共查询到20条相似文献,搜索用时 114 毫秒
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本文在前人研究的基础上,计入浮力、表面张力、不同流体密度比等因素对弹性膜附近气泡运动的影响,结合不可压缩理想流体理论,建立气泡与弹性膜耦合动力学数值模型,采用边界元方法进行求解,计算值与Turangan等的实验结果符合良好.通过对弹性膜附近气泡运动的数值模拟,详细分析了弹性膜两侧为同种密度液体以及不同密度液体时气泡的运动,随后又分析气泡在弹性膜和浮力的共同作用下气泡的射流特性.旨在为相关气泡与弹性膜相互作用特性的研究提供参考.
关键词:
弹性膜
边界元法
气泡
浮力 相似文献
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采用体积加速度模型确定水下爆炸气泡运动的初始条件,基于MSC.DYTRAN有限元软件开发了定义流场初始条件和边界条件的子程序,对气泡在水平刚性壁面附近的运动特性进行了数值模拟,通过对比发现数值计算结果与实验结果具有较好的一致性,证明了初始条件定义、子程序开发和有限元模型建立的正确性和数值计算的准确性。以此为基础,研究了水深、泡心与刚性底面之间的距离对气泡动态特性和射流速度的影响,通过数值计算得到了一些有规律的曲线。计算模型、方法及结果对相关的工程研究和计算具有一定的参考价值。 相似文献
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《物理学报》2017,(5)
通过水洞实验对有水流速度影响的水下超声速气体射流进行实验研究,通过高速摄像系统记录射流形态演变过程,采用动态测力系统测量射流演变过程中射流周围环境压力的脉动特征.对剪切层涡旋结构进行分析,得到水流冲击射流的剪切涡流动形态演化和压力脉动特征.实验结果表明,射流主体形态的非定常运动依赖于水流速度,无水流速度时,射流主体受到重浮力影响向上弯曲较大,并且可以捕捉到射流的振荡诱导喷管口平面处主频为200 Hz的压力脉动,当存在水流速度时,射流主体向下游发展过程中的偏斜程度较小,射流与水流相互作用形成剪切涡,在水流作用下射流主体向下游发展过程中卷入射流剪切层,与射流主体掺混形成较大尺度的涡结构,喷管口平面处主频消失. 相似文献
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《工程热物理学报》2010,(9)
水下气体喷射形成了复杂气液流场,同时伴有频带宽、声压大的排气噪声产生。为研究水下排气流动状态与声压频谱之间的关系,建立水下排气噪声测试系统对水下排气形成的两相流场和排气噪声频谱进行了试验研究。结果表明随着排气速度的逐渐增大,排气形成的两相流场由气泡流态过渡为射流流态。伴随着流态的转换,气液边界面附近不稳定,形成大量体积较小气泡,这些小气泡在排气形成的湍流场激振作用下产生共振,从而辐射噪声;另一方面,这些气泡体积小,表面张力大,当多个气泡相互作用以及气泡形态发生变化时将释放出更高的能量,这些能量会辐射形成噪声;喷射流场的流态对水下排气噪声中频段声压峰值有较大的影响。当射流场由气泡流态过渡为射流流态后,2 kHz处对应的声压峰值呈非线性增大。 相似文献
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在势流假设下, 考虑表面张力以及黏性修正, 建立自由液面在气泡破碎后全非线性运动的数值模型, 给出射流断裂和水滴撕裂的数值处理方法. 同时进行上浮气泡在自由液面破裂的实验研究, 数值解与实验值符合良好.为了研究自由液面在气泡破碎后的运动学机理和规律, 运用开发的程序研究了不同尺寸气泡破碎后的动态特性, 包括从气泡底部顶起的射流、射流断裂以及水滴分裂等复杂的物理现象, 总结了从射流上撕裂出的第一个水滴尺寸、撕裂时间以及最大射流速度的变化规律. 最后讨论了雷诺数与韦伯数对气泡破碎后自由液面运动的影响.
关键词:
气泡
自由液面
破碎
断裂 相似文献
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YANG Bin GUO Hao-ran GUI Xin-yang LIU Xin WANG Zhi-xin CHEN Xiao-long LIU Pei-jin 《光谱学与光谱分析》2018,38(6):1958-1962
针对固体火箭发动机恶劣环境下的高温燃烧测量问题,提出了利用辐射光谱法来开展固体火箭推进剂燃烧温度在线测量的方法,采用200~1 100 nm光纤光谱仪测量了高压实验燃烧器下固体火箭推进剂燃烧火焰辐射光谱,总结了其光谱特性,并基于普朗克定律和光谱拟合方法获得了相应的推进剂燃烧温度,这对固体火箭推进剂燃烧诊断与燃烧机理研究具有重要的参考价值。 相似文献
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Suhyeon Oh Kyu Ho Van Ki Sung Jung Chun Sang Yoo Min Suk Cha Suk Ho Chung Jeong Park 《Proceedings of the Combustion Institute》2021,38(2):2049-2056
This study investigates the characteristics of oscillating lifted flames in laminar coflow-jets experimentally and numerically by varying both fuel density (by varying propane and n-butane mixtures) and coflow density (by diluting air with N2/He mixtures). Two different lifted flame oscillation behaviors are observed depending on these parameters: oscillating tribrachial lifted flame (OTLF) and oscillating mode-change lifted flame (OMLF), where a rapid increase in flame radius is observed. The regimes of the two flames are identified from experiments, which shows that OMLF occurs only when the effect of the negative buoyancy on the flow field by the fuel heavier than air becomes significant at low fuel jet velocity. OMLFs are also identified to distinguish OTLF regime from flame extinction, which implies that an OMLF can be extinguished when the positive buoyancy becomes weak, losing its stabilizing effect, or when the negative buoyancy becomes strong, further enhancing its destabilizing effect. Transient numerical simulations of both OTLF and OMLF reveal that the OMLF occurs by a strong toroidal vortex and a subsequent counterflow-like structure induced by relatively-strong negative buoyancy. Such a drastic flow redirection significantly changes the fuel concentration gradient such that the OMLF changes its mode from a tribrachial flame mode (decreasing edge speed with fuel concentration gradient) to the premixed flame-like transition mode when the fuel concentration gradient becomes very small (increasing edge speed with fuel concentration gradient). Again, a tribrachial flame mode is recovered during a rising period of flame edge and repeats an oscillation cycle. 相似文献
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流体体积法(VOF)可以便捷、高效地实现对多相流界面的捕捉和追踪。本文基于VOF方法,对单个空化泡在曲面固壁附近的运动进行了数值模拟,从实验对比、压力场、速度场、温度场演化、溃灭时间、射流速度、固壁温度等方面分析了空化泡溃灭过程的热动力学影响。结果表明,数值模拟得到的空化泡形态演化与实验观测到的现象一致,随着位置参数、泡内外压差及曲面固壁尺寸的改变,空化泡热动力学行为也将发生变化,受到流体运动及射流冲击的影响,溃灭瞬间产生的高温高压使得曲面固壁温度升高。本文研究的曲面固壁附近空化泡溃灭效应,揭示了空化泡与曲面固壁间的相互作用规律,对学术研究及工程应用都具有重要意义。 相似文献
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Kyu Ho Van Jeong Park Sung Hwan Yoon Suk Ho Chung Min Suk Cha 《Proceedings of the Combustion Institute》2019,37(2):1997-2004
The oscillating lifted flame in a laminar nonpremixed nitrogen-diluted fuel jet is known to be a result of buoyancy, though the detailed physical mechanism of the initiation has not yet been properly addressed. We designed a systematic experiment to test the hypothesis that the oscillation is driven by competition between the positive buoyancy of flame and the negative buoyancy of a fuel stream heavier than the ambient air. The positive buoyancy was examined with various flame temperatures by changing fuel mole fraction, and the negative buoyancy was investigated with various fuel densities. The density of the coflow was also varied within a certain range by adding either helium or carbon dioxide to air, to study how it affected the positive and negative buoyancies at the same time. As a result, we found that the range of oscillation was well-correlated with the positive and the negative buoyancies; the former stabilized the oscillation while the latter triggered instability and became a source of the oscillation. Further measurements of the flow fields and OH radicals evidenced the important role of the negative buoyancy on the oscillation, detailing a periodic variation in the unburned flow velocity that affected the displacement of the flame. 相似文献
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Rainbow schlieren deflectometry combined with high-speed digital imaging was used to study buoyancy effects on flow structure
of a helium jet discharged vertically into air. The experimental data were taken using the 2.2-sec drop tower facility at
the NASA John H. Glenn Research Center in Cleveland, Ohio. The test conditions pertained to jet Reynolds number of 490 and
jet Richardson number of 0.11, for which buoyancy is often considered unimportant. Experimental results show global oscillations
at a frequency of 27 Hz in Earth gravity. In microgravity, the jet oscillations vanished and the jet width increased. Results
provide a direct physical evidence of the importance of buoyancy on the flow structure of low-density gas jets at a Richardson
number considered too small to account for gravity. 相似文献
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The interactions of bubbles and coal particles in 600 kHz ultrasonic standing waves (USW) field has been investigated. A high-speed camera was employed to record the phenomena occurred under the USW treatment. The formation and behaviors of cavitation bubbles were analyzed. Under the driving of these cavitation bubbles, whose size is from several microns to dozens of microns, coal particles were aggregated and then attracted by large bubbles due to the acoustic radiation forces. The results of USW-assisted flotation show a significant improvement in recoveries at 600 kHz, which indicates that the interactions of bubbles and particles in the USW field are more efficient than that in the conventional gravitational field. Furthermore, the sound pressure distribution of the USW was measured and predicted by a hydrophone. The analysis of gravity and buoyancy, primary and secondary Bjerknes forces shows that bubble-laden particles can be attracted by the rising bubbles under large acoustic forces. This study highlights the potential for USW technology to achieve efficient bubble-particle interactions in flotation. 相似文献
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采用直接数值模拟的FTM(Front-Tracking Method)方法研究在重力作用下单气泡在竖直内置矩形肋管内的自由上升.选择矩形肋的肋高、肋距与方管宽度的比值作为管道几何特征值,用莫顿数作为流体特征参数,分析不同肋高、肋距及莫顿数情况下的气泡自由上升,研究不同几何特征及流体参数对气泡运动轨迹的影响.研究表明:在矩形肋片的影响下气泡上升时形状不对称,存在水平方向位移,表现为"蛇形"上升.这种现象与管道几何结构及气泡周围流体性质有关,肋高越大,现象越明显;气泡周围流体的粘度越小,水平方向位移越大. 相似文献
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采用格子Boltzmann方法(LBM)建立了气液固三相耦合的动力学模型,研究了相同尺度下上浮气泡与复杂壁面的相互耦合作用.首先,基于黏性流体理论,通过构建一组格子Boltzmann(LB)方程来描述气液两相的运动,并以LB离散体积力的形式计入了黏性力、表面张力和重力.同时,采用LBM中的Half-way反弹模型与有限差分格式相结合的方式进行固壁边界的处理.然后,利用本文建立的模型,对不同特征尺寸比条件下,气泡与考虑边缘效应的平面固壁和曲面固壁的耦合特性进行了研究.研究发现固壁边界条件以及特征尺寸比对气泡的运动和拓扑结构的变化都具有明显的非线性影响.最后,研究了流体属性对气泡与复杂壁面耦合规律的影响. 相似文献