共查询到20条相似文献,搜索用时 109 毫秒
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利用自主研发的CIP-ZJU(Constrained Interpolation Profile Method in Zhejiang University)高精度数学模型研究强非线性自由表面流动问题.模型在直角坐标系统下建立,采用紧致插值曲线CIP方法作为流场的基本求解器,通过多相流的方式实现固-液-气耦合同步求解,采用平衡格式的VOF(VOF/WLIC:Volume of Fluid/Weighted LineInterface Calculation)自由面捕捉方法改进了原模型,利用浸入边界方法处理运动物体.利用改进的CIP模型开展了不同类型的物体冲击液面引起的液滴飞溅现象的数值模拟,重点分析液滴飞溅过程中的自由液面变形、作用荷载和物体位置等.通过数值结果与实验结果的比较验证模型的可靠性.结果表明:平衡格式的VOF自由面捕捉方法能更精确地重构自由面,本文的数学模型可精确预测强非线性自由表面流动问题. 相似文献
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文献(1)介绍了打击水面产生水滴,井用水跃回法使这些水滴长期浮动在水面上的奇妙现象.该文中叙述的办法都是从外界产生水珠,溅落在水面上.笔者现在介绍一种液面自动产生液滴,并长期浮动在液面上的有趣现象.取一镍质增锅,倒入音容积的乙醇井点燃.一般乙醇火焰有20cm高,燃烧的火焰与液面之间有3cm高的乙醇蒸气层(图1所示).燃烧一分钟后,仔细观察液而,就会发现有大员的、极细小的液滴游动在液面上.细小的液滴不断地产生,通过碰担这些小浪滴合并成大的液滴,很快就会有几颗直径达Zmm的大液珠长成.这些大颗的液滴寿命很长,只… 相似文献
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高温熔融液滴的破碎特性研究 总被引:2,自引:0,他引:2
本文采用高速摄影和数字图像处理技术对高温熔融液滴与冷却水作用时的破碎现象进行了研究,用图像技术对高速摄影(1000 fps,512×512象素)照片进行处理,识别液滴破碎后所形成的碎片,并统计出碎片的数目及尺寸分布;还对液滴温度、冲击速度、水温等因素对液滴破碎过程的影响进行了实验研究和分析。研究结果表明,随着实验条件的改变,液滴破碎后的碎片有三种典型形态,冷却水温度对碎片形态有重要影响;碎片的当量直径符合累积高斯分布,分布曲线可用Sigmoid函数表示;冷却水温度越高,冲击高度越大,液滴温度越高,液滴的破碎过程进行得越彻底。 相似文献
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雨滴撞击索类结构表面可能会激发振动及表面积冰等问题,现有研究多关注于疏水壁面及液滴撞击壁面铺展、回缩特性,鲜见涉及雨滴冲击超疏水壁面压力特性的研究.为此,采用CLSVOF方法对单液滴冲击超疏水固壁面这一过程进行数值计算,分析了液滴速度、初始直径等因素对液滴冲击超疏水壁面的压力特性、液滴动态行为特性及液滴与壁面接触时间的影响.结果 表明:单液滴撞击超疏水壁面的过程中,接触瞬间在接触点附近产生局部高压区,而在液滴铺展过程中,对壁面几乎没有压力冲击;在回缩反弹阶段,壁面受到持续较长时间的压力波动,且压力波动区域不局限于初始接触点附近较小范围.撞击速度或液滴初始直径的增大使壁面受到的冲击更为剧烈,且初始速度对壁面受压的影响更为明显.一定范围内液滴初始直径的增大则会导致接触时间延长. 相似文献
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一、什么是不溶合现象或许你有喝咖啡的习惯,会偶而目睹一些有趣的事情.当咖啡滴入壶中的时候,咖啡液滴落到液面,在与大量咖啡液溶合之前,它可保持1秒钟左右不变.这种同种液体的两部分之间短暂的不溶合现象既不是分离现象也不是一种只能在漏滴型咖啡壶中才可观察到的现象.早在1879年瑞利就描述过类似的现象,1978年J.Walker称这种不溶合现象为科学的奇观.根据人们的日常经验,当同种液体的两部分接触时,会立即港合成单一的液体.如果两液滴起初被另一种与之不互溶的液体而非空气隔开,那么保持两个液滴状态的时间将延长,但是最终的结果仍是两个液滴溶合在一些. 相似文献
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A. A. Koroteev N. V. Bondareva Yu. A. Nagel N. I. Filatov I. V. Baidenko 《Thermophysics and Aeromechanics》2016,23(6):879-885
The regularities of interaction of drops of ultra-high vacuum liquid working media of space drop emitters with surfaces of trapping devices were considered. Their comparison with the characteristics of the interaction of drops of distilled water was performed. The achievability of trapping regimes without secondary drop formation in space was justified. 相似文献
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Antonio A. García Ana Egatz-Gómez Solitaire A. Lindsay P. Domínguez-García Sonia Melle Manuel Marquez Miguel A. Rubio S.T. Picraux Dongqing Yang P. Aella Mark A. Hayes Devens Gust Suchera Loyprasert Terannie Vazquez-Alvarez Joseph Wang 《Journal of magnetism and magnetic materials》2007
Magnetic fields can be used to control the movement of aqueous drops on non-patterned, silicon nanowire superhydrophobic surfaces. Drops of aqueous and biological fluids are controlled by introducing magnetizable carbonyl iron microparticles into the liquid. Key elements of operations such as movement, coalescence, and splitting of water and biological fluid drops, as well as electrochemical measurement of an analyte are demonstrated. Superhydrophobic surfaces were prepared using vapor–liquid–solid (VLS) growth systems followed by coating with a perfluorinated hydrocarbon molecule. Drops were made from aqueous and biological fluid suspensions with magnetizable microparticle concentrations ranging from 0.1 to 10 wt%. 相似文献
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环状出口气泡雾化喷嘴研究 总被引:3,自引:0,他引:3
本文对环状出口气泡雾化喷嘴出口下游液膜的破碎过程进行了研究,发现气体的介入是促使液膜破碎的主要原因。利用DUALPDA对其下游流场的速度分布、颗粒直径分布以及通量分布进行了实验测量。发现喷嘴出口附近主流区域存在大量具有负向速度的颗粒,并且此处的颗粒平均直径显著减小,为气泡雾化机理提供了佐证;在喷嘴出口下游轴心处液雾呈现逆向流动趋势,证明此处存在负压回流;沿轴向的速度分布曲线与颗粒直径分布曲线的变化趋势说明气泡"爆炸"发生在出口下游5-15 mm距离内。 相似文献
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We propose a novel approach to describe wetting of plane solid surfaces by liquid drops. A two-dimensional nonconserved phase field variable is employed to distinguish between wetted and nonwetted regions on the surface. The imbalance in the Young's force provides for the exchange of relative stability of the two phases. The three-phase contact line tension arises from the gradient energy and contact angle hysteresis from the kinetic coefficient. Using this theory, we discuss contact angle hysteresis on chemically heterogeneous surfaces. We show significant departure from the classical Cassie theory, which is attributed to defect pinning of the continuous triple line. 相似文献
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Xiufeng Yang Manjil Ray Song-Charng Kong Chol-Bum M. Kweon 《Proceedings of the Combustion Institute》2019,37(3):3279-3286
The interaction of liquid drops and heated surfaces is of great importance in many applications. This paper describes a numerical method, based on smoothed particle hydrodynamics (SPH), for simulating n-heptane drop impact on a heated surface. The SPH method uses numerical Lagrangian particles, which obey the laws of fluid dynamics, to describe the fluid flows. By incorporating the Peng–Robinson equation of state, the present SPH method can directly simulate both the liquid and vapor phases and the phase change process between them. The numerical method was validated by two experiments on drop impact on heated surfaces at low impact velocities. The numerical method was then used to predict drop-wall interactions at various temperatures and velocities. The model was able to predict the different outcomes, such as rebound, spread, splash, breakup, and the Leidenfrost phenomenon, consistent with the physical understanding. 相似文献
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Fernández-Nieves A Vitelli V Utada AS Link DR Márquez M Nelson DR Weitz DA 《Physical review letters》2007,99(15):157801
We use double-emulsion drops to experimentally investigate the defect structures of spherical shells of nematic liquid crystals. We uncover a rich scenario of coexisting defect structures dictated by the unavoidable finite thickness of even the thinnest shell and by the thickness variation around the sphere. These structures are characterized by a varying number of disclination lines and pairs of surface point defects on the inner and outer surfaces of the nematic shell. In the limit of very thick shells the defect structure ultimately merges with that of a bulk nematic liquid crystal drop. 相似文献
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This article describes work aimed at obtaining higher filmwise condensation heat flux by distributing dropwise condensation surfaces of optimal width promoted by an organic coating among filmwise surfaces, and to get higher mean overall heat transfer coefficients in condensing systems. Several different spacings were examined for the horizontal orientation, arranging a dropwise section above a filmwise one, to make clear the effect of the drops falling down to the filmwise section. The heat flux of the filmwise part increased with increasing the height of the dropwise part up to 2 mm, but then decreased above that. The extent of the filmwise part that was augmented by drops was also tested by changing the width of the filmwise section sandwiched between dropwise sections of constant width. The heat flux of the filmwise part increased abruptly at a width between 5 and 3 mm. Consequently, it was shown that there exists an optimum width for each section for enhancing condensation heat transfer in the filmwise sections. 相似文献
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