共查询到20条相似文献,搜索用时 140 毫秒
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通过汽泡受力分析,构建窄缝通道内汽泡脱离直径预测模型。基于可视化实验获得的汽泡轴心倾斜角、前后接触角以及底部接触直径等数据,评价分析汽泡界面参数对脱离直径预测的影响,进而确定适用于本实验工况下窄缝通道内汽泡受力模型求解的界面输入参数,获得了窄缝通道汽泡脱离直径的预测值。利用竖直和倾斜条件下可视化实验获得的58个数据对汽泡脱离直径预测模型进行了验证,预测值和实验值符合较好。基于验证的汽泡脱离直径模型评估了各个力的地位和作用,应用分析了热工参数对汽泡脱离直径的影响。 相似文献
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在垂直上升环形通道内进行强制对流过冷沸腾实验。实验工质为水,实验压力为大气压力。由一台高速摄像仪对汽泡核化的动力学过程进行图像捕捉。通过影像获取总共58个工况下的汽泡脱离频率。对本实验的数据和从文献中获取的数据进行无量纲分析。将已有的模型和关系式与汽泡等待时间、生长时间以及脱离频率等实验数据进行比较。由池式沸腾改进的关系式未能很好地应用于强制对流过冷沸腾,同时,由过冷沸腾提出的模型也不能预测宽实验参数范围内的汽泡脱离频率。无量纲汽泡脱离频率与无量纲泡核沸腾热流密度相关。新的关系式与现有的低壁面过热度下的实验数据吻合良好。 相似文献
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《核动力工程》2016,(3):26-30
从微观角度深入探究汽泡的生长、聚合及传热规律,采用数值仿真的方法,建立相变物理模型。将建立的模型嵌入计算流体动力学(CFD)软件,利用流体体积函数(VOF)相界面追踪方法,对汽泡的生长、运动、聚合及脱离进行探究。设立1个尺寸为3 mm×2 mm×2 mm的三维微型通道,底部壁面设置5个单元,用于加热并对汽泡底部热流密度进行监测。获得微通道加热条件下汽泡的合并运动形态和底面热流密度分布,并与实验观测值比较。通过对汽泡形态的模拟和底部热流密度的监测,建立汽泡动力学规律与底面热流密度分布的关系,进一步深化对汽泡合并的动力学规律和沸腾传热机理的认识。 相似文献
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矩形窄流道内汽泡生长会直接改变相界面浓度,从而影响流道的传热传质性能。为获得适用于窄流道内不同类型的汽泡生长模型,基于通体可视的实验本体,开展壁面沸腾流动换热实验。基于传热能量方程,研究过冷沸腾中汽泡滑移与冷凝前期两种情况下汽泡生长模型。实验结果表明汽泡呈现两种形式的生长,即汽泡滑移生长以及冷凝前期生长。建立了两种情况下的汽泡生长模型,实验数据验证模型误差在20%以内。因此,本研究能为沸腾两相数值模拟提供更加精细化的汽泡生长模型,从而提高汽泡行为的预测精度。 相似文献
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《核技术(英文版)》2019,30(12)
Bubble formation is an integral part of the twophase flow science.Through numerical simulation and experiments using different air flow rates and orifice diameters,the present study aims at investigating the behavior of bubble formation and evolution from vertical wall orifice in quiescent pure water.For the experiments,the images of the bubble formation process under different working conditions were recorded using a high-speed camera and analyzed the entire process.The bubble formation process can be divided into three stages,namely nucleation,stable growth,and necking.According to the obtained results,bubble forms only when the air-phase pressure exceeds the threshold pressure at wall orifice.Due to the influence of the threshold pressure and buoyancy,the bubble volume decreases with an increase in the wall orifice diameter for the same flow rate.Moreover,the volume of fluid method is applied to simulate bubble formation in a three-dimensional model and the"buffer volume"is considered in the simulation model.The simulation resultsmatched well with the experimental data,which proves the existence of threshold pressure and the periodic pressure fluctuation at the wall orifice. 相似文献
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核电厂发生严重事故时可利用池洗效应去除泄漏的放射性气溶胶。对池洗过程进行两相数值模拟研究是有必要的,在使用两相计算流体力学(CFD)程序计算之前需要确定气泡注入点处的边界条件。基于整合池洗研究(IPRESCA)项目框架和流体体积法(VOF),对单个浸没孔气泡动力学特性进行数值模拟研究,捕捉浸没孔处气泡的大小、形状和脱离频率,并对气泡注入速度对气泡脱离频率的影响进行敏感性分析。利用DBSCAN聚类算法获得了气泡质心高度,并计算得到了不同高度的气泡上升速度。给出了平均空泡份额沿z轴方向的分布,以及平均空泡份额和平均混合速度在不同高度平面沿水平及径向的分布。 相似文献
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In severe accidents of a nuclear power plant, the released radioactive aerosols can be removed by pool scrubbing effect. Two-phase numerical simulation of the pool scrubbing process is necessary. The boundary conditions at the bubble injection point need to be determined before using the two-phase CFD program. Based on the framework of Integration of Pool scrubbing Research to Enhance Source-term Calculations (IPRESCA) project and the volume of fluid (VOF) method, a numerical simulation of gas injected bubble dynamics from single submerged orifice was carried out. Bubble size, shape, and detachment frequency at the orifice were captured. Sensitivity analysis of the influence of bubble injection speed on bubble detachment frequency was carried out. The bubble centroid height was obtained by DBSCAN clustering algorithm, and the bubble rising velocity at different heights was calculated. The distribution of the mean void fraction along the z-axis direction and the distribution of mean void fraction and mean mixture velocity along the horizontal lines and radius in central plane at different height are given. 相似文献
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基于扩散界面法,对单个氮气气泡在液态铅铋合金内从静止到充分发展整个过程中的动力学行为进行数值模拟,得到气泡形变特性和气泡上升速度随时间的变化关系,将模拟结果与Grace经验关系图对比,发现模拟得到的气泡形变结果在Grace经验关系图中均可找到且很好地吻合,从而验证了扩散界面法在模拟液态铅铋合金中气泡上升行为的可行性和准确性。同时基于界面扩散法的模拟,对比了5种不同初始直径的氮气泡在液态铅铋合金中的上升行为,发现初始直径较小的气泡在上升过程中扰动会更剧烈,初始直径较大的气泡在上升过程中易发生分裂现象。 相似文献
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Xiang Chai Xiaojing Liu Jinbiao Xiong Xu Cheng 《Journal of Nuclear Science and Technology》2016,53(11):1870-1880
Wake flow caused by the relative motions between bubble and liquid phase influences bubble motions and enhances turbulent properties in the liquid phase. This phenomenon has been stressed for a better understanding of bubbly flow. In this paper, large eddy simulation (LES) is performed to simulate a single bubble rising in the moving liquid, with volume of fluid (VOF) method to capture the interface movements between bubble and liquid phase. The simulation results are firstly compared with the numerical and experimental data from the literature. A good agreement demonstrated the capability of the employed computational fluid dynamics (CFD) approach to predict turbulent properties in the liquid phase and capture interface movement as well as its induced wake flow. Consequently, the dynamic behaviors of a single bubble rising in the moving liquid were investigated. An ensemble averaged has been employed to evaluate the velocity distribution composed by wake velocity and liquid velocity quantitatively as well as the velocity fluctuations enhanced by bubble motion. Their dependency was also evaluated based on a systematic CFD simulation which covers a wide range of liquid velocity. With comparisons of the single phase flow, the influence from the existence of bubble on turbulent properties was determined. 相似文献
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The single condensing bubble behavior in subcooled flow has been numerical investigated using the open source code OpenFOAM. A coupled Level Set (LS) and Volume of Fluid (VOF) method (CLSVOF) model with a phase change model for condensation was developed and implemented in the code. The simulated results were firstly compared with the experimental results, they were in great agreements, and thus the simulation model was validated. The validated numerical model was then used to analyze the condensing bubble deformation, bubble lifetime, bubble size history, condensate Nusselt number and other interesting parameters with different variables in subcooled flow. The numerical results indicated that the initial bubble size, subcooling of liquid and system pressure play an important role to influence the condensing bubble behaviors significantly and bubble will be pierced when the subcooling and initial diameter reach a certain value at the later condensing stage. The bubble diameter history and condensate Nusselt number were found in good agreement with the empirical correlation. The drag force coefficient was predicted well by introducing a reduced drag coefficient. 相似文献
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Chenguang YAN 《等离子体科学和技术》2022,24(4):44003
In this work, experimental and theoretical studies were carried out on arc-induced bubble dynamic behaviors in insulation oil. Direct experimental evidence indicated that the arc-induced bubble experiences pulsating growth rather than a continuous expansion. Furthermore, a theoretical model and numerical calculation method were proposed, which revealed the dynamic mechanism of bubble growth. Good agreement between the theoretical results and experimental observations verified the general correctness and feasibility of the proposed method. 相似文献
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棒束定位格架两相CFD模拟方法研究 总被引:1,自引:0,他引:1
考虑气泡合并分裂,采用MUSIG模型,对3×3格架内空气-水两相分布进行计算流体力学(CFD)数值模拟研究发现,计算对入口两相分布预计不敏感,但对气泡直径大小敏感;在定位格架下游不远处,空泡份额分布由较小直径气泡起主导作用,格架下游较远处,空泡份额分布由较大直径气泡起主导作用。考虑空气-水两相流量、几何条件和压力对气泡直径的影响,本文提出针对棒束定位格架的数值模拟气泡最大直径设置关系式,并对模型选取和模拟方法给出建议。计算表明空泡份额分布曲线形状与峰值均和实验符合较好,该模拟方法能合理预测复杂通道两相数值分布。 相似文献