technology BUET Dhaka Bangladesh

Hydrodynamic and thermal characteristics in a pipe with sinusoidal wavy surface for steady laminar flow are invdtigted numerically in the present study. The integral forms of governing equations are discretized using control volume based Finite Volume method with collocated variable arrangement, SImPLE algorithm is used and TDmA solver is applied for solution of system of equations. A pipe of length equal to 4λ is considered. Effect of surface waviness, determined by wavelength-amplitude ratio λ/a (=L), on flow and thermal field is presented. The simulation work has been carried out for L’=11.0 -30.0 for a Reynolds number range50 to 2000. Results are presented in the form of Streamfunction, isothermal lines, velocity and vorticity profiles, change of mean friction factor, variation in skin fiction. local and average Nusselt number with Reynolds number, wave number (n) and L’. For a particular geometry. length of circulation zone increases with Reynolds number and approaches a limiting value for higher Reynolds number. Wall shear stress in the bulge part of the chancel shows smaller values that affect largely the be of heat transfer and Nusselt number shows minimum values in this region. This circulation zone drastically increases with the increase of surface waviness showing high mean friction factor per wavelength. mean friction factor inversely varies with Reynolds number. A correlation is proposed for calculating friction factor in the form f=C/(Re)m, where ’C and ’m’ represents two polynomials of degree 4 and 2 respectively and are function of L. Higher waviness of the surface shows the higher heat transfer rate than lower waviness. Heat transfer rate falls almost exponentially along the axial direction with the increase of wave number.

关键词： Nusselt number separation bubble surface wavomess wall vorticity

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

The Effect of Injection Angle on mixing and Flame Holding in Supersonic Combustor

引用

Journal of Thermal Science 2002年第1期11卷 80-91页

作者： Shakil Ahmed mohammad Ali A. k. m. sadrul islam Department of mechanical Engineering Bangladesh University of Engineering and Technology (BUET) Dhaka Bangladesh

A numerical study on mixing of hydrogen injected into a supersonic air stream has been performed by solving two-dimensional full Navier-Stokes equations. An explicit Harten-Yee Non-mUSCL modified-flux-type TVD scheme has been used to solve the system of equations, and a zero-equation algebraic turbulence model to calculate the eddy viscosity coefficient. The main objectives of this study are to increase the mixing efficiency and flame holding capability of a supersonic combustor. The performance of combustor has been investigated by varying the hydrogen injection angle made with the direction of air stream considering anti-clockwise direction as positive. The injector position from left boundary, backward-facing step height and the inlet width of air stream are kept constant. The results show that upstream of injector the mixing is dominated by recirculation and in downstream the mixing is dominated by mass concentration of hydrogen. Upstream recirculation is dominant for injecting angle 600 and 900 . Incorporating the various effects, perpendicular injection shows the maximum mixing efficiency and its large upstream recirculation region has a good flame holding capability.

关键词： scramjet engine TVD scheme backward-facing step supersonic mixing supersonic stream flame holding.

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Regression analysis of squeezing-induced hybrid nanofluid flow in Darcy-Forchheimer porous medium

引用

Applied mathematics and mechanics(English Edition) 2025年第1期46卷 193-208页

作者： k.mUHAmmAD m.SARFRAZ Department of Humanities and Sciences School of Electrical Engineering and Computer Science National University of Sciences and Technology Department of mathematics Quaid-i-Azam University

This article presents a mathematical model addressing a scenario involving a hybrid nanofluid flow between two infinite parallel plates. One plate remains stationary, while the other moves downward at a squeezing velocity. The space between these plates contains a Darcy-Forchheimer porous medium. A mixture of water-based fluid with gold(Au) and silicon dioxide(Si O2) nanoparticles is formulated. In contrast to the conventional Fourier's heat flux equation, this study employs the Cattaneo-Christov heat flux equation. A uniform magnetic field is applied perpendicular to the flow direction, invoking magnetohydrodynamic(mHD) effects. Further, the model accounts for Joule heating, which is the heat generated when an electric current passes through the fluid. The problem is solved via NDSolve in mATHEmATICA. Numerical and statistical analyses are conducted to provide insights into the behavior of the nanomaterials between the parallel plates with respect to the flow, energy transport, and skin *** findings of this study have potential applications in enhancing cooling systems and optimizing thermal management strategies. It is observed that the squeezing motion generates additional pressure gradients within the fluid, which enhances the flow rate but reduces the frictional drag. Consequently, the fluid is pushed more vigorously between the plates, increasing the flow velocity. As the fluid experiences higher flow rates due to the increased squeezing effect, it spends less time in the region between the plates. The thermal relaxation, however, abruptly changes the temperature, leading to a decrease in the temperature fluctuations.

关键词： convective boundary condition Darcy-Forchheimer medium hybrid nanofluid Joule heating magnetohydrodynamic (mHD) numerical solution squeezing flow regression analysis O361 O175.2

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Seedling Growth of Cassia tora, Cassia occidentalis and Cassia sophera in Relation to Salinity and pH

引用

Journal of Agricultural Science and Technology(A) 2015年第7期5卷 601-607页

作者： Sabiha Sultana a.k.m. Nazrul islam Ecology and Environment Laboratory Department of Botany University of Dhaka Dhaka 1000 Bangladesh

The paper aimed to investigate the growth of seedlings of three species of Cassia （C tora, C. sophera and C occidentalis） at different concentrations of salinity （NaC1） and pH treatments. All the species showed the highest seedling length under control condition, and with the increase of salinity, C occidentalis showed the highest sensitivity. The seedling length of C tora at 0.05 m NaCI significantly （P = 0.05） decreased to 5.71 cm, and further increase of salinity to 0.1 m, the seedling length was decreased to less than the value of 0.05 m NaC1 treatment and one-third （2.15 cm） of that of control （6.92 cm）. Seeds of all the species failed to germinate at 0.5 m NaC1. Scarified seeds of C. sophera and C occidentalis increased seedling length. The highest seedling length was in C. sophera, followed by C. tora and C. occidentalis. All the species showed significant decrease （P 〈 0.05） of fresh weight with the increase of salinity; scarification of seeds in C. occidentalis and C. sophera showed higher fresh weight than those of without scarification. Experiments at different pH levels did not show any significant （P = 0.05） change in seedling length, except C. sophera, while at acidic pH, both seedling length and dry weight were significantly （P 〈 0.05） decreased.

关键词： Cassia spp. seedling growth salinity pH.

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Band structure,Fermi surface,elastic,thermodynamic,and optical properties of AlZr3,AlCu3,and AlCu2Zr:First-principles study

引用

Chinese Physics B 2016年第8期25卷 103-112页

作者： Parvin R Parvin F Ali m S islam a.k.m.A Department of Physics Rajshahi University Rajshahi-6205 Bangladesh Department of Physics Pabna University of Science and Technology Pabna 6600 Bangladesh International islamic University Chittagong 154/A College Road Chittagong-4203 Bangladesh

The electronic properties（Fermi surface,band structure,and density of states（DOS）） of Al-based alloys Alm3（m=Zr and Cu） and AlCu2Zr are investigated using the first-principles pseudopotential plane wave method within the generalized gradient approximation（GGA）.The structural parameters and elastic constants are evaluated and compared with other available ***,the pressure dependences of mechanical properties of the compounds are *** temperature dependence of adiabatic bulk modulus,Debye temperature,specific heat,thermal expansion coefficient,entropy,and internal energy are all obtained for the first time through quasi-harmonic Debye model with phononic effects for T = 0 k-100 *** parameters of optical properties（dielectric functions,refractive index,extinction coefficient,absorption spectrum,conductivity,energy-loss spectrum,and reflectivity） of the compounds are calculated and discussed for the first *** reflectivities of the materials are quite high in the IR-visible-UV region up to ~ 15 eV,showing that they promise to be good coating materials to avoid solar *** of the properties are also compared with those of the Al-based Ni3 Al compound.

关键词： first principle calculations Fermi surface elastic moduli entropy and internal energy optical properties

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

New ternary superconducting compound LaRu2As2： Physical properties from density functional theory calculations

引用

Chinese Physics B 2017年第3期26卷 453-460页

作者： m A Hadi m S Ali S H Naqib a.k.m.A islam Department of Physics University of Rajshahi Rajshahi 6205 Bangladesh Department of Physics Pabna University of Science and Technology Pabna 6600 Bangladesh International islamic University Chittagong Chittagong 4203 Bangladesh

In this paper, we perform the density functional theory （DFT） -based calculations by the first-principles pseudopo- tential method to investigate the physical properties of the newly discovered superconductor LaRu2As2 for the first time. The optimized structural parameters are in good agreement with the experimental results. The calculated independent elas- tic constants ensure the mechanical stability of the compound. The calculated Cauchy pressure, Pugh＇s ratio as well as Poisson＇s ratio indicate that LaRu2As2 should behave as a ductile material. Due to low Debye temperature, LaRu2As2 may be used as a thermal barrier coating （TBC） material. The new compound should exhibit metallic nature as its valence bands overlap considerably with the conduction bands. LaRu2As2 is expected to be a soft material and easily machinable because of its low hardness value of 6.8 GPa. The multi-band nature is observed in the calculated Fermi surface. A highly anisotropic combination of ionic, covalent and metallic interactions is expected to be in accordance with charge density calculation.

关键词： new superconductor LaRu2As2 density functional theory (DFT) calculations mechanical proper-ties electronic features

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

mechanical and thermodynamical stability of BiVO4 polymorphs using first-principles study

引用

Chinese Physics B 2017年第3期26卷 395-403页

作者： a.k.m.Farid UI islam md Nurul Huda Liton H m Tariqul islam md Al Helal md kamruzzaman Department of Computer Science and Engineering Begum Rokeya University Rangpur Rangpur-5400 Bangladesh Department of Physics Begum Rokeya University Rangpur Rangpur-5400 Bangladesh Department of Chemistry Begum Rokeya University Rangpur Rangpur-5400 Bangladesh Department of Physics and materials Science and Center of Super-Diamond and Advanced Films (COSDAF) City University of Hong Kong Hong Kong SAR China

First principles calculations of structural, electronic, mechanical, and thermodynamic properties of different poly- morphs of BiVO4 are performed using Bender-type plane/wave ultrasoft pseudopotentials within the generalized gradient approximation （GGA） in the flame of density functional theory （DFT）. The calculated structural and electronic properties are consistent with the previous theoretical and experimental results. The electronic structures reveal that m-BiVO4, op- BiVO4, and st-BiVO4 have indirect band gaps, on the other hand, zt-BiVO4 has a direct band gap. From the DOS and mulliken＇s charge analysis, it is observed that only m-BiVO4 has 6s2 Bi lone pair. Bond population analysis indicates that st-BiVO4 shows a more ionic nature and a similar result is obtained from the elastic properties. From the elastic prop- erties, it is observed that st-BiVO4 is more mechanically stable than the others, st-BiVO4 is more ductile and useful for high electro-optical and electro-mechanical coupling devices. Our calculated thermodynamic properties confirm the similar characteristics found from electronic and elastic properties, m-BiVO4 is useful as photocatalysts, solid state electrolyte, and electrode and other polymorphs are applicable in electronic device fabrications.

关键词： BiVO4 crystal structure lone pair mechanical stability

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

An ab initio investigation of vibrational, thermodynamic, and optical properties of Sc_2AlC mAX compound

引用

Chinese Physics B 2016年第10期25卷 103-108页

作者： m A Ali m T Nasir m R khatun a.k.m.A islam S H Naqib Department of Physics Chittagong University of Engineering and Technology Department of Arts & Sciences Bangladesh Army University of Science and Technology Department of Physics University of Rajshahi International islamic University Chittagong

The structural vibrational, thermodynamical, and optical properties of potentially technologically important, weakly coupled mAX compound, Sc2 Al C are calculated using density functional theory(DFT). The structural properties of ScAlC are compared with the results reported earlier. The vibrational, thermodynamical, and optical properties are theoretically estimated for the first time. The phonon dispersion curve is calculated and the dynamical stability of this compound is investigated. The optical and acoustic modes are observed clearly. We calculate the Helmholtz free energy(F), internal energy(E), entropy(S), and specific heat capacity(Cv) from the phonon density of states. Various optical parameters are also calculated. The reflectance spectrum shows that this compound has the potential to be used as an efficient solar reflector.

关键词： mAX compound phonon dispersion thermodynamical properties optical properties

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Cardiac myxomas:A narrative review

引用

World Journal of Cardiology 2022年第4期14卷 206-219页

作者： a.k.m.monwarul islam Department of Cardiology National Institute of Cardiovascular DiseasesDhaka 1207Bangladesh

Cardiac myxomas are common primary neoplasms of the *** are biologically benign but“functionally malignant”because of the potential for *** arise most commonly from the left atrium,but no chambers of the heart are *** may be sporadic in the majority but also familial as a part of the Carney *** morphological forms exist:polypoid and *** myxomas often present with obstructive features,while the papillary forms are more prone to *** is still controversial;the current view centres around origin from the primitive pluripotent mesenchymal *** may be of giant proportion,be calcified or get *** presentation typically involves the triad of intracardiac obstruction,embolic events and constitutional *** examination findings may simulate those of mitral or tricuspid *** presence of tumour plop and change of the physical findings with changing position may help differentiation between the *** is the investigation of *** polypoid or papillary mobile mass within the atrial cavity remaining attached to the interatrial septum through a stalk are the tell-tale echocardiographic *** magnetic resonance and computed tomographic scanning may have incremental diagnostic *** examination reveals abundant loose myxoid stroma with scattered round,polygonal or stellate cells with dense irregular *** testing may detect mutations in the PRkAR1A gene in the familial form of cardiac myxoma,*** Carney *** excision is the mainstay of treatment with low operative mortality,excellent postoperative survival and low recurrence *** current trend favours minimal-access surgery with or without robotic *** should have appropriate preparedness to make a timely diagnosis and enthusiastic treatment to avoid potentially fatal complications.

关键词： myxoma Cardiac Neoplasm Carney Complex Echocardiography Embolism

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：