To examine the similarities and differences in the evolution of cavity,wetting and dynamics of a highspeed,oblique water-entry projectile with different positive angles of attack,a comparative analysis has been conduc...To examine the similarities and differences in the evolution of cavity,wetting and dynamics of a highspeed,oblique water-entry projectile with different positive angles of attack,a comparative analysis has been conducted based on the numerical results of two mathematical models,the rigid-body model and fluid-structure interaction model.In addition,the applicable scope of the above two methods,and the structural response characteristics of the projectile have also been investigated.Our results demonstrate that:(1) The impact loads and angular motion of the projectile of the rigid-body method are more likely to exhibit periodic variations due to the periodic tail slap,its range of positive angles of attack is about α<2°.(2) When the projectile undergone significant wetting,a strong coupling effect is observed among wetting,structural deformation,and projectile motion.With the applied projectile shape,it is observed that,when the projectile bends,the final wetting position is that of Part B(cylinder of body).With the occu rrence of this phenomenon,the projectile ballistics beco me completely unstable.(3) The force exerted on the lower surface of the projectile induced by wetting is the primary reason of the destabilization of the projectile traj ectory and structu ral deformation failure.Bending deformation is most likely to appear at the junction of Part C(cone of body) and Part D(tail).The safe angles of attack of the projectile stability are found to be about α≤2°.展开更多
地下粮仓具有充分利用地下空间和抵抗外部干扰能力强等优点。为研究地下粮仓结构与土场相互作用的动力学特征,以装配式地下粮仓结构中钢桩为研究对象,利用非线性能量阱(nonlinear energy sink,NES)理论,将地下粮仓周围简化为非线性Wink...地下粮仓具有充分利用地下空间和抵抗外部干扰能力强等优点。为研究地下粮仓结构与土场相互作用的动力学特征,以装配式地下粮仓结构中钢桩为研究对象,利用非线性能量阱(nonlinear energy sink,NES)理论,将地下粮仓周围简化为非线性Winkler地基,钢桩简化为简支的Euler-Bernoulli梁。利用Hamilton原理,建立梁-土系统的运动方程;引入地基反力系数,描述土体的非线性刚度;利用增量谐波平衡法,求得运动方程的半解析解,并与数值解对比验证。与不考虑NES效应的结果对比,分析阻尼、质量比和地基反力系数等参数对结构在简谐激励下动力响应的影响,分析不同参数条件下土场对结构振动响应的抑制效果。研究表明:选取合理的阻尼、质量比和地基反力系数等参数时,弹性土体能在宽频带范围内减小结构稳态振动能量,显著降低结构共振能量峰和响应幅值;在经分析所得到的最优参数条件下,振动能量衰减率达99.39%。研究成果进一步阐释了土-结构相互作用效应的减振吸能作用,并为基于NES理论的地下粮仓减振设计提供了理论依据。展开更多
基金supported by the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX24_0714).
文摘To examine the similarities and differences in the evolution of cavity,wetting and dynamics of a highspeed,oblique water-entry projectile with different positive angles of attack,a comparative analysis has been conducted based on the numerical results of two mathematical models,the rigid-body model and fluid-structure interaction model.In addition,the applicable scope of the above two methods,and the structural response characteristics of the projectile have also been investigated.Our results demonstrate that:(1) The impact loads and angular motion of the projectile of the rigid-body method are more likely to exhibit periodic variations due to the periodic tail slap,its range of positive angles of attack is about α<2°.(2) When the projectile undergone significant wetting,a strong coupling effect is observed among wetting,structural deformation,and projectile motion.With the applied projectile shape,it is observed that,when the projectile bends,the final wetting position is that of Part B(cylinder of body).With the occu rrence of this phenomenon,the projectile ballistics beco me completely unstable.(3) The force exerted on the lower surface of the projectile induced by wetting is the primary reason of the destabilization of the projectile traj ectory and structu ral deformation failure.Bending deformation is most likely to appear at the junction of Part C(cone of body) and Part D(tail).The safe angles of attack of the projectile stability are found to be about α≤2°.
文摘地下粮仓具有充分利用地下空间和抵抗外部干扰能力强等优点。为研究地下粮仓结构与土场相互作用的动力学特征,以装配式地下粮仓结构中钢桩为研究对象,利用非线性能量阱(nonlinear energy sink,NES)理论,将地下粮仓周围简化为非线性Winkler地基,钢桩简化为简支的Euler-Bernoulli梁。利用Hamilton原理,建立梁-土系统的运动方程;引入地基反力系数,描述土体的非线性刚度;利用增量谐波平衡法,求得运动方程的半解析解,并与数值解对比验证。与不考虑NES效应的结果对比,分析阻尼、质量比和地基反力系数等参数对结构在简谐激励下动力响应的影响,分析不同参数条件下土场对结构振动响应的抑制效果。研究表明:选取合理的阻尼、质量比和地基反力系数等参数时,弹性土体能在宽频带范围内减小结构稳态振动能量,显著降低结构共振能量峰和响应幅值;在经分析所得到的最优参数条件下,振动能量衰减率达99.39%。研究成果进一步阐释了土-结构相互作用效应的减振吸能作用,并为基于NES理论的地下粮仓减振设计提供了理论依据。
