共查询到19条相似文献,搜索用时 67 毫秒
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流动液体中的压力变化会引起气泡和气穴的产生及破灭,而气泡和气穴又会对液体的流动产生影响及压力变化.为了合理预测流控系统瞬态压力脉动过程中气泡和气穴的体积变化及其对脉动传播过程的影响,基于气泡溶解和析出的物理过程,建立了压力脉动过程中气泡和气穴产生及破灭的数学模型,并提出采用遗传算法对气泡模型中初始气泡体积、气体溶解和析出时间常数进行参数辨识.以一段液压油管路为研究对象,对管路中伴随气泡和气穴的瞬态压力脉动过程进行仿真及实验研究.利用仿真及实验结果,验证了采用遗传算法对气泡模型进行参数辨识的可行性.
关键词:
气泡
气穴
压力脉动
参数辨识 相似文献
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对于颗粒物质,在锥形通道的窄口处容易发生堵塞现象,实验中通常利用机械振动进行疏通.而对于无孔不入的水却不同,即使在纳米尺度的碳纳米管中仍然可以快速通透.本文利用分子动力学模拟研究了由锥形碳纳米管与石墨烯平面构成的无阀纳米泵,发现水输运在一定条件下也会出现反常堵塞.与颗粒物质截然不同的是振动方法无法恢复水流,相反,它促使水在纳米水泵的通道窄口处发生堵塞.通过分析堵塞区水的密度分布、氢键寿命、水分子的结构特征,揭示了反常堵塞是由腔体中振动膜的高频振动引发水的结构相变造成的. 相似文献
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实验分析研究了溴化锂溶液驱动的气泡泵。实验中保持12 mm管径、960W加热功率、1244 mm提升高度不变,改变溴化锂溶液浓度、浸没高度和添加剂质量分数来测试分析气泡泵性能。浸没高度为378~528 mm。溴化锂溶液浓度为45.5%~59.5%。选取异辛醇作为添加剂,添加的质量分数为(40~70)×10-6。实验结果表明,溴化锂溶液浓度对气泡泵的工作性能影响很大而异辛醇影响很小。 相似文献
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近壁微气泡溃灭特性的深入研究对靶向给药和基因治疗等技术具有较好的指导作用。该文基于数值模拟技术,采用有限体积法结合流体体积模型对超声作用下的近壁微气泡溃灭特性进行了研究,分析了超声对近壁微气泡溃灭动力学过程的影响。结果表明气泡溃灭最大射流速度与近壁距离无量纲参数γ在1.1~1.6范围内时成正比,与超声频率在10~60 Hz范围内时成正比,与气泡初始半径在50~100μm范围内时成反比;近壁气泡的二次溃灭最大射流速度大于一次溃灭,二次溃灭的作用更加明显。超声参数对近壁气泡溃灭过程存在较大影响,该研究为超声在医学上的应用提供了依据。 相似文献
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为了进一步提高能源利用效率和实现其空冷化,在双效溴化锂吸收式制冷系统中利用两级气泡泵代替溴化锂吸收制冷系统中传统的机械溶液泵。本文重点对两级溴化锂气泡泵的泵起时间及其影响因素做相关的实验研究,并得出以下的主要研究结果:1)对于不同的管径,两级气泡泵的泵起时间随着加热功率、浸没高度、工质浓度的变化趋势是基本一致的;2)加热功率越大越有利于气泡泵的泵起;3)随着浸没高度的增大气泡泵的泵起时间逐渐减小;4)工质浓度的增大也会使气泡泵的泵起时间增大,但当溴化锂溶液浓度大于54%后影响不明显;5)一级气泡泵的气液成分及中间溶液的闪发一定程度上影响两级气泡泵的泵起时间,因而造成局部区域与上述规律的偏离。 相似文献
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The aim of this paper is to investigate the dynamic characteristics of a valve-less micropump. A dynamic mathematical model of the micropump based on a hydraulic analogue system and a simulation method using AMESim software are developed. By using the finite-element analysis method, the static analysis of the diaphragm is carried out to obtain the maximum deflection and volumetric displacement. Dynamic characteristics of the valve-less micropump under different excitation voltages and frequencies are simulated and tested. Because of the discrepancy between simulation results and experimental data at frequencies other than the natural frequency, the revised model for the diaphragm maximum volumetric displacement is presented. Comparison between the simulation results based on the revised model and experimental data shows that the dynamic mathematical model based on the hydraulic analogue system is capable of predicting dynamic characteristics of the valve-less micropump at any excitation voltage and frequency. 相似文献
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强激光脉冲在水中的自聚焦传输、成丝、击穿及击穿后产生的声波,近年来成为强激光脉冲传输应用研究领域的一个热点。强激光脉冲电离产生的空泡在溃灭过程中,对周围水体产生压缩,从而在水下产生声波。在现有理论基础上,考虑空泡含气量、水的粘滞系数和水的表面张力系数对空泡运动及其产生声波的影响。给出双空泡运动方程,分析空泡间距对空泡溃灭和其产生声压关系。根据实际情况,计算不同温度情况下单空泡和双空泡运动过程及其产生的声压,并进行相互比较。计算结果表明: 水温越高,空泡运动时达到的最小半径越小,空泡振荡周期和溃灭时间延长,产生声压越高。随双空泡间距减小,空泡溃灭时达到的最小半径线性减小,而其产生的最大声压则单调增大。 相似文献
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This paper deals with the influence of gas law on ultrasonic behaviour of porous media when the saturating fluid is high pressured. Previous works have demonstrated that ultrasonic transmission through a porous sample with variations of the static pressure (up to 18 bars) of the saturating fluid allows the characterization of high damping materials. In these studies, the perfect gas law was used to link static pressure and density, which is disputable for high pressures. This paper compares the effects of real and perfect gas laws on modeled transmission coefficient for porous foams at these pressures. Direct simulations and a mechanical parameters estimation from minimization show that results are very similar in both cases. The real gas law is thus not necessary to describe the acoustic behaviour of porous media at low ultrasonic frequencies (100 kHz) up to 20 bars. 相似文献
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This paper investigates the pulsations and translation of bubbles in a double-bubble system driven by burst ultrasound. Results illustrate that for two identical bubbles, decreasing the frequency of burst or increasing its amplitude can enhance the pulsations and improve the translation velocities of bubbles. In a certain scope, large bubble brings about fast translation velocity, but the velocity will fall down for too large bubble, such as the bubble with ambient radius over about its resonance radius. When the ambient radii of two bubbles are different, translation of the large bubble is smaller than that of the small bubble. In addition, the effect of initial distance between bubbles is described as well. If burst serials are used, shortening the time interval between each burst and improving the acoustic amplitude of bursts are beneficial for the translations of bubbles. 相似文献
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Stable arrays of cylindrical bubbles with diameters 3 and 4 μm were produced by trapping air in the pores of hydrophobic Nuclepore filters. These bubble arrays were irradiated by beams of cw and pulsed ultrasound at carrier frequencies near the resonance frequencies of the trapped bubbles. By examining the frequency spectrum of the field scattered by the arrays it was found that the bubbles may oscillate as non-linear stable cavities of long duration. Using short pulses, the bubbles remain stable up to excitation pressure amplitudes of several bars. Mechanisms for the eventual growth and decay of the bubbles are discussed in light of the observations. 相似文献
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基于气泡边界层理论,引入黏性修正,采用边界积分法,考虑黏性效应和表面张力在单气泡以及双气泡耦合作用过程中的影响.首先将建立的数值模型与Rayleigh-Plesset的解析解进行对比,发现二者符合良好,验证了数值模型的有效性;在此基础上,建立考虑流体弱黏性效应的双气泡耦合模型,研究流体黏性和表面张力作用下,气泡表面变形、射流速度、流场能量转换等物理量的变化规律;最后研究雷诺数和韦伯数对于气泡脉动特性的影响规律.结果表明,流体黏性会抑制气泡脉动和气泡射流发展,降低气泡半径和射流速度;表面张力不改变气泡脉动幅值,但缩短了脉动周期,提升气泡势能. 相似文献
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The influence of a uniform driving force on tracer diffusion is investigated for a one-dimensional lattice gas where particles jump stochastically to unoccupied neighboring sites. A new, simple calculation is presented for the diffusion coefficient of a tracer particle with respect to its average drift, obtained recently by rigorous methods by De Masi and Ferrari. A theoretical expression describing the tracer particle mean square displacement approximately for all times is derived and found to be in excellent agreement with the results of Monte Carlo simulations. 相似文献