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气泡上浮运动是舰船远程尾迹气泡场特征的重要组成部分。本文首先综合考虑水中气泡上浮与扩散传质这两个相互耦合的因素,构建了能够表征舰船远程尾迹场中气泡上浮运动的数学模型:进而利用该模型计算分析了远程尾迹气泡场气泡数密度的变化情况,计算值与实验结论吻合良好,表明了该模型的正确性与应用价值。 相似文献
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有限水域水中爆炸气泡脉动的数值模拟 总被引:1,自引:1,他引:0
《舰船科学技术》2015,(8):31-34
为研究炸药在有限水域内的气泡脉动规律,在Ansys AUTODYN程序内建立相应的计算模型,该模型考虑静水压力梯度和包括自由面、侧壁和水底在内的边界条件。以Pentolite炸药为例,计算其在Φ12 m×9.5 m爆炸水池内的水中爆炸过程,计算得到的气泡脉动周期与试验结果相吻合。基于该模型,可以计算炸药在有限水域中的气泡脉动过程,对于炸药水中爆炸气泡脉动研究具有参考价值。 相似文献
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柴油机活塞的低周热疲劳寿命预测与安全性评价 总被引:2,自引:0,他引:2
运用ADINAT和ADINA程序计算了12V180和42-160柴油机活塞的轴对称温度场和循环弹塑性应力应变场以及Mises当量应力应变场。根据“起动-停车”波形,采用带环状缺口的圆柱形试件,进行了热疲劳和高温低周疲劳模拟试验试验和计算表明:当量应变范围与疲劳寿命之间存在着Manson-Coffin公式关系,且不受试件结构形状和尺寸的影响; 相似文献
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水下航行体穿越水中膨胀气泡时,气泡在一定条件下有可能附着在航行体上形成附着空泡,从而改变航行体水动力性能,为此开展了头型因素对气团附着空泡影响的数值研究。利用数值模拟方法计算了四种头型航行体穿越膨胀气团的过程,结果发现头型是影响气泡附着的重要因素:对于分离角较大的钝头型,气泡容易附着在航行体上形成附着空泡;对于分离角较小的细长头型,气泡受到扰动后就很快与航行体分离而不会附着。 相似文献
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受试验场地条件限制,试验设计不得不采用多个几何缩比时,水下爆炸相似律将不再适用.本文从能量角度给出以水下爆炸动响应试验为目标的模型缩比设计换算律,能在一次试验过程中同时获取一次冲击波和气泡二次压力波冲击环境的测值. 相似文献
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水下爆炸试验相似准则 总被引:3,自引:1,他引:2
水下爆炸现象很复杂,根本不可能做到完全性的相似,哪怕做到一般船舶力学中的流体近似相似也相当困难.因此文献中有关水下爆炸相似律的描述就显得特别简单、笼统和模糊.文章首先对已经公认的一次冲击波的相似律作些解释,说明对一次冲击波的相似律也就是这些了,否则只能做原型试验,再对文献中没有出现过的气泡脉冲相似律的选择作了推导,最后将水下爆炸相似律拓广到与结构耦合上去. 相似文献
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气泡运动与舰船设备冲击振动关系的试验验证 总被引:11,自引:0,他引:11
由于水下爆炸和舰船动态响应的复杂性,对舰船水下爆炸动响应的认识的深刻程度主要来自试验现象和试验数据的分析.由于水下爆炸冲击波和二次压力波早已在水下爆炸试验测量中被发现,因此,在舰船和设备水下爆炸动响应的理论分析和计算过程中只将药包水下爆炸的冲击波作为主要外力,有时也考虑二次压力波的作用.也有人在研究中发现,气泡的运动有时对于舰船设备的运动是重要的.作者于1995年在浮动冲击平台水下爆炸试验中发现"水下爆炸气泡膨胀产生的滞后流是使安装频率为数十赫兹的舰船设备产生冲击振动的主要能源".近年来,发表的水下爆炸气泡运动的研究文献增多,但是,基本没有涉及气泡运动与舰船设备冲击振动的关系.在2003年的圆筒模型水下爆炸试验研究中,作者从另一种角度,用更加简明有力的证据,验证了上述结论.显然,这一发现不仅对于建立正确的理论计算力学模型有重要作用,甚至对于舰船防护的研究乃至水中兵器的研究都有着重要意义. 相似文献
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水下爆炸冲击波和气泡脉动的数值模拟研究 总被引:3,自引:0,他引:3
运用AUTODYN程序对水下爆炸冲击波和气泡脉动进行了数值模拟研究.首先模拟了无限水域中的水下爆炸冲击波,然后将深水爆炸简化为一维问题,采用一维方法对深水爆炸冲击波和气泡脉动进行了数值模拟,并将模拟结果与经验公式和实验结果进行了比较.模拟结果表明,AUTODYN能准确模拟近场水下爆炸冲击波和深水爆炸气泡脉动过程,计算得到的近场水下爆炸冲击波峰值压力和比冲量、水质点速度、气泡最大半径、脉动周期、二次压力波的峰值压力和比冲量等特性参数均与经验公式、理论公式和实验结果吻合良好.远场的冲击波峰值压力的计算值小于经验值,而且计算误差随着爆距的增加而增大.最后总结了模拟结果,得出了对工程应用有益的结论. 相似文献
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An experimental and computational investigation was conducted to evaluate the underwater blast response of fully submerged carbon fiber composite plates after prolonged exposure to saline water. The material was a biaxial carbon fiber/epoxy composite with a [±45°] fiber orientation layup. The plates were placed in a saline water bath with a temperature of 65 °C for 35 and 70 days, which simulates approximately 10 and 20 years of operating conditions in accordance to Fick's law of diffusion coupled with Arrhenius's Equation and a reference ocean temperature of 17 °C. Underwater blast experiments were performed in a 2.1 m diameter pressure vessel. The composite plates were placed in the center of the vessel while fully submerged in water, and an RP-85 explosive was detonated at a standoff distance of 102 mm from the center of the plate. Two cases of fluid hydrostatic gage pressures were investigated: 0 MPa, and 3.45 MPa. Two high speed cameras were utilized for three-dimensional Digital Image Correlation, which provided full-field displacements and velocities of the composite plates during underwater blast loading. A third high speed camera captured the behavior of the explosive gas bubble. Moreover, the pressure fields generated by the explosive detonation and resulting gas bubble were recorded with tourmaline pressure transducers. A water diffusion study was completed which showed that the diffusion of water into the composites reached a point of complete saturation after 35 days of exposure. Quasi-static material characterization tests were performed before and after prolonged exposure to saline water. The properties obtained from quasi-static testing also served as material inputs for the numerical models. The quasi-static test results showed that the tensile modulus E1,2 does not change with exposure to saline water, whereas the in-plane shear modulus G12 decreases with saline water exposure. During blast loading, for the case of 0 MPa hydrostatic gage pressure, the gas bubble interacts with the composite plate substantially. In such an event, the out of plane displacement increased for saline water exposed plates when compared to virgin structures. For the case of 3.45 MPa hydrostatic gage pressure, the gas bubble does not visibly interact with the composite plate. In this case, the out of plane displacement for specimens exposed to saline water was similar to the virgin specimen. A fully coupled Eulerian–Lagrangian fluid structure interaction simulation was performed by using the DYSMAS code. The numerical simulations showed that the displacement of fully submerged composite plates is driven by the displacement of fluid, as well as the size of the gas bubble formed by the explosive rather than the peak pressure generated by the explosive. The numerical simulations were in agreement with the experimental findings in terms of pressure history and plate deformation. 相似文献