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不同槽宽分体箱梁可以有效地提高大跨度桥梁的气动稳定性,但是其涡振性能还不够明确,研究了6种代表性开槽率分体箱梁的涡振性能随开槽率的变化规律,对比了4种控制措施(增大阻尼比、可调风障、导流板和隔涡板)的制振效果,并对其进行了综合评价。结果表明:闭口箱梁的涡振性能要优于开槽的分体箱梁;随着开槽率的增大,分体箱梁的竖弯涡振振幅先增后减,扭转涡振振幅表现较为敏感,其中,60%开槽率的竖弯涡振和80%开槽率的扭转涡振振幅最大。对比了60%和20%开槽率分体箱梁,增大结构阻尼比和增设小透风率的隔涡板可以明显的减小不同槽宽分体箱梁的竖弯涡振振幅,增大阻尼比和增设水平风障可以有效地提高不同槽宽分体箱梁的扭转涡振性能,而增设内置、外置导流板对的涡振控制效果取决于开槽率的大小。以上4种控制措施都可以满足分体箱梁的扭转涡振振幅要求,但只有增设0%透风率的隔涡板才能满足Sperling指标和抗风设计规范的竖弯涡振振幅要求。 相似文献
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基于九叉树分割的曲面片上点的快速反解算法 总被引:1,自引:0,他引:1
本文针对曲面造型中,“由参数样条曲面上点的笛卡尔坐标,反求其对应参数”的反解问题,提出了一种通过曲面快速分割来逼近最终解的快速、简单、可靠的反解算法;并以B样条参数曲面为例,介绍了算法的实现过程。 相似文献
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George E. Klinzing Craig A. Myler Abdolreza Zaltash Shrikant Dhodapkar 《Particulate Science and Technology》1989,7(1):71-85
A new empirical correlation for the particle velocity which incorporates the angle of inclination is proposed here. This correlation coupled with the expression for the solids friction factor obtained from the force balance on the particle was used to predict the pressure drops in the 0.0266 m and 0.0504 m systems held at various angles of inclination. Particles used in these systems included glass particles of 67, 450, and 900 µm weight mean diameter. The existence of minimum points in the predicted pressure drop curves as a function of gas velocity was corroborated by these two expressions. 相似文献
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GEORGE E. KLINZING CRAIG A. MYLER ABDOLREZA ZALTASH SHRIKANT DHODAPKAR 《Particulate Science and Technology》2013,31(1-2):71-85
ABSTRACT A new empirical correlation for the particle velocity which incorporates the angle of inclination is proposed here. This correlation coupled with the expression for the solids friction factor obtained from the force balance on the particle was used to predict the pressure drops in the 0.0266 m and 0.0504 m systems held at various angles of inclination. Particles used in these systems included glass particles of 67, 450, and 900 µm weight mean diameter. The existence of minimum points in the predicted pressure drop curves as a function of gas velocity was corroborated by these two expressions. 相似文献
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该文推导了锚杆支护前后圆形隧洞的应力、位移和塑性区半径表达式。首先考虑静水压力状态下,岩石表现为弹脆塑性材料模型,采用Mohr-Coulomb线性屈服准则以及非关联流动法则,推导了无支护状态下圆形隧洞的弹塑性解析新解。在此基础上,通过均匀化方法,从宏观尺度将锚杆高密度支护模式下的岩石和锚杆复合体考虑成均匀连续、强度参数增强的等效材料,定义能够反映隧洞支护参数的锚杆密度因子,推导出等效弹性模量,等效粘聚力和等效内摩擦角的表达式,然后通过该文得到的隧洞在无支护状态下的解析解可以得到锚杆支护圆形隧洞解析解。最后将该文结果与前人研究结果及数值结果进行了比较分析,对比了锚杆支护前后圆形隧洞的塑性区半径、塑性区位移和塑性区应力,结果表明锚杆支护对隧洞的加固效果明显,该文结果可为地下工程中圆形隧洞的稳定性分析提供参考。 相似文献
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一类变质量振动系统的近似求解 总被引:3,自引:0,他引:3
当振动系统的参振质量随时间变化时,该系统即为变质量振动系统.采用改进的多尺度方法对变质量振动系统进行近似解析求解,并与四阶Runge-Kutta数值法进行比较,两种方法解得的振动响应一致.由计算结果可知,变质量振动系统的响应具有周期性;参振质量的时变方程中幅值变化系数ε的不同只影响系统振幅的大小,而不改变系统振动响应的周期.ε越大,系统响应的突变性越强;ε越小,振动响应越趋于平稳. 相似文献
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The formation of ash deposits may cause slagging and fouling problems in furnaces. The difficulties of predicting particle depositions are caused by the complexity of two-phase flow, which includes the particle size effects in a turbulent flow and the interparticle force between particles. Although some models were proposed to predict the particle deposition, few attempts were made for larger particles in the region of the dimensionless relaxation time (τ+) greater than 20. Thus, a reliable deposition model experimental results are needed for model verification, In this study, the modified turbulent intensity and apparent turbulent viscosity of the fluid were used to describe particles in suspension flow. And, an isothermal flow model was developed for calculating particle deposition rate in a parallel vertical plate, and for comparison with the experimental data. The predicted particle deposition rates under selected conditions are found to be in good qualitative agreement with available experimental results. 相似文献
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微波等离子体化学气相沉积(MWPCVD)是制备金刚石膜的一种重要方法.为了获得金刚石膜的高速率大面积沉积,研制成功了水冷反应室式MWPCVD制备金刚石膜的装置.装置在微波输入功率为3.0 kW时能长时间稳定运行,并在硅衬底上沉积出金刚石膜. 相似文献
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拉压弹性模量不同曲梁的弹性理论解 总被引:1,自引:0,他引:1
利用弹性理论研究了拉压弹性模量不同曲梁的平面应力及位移的问题,推导出了拉压弹性模量不同曲梁的应力及位移表达式。把该应力及位移表达式的计算结果与有限元法的计算结果进行了比较,验证了该拉压弹性模量不同曲梁的平面应力及位移公式的计算结果是可靠的。算例分析表明,对于拉压弹性模量不同曲梁的平面问题,不宜采用相同弹性模量弹性理论,而应该采用拉压弹性模量不同弹性理论。 相似文献
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不同拉压模量及软化特性材料的柱形孔扩张问题的统一解 总被引:9,自引:3,他引:6
对于具有不同的拉压模量及软化特性的岩土类材料,提出了不同拉压模量及软化特性的控制参数,采用双剪统一强度理论推导了柱形孔扩张问题的应力及位移的统一解。分析了模量、模型和软化等控制参数对柱形孔扩张时的扩张压力、塑性区开展规律及应力场的影响。结果表明:圆孔极限扩张压力、塑性区的发展规律、应力场、位移场等均随着模量控制参数、模型参数及软化参数的变化而变化,因此若采用经典的弹性理论、单一的模型参数及传统的不考虑应变软化来对岩土类的工程材料进行设计计算,必会带来较大的误差。 相似文献
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Conditions for the onset of particle breakup in normal shock waves have been investigated. A normalized particle drag behind the shock has been determined in terms of gas stagnation conditions and particle diameter for a range of gas Mach numbers 1 ≤ M1 ≤ 5 by introducing appropriately defined particle Knudsen and Reynolds numbers into analytical expressions for the drag coefficient. Numerical computations of the particle drag, normalized with gas stagnation pressure and particle area, indicate a peak at a gas Mach number M1 ≳ 2.2, The magnitude of the peak was found to decrease with increasing particle diameter and reservoir gas density.
Criteria for the onset of agglomerate breakup were defined in terms of a modified Weber number for the adhesion mechanisms due to Van der Waals forces, electrostatic attraction and adsorbed surface films. These results indicate that larger more closely packed agglomerates made up of smaller constituent particles have a greater tendency to resist breakup for a given set of stagnation conditions and shock Mach number. 相似文献
Criteria for the onset of agglomerate breakup were defined in terms of a modified Weber number for the adhesion mechanisms due to Van der Waals forces, electrostatic attraction and adsorbed surface films. These results indicate that larger more closely packed agglomerates made up of smaller constituent particles have a greater tendency to resist breakup for a given set of stagnation conditions and shock Mach number. 相似文献
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SALEM ABUZEID AHMED A. BUSNAINA GOODARZ AHMADI 《Particulate Science and Technology》2013,31(3-4):145-166
ABSTRACT Results comparing Eulerian and Lagrangian simulations of particle deposition from a point source in a channel are presented. The mean turbulent flow field is simulated using a two-equation k-? turbulence model. In the first, approach, diffusion of aerosol particles is studied by solving the corresponding advection-diffusion equation. Deposition of particles in the intermediate size range are analyzed by considering both the turbulent eddy diffusion and the eddy impaction processes, as well as the Brownian diffusion effects. In the second approach, the turbulence fluctuating velocity field are numerically simulated as a Gaussian random process. The Lagrangian trajectories of aerosol particles in the channel are then evaluated by solving the corresponding particle equation of motion. Effects of Brownian diffusion on particle motions are also included. A series of digital simulations for particles of various sizes which are released at different locations across the channel are carried out. Depositions of different size particles on the wall under a variety of conditions are analyzed. The relative significance of turbulence and Brownian effects are also discussed. 相似文献
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Salem Abuzeid Ahmed A. Busnaina Goodarz Ahmadi 《Particulate Science and Technology》1990,8(3):145-166
Results comparing Eulerian and Lagrangian simulations of particle deposition from a point source in a channel are presented. The mean turbulent flow field is simulated using a two-equation k-ε turbulence model. In the first, approach, diffusion of aerosol particles is studied by solving the corresponding advection-diffusion equation. Deposition of particles in the intermediate size range are analyzed by considering both the turbulent eddy diffusion and the eddy impaction processes, as well as the Brownian diffusion effects. In the second approach, the turbulence fluctuating velocity field are numerically simulated as a Gaussian random process. The Lagrangian trajectories of aerosol particles in the channel are then evaluated by solving the corresponding particle equation of motion. Effects of Brownian diffusion on particle motions are also included. A series of digital simulations for particles of various sizes which are released at different locations across the channel are carried out. Depositions of different size particles on the wall under a variety of conditions are analyzed. The relative significance of turbulence and Brownian effects are also discussed. 相似文献
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基于一种时域正演精细算法,引入Bregman距离函数作为Tikhonov函数的正则项,建立了求解多宗量一维瞬态非线性热传导反问题的数学模型,可对非线性内热源强度、导温系数和边界条件等多个热学参数进行组合识别。对信息测量误差作了初步探讨,数值验证给出令人满意的结果。 相似文献
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不同拉压模量及软化特性材料的球形孔扩张问题的统一解 总被引:5,自引:1,他引:4
对于具有不同的拉压模量及软化特性的岩土类材料,提出了不同拉压模量及软化特性的控制参数,采用双剪统一强度理论推导了球形孔扩张问题的应力及位移的统一解.分析了模量、模型和软化等控制参数对球形孔扩张时的扩张压力、塑性区开展规律及应力场的影响.结果表明:圆孔极限扩张压力,塑性区的发展规律,应力场,位移场等均随着模量控制参数、模型参数及软化参数的变化而变化,因此若采用经典的弹性理论、单一的模型参数及传统的不考虑应变软化来对岩土类的工程材料进行设计计算,必会带来较大的误差. 相似文献