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为了扩展谐振管内非线性驻波在工程中的应用, 以及克服现有数值计算方法仅局限于求解直圆柱形和指数形谐振管内非线性驻波的问题. 根据变截面的非稳态可压缩热黏性流体Navier-Stokes方程和空间守恒方程, 并基于求解压力速度耦合方程的半隐式算法和交错网格技术, 构建一种能够计算任意形状轴对称谐振管受活塞驱动时内部非线性驻波的有限体积算法. 分别对圆柱形、指数形和圆锥形谐振管内的非线性驻波进行仿真计算. 通过与现有试验结果以及数值仿真结果的对比, 验证了该方法的正确性.并获得除驻波声压之外的另外一些新的物理结果, 包括速度、密度、温度的瞬时变化.在直圆柱形谐振管内产生冲击声压波, 速度波形中出现钉状结构.而在指数形和圆锥形谐振管内产生高声压幅值的驻波, 没有出现冲击波, 速度波形中均未发现钉状结构. 计算结果表明谐振管内非线性驻波的物理属性与谐振管形状之间有密切关系. 相似文献
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Manufacturing machines converting energy to mechanical work at the molecular level is a vital pathway to explore the microscopic world. A kind of operable molecular engines, composed of β‐cyclodextrin (β‐CD), aryl, alkene and amide moiety was investigated using molecular dynamics simulations combined with free‐energy calculations. To understand how the integrated alkene double bond controls the work performed on the engines, two alkene isomers of the prototype were considered as two molecular engines. The free‐energy profiles delineating the binding process of the amide (Z)‐ and (E)‐isomers for each alkene isomer with 1‐adamantanol indicate that for the alkene (E)‐isomer, the apparent work performed on the amide bond is 1.6 kcal/mol, while the alkene (Z)‐isomer is incapable to perform work. Direct switch on/off of engines caused by the isomerization of the alkene bond was, therefore, witnessed, in line with experimental measurements. Decomposition of the free‐energy profile into different components and structural analyses suggest that the isomerization of the alkene bond controls the position of the aryl unit relative to the cavity of the CD, resulting in the difference among the free‐energy profiles and the stark contrast of the work performed on engines. 相似文献
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