【作者】 徐良浩；

【导师】 彭晓星；

【作者基本信息】 中国舰船研究院 ， 流体力学， 2011， 硕士

【摘要】 已有研究表明,气核不仅是液体产生空化的必要条件,同时对空化发展也有显著的影响,因而掌握气核对空化的影响规律一直是空化研究的一项重要课题。为了研究气核对空化的影响,需要采用适当的测核手段来确定水中气核谱,但是目前气核如何对空化产生影响依然悬而未决,其中一个原因就是由于缺乏可以实时测量来流中气核的手段;同时根据已有的气核相似理论,在空泡水筒中播核通常用于减小模型空化试验的尺度效应,这时测核系统就成为有效地控制水筒中的气核的必要条件。本文通过调研已有的测核方法及其原理,在现有的PIV设备基础上,建立了一套激光干涉成像测核系统,该系统具有实时测量能力,并开发相应的图像处理软件。针对中国船舶科学研究中心新建空泡水筒中的播核系统,对该测核系统的应用进行了探索研究,目的就是希望为今后水筒中的气核控制提供基础。首先,从球形气泡的光散射特性出发,根据激光干涉成像测核的基本原理,分析了前向散射和侧向散射两种情况下气泡直径的计算公式。并在Matlab软件的基础上开发了相应的图像处理程序,重点解决气泡的提取和图像重叠的问题。然后,通过测量分析电解产生的气泡,对建立的激光干涉成像测核系统进行原理性试验,改变试验参数来研究各参数对试验结果的影响,主要分析了散射角、收集角和相机放大率等参数的影响。同时本文采用显微摄像法验证了激光干涉成像测核的有效性。最后,将激光干涉成像测核技术应用于过饱和水播核系统中,通过改变播核系统混合气体的压力和播核流量,对所产生的不同气核谱进行了测量,并对播核系统的播核能力进行了简单的计算,为今后该系统在水筒中的应用提供了技术基础。更多还原

【Abstract】 The existed cavitation researches have showed that the nuclei in the water are the fundamental condition for cavitation inception and also have remarkable influence on the process of cavitation. In order to know well about the relationship between nuclei and cavitation, some measurement methods have been used to determine the nuclei size and distribution. But up to now it is still an open problem about how the nuclei affect the cavitation. One of the reasons is lack of the effective way to measure the nuclei of incoming flow in cavitation facilities in real time. One other hand, seeding nuclei to the cavitation tunnel is often used to reduce the scale effects in the cavitation experiment. In this case nuclei measurement is also necessary technology to control the nuclei seeding in cavitation tunnel.In the present paper interferometric laser imaging system based on the PIV hardware equipments was set up to measure the nuclei distribution, and the image processing programs were developed to try to obtain the measurement results in real time. As the application this measurement was applied to the nuclei seeding system which is the key equipment for newly-built cavitation tunnel of CSSRC. The present work will provide a base to the nuclei control in the cavitation tunnel.Firstly, according to basic principle of interferometric laser imaging, some analysis was carried out to establish the formula of the bubble diameter in the front scattering field and side scattering field respectively. And then the image processing programs, which primarily include to pick up the bubble image and solve the problems of bubble overlap in a image, was developed to try to obtain the measurement results automatically in the Matlab environment.Secondly, some discussions were made about the influence of system parameters on the measurement, as the interferometric laser imaging technology was employed to measure the micro-bubbles generated by electrolysis. The factors include scattering angle, collecting angle and magnification etc.. The measurement results were also validated by microphotographics method in the same experimental conditions.Finally, the interferometric laser imaging technology was applied to the nuclei seeding system and measured nuclei spectrum under the different mixture pressure and seeding flux conditions. The capability of nuclei seeding system was deduced from the measurement results. The results can provide a technology fundament to the application of the interferometric laser imaging method and the nuclei seeding system on the cavitation tunnel.更多还原