检索结果-南通市图书馆

Acta Mechanica Sinica 2015年第4期31卷 570-580页

作者： laith k.abbas Qinbo Zhou Hossam Hendy Xiaoting Rui Institute of Launch Dynamics Nanjing University of Science and Technology

The analysis of natural vibration characteristics has become one of important steps of the manufacture and dynamic design in the aerospace industry. This paper presents a new scenario called virtual cutting in the context of the transfer matrix method of linear multibody systems closed- loop topology for computing the free vibration characteristics of elastically coupled flexible launch vehicle boosters. In this approach, the coupled system is idealized as a triple-beam system-like structure coupled by linear translational springs, where a non-uniform free-free Euler-Bemoulli beam is used. A large thrust-to-weight ratio leads to large axial accelera- tions that result in an axial inertia load distribution from nose to tail. Consequently, it causes the development of significant compressive forces along the length of the launch vehicle. Therefore, it is important to take into account this effect in the transverse vibration model. This scenario does not need the global dynamics equations of a system, and it has high computational efficiency and low memory requirements. The validity of the presented scenario is achieved through com- parison to other approaches published in the literature.

关键词： Transfer matrix method of linear multibodysystems Free vibration characteristics Coupled launchvehicle boosters

Aero-thermo-elastic Numerical Calculation and Analysis of Spinning Rocket

在线全文

学校读者我要写书评

暂无评论

Transactions of Nanjing University of Aeronautics and Astronautics 2014年第6期31卷 681-687页

作者：陈东阳 laith k.abbas 芮筱亭 Marzocca Piergiovanni 王国平 Institute of Launch Dynamics Nanjing University of Science and Technology Department of Mechanical and Aerospace Engineering The Wallace H.Coulter School of EngineeringClarkson University

The application of computational fluid dynamics/computational solid method(CFD/CSM)on solving the aero-thermo-elastic problem of spinning rocket is ***,the aerodynamic coefficients of a rocket are calculated,and the results are compared with the available experimental data,which verified the accuracy of the CFD ***,analysis is carried using ANSYS Workbench multi-physics coupling platform,which includes fluid,thermal,and structural *** results show that spinning causes a significant effect on the deformations and ***,thermal stresses due to high temperature at the rocket warhead and tail edges have a dominated effect,even more than those produced by aerodynamic ***,this important outcome should be taken into consideration during the rocket design stages.

关键词： ANSYS Workbench numerical calculation thermal stress spinning

在线全文

学校读者我要写书评

暂无评论

柔性火箭弹气动力计算精度预测

哈尔滨工业大学学报 2016年第10期48卷 91-96页

作者：李敏娇 laith k.abbas 芮筱亭王国平南京理工大学发射动力学研究所南京210094

为验证小变形小攻角下基于准定常和线性理论进行柔性火箭弹气动力计算的合理性,采用计算流体力学(CFD)方法预测了某火箭弹的升力及阻力系数,并在此基础上与经验公式相结合,获得该火箭弹沿轴向的单位长度升力和阻力系数导数分布.应用多... 详细信息

为验证小变形小攻角下基于准定常和线性理论进行柔性火箭弹气动力计算的合理性,采用计算流体力学(CFD)方法预测了某火箭弹的升力及阻力系数,并在此基础上与经验公式相结合,获得该火箭弹沿轴向的单位长度升力和阻力系数导数分布.应用多体系统传递矩阵法计算了该火箭弹的固有频率和振型,在准定常及线性理论的假设条件下,结合已得到的气动力系数导数,计算了基于火箭弹一阶振型的两个弯曲模型在不同攻角下的单位长度气动力系数分布.与CFD计算结果进行对比,发现该火箭弹在实际飞行条件下,该计算方法精度较好,在远超于实际的大变形时、攻角较大的情况下在头部和弹身处仍具有一定精度,但尾部误差较大,总体精度降低.

关键词：多体系统传递矩阵法柔性火箭弹振动特性 CFD 气动力

在线全文

学校读者我要写书评

暂无评论

流场环境对柔性立管湿模态的影响

哈尔滨工程大学学报 2017年第10期38卷 1587-1594页

作者：陈东阳 laith k.abbas 王国平芮筱亭南京理工大学发射动力学研究所江苏南京210094

为了研究静水压力和瞬态流场载荷对三维柔性立管湿模态的影响,本文基于声-固耦合模型对考虑水介质、顶张力情况下的立管进行湿模态计算,并与理论计算结果以及实验数据对比,验证了该模型的准确性;采用不考虑流-固耦合的计算流体力学(comp... 详细信息

为了研究静水压力和瞬态流场载荷对三维柔性立管湿模态的影响,本文基于声-固耦合模型对考虑水介质、顶张力情况下的立管进行湿模态计算,并与理论计算结果以及实验数据对比,验证了该模型的准确性;采用不考虑流-固耦合的计算流体力学(computational fluid dynamics,CFD)方法和考虑流固双向耦合的计算流体力学/计算结构力学(computational fluid dynamics/computational structure dynamics,CFD/CSD)方法分别计算了立管的瞬态流场载荷,并与实验数据对比;将水深产生的静水压力和瞬态流场载荷分别加载到三维柔性立管表面进行静力学分析,计算其湿模态。计算结果表明:立管湿模态频率比干模态频率小很多,且随着顶张力增大而增大;静水压力和瞬态流场载荷都使得湿模态频率略微增加;静水压力和瞬态流场载荷对湿模态低阶振型影响较大,对高阶振型几乎没有影响。

关键词：湿模态声-固耦合模型涡激振动顶张力柔性立管瞬态流场载荷湍流模型干模态

Non-linear Aerothermoelastic Modeling and Behavior of a Double-wedge Lifting Surface

在线全文

学校读者我要写书评

暂无评论

Journal of Shanghai Jiaotong university(Science) 2009年第5期14卷 620-625页

作者： laith k.abbas 芮筱亭 P.Marzocca Institute of Launch Dynamics School of Power EngineeringNanjing University of Sciences and Technology Clarkson University

The design of the re-entry space vehicles and high-speed aircraft structures requires special attention to the non-linear thermoelastic and aerodynamic *** thermal effects are important since temperature environment influences significantly the static and dynamic behaviors of flight structures in supersonic/hypersonic *** dynamic behavior of a double-wedge lifting surface with combined freeplay and cubic stiffening structural nonlinearities in both plunging and pitching degrees-of-freedom(DOF) operating in supersonic/hypersonic flight speed regimes has been *** addition a third order piston theory aerodynamics(PTA) is used to evaluate the non-linear unsteady aerodynamic loads applied to the wing *** of torsional stiffness that may be incurred by lifting surfaces subjected to axial stresses induced by aerodynamic heating is also *** aerodynamic heating effect is estimated based on the adiabatic wall temperature due to high speed *** is demonstrated that serious losses of torsional stiffness may occur in such lifting surfaces;the influence of various parameters such as flight condition,thickness ratio,freeplays and pitching stiffness nonlinearity are discussed.

关键词： non-linear aerothermoelastic analysis thermal loading freeplay hypersonic speed

在线全文

学校读者我要写书评

暂无评论

翼型非定常来流下复合运动动态失速仿真

哈尔滨工程大学学报 2019年第5期40卷 865-871页

作者：谢凯 laith k.abbas 陈东阳杨富锋芮筱亭南京理工大学发射动力学研究所江苏南京210094

针对直升机前飞时的动态失速问题,本文采用转捩修正的SST k-ω湍流模型和嵌套网格技术对雷诺数Re为3. 92×10~6时的直升机二维翼型SC1095进行数值仿真。以非定常来流条件下的纯俯仰运动为基础,对比分析了在耦合挥舞、摆振运动时,相位差... 详细信息

针对直升机前飞时的动态失速问题,本文采用转捩修正的SST k-ω湍流模型和嵌套网格技术对雷诺数Re为3. 92×10~6时的直升机二维翼型SC1095进行数值仿真。以非定常来流条件下的纯俯仰运动为基础,对比分析了在耦合挥舞、摆振运动时,相位差、振幅对动态失速的影响;比较挥舞、摆振二者运动对于动态失速角的作用大小。结果表明:固定振幅条件下,挥舞和摆振运动相位差的增加会使动态失速角提前,升力系数峰值提高;固定相位角条件下,挥舞和摆振运动振幅的增加会使动态失速角延迟,升力系数峰值减小。挥舞运动对于非定常来流下俯仰运动翼型动态失速角的影响要大于摆振运动。本文计算方法和研究结果为翼型多自由度耦合运动下的动态失速行为预测提供参考。

关键词：直升机旋翼翼型动态失速计算流体力学嵌套网格俯仰运动挥舞运动摆振运动

结构误差对旋转稳定弹丸气动特性影响的数值模拟

在线全文

学校读者我要写书评

暂无评论

空气动力学学报 2014年第5期32卷 705-711页

作者：陈东阳 laith k.abbas 芮筱亭王国平南京理工大学发射动力学研究所江苏南京210094

基于剪切应力传输(SST)k-ω湍流模型,对考虑结构误差情况下的弹箭模型进行数值模拟计算。首先采用CFD和工程经验公式相结合的方法,得到了不同马赫数、不同转速情况下无结构误差模型的多种气动特性参数。通过与实验数据对比,阻力、法向... 详细信息

基于剪切应力传输(SST)k-ω湍流模型,对考虑结构误差情况下的弹箭模型进行数值模拟计算。首先采用CFD和工程经验公式相结合的方法,得到了不同马赫数、不同转速情况下无结构误差模型的多种气动特性参数。通过与实验数据对比,阻力、法向力、俯仰力矩、压心位置误差在10%以内,验证了该方法的可行性和准确性。然后,建立了考虑结构误差即质量分布不对称、弹体不同轴和无结构误差模型,并分别进行了气动特性模拟计算。结果表明,质量偏心对滚转阻尼力矩系数、马格努斯力矩系数影响很大;弹体不同轴对法向力系数导数、俯仰力矩系数导数、马格努斯力矩系数导数和压心位置都产生很大影响。结构误差使模型的多种气动特性参数产生很大变化,将影响其飞行弹道和稳定性。

关键词：结构误差湍流模型计算流体力学旋转

在线全文

学校读者我要写书评

暂无评论

旋转弹箭气动导数与气动热仿真计算

计算机仿真 2014年第5期31卷 26-30页

作者：陈东阳 laith k.abbas 芮筱亭南京理工大学发射动力学研究所江苏南京210094

研究弹箭气动特性优化问题,基于剪切应力传输(SST)k-ω湍流模型,分别对M910弹丸和旋转弹模型F4进行数值仿真。计算采用CFD和工程经验公式相结合的方法,得到了光弹M910和翼身组合体F4在不同攻角,不同旋转速度,不同马赫数下的气动导数分... 详细信息

研究弹箭气动特性优化问题,基于剪切应力传输(SST)k-ω湍流模型,分别对M910弹丸和旋转弹模型F4进行数值仿真。计算采用CFD和工程经验公式相结合的方法,得到了光弹M910和翼身组合体F4在不同攻角,不同旋转速度,不同马赫数下的气动导数分布。通过与实验数据比较分析,阻力系数,法向力系数,俯仰力矩系数导数,滚转阻尼系数误差均在工程误差范围内,验证了本文计算方法的准确性。同时,数值仿真得到旋转弹体绝热壁面温度分布云图和不同旋转速度、不同攻角的弹箭迎风面中心线上温度分布数据图。计算分析为旋转弹箭气动热弹性仿真提供有价值参考。

关键词：数值仿真气动热气动导数旋转

Flow Regimes in Bubble Columns with and without Internals: A Review

在线全文

学校读者我要写书评

暂无评论

Fluid Dynamics & Materials Processing 2024年第2期20卷 239-256页

作者： Ayat N.Mahmood Amer A.Abdulrahman laith S.Sabri abbas J.Sultan Hasan Shakir Majdi Muthanna H.Al-Dahhan Department of Chemical Engineering University of Technology-IraqBaghdadIraq Chemical and Petroleum Industries Engineering Department Al-Mustaqbal University CollegeBabylonIraq Department of Chemical and Biochemical Engineering Missouri University of Science and TechnologyRollaUSA

Hydrodynamics characterization in terms ofﬂow regime behavior is a crucial task to enhance the design of bubble column reactors and scaling up related *** review presents recent studies on the typicalﬂow regimes established in bubble *** effort is also provided to introduce relevant deﬁnitions pertaining to thisﬁeld,namely,that of“void fraction”and related(local,chordal,cross-sectional and volumetric)*** studies involving different parameters that affect design and operating conditions are also discussed in *** the second part of the review,the attention is shifted to cases with internals of various types(perfo-rated plates,bafﬂes,vibrating helical springs,mixers,and heat exchanger tubes)immersed in the bubble *** is shown that the presence of these elements has a limited inﬂuence on the global column ***,they can make the homogeneousﬂow regime more stable in terms of transition gas velocity and transi-tion holdup *** last section is used to highlight gaps which have not beenﬁlled yet and future directions of investigation.

关键词： Hydrodynamics ﬂow regime bubble column heat-exchanging internals

Improved Manta Ray Foraging Optimizer-based SVM for Feature Selection Problems:A Medical Case Study

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

Journal of Bionic Engineering 2024年第1期21卷 409-425页

作者： Adel Got Djaafar Zouache Abdelouahab Moussaoui laith Abualigah Ahmed Alsayat Faculty of informatics University of Science and Technology Houari BoumedieneAlgiersAlgeria LRIA Laboratory University of Science and Technology Houari BoumedieneAlgiersAlgeria Computer Science Department University of Mohamed El Bachir El IbrahimiBordj Bou ArreridjAlgeria Computer Science Department University of Ferhat AbbasSetifAlgeria Computer Science Department Prince Hussein Bin Abdullah Faculty for Information TechnologyAl al-Bayt UniversityMafraq 25113Jordan Department of Computer Science College of Computer and Information SciencesJouf UniversityJoufSaudi Arabia Department of Electrical and Computer Engineering Lebanese American University13-5053ByblosLebanon Hourani Center for Applied Scientific Research Al-Ahliyya Amman UniversityAmman 19328Jordan MEU Research Unit Middle East UniversityAmman 11831Jordan Applied science research center Applied science private universityAmman 11931Jordan School of Computer Sciences Universiti Sains Malaysia11800 PenangMalaysia School of Engineering and Technology Sunway University Malaysia27500 Petaling JayaMalaysia

Support Vector Machine(SVM)has become one of the traditional machine learning algorithms the most used in prediction and classification ***,its behavior strongly depends on some parameters,making tuning these parameters a sensitive step to maintain a good *** the other hand,and as any other classifier,the performance of SVM is also affected by the input set of features used to build the learning model,which makes the selection of relevant features an important task not only to preserve a good classification accuracy but also to reduce the dimensionality of *** this paper,the MRFO+SVM algorithm is introduced by investigating the recent manta ray foraging optimizer to fine-tune the SVM parameters and identify the optimal feature subset *** proposed approach is validated and compared with four SVM-based algorithms over eight benchmarking ***,it is applied to a disease Covid-19 *** experimental results show the high ability of the proposed algorithm to find the appropriate SVM’s parameters,and its acceptable performance to deal with feature selection problem.

关键词： Support vector machine Parameters tuning Feature selection Bioinspired algorithms Manta ray foraging optimizer